0000950170-24-026249 | 10-K | XBRL Viewer

Print Document View Excel Document

Consolidated Financial Statement Details - Schedule of Other Current Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Other current assets	$ 9,779	$ 15,808
Prepaid research and development expenses
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Other current assets	4,325	7,398
Non-trade receivables and other
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Other current assets	1,047	2,423
Other prepaid expenses
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Other current assets	$ 4,407	$ 5,987

Income Taxes - Schedule of Income (Loss) Before Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Domestic	$ (274,998)	$ (371,900)	$ (524,440)
Foreign	(1,258)	6,917	1,160
Loss before provision for income taxes	$ (276,256)	$ (364,983)	$ (523,280)

- Definition

Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(11))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483586/944-220-S99-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-22

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 30
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-30

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-32

Reference 5: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 31
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-31

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-32

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 235
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-05(b)(2))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479557/942-235-S99-1

Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 25
-Paragraph 1
-SubTopic 20
-Topic 940
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481913/940-20-25-1

Reference 9: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(10))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483621/220-10-S99-2

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 942
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(15))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483589/942-220-S99-1

+ Details

CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Statement of Comprehensive Income [Abstract]
Net loss	$ (276,056)	$ (368,198)	$ (523,837)
Other comprehensive income (loss):
Net unrealized gain (loss) on available-for-sale investments	1,826	(1,114)	(1,568)
Net foreign currency translation adjustment	5,161	(1,636)	(294)
Other comprehensive income (loss)	6,987	(2,750)	(1,862)
Comprehensive loss	$ (269,069)	$ (370,948)	$ (525,699)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(g)(1)(ii))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 323
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481687/323-10-50-3

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 28
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482907/825-10-50-28

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482765/220-10-50-6

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483443/250-10-50-3

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483443/250-10-50-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 65
-Paragraph 1
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480175/815-40-65-1

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 8
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483443/250-10-50-8

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483443/250-10-50-9

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483443/250-10-50-11

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483443/250-10-50-11

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483443/250-10-50-4

Reference 13: http://www.xbrl.org/2003/role/exampleRef
-Topic 946
-SubTopic 830
-Name Accounting Standards Codification
-Section 55
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480167/946-830-55-10

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section 45
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483581/946-220-45-7

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(18))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483586/944-220-S99-1

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-22

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(9))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483575/946-220-S99-1

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.6-09(1)(d))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483575/946-220-S99-3

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(i))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480097/470-10-S99-1A

Reference 20: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(ii))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480097/470-10-S99-1A

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iii)(A))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480097/470-10-S99-1A

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iv))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480097/470-10-S99-1A

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(5))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480097/470-10-S99-1A

Reference 24: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(i))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480097/470-10-S99-1B

Reference 25: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iii)(A))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480097/470-10-S99-1B

Reference 26: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iii)(B))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480097/470-10-S99-1B

Reference 27: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iv))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480097/470-10-S99-1B

Reference 28: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(5))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480097/470-10-S99-1B

Reference 29: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 30
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-30

Reference 30: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-32

Reference 31: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 60B
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482689/260-10-45-60B

Reference 32: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 31
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-31

Reference 33: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-32

Reference 34: http://www.xbrl.org/2003/role/disclosureRef
-Topic 205
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483499/205-20-50-7

Reference 35: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 28
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482740/230-10-45-28

Reference 36: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1A
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482790/220-10-45-1A

Reference 37: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1B
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482790/220-10-45-1B

Reference 38: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(20))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483621/220-10-S99-2

Reference 39: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 942
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(22))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483589/942-220-S99-1

+ Details

- Definition

Amount after tax and reclassification adjustments of other comprehensive income (loss).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-SubTopic 10
-Topic 505
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 830
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481674/830-30-50-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 830
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 17
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481694/830-30-45-17

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(19))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483586/944-220-S99-1

Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482765/220-10-50-4

Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482765/220-10-50-5

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 830
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 20
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481694/830-30-45-20

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(21))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483621/220-10-S99-2

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(23))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483589/942-220-S99-1

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1B
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482790/220-10-45-1B

Reference 11: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 55
-Paragraph 15
-SubTopic 10
-Topic 220
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482739/220-10-55-15

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1A
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482790/220-10-45-1A

+ Details

License and Collaboration Agreements

12 Months Ended

Dec. 31, 2023

License And Collaboration Agreements [Abstract]

License and Collaboration Agreements

Note 7 — License and Collaboration Agreements

We have entered into various collaboration agreements including license agreements and collaborative research, development and commercialization agreements with various pharmaceutical and biotechnology companies. Under these collaboration arrangements, we are entitled to receive license fees, upfront payments, milestone and other contingent payments, royalties, sales milestone payments, and payments for the manufacture and supply of our proprietary PEGylation materials and/or reimbursement for research and development activities. We generally include our costs of performing these services in research and development expense, except for costs for product sales to our collaboration partners which we include in cost of goods sold. We analyze our agreements to determine whether we should account for the agreements within the scope of ASC 808 Collaborative Arrangements, and, if so, we analyze whether we should account for any elements under ASC 606 Revenue from Contracts with Customers.

Eli Lilly and Company (Lilly): Rezpegaldesleukin (previously referred to as NKTR-358)

On July 23, 2017, we entered into a worldwide license agreement (the Lilly Agreement) with Eli Lilly and Company (Lilly) to co-develop rezpegaldesleukin, a novel immunological drug candidate that we invented, pursuant to which we received an initial payment of $150.0 million and were eligible for up to $250.0 million in additional development and regulatory milestones. The Lilly Agreement provided that, during Phase 1b and Phase 2 development, we shared development costs wherein 75% of the costs were borne by Lilly and 25% of the costs were borne by us.

On February 23, 2023, we announced the topline data from the Phase 2 study (Phase 2 Lupus Study) of rezpegaldesleukin in adult patients with systemic lupus erythematosus (SLE). Although the Phase 2 Lupus Study did not meet its primary endpoint, patients who received the middle dose within the modified intent-to-treat population, defined as all patients who were randomized and received at least one dose of rezpegaldesleukin, demonstrated improvement in SLEDAI-2K score as compared to placebo. Nonetheless, Lilly notified us that it does not intend to advance rezpegaldesleukin into Phase 3 development for SLE.

On April 23, 2023, we received from Lilly a notice of at-will termination of the Lilly Agreement. On April 27, 2023, we announced that we would regain full rights to rezpegaldesleukin from Lilly, and the Lilly Agreement subsequently terminated. Following the return of our rights to develop rezpegaldesleukin, we bear all costs of development. We have initiated a Phase 2b study of rezpegaldesleukin in patients with moderate-to-severe atopic dermatitis, and we are targeting the initiation of a Phase 2b study of rezpegaldesleukin in patients with alopecia areata by the end of March 2024. We also plan to explore other auto-immune indications for the development of rezpegaldesleukin.

On August 7, 2023, we announced that the interim efficacy data previously generated by Lilly for rezpegaldesleukin that were presented at the EADV conference in September 2022 were incorrectly calculated by Lilly. The erroneous interim data were reported in connection with the Phase 1b study of rezpegaldesleukin in adult patients with atopic dermatitis (Phase 1b AD Study) and the Phase 1b study of rezpegaldesleukin in adult patients with psoriasis. We reported the new and corrected data from the Phase 1b AD and psoriasis studies of rezpegaldesleukin.

On October 13, 2023, we announced final efficacy data from the Phase 1b AD Study at the 2023 EADV conference. The final data from the study demonstrated rezpegaldesleukin resulted in dose-dependent improvements in eczema area and severity index (EASI), validated investigated global assessment (vIGA), body surface area (BSA), and itch numeric rating scale (NRS) over twelve weeks of treatment compared to placebo, which were sustained post-treatment over an additional thirty-six weeks.

Bristol-Myers Squibb (BMS): Bempegaldesleukin (previously referred to as NKTR-214)

Effective April 3, 2018, we entered into a Strategic Collaboration Agreement (the BMS Collaboration Agreement) and a Share Purchase Agreement with BMS. Pursuant to the BMS Collaboration Agreement, we and BMS jointly developed bempegaldesleukin in combination with BMS’ Opdivo®. The parties share the internal and external development costs for bempegaldesleukin in combination regimens based on each party’s relative ownership interest in the compounds included in the regimens. In accordance with the agreement, the parties share development costs for bempegaldesleukin in combination with Opdivo®, 67.5% of costs to BMS and 32.5% to Nektar. The parties also shared costs for the manufacturing and pre-commercial costs of bempegaldesleukin, 35% of the costs to BMS and 65% to Nektar.

Upon the effective date of the BMS Collaboration Agreement in April 2018, BMS paid us a non-refundable upfront cash payment of $1.0 billion and purchased 8,284,600 shares of our common stock pursuant to the Share Purchase Agreement for total additional cash consideration of $850.0 million. In 2020, we received additional non-refundable milestone payments of $50.0 million.

As discussed in Note 1, in April 2022, we announced that BMS and we decided to discontinue all development of bempegaldesleukin in combination with Opdivo®. On September 6, 2023, BMS and we terminated the BMS Collaboration Agreement, and pursuant to the surviving provisions of the BMS Collaboration Agreement, we and BMS continue our efforts to wind down the bempegaldesleukin program, and the cost sharing provisions continue to remain in effect as the parties wind down the studies. On February 12, 2024, we repurchased the 8.3 million shares previously sold to BMS for total cash consideration of $3.0 million.

We determined that the BMS Collaboration Agreement falls within the scope of ASC 808. Based on the cost sharing percentages described above, we recognized BMS’ reimbursement of our expenses as a reduction of research and development expense and our reimbursement of BMS’ expenses as research and development expense. As discussed in Note 8, beginning in the second quarter of 2022, we began reporting clinical trial, other third-party costs and employee costs for the wind down of the bempegaldesleukin program in restructuring, impairment and costs of terminated program.

Accordingly, during the year ended December 31, 2022, we recorded $45.7 million for the net reimbursement from BMS, of which we recorded $24.9 million as a reduction of research and development expense for the first quarter of 2022, and $20.8 million as a reduction of restructuring, impairment and costs of terminated program for the remaining three quarters of 2022. During the year ended December 31, 2021, we recorded $101.5 million as a reduction of research and development expense for the net reimbursement from BMS. The net reimbursement payable to BMS for the year ended December 31, 2023 was not significant.

SFJ Pharmaceuticals

On February 12, 2021, we entered into a Co-Development Agreement (the SFJ Agreement) with SFJ Pharmaceuticals XII, L.P., a SFJ Pharmaceuticals Group company (SFJ), pursuant to which SFJ would pay up to $150.0 million to support a Phase 2/3 study of bempegaldesleukin in combination with Keytruda® (pembrolizumab) in metastatic or unresectable recurrent squamous cell carcinoma of the head and neck (the SCCHN Clinical Trial). SFJ had primary responsibility for the clinical trial management of the SCCHN Clinical Trial, and we were the sponsor of the SCCHN Clinical Trial. The SFJ Agreement provided for us to pay up to $637.5 million in Success Payments in the event of FDA approval of bempegaldesleukin in up to three indications.

We accounted for the SFJ Agreement as a derivative liability, which we remeasured to fair value at each reporting date. We recorded increases to the liability for non-cash research and development expense as SFJ conducted the SCCHN Clinical Trial and for cash receipts from SFJ to us to support our internal costs of conducting the trial. We presented the gain (loss) from the remeasurement as change in fair value of development derivative liability in our Consolidated Statements of Operations.

At March 31, 2022, due to the negative results of the metastatic melanoma trial and initial discussions with SFJ, we concluded that it was remote that SFJ and we would continue the SCCHN Clinical Trial. Accordingly, the fair value of the development derivative liability was reduced to zero as of March 31, 2022, and we recognized a corresponding gain in change in fair value of development derivative liability. In April 2022, we announced that SFJ and we agreed to discontinue the SCCHN Clinical Trial. Accordingly, SFJ will not be entitled to any Success Payments, and SFJ has the responsibility to wind down the SCCHN Clinical Trial at its sole cost. SFJ has no right to seek reimbursement from us for any costs incurred for the SCCHN Clinical Trial.

The following table presents the change in the derivative liability for the years ended December 31, 2022 and 2021:


		Year Ended December 31,
	Fair Value Hierarchy Level	2022			2021
Fair value as of December 31, 2021 and February 12, 2021 (inception), respectively	3	$	27,726		$	—
Non-cash research and development expense			4,951			16,703
Cash receipts from SFJ			750			3,000
Change in the fair value of development derivative liability			(33,427	)		8,023
Fair value at end of period	3	$	—		$	27,726

Other

We have other collaboration agreements that have resulted in commercialized products for our collaborations partners. Under these agreements, we may sell our proprietary PEGylation materials for use in these products, and we are entitled to receive royalties based on net sales of these products as well as sales milestones. Additionally, we have a collaboration agreement for a product under development, under which we are entitled to up to a total of $40.0 million of regulatory milestones, as well as royalties based on net sales, if approved, and sales milestones upon achievement of an annual net sales targets. However, given the current phase of development of the product under this collaboration agreement, we cannot estimate the probability or timing of achieving these milestones, and, therefore, have excluded all development milestones from the transaction price for this agreement.

Segment Reporting (Tables)

12 Months Ended

Dec. 31, 2023

Segment Reporting [Abstract]

Schedule of Revenue by Geographic Area

Revenue by geographic area is based on the headquarters or shipping locations of our partners. The following table sets forth revenue by geographic area (in thousands):


	Year Ended December 31,
	2023		2022		2021
United States	$	11,481	$	9,841	$	10,114
Rest of World		78,641		82,214		91,793
Total revenue	$	90,122	$	92,055	$	101,907

Restructuring, Impairment and Costs of Terminated Program - Summary of Restructuring Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Restructuring Cost and Reserve [Line Items]
Clinical trial expense, other third-party and employee costs for the wind down of the bempegaldesleukin program	$ 5,492
Severance and benefit expense	7,885
Impairment of right-of-use assets and property, plant and equipment	35,328	$ 65,761	$ 0
Loss (gain) on sale or disposal of other property, plant and equipment, net	1,300	(3,326)	0
Contract termination and other restructuring costs	1,953
Restructuring, impairment and costs of terminated program	51,958	135,930	$ 0
2022 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Clinical trial expense, other third-party and employee costs for the wind down of the bempegaldesleukin program	5,492	31,693
Severance and benefit expense		30,904
Impairment of right-of-use assets and property, plant and equipment	14,728	65,761
Loss (gain) on sale or disposal of other property, plant and equipment, net	0	(3,326)
Contract termination and other restructuring costs	1,919	10,898
Restructuring, impairment and costs of terminated program	22,139	$ 135,930
2023 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Clinical trial expense, other third-party and employee costs for the wind down of the bempegaldesleukin program	0
Severance and benefit expense	7,885
Impairment of right-of-use assets and property, plant and equipment	20,600
Loss (gain) on sale or disposal of other property, plant and equipment, net	1,300
Contract termination and other restructuring costs	34
Restructuring, impairment and costs of terminated program	$ 29,819

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References + Details

Operating Leases - Additional Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($) ft² Option	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Leases [Line Items]
Impairment of right-of-use assets and property, plant and equipment		$ 65,761
Operating lease, payments	$ 21,000	20,100	$ 16,800
Weighted average remaining lease term	6 years 1 month 6 days
Weighted average discount rate, percent	5.80%
Subleases aggregate lease payments	$ 10,500
General and Administrative Expense
Leases [Line Items]
Total sublease income	2,200
Sublease Property, Plant And Equipment
Leases [Line Items]
Impairment of right-of-use assets and property, plant and equipment	$ 30,600	$ 11,171
Mission Bay Facility
Leases [Line Items]
Lease space (in sq ft) \| ft²	155,215
Subleases space (in sq ft) \| ft²	29,000
Number of renewal options \| Option	2
Renewal term (in years)	5 years
Third Street Facility
Leases [Line Items]
Lease space (in sq ft) \| ft²	135,936
Number of renewal options \| Option	1
Renewal term (in years)	5 years

Liabilities Related to the Sales of Future Royalties - Additional Information (Details) $ in Thousands				3 Months Ended	12 Months Ended
	Mar. 01, 2024 USD ($)	Dec. 16, 2020 USD ($)	Feb. 24, 2012 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Liability Related to the Sale of Future Royalties [Line Items]
Non-cash loss on revaluation of liability related to the sale of future royalties					$ 0	$ 0	$ 24,410
2012 Purchase and Sale Agreement
Liability Related to the Sale of Future Royalties [Line Items]
Proceeds from sale of royalty rights			$ 124,000
2012 Purchase and Sale Agreement \| Future Royalties
Liability Related to the Sale of Future Royalties [Line Items]
Fair value of liabilities					$ 84,700
Non-cash loss on revaluation of liability related to the sale of future royalties				$ 23,500
Transaction costs related to revised royalty payments				$ 900
2020 Purchase and Sale Agreement
Liability Related to the Sale of Future Royalties [Line Items]
Proceeds from sale of royalty rights		$ 150,000
Payment of transaction related to purchase and sale agreement		210,000
Payment of transaction related to purchase and sale agreement if threshold is not achieved		$ 240,000
2020 Purchase and Sale Agreement \| Subsequent Event
Liability Related to the Sale of Future Royalties [Line Items]
Amount exchanged to remove cap on royalties	$ 15,000
2020 Purchase and Sale Agreement \| Measurement Input, Discount Rate
Liability Related to the Sale of Future Royalties [Line Items]
Royalties liability, measurement input					0.17
2020 Purchase and Sale Agreement \| Measurement Input, Interest Rate
Liability Related to the Sale of Future Royalties [Line Items]
Royalties liability, measurement input					0.30
Pursuant to the 2012 Purchase and Sale Agreement
Liability Related to the Sale of Future Royalties [Line Items]
Payment made for milestone not achieved year one						$ 10,000
Payment made for milestone not achieved year two					$ 10,000

License and Collaboration Agreements - Additional Information (Details) - USD ($)					1 Months Ended	3 Months Ended	9 Months Ended	12 Months Ended
	Feb. 12, 2024	Feb. 12, 2021	Apr. 03, 2018	Jul. 23, 2017	Apr. 30, 2018	Mar. 31, 2022	Dec. 31, 2022	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2023	Dec. 31, 2020
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Derivative liability						$ 0
SFJ
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Committed funding (up to)		$ 150,000,000
Success payments (up to)		$ 637,500,000
Bristol-Myers Squibb Company \| Purchase Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Shares issued (in shares)					8,284,600
Sale of stock consideration received					$ 850,000,000
Bristol-Myers Squibb Company \| Nektar 214
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Reimbursement of expenses							$ 20,800,000	$ 20,800,000
Bristol-Myers Squibb Company \| Nektar 214 \| Research and Development Expense
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Reimbursement of expenses						$ 24,900,000		$ 45,700,000	$ 101,500,000
Other Partner
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential future additional payments for development milestones										$ 40,000,000
Subsequent Event \| Bristol-Myers Squibb Company
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Sale of stock shares repurchased	8,300,000
Sale of stock repurchased cash consideration	$ 3,000,000
Nektar-358 \| Eli Lilly
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of sharing in Phase 2 development costs				75.00%
Nektar-358 \| Maximum \| Eli Lilly And Company
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential future additional development and regulatory milestones (up to)				$ 250,000,000
Bristol Myers Squibb Collaboration Agreement \| Bristol-Myers Squibb Company \| Nektar 214
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of sharing production costs			35.00%
Bristol Myers Squibb Collaboration Agreement \| Bristol-Myers Squibb Company \| Nektar 214 \| Opdivo
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of sharing development costs			67.50%
Nektar's \| Nektar-358
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Received upfront and milestone payment				$ 150,000,000
Percentage of sharing in Phase 2 development costs				25.00%
Nektar's \| Bristol Myers Squibb Collaboration Agreement \| Nektar 214
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of sharing production costs			65.00%
Upfront and milestone payments received from license agreements					$ 1,000,000,000
Nektar's \| Bristol Myers Squibb Collaboration Agreement \| Nektar 214 \| Milestone One
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential future additional payments for development milestones											$ 50,000,000
Nektar's \| Bristol Myers Squibb Collaboration Agreement \| Nektar 214 \| Opdivo
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of sharing development costs			32.50%

Income Taxes - Schedule of Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Current:
Federal	$ 0	$ 0	$ 0
State	(43)	(608)	50
Foreign	(17)	1,115	609
Total current income tax expense	(60)	507	659
Deferred:
Federal	0	0	0
State	0	0	0
Foreign	(140)	2,708	(102)
Total deferred income tax expense	(140)	2,708	(102)
Provision (benefit) for income taxes	$ (200)	$ 3,215	$ 557

Consolidated Financial Statement Details - Schedule of Inventory (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Inventory Disclosure [Abstract]
Raw materials	$ 1,861	$ 2,575
Work-in-process	12,880	10,749
Finished goods	1,360	5,878
Total inventory	$ 16,101	$ 19,202

Restructuring, Impairment and Costs of Terminated Program - Restructuring Reserve Rollforward (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Jan. 31, 2023	Dec. 31, 2023	Dec. 31, 2022
Employee Severance
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance	$ 3,299	$ 3,299	$ 0
Expense recognized during the period		7,885	30,904
Payments during the period	(3,300)	(10,988)	(27,605)
Restructuring reserve, ending balance		196	3,299
Employee Severance \| 2023 Restructuring Plan
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance	0	0	0
Expense recognized during the period		7,885	0
Payments during the period		(7,689)	0
Restructuring reserve, ending balance		196	0
Employee Severance \| 2022 Restructuring Plan
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance	3,299	3,299	0
Expense recognized during the period		0	30,904
Payments during the period		(3,299)	(27,605)
Restructuring reserve, ending balance		0	3,299
Contract Termination and Other Costs \| 2022 Restructuring Plan
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance	$ 7,710	7,710	0
Expense recognized during the period		1,919	10,898
Payments during the period		(4,087)	(3,188)
Restructuring reserve, ending balance		$ 5,542	$ 7,710

Restructuring, Impairment and Costs of Terminated Program - Narrative (Details) - USD ($) $ in Thousands	1 Months Ended				3 Months Ended								9 Months Ended	12 Months Ended			21 Months Ended
	Jan. 31, 2024	Jun. 30, 2023	Jan. 31, 2023	Apr. 30, 2022	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2023
Restructuring Cost and Reserve [Line Items]
Non-cash impairment charges														$ 36,962	$ 67,875
Impairment of goodwill								$ 76,500						76,501	0	$ 0
Nektar 214 \| Bristol-Myers Squibb Company
Restructuring Cost and Reserve [Line Items]
Reimbursement of expenses													$ 20,800		20,800
Nektar 214 \| Research and Development Expense \| Bristol-Myers Squibb Company
Restructuring Cost and Reserve [Line Items]
Reimbursement of expenses												$ 24,900			45,700	$ 101,500
2022 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Non-cash impairment charges					$ 0	$ (1,467)	$ (13,261)	0	$ (12,361)	$ (1,200)	$ (52,200)						$ (80,489)
Contract termination and other costs included in accrued expenses					$ 3,000									3,000			$ 3,000
2023 Restructuring Plan \| Life Sciences Lease Market
Restructuring Cost and Reserve [Line Items]
Non-cash impairment charges						$ 9,100
2023 Restructuring Plan \| Office and Laboratory Space \| Mission Bay Facility
Restructuring Cost and Reserve [Line Items]
Non-cash impairment charges								$ 11,500						20,600
Measurement Input, Market Participant Subtenant Borrowing Rate \| Maximum
Restructuring Cost and Reserve [Line Items]
Operating lease, measurement input						8.70%
Measurement Input, Market Participant Subtenant Borrowing Rate \| Minimum
Restructuring Cost and Reserve [Line Items]
Operating lease, measurement input											6.40%
Employee Severance
Restructuring Cost and Reserve [Line Items]
Restructuring, impairment, and costs of terminated program														7,885	30,904
Payments during the period			$ 3,300											10,988	27,605
Employee Severance \| 2022 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Workforce termination, percentage				70.00%
Restructuring, impairment, and costs of terminated program														0	30,904
Payments during the period														3,299	27,605
Employee Severance \| 2023 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Workforce termination, percentage		60.00%
Restructuring, impairment, and costs of terminated program														7,885	0
Payments during the period														$ 7,689	$ 0
Employee Severance \| 2023 Restructuring Plan \| Subsequent Event
Restructuring Cost and Reserve [Line Items]
Payments during the period	$ 200

Stockholders' Equity - Additional Information (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Class of Stock [Line Items]
Losses recorded in AOCI	$ (130,987)	$ (366,638)	$ (679,508)	$ (1,077,295)
Common Stock
Class of Stock [Line Items]
Losses recorded in AOCI	(19)	(19)	$ (19)	$ (18)
Available-for-sale securities
Class of Stock [Line Items]
Losses recorded in AOCI	(50)	1,776
Foreign currency translation
Class of Stock [Line Items]
Losses recorded in AOCI	$ (30)	$ 5,131

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 2: http://www.xbrl.org/2003/role/recommendedDisclosureRef
-Topic 272
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483014/272-10-45-3

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 272
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482987/272-10-50-1

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(d))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-14

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-18

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(27)(b))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(28))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-2

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.6-03(i)(2))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479886/946-10-S99-3

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.6-03(i)(1))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479886/946-10-S99-3

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.6-03(i)(2)(i))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479886/946-10-S99-3

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.6-03(i)(2)(ii))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479886/946-10-S99-3

+ Details

- Definition

Amount of equity (deficit) attributable to parent. Excludes temporary equity and equity attributable to noncontrolling interest.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 852
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481372/852-10-55-10

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 946
-SubTopic 830
-Name Accounting Standards Codification
-Section 55
-Paragraph 12
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480167/946-830-55-12

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-04(19))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479617/946-210-S99-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.6-05(4))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479617/946-210-S99-2

Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.6-09(4)(b))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483575/946-220-S99-3

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.6-09(6))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483575/946-220-S99-3

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.6-09(7))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483575/946-220-S99-3

Reference 8: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(g)(1)(ii))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 9: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 323
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481687/323-10-50-3

Reference 10: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 28
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482907/825-10-50-28

Reference 11: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1

Reference 12: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(31))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1

Reference 13: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(30))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1

Reference 14: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 4.E)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480418/310-10-S99-2

+ Details

Restructuring, Impairment and Costs of Terminated Program

12 Months Ended

Dec. 31, 2023

Restructuring and Related Activities [Abstract]

Restructuring, Impairment and Costs of Terminated Program

Note 8 — Restructuring, Impairment and Costs of Terminated Program

As discussed in Note 1, because our registrational trials in bempegaldesleukin did not meet their primary endpoints, we decided to discontinue all development of bempegaldesleukin and wind down the clinical trials studying bempegaldesleukin. In April 2022, we announced the 2022 Restructuring Plan pursuant to which we completed an approximate 70% reduction of our workforce during 2022. We also sold our research facility in India in December 2022 and decided to sublease certain of our leased premises in San Francisco, CA, including all of our office leased space in the Third Street Facility and portions of our office and laboratory space in the Mission Bay Facility.

Pursuant to plans approved by our Board in March 2023, we announced the 2023 Restructuring Plan to further reduce our San Francisco-based workforce by approximately 60%, which was substantially completed by June 30, 2023. In addition, under the 2023 Restructuring Plan, we decided to sublease our remaining office and laboratory space in the Mission Bay Facility, which we had not planned to sublease pursuant to the 2022 Restructuring Plan.

In connection with our 2022 and 2023 Restructuring Plans, we report the following costs in restructuring, impairment and costs of terminated program:

•

Clinical trial expense, other third-party costs and employee costs for the wind down of the bempegaldesleukin program, net of the reimbursement from BMS, initiated in 2022;

•

Severance and related benefit costs pursuant to the 2022 and 2023 Restructuring Plans;

•

Non-cash impairment of right-of-use assets and property, plant and equipment; and

•

Contract termination and other costs associated with these plans.

Restructuring, impairment and costs of terminated program includes the following (in thousands):


	Year Ended December 31,
	2023						2022
	2022 Restructuring Plan		2023 Restructuring Plan		Total		2022 Restructuring Plan
Clinical trial expense, other third-party and employee costs for the wind down of the bempegaldesleukin program	$	5,492	$	—	$	5,492	$	31,693
Severance and benefit expense		—		7,885		7,885		30,904
Impairment of right-of-use assets and property, plant and equipment		14,728		20,600		35,328		65,761
Loss (gain) on sale or disposal of other property, plant and equipment, net		—		1,300		1,300		(3,326	)
Contract termination and other restructuring costs		1,919		34		1,953		10,898
Restructuring, impairment and costs of terminated program	$	22,139	$	29,819	$	51,958	$	135,930

Wind Down of the Bempegaldesleukin Program

In prior periods through March 31, 2022, we reported the clinical trial costs, other third-party costs and employee costs related to the bempegaldesleukin program primarily in research and development expense. Beginning in the second quarter of 2022, we began reporting clinical trial, other third-party costs and employee costs for the wind down of the bempegaldesleukin program in restructuring, impairment and costs of terminated program.

The clinical trial expense, other third-party and employee costs for the wind down of the bempegaldesleukin program for the year ended December 31, 2022 includes reductions of $20.8 million, for the net reimbursement from BMS. The net reimbursement payable to BMS for the year ended December 31, 2023 was not significant.

Severance and Benefit Expense

Employees affected by the reduction in force under the 2022 and 2023 Restructuring Plans are entitled to receive severance payments and certain Company funded benefits. The restructuring charges are recorded at fair value.

For the 2022 Restructuring Plan, we recognized severance and benefit expense in full for employees who had no requirements for future service upon approval of the 2022 Restructuring Plan by the Board in April 2022. We recognized severance and benefit expense for employees who were required to render services to receive their severance and benefits ratably over the service period. This service period began on the communication date in April 2022 and was completed for all employees during 2022. We recognized $30.9 million in total severance and benefit expense during 2022 and paid the remaining liability of $3.3 million in January 2023.

For the 2023 Restructuring Plan, we recognized $7.9 million of severance and benefit expense for the year ended December 31, 2023 and paid the final liability of $0.2 million in January 2024. We do not expect to recognize any further severance expense for the 2023 Restructuring Plan.

The following table provides details regarding the severance and benefit expense for the years ended December 31, 2023 and 2022 pursuant to the 2022 and 2023 Restructuring Plans and a reconciliation of the severance and benefits liability for the year ended December 31, 2023 pursuant to the 2022 and 2023 Restructuring Plans, which we report within accrued expenses on our Consolidated Balance Sheets (in thousands):


	2023 Restructuring Plan			2022 Restructuring Plan			Total
Liability balance as of December 31, 2021	$	—		$	—		$	—
Expense recognized during the period		—			30,904			30,904
Payments during the period		—			(27,605	)		(27,605	)
Liability balance as of December 31, 2022	$	—		$	3,299		$	3,299
Expense recognized during the period		7,885			—			7,885
Payments during the period		(7,689	)		(3,299	)		(10,988	)
Liability balance as of December 31, 2023	$	196		$	—		$	196

Impairment of Long-Lived Assets

As a result of our 2022 and 2023 Restructuring Plans, we have decided to sublease all of our leased spaces in the Third Street Facility and the Mission Bay Facility. Accordingly, we evaluated each space for impairment when management decided to sublease the respective space and at each reporting date thereafter, as facts and circumstances change. The significant assumptions in our impairment analysis relate to sublease income, including the length of time to enter into a sublease, sublease rental payments, free rent periods, tenant improvement allowances and broker commissions. When available, we use sublease negotiations or agreements, but in the absence of such information, we develop our own subjective estimates based on current real estate trends and market conditions. Accordingly, our estimates are subject to significant risk, and the terms of sublease agreements, if any, and the resulting amount and timing of sublease income, if ever realized, may be materially different than our estimates.

As part of our evaluation of each sublease space, we separately compare the estimated undiscounted sublease income, as described above, for each sublease to the net book value of the related long-term assets, which include right-of-use assets and certain property, plant and equipment, primarily for leasehold improvements (collectively, sublease assets). If such sublease income exceeds the net book value of the sublease assets, we do not record an impairment charge. Otherwise, we record an impairment charge by reducing the net book value of the sublease assets to their estimated fair value, which we determined by discounting the estimated sublease income using the estimated borrowing rate of a market participant subtenant, which has ranged from 6.4% for the three months ended June 30, 2022 to 8.7% for the three months ended September 30, 2023.

We recorded non-cash impairment charges of lease assets pertaining to the 2022 and 2023 Restructuring Plans as follows (in thousands):


	Three-months Ended
Sublease Spaces	June 30, 2022		September 30, 2022		December 31, 2022		March 31, 2023		June 30, 2023		September 30, 2023		December 31, 2023		Total
Mission Bay Blvd. South	$	3,000	$	1,200	$	361	$	—	$	7,061	$	1,467	$	—	$	13,089
Third St		49,200		—		12,000		—		6,200		—		—		67,400
Total 2022 Restructuring Plan		52,200		1,200		12,361		—		13,261		1,467		—		80,489
Mission Bay Blvd. South - 2023 Restructuring Plan	N/A		N/A		N/A			11,500		—		9,100		—		20,600
Total impairment of lease assets	$	52,200	$	1,200	$	12,361	$	11,500	$	13,261	$	10,567	$	—	$	101,089

•

The non-cash impairment charges for the three months ended June 30, 2022 for our Third St. Facility reflects our initial estimates of sublease income when management first decided to sublease the spaces. As the San Francisco office lease market has continued to deteriorate, we have recognized additional non-cash impairment charges for the Third Street Facility in the three months ended December 31, 2022, and in the three months ended June 30, 2023.

•

The non-cash impairment charges for the three months ended June 30, 2022 for Mission Bay Facility reflects our initial estimates of sublease income. As the life sciences lease market has deteriorated during 2023, we recorded additional non-cash impairment charges in the three months ended June 30, 2023 and in the three months ended September 30, 2023.

•

The impairment charges under the 2023 Restructuring Plan include $20.6 million for the impairment of the Mission Bay Facility that we decided to sublease in 2023. We recorded an impairment charge of $11.5 million in the three months ended March 31, 2023, based on our initial estimates of sublease income. As the life sciences lease market has deteriorated during 2023, including a significant increase in available sublease space in San Francisco, California, we recorded an additional impairment charge of $9.1 million in the three months ended September 30, 2023 for this space.

The following are reconciliations of the impairment charges we recorded for the years ended December 31, 2023 and 2022, including the net book values of the sublease assets before the impairment and the fair values of the sublease assets. Since we recorded multiple impairment charges for certain spaces as a resulting of worsening lease markets, we present the net book value before the first impairment in such year and the fair value after the second impairment in such year (in thousands):


	Year Ended December 31, 2022
	Operating Lease			Property, Plant and
	Right-of-Use Assets			Equipment			Total
Net book value of impaired sublease assets	$	72,481		$	16,348		$	88,829
Less: Fair value of impaired sublease assets — Level 3 of Fair Value Hierarchy		(16,174	)		(4,780	)		(20,954	)
Book value in excess of fair value		56,307			11,568			67,875
Less: Amounts recorded as amortization between June 30, 2022 and December 31, 2022 for Third St. facility		(1,717	)		(397	)		(2,114	)
Total impairment of sublease assets	$	54,590		$	11,171		$	65,761


	Year Ended December 31, 2023
	Operating Lease Right-of-Use Assets			Property, Plant and Equipment			Total
Net book value of impaired facilities before write-off	$	46,292		$	7,206		$	53,498
Less: Fair value of impaired facilities — Level 3 of Fair Value Hierarchy		(14,364	)		(2,172	)		(16,536	)
Book value in excess of fair value		31,928			5,034			36,962
Less: Amounts recorded as amortization between March 31, 2023 and September 30, 2023 for Mission Bay facility		(1,371	)		(263	)		(1,634	)
Total impairment of right-of-use assets and property, plant and equipment	$	30,557		$	4,771		$	35,328

(Gain) Loss on Sale or Disposal of Property, Plant and Equipment, Net

In connection with our 2022 Restructuring Plan, we terminated all research and development activities at our owned facility in India, which we sold in December 2022. We also sold excess lab equipment and disposed of software to support the commercialization of bempegaldesleukin. In 2023, we sold additional lab equipment under the 2023 Restructuring Plan. We recorded the gains and losses as follows (in thousands):


	Year Ended December 31,
	2023		2022
Proceeds from sales	$	1,245	$	13,196
Net book value of assets		2,545		9,870
Total (gain) loss on sale or disposal of other property, plant and equipment, net	$	1,300	$	(3,326	)

Contract Termination and Other Costs

The following is a reconciliation of the contract termination and other costs for the 2022 Restructuring Plan and the related liability of which we report $3.0 million within accrued expenses and the remaining within other long-term liabilities on our Consolidated Balance Sheet as of December 31, 2023:


	Year Ended
	December 31, 2023
Liability balance as of December 31, 2021	$	—
Expense recognized during the period		10,898
Payments during the period		(3,188	)
Liability balance as of December 31, 2022		7,710
Expense recognized during the period		1,919
Payments during the period		(4,087	)
Liability balance as of December 31, 2023	$	5,542

Property, Plant and Equipment - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Abstract]
Depreciation and amortization expenses	$ 7.0	$ 12.2	$ 13.0

Cash and Investments in Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2023

Fair Value Disclosures [Abstract]

Schedule of Cash and Investments in Marketable Securities, Including Cash Equivalents

Cash and investments in marketable securities, including cash equivalents, are as follows (in thousands):


	Estimated Fair Value at
	December 31,		December 31,
	2023		2022
Cash and cash equivalents	$	35,277	$	88,227
Short-term investments		268,339		416,750
Long-term investments		25,825		—
Total cash and investments in marketable securities	$	329,441	$	504,977

Schedule of Portfolio of Cash and Investments in Marketable Securities

Our portfolio of cash and investments in marketable securities includes (in thousands):


				December 31, 2023							December 31, 2022
	Fair Value Hierarchy			Gross Unrealized		Gross Unrealized
	Level	Amortized Cost		Gains		Losses			Fair Value		Fair Value
Corporate notes and bonds	2	$	38,799	$	85	$	(2	)	$	38,882	$	83,522
Corporate commercial paper	2		255,274		47		(80	)		255,241		344,204
Available-for-sale investments			294,073		132		(82	)		294,123		427,726
Money market funds	1									2,359		47,054
Certificates of deposit	2									15,116		21,399
Cash	N/A									17,843		8,798
Total cash and investments in marketable securities									$	329,441	$	504,977

Organization and Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Summary of Significant Accounting Policies	Note 1 — Organization and Summary of Significant Accounting Policies Organization We are a clinical stage, research-based drug discovery biopharmaceutical company headquartered in San Francisco, California and incorporated in Delaware, focused on discovering and developing innovative medicines in the field of immunotherapy. Within this growing field, we direct our efforts toward creating new immunomodulatory agents that selectively induce, amplify, attenuate or prevent immune responses in order to achieve desired therapeutic outcomes. Our pipeline of clinical-stage and preclinical-stage immunomodulatory agents targets the treatment of autoimmune diseases (e.g. rezpegaldesleukin and NKTR-0165, respectively) and cancer (e.g. NKTR-255). Our research and development activities have required significant ongoing investment to date and are expected to continue to require significant investment. As a result, we expect to continue to incur substantial losses and negative cash flows from operations in the future. We have financed our operations primarily through cash generated from licensing, collaboration and manufacturing agreements and financing transactions. At December 31, 2023, we had approximately $329.4 million in cash and investments in marketable securities. Results of Clinical Trial Programs and Restructuring Plans In March and April 2022, we announced that our registrational trials of bempegaldesleukin in combination with Opdivo® in metastatic melanoma, renal cell carcinoma and locally advanced or metastatic urothelial cancer under our Strategic Collaboration Agreement (BMS Collaboration Agreement) with Bristol-Myers Squibb Company (BMS) did not meet their primary endpoints. Based on these results, in April 2022, we announced our decisions to discontinue all development of bempegaldesleukin in combination with checkpoint inhibitors, including these trials, our registrational trial in adjuvant melanoma under our BMS Collaboration Agreement, and our Phase 2/3 study of bempegaldesleukin in combination with Keytruda® in squamous cell cancer of the head and neck under our Co-Development Agreement with SFJ Pharmaceuticals XII, L.P., an SFJ Pharmaceuticals Group company (SFJ). See Note 7 for additional information regarding our BMS Collaboration Agreement and Co-Development Agreement with SFJ. On September 6, 2023, BMS and we terminated the BMS Collaboration Agreement, however, we continue our efforts to wind down the bempegaldesleukin program following the same cost sharing provisions provided for in the BMS Collaboration Agreement. In April 2022, we also announced new strategic reorganization and cost restructuring plans (together, the 2022 Restructuring Plan), pursuant to which we completed an approximate 70% reduction of our workforce during 2022 and sold our research facility in India in December 2022. We also decided to sublease certain of our leased premises in San Francisco, CA, including all of our office leased space on Third St. (the Third Street Facility) and portions of our office and laboratory space on Mission Bay Blvd. South (the Mission Bay Facility). On February 23, 2023, we announced the topline data from the Phase 2 study of rezpegaldesleukin in adult patients with systemic lupus erythematosus (SLE) (Phase 2 Lupus Study) under our collaboration agreement with Eli Lilly and Company (Lilly). Lilly subsequently notified us that it did not intend to advance rezpegaldesleukin into Phase 3 development for SLE. On April 27, 2023, we announced that we would be regaining the full rights to rezpegaldesleukin from Lilly, and the collaboration agreement was subsequently terminated. We have initiated a Phase 2b study of rezpegaldesleukin in patients with moderate-to-severe atopic dermatitis, and we are targeting the initiation of a Phase 2b study of rezpegaldesleukin in patients with alopecia areata by the end of March 2024. We also plan to explore other auto-immune indications for the development of rezpegaldesleukin. Pursuant to plans approved by our Board of Directors (the Board) on March 29, 2023, we announced on April 17, 2023, a new strategic reprioritization and cost restructuring plan (the 2023 Restructuring Plan). Under the 2023 Restructuring Plan, we reduced our San Francisco-based workforce by approximately 60%, which was substantially completed by June 2023. In addition, under the 2023 Restructuring Plan, we decided to sublease our remaining office and laboratory space on Mission Bay Blvd. South which we had not planned to sublease pursuant to the 2022 Restructuring Plan. We have incurred significant costs resulting from the 2022 and 2023 Restructuring Plans. See Note 8 for additional information on the effect of these Plans on our Consolidated Financial Statements. Basis of Presentation, Principles of Consolidation and Use of Estimates Our Consolidated Financial Statements include the financial position, results of operations and cash flows of our wholly-owned subsidiaries. We have eliminated all intercompany accounts and transactions in consolidation. Our Consolidated Financial Statements are denominated in U.S. dollars. Accordingly, changes in exchange rates between the applicable foreign currency and the U.S. dollar will affect the translation of each foreign subsidiary’s financial results into U.S. dollars for purposes of reporting our consolidated financial results. We include translation gains and losses in accumulated other comprehensive income (loss) in the stockholders’ equity section of our Consolidated Balance Sheets. Our comprehensive loss consists of our net loss plus our foreign currency translation gains and losses and unrealized holding gains and losses on available-for-sale securities. Other than as described in Note 3, there were no significant reclassifications out of accumulated other comprehensive loss to the statements of operations for the periods presented. The preparation of consolidated financial statements in conformity with U.S. generally accepted accounting principles (GAAP) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenue and expenses during the reporting period. Accounting estimates and assumptions are inherently uncertain. Actual results could differ materially from those estimates and assumptions. Our estimates include those related to the selling prices of performance obligations and amounts of variable consideration in collaboration agreements, royalty revenue, and other assumptions required for revenue recognition as described further below; the net realizable value of inventory; the fair value and impairment of investments, goodwill and long-lived assets; contingencies, accrued clinical trial, contract manufacturing and other expenses; income taxes; non-cash royalty revenue and non-cash interest expense from our liabilities related to our sales of future royalties; our assumptions used in stock-based compensation; and ongoing litigation, among other estimates. We base our estimates on historical experience and on other assumptions that management believes are reasonable under the circumstances. These estimates form the basis for making judgments about the carrying values of assets and liabilities when these values are not readily apparent from other sources. As appropriate, we assess estimates each period, update them to reflect current information, and will generally reflect any changes in estimates in the period first identified. Fair Value of Financial Instruments The recorded amounts of certain financial instruments, including cash and cash equivalents, accounts receivable, accounts payable and accrued liabilities approximate their fair values due to their relatively short maturities. We record available-for-sale investments and cash equivalents at their estimated fair values, which are based on market prices from a variety of industry standard data providers and generally represent quoted prices for similar assets in active markets or have been derived from observable market data. As further described in Note 8, we estimated the fair value of our lease assets for recognizing impairment charges based on management’s estimates of several unobservable inputs, including estimated time to enter a sublease, sublease rental rates and free rent periods. The fair value of our financial assets and liabilities are determined in accordance with the fair value hierarchy established in ASC 820-10, Fair Value Measurements and Disclosures (ASC 820). ASC 820 defines fair value as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. The fair value hierarchy of ASC Topic 820 requires an entity to maximize the use of observable inputs when measuring fair value and classifies those inputs into three levels: Level 1 — Quoted prices in active markets for identical assets or liabilities. Level 2 — Inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices for identical or similar assets or liabilities in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. For the years ended December 31, 2023 and 2022, there were no transfers between Level 1 and Level 2 of the fair value hierarchy. Level 3 — Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. Cash, Cash Equivalents, and Investments in Marketable Securities We consider all investments in marketable securities with an original maturity of three months or less when purchased to be cash equivalents. We classify investments in securities with remaining maturities of less than one year, or where our intent is to use the investments to fund current operations or to make them available for current operations, as short-term investments. We classify investments in securities with remaining maturities of over one year as long-term investments. Our cash and investments are held or issued by financial institutions that management believes are of high credit quality. However, we are exposed to credit risk in the event of default by the third parties that hold or issue such assets. Our investment policy limits investments to fixed income securities denominated and payable in U.S. dollars such as corporate bonds, corporate commercial paper, U.S. government obligations, and money market funds and places restrictions on maturities and concentrations by type and issuer. For our available-for-sale securities, we have significant concentrations of issuers in the banking and financial services industry. While our investment policy requires that we only invest in highly-rated securities and limit our exposure to any single issuer, a variety of factors may materially affect the financial condition of issuers. Additionally, pursuant to our investment policy, we may sell securities before maturity if the issuer’s credit rating has been downgraded below our minimum credit rating requirements, which may result in a loss on the sale. Accordingly, if factors result in downgrades below our minimum credit rating requirements and if we decide to sell these securities, we may experience losses on such sales. Investments are designated as available-for-sale and are carried at fair value with unrealized gains and losses reported in stockholders’ equity as accumulated other comprehensive income (loss). We review our portfolio of available-for-sale debt securities, using both quantitative and qualitative factors, to determine if declines in fair value below amortized cost have resulted from a credit-related loss or other factors. If the decline in fair value is due to credit-related factors, we recognize a loss in our Consolidated Statement of Operations, whereas if the decline in fair value is not due to credit-related factors, we recognize the loss in other comprehensive income (loss). We include coupon interest on securities classified as available-for-sale, as well as amortization of premiums and accretion of discounts to maturity, in interest income. The cost of securities sold is based on the specific identification method. Accounts Receivable and Significant Customer Concentrations Our customers are primarily pharmaceutical and biotechnology companies that are primarily located in the U.S. and Europe and with whom we have multi-year arrangements. Our accounts receivable balance contains billed and unbilled trade receivables from product sales, milestones (to the extent that they have been achieved and are due from the counterparty), other contingent payments, as well as reimbursable costs from collaborative research and development agreements. We perform a regular review of our partners’ credit risk and payment histories when circumstances warrant, including payments made subsequent to year-end. When appropriate, we provide for an allowance for doubtful accounts by reserving for specifically identified doubtful accounts, although historically we have not experienced credit losses from our accounts receivable. We have not recorded provisions for credit losses for any of the periods presented. Inventory and Significant Supplier Concentrations We generally manufacture inventory upon receipt of firm purchase orders from our partners, and we may manufacture certain intermediate work-in-process materials and purchase raw materials based on purchase forecasts from our partners. Inventory includes direct materials, direct labor, and manufacturing overhead, and we determine cost on a first-in, first-out basis for raw materials and on a specific identification basis for work-in-process and finished goods. We value inventory at the lower of cost or net realizable value, and we write down defective or excess inventory to net realizable value based on historical experience or projected usage. We expense inventory related to our research and development activities when we purchase or manufacture it. We are dependent on our suppliers and contract manufacturers to provide raw materials and drugs of appropriate quality and reliability and to meet applicable contract and regulatory requirements. In certain cases, we rely on single sources of supply of one or more critical materials. Consequently, in the event that supplies are delayed or interrupted for any reason, our ability to develop and produce our drug candidates or our ability to meet our supply obligations could be significantly impaired, which could have a material adverse effect on our business, financial condition and results of operations. Restructuring We recognize restructuring charges related to reorganization plans that have been committed to by management when liabilities have been incurred. In connection with these activities, we record restructuring charges at fair value for: • contractual employee termination benefits provided that the obligations result from services already rendered based on vested rights to such benefits when the payment of benefits becomes probable and the amount can be reasonably estimated; • one-time employee termination benefits on the communication date from management to the employees provided that management has committed to a plan of termination, the plan identifies the employees and their expected termination dates, the details of termination benefits are complete, and it is unlikely that changes to the plan will be made or the plan will be withdrawn; • contract termination costs when we cancel the contract in accordance with its terms; and • costs to be incurred over the remaining contract term without economic benefit to us at the cease-use date. For one-time employee termination benefits, we recognize the liability in full on the communication date when future services are not required or amortize the liability ratably over the service period, if required. The fair value of termination benefits reflects our estimates of expected utilization of certain Company-funded post-employment benefits. See Note 8 for additional information on the severance expense that we recognized for employees terminated in connection with our reductions-in-force. Goodwill Goodwill represents the excess of the price paid for another entity over the fair value of the assets acquired and liabilities assumed in a business combination. We are organized in one reporting unit and evaluate the goodwill for the Company as a whole. Goodwill has an indefinite useful life and is not amortized, but instead tested for impairment. Goodwill is assessed for impairment on an annual basis and whenever events and circumstances indicate that it may be impaired. Factors that may indicate potential impairment and trigger an impairment test include, but are not limited to, current economic, market and geopolitical conditions, including a significant, sustained decline in our stock price and market capitalization compared to the net book value; an adverse change in legal factors, business climate or operational performance of the business; or significant changes in the ability of the reporting unit to generate positive cash flows for our strategic business objectives. If the carrying value of the reporting unit, including goodwill, exceeds the reporting unit’s fair value, we will recognize a goodwill impairment loss, and we will write down goodwill such that the carrying value of the reporting unit equals its fair value, provided that we cannot reduce goodwill below zero. See Note 9 for additional information regarding the impairment charges we recorded during the three months ended March 31, 2023 in connection with our goodwill. Long-Lived Assets We report property, plant and equipment at cost, net of accumulated depreciation. We capitalize major improvements and expense maintenance and repairs as incurred. We generally recognize depreciation on a straight-line basis. We depreciate manufacturing, laboratory and other equipment over their estimated useful lives of generally three to ten years, depreciate buildings over the estimated useful life of generally twenty years and amortize leasehold improvements over the shorter of the estimated useful lives or the remaining term of the related lease. We assess the impairment of long-lived assets whenever events or changes in business circumstances indicate that the carrying amounts of the assets may not be fully recoverable. In the case of property, plant and equipment and right-of-use assets for our leases, we determine whether there has been an impairment by comparing the carrying value of the asset to the anticipated undiscounted net cash flows associated with the asset. If such cash flows are less than the carrying value, we write down the asset to its fair value, which may be measured as anticipated net cash flows associated with the asset, discounted at a rate that we believe a market participant would utilize to reflect the risks associated with the cash flows, such as credit risk. See Note 8 for additional information regarding the impairment charges we recorded in connection with our leased facilities and certain property and equipment. Leases We determine if an arrangement contains a lease at the inception of the arrangement. Right-of-use assets represent our right to use an underlying asset for the lease term, and lease liabilities represent our obligation to make lease payments arising from the lease. We recognize operating lease right-of-use assets and liabilities at the lease commencement date based on the present value of lease payments over the expected lease term. In determining the present value of lease payments, we use our incremental borrowing rate based on the information available at the lease commencement date. We have elected the practical expedient to account for the lease and non-lease components, such as common area maintenance charges, as a single lease component for our facilities leases, and elected the short-term lease recognition exemption for our short-term leases, under which we do not recognize lease liabilities and right-of-use assets for leases with an original term of twelve months or less. Our expected lease terms may include options to extend or terminate the lease when it is reasonably certain that we will exercise any such options. We recognize lease expense for our operating leases on a straight-line basis over the expected lease term. We have elected to recognize lease incentives, such as tenant improvement allowances, at the lease commencement date as a reduction of the right-of-use asset and lease liability until paid to us by the lessor to the extent that the lease provides a specified fixed or maximum level of reimbursement and we are reasonably certain to incur reimbursable costs at least equaling such amounts. Please see Note 4 for additional information regarding our leases. Collaborative Arrangements We enter into collaboration arrangements with pharmaceutical and biotechnology collaboration partners, under which we may grant licenses to our collaboration partners to further develop and commercialize one of our drug candidates, either alone or in combination with the collaboration partners’ compounds, or grant licenses to partners to use our technology to research and develop their own drug candidates. We may also perform research, development, manufacturing and supply activities under our collaboration agreements. Consideration under these contracts may include an upfront payment, development and regulatory milestones and other contingent payments, expense reimbursements, royalties based on net sales of approved drugs, and commercial sales milestone payments. Additionally, these contracts may provide options for the customer to purchase our proprietary PEGylation materials, drug candidates or additional contract research and development services under separate contracts. When we enter into collaboration agreements, we assess whether the arrangements fall within the scope of ASC 808, Collaborative Arrangements (ASC 808) based on whether the arrangements involve joint operating activities and whether both parties have active participation in the arrangement and are exposed to significant risks and rewards of the arrangement. To the extent that the arrangement falls within the scope of ASC 808, we assess whether the payments between us and our collaboration partner fall within the scope of other accounting literature. If we conclude that payments from the collaboration partner to us represent consideration from a customer, such as license fees and contract research and development activities, we account for those payments within the scope of ASC 606, Revenue from Contracts with Customers (ASC 606). However, if we conclude that our collaboration partner is not a customer for certain activities and associated payments, such as for certain collaborative research, development, manufacturing and commercial activities, we present such payments as a reduction of research and development expense or general and administrative expense, based on where we present the underlying expense. Revenue Recognition For elements of those arrangements that we determine should be accounted for under ASC 606, we assess which activities in our collaboration agreements are performance obligations that should be accounted for separately and determine the transaction price of the arrangement, which includes the assessment of the probability of achievement of future milestones and other potential consideration. For arrangements that include multiple performance obligations, such as granting a license or performing contract research and development activities or participation on joint steering or other committees, we allocate upfront and milestone payments under a relative standalone selling price method. Accordingly, we develop assumptions that require judgment to determine the standalone selling price for each performance obligation identified in the contract. These key assumptions may include revenue forecasts, clinical development timelines and costs, discount rates and probabilities of clinical and regulatory success. Product sales Product sales are primarily derived from manufacturing and supply agreements with our customers. We have assessed our current manufacturing and supply arrangements and have generally determined that they provide the customer an option to purchase our proprietary PEGylation materials. Accordingly, we treat each purchase order as a discrete exercise of the customer’s option (i.e. a separate contract) rather than as a component of the overall arrangement. The pricing for the manufacturing and supply is generally at a fixed price and may be subject to annual producer price index (PPI) adjustments. We invoice and recognize product sales when title and risk of loss pass to the customer, which generally occurs upon shipment. Customer payments are generally due 30 days from receipt of an invoice. We test our products for adherence to technical specifications before shipment; accordingly, we have not experienced any significant returns from our customers. We recognize costs related to shipping and handling of product to customers in cost of goods sold. Non-cash royalty revenue Generally, for our collaboration arrangements that include sales-based royalties, we have granted our collaboration partner a license to our intellectual property. Pursuant to these arrangements, our collaboration partners are typically obligated to pay a royalty that is based on the net sales of their approved drugs that are sold in the countries where we have intellectual property rights covering their drugs. We have sold our rights to receive sales-based royalties for CIMZIA®, MIRCERA®, MOVANTIK®, ADYNOVATE® and REBINYN® as further described in Note 5. For collaboration arrangements that include sales-based royalties, we have concluded that the license is the predominant item to which the royalties relate, which include commercial milestone payments based on the level of sales. Accordingly, we recognize royalty revenue when the underlying sales occur based on our best estimates of sales of the drugs. Our aggregate royalty and non-cash royalty revenue of $68.9 million, $69.8 million and $77.7 million for the years ended December 31, 2023, 2022 and 2021, respectively, represents revenue for granting licenses for which we had satisfied in prior periods. License, collaboration and other revenue License Grants: For collaboration arrangements that include a grant of a license to our intellectual property, we consider whether the license grant is distinct from the other performance obligations included in the arrangement. Generally, we would conclude that the license is distinct if the customer is able to benefit from the license with the resources available to it. For licenses that are distinct, we recognize revenues from nonrefundable, upfront payments and other consideration allocated to the license when the license term has begun and we have provided all necessary information regarding the underlying intellectual property to the customer, which generally occurs at or near the inception of the arrangement. Milestone Payments: At the inception of the arrangement and at each reporting date thereafter, we assess whether we should include any milestone payments or other forms of variable consideration in the transaction price, based on whether a significant reversal of revenue previously recognized is not probable upon resolution of the uncertainty. Since milestone payments may become payable to us upon the initiation of a clinical study, filing for or receipt of regulatory approval or the first commercial sale of a product, we review the relevant facts and circumstances to determine when we should update the transaction price, which may occur before the triggering event. When we do update the transaction price for milestone payments, we allocate it on a relative standalone selling price basis and record revenue on a cumulative catch-up basis, which results in recognizing revenue for previously satisfied performance obligations in such period. If we update the transaction price before the triggering event, we recognize the increase in the transaction price as a contract asset. Our partners generally pay development milestones subsequent to achievement of the triggering event. Research and Development Services: For amounts allocated to our research and development obligations in a collaboration arrangement, we recognize revenue over time using a proportional performance model, representing the transfer of goods or services as we perform activities over the term of the agreement. Research and Development Expense Research and development costs are expensed as incurred and include salaries, benefits and other operating costs such as outside services, supplies and allocated overhead costs. We perform research and development activities for our drug candidates and technology development and for certain third parties under collaboration agreements. For our drug candidates and our internal technology development programs, we invest our own funds without reimbursement from a third party. Where we perform research and development activities under a joint development collaboration, such as our collaboration with BMS, we record the cost reimbursement from our partner as a reduction to research and development expense when reimbursement amounts are due to us under the agreement. We record an accrued expense for the estimated unbilled costs of our clinical study activities performed by third parties. The financial terms of these agreements are subject to negotiation, vary from contract to contract and may result in uneven payment flows to our vendors. Payments under the contracts depend on factors such as the achievement of certain events, successful enrollment of patients and completion of certain clinical trial activities. We generally recognize costs associated with the start-up and reporting phases of the clinical trials as incurred. We generally accrue costs associated with the treatment phase of clinical trials based on the estimated activities performed by our third party vendors, including our contract research organizations. We may also accrue expenses based on the total estimated cost of the treatment phase on a per patient basis and expense the per patient cost ratably over the estimated patient treatment period. In specific circumstances, such as for certain time-based costs, we recognize clinical trial expenses ratably over the service period, as we believe that this methodology may be more reflective of the timing of costs incurred. We capitalize advance payments for goods or services that will be used or rendered for future research and development activities and recognize expense as the related goods are delivered or services performed. We base our estimates on the best information available at the time. However, additional information may become available to us in the future which may allow us to make a more accurate estimate in future periods. In this event, we may be required to record adjustments to research and development expenses in future periods when the actual level of activity becomes more certain. We generally consider such increases or decreases in cost as changes in estimates and reflect them in research and development expenses in the period identified. Restructuring, Impairment and Other Costs for Terminated Program Amounts recorded as restructuring, impairment and other costs for terminated program for the year ended December 31, 2023 and 2022 relate to the 2022 and 2023 Restructuring Plans. See Note 8 for additional information. Stock-Based Compensation Stock-based compensation arrangements include grants of stock options, restricted stock units (RSUs), performance stock units (PSUs) under our equity incentive plans, as well as shares issued under our Employee Stock Purchase Plan (ESPP), through which employees may purchase our common stock at a discount to the market price. We expense the grant date fair value of stock-based compensation on a straight-line basis over the requisite service periods in our Consolidated Statements of Operations and recognize forfeitures as they occur. For options and RSUs that vest upon the achievement of performance milestones, we recognize expense provided that we believe that the performance milestones are probable of achievement, and we estimate the vesting period based on our evaluation of the estimated date of achievement of these milestones. For PSUs, we recognize expense based on the grant date fair value regardless of whether the market condition is met. The number of shares issuable under PSUs is based on our total shareholder return as compared to other companies within the NASDAQ biotechnology index over the measurement period and may be capped based on our absolute total shareholder return over such period. We report expense amounts in cost of goods sold, research and development expense, and general and administrative expense based on the function of the applicable employee. We estimate the grant date fair value of our stock-based compensation awards as follows: • Stock options - We use the Black-Scholes option pricing model for the respective grant to determine the grant date fair value of stock options and common stock issued under the Company's equity incentive plans or purchased under the ESPP. The Black-Scholes option pricing model requires the input of assumptions, including but not limited to, our stock price volatility over the term of the awards, and actual and projected employee stock option exercise behaviors. • PSUs - We use the Monte Carlo simulation model to determine the grant date fair value of PSUs. The Monte Carlo simulation model incorporates assumptions such as the volatility of our stock, the volatility of the stock of other peer companies within the index, and the correlation of both our stock and our peer companies’ stock to the index. • RSUs - The fair value of an RSU is equal to the closing price of our common stock on the grant date. Income Taxes We account for income taxes under the liability method. Under this method, we determine deferred tax assets and liabilities based on differences between the financial reporting and tax reporting bases of assets and liabilities, measured using enacted tax rates and laws that we expect to be in effect when we expect the differences to reverse. Realization of deferred tax assets is dependent upon future earnings, the timing and amount of which are uncertain. We record a valuation allowance against deferred tax assets to reduce their carrying value to an amount that is more likely than not to be realized. When we establish or reduce the valuation allowance related to the deferred tax assets, our provision for income taxes will increase or decrease, respectively, in the period we make such determination. We utilize a two-step approach to recognize and measure uncertain tax positions. The first step is to evaluate the tax position for recognition by determining if the weight of available evidence indicates that it is more likely than not that the position will be sustained upon tax authority examination, including resolution of related appeals or litigation processes, if any. The second step is to measure the tax benefit as the largest amount of benefit, determined on a cumulative probability basis, that is more than 50% likely of being realized upon ultimate settlement. For the year ended December 31, 2023, our income tax benefit was immaterial. For the years ended December 31, 2022 and 2021, our income tax provision primarily relates to our Nektar India subsidiary. As a result of the 2022 Restructuring Plan and our intent to wind down our foreign subsidiaries, we have recorded a provision for the repatriation of accumulated earnings and profits from India. See Note 10 for additional information. Net Loss Per Share For all periods presented in the Consolidated Statements of Operations, the net loss available to common stockholders is equal to the reported net loss. We calculate basic net loss per share based on the weighted-average number of common shares outstanding during the periods presented. For the years ended December 31, 2023, 2022 and 2021, basic and diluted net loss per share are the same due to our net losses and the requirement to exclude potentially dilutive securities which would have an antidilutive effect on net loss per share. We excluded shares underlying the weighted average outstanding stock options, RSUs and PSUs, which totaled 20.4 million, 21.2 million and 18.4 million for the years ended December 31, 2023, 2022 and 2021, respectively. Comprehensive Loss Comprehensive loss is the change in stockholders’ equity from transactions and other events and circumstances other than those resulting from investments by stockholders and distributions to stockholders. Our comprehensive loss includes our net loss, gains and losses from the foreign currency translation of the assets and liabilities of our foreign subsidiaries, and unrealized gains and losses on investments in available-for-sale securities. Recent Accounting Pronouncements In November 2023, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2023-07, Improvements to Reportable Segment Disclosures, which will require disclosure of incremental segment information on an annual and interim basis for all public entities. The amendments do not change how a public entity identifies its operating segments, aggregates those operating segments, or applies the quantitative thresholds to determine its reportable segments. ASU 2023-07 is effective for annual reporting beginning with the fiscal year ending December 31, 2024, and for interim periods thereafter. We are currently evaluating the incremental disclosures that will be required in the footnotes to our consolidated financial statements. In December 2023, the FASB issued ASU 2023-09, Improvements to Income Tax Disclosures, which will require incremental income tax disclosures on an annual basis for all public entities. The amendments require that public business entities disclose specific categories in the rate reconciliation and provide additional information for reconciling items meeting a quantitative threshold. The amendments also require disclosure of income taxes paid to be disaggregated by jurisdiction, and disclosure of income tax expense disaggregated by federal, state, and foreign. ASU 2023-09 is effective for annual reporting beginning with the fiscal year ending December 31, 2025. We are currently evaluating the incremental disclosures that will be required in our consolidated financial statements.

Liabilities Related to the Sales of Future Royalties - Schedule of Liability Related to Potential Future Royalties (Detail) - USD ($) $ in Thousands	12 Months Ended			36 Months Ended	142 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2023	Dec. 31, 2023
Liability Related To Sale Of Future Royalties [Roll Forward]
Liabilities related to the sales of future royalties—beginning balance	$ 157,461				$ 0
Royalty monetization proceeds	0				274,000
Non-cash royalty revenue	(68,921)	$ (69,794)	$ (77,746)		(472,166)
Non-cash interest expense	25,334	28,911	$ 47,313		298,518
Payments to RPI	0				(10,000)
Loss on revaluation of liability related to the sale of future royalties	0				23,522
Liabilities related to the sales of future royalties – ending balance	113,874	157,461		$ 113,874	113,874
Less: unamortized transaction costs	(1,249)			(1,249)	(1,249)
Liabilities related to the sales of future royalties, net	112,625	155,378		112,625	112,625
2012 Purchase and Sale Agreement
Liability Related To Sale Of Future Royalties [Roll Forward]
Liabilities related to the sales of future royalties—beginning balance	55,167				0
Royalty monetization proceeds	0				124,000
Non-cash royalty revenue	(37,323)				(353,847)
Non-cash interest expense	6,373				240,542
Payments to RPI	0				(10,000)
Loss on revaluation of liability related to the sale of future royalties	0				23,522
Liabilities related to the sales of future royalties – ending balance	24,217	55,167		24,217	24,217
Less: unamortized transaction costs	0			0	0
Liabilities related to the sales of future royalties, net	24,217			24,217	24,217
2020 Purchase and Sale Agreement
Liability Related To Sale Of Future Royalties [Roll Forward]
Liabilities related to the sales of future royalties—beginning balance	102,294			0
Royalty monetization proceeds	0			150,000
Non-cash royalty revenue	(31,598)			(118,319)
Non-cash interest expense	18,961			57,976
Payments to RPI	0			0
Loss on revaluation of liability related to the sale of future royalties	0			0
Liabilities related to the sales of future royalties – ending balance	89,657	$ 102,294		89,657	89,657
Less: unamortized transaction costs	(1,249)			(1,249)	(1,249)
Liabilities related to the sales of future royalties, net	$ 88,408			$ 88,408	$ 88,408

Cash and Investments in Marketable Securities - Cash and Investments in Marketable Securities, Including Cash Equivalents (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Estimated Fair Value at
Cash and cash equivalents	$ 35,277	$ 88,227
Short-term investments	268,339	416,750
Long-term investments	25,825	0
Total cash and investments in marketable securities	$ 329,441	$ 504,977

Income Taxes - Schedule of Income Tax Provision Related to Continuing Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Income tax benefit at federal statutory rate	$ (58,013)	$ (76,647)	$ (109,889)
Research credits	(1,192)	(987)	(4,727)
Change in valuation allowance	35,033	51,108	97,914
Expiration of net operating loss carryforwards	312	12,348	286
Stock-based compensation	8,919	15,778	6,627
Non-cash interest expense on liability related to sales of future royalties	5,320	6,071	9,936
Non-cash royalty revenue related to sales of future royalties	(7,838)	(7,112)	(7,891)
Loss on revaluation of liability related to the sale of future royalties	0	0	4,940
Impairment of goodwill	16,065	0	0
Other	1,194	2,656	3,361
Provision (benefit) for income taxes	$ (200)	$ 3,215	$ 557

Cash and Investments in Marketable Securities

12 Months Ended

Dec. 31, 2023

Fair Value Disclosures [Abstract]

Cash and Investments in Marketable Securities

Note 2 — Cash and Investments in Marketable Securities

Cash and investments in marketable securities, including cash equivalents, are as follows (in thousands):


	Estimated Fair Value at
	December 31,		December 31,
	2023		2022
Cash and cash equivalents	$	35,277	$	88,227
Short-term investments		268,339		416,750
Long-term investments		25,825		—
Total cash and investments in marketable securities	$	329,441	$	504,977

We invest in liquid, high quality debt securities. Our investments in debt securities are subject to interest rate risk. To minimize the exposure due to an adverse shift in interest rates, we invest in securities with maturities of two years or less and maintain a weighted average maturity of one year or less. All of our long-term investments as of December 31, 2023 had maturities between one and two years.

During the years ended December 31, 2023 and 2022, we did not sell any available-for-sale securities. During the year ended December 31, 2021, we sold available-for-sale securities totaling $11.5 million. Gross realized gains and losses on those sales were not significant.

We report our accrued interest receivable, which totaled $0.5 million and $0.7 million at December 31, 2023 and December 31, 2022, respectively, in other current assets on our Consolidated Balance Sheets.

Our portfolio of cash and investments in marketable securities includes (in thousands):


				December 31, 2023							December 31, 2022
	Fair Value Hierarchy			Gross Unrealized		Gross Unrealized
	Level	Amortized Cost		Gains		Losses			Fair Value		Fair Value
Corporate notes and bonds	2	$	38,799	$	85	$	(2	)	$	38,882	$	83,522
Corporate commercial paper	2		255,274		47		(80	)		255,241		344,204
Available-for-sale investments			294,073		132		(82	)		294,123		427,726
Money market funds	1									2,359		47,054
Certificates of deposit	2									15,116		21,399
Cash	N/A									17,843		8,798
Total cash and investments in marketable securities									$	329,441	$	504,977

At December 31, 2022, our gross unrealized losses totaled $1.8 million. Our gross unrealized gains were not significant. As of December 31, 2023 and 2022, we assessed our marketable securities with unrealized losses and concluded that the losses were not attributable to credit. Accordingly, we have not recorded an allowance for credit losses for these securities.

At both December 31, 2023 and 2022, we had letter of credit arrangements in favor of our landlords and certain vendors totaling $7.5 million and $7.5 million, respectively. These letters of credit are secured by investments of similar amounts.

Operating Leases

12 Months Ended

Dec. 31, 2023

Leases [Abstract]

Operating Leases

Note 4 — Operating Leases

Our leases consist of a Lease Agreement (the Mission Bay Lease) with ARE-San Francisco No. 19, LLC (ARE) for our 155,215 square foot corporate office and R&D facility located at 455 Mission Bay Boulevard South, San Francisco, California (the Mission Bay Facility) and a Lease Agreement (the Third Street Lease) with Kilroy Realty Finance Partnership, L.P. (Kilroy) for an additional 135,936 square foot of office space at 360 Third Street, San Francisco, California (the Third Street Facility). Both leases terminate in January 31, 2030, subject to two consecutive five year renewals for the Mission Bay Facility and one five year renewal for the Third Street Facility.

•

The monthly base rent for both facilities will escalate over the term of the lease at various intervals.

•

Both leases include various covenants, indemnities, defaults, termination rights, security deposits and other provisions customary for lease transactions of this nature.

•

During the term of the Mission Bay Lease, we are responsible for paying our share of operating expenses specified in the lease, including utilities, common area maintenance, insurance costs and taxes.

•

For the Third Street Lease, our fixed annual base rent on an industrial gross lease basis includes certain expenses and property taxes paid directly by the landlord.

Due to our 2022 and 2023 Restructuring Plans, during the year ended December 31, 2023, we recorded impairment charges of $30.6 million for our right-of-use assets which we are seeking to sublease. See Note 8 for additional information.

We generally recognize lease expense for our operating leases on a straight-line basis over the lease term. For spaces where we have recognized an impairment charge, the aggregate lease expense recognized over the remaining term is reduced by the amount of the impairment charge, but we recognize the remaining lease expense on an accelerated basis. The

components of lease expense, which we include in operating expenses in our Consolidated Statements of Operations, were as follows (in thousands):


	Year Ended December 31,
	2023		2022		2021
Operating lease expense	$	12,116	$	17,057	$	19,153
Variable lease expense		7,027		10,700		8,974
Total lease expense	$	19,143	$	27,757	$	28,127

During the years ended December 31, 2023, 2022 and 2021, we paid $21.0 million, $20.1 million and $16.8 million, respectively, of operating lease payments related to our lease liabilities, which we include in net cash used in operating activities in our Consolidated Statements of Cash Flows.

As of December 31, 2023, the maturities of our operating lease liabilities were as follows (in thousands):


Year ending December 31,
2024	$	19,822
2025		22,255
2026		22,958
2027		23,682
2028		24,427
2029 and thereafter		27,303
Total lease payments		140,447
Less: portion representing interest		(22,671	)
Operating lease liabilities		117,776
Less: current portion		(19,259	)
Operating lease liabilities, less current portion	$	98,517

As of December 31, 2023, the weighted-average remaining lease term is 6.1 years and the weighted-average discount rate was 5.8%.

We have entered into subleases for approximately 29,000 square feet of space in our Mission Bay Facility that would provide recovery of $10.5 million in aggregate fixed lease payments, as well as full recovery of the subtenants' share of operating expenses under our master lease agreement, subject to certain free rent periods. We record the total sublease income as a reduction of general and administrative expense, which totaled $2.2 million for the year ended December 31, 2023.

As of December 31, 2023, maturities of our operating lease receivables from subleases for each of the next five years and thereafter were as follows:


Year ending December 31,
2024	$	1,360
2025		1,535
2026		1,589
2027		1,645
2028		1,702
2029 and thereafter		1,757
Gross Lease Receivable	$	9,588

Liabilities Related to the Sales of Future Royalties (Tables)

12 Months Ended

Dec. 31, 2023

Schedule of Liability Related to Potential Future Royalties

The following table shows the activity within the liability account of each arrangement (in thousands):


	Year-Ended December 31, 2023									Period from inception to December 31, 2023
	2012 Purchase and Sale Agreement			2020 Purchase and Sale Agreement			Total			2012 Purchase and Sale Agreement			2020 Purchase and Sale Agreement			Total
Liabilities related to the sales of future royalties—beginning balance	$	55,167		$	102,294		$	157,461		$	—		$	—		$	—
Royalty monetization proceeds		—			—			—			124,000			150,000			274,000
Non-cash royalty revenue		(37,323	)		(31,598	)		(68,921	)		(353,847	)		(118,319	)		(472,166	)
Non-cash interest expense		6,373			18,961			25,334			240,542			57,976			298,518
Payments to RPI		—			—			—			(10,000	)		—			(10,000	)
Loss on revaluation of liability related to the sale of future royalties		—			—			—			23,522			—			23,522
Liabilities related to the sales of future royalties – ending balance		24,217			89,657			113,874			24,217			89,657			113,874
Less: unamortized transaction costs		—			(1,249	)		(1,249	)		—			(1,249	)		(1,249	)
Liabilities related to the sales of future royalties, net	$	24,217		$	88,408		$	112,625		$	24,217		$	88,408		$	112,625

Organization and Summary of Significant Accounting Policies (Details) - USD ($) shares in Millions	1 Months Ended		12 Months Ended
	Jun. 30, 2023	Apr. 30, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Organization And Summary Of Significant Accounting Policies [Line Items]
Cash and investments in marketable securities			$ 329,441,000	$ 504,977,000
Total revenue			90,122,000	$ 92,055,000	$ 101,907,000
Accounts receivable, credit loss expense (reversal)			$ 0
Employee Severance \| 2022 Restructuring Plan
Organization And Summary Of Significant Accounting Policies [Line Items]
Workforce termination, percentage		70.00%
Employee Severance \| 2023 Restructuring Plan
Organization And Summary Of Significant Accounting Policies [Line Items]
Workforce termination, percentage	60.00%
Stock Options, RSUs and PSUs
Organization And Summary Of Significant Accounting Policies [Line Items]
Weighted average antidilutive securities excluded from computation of earnings per share (in shares)			20.4	21.2	18.4
Cash And NonCash Royalties
Organization And Summary Of Significant Accounting Policies [Line Items]
Total revenue			$ 68,900,000	$ 69,800,000	$ 77,700,000
Buildings
Organization And Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful lives			20 years
Minimum \| Manufacturing equipment
Organization And Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful lives			3 years
Maximum \| Manufacturing equipment
Organization And Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful lives			10 years

Segment Reporting - Additional Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($) Segment	Dec. 31, 2022 USD ($)	Dec. 31, 2020
Segment Reporting Information [Line Items]
Number of operating business segment \| Segment	1
Property, plant and equipment, net \| $	$ 18,856	$ 32,451
Revenue \| UCB \| Customer Concentration Risk
Segment Reporting Information [Line Items]
Percentage revenue from customers	40.00%	37.00%	23.00%
Revenue \| Baxalta Incorporated Or Takeda P L C \| Customer Concentration Risk
Segment Reporting Information [Line Items]
Percentage revenue from customers	21.00%	25.00%	16.00%
Revenue \| Astra Zeneca Ab \| Customer Concentration Risk
Segment Reporting Information [Line Items]
Percentage revenue from customers	11.00%	14.00%	13.00%
Revenue \| Pfizer \| Customer Concentration Risk
Segment Reporting Information [Line Items]
Percentage revenue from customers	10.00%	11.00%
Revenue \| BMS \| Customer Concentration Risk
Segment Reporting Information [Line Items]
Percentage revenue from customers			36.00%

Consolidated Financial Statement Details - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended			12 Months Ended
	Dec. 31, 2023	Sep. 30, 2023	Mar. 31, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Goodwill [Line Items]
Provision for inventory obsolescence				$ 2,402	$ 0	$ 0
Impairment of other property, plant and equipment				35,328	65,761	0
Impairment of goodwill			$ 76,500	76,501	0	0
Depreciation and amortization expenses				7,000	$ 12,200	$ 13,000
Huntsville, Alabama Manufacturing Facility
Goodwill [Line Items]
Provision for inventory obsolescence		$ 3,700
Provision for inventory obsolescence reversed	$ 3,700
UCB Pharma Manufacturing Agreement
Goodwill [Line Items]
Provision for inventory obsolescence				2,000
Sublease of Laboratory and Office Space
Goodwill [Line Items]
Impairment of other property, plant and equipment				$ 4,800

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-1

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 24
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482548/350-20-55-24

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-1

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-1

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-1

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-1

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-1

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1A
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-1A

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-2

+ Details

Stock-Based Compensation

12 Months Ended

Dec. 31, 2023

Share-Based Payment Arrangement [Abstract]

Stock-Based Compensation

Note 10 — Stock-Based Compensation

2017 Performance Incentive Plan

Our 2017 Performance Incentive Plan (2017 Plan) provides for the issuance of our common stock to members of the Board of Directors, officers or employees, certain consultants and advisors and our subsidiaries. Our 2017 Plan has been amended and restated such that an aggregate 51,200,000 shares have been authorized for issuance as of December 31, 2023, including 12,000,000 shares that were approved on June 8, 2023. Under the 2017 Plan, we may issue stock options, restricted stock, performance stock, stock units, stock appreciation rights and other similar types of awards. When the 2017 Plan was approved on June 14, 2017, any shares of our common stock that were available for issuance under our 2012 Performance Incentive Plan (the 2012 Plan) ceased to be available for future grants. However, options and RSUs granted under the 2012 Plan remained outstanding, and any options or RSUs that were cancelled or forfeited became available for issuance under the 2017 Plan. Shares issued for RSUs, PSUs or any other “full-value award” are counted against the share limit as 1.5 shares for every one share granted in connection with the award.

We have granted non-qualified stock options, RSUs and PSUs to employees, officers, and non-employee directors. For our employees, the requisite service period is generally three to four years for stock options, and three years for RSUs and PSUs. For our directors, the requisite service is generally one year for stock options and RSUs. The maximum term of a stock option is eight years from the date of grant. The per share exercise price of an option generally may not be less than the fair market value of a share of our common stock on the NASDAQ Stock Market on the date of grant.

Under our Change in Control Plan (the CIC Plan), in the event of a change of control of Nektar and a subsequent termination of employment initiated by us or a successor company other than for Cause (as defined in the CIC Plan) within twelve months following a change of control, our employees are entitled to full acceleration of their unvested equity awards. Our Chief Executive Officer, Senior Vice Presidents and Vice Presidents (including Principal Fellows) are also entitled to full acceleration of unvested equity awards if the termination is initiated by the employee for a Good Reason Resignation (as defined in the CIC Plan) within twelve months following a change of control. Additionally, non-employee directors would also be entitled to full acceleration of vesting of all outstanding stock awards in the event of a change of control transaction.

Employee Stock Purchase Plan

Under the terms of our Employee Stock Purchase Plan (ESPP), employees may purchase shares of our common stock based on a percentage of their compensation subject to certain limits. Shares are purchased at 85% of the lower of the closing price on either the first day or last day of each six-month offering period. An aggregate 3,500,000 shares have been authorized for issuance under our ESPP.

Shares Reserve for Issuance

As of December 31, 2023, shares of common stock reserved for future issuance are as follows (in thousands):


Stock options, RSUs and PSUs outstanding			27,246
Shares available for future grant under the 2017 Performance Incentive Plan			10,101
Shares available for issuance under the employee stock purchase plan			775
Total common stock reserved for issuance			38,122

Stock-Based Compensation Expense

We recognize total stock-based compensation expense in our Consolidated Statements of Operations as follows (in thousands):


	Year Ended December 31,
	2023		2022		2021
Cost of goods sold	$	3,177	$	2,824	$	2,779
Research and development		13,890		27,727		54,821
General and administrative		16,321		24,488		37,074
Restructuring, impairment and costs of terminated program		—		2,281		—
Total stock-based compensation	$	33,388	$	57,320	$	94,674

Stock-based compensation expense resulting from PSUs and our ESPP was not significant in the years ended December 31, 2023, 2022, and 2021.

As of December 31, 2023, total unrecognized compensation costs of $33.1 million related to unvested stock-based compensation awards are expected to be recognized as expense over a weighted-average period of 2.3 years.

Black-Scholes Assumptions

The following table lists the Black-Scholes option-pricing model assumptions used to calculate the fair value of employee and director stock options, as well as the resulting grant-date fair value:


	Year Ended December 31,
	2023			2022			2021
Average risk-free interest rate		4.0	%		2.9	%		1.2	%
Dividend yield		0.0	%		0.0	%		0.0	%
Average volatility factor		88.4	%		77.9	%		63.8	%
Weighted-average expected life	5.1 years			5.6 years			5.5 years
Weighted-average grant-date fair value of options granted	$	0.37		$	3.18		$	8.07

The average risk-free interest rate is based on the U.S. treasury yield curve in effect at the time of grant for periods commensurate with the expected life of the stock-based award. We have never paid dividends, nor do we expect to pay dividends in the foreseeable future; therefore, we used a dividend yield of zero. Our estimate of expected volatility is based on the daily historical trading data of our common stock at the time of grant over a historical period commensurate with the expected life of the stock-based award. We estimated the weighted-average expected life based on the contractual and vesting terms of the stock options, as well as historical cancellation and exercise data.

Summary of Stock Option Activity

The table below presents a summary of stock option activity under our equity incentive plans (in thousands, except for price per share and contractual life information):


						Weighted-
				Weighted-		Average
				Average		Remaining
	Number			Exercise		Contractual		Aggregate
	of			Price		Life		Intrinsic
	Shares			per Share		(in Years)		Value(1)
Outstanding at December 31, 2022		14,088		$	16.40
Options granted		11,854			0.51
Options exercised		—			—
Options forfeited & canceled		(2,926	)		16.07
Outstanding at December 31, 2023		23,016		$	8.26		6.42	$	—

Exercisable at December 31, 2023		6,425			22.99		3.68	$	—

(1)

Aggregate intrinsic value represents the difference between the exercise price of the option and the closing market price of our common stock on December 31, 2023.

The intrinsic value of options exercised during the years ended December 31, 2022 and 2023 was not significant and totaled $17.3 million during the year ended December 31, 2021.

Summary of RSU Activity

A summary of RSU award activity is as follows (in thousands except for per share amounts):


				Weighted-
				Average
				Grant
				Date Fair
	Units Issued			Value
Unvested at December 31, 2022		9,312		$	6.81
Granted		126			1.10
Vested and released		(2,759	)		7.93
Forfeited and canceled		(2,449	)		6.11
Unvested at December 31, 2023		4,230		$	6.14

The weighted-average grant-date fair values of RSUs granted during the years ended December 31, 2023, 2022 and 2021 were $1.10, $4.14 and $14.68, respectively. The fair value of RSU's that vested in the years ended December 31, 2023, 2022 and 2021 totaled $3.6 million, $17.5 million and $45.3 million, respectively.

401(k) Retirement Plan

We sponsor a 401(k) retirement plan whereby eligible employees may elect to contribute up to the lesser of 60% of their annual compensation or the statutorily prescribed annual limit allowable under Internal Revenue Service regulations. The 401(k) plan permits us to make matching contributions on behalf of all participants, up to a maximum of $12,000 per participant for the years ended December 31, 2022 and 2023, and up to a maximum of $6,000 per participant for the year ended December 31, 2021. For the years ended December 31, 2023, 2022, and 2021, we recognized $1.5 million, $2.5 million and $3.6 million, respectively, of compensation expense in connection with our 401(k) retirement plan.

Consolidated Financial Statement Details - Schedule of Accumulated Other Comprehensive Income (Loss) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	$ 366,638
Ending balance	130,987
Accumulated Other Comprehensive Loss
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(6,907)
Ending balance	80
Foreign currency translation
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(5,131)
Adjustments	62
Reclassification adjustments to income	5,099
Ending balance	30
Available-for-sale securities
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(1,776)
Adjustments	1,826
Ending balance	$ 50

- Definition

Amount of equity (deficit) attributable to parent. Excludes temporary equity and equity attributable to noncontrolling interest.

+ References

+ Details

Restructuring, Impairment and Costs of Terminated Program - Non-cash Impairment Charges Pertaining 2022 and 2023 Restructuring Plan (Details) - USD ($) $ in Thousands	3 Months Ended							12 Months Ended		21 Months Ended
	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2023
Restructuring Cost and Reserve [Line Items]
Total impairment of lease assets								$ (36,962)	$ (67,875)
2022 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Total impairment of lease assets	$ 0	$ 1,467	$ 13,261	$ 0	$ 12,361	$ 1,200	$ 52,200			$ 80,489
2022 and 2023 Restructuring Plans
Restructuring Cost and Reserve [Line Items]
Total impairment of lease assets	0	(10,567)	(13,261)	(11,500)	(12,361)	(1,200)	(52,200)			(101,089)
Mission Bay Blvd. South \| 2022 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Total impairment of lease assets	0	1,467	7,061	0	361	1,200	3,000			13,089
Mission Bay Blvd. South \| 2023 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Total impairment of lease assets	0	9,100	0	11,500						20,600
Third St \| 2022 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Total impairment of lease assets	$ 0	$ 0	$ 6,200	$ 0	$ 12,000	$ 0	$ 49,200			$ 67,400

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References + Details

Income Taxes - Schedule of Significant Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets:
Net operating loss carryforwards	$ 574,737	$ 545,508
Research and other credits	144,128	142,198
Net capital loss carryforwards	39,655	38,445
Operating lease liabilities	25,384	28,254
Stock-based compensation	19,447	22,110
Capitalized research and development costs	34,675	24,134
Liability related to the sale of future royalties	6,729	13,424
Other	13,863	13,935
Deferred tax assets before valuation allowance	858,618	828,008
Valuation allowance for deferred tax assets	(854,528)	(816,235)
Total deferred tax assets	4,090	11,773
Deferred tax liabilities:
Operating lease right-of-use assets	(3,824)	(11,335)
Investment in foreign subsidiary	(521)	(2,451)
Other	(265)	(392)
Total deferred tax liabilities	(4,610)	(14,178)
Total deferred tax liabilities	$ (520)	$ (2,405)

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 35,277	$ 88,227
Short-term investments	268,339	416,750
Accounts receivable	1,205	5,981
Inventory	16,101	19,202
Other current assets	9,779	15,808
Total current assets	330,701	545,968
Long-term investments	25,825	0
Property, plant and equipment, net	18,856	32,451
Operating lease right-of-use assets	18,007	53,435
Goodwill	0	76,501
Other assets	4,644	2,245
Total assets	398,033	710,600
Current liabilities:
Accounts payable	9,848	12,980
Accrued expenses	22,162	36,557
Operating lease liabilities, current portion	19,259	18,667
Total current liabilities	51,269	68,204
Operating lease liabilities, less current portion	98,517	112,829
Liabilities related to the sales of future royalties, net	112,625	155,378
Other long-term liabilities	4,635	7,551
Total liabilities	267,046	343,962
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $0.0001 par value; 10,000 shares authorized; no shares designated, issued or outstanding at December 31, 2023 or 2022	0	0
Common stock, $0.0001 par value; 300,000 shares authorized; 191,384 shares and 188,560 shares issued and outstanding at December 31, 2023 and 2022, respectively	19	19
Capital in excess of par value	3,608,137	3,574,719
Accumulated other comprehensive income (loss)	80	(6,907)
Accumulated deficit	(3,477,249)	(3,201,193)
Total stockholders’ equity	130,987	366,638
Total liabilities and stockholders’ equity	$ 398,033	$ 710,600

Income Taxes

12 Months Ended

Dec. 31, 2023

Income Tax Disclosure [Abstract]

Income Taxes

Note 11 — Income Taxes

Loss before provision for income taxes includes the following components (in thousands):


	Year Ended December 31,
	2023			2022			2021
Domestic	$	(274,998	)	$	(371,900	)	$	(524,440	)
Foreign		(1,258	)		6,917			1,160
Loss before provision for income taxes	$	(276,256	)	$	(364,983	)	$	(523,280	)

Provision for Income Taxes

The provision for income taxes consists of the following (in thousands):


	Year Ended December 31,
	2023			2022			2021
Current:
Federal	$	—		$	—		$	—
State		(43	)		(608	)		50
Foreign		(17	)		1,115			609
Total current income tax expense		(60	)		507			659
Deferred:
Federal		—			—			—
State		—			—			—
Foreign		(140	)		2,708			(102	)
Total deferred income tax expense		(140	)		2,708			(102	)
Provision (benefit) for income taxes	$	(200	)	$	3,215		$	557

Our income tax provision related to continuing operations differs from the amount computed by applying the statutory income tax rate of 21% to our pretax loss as follows (in thousands):


	Year Ended December 31,
	2023			2022			2021
Income tax benefit at federal statutory rate	$	(58,013	)	$	(76,647	)	$	(109,889	)
Research credits		(1,192	)		(987	)		(4,727	)
Change in valuation allowance		35,033			51,108			97,914
Expiration of net operating loss carryforwards		312			12,348			286
Stock-based compensation		8,919			15,778			6,627
Non-cash interest expense on liability related to sales of future royalties		5,320			6,071			9,936
Non-cash royalty revenue related to sales of future royalties		(7,838	)		(7,112	)		(7,891	)
Loss on revaluation of liability related to the sale of future royalties		—			—			4,940
Impairment of goodwill		16,065			—			—
Other		1,194			2,656			3,361
Provision (benefit) for income taxes	$	(200	)	$	3,215		$	557

Deferred Tax Assets and Liabilities

Deferred income taxes reflect the net tax effects of loss and credit carryforwards and temporary differences between the carrying amount of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. We measure deferred tax assets and liabilities based on the rates at which they are expected to reverse in the future. Significant components of our deferred tax assets for federal and state income taxes are as follows (in thousands):


	December 31,
	2023			2022
Deferred tax assets:
Net operating loss carryforwards	$	574,737		$	545,508
Research and other credits		144,128			142,198
Net capital loss carryforwards		39,655			38,445
Operating lease liabilities		25,384			28,254
Stock-based compensation		19,447			22,110
Capitalized research and development costs		34,675			24,134
Liability related to the sale of future royalties		6,729			13,424
Other		13,863			13,935
Deferred tax assets before valuation allowance		858,618			828,008
Valuation allowance for deferred tax assets		(854,528	)		(816,235	)
Total deferred tax assets		4,090			11,773
Deferred tax liabilities:
Operating lease right-of-use assets		(3,824	)		(11,335	)
Investment in foreign subsidiary		(521	)		(2,451	)
Other		(265	)		(392	)
Total deferred tax liabilities		(4,610	)		(14,178	)
Net deferred tax assets (liabilities)	$	(520	)	$	(2,405	)

Realization of our deferred tax assets is dependent upon future earnings, if any, the timing and amount of which are uncertain. Because of our lack of U.S. earnings history and projected future losses, we have fully reserved our net U.S. deferred tax assets with a valuation allowance. The valuation allowance increased by $38.3 million for the year ended December 31, 2023 and increased by $30.5 million for the year ended December 31, 2022.

Our net deferred tax liability position reflects the provision for the withholding taxes associated with the repatriation of accumulated earnings and profits from India.

Net Operating Loss and Tax Credit Carryforwards

As of December 31, 2023, we had a net operating loss carryforward for federal income tax purposes of approximately $2.7 billion, of which $1.3 billion is subject to expiration beginning in 2024 and a total state net operating loss carryforward of approximately $0.7 billion, portions of which will begin to expire in 2027. We have federal tax credits of approximately $126.0 million, which will begin to expire in 2024 and state research credits of approximately $59.9 million which have no expiration date. Utilization of some of the federal and state net operating loss and credit carryforwards are subject to annual limitations due to the “change in ownership” provisions of the Internal Revenue Code of 1986 and similar state provisions.

Unrecognized tax benefits

We have the following activity relating to unrecognized tax benefits (in thousands):


	Year Ended December 31,
	2023			2022			2021
Beginning balance	$	85,845		$	80,604		$	78,665
Tax positions related to current year:
Additions		848			378			2,371
Reductions		—			—			—
Tax positions related to prior years:
Additions		40,079			5,272			58
Reductions		—			—			(490	)
Settlements		—			—			—
Lapses in statute of limitations		(274	)		(409	)		—
Ending balance	$	126,498		$	85,845		$	80,604

If we are eventually able to recognize our uncertain tax positions, our effective tax rate may be reduced. We currently have a full valuation allowance against our U.S. net deferred tax asset which would impact the timing of the effective tax rate benefit should any of these uncertain tax positions be favorably settled in the future. Adjustments to the substantial majority of our uncertain tax positions would result in an adjustment of our net operating loss or tax credit carryforwards rather than resulting in a cash outlay.

We file income tax returns in the U.S., California, Alabama, certain other states and India. As a result of our net operating loss and research credit carryforwards, substantially all of our domestic tax years remain open and subject to examination. We may be subject to examination in India from time to time, but we do not believe that any liability resulting from such an examination would have a material effect on our financial position or results of operations.

Our policy is to include interest and penalties related to unrecognized tax benefits, if any, within the provision for income taxes in the consolidated statements of operations. During the years ended December 31, 2023, 2022 and 2021, no significant interest or penalties were recognized relating to unrecognized tax benefits. Although it is reasonably possible that certain unrecognized tax benefits could change in the future, we do not anticipate any significant changes over the next twelve months.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480990/946-20-50-13

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h)(2))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org//740/tableOfContent

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-14

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-21

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 270
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482526/740-270-50-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 17
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-17

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I.5.Q1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479360/740-10-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 11.C)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479360/740-10-S99-2

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482603/740-30-50-2

+ Details

Subsequent Events - Additional Information (Details) - Securities Purchase Agreement - TCG Crossover Fund II, L.P. - Subsequent Event $ / shares in Units, $ in Millions	Mar. 04, 2024 USD ($) $ / shares shares
Subsequent Event [Line Items]
Aggregate common shares issued to purchase prefunded warrants \| shares	25,000,000
Stock price per share \| $ / shares	$ 1.2
Gross proceeds \| $	$ 30.0

Stock-Based Compensation - Schedule of Common Stock Reserved for Future Issuance (Details) - shares shares in Thousands	Dec. 31, 2023	Dec. 31, 2022
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Stock options outstanding	23,016	14,088
Total common stock reserved for issuance	38,122
RSUs and PSUs
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Stock options outstanding	27,246
2017 Performance Incentive Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Shares available for future issuance	10,101
Employee Stock Purchase Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Shares available for future issuance	775

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 35
-Paragraph 1D
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480483/718-10-35-1D

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 35
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480483/718-10-35-3

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)(3)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(i)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(ii)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iii)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(01)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(02)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(03)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(04)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(i)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(ii)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(01)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(02)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(03)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (e)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (e)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 24: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(i)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 25: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(ii)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 26: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(iii)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 27: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(iv)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 28: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(v)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

+ Details

Co-Development Agreement with SFJ Pharmaceuticals and Development Derivative Liability (Tables)

12 Months Ended

Dec. 31, 2023

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Schedule of Derivative Liabilities at Fair Value

The following table presents the change in the derivative liability for the years ended December 31, 2022 and 2021:


		Year Ended December 31,
	Fair Value Hierarchy Level	2022			2021
Fair value as of December 31, 2021 and February 12, 2021 (inception), respectively	3	$	27,726		$	—
Non-cash research and development expense			4,951			16,703
Cash receipts from SFJ			750			3,000
Change in the fair value of development derivative liability			(33,427	)		8,023
Fair value at end of period	3	$	—		$	27,726

CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common Shares	Capital in Excess of Par Value	Accumulated Other Comprehensive Loss	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2020		180,091
Beginning balance at Dec. 31, 2020	$ 1,077,295	$ 18	$ 3,388,730	$ (2,295)	$ (2,309,158)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under equity compensation plans (in shares)		5,377
Shares issued under equity compensation plans	33,238	$ 1	33,237
Stock-based compensation	94,674		94,674
Comprehensive loss	(525,699)			(1,862)	(523,837)
Ending balance (in shares) at Dec. 31, 2021		185,468
Ending balance at Dec. 31, 2021	679,508	$ 19	3,516,641	(4,157)	(2,832,995)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under equity compensation plans (in shares)		3,092
Shares issued under equity compensation plans	758		758
Stock-based compensation	57,320		57,320
Comprehensive loss	$ (370,948)			(2,750)	(368,198)
Ending balance (in shares) at Dec. 31, 2022	188,560	188,560
Ending balance at Dec. 31, 2022	$ 366,638	$ 19	3,574,719	(6,907)	(3,201,193)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under equity compensation plans (in shares)		2,824
Shares issued under equity compensation plans	30		30
Stock-based compensation	33,388		33,388
Comprehensive loss	$ (269,069)			6,987	(276,056)
Ending balance (in shares) at Dec. 31, 2023	191,384	191,384
Ending balance at Dec. 31, 2023	$ 130,987	$ 19	$ 3,608,137	$ 80	$ (3,477,249)

- Definition

Amount of equity (deficit) attributable to parent. Excludes temporary equity and equity attributable to noncontrolling interest.

+ References

+ Details

Stock-Based Compensation - Schedule of Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	$ 33,388	$ 57,320	$ 94,674
Cost of goods sold
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	3,177	2,824	2,779
Research and development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	13,890	27,727	54,821
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	16,321	24,488	37,074
Restructuring, impairment and costs of terminated program
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	$ 0	$ 2,281	$ 0

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Revenue:
Total revenue	$ 90,122	$ 92,055	$ 101,907
Operating costs and expenses:
Cost of goods sold	33,768	21,635	24,897
Research and development	114,162	218,323	400,269
General and administrative	77,417	92,333	122,844
Restructuring, impairment and costs of terminated program	51,958	135,930	0
Impairment of goodwill	76,501	0	0
Total operating costs and expenses	353,806	468,221	548,010
Loss from operations	(263,684)	(376,166)	(446,103)
Non-operating income (expense):
Change in fair value of development derivative liability	0	33,427	(8,023)
Non-cash interest expense on liabilities related to the sales of future royalties	(25,334)	(28,911)	(47,313)
Loss on revaluation of liability related to the sale of future royalties	0	0	(24,410)
Interest income	19,009	6,783	2,731
Other income (expense), net	(6,247)	(116)	(162)
Total non-operating income (expense), net	(12,572)	11,183	(77,177)
Loss before provision for income taxes	(276,256)	(364,983)	(523,280)
Provision (benefit) for income taxes	(200)	3,215	557
Net loss	$ (276,056)	$ (368,198)	$ (523,837)
Basic net loss per share (in dollars per share)	$ (1.45)	$ (1.97)	$ (2.86)
Diluted net loss per share (in dollars per share)	$ (1.45)	$ (1.97)	$ (2.86)
Weighted average shares outstanding used in computing basic net loss per share (in shares)	190,001	187,138	183,298
Weighted average shares outstanding used in computing diluted net loss per share (in shares)	190,001	187,138	183,298
Product sales
Revenue:
Total revenue	$ 20,681	$ 20,348	$ 23,725
Non-cash royalty revenue related to the sales of future royalties
Revenue:
Total revenue	68,921	69,794	77,746
License, collaboration and other revenue
Revenue:
Total revenue	$ 520	$ 1,913	$ 436

Cash and Investments in Marketable Securities - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Target maturity period	2 years
Weighted average maturity period	1 year
Sales of investments	$ 0	$ 0	$ 11,504
Accrued interest receivable	500	700
Gross unrealized gains	132
Gross unrealized losses	82	1,800
Letter of credit	$ 7,500	$ 7,500
Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long term investment maturity period	1 year
Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long term investment maturity period	2 years

Organization and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization	Organization We are a clinical stage, research-based drug discovery biopharmaceutical company headquartered in San Francisco, California and incorporated in Delaware, focused on discovering and developing innovative medicines in the field of immunotherapy. Within this growing field, we direct our efforts toward creating new immunomodulatory agents that selectively induce, amplify, attenuate or prevent immune responses in order to achieve desired therapeutic outcomes. Our pipeline of clinical-stage and preclinical-stage immunomodulatory agents targets the treatment of autoimmune diseases (e.g. rezpegaldesleukin and NKTR-0165, respectively) and cancer (e.g. NKTR-255). Our research and development activities have required significant ongoing investment to date and are expected to continue to require significant investment. As a result, we expect to continue to incur substantial losses and negative cash flows from operations in the future. We have financed our operations primarily through cash generated from licensing, collaboration and manufacturing agreements and financing transactions. At December 31, 2023, we had approximately $329.4 million in cash and investments in marketable securities.
Results of Clinical Trial Programs and Restructuring Plans	Results of Clinical Trial Programs and Restructuring Plans In March and April 2022, we announced that our registrational trials of bempegaldesleukin in combination with Opdivo® in metastatic melanoma, renal cell carcinoma and locally advanced or metastatic urothelial cancer under our Strategic Collaboration Agreement (BMS Collaboration Agreement) with Bristol-Myers Squibb Company (BMS) did not meet their primary endpoints. Based on these results, in April 2022, we announced our decisions to discontinue all development of bempegaldesleukin in combination with checkpoint inhibitors, including these trials, our registrational trial in adjuvant melanoma under our BMS Collaboration Agreement, and our Phase 2/3 study of bempegaldesleukin in combination with Keytruda® in squamous cell cancer of the head and neck under our Co-Development Agreement with SFJ Pharmaceuticals XII, L.P., an SFJ Pharmaceuticals Group company (SFJ). See Note 7 for additional information regarding our BMS Collaboration Agreement and Co-Development Agreement with SFJ. On September 6, 2023, BMS and we terminated the BMS Collaboration Agreement, however, we continue our efforts to wind down the bempegaldesleukin program following the same cost sharing provisions provided for in the BMS Collaboration Agreement. In April 2022, we also announced new strategic reorganization and cost restructuring plans (together, the 2022 Restructuring Plan), pursuant to which we completed an approximate 70% reduction of our workforce during 2022 and sold our research facility in India in December 2022. We also decided to sublease certain of our leased premises in San Francisco, CA, including all of our office leased space on Third St. (the Third Street Facility) and portions of our office and laboratory space on Mission Bay Blvd. South (the Mission Bay Facility). On February 23, 2023, we announced the topline data from the Phase 2 study of rezpegaldesleukin in adult patients with systemic lupus erythematosus (SLE) (Phase 2 Lupus Study) under our collaboration agreement with Eli Lilly and Company (Lilly). Lilly subsequently notified us that it did not intend to advance rezpegaldesleukin into Phase 3 development for SLE. On April 27, 2023, we announced that we would be regaining the full rights to rezpegaldesleukin from Lilly, and the collaboration agreement was subsequently terminated. We have initiated a Phase 2b study of rezpegaldesleukin in patients with moderate-to-severe atopic dermatitis, and we are targeting the initiation of a Phase 2b study of rezpegaldesleukin in patients with alopecia areata by the end of March 2024. We also plan to explore other auto-immune indications for the development of rezpegaldesleukin. Pursuant to plans approved by our Board of Directors (the Board) on March 29, 2023, we announced on April 17, 2023, a new strategic reprioritization and cost restructuring plan (the 2023 Restructuring Plan). Under the 2023 Restructuring Plan, we reduced our San Francisco-based workforce by approximately 60%, which was substantially completed by June 2023. In addition, under the 2023 Restructuring Plan, we decided to sublease our remaining office and laboratory space on Mission Bay Blvd. South which we had not planned to sublease pursuant to the 2022 Restructuring Plan. We have incurred significant costs resulting from the 2022 and 2023 Restructuring Plans. See Note 8 for additional information on the effect of these Plans on our Consolidated Financial Statements.
Basis of Presentation, Principles of Consolidation and Use of Estimates	Basis of Presentation, Principles of Consolidation and Use of Estimates Our Consolidated Financial Statements include the financial position, results of operations and cash flows of our wholly-owned subsidiaries. We have eliminated all intercompany accounts and transactions in consolidation. Our Consolidated Financial Statements are denominated in U.S. dollars. Accordingly, changes in exchange rates between the applicable foreign currency and the U.S. dollar will affect the translation of each foreign subsidiary’s financial results into U.S. dollars for purposes of reporting our consolidated financial results. We include translation gains and losses in accumulated other comprehensive income (loss) in the stockholders’ equity section of our Consolidated Balance Sheets. Our comprehensive loss consists of our net loss plus our foreign currency translation gains and losses and unrealized holding gains and losses on available-for-sale securities. Other than as described in Note 3, there were no significant reclassifications out of accumulated other comprehensive loss to the statements of operations for the periods presented. The preparation of consolidated financial statements in conformity with U.S. generally accepted accounting principles (GAAP) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenue and expenses during the reporting period. Accounting estimates and assumptions are inherently uncertain. Actual results could differ materially from those estimates and assumptions. Our estimates include those related to the selling prices of performance obligations and amounts of variable consideration in collaboration agreements, royalty revenue, and other assumptions required for revenue recognition as described further below; the net realizable value of inventory; the fair value and impairment of investments, goodwill and long-lived assets; contingencies, accrued clinical trial, contract manufacturing and other expenses; income taxes; non-cash royalty revenue and non-cash interest expense from our liabilities related to our sales of future royalties; our assumptions used in stock-based compensation; and ongoing litigation, among other estimates. We base our estimates on historical experience and on other assumptions that management believes are reasonable under the circumstances. These estimates form the basis for making judgments about the carrying values of assets and liabilities when these values are not readily apparent from other sources. As appropriate, we assess estimates each period, update them to reflect current information, and will generally reflect any changes in estimates in the period first identified.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The recorded amounts of certain financial instruments, including cash and cash equivalents, accounts receivable, accounts payable and accrued liabilities approximate their fair values due to their relatively short maturities. We record available-for-sale investments and cash equivalents at their estimated fair values, which are based on market prices from a variety of industry standard data providers and generally represent quoted prices for similar assets in active markets or have been derived from observable market data. As further described in Note 8, we estimated the fair value of our lease assets for recognizing impairment charges based on management’s estimates of several unobservable inputs, including estimated time to enter a sublease, sublease rental rates and free rent periods. The fair value of our financial assets and liabilities are determined in accordance with the fair value hierarchy established in ASC 820-10, Fair Value Measurements and Disclosures (ASC 820). ASC 820 defines fair value as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. The fair value hierarchy of ASC Topic 820 requires an entity to maximize the use of observable inputs when measuring fair value and classifies those inputs into three levels: Level 1 — Quoted prices in active markets for identical assets or liabilities. Level 2 — Inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices for identical or similar assets or liabilities in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. For the years ended December 31, 2023 and 2022, there were no transfers between Level 1 and Level 2 of the fair value hierarchy. Level 3 — Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities.
Cash, Cash Equivalents, and Investments in Marketable Securities	Cash, Cash Equivalents, and Investments in Marketable Securities We consider all investments in marketable securities with an original maturity of three months or less when purchased to be cash equivalents. We classify investments in securities with remaining maturities of less than one year, or where our intent is to use the investments to fund current operations or to make them available for current operations, as short-term investments. We classify investments in securities with remaining maturities of over one year as long-term investments. Our cash and investments are held or issued by financial institutions that management believes are of high credit quality. However, we are exposed to credit risk in the event of default by the third parties that hold or issue such assets. Our investment policy limits investments to fixed income securities denominated and payable in U.S. dollars such as corporate bonds, corporate commercial paper, U.S. government obligations, and money market funds and places restrictions on maturities and concentrations by type and issuer. For our available-for-sale securities, we have significant concentrations of issuers in the banking and financial services industry. While our investment policy requires that we only invest in highly-rated securities and limit our exposure to any single issuer, a variety of factors may materially affect the financial condition of issuers. Additionally, pursuant to our investment policy, we may sell securities before maturity if the issuer’s credit rating has been downgraded below our minimum credit rating requirements, which may result in a loss on the sale. Accordingly, if factors result in downgrades below our minimum credit rating requirements and if we decide to sell these securities, we may experience losses on such sales. Investments are designated as available-for-sale and are carried at fair value with unrealized gains and losses reported in stockholders’ equity as accumulated other comprehensive income (loss). We review our portfolio of available-for-sale debt securities, using both quantitative and qualitative factors, to determine if declines in fair value below amortized cost have resulted from a credit-related loss or other factors. If the decline in fair value is due to credit-related factors, we recognize a loss in our Consolidated Statement of Operations, whereas if the decline in fair value is not due to credit-related factors, we recognize the loss in other comprehensive income (loss). We include coupon interest on securities classified as available-for-sale, as well as amortization of premiums and accretion of discounts to maturity, in interest income. The cost of securities sold is based on the specific identification method.
Accounts Receivable and Significant Customer Concentrations	Accounts Receivable and Significant Customer Concentrations Our customers are primarily pharmaceutical and biotechnology companies that are primarily located in the U.S. and Europe and with whom we have multi-year arrangements. Our accounts receivable balance contains billed and unbilled trade receivables from product sales, milestones (to the extent that they have been achieved and are due from the counterparty), other contingent payments, as well as reimbursable costs from collaborative research and development agreements. We perform a regular review of our partners’ credit risk and payment histories when circumstances warrant, including payments made subsequent to year-end. When appropriate, we provide for an allowance for doubtful accounts by reserving for specifically identified doubtful accounts, although historically we have not experienced credit losses from our accounts receivable. We have not recorded provisions for credit losses for any of the periods presented.
Inventory and Significant Supplier Concentrations	Inventory and Significant Supplier Concentrations We generally manufacture inventory upon receipt of firm purchase orders from our partners, and we may manufacture certain intermediate work-in-process materials and purchase raw materials based on purchase forecasts from our partners. Inventory includes direct materials, direct labor, and manufacturing overhead, and we determine cost on a first-in, first-out basis for raw materials and on a specific identification basis for work-in-process and finished goods. We value inventory at the lower of cost or net realizable value, and we write down defective or excess inventory to net realizable value based on historical experience or projected usage. We expense inventory related to our research and development activities when we purchase or manufacture it. We are dependent on our suppliers and contract manufacturers to provide raw materials and drugs of appropriate quality and reliability and to meet applicable contract and regulatory requirements. In certain cases, we rely on single sources of supply of one or more critical materials. Consequently, in the event that supplies are delayed or interrupted for any reason, our ability to develop and produce our drug candidates or our ability to meet our supply obligations could be significantly impaired, which could have a material adverse effect on our business, financial condition and results of operations.
Restructuring	Restructuring We recognize restructuring charges related to reorganization plans that have been committed to by management when liabilities have been incurred. In connection with these activities, we record restructuring charges at fair value for: • contractual employee termination benefits provided that the obligations result from services already rendered based on vested rights to such benefits when the payment of benefits becomes probable and the amount can be reasonably estimated; • one-time employee termination benefits on the communication date from management to the employees provided that management has committed to a plan of termination, the plan identifies the employees and their expected termination dates, the details of termination benefits are complete, and it is unlikely that changes to the plan will be made or the plan will be withdrawn; • contract termination costs when we cancel the contract in accordance with its terms; and • costs to be incurred over the remaining contract term without economic benefit to us at the cease-use date. For one-time employee termination benefits, we recognize the liability in full on the communication date when future services are not required or amortize the liability ratably over the service period, if required. The fair value of termination benefits reflects our estimates of expected utilization of certain Company-funded post-employment benefits. See Note 8 for additional information on the severance expense that we recognized for employees terminated in connection with our reductions-in-force.
Goodwill	Goodwill Goodwill represents the excess of the price paid for another entity over the fair value of the assets acquired and liabilities assumed in a business combination. We are organized in one reporting unit and evaluate the goodwill for the Company as a whole. Goodwill has an indefinite useful life and is not amortized, but instead tested for impairment. Goodwill is assessed for impairment on an annual basis and whenever events and circumstances indicate that it may be impaired. Factors that may indicate potential impairment and trigger an impairment test include, but are not limited to, current economic, market and geopolitical conditions, including a significant, sustained decline in our stock price and market capitalization compared to the net book value; an adverse change in legal factors, business climate or operational performance of the business; or significant changes in the ability of the reporting unit to generate positive cash flows for our strategic business objectives. If the carrying value of the reporting unit, including goodwill, exceeds the reporting unit’s fair value, we will recognize a goodwill impairment loss, and we will write down goodwill such that the carrying value of the reporting unit equals its fair value, provided that we cannot reduce goodwill below zero. See Note 9 for additional information regarding the impairment charges we recorded during the three months ended March 31, 2023 in connection with our goodwill.
Long-Lived Assets	Long-Lived Assets We report property, plant and equipment at cost, net of accumulated depreciation. We capitalize major improvements and expense maintenance and repairs as incurred. We generally recognize depreciation on a straight-line basis. We depreciate manufacturing, laboratory and other equipment over their estimated useful lives of generally three to ten years, depreciate buildings over the estimated useful life of generally twenty years and amortize leasehold improvements over the shorter of the estimated useful lives or the remaining term of the related lease. We assess the impairment of long-lived assets whenever events or changes in business circumstances indicate that the carrying amounts of the assets may not be fully recoverable. In the case of property, plant and equipment and right-of-use assets for our leases, we determine whether there has been an impairment by comparing the carrying value of the asset to the anticipated undiscounted net cash flows associated with the asset. If such cash flows are less than the carrying value, we write down the asset to its fair value, which may be measured as anticipated net cash flows associated with the asset, discounted at a rate that we believe a market participant would utilize to reflect the risks associated with the cash flows, such as credit risk. See Note 8 for additional information regarding the impairment charges we recorded in connection with our leased facilities and certain property and equipment.
Leases	Leases We determine if an arrangement contains a lease at the inception of the arrangement. Right-of-use assets represent our right to use an underlying asset for the lease term, and lease liabilities represent our obligation to make lease payments arising from the lease. We recognize operating lease right-of-use assets and liabilities at the lease commencement date based on the present value of lease payments over the expected lease term. In determining the present value of lease payments, we use our incremental borrowing rate based on the information available at the lease commencement date. We have elected the practical expedient to account for the lease and non-lease components, such as common area maintenance charges, as a single lease component for our facilities leases, and elected the short-term lease recognition exemption for our short-term leases, under which we do not recognize lease liabilities and right-of-use assets for leases with an original term of twelve months or less. Our expected lease terms may include options to extend or terminate the lease when it is reasonably certain that we will exercise any such options. We recognize lease expense for our operating leases on a straight-line basis over the expected lease term. We have elected to recognize lease incentives, such as tenant improvement allowances, at the lease commencement date as a reduction of the right-of-use asset and lease liability until paid to us by the lessor to the extent that the lease provides a specified fixed or maximum level of reimbursement and we are reasonably certain to incur reimbursable costs at least equaling such amounts. Please see Note 4 for additional information regarding our leases.
Collaborative Arrangements	Collaborative Arrangements We enter into collaboration arrangements with pharmaceutical and biotechnology collaboration partners, under which we may grant licenses to our collaboration partners to further develop and commercialize one of our drug candidates, either alone or in combination with the collaboration partners’ compounds, or grant licenses to partners to use our technology to research and develop their own drug candidates. We may also perform research, development, manufacturing and supply activities under our collaboration agreements. Consideration under these contracts may include an upfront payment, development and regulatory milestones and other contingent payments, expense reimbursements, royalties based on net sales of approved drugs, and commercial sales milestone payments. Additionally, these contracts may provide options for the customer to purchase our proprietary PEGylation materials, drug candidates or additional contract research and development services under separate contracts. When we enter into collaboration agreements, we assess whether the arrangements fall within the scope of ASC 808, Collaborative Arrangements (ASC 808) based on whether the arrangements involve joint operating activities and whether both parties have active participation in the arrangement and are exposed to significant risks and rewards of the arrangement. To the extent that the arrangement falls within the scope of ASC 808, we assess whether the payments between us and our collaboration partner fall within the scope of other accounting literature. If we conclude that payments from the collaboration partner to us represent consideration from a customer, such as license fees and contract research and development activities, we account for those payments within the scope of ASC 606, Revenue from Contracts with Customers (ASC 606). However, if we conclude that our collaboration partner is not a customer for certain activities and associated payments, such as for certain collaborative research, development, manufacturing and commercial activities, we present such payments as a reduction of research and development expense or general and administrative expense, based on where we present the underlying expense.
Revenue Recognition	Revenue Recognition For elements of those arrangements that we determine should be accounted for under ASC 606, we assess which activities in our collaboration agreements are performance obligations that should be accounted for separately and determine the transaction price of the arrangement, which includes the assessment of the probability of achievement of future milestones and other potential consideration. For arrangements that include multiple performance obligations, such as granting a license or performing contract research and development activities or participation on joint steering or other committees, we allocate upfront and milestone payments under a relative standalone selling price method. Accordingly, we develop assumptions that require judgment to determine the standalone selling price for each performance obligation identified in the contract. These key assumptions may include revenue forecasts, clinical development timelines and costs, discount rates and probabilities of clinical and regulatory success. Product sales Product sales are primarily derived from manufacturing and supply agreements with our customers. We have assessed our current manufacturing and supply arrangements and have generally determined that they provide the customer an option to purchase our proprietary PEGylation materials. Accordingly, we treat each purchase order as a discrete exercise of the customer’s option (i.e. a separate contract) rather than as a component of the overall arrangement. The pricing for the manufacturing and supply is generally at a fixed price and may be subject to annual producer price index (PPI) adjustments. We invoice and recognize product sales when title and risk of loss pass to the customer, which generally occurs upon shipment. Customer payments are generally due 30 days from receipt of an invoice. We test our products for adherence to technical specifications before shipment; accordingly, we have not experienced any significant returns from our customers. We recognize costs related to shipping and handling of product to customers in cost of goods sold. Non-cash royalty revenue Generally, for our collaboration arrangements that include sales-based royalties, we have granted our collaboration partner a license to our intellectual property. Pursuant to these arrangements, our collaboration partners are typically obligated to pay a royalty that is based on the net sales of their approved drugs that are sold in the countries where we have intellectual property rights covering their drugs. We have sold our rights to receive sales-based royalties for CIMZIA®, MIRCERA®, MOVANTIK®, ADYNOVATE® and REBINYN® as further described in Note 5. For collaboration arrangements that include sales-based royalties, we have concluded that the license is the predominant item to which the royalties relate, which include commercial milestone payments based on the level of sales. Accordingly, we recognize royalty revenue when the underlying sales occur based on our best estimates of sales of the drugs. Our aggregate royalty and non-cash royalty revenue of $68.9 million, $69.8 million and $77.7 million for the years ended December 31, 2023, 2022 and 2021, respectively, represents revenue for granting licenses for which we had satisfied in prior periods. License, collaboration and other revenue License Grants: For collaboration arrangements that include a grant of a license to our intellectual property, we consider whether the license grant is distinct from the other performance obligations included in the arrangement. Generally, we would conclude that the license is distinct if the customer is able to benefit from the license with the resources available to it. For licenses that are distinct, we recognize revenues from nonrefundable, upfront payments and other consideration allocated to the license when the license term has begun and we have provided all necessary information regarding the underlying intellectual property to the customer, which generally occurs at or near the inception of the arrangement. Milestone Payments: At the inception of the arrangement and at each reporting date thereafter, we assess whether we should include any milestone payments or other forms of variable consideration in the transaction price, based on whether a significant reversal of revenue previously recognized is not probable upon resolution of the uncertainty. Since milestone payments may become payable to us upon the initiation of a clinical study, filing for or receipt of regulatory approval or the first commercial sale of a product, we review the relevant facts and circumstances to determine when we should update the transaction price, which may occur before the triggering event. When we do update the transaction price for milestone payments, we allocate it on a relative standalone selling price basis and record revenue on a cumulative catch-up basis, which results in recognizing revenue for previously satisfied performance obligations in such period. If we update the transaction price before the triggering event, we recognize the increase in the transaction price as a contract asset. Our partners generally pay development milestones subsequent to achievement of the triggering event. Research and Development Services: For amounts allocated to our research and development obligations in a collaboration arrangement, we recognize revenue over time using a proportional performance model, representing the transfer of goods or services as we perform activities over the term of the agreement.
Research and Development Expense	Research and Development Expense Research and development costs are expensed as incurred and include salaries, benefits and other operating costs such as outside services, supplies and allocated overhead costs. We perform research and development activities for our drug candidates and technology development and for certain third parties under collaboration agreements. For our drug candidates and our internal technology development programs, we invest our own funds without reimbursement from a third party. Where we perform research and development activities under a joint development collaboration, such as our collaboration with BMS, we record the cost reimbursement from our partner as a reduction to research and development expense when reimbursement amounts are due to us under the agreement. We record an accrued expense for the estimated unbilled costs of our clinical study activities performed by third parties. The financial terms of these agreements are subject to negotiation, vary from contract to contract and may result in uneven payment flows to our vendors. Payments under the contracts depend on factors such as the achievement of certain events, successful enrollment of patients and completion of certain clinical trial activities. We generally recognize costs associated with the start-up and reporting phases of the clinical trials as incurred. We generally accrue costs associated with the treatment phase of clinical trials based on the estimated activities performed by our third party vendors, including our contract research organizations. We may also accrue expenses based on the total estimated cost of the treatment phase on a per patient basis and expense the per patient cost ratably over the estimated patient treatment period. In specific circumstances, such as for certain time-based costs, we recognize clinical trial expenses ratably over the service period, as we believe that this methodology may be more reflective of the timing of costs incurred. We capitalize advance payments for goods or services that will be used or rendered for future research and development activities and recognize expense as the related goods are delivered or services performed. We base our estimates on the best information available at the time. However, additional information may become available to us in the future which may allow us to make a more accurate estimate in future periods. In this event, we may be required to record adjustments to research and development expenses in future periods when the actual level of activity becomes more certain. We generally consider such increases or decreases in cost as changes in estimates and reflect them in research and development expenses in the period identified.
Restructuring, Impairment and Other Costs for Terminated Program	Restructuring, Impairment and Other Costs for Terminated Program Amounts recorded as restructuring, impairment and other costs for terminated program for the year ended December 31, 2023 and 2022 relate to the 2022 and 2023 Restructuring Plans. See Note 8 for additional information.
Stock-Based Compensation	Stock-Based Compensation Stock-based compensation arrangements include grants of stock options, restricted stock units (RSUs), performance stock units (PSUs) under our equity incentive plans, as well as shares issued under our Employee Stock Purchase Plan (ESPP), through which employees may purchase our common stock at a discount to the market price. We expense the grant date fair value of stock-based compensation on a straight-line basis over the requisite service periods in our Consolidated Statements of Operations and recognize forfeitures as they occur. For options and RSUs that vest upon the achievement of performance milestones, we recognize expense provided that we believe that the performance milestones are probable of achievement, and we estimate the vesting period based on our evaluation of the estimated date of achievement of these milestones. For PSUs, we recognize expense based on the grant date fair value regardless of whether the market condition is met. The number of shares issuable under PSUs is based on our total shareholder return as compared to other companies within the NASDAQ biotechnology index over the measurement period and may be capped based on our absolute total shareholder return over such period. We report expense amounts in cost of goods sold, research and development expense, and general and administrative expense based on the function of the applicable employee. We estimate the grant date fair value of our stock-based compensation awards as follows: • Stock options - We use the Black-Scholes option pricing model for the respective grant to determine the grant date fair value of stock options and common stock issued under the Company's equity incentive plans or purchased under the ESPP. The Black-Scholes option pricing model requires the input of assumptions, including but not limited to, our stock price volatility over the term of the awards, and actual and projected employee stock option exercise behaviors. • PSUs - We use the Monte Carlo simulation model to determine the grant date fair value of PSUs. The Monte Carlo simulation model incorporates assumptions such as the volatility of our stock, the volatility of the stock of other peer companies within the index, and the correlation of both our stock and our peer companies’ stock to the index. • RSUs - The fair value of an RSU is equal to the closing price of our common stock on the grant date.
Income Taxes	Income Taxes We account for income taxes under the liability method. Under this method, we determine deferred tax assets and liabilities based on differences between the financial reporting and tax reporting bases of assets and liabilities, measured using enacted tax rates and laws that we expect to be in effect when we expect the differences to reverse. Realization of deferred tax assets is dependent upon future earnings, the timing and amount of which are uncertain. We record a valuation allowance against deferred tax assets to reduce their carrying value to an amount that is more likely than not to be realized. When we establish or reduce the valuation allowance related to the deferred tax assets, our provision for income taxes will increase or decrease, respectively, in the period we make such determination. We utilize a two-step approach to recognize and measure uncertain tax positions. The first step is to evaluate the tax position for recognition by determining if the weight of available evidence indicates that it is more likely than not that the position will be sustained upon tax authority examination, including resolution of related appeals or litigation processes, if any. The second step is to measure the tax benefit as the largest amount of benefit, determined on a cumulative probability basis, that is more than 50% likely of being realized upon ultimate settlement. For the year ended December 31, 2023, our income tax benefit was immaterial. For the years ended December 31, 2022 and 2021, our income tax provision primarily relates to our Nektar India subsidiary. As a result of the 2022 Restructuring Plan and our intent to wind down our foreign subsidiaries, we have recorded a provision for the repatriation of accumulated earnings and profits from India. See Note 10 for additional information.
Net Loss Per Share	Net Loss Per Share For all periods presented in the Consolidated Statements of Operations, the net loss available to common stockholders is equal to the reported net loss. We calculate basic net loss per share based on the weighted-average number of common shares outstanding during the periods presented. For the years ended December 31, 2023, 2022 and 2021, basic and diluted net loss per share are the same due to our net losses and the requirement to exclude potentially dilutive securities which would have an antidilutive effect on net loss per share. We excluded shares underlying the weighted average outstanding stock options, RSUs and PSUs, which totaled 20.4 million, 21.2 million and 18.4 million for the years ended December 31, 2023, 2022 and 2021, respectively.
Comprehensive Loss	Comprehensive Loss Comprehensive loss is the change in stockholders’ equity from transactions and other events and circumstances other than those resulting from investments by stockholders and distributions to stockholders. Our comprehensive loss includes our net loss, gains and losses from the foreign currency translation of the assets and liabilities of our foreign subsidiaries, and unrealized gains and losses on investments in available-for-sale securities.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In November 2023, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2023-07, Improvements to Reportable Segment Disclosures, which will require disclosure of incremental segment information on an annual and interim basis for all public entities. The amendments do not change how a public entity identifies its operating segments, aggregates those operating segments, or applies the quantitative thresholds to determine its reportable segments. ASU 2023-07 is effective for annual reporting beginning with the fiscal year ending December 31, 2024, and for interim periods thereafter. We are currently evaluating the incremental disclosures that will be required in the footnotes to our consolidated financial statements. In December 2023, the FASB issued ASU 2023-09, Improvements to Income Tax Disclosures, which will require incremental income tax disclosures on an annual basis for all public entities. The amendments require that public business entities disclose specific categories in the rate reconciliation and provide additional information for reconciling items meeting a quantitative threshold. The amendments also require disclosure of income taxes paid to be disaggregated by jurisdiction, and disclosure of income tax expense disaggregated by federal, state, and foreign. ASU 2023-09 is effective for annual reporting beginning with the fiscal year ending December 31, 2025. We are currently evaluating the incremental disclosures that will be required in our consolidated financial statements.

Stock-Based Compensation - Schedule of Black-Scholes Option-Pricing Model Assumptions Used to Calculate Fair Value of Employee Stock Options (Details) - $ / shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-Based Payment Arrangement [Abstract]
Average risk-free interest rate	4.00%	2.90%	1.20%
Dividend yield	0.00%	0.00%	0.00%
Average volatility factor	88.40%	77.90%	63.80%
Weighted-average expected life	5 years 1 month 6 days	5 years 7 months 6 days	5 years 6 months
Weighted-average grant-date fair value of options granted (in dollars per share)	$ 0.37	$ 3.18	$ 8.07

Consolidated Financial Statement Details

12 Months Ended

Dec. 31, 2023

Inventory Disclosure [Abstract]

Consolidated Financial Statement Details

Note 3 — Consolidated Financial Statement Details

Inventory

Inventory consists of the following (in thousands):


	December 31,
	2023		2022
Raw materials	$	1,861	$	2,575
Work-in-process		12,880		10,749
Finished goods		1,360		5,878
Total inventory	$	16,101	$	19,202

For the year ended December 31, 2023, we recorded a provision of $2.0 million for the net realizable value of our batches as an increase to cost of goods sold. Our manufacturing agreement with UCB Pharma (UCB) provides for a fixed price which we had negotiated in exchange for a higher royalty rate. Accordingly, when evaluating the net realizable value of our inventory for UCB, we include the negotiated increase of the royalties in our analysis, and the aggregate revenue has historically been greater than our manufacturing cost. Due to the decrease in the royalty rate for 2024 as a result of a settlement agreement with UCB, the aggregate revenue is expected to be less than our manufacturing cost, and therefore we recorded a provision for net realizable value. See Note 5 for additional information on the settlement agreement with UCB.

During the three months ended September 30, 2023, we recorded a provision for inventory obsolescence of $3.7 million as an increase to cost of goods sold for certain batches produced in our Huntsville, Alabama manufacturing facility, as a result of our identification of a quality concern of a solvent obtained from a third party that was used in the manufacturing of these batches. In the three months ended December 31, 2023, based on further analysis and partner approval, we reversed the provision and recorded a $3.7 million benefit to cost of goods sold.

Other Current Assets

Other current assets consists of the following (in thousands):


	December 31,
	2023		2022
Prepaid research and development expenses	$	4,325	$	7,398
Non-trade receivables and other		1,047		2,423
Other prepaid expenses		4,407		5,987
Total other current assets	$	9,779	$	15,808

Property, Plant and Equipment

Property, plant and equipment consists of the following (in thousands):


	December 31,
	2023			2022
Building and leasehold improvements	$	43,184		$	74,889
Laboratory equipment		14,537			24,243
Computer equipment and software		22,438			26,205
Manufacturing equipment		24,315			25,052
Furniture, fixtures, and other		541			4,263
Depreciable property, plant and equipment at cost		105,015			154,652
Less: accumulated depreciation		(86,898	)		(124,731	)
Depreciable property, plant and equipment, net		18,117			29,921
Construction-in-progress		739			2,530
Property, plant and equipment, net	$	18,856		$	32,451

Laboratory and manufacturing equipment, including construction-in-process, include assets that support both our manufacturing and research and development activities.

As a result of the sustained decrease in the fair value of our single reporting unit during the three months ended March 31, 2023, plans to sublease all of our laboratory and office space, and the weakening sublease markets, we recorded non-cash impairment charges of $4.8 million for property, plant and equipment for the year-ended December 31, 2023, which we report in restructuring, impairment and costs of terminated program in our Consolidated Statement of Operations. See Note 8 for additional information.

Depreciation and amortization expense for property, plant and equipment for the years ended December 31, 2023, 2022, and 2021 was $7.0 million, $12.2 million, and $13.0 million, respectively.

Goodwill

The following is a reconciliation of the change in our goodwill for the year ended December 31, 2023 (in thousands):


	Year Ended December 31, 2023
Goodwill – beginning balance	$	76,501
Impairment of goodwill		(76,501	)
Goodwill – ending balance	$	—

As a result of the decrease in the fair value of our single reporting unit during the three months ended March 31, 2023, we recorded a non-cash goodwill impairment charge of $76.5 million, which we report as impairment of goodwill in our Consolidated Statement of Operations. We had previously recognized goodwill primarily from our acquisitions of Shearwater Corp. and Aerogen, Inc. in 2001 and 2005, respectively. See Note 9 for additional information.

Accrued Expenses

Accrued expenses consist of the following (in thousands):


	December 31,
	2023		2022
Accrued compensation	$	5,553	$	9,582
Accrued clinical trial expenses		4,321		12,262
Liability to collaboration partners		2,678		3,808
Accrued contract termination costs		3,020		3,902
Other accrued expenses		6,590		7,003
Total accrued expenses	$	22,162	$	36,557

Accumulated Other Comprehensive Income (Loss)

The following table summarizes the changes in accumulated other comprehensive income (loss) by component (in thousands):


	Foreign currency translation			Available-for-sale securities			Accumulated Other Comprehensive Income
Balance at December 31, 2022	$	(5,131	)	$	(1,776	)	$	(6,907	)
Foreign currency translation gain		62			—			62
Unrealized gain on available-for-sale securities		—			1,826			1,826
Reclassification adjustments to income		5,099			—			5,099
Balance at December 31, 2023	$	30		$	50		$	80

The reclassification from accumulated other comprehensive loss relates to the closure of the operations of our foreign subsidiaries and has been included within other income (expense), net in our Consolidated Statement of Operations for the year ended December 31, 2023.

Impairment of Goodwill - Additional Information (Details) - USD ($)	1 Months Ended	3 Months Ended	12 Months Ended
	Jan. 31, 2023	Mar. 31, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Additional impairment charges on remaining long-lived assets	$ 0
Impairment of goodwill		$ 76,500,000	$ 76,501,000	$ 0	$ 0

Segment Reporting

12 Months Ended

Dec. 31, 2023

Segment Reporting [Abstract]

Segment Reporting

Note 12 — Segment Reporting

We operate in one business segment which focuses on applying our technology platforms to develop novel drug candidates. Our business offerings have similar economics and other characteristics, including the nature of products and manufacturing processes, types of customers, distribution methods and regulatory environment. We are comprehensively managed as one business segment by our Chief Executive Officer.

Our revenue is derived primarily from customers in the pharmaceutical and biotechnology industries. Revenue from UCB Pharma, Baxalta / Takeda, AstraZeneca and Pfizer represented 40%, 21%, 11% and 10% of our revenue, respectively, for the year ended December 31, 2023. Revenue from UCB Pharma, Baxalta / Takeda, AstraZeneca and Pfizer represented 37%, 25%, 14% and 11% of our revenue, respectively, for the year ended December 31, 2022. Revenue from BMS, UCB Pharma, Baxalta / Takeda, and AstraZeneca represented 36%, 23%, 16% and 13% of our revenue for the year-ended December 31, 2021.

Revenue by geographic area is based on the headquarters or shipping locations of our partners. The following table sets forth revenue by geographic area (in thousands):


	Year Ended December 31,
	2023		2022		2021
United States	$	11,481	$	9,841	$	10,114
Rest of World		78,641		82,214		91,793
Total revenue	$	90,122	$	92,055	$	101,907

At December 31, 2023 and 2022, all of our property, plant and equipment was located in the United States.

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-22

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 15
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-15

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 31
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-31

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-32

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-42

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-32

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 40
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-40

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org//280/tableOfContent

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 26
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-26

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 34
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-34

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 41
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-41

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-21

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-21

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-32

+ Details

Operating Leases (Tables)

12 Months Ended

Dec. 31, 2023

Leases [Abstract]

Schedule of Lease Expense

The

components of lease expense, which we include in operating expenses in our Consolidated Statements of Operations, were as follows (in thousands):


	Year Ended December 31,
	2023		2022		2021
Operating lease expense	$	12,116	$	17,057	$	19,153
Variable lease expense		7,027		10,700		8,974
Total lease expense	$	19,143	$	27,757	$	28,127

Schedule of Future Minimum Lease Payments for Operating Leases

As of December 31, 2023, the maturities of our operating lease liabilities were as follows (in thousands):


Year ending December 31,
2024	$	19,822
2025		22,255
2026		22,958
2027		23,682
2028		24,427
2029 and thereafter		27,303
Total lease payments		140,447
Less: portion representing interest		(22,671	)
Operating lease liabilities		117,776
Less: current portion		(19,259	)
Operating lease liabilities, less current portion	$	98,517

Schedule of Maturities of Operating Lease Receivables from Subleases

As of December 31, 2023, maturities of our operating lease receivables from subleases for each of the next five years and thereafter were as follows:


Year ending December 31,
2024	$	1,360
2025		1,535
2026		1,589
2027		1,645
2028		1,702
2029 and thereafter		1,757
Gross Lease Receivable	$	9,588

Operating Leases - Schedule of Lease Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Leases [Abstract]
Operating lease expense	$ 12,116	$ 17,057	$ 19,153
Variable lease expense	7,027	10,700	8,974
Total lease expense	$ 19,143	$ 27,757	$ 28,127

Restructuring, Impairment and Costs of Terminated Program - Sublease Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Restructuring Cost and Reserve [Line Items]
Book value in excess of fair value	$ 36,962	$ 67,875
Less: Amounts recorded as amortization for Third St. facility and Mission Bay facility	(1,634)	(2,114)
Total impairment of sublease assets		65,761
Total impairment of right-of-use assets and property, plant and equipment	35,328	65,761	$ 0
Reported Value Measurement
Restructuring Cost and Reserve [Line Items]
Property, plant and equipment and operating lease right-of-use assets	53,498	88,829
Property, Plant and Equipment
Restructuring Cost and Reserve [Line Items]
Book value in excess of fair value	5,034	11,568
Less: Amounts recorded as amortization for Third St. facility and Mission Bay facility	(263)	(397)
Total impairment of sublease assets	30,600	11,171
Total impairment of right-of-use assets and property, plant and equipment	4,771
Property, Plant and Equipment \| Reported Value Measurement
Restructuring Cost and Reserve [Line Items]
Property, plant and equipment and operating lease right-of-use assets	7,206	16,348
Operating Lease Right-of-Use Assets
Restructuring Cost and Reserve [Line Items]
Book value in excess of fair value	31,928	56,307
Less: Amounts recorded as amortization for Third St. facility and Mission Bay facility	(1,371)	(1,717)
Total impairment of sublease assets		54,590
Total impairment of right-of-use assets and property, plant and equipment	30,557
Operating Lease Right-of-Use Assets \| Reported Value Measurement
Restructuring Cost and Reserve [Line Items]
Property, plant and equipment and operating lease right-of-use assets	46,292	72,481
Level 3 \| Estimate of Fair Value Measurement
Restructuring Cost and Reserve [Line Items]
Property, plant and equipment and operating lease right-of-use assets	(16,536)	(20,954)
Level 3 \| Property, Plant and Equipment \| Estimate of Fair Value Measurement
Restructuring Cost and Reserve [Line Items]
Property, plant and equipment and operating lease right-of-use assets	(2,172)	(4,780)
Level 3 \| Operating Lease Right-of-Use Assets \| Estimate of Fair Value Measurement
Restructuring Cost and Reserve [Line Items]
Property, plant and equipment and operating lease right-of-use assets	$ (14,364)	$ (16,174)

Impairment of Goodwill

12 Months Ended

Dec. 31, 2023

Goodwill and Intangible Assets Disclosure [Abstract]

Impairment of Goodwill

Note 9 — Impairment of Goodwill

During the three months ended March 31, 2023, our stock price and resulting market capitalization experienced a significant, sustained decline. Accordingly, we assessed our long-lived assets, including our property, plant and equipment, right-of-use assets and goodwill, for impairment.

As part of our long-lived asset impairment analysis, we first assessed which long-lived assets have identifiable cash flows that are largely independent of the cash flows of other groups of assets. We concluded that the sublease assets, for which we have recognized significant impairment charges during 2022 and 2023, including for the three months ended March 31, 2023, are independent of our entity-wide group. See Note 8 for additional information regarding impairment charges that we have recorded for our sublease assets.

We next evaluated our remaining long-lived assets for impairment and performed a recoverability test using the undiscounted cash flows approach. We did not recognize any additional impairment charges on the remaining long-lived assets.

Finally, we measured the fair value of our reporting unit utilizing both income and market approaches for our entity-wide asset impairment analysis. Based on this analysis, we wrote off all of our goodwill, resulting in a non-cash impairment charge of $76.5 million during the three months ended March 31, 2023, which we reported as impairment of goodwill in our Consolidated Statements of Operations for the year ended December 31, 2023. We had previously recognized goodwill primarily from our acquisitions of Shearwater Corp. and Aerogen, Inc. in 2001 and 2005, respectively.

Income Taxes - Schedule of Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance	$ 85,845	$ 80,604	$ 78,665
Tax positions related to current year:
Additions	848	378	2,371
Reductions	0	0	0
Tax positions related to prior years:
Additions	40,079	5,272	58
Reductions	0	0	(490)
Settlements	0	0	0
Lapses in statute of limitations	(274)	(409)	0
Ending balance	$ 126,498	$ 85,845	$ 80,604

License and Collaboration Agreements - Fair Value of Derivative Liabilities (Details) - Fair Value, Level 3 - Development Derivative Liability - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value as of December 31, 2021 and February 12, 2021 (inception), respectively	$ 27,726	$ 0
Non-cash research and development expense	4,951	16,703
Cash receipts from SFJ	750	3,000
Change in the fair value of development derivative liability	(33,427)	8,023
Fair value at end of period	$ 0	$ 27,726

Stock-Based Compensation - Schedule of Stock Option Activity Under Equity Incentive Plans (Details) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($) $ / shares shares
Number of Shares
Outstanding, beginning balance (in shares) \| shares	14,088
Options granted (in shares) \| shares	11,854
Options exercised (in shares) \| shares	0
Options forfeited and canceled (in shares) \| shares	(2,926)
Outstanding, ending balance (in shares) \| shares	23,016
Weighted- Average Exercise Price per Share
Outstanding, beginning balance (in dollars per share) \| $ / shares	$ 16.4
Options granted (in dollars per share) \| $ / shares	0.51
Options exercised (in dollars per share) \| $ / shares	0
Options forfeited and canceled (in dollars per share) \| $ / shares	16.07
Outstanding, ending balance (in dollars per share) \| $ / shares	$ 8.26
Weighted- Average Remaining Contractual Life (in Years)
Weighted-Average Remaining Contractual Life, Outstanding	6 years 5 months 1 day
Aggregate Intrinsic Value, Outstanding \| $	$ 0
Number of Shares, Exercisable (in shares) \| shares	6,425
Weighted-Average Exercise Price Per Share, Exercisable (in dollars per share) \| $ / shares	$ 22.99
Weighted-Average Remaining Contractual Life, Exercisable	3 years 8 months 4 days
Aggregate Intrinsic Value, Exercisable \| $	$ 0

Segment Reporting - Revenue by Geographic Area (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Revenue by geographic area
Total revenue	$ 90,122	$ 92,055	$ 101,907
United States \| Reportable Geographical Components
Revenue by geographic area
Total revenue	11,481	9,841	10,114
Rest of World \| Reportable Geographical Components
Revenue by geographic area
Total revenue	$ 78,641	$ 82,214	$ 91,793

- Definition

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 924
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 11.L)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479941/924-10-S99-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479806/606-10-50-5

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 30
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-30

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-42

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-22

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-32

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 40
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-40

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-22

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-32

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 41
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-41

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479806/606-10-50-4

+ Details

Cash and Investments in Marketable Securities - Portfolio of Cash and Investments in Marketable Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	$ 294,073
Gross Unrealized Gains	132
Gross Unrealized Losses	(82)	$ (1,800)
Fair Value	294,123	427,726
Cash	17,843	8,798
Total cash and investments in marketable securities	329,441	504,977
Corporate notes and bonds \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	38,799
Gross Unrealized Gains	85
Gross Unrealized Losses	(2)
Fair Value	38,882	83,522
Corporate commercial paper \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	255,274
Gross Unrealized Gains	47
Gross Unrealized Losses	(80)
Fair Value	255,241	344,204
Money market funds \| Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	2,359	47,054
Certificates of deposit \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	$ 15,116	$ 21,399

Stockholders' Equity - Schedule of Shares of Common Stock Reserved for Future Issuance (Details) shares in Thousands	Dec. 31, 2023 shares
Class of Stock [Line Items]
Total common stock reserved for issuance	38,122

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

+ Details

Consolidated Financial Statement Details (Tables)

12 Months Ended

Dec. 31, 2023

Inventory Disclosure [Abstract]

Schedule of Inventory

Inventory

Inventory consists of the following (in thousands):


	December 31,
	2023		2022
Raw materials	$	1,861	$	2,575
Work-in-process		12,880		10,749
Finished goods		1,360		5,878
Total inventory	$	16,101	$	19,202

Schedule of Other Current Assets

Other Current Assets

Other current assets consists of the following (in thousands):


	December 31,
	2023		2022
Prepaid research and development expenses	$	4,325	$	7,398
Non-trade receivables and other		1,047		2,423
Other prepaid expenses		4,407		5,987
Total other current assets	$	9,779	$	15,808

Schedule of Property, Plant and Equipment

Property, Plant and Equipment

Property, plant and equipment consists of the following (in thousands):


	December 31,
	2023			2022
Building and leasehold improvements	$	43,184		$	74,889
Laboratory equipment		14,537			24,243
Computer equipment and software		22,438			26,205
Manufacturing equipment		24,315			25,052
Furniture, fixtures, and other		541			4,263
Depreciable property, plant and equipment at cost		105,015			154,652
Less: accumulated depreciation		(86,898	)		(124,731	)
Depreciable property, plant and equipment, net		18,117			29,921
Construction-in-progress		739			2,530
Property, plant and equipment, net	$	18,856		$	32,451

We recorded the gains and losses as follows (in thousands):


	Year Ended December 31,
	2023		2022
Proceeds from sales	$	1,245	$	13,196
Net book value of assets		2,545		9,870
Total (gain) loss on sale or disposal of other property, plant and equipment, net	$	1,300	$	(3,326	)

Schedule of Goodwill

Goodwill

The following is a reconciliation of the change in our goodwill for the year ended December 31, 2023 (in thousands):


	Year Ended December 31, 2023
Goodwill – beginning balance	$	76,501
Impairment of goodwill		(76,501	)
Goodwill – ending balance	$	—

Schedule of Accred Expenses

Accrued Expenses

Accrued expenses consist of the following (in thousands):


	December 31,
	2023		2022
Accrued compensation	$	5,553	$	9,582
Accrued clinical trial expenses		4,321		12,262
Liability to collaboration partners		2,678		3,808
Accrued contract termination costs		3,020		3,902
Other accrued expenses		6,590		7,003
Total accrued expenses	$	22,162	$	36,557

Schedule of Accumulated Other Comprehensive Income (Loss)

Accumulated Other Comprehensive Income (Loss)

The following table summarizes the changes in accumulated other comprehensive income (loss) by component (in thousands):


	Foreign currency translation			Available-for-sale securities			Accumulated Other Comprehensive Income
Balance at December 31, 2022	$	(5,131	)	$	(1,776	)	$	(6,907	)
Foreign currency translation gain		62			—			62
Unrealized gain on available-for-sale securities		—			1,826			1,826
Reclassification adjustments to income		5,099			—			5,099
Balance at December 31, 2023	$	30		$	50		$	80

- Definition

Tabular disclosure of goodwill by reportable segment and in total which includes a rollforward schedule.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 24
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482548/350-20-55-24

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-1

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-1

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-1

Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-1

Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-1

Reference 7: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-1

Reference 8: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-1

Reference 9: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-1

Reference 10: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-1

Reference 11: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1A
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-1A

Reference 12: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-2

+ Details

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2023	Dec. 31, 2022
Statement of Financial Position [Abstract]
Preferred stock, par value (in usd per share)	$ 0.0001	$ 0.0001
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares designated (in shares)	0	0
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in usd per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	300,000,000	300,000,000
Common stock, shares issued (in shares)	191,384,000	188,560,000
Common stock, shares outstanding (in shares)	191,384,000	188,560,000

Cover - USD ($) $ in Millions	12 Months Ended
Cover - USD ($) $ in Millions	Dec. 31, 2023	Feb. 27, 2024	Jun. 30, 2023
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2023
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	0-24006
Entity Registrant Name	NEKTAR THERAPEUTICS
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	94-3134940
Entity Address, Address Line One	455 Mission Bay Boulevard South
Entity Address, City or Town	San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94158
City Area Code	415
Local Phone Number	482-5300
Title of 12(b) Security	Common Stock, $0.0001 par value
Trading Symbol	NKTR
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Document Financial Statement Error Correction Flag	false
Entity Shell Company	false
Entity Public Float			$ 109
Entity Common Stock, Shares Outstanding (in shares)		183,617,817
Documents Incorporated by Reference	Portions of registrant’s definitive Proxy Statement to be filed for its 2024 Annual Meeting of Stockholders are incorporated by reference into Part III hereof. Such Proxy Statement will be filed with the Securities and Exchange Commission within 120 days of the end of the fiscal year covered by this Annual Report on Form 10-K.
Amendment Flag	false
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Entity Central Index Key	0000906709
Auditor Name	Ernst & Young LLP
Auditor Location	San Mateo, California
Auditor Firm ID	42

Consolidated Financial Statement Details - Schedule of Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment [Line Items]
Depreciable property, plant and equipment at cost	$ 105,015	$ 154,652
Less: accumulated depreciation	(86,898)	(124,731)
Depreciable property, plant and equipment, net	18,117	29,921
Construction-in-progress	739	2,530
Property, plant and equipment, net	18,856	32,451
Building and leasehold improvements
Property, Plant and Equipment [Line Items]
Depreciable property, plant and equipment at cost	43,184	74,889
Computer equipment and software
Property, Plant and Equipment [Line Items]
Depreciable property, plant and equipment at cost	22,438	26,205
Manufacturing equipment
Property, Plant and Equipment [Line Items]
Depreciable property, plant and equipment at cost	24,315	25,052
Laboratory equipment
Property, Plant and Equipment [Line Items]
Depreciable property, plant and equipment at cost	14,537	24,243
Furniture, fixtures, and other
Property, Plant and Equipment [Line Items]
Depreciable property, plant and equipment at cost	$ 541	$ 4,263

Commitments and Contingencies

12 Months Ended

Dec. 31, 2023

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

Note 6 — Commitments and Contingencies

Purchase Commitments

In the normal course of business, we enter into various firm purchase commitments related to contract manufacturing, clinical development and certain other items. As of December 31, 2023, these commitments were approximately $3.3 million.

Legal Matters

From time to time, we are involved in lawsuits, arbitrations, claims, investigations and proceedings, consisting of intellectual property, commercial, employment and other matters, which arise in the ordinary course of business. We make provisions for liabilities when it is both probable that a liability has been incurred and the amount of the loss can be reasonably estimated. Such provisions are reviewed at least quarterly and adjusted to reflect the impact of settlement negotiations, judicial and administrative rulings, advice of legal counsel, and other information and events pertaining to a particular case. Litigation is inherently unpredictable. If any unfavorable ruling were to occur in any specific period, there exists the possibility of a material adverse impact on the results of our operations for that period and on our cash flows and liquidity.

On August 7, 2023, we filed a complaint in the United States District Court for the Northern District of California against Lilly alleging, among other claims, breach of contract and breach of implied covenant of good faith and fair dealing, in connection with our collaboration with Lilly.

We have recorded no liability for any litigation matters in our Consolidated Balance Sheets at either December 31, 2023 or December 31, 2022.

Indemnification Obligations

During the course of our normal operating activities, we have agreed to certain contingent indemnification obligations as further described below. The term of our indemnification obligations is generally perpetual. There is generally no limitation on the potential amount of future payments we could be required to make under these indemnification obligations. To date, we have not incurred significant costs to defend lawsuits or settle claims based on our indemnification obligations. If any of our indemnification obligations is triggered, we may incur substantial liabilities. Because the aggregate

amount of any of these potential indemnification obligations is not a stated amount, we cannot reasonably estimate the overall maximum amount of any such obligations. We have recorded no liabilities for these obligations in our Consolidated Balance Sheets at either December 31, 2023 or December 31, 2022.

Indemnifications in Connection with Commercial Agreements

As part of our collaboration agreements with our partners related to the license, development, manufacture and supply of drugs and PEGylation materials based on our proprietary technologies and drug candidates, we generally agree to defend, indemnify and hold harmless our partners from and against third party liabilities arising out of the agreement, including product liability (with respect to our activities) and infringement of intellectual property to the extent the intellectual property is developed by us and licensed to our partners. The term of these indemnification obligations is generally perpetual commencing after execution of the agreement. There is generally no limitation on the potential amount of future payments we could be required to make under these indemnification obligations.

From time to time, we enter into other strategic agreements such as divestitures and financing transactions pursuant to which we are required to make representations and warranties and undertake to perform or comply with certain covenants. For example, we made certain intellectual property representations in connection with our RPI and HCR transactions, however, the time limitation we have to indemnify RPI with respect to any breach of these intellectual property-based representations and warranties has passed. In the event it is determined that we breached certain of the representations and warranties or covenants made by us in any such agreements or certain express indemnification provisions are applicable, we could incur substantial indemnification liabilities depending on the timing, nature, and amount of any such claims.

To date, we have not incurred any costs to defend lawsuits or settle claims related to these indemnification obligations, nor any breaches of representations or warranties or covenants. Because the aggregate amount of any potential indemnification obligation is not a stated amount, we cannot reasonably estimate the overall maximum amount of any such obligations.

Indemnification of Underwriters and Initial Purchasers of our Securities

In connection with our sale of equity we have agreed to defend, indemnify and hold harmless our underwriters or initial purchasers, as applicable, as well as certain related parties from and against certain liabilities, including liabilities under the Securities Act of 1933, as amended.

Director and Officer Indemnifications

As permitted under Delaware law, and as set forth in our Certificate of Incorporation and our Bylaws, we indemnify our directors, executive officers, other officers, employees, and other agents for certain events or occurrences that may arise while in such capacity. The maximum potential amount of future payments we could be required to make under this indemnification is unlimited; however, we have insurance policies that may limit our exposure and may enable us to recover a portion of any future amounts paid. Assuming the applicability of coverage, the willingness of the insurer to assume coverage, and subject to certain retention, loss limits and other policy provisions, we believe any obligations under this indemnification would not be material, other than retention of up to $5.0 million per incident for merger and acquisition related claims, $5.0 million per incident for securities related claims and $5.0 million per incident for non-securities related claims per our insurance policy. However, no assurances can be given that the covering insurers will not attempt to dispute the validity, applicability, or amount of coverage without expensive litigation against these insurers, in which case we may incur substantial liabilities as a result of these indemnification obligations.

Commitments and Contingencies (Details) - USD ($)	Dec. 31, 2023	Dec. 31, 2022
Loss Contingencies [Line Items]
Purchase commitments related to contract manufacturing, clinical development and certain other items	$ 3,300,000
Liability for litigation	0	$ 0
Indemnification Obligation
Loss Contingencies [Line Items]
Litigation matters, liabilities	0	$ 0
Merger and Acquisition Related Claims \| Maximum
Loss Contingencies [Line Items]
Obligations under Director and Officer Indemnifications per incident	0
Securities Related Claims
Loss Contingencies [Line Items]
Obligations under Director and Officer Indemnifications per incident	0
Non-Securities Related Claims
Loss Contingencies [Line Items]
Obligations under Director and Officer Indemnifications per incident	$ 0

License and Collaboration Agreements (Tables)

12 Months Ended

Dec. 31, 2023

License And Collaboration Agreements [Abstract]

Schedule of Derivative Liabilities at Fair Value

The following table presents the change in the derivative liability for the years ended December 31, 2022 and 2021:


		Year Ended December 31,
	Fair Value Hierarchy Level	2022			2021
Fair value as of December 31, 2021 and February 12, 2021 (inception), respectively	3	$	27,726		$	—
Non-cash research and development expense			4,951			16,703
Cash receipts from SFJ			750			3,000
Change in the fair value of development derivative liability			(33,427	)		8,023
Fair value at end of period	3	$	—		$	27,726

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended	12 Months Ended			142 Months Ended
	Mar. 31, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2023
Cash flows from operating activities:
Net loss		$ (276,056)	$ (368,198)	$ (523,837)
Adjustments to reconcile net loss to net cash used in operating activities:
Non-cash royalty revenue related to the sales of future royalties		(68,921)	(69,794)	(77,746)	$ (472,166)
Non-cash interest expense on liabilities related to sales of future royalties		25,334	28,911	47,313	298,518
Loss on revaluation of liability related to the sale of future royalties		0	0	24,410
Change in fair value of development derivative liability		0	(33,427)	8,023
Non-cash research and development expense		0	4,951	16,703
Stock-based compensation		33,388	57,320	94,674
Depreciation and amortization		7,815	13,030	14,146
Deferred income tax expense		(140)	2,708	(102)
Impairment of right-of-use assets and property, plant and equipment		35,328	65,761	0
Impairment of goodwill	$ 76,500	76,501	0	0
(Gain) loss on sale or disposal of property, plant and equipment, net		1,300	(3,326)	0
Provision for inventory obsolescence		2,402	0	0
Foreign currency translation adjustment		5,099	0	0
Amortization of premiums (discounts), net and other non-cash transactions		(14,856)	(2,435)	6,730
Changes in operating assets and liabilities:
Accounts receivable		4,776	16,511	12,397
Inventory		699	(3,401)	(509)
Operating leases, net		(8,850)	(2,680)	2,340
Other assets		3,583	6,906	(2,586)
Accounts payable		(2,884)	3,103	(11,690)
Accrued expenses		(17,124)	(19,947)	(22,926)
Net cash used in operating activities		(192,606)	(304,007)	(412,660)
Cash flows from investing activities:
Purchases of investments		(511,699)	(467,914)	(960,689)
Maturities of investments		650,883	826,229	1,166,951
Sales of investments		0	0	11,504
Purchases of property, plant and equipment		(865)	(5,676)	(14,989)
Sales of property, plant and equipment		1,245	13,196	0
Net cash provided by investing activities		139,564	365,835	202,777
Cash flows from financing activities:
Cash receipts from development derivative liability		0	750	3,000
Proceeds from shares issued under equity compensation plans		30	758	33,238
Net cash provided by financing activities		30	1,508	36,238
Effect of foreign exchange rates on cash and cash equivalents		62	(327)	(92)
Net increase (decrease) in cash and cash equivalents		(52,950)	63,009	(173,737)
Cash and cash equivalents at beginning of year	$ 88,227	88,227	25,218	198,955
Cash and cash equivalents at end of year		35,277	88,227	25,218	$ 35,277
Supplemental disclosure of cash flow information:
Operating lease right-of-use assets recognized in exchange for lease liabilities		0	0	1,057
Cash paid for income taxes		$ 2,656	$ 272	$ 325

Liabilities Related to the Sales of Future Royalties

12 Months Ended

Dec. 31, 2023

Note 5 — Liabilities Related to the Sales of Future Royalties

On February 24, 2012, we entered into a purchase and sale agreement (the 2012 Purchase and Sale Agreement) with RPI Finance Trust (RPI), an affiliate of Royalty Pharma, pursuant to which we sold, and RPI purchased, our right to receive royalty payments (the 2012 Transaction Royalties) arising from the worldwide net sales, from and after January 1, 2012, of (a) CIMZIA®, under our license, manufacturing and supply agreement with UCB, and (b) MIRCERA®, under our license, manufacturing and supply agreement with F. Hoffmann-La Roche Ltd and Hoffmann-La Roche Inc. (together referred to as Roche). We received aggregate cash proceeds of $124.0 million for the 2012 Transaction Royalties. Although we sold all of our rights to receive royalties from the CIMZIA® and MIRCERA® products, as a result of our ongoing manufacturing and supply obligations related to the generation of these royalties, we continue to account for these royalties as revenue. We

recorded the $124.0 million in proceeds from this transaction as a liability (the 2012 Royalty Obligation) that is amortized using the effective interest method over the estimated life of the 2012 Purchase and Sale Agreement as royalties from the CIMZIA® and MIRCERA® products are remitted directly to RPI. As of December 31, 2023, our prospective effective interest rate used to amortize the liability is 30%.

We were required to pay RPI an aggregate $10.0 million as a result of worldwide net sales of MIRCERA® during the years 2013 and 2012 not reaching certain minimum thresholds. The 2012 Purchase and Sale Agreement does not include any other potential payments related to minimum net sales thresholds.

On June 5, 2020, UCB served notice of a Declaratory Judgment of Patent Invalidity, filed in the United States District Court for the District of Delaware, seeking a declaration of invalidity of certain of our patents that we had licensed to UCB and pursued similar actions in other jurisdictions. On October 14, 2021, RPI and we entered into a Letter Agreement which permitted us to enter into a Settlement Agreement, effective October 13, 2021, with UCB to effect the negotiation between RPI and UCB in which UCB and RPI agreed to a reduction in the royalty term and annual decreases in the royalty rate over the remaining royalty term in exchange for UCB’s withdrawal of all of UCB’s litigation and challenges.

We concluded that we should account for the decrease in royalty payments to RPI as a result of these agreements as a modification of our liability. Due to the significance of the change in the estimated royalty payments, we concluded that we should treat the modification as an extinguishment of the prior liability and recognize a new liability based on the revised royalty payments and term, discounted to fair value. Accordingly, we estimated the fair value to be approximately $84.7 million. As a result, we recognized a non-cash loss of $23.5 million on the revaluation of the prior liability in the three months ended December 31, 2021, and we wrote off the remaining $0.9 million of unamortized transaction costs. We present these charges in Loss on revaluation of liability related to the sale of future royalties line in our Consolidated Statement of Operations.

On December 16, 2020, we entered into a purchase and sale agreement (the 2020 Purchase and Sale Agreement) with entities managed by Healthcare Royalty Management, LLC (collectively, HCR). Pursuant to the 2020 Purchase and Sale Agreement, we agreed to sell to HCR certain of our rights to receive royalty payments (the 2020 Transaction Royalties) arising from the worldwide net sales, from and after October 1, 2020 until such time that certain return thresholds are met as described below, of (a) MOVANTIK® under that certain License Agreement, dated September 20, 2009, by and between Nektar and AstraZeneca AB, as amended, (b) ADYNOVATE® under that certain Exclusive Research, Development, License and Manufacturing and Supply Agreement, dated September 26, 2005, by and among Nektar, Baxalta US Inc. and Baxalta GmbH, as amended, (c) REBINYN® under that certain Settlement and License Agreement, dated December 21, 2016, by and among Nektar, Novo Nordisk Inc., Novo Nordisk A/S and Novo Nordisk A/G and (d) licensed products under that certain Right to Sublicense Agreement, dated October 27, 2017, by and among Nektar, Baxalta Incorporated, Baxalta US Inc. and Baxalta GmbH. Although we sold all of our rights to receive royalties from these products up to the cap, as a result of the limits on the 2020 Transaction Royalties to be received by HCR and our ongoing manufacturing and supply obligations related to the generation of these royalties, we account for the transaction as debt and recognize these non-cash royalties as revenue. We recorded the $150.0 million in proceeds from this transaction as a liability (the 2020 Royalty Obligation) that will be amortized using the effective interest method over the estimated life of the 2020 Purchase and Sale Agreement. As of December 31, 2023, our prospective effective interest rate used to amortize the liability is 17%.

The 2020 Purchase and Sale Agreement was to automatically expire, and the payment of the 2020 Transaction Royalties to HCR would cease, when HCR received payments of the 2020 Transaction Royalties equal to $210.0 million (the 2025 Threshold), if the 2025 Threshold is achieved on or prior to December 31, 2025, or $240.0 million, if the 2025 Threshold is not achieved on or prior to December 31, 2025 (or, if earlier, the date on which the last royalty payment under the relevant license agreements is made). On March 4, 2024, Nektar and HCR amended the 2020 Purchase and Sale Agreement to remove the cap on the royalties in exchange for $15.0 million. Accordingly, HCR will receive all future royalties of these products, and none of these royalties will return to Nektar.

The following table shows the activity within the liability account of each arrangement (in thousands):


	Year-Ended December 31, 2023									Period from inception to December 31, 2023
	2012 Purchase and Sale Agreement			2020 Purchase and Sale Agreement			Total			2012 Purchase and Sale Agreement			2020 Purchase and Sale Agreement			Total
Liabilities related to the sales of future royalties—beginning balance	$	55,167		$	102,294		$	157,461		$	—		$	—		$	—
Royalty monetization proceeds		—			—			—			124,000			150,000			274,000
Non-cash royalty revenue		(37,323	)		(31,598	)		(68,921	)		(353,847	)		(118,319	)		(472,166	)
Non-cash interest expense		6,373			18,961			25,334			240,542			57,976			298,518
Payments to RPI		—			—			—			(10,000	)		—			(10,000	)
Loss on revaluation of liability related to the sale of future royalties		—			—			—			23,522			—			23,522
Liabilities related to the sales of future royalties – ending balance		24,217			89,657			113,874			24,217			89,657			113,874
Less: unamortized transaction costs		—			(1,249	)		(1,249	)		—			(1,249	)		(1,249	)
Liabilities related to the sales of future royalties, net	$	24,217		$	88,408		$	112,625		$	24,217		$	88,408		$	112,625

As royalties are remitted to RPI and HCR by our licensees, the balances of the respective Royalty Obligations will be effectively repaid over the lives of the agreements. To determine the amortization of the Royalty Obligations, we are required to estimate the total amount of future royalty payments to be received by RPI and HCR, respectively. We periodically assess the estimated royalty payments to RPI and HCR from our licensees and to the extent the amount or timing of such payments is materially different than our original estimates, we prospectively adjust the imputed interest rate and the related amortization of the appropriate Royalty Obligation.

Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2023

Equity [Abstract]

Schedule of Shares of Common Stock Reserved for Future Issuance

The following table lists the Black-Scholes option-pricing model assumptions used to calculate the fair value of employee and director stock options, as well as the resulting grant-date fair value:


	Year Ended December 31,
	2023			2022			2021
Average risk-free interest rate		4.0	%		2.9	%		1.2	%
Dividend yield		0.0	%		0.0	%		0.0	%
Average volatility factor		88.4	%		77.9	%		63.8	%
Weighted-average expected life	5.1 years			5.6 years			5.5 years
Weighted-average grant-date fair value of options granted	$	0.37		$	3.18		$	8.07

Stock-Based Compensation - Schedule of Restricted Stock Unit Award Activity (Details) - Restricted Stock Units (RSU) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Units Issued
Beginning balance (in shares)	9,312
Granted (in shares)	126
Vested and released (in shares)	(2,759)
Forfeited and canceled (in shares)	(2,449)
Ending balance (in shares)	4,230	9,312
Weighted- Average Grant Date Fair Value
Beginning balance (in dollars per share)	$ 6.81
Granted (in dollars per share)	1.10	$ 4.14	$ 14.68
Vested and released (in dollars per share)	7.93
Forfeited and canceled (in dollars per share)	6.11
Ending balance (in dollars per share)	$ 6.14	$ 6.81

Restructuring, Impairment and Costs of Terminated Program - Schedule of Property, Plant and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Restructuring Cost and Reserve [Line Items]
Proceeds from sales	$ 1,245	$ 13,196	$ 0
Property, plant and equipment, net	18,856	32,451
Facility Closing
Restructuring Cost and Reserve [Line Items]
Proceeds from sales	1,245	13,196
Property, plant and equipment, net	2,545	9,870
Total (gain) loss on sale or disposal of property, plan and equipment, net	$ 1,300	$ (3,326)

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References + Details

Operating Leases - Schedule of Future Minimum Lease Payments for Operating Leases (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Leases [Abstract]
2024	$ 19,822
2025	22,255
2026	22,958
2027	23,682
2028	24,427
2029 and thereafter	27,303
Total lease payments	140,447
Less: portion representing interest	(22,671)
Operating lease liabilities	117,776
Less: current portion	(19,259)	$ (18,667)
Operating lease liabilities, less current portion	$ 98,517	$ 112,829

Restructuring, Impairment and Costs of Terminated Program (Tables)

12 Months Ended

Dec. 31, 2023

Restructuring and Related Activities [Abstract]

Schedule of Restructuring, Impairment and Costs of Terminated Program

Restructuring, impairment and costs of terminated program includes the following (in thousands):


	Year Ended December 31,
	2023						2022
	2022 Restructuring Plan		2023 Restructuring Plan		Total		2022 Restructuring Plan
Clinical trial expense, other third-party and employee costs for the wind down of the bempegaldesleukin program	$	5,492	$	—	$	5,492	$	31,693
Severance and benefit expense		—		7,885		7,885		30,904
Impairment of right-of-use assets and property, plant and equipment		14,728		20,600		35,328		65,761
Loss (gain) on sale or disposal of other property, plant and equipment, net		—		1,300		1,300		(3,326	)
Contract termination and other restructuring costs		1,919		34		1,953		10,898
Restructuring, impairment and costs of terminated program	$	22,139	$	29,819	$	51,958	$	135,930


	2023 Restructuring Plan			2022 Restructuring Plan			Total
Liability balance as of December 31, 2021	$	—		$	—		$	—
Expense recognized during the period		—			30,904			30,904
Payments during the period		—			(27,605	)		(27,605	)
Liability balance as of December 31, 2022	$	—		$	3,299		$	3,299
Expense recognized during the period		7,885			—			7,885
Payments during the period		(7,689	)		(3,299	)		(10,988	)
Liability balance as of December 31, 2023	$	196		$	—		$	196

We recorded non-cash impairment charges of lease assets pertaining to the 2022 and 2023 Restructuring Plans as follows (in thousands):


	Three-months Ended
Sublease Spaces	June 30, 2022		September 30, 2022		December 31, 2022		March 31, 2023		June 30, 2023		September 30, 2023		December 31, 2023		Total
Mission Bay Blvd. South	$	3,000	$	1,200	$	361	$	—	$	7,061	$	1,467	$	—	$	13,089
Third St		49,200		—		12,000		—		6,200		—		—		67,400
Total 2022 Restructuring Plan		52,200		1,200		12,361		—		13,261		1,467		—		80,489
Mission Bay Blvd. South - 2023 Restructuring Plan	N/A		N/A		N/A			11,500		—		9,100		—		20,600
Total impairment of lease assets	$	52,200	$	1,200	$	12,361	$	11,500	$	13,261	$	10,567	$	—	$	101,089


	Year Ended December 31, 2022
	Operating Lease			Property, Plant and
	Right-of-Use Assets			Equipment			Total
Net book value of impaired sublease assets	$	72,481		$	16,348		$	88,829
Less: Fair value of impaired sublease assets — Level 3 of Fair Value Hierarchy		(16,174	)		(4,780	)		(20,954	)
Book value in excess of fair value		56,307			11,568			67,875
Less: Amounts recorded as amortization between June 30, 2022 and December 31, 2022 for Third St. facility		(1,717	)		(397	)		(2,114	)
Total impairment of sublease assets	$	54,590		$	11,171		$	65,761


	Year Ended December 31, 2023
	Operating Lease Right-of-Use Assets			Property, Plant and Equipment			Total
Net book value of impaired facilities before write-off	$	46,292		$	7,206		$	53,498
Less: Fair value of impaired facilities — Level 3 of Fair Value Hierarchy		(14,364	)		(2,172	)		(16,536	)
Book value in excess of fair value		31,928			5,034			36,962
Less: Amounts recorded as amortization between March 31, 2023 and September 30, 2023 for Mission Bay facility		(1,371	)		(263	)		(1,634	)
Total impairment of right-of-use assets and property, plant and equipment	$	30,557		$	4,771		$	35,328


	Year Ended
	December 31, 2023
Liability balance as of December 31, 2021	$	—
Expense recognized during the period		10,898
Payments during the period		(3,188	)
Liability balance as of December 31, 2022		7,710
Expense recognized during the period		1,919
Payments during the period		(4,087	)
Liability balance as of December 31, 2023	$	5,542

Schedule of Property, Plant and Equipment

Property, Plant and Equipment

Property, plant and equipment consists of the following (in thousands):


	December 31,
	2023			2022
Building and leasehold improvements	$	43,184		$	74,889
Laboratory equipment		14,537			24,243
Computer equipment and software		22,438			26,205
Manufacturing equipment		24,315			25,052
Furniture, fixtures, and other		541			4,263
Depreciable property, plant and equipment at cost		105,015			154,652
Less: accumulated depreciation		(86,898	)		(124,731	)
Depreciable property, plant and equipment, net		18,117			29,921
Construction-in-progress		739			2,530
Property, plant and equipment, net	$	18,856		$	32,451

We recorded the gains and losses as follows (in thousands):


	Year Ended December 31,
	2023		2022
Proceeds from sales	$	1,245	$	13,196
Net book value of assets		2,545		9,870
Total (gain) loss on sale or disposal of other property, plant and equipment, net	$	1,300	$	(3,326	)

Subsequent Events

12 Months Ended

Dec. 31, 2023

Subsequent Events [Abstract]

Subsequent Events

Note 13 — Subsequent Events

On March 4, 2024, we entered into a Securities Purchase Agreement with TCG Crossover Fund II, L.P. (TCG) wherein TCG agreed to purchase pre-funded warrants to purchase an aggregate 25,000,000 shares of Nektar’s common stock at a price of $1.20 per share for gross proceeds of $30.0 million. The closing of the purchase is expected to occur on or before March 6, 2024.

Operating Leases - Schedule of Maturities of Operating Lease Receivables from Subleases (Details) $ in Thousands	Dec. 31, 2023 USD ($)
Leases [Abstract]
2024	$ 1,360
2025	1,535
2026	1,589
2027	1,645
2028	1,702
2029 and thereafter	1,757
Gross Lease Receivable	$ 9,588

Co-Development Agreement with SFJ Pharmaceuticals and Development Derivative Liability - Schedule of Fair Value of Derivative Liability (Details) - Development Derivative Liability - Level 3 - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value as of December 31, 2021 and February 12, 2021 (inception), respectively	$ 27,726	$ 0
Non-cash research and development expense	4,951	16,703
Cash receipts from SFJ	750	3,000
Change in the fair value of development derivative liability	(33,427)	8,023
Fair value at end of period	$ 0	$ 27,726

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2023

Share-Based Payment Arrangement [Abstract]

Schedule of Common Stock Reserved for Future Issuance

As of December 31, 2023, shares of common stock reserved for future issuance are as follows (in thousands):


Stock options, RSUs and PSUs outstanding			27,246
Shares available for future grant under the 2017 Performance Incentive Plan			10,101
Shares available for issuance under the employee stock purchase plan			775
Total common stock reserved for issuance			38,122

Schedule of Stock-Based Compensation Expense

We recognize total stock-based compensation expense in our Consolidated Statements of Operations as follows (in thousands):


	Year Ended December 31,
	2023		2022		2021
Cost of goods sold	$	3,177	$	2,824	$	2,779
Research and development		13,890		27,727		54,821
General and administrative		16,321		24,488		37,074
Restructuring, impairment and costs of terminated program		—		2,281		—
Total stock-based compensation	$	33,388	$	57,320	$	94,674

Schedule of Black-Scholes Option-Pricing Model Assumptions Used to Calculate Fair Value of Employee Stock Options

The following table lists the Black-Scholes option-pricing model assumptions used to calculate the fair value of employee and director stock options, as well as the resulting grant-date fair value:


	Year Ended December 31,
	2023			2022			2021
Average risk-free interest rate		4.0	%		2.9	%		1.2	%
Dividend yield		0.0	%		0.0	%		0.0	%
Average volatility factor		88.4	%		77.9	%		63.8	%
Weighted-average expected life	5.1 years			5.6 years			5.5 years
Weighted-average grant-date fair value of options granted	$	0.37		$	3.18		$	8.07

Schedule of Stock Option Activity Under Equity Incentive Plans

The table below presents a summary of stock option activity under our equity incentive plans (in thousands, except for price per share and contractual life information):


						Weighted-
				Weighted-		Average
				Average		Remaining
	Number			Exercise		Contractual		Aggregate
	of			Price		Life		Intrinsic
	Shares			per Share		(in Years)		Value(1)
Outstanding at December 31, 2022		14,088		$	16.40
Options granted		11,854			0.51
Options exercised		—			—
Options forfeited & canceled		(2,926	)		16.07
Outstanding at December 31, 2023		23,016		$	8.26		6.42	$	—

Exercisable at December 31, 2023		6,425			22.99		3.68	$	—

(1)

Aggregate intrinsic value represents the difference between the exercise price of the option and the closing market price of our common stock on December 31, 2023.

Schedule of Restricted Stock Unit Award Activity

A summary of RSU award activity is as follows (in thousands except for per share amounts):


				Weighted-
				Average
				Grant
				Date Fair
	Units Issued			Value
Unvested at December 31, 2022		9,312		$	6.81
Granted		126			1.10
Vested and released		(2,759	)		7.93
Forfeited and canceled		(2,449	)		6.11
Unvested at December 31, 2023		4,230		$	6.14

Consolidated Financial Statement Details - Schedule of Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Inventory Disclosure [Abstract]
Accrued compensation	$ 5,553	$ 9,582
Accrued clinical trial expenses	4,321	12,262
Liability to collaboration partners	2,678	3,808
Accrued contract termination costs	3,020	3,902
Other accrued expenses	6,590	7,003
Total accrued expenses	$ 22,162	$ 36,557

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2023

Income Tax Disclosure [Abstract]

Schedule of Income Before Income Tax, Domestic and Foreign

Loss before provision for income taxes includes the following components (in thousands):


	Year Ended December 31,
	2023			2022			2021
Domestic	$	(274,998	)	$	(371,900	)	$	(524,440	)
Foreign		(1,258	)		6,917			1,160
Loss before provision for income taxes	$	(276,256	)	$	(364,983	)	$	(523,280	)

Schedule of Provision for Income Taxes

The provision for income taxes consists of the following (in thousands):


	Year Ended December 31,
	2023			2022			2021
Current:
Federal	$	—		$	—		$	—
State		(43	)		(608	)		50
Foreign		(17	)		1,115			609
Total current income tax expense		(60	)		507			659
Deferred:
Federal		—			—			—
State		—			—			—
Foreign		(140	)		2,708			(102	)
Total deferred income tax expense		(140	)		2,708			(102	)
Provision (benefit) for income taxes	$	(200	)	$	3,215		$	557

Schedule of Income Tax Provision Related to Continuing Operations

Our income tax provision related to continuing operations differs from the amount computed by applying the statutory income tax rate of 21% to our pretax loss as follows (in thousands):


	Year Ended December 31,
	2023			2022			2021
Income tax benefit at federal statutory rate	$	(58,013	)	$	(76,647	)	$	(109,889	)
Research credits		(1,192	)		(987	)		(4,727	)
Change in valuation allowance		35,033			51,108			97,914
Expiration of net operating loss carryforwards		312			12,348			286
Stock-based compensation		8,919			15,778			6,627
Non-cash interest expense on liability related to sales of future royalties		5,320			6,071			9,936
Non-cash royalty revenue related to sales of future royalties		(7,838	)		(7,112	)		(7,891	)
Loss on revaluation of liability related to the sale of future royalties		—			—			4,940
Impairment of goodwill		16,065			—			—
Other		1,194			2,656			3,361
Provision (benefit) for income taxes	$	(200	)	$	3,215		$	557

Schedule of Significant Components of Deferred Tax Assets and Liabilities

We measure deferred tax assets and liabilities based on the rates at which they are expected to reverse in the future. Significant components of our deferred tax assets for federal and state income taxes are as follows (in thousands):


	December 31,
	2023			2022
Deferred tax assets:
Net operating loss carryforwards	$	574,737		$	545,508
Research and other credits		144,128			142,198
Net capital loss carryforwards		39,655			38,445
Operating lease liabilities		25,384			28,254
Stock-based compensation		19,447			22,110
Capitalized research and development costs		34,675			24,134
Liability related to the sale of future royalties		6,729			13,424
Other		13,863			13,935
Deferred tax assets before valuation allowance		858,618			828,008
Valuation allowance for deferred tax assets		(854,528	)		(816,235	)
Total deferred tax assets		4,090			11,773
Deferred tax liabilities:
Operating lease right-of-use assets		(3,824	)		(11,335	)
Investment in foreign subsidiary		(521	)		(2,451	)
Other		(265	)		(392	)
Total deferred tax liabilities		(4,610	)		(14,178	)
Net deferred tax assets (liabilities)	$	(520	)	$	(2,405	)

Schedule of Unrecognized Tax Benefits

We have the following activity relating to unrecognized tax benefits (in thousands):


	Year Ended December 31,
	2023			2022			2021
Beginning balance	$	85,845		$	80,604		$	78,665
Tax positions related to current year:
Additions		848			378			2,371
Reductions		—			—			—
Tax positions related to prior years:
Additions		40,079			5,272			58
Reductions		—			—			(490	)
Settlements		—			—			—
Lapses in statute of limitations		(274	)		(409	)		—
Ending balance	$	126,498		$	85,845		$	80,604

Co-Development Agreement with SFJ Pharmaceuticals and Development Derivative Liability - Additional Information (Details) - SFJ	Feb. 12, 2021 USD ($)
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Committed funding (up to)	$ 150,000,000
Collaborative arrangement, success-based payments	$ 637,500,000

Consolidated Financial Statement Details - Schedule of Goodwill (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Goodwill [Roll Forward]
Goodwill - beginning balance	$ 76,501	$ 76,501
Impairment of goodwill	$ (76,500)	(76,501)	$ 0	$ 0
Goodwill - ending balance		$ 0	$ 76,501

- Definition

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References + Details

Stock-Based Compensation - Additional Information (Details)	12 Months Ended
	Dec. 31, 2023 USD ($) $ / shares shares	Dec. 31, 2022 USD ($) $ / shares	Dec. 31, 2021 USD ($) $ / shares	Jun. 08, 2022 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Change in control severance payment period for executives	12 months
Total unrecognized compensation costs	$ 33,100,000
Recognized over a weighted-average period	2 years 3 months 18 days
Dividend yield	0.00%	0.00%	0.00%
Total intrinsic value of options exercised	$ 0	$ 0	$ 17,300,000
Maximum 401(k) per employee, percentage of annual salary	60.00%
Matching 401(k) employer contribution, maximum amount	$ 12,000,000	12,000,000	6,000,000
Compensation expense in connection with 401(k) retirement plan	$ 1,500,000	$ 2,500,000	$ 3,600,000
2017 Performance Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized \| shares	51,200,000			12,000,000
Share-based compensation plan's share limit reduction for every one restricted stock unit granted	1.5
Stock options term under equity incentive plans	8 years
Number of common stock shares available for stock options grants (in shares) \| shares	10,101,000
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common stock shares available for stock options grants (in shares) \| shares	775,000
Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend yield	0.00%
Stock Option \| 2017 Performance Incentive Plan \| Employee \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Service period for stock-based compensation award granted	4 years
Stock Option \| 2017 Performance Incentive Plan \| Employee \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Service period for stock-based compensation award granted	3 years
Stock Option \| 2017 Performance Incentive Plan \| Director
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Service period for stock-based compensation award granted	1 year
RSUs and PSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in dollars per share) \| $ / shares	$ 1.10
RSUs and PSUs \| 2017 Performance Incentive Plan \| Employee
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Service period for stock-based compensation award granted	3 years
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Offering period	6 months
Employee Stock Purchase Plan \| Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Purchase price of common stock, percent	85.00%
Number of common stock shares available for stock options grants (in shares) \| shares	3,500,000
Restricted Stock Units (RSU)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in dollars per share) \| $ / shares	$ 1.10	$ 4.14	$ 14.68
Fair value of restricted stock vested	$ 3,600,000	$ 17,500,000	$ 45,300,000

Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Taxes Disclosure [Line Items]
Increase in valuation allowance	$ 38,300,000	$ 30,500,000
Operating loss carryforwards, subject to expiration	1,300,000,000
Income tax research credits	1,192,000	987,000	$ 4,727,000
Unrecognized tax benefits, interest recognized	0	0	0
Unrecognized tax benefits, penalties recognized	$ 0	$ 0	$ 0
Unrecognized tax benefits, period may increase or decrease due to tax examination	12 months
Federal
Income Taxes Disclosure [Line Items]
Operating loss carryforwards	$ 2,700,000,000
Income tax research credits	126,000,000
State
Income Taxes Disclosure [Line Items]
Operating loss carryforwards	700,000,000
Income tax research credits	$ 59,900,000