0000906709-21-000018 | 10-Q | XBRL Viewer

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Cover Page - shares	9 Months Ended
Cover Page - shares	Sep. 30, 2021	Oct. 29, 2021
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2021
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 Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		184,557,124
Amendment Flag	false
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Entity Central Index Key	0000906709
Current Fiscal Year End Date	--12-31

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 54,017	$ 198,955
Short-term investments	867,063	862,941
Accounts receivable	28,994	38,889
Inventory	15,330	15,292
Other current assets	20,731	21,928
Total current assets	986,135	1,138,005
Long-term investments	34,219	136,662
Property, plant and equipment, net	58,830	59,662
Operating lease right-of-use assets	119,714	126,476
Goodwill	76,501	76,501
Other assets	1,844	1,461
Total assets	1,277,243	1,538,767
Current liabilities:
Accounts payable	23,660	22,139
Accrued compensation	32,882	14,532
Accrued clinical trial expenses	37,633	44,207
Accrued contract manufacturing expenses	8,088	11,310
Other accrued expenses	19,966	9,676
Operating lease liabilities, current portion	17,740	13,915
Total current liabilities	139,969	115,779
Operating lease liabilities, less current portion	128,718	136,373
Development derivative liability	21,387	0
Liabilities related to the sales of future royalties, net	181,760	200,340
Other long-term liabilities	3,869	8,980
Total liabilities	475,703	461,472
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $0.0001 par value; 10,000 shares authorized; no shares designated or outstanding at September 30, 2021 or December 31, 2020	0	0
Common stock, $0.0001 par value; 300,000 shares authorized; 184,554 shares and 180,091 shares outstanding at September 30, 2021 and December 31, 2020, respectively	18	18
Capital in excess of par value	3,492,435	3,388,730
Accumulated other comprehensive loss	(3,563)	(2,295)
Accumulated deficit	(2,687,350)	(2,309,158)
Total stockholders’ equity	801,540	1,077,295
Total liabilities and stockholders’ equity	$ 1,277,243	$ 1,538,767

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Sep. 30, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars 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 outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	300,000,000	300,000,000
Common stock, shares outstanding (in shares)	184,554,000	180,091,000

Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Revenue:
Total revenue	$ 24,921	$ 30,033	$ 76,898	$ 129,453
Operating costs and expenses:
Cost of goods sold	5,311	5,570	18,734	15,154
Research and development	103,738	100,531	300,655	305,954
General and administrative	29,468	26,982	90,702	77,546
Impairment of assets and other costs for terminated program	0	0	0	45,189
Total operating costs and expenses	138,517	133,083	410,091	443,843
Loss from operations	(113,596)	(103,050)	(333,193)	(314,390)
Non-operating income (expense):
Non-cash interest expense on liabilities related to sales of future royalties	(12,801)	(8,425)	(39,186)	(22,084)
Change in fair value of development derivative liability	(3,328)	0	(7,640)	0
Interest income and other income (expense), net	131	2,910	2,388	16,453
Interest expense	0	0	0	(6,851)
Total non-operating income (expense), net	(15,998)	(5,515)	(44,438)	(12,482)
Loss before provision for income taxes	(129,594)	(108,565)	(377,631)	(326,872)
Provision for income taxes	112	21	561	365
Net loss	$ (129,706)	$ (108,586)	$ (378,192)	$ (327,237)
Basic net loss per share (in dollars per share)	$ (0.70)	$ (0.61)	$ (2.07)	$ (1.84)
Diluted net loss per share (in dollars per share)	$ (0.70)	$ (0.61)	$ (2.07)	$ (1.84)
Weighted average shares outstanding used in computing basic net loss per share (in shares)	184,110	179,090	182,736	178,203
Weighted average shares outstanding used in computing diluted net loss per share (in shares)	184,110	179,090	182,736	178,203
Product sales
Revenue:
Total revenue	$ 5,194	$ 5,691	$ 17,835	$ 14,620
Royalty revenue
Revenue:
Total revenue	0	12,289	0	31,411
Non-cash royalty revenue related to sales of future royalties
Revenue:
Total revenue	19,413	10,422	58,667	28,001
License, collaboration and other revenue
Revenue:
Total revenue	$ 314	$ 1,631	$ 396	$ 55,421

Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Statement of Comprehensive Income [Abstract]
Net loss	$ (129,706)	$ (108,586)	$ (378,192)	$ (327,237)
Other comprehensive income (loss):
Net unrealized gain (loss) on available-for-sale investments	(176)	(2,144)	(1,006)	423
Net foreign currency translation gain (loss)	13	349	(262)	(498)
Other comprehensive income (loss)	(163)	(1,795)	(1,268)	(75)
Comprehensive loss	$ (129,869)	$ (110,381)	$ (379,460)	$ (327,312)

- Definition

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

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- Definition

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

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Condensed Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Shares	Capital in Excess of Par Value	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2019		176,505
Beginning balance at Dec. 31, 2019	$ 1,405,391	$ 17	$ 3,271,097	$ (1,005)	$ (1,864,718)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under equity compensation plans (in shares)		1,358
Shares issued under equity compensation plans	11,347		11,347
Stock-based compensation	24,211		24,211
Comprehensive income (loss)	(144,523)			(5,872)	(138,651)
Ending balance (in shares) at Mar. 31, 2020		177,863
Ending balance at Mar. 31, 2020	1,296,426	$ 17	3,306,655	(6,877)	(2,003,369)
Beginning balance (in shares) at Dec. 31, 2019		176,505
Beginning balance at Dec. 31, 2019	1,405,391	$ 17	3,271,097	(1,005)	(1,864,718)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income (loss)	(327,312)
Ending balance (in shares) at Sep. 30, 2020		179,394
Ending balance at Sep. 30, 2020	1,170,981	$ 18	3,363,998	(1,080)	(2,191,955)
Beginning balance (in shares) at Mar. 31, 2020		177,863
Beginning balance at Mar. 31, 2020	1,296,426	$ 17	3,306,655	(6,877)	(2,003,369)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under equity compensation plans (in shares)		947
Shares issued under equity compensation plans	7,826	$ 1	7,825
Stock-based compensation	24,396		24,396
Comprehensive income (loss)	(72,408)			7,592	(80,000)
Ending balance (in shares) at Jun. 30, 2020		178,810
Ending balance at Jun. 30, 2020	1,256,240	$ 18	3,338,876	715	(2,083,369)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under equity compensation plans (in shares)		584
Shares issued under equity compensation plans	1,455	$ 0	1,455
Stock-based compensation	23,667		23,667
Comprehensive income (loss)	(110,381)			(1,795)	(108,586)
Ending balance (in shares) at Sep. 30, 2020		179,394
Ending balance at Sep. 30, 2020	1,170,981	$ 18	3,363,998	(1,080)	(2,191,955)
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)		2,199
Shares issued under equity compensation plans	17,106		17,106
Stock-based compensation	23,898		23,898
Comprehensive income (loss)	(123,793)			(826)	(122,967)
Ending balance (in shares) at Mar. 31, 2021		182,290
Ending balance at Mar. 31, 2021	994,506	$ 18	3,429,734	(3,121)	(2,432,125)
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]
Comprehensive income (loss)	(379,460)
Ending balance (in shares) at Sep. 30, 2021		184,554
Ending balance at Sep. 30, 2021	801,540	$ 18	3,492,435	(3,563)	(2,687,350)
Beginning balance (in shares) at Mar. 31, 2021		182,290
Beginning balance at Mar. 31, 2021	994,506	$ 18	3,429,734	(3,121)	(2,432,125)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under equity compensation plans (in shares)		1,483
Shares issued under equity compensation plans	12,553		12,553
Stock-based compensation	23,714		23,714
Comprehensive income (loss)	(125,798)			(279)	(125,519)
Ending balance (in shares) at Jun. 30, 2021		183,773
Ending balance at Jun. 30, 2021	904,975	$ 18	3,466,001	(3,400)	(2,557,644)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under equity compensation plans (in shares)		781
Shares issued under equity compensation plans	1,777	$ 0	1,777
Stock-based compensation	24,657		24,657
Comprehensive income (loss)	(129,869)			(163)	(129,706)
Ending balance (in shares) at Sep. 30, 2021		184,554
Ending balance at Sep. 30, 2021	$ 801,540	$ 18	$ 3,492,435	$ (3,563)	$ (2,687,350)

- Definition

Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(g)(1)(ii))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 852
-SubTopic 10
-Section 55
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=84165509&loc=d3e56426-112766

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 4.E)
-URI http://asc.fasb.org/extlink&oid=122038336&loc=d3e74512-122707

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(31))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(30))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 7: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 28
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=123596393&loc=d3e14064-108612

Reference 8: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

+ Details

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Cash flows from operating activities:
Net loss	$ (378,192)	$ (327,237)
Adjustments to reconcile net loss to net cash used in operating activities:
Non-cash royalty revenue related to sales of future royalties	(58,667)	(28,001)
Non-cash interest expense on liabilities related to sales of future royalties	39,186	22,084
Change in fair value of development derivative liability	7,640	0
Non-cash research and development expense	11,497	0
Stock-based compensation	72,269	72,274
Depreciation and amortization	10,710	10,937
Impairment of advance payments to contract manufacturers and equipment for terminated program	0	20,351
Amortization of premiums (discounts), net and other non-cash transactions	5,677	1,150
Changes in operating assets and liabilities:
Accounts receivable	9,895	(6,123)
Inventory	(38)	(227)
Operating leases, net	2,932	4,316
Other assets	814	(5,588)
Accounts payable	1,247	(3,337)
Accrued compensation	18,350	20,478
Other accrued expenses	(3,837)	9,340
Deferred revenue	(605)	(5,070)
Net cash used in operating activities	(261,122)	(214,653)
Cash flows from investing activities:
Purchases of investments	(816,049)	(791,445)
Maturities of investments	902,687	1,158,722
Sales of investments	5,035	41,700
Purchases of property, plant and equipment	(9,093)	(5,504)
Net cash provided by investing activities	82,580	403,473
Cash flows from financing activities:
Proceeds from shares issued under equity compensation plans	31,436	20,651
Cash receipts from development derivative liability	2,250	0
Repayment of senior notes	0	(250,000)
Net cash provided by (used in) financing activities	33,686	(229,349)
Effect of foreign exchange rates on cash and cash equivalents	(82)	9
Net decrease in cash and cash equivalents	(144,938)	(40,520)
Cash and cash equivalents at beginning of period	198,955	96,363
Cash and cash equivalents at end of period	54,017	55,843
Supplemental disclosures of cash flow information:
Cash paid for interest	0	9,742
Operating lease right-of-use asset recognized in exchange for lease liabilities	$ 1,057	$ 2,133

Organization and Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Summary of Significant Accounting Policies	Organization and Summary of Significant Accounting Policies Organization We are a research-based biopharmaceutical company headquartered in San Francisco, California and incorporated in Delaware. We are developing a pipeline of drug candidates that leverage our proprietary and proven advanced polymer conjugate technology platforms, which are designed to enable the development of new molecular entities that target known mechanisms of action. Our research and development pipeline of new investigational drugs includes potential therapies for oncology, immunology and virology. 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 September 30, 2021, we had approximately $955.3 million in cash and investments in marketable securities. Basis of Presentation and Principles of Consolidation Our Condensed Consolidated Financial Statements include the financial position, results of operations and cash flows of our wholly-owned subsidiaries: Inheris Biopharma, Inc., Nektar Therapeutics (India) Private Limited (Nektar India), Nektar Therapeutics Europe GmbH, and certain other entities in Europe. We have eliminated all intercompany accounts and transactions in consolidation. We prepared our Condensed Consolidated Financial Statements following the requirements of the Securities and Exchange Commission (SEC) for interim reporting. As permitted under those rules, we may condense or omit certain footnotes or other financial information that are normally required by U.S. generally accepted accounting principles (GAAP) for annual periods. In the opinion of management, these financial statements include all normal and recurring adjustments that we consider necessary for the fair presentation of our financial position and operating results. Our Condensed 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 Condensed Consolidated Balance Sheets. To date, such cumulative currency translation adjustments have not been significant to our consolidated financial position. 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. There were no significant reclassifications out of accumulated other comprehensive loss to the statements of operations during the three and nine months ended September 30, 2021 and 2020. The accompanying Condensed Consolidated Financial Statements are unaudited. The Condensed Consolidated Balance Sheet data as of December 31, 2020 was derived from the audited consolidated financial statements which are included in our Annual Report on Form 10-K for the year ended December 31, 2020 filed with the SEC on February 26, 2021. The information included in this Quarterly Report on Form 10-Q should be read in conjunction with the consolidated financial statements and the accompanying notes to those financial statements included in our Annual Report on Form 10-K for the year ended December 31, 2020. Revenue, expenses, assets, and liabilities can vary during each quarter of the year. The results and trends in these interim Condensed Consolidated Financial Statements are not necessarily indicative of the results to be expected for the full year or any other period. Use of Estimates The preparation of consolidated financial statements in conformity with 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. As appropriate, we assess our estimates each period, update them to reflect current information and generally recognize any changes in such estimates in the period first identified. Reclassifications Certain items previously reported in specific financial statement captions have been reclassified to conform to the current period presentation. Such reclassifications do not materially impact previously reported revenue, operating loss, net loss, total assets, liabilities or stockholders’ equity. Segment Information We operate in one business segment which focuses on applying our technology platform 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. Significant Concentrations Our customers are primarily pharmaceutical and biotechnology companies that are 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), and other contingent payments, as well as reimbursable costs from collaborative research and development agreements. As of September 30, 2021, our accounts receivable includes $24.9 million for unbilled net expense reimbursements from our collaboration partner Bristol-Myers Squibb Company (BMS) and $3.1 million under customer contracts from our collaboration partners. As of December 31, 2020, our accounts receivable included $38.7 million for unbilled net expense reimbursements from BMS and $0.2 million from customer contracts. We generally do not require collateral from our customers. We perform a regular review of our customers’ credit risk and payment histories, including payments made after period end. Historically, we have not experienced credit losses from our accounts receivable and recorded no bad debt expense for the three and nine months ended September 30, 2021 and 2020. We have not recorded a reserve for credit losses at September 30, 2021 or December 31, 2020. 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, including as a result of the COVID-19 pandemic, our ability to develop and produce our drug candidates, our ability to supply comparator drugs for our clinical trials, 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. 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 deterioration in this industry could have a material effect on our results of operations and financial position. 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, including the effects of the COVID-19 pandemic, result in downgrades below our minimum credit rating requirements and if we decide to sell these securities, we may experience losses on such sales. 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 proprietary 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 proprietary 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 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 invoice. We test our products for adherence to technical specifications before shipment; accordingly, we have not experienced any significant returns from our customers. 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. As of December 30, 2020, 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, including for our non-cash royalties, when the underlying sales occur based on our best estimates of sales of the drugs. Our partners generally pay royalties or commercial milestones after the end of the calendar quarter in accordance with contractual terms. 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 after 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 for our proprietary drug candidates and technology development and for certain third parties under collaboration agreements. For our proprietary 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 costs of our clinical trial 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 accrue costs associated with the start-up and reporting phases of the clinical trials ratably over the estimated duration of the start-up and reporting phases. We generally accrue costs associated with the treatment phase of clinical trials based on the estimated activities performed by third parties. 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 based on patient enrollment in the trials. In specific circumstances, such as for certain time-based costs, we recognize clinical trial expenses using a methodology that we consider to be more reflective of the timing of costs incurred. We record an accrued expense for the estimated costs of our contract manufacturing 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 include upfront payments and milestone payments, which depend on factors such as the achievement of the completion of certain stages of the manufacturing process. For purposes of recognizing expense, we assess whether we consider the production process is sufficiently defined such that the resulting product can be considered the delivery of a good, as evidenced by predictive or contractually required yields in the production process or payment terms based on the actual yield, or the delivery of a service, where processes and yields are developing and less certain. If we consider the process to be the delivery of a good, we recognize expense when the drug product is delivered, or we otherwise bear risk of loss. If we consider the process to be the delivery of a service, we recognize expense based on our best estimates of the contract manufacturer’s progress towards completion of the stages in the contracts. We recognize and amortize upfront payments and accrue liabilities based on the specific terms of each arrangement. Certain arrangements may provide upfront payments for certain stages of the arrangement and milestone payments for the completion of certain stages, and, accordingly, we may record advance payments for services that have not been completed or goods not delivered and liabilities for stages where the contract manufacturer is entitled to a milestone payment. 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. Impairment of Assets and Other Costs for Terminated Program On January 14, 2020, the joint FDA Anesthetic Drug Products Advisory Committee and Drug Safety and Risk Management Committee did not recommend approval of our New Drug Application (NDA) for NKTR-181. As a result, we withdrew our NDA and decided to make no further investments in this program. As a result, in the three months ended March 31, 2020, we wrote off $19.7 million of advance payments to contract manufacturers for commercial batches of NKTR-181. We also incurred $25.5 million of additional costs, primarily for non-cancellable commitments to our contract manufacturers and certain severance costs. We present these costs in the Impairment of assets and other costs for terminated program line in our Condensed Consolidated Statement of Operations. Income Taxes For the three and nine months ended September 30, 2021 and 2020, our income tax expense primarily results from our foreign operations. We have fully reserved our U.S. federal deferred tax assets generated from our net operating losses, as we believe it is not more likely than not that the benefit will be realized. Shelf Registration We currently have an effective shelf registration statement on Form S-3 (the 2021 Shelf Registration Statement) on file with the SEC, which expires in March 2024. The 2021 Shelf Registration Statement currently permits the offering, issuance and sale by us of up to an aggregate offering price of $300.0 million of common stock, preferred stock, debt securities and warrants in one or more offerings and in any combination, all of which may be offered, issued and sold in “at-the-market” sales pursuant to an equity distribution agreement with Cowen and Company, LLC (the Equity Distribution Agreement). No securities have been sold under the 2021 Shelf Registration Statement or the Equity Distribution Agreement.

Cash and Investments in Marketable Securities

9 Months Ended

Sep. 30, 2021

Fair Value Disclosures [Abstract]

Cash and Investments in Marketable Securities

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


	Estimated Fair Value at
	September 30, 2021		December 31, 2020
Cash and cash equivalents	$	54,017	$	198,955
Short-term investments	867,063		862,941
Long-term investments	34,219		136,662
Total cash and investments in marketable securities	$	955,299	$	1,198,558

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. As of September 30, 2021 and December 31, 2020, all of our long-term investments had maturities between one and two years.

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


	September 30, 2021								December 31, 2020
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value		Fair Value
Corporate notes and bonds	$	329,376	$	53	$	(90)	$	329,339	$	687,469
Corporate commercial paper	555,989		35		(100)		555,924		313,497
Obligations of U.S. government agencies	5,880		2		—		5,882		2,382
Available-for-sale investments	$	891,245	$	90	$	(190)	$	891,145	$	1,003,348
Money market funds							48,336		179,302
Certificates of deposit							10,137		9,623
Cash							5,681		6,285
Total cash and investments in marketable securities							$	955,299	$	1,198,558

At December 31, 2020, our gross unrealized gains and losses totaled $1.1 million and $0.2 million, respectively.

Inventory

9 Months Ended

Sep. 30, 2021

Inventory Disclosure [Abstract]

Inventory

InventoryInventory consists of the following (in thousands):


	September 30, 2021		December 31, 2020
Raw materials	$	1,744	$	2,422
Work-in-process	9,388		10,703
Finished goods	4,198		2,167
Total inventory	$	15,330	$	15,292

We manufacture finished goods inventory upon receipt of firm purchase orders, and we may manufacture certain intermediate work-in-process materials and purchase raw materials based on purchase forecasts from our collaboration partners. We include direct materials, direct labor, and manufacturing overhead in inventory and 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 as manufactured by us or when purchased. Before the regulatory approval of our drug candidates, we recognize research and development expense for the manufacture of drug products that could potentially be available to support the commercial launch of our drug candidates, if approved.

Co-Development Agreement with SFJ Pharmaceuticals and Development Derivative Liability

9 Months Ended

Sep. 30, 2021

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Co-Development Agreement with SFJ Pharmaceuticals and Development Derivative Liability

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 will pay up to $150.0 million in committed funding to support a Phase 2/3 study of bempegaldesleukin in combination with Keytruda® (pembrolizumab) for first-line treatment of patients with metastatic or unresectable recurrent squamous cell carcinoma of the head and neck (the SCCHN Clinical Trial) whose tumors express PD-L1 (the SCCHN Indication). SFJ Pharmaceuticals is a global drug development company backed by Blackstone Life Sciences and Abingworth. On February 11, 2021, we entered into a collaboration agreement with MSD International GmbH (MSD), an affiliate of Merck, Sharp & Dohme, pursuant to which MSD will provide Keytruda® at no cost for use in the SCCHN Clinical Trial but will not bear any other costs of the trial.

SFJ will have primary responsibility for the clinical trial management of the SCCHN Clinical Trial, and we will be the sponsor of the SCCHN Clinical Trial and will also have sole responsibility for regulatory interactions and filings for bempegaldesleukin. The SCCHN Clinical Trial provides for an interim futility analysis, and unless the futility criteria are met, SFJ is required to complete the SCCHN Trial, but if the futility criteria are met, SFJ has the responsibility to wind down the SCCHN Clinical Trial at its sole cost. We and BMS, pursuant to the BMS Collaboration Agreement, remain solely responsible for conducting the Phase 3 clinical trials of bempegaldesleukin in combination with Opdivo®, including the treatment of previously untreated unresectable or metastatic melanoma (the “Melanoma Indication” and the “Melanoma Clinical Trial”).

Other than the opportunity to receive Success Payments as outlined below, SFJ has no right to reimbursement of costs incurred by SFJ for the SCCHN Clinical Trial in the event that the Melanoma Clinical Trial and the SCCHN Clinical Trial do not achieve FDA approval. We will pay SFJ a series of success-based annual payments (collectively, the Success Payments) in the event of FDA approval of bempegaldesleukin for the Melanoma Indication, the SCCHN Indication, or both, and in the event of FDA approval of one additional bempegaldesleukin indication. The Success Payments do not begin until the substantial completion of the SCCHN Clinical Trial. The total success-based annual payments for the first indication approved by FDA, whether for the Melanoma Indication or the SCCHN Indication, is an aggregate of $450.0 million, paid in annual contractual payments over five years, with the first payment being $30.0 million, with the earliest possible payment expected to occur in late 2024 or early 2025, subject to the substantial completion of the SCCHN Clinical Trial. The total success-based payments for the second indication approved by FDA, whether for the Melanoma Indication or the SCCHN Indication, is an aggregate of $150.0 million, paid in annual contractual payments over seven years. Finally, in the event of FDA approval for bempegaldesleukin for any indication other than the Melanoma Indication or the SCCHN Indication, we will make a one-time payment of $37.5 million to SFJ. If the success criterion for the interim futility analysis is not met and SFJ winds down the SCCHN Clinical Trial, then the Success Payments, if any, for the Melanoma Indication and/or the additional bempegaldesleukin indication are reduced pro rata based on the costs incurred by SFJ for the SCCHN Clinical Trial over the aggregate commitment of $150.0 million.

The SFJ Agreement provides for certain positive and negative covenants, including restrictions on our ability to incur liens on our intellectual property related to bempegaldesleukin (the bempegaldesleukin IP), or assign or convey any right to receive income with respect to the bempegaldesleukin IP (other than royalty and other license fee obligations to licensors), except for the issuance of senior secured debt secured by all or substantially all of our assets, including the bempegaldesleukin IP.

The SFJ Agreement expires upon the payment of all Success Payments to SFJ, unless earlier terminated as provided under the SFJ Agreement. The SFJ Agreement may be terminated by either party for a safety or health concern for the patients, whether by the independent data monitoring company or by mutual agreement of both parties. The SFJ Agreement may also be terminated by either party for material breach or insolvency of the counterparty.

We present the SFJ Agreement as development derivative liability in our Condensed Consolidated Balance Sheets, which we remeasure to fair value at each reporting date. As SFJ conducts the SCCHN Clinical Trial, we record non-cash research and development expense with a corresponding increase to the development derivative liability, and as SFJ remits funding to us to support our internal costs of conducting the trial, we also record a corresponding increase to the development derivative liability. We present the gain (loss) from the remeasurement as Change in fair value of development derivative liability in our Condensed Consolidated Statement of Operations. The following table presents the changes in the development derivative liability for the three and nine months ended September 30, 2021:


	Three Months Ended September 30, 2021		Nine Months Ended September 30, 2021
Fair value at beginning of period	$	11,607	$	—
Non-cash research and development expense	5,702		11,497
Cash receipts from SFJ	750		2,250
Change in the fair value of development derivative liability	3,328		7,640
Fair value at end of period	$	21,387	$	21,387

We valued the derivative using a scenario-based discounted cash flow method, whereby each scenario makes assumptions about the probability and timing of cash flows, and we discount such cash flows to present value using a risk-adjusted rate. The key inputs to the valuation include our estimates of the following: (i) the probability and timing of achieving FDA approval in the Melanoma Indication, the SCCHN Indication and any other bempegaldesleukin indication, (ii) the timing of the substantial completion of the SCCHN Clinical Trial that SFJ must achieve before receiving a Success Payment, (iii) the probability of termination of the study due to meeting the interim futility criteria, (iv) the amount of costs incurred by SFJ if the success criterion for the interim futility analysis is not met, (v) SFJ’s cost of borrowing (1.0%), and (vi) the Company’s imputed cost of borrowing for debt with similar terms (12.2%).

Liabilities Related to Sales of Future Royalties

9 Months Ended

Sep. 30, 2021

Other Liabilities Disclosure [Abstract]

Liabilities Related to Sales of Future RoyaltiesOn 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 to RPI 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 Pharma, 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 sale of the 2012 Transaction Royalties. As part of this sale, we incurred approximately $4.4 million in transaction costs, which are amortized to interest expense over the estimated life of the 2012 Purchase and Sale Agreement. 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 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.

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. Because 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, UCB and we entered into a Settlement Agreement, effective as of October 13, 2021. We are still evaluating the effect of this agreement on our Consolidated Financial Statements. However, the reduction in the royalty term and royalty rate has no effect on our cash flows as we previously sold our right to receive these royalty payments to RPI pursuant to the 2012 Purchase and Sale Agreement.

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 sold 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 certain aggregate royalty payment 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 (AstraZeneca), 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 (collectively, Novo Nordisk) and (d) licensed products under that certain Right to Sublicense Agreement, dated October 27, 2017, by and among Nektar, Baxter Incorporated, Baxalta US Inc. and Baxalta GmbH.

The 2020 Purchase and Sale Agreement will automatically expire, and the payment of the 2020 Transaction Royalties to HCR will cease, when HCR has 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). If HCR has received payments of the 2020 Transaction Royalties equal to at least $208.0 million on or prior to December 31, 2025, we have the option to pay the difference between the 2025 Threshold and such 2020 Transaction Royalties, and the 2025 Threshold will be met and the 2020 Purchase and Sale Agreement will expire. After the 2020 Purchase and Sale Agreement expires, all rights to receive the 2020 Transaction Royalties return to Nektar.

On December 30, 2020, we received aggregate cash proceeds of $150.0 million for the sale of the 2020 Transaction Royalties. As part of the sale, we incurred approximately $3.8 million in transaction costs, which are amortized to interest expense over the estimated life of the 2020 Purchase and Sale Agreement. Although we sold all of our rights to receive royalties from these products, 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 continue to account for these non-cash royalties as revenue, commencing with royalties for the three months ended December 31, 2020, which HCR received in the three months ended March 31, 2021. We recorded the $150.0 million in proceeds from this transaction as a liability (the 2020 Royalty Obligation) that is amortized using the effective interest method over the estimated life of the 2020 Purchase and Sale Agreement.

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. The sum of these amounts less the net proceeds we received will be recorded as non-cash interest expense over the lives of the respective Royalty Obligations. 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 will prospectively adjust the imputed interest rate and the related amortization of the applicable Royalty Obligation.

The following table presents our estimates of the annual interest rates over the lives of the agreements and the resulting prospective interest rates used to recognize non-cash interest expense for the three and nine months ended September 30, 2021 and 2020.


	2012 Purchase and Sale Agreement				2020 Purchase and Sale Agreement
	Three and nine months ended September 30,				Three and nine months ended September 30,
	2021		2020		2021
Interest rates - end of period presented
Implicit interest rate over the life of the agreement	20.2	%	20.2	%	16.0	%
Prospective effective interest rate	48.0	%	48.0	%	16.0	%

In addition, the 2012 and 2020 Purchase and Sale Agreements grant RPI and HCR, respectively, the right to receive certain reports and other information relating to the 2012 and 2020 Transaction Royalties, respectively, and contain other representations and warranties, covenants and indemnification obligations that are customary for transactions of this nature. To our knowledge, we are currently in compliance with these provisions of the 2012 and 2020 Purchase and Sale Agreements; however, if we were to breach our obligations, we could be required to pay damages to RPI and HCR, respectively, that are not limited to the purchase prices we received in the sale 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.

Commitments and Contingencies	9 Months Ended
Commitments and Contingencies	Sep. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Legal Matters From time to time, we are involved in lawsuits, arbitration, 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 of that period and on our cash flows and liquidity. In October 2018, we and certain of our executives were named in a putative securities class action complaint filed in the U.S. District Court for the Northern District of California (Case No. 18-cv—66-7-HSG, which we refer to as the Mulquin action). The Mulquin plaintiffs have challenged public statements Nektar made, between January 2017 and June 2018, about the clinical trials of bempegaldesleukin. The Mulquin complaint was amended in May 2019. The defendants moved to dismiss and the court granted the motion without prejudice in July 2020. The Mulquin plaintiffs again amended their complaint and the defendants again moved to dismiss. In December 2020, the court dismissed the action with prejudice. The plaintiffs filed a notice of appeal in January 2021 and appellate briefing in the U.S. Court of Appeals for the Ninth Circuit was completed in September 2021. Oral argument is scheduled for December 10, 2021. A second putative securities class action was filed against the Company and certain of our executives in the U.S. District Court for the Northern District of California in August 2019 (Case No. 4-19-cv-05173, which we refer to as the Damiba action). The Damiba plaintiffs challenged public statements Nektar made, between February 2019 and May 2019, about its bempegaldesleukin clinical trials and collaboration with Bristol-Myers Squibb. After the Damiba plaintiffs filed an amended complaint and the defendants moved to dismiss, the court dismissed the action without prejudice in January 2021. The Damiba plaintiffs subsequently voluntarily dismissed the action, with prejudice, in March 2021. In addition to the two securities actions (the Mulquin action and the Damiba action), three sets of derivative actions have been filed against certain of the Company’s current and former officers and directors, purportedly on the Company’s behalf. These derivative actions are based on the allegations in the securities actions and on the premise that the Company’s officers and directors breached their fiduciary duties by exposing the Company to one or both of the securities actions. The first derivative action was filed in the U.S. District Court for the District of Delaware in February 2019 (Case No. 1:19-cv-00322-MN-JLH). After amending their complaint several times, the plaintiffs in that action voluntarily dismissed their claims without prejudice in April 2021. A second set of derivative actions was filed in February 2020 in the U.S. District Court for the Northern District of California (Case No. 4:20-cv-01088-JSW). The derivative actions in California were consolidated and the Company moved to dismiss on the basis that the plaintiffs had neither made a demand on the Company’s board of directors nor shown that a demand would be futile. On September 1, 2021, the court dismissed the action with prejudice. A third derivative complaint was filed in February 2021 in the Court of Chancery of the State of Delaware (C.A. No. 2021-0118-PAF). The parties agreed to stay further proceedings in this action until thirty days after the U.S. Court of Appeals for the Ninth Circuit’s final resolution of the appeal in the Mulquin action. Given the nature and status of these securities class action lawsuits and derivative complaints, we cannot reasonably estimate a potential future loss or a range of potential future losses. However, an unfavorable resolution could potentially have a material adverse effect on our business, financial condition, and results of operations or prospects, and potentially result in paying monetary damages. We have recorded no liability for these matters in our Condensed Consolidated Balance Sheets at either September 30, 2021 or December 31, 2020. 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 any time 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, including our obligation to RPI described in Note 5. In the event it is determined that we breached certain of the representations and warranties or covenants made by us in any such agreements, we could incur substantial indemnification liabilities depending on the timing, nature, and amount of any such claims. To date, we have not incurred costs to defend lawsuits or settle claims related to these indemnification obligations, representations or warranties. 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. We have recorded no liabilities for these obligations in our Condensed Consolidated Balance Sheets at either September 30, 2021 or December 31, 2020.

Fair Value Measurement

9 Months Ended

Sep. 30, 2021

Fair Value Disclosures [Abstract]

Fair Value Measurement

The following table presents information about our assets and liabilities that are measured at fair value on a recurring basis and indicates the level of the fair value hierarchy and the valuation techniques we utilized to determine such fair value:


	As of September 30, 2021
	Level 1		Level 2		Level 3		Total
Assets:
Corporate notes and bonds	$	—	$	329,339	$	—	$	329,339
Corporate commercial paper	—		555,924		—		555,924
Obligations of U.S. government agencies	—		5,882		—		5,882
Money market funds	48,336		—		—		48,336
Total assets	$	48,336	$	891,145	$	—	$	939,481
Liabilities:
Development derivative liability	$	—	$	—	$	21,387	$	21,387


	As of December 31, 2020
	Level 1		Level 2		Level 3		Total
Assets:
Corporate notes and bonds	$	—	$	687,469	$	—	$	687,469
Corporate commercial paper	—		313,497		—		313,497
Obligations of U.S. government agencies	—		2,382		—		2,382
Money market funds	179,302		—		—		179,302
Total assets	179,302		$	1,003,348	$	—	$	1,182,650
Liabilities:
Development derivative liability	$	—	$	—	$	—	$	—

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.

We use a market approach to value our Level 2 investments. The disclosed fair value related to our investments is based on market prices from a variety of industry standard data providers and generally represents quoted prices for similar assets in active markets or has been derived from observable market data. For the nine months ended September 30, 2021, 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. For the reconciliation of the changes in the development derivative liability and the description of the significant inputs used in estimating its fair value, see Note 4.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

License and Collaboration Agreements

9 Months Ended

Sep. 30, 2021

License And Collaboration Agreements [Abstract]

License and Collaboration Agreements

License and Collaboration AgreementsWe 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, and, if so, we analyze whether we should account for any elements under ASC 606.

In accordance with our collaboration agreements, we recognized license, collaboration and other revenue as follows (in thousands):


		Three months ended September 30,				Nine months ended September 30,
Partner	Drug or Drug Candidate	2021		2020		2021		2020
Bristol-Myers Squibb Company	Bempegaldesleukin	$	—	$	—	$	—	$	50,000
Eli Lilly and Company	NKTR-358	—		—		—		1,259
Other		314		1,631		396		4,162
Total license, collaboration and other revenue		$	314	$	1,631	$	396	$	55,421

During the three and nine months ended September 30, 2021, we recognized $19.4 million and $58.7 million, respectively, of revenue for performance obligations that we had satisfied in prior periods. During the three and nine months ended September 30, 2020, we recognized $22.7 million and $109.4 million, respectively, of revenue for performance obligations that we had satisfied in prior periods. These amounts include all of our royalty revenue and non-cash royalty revenue, as well as the $50.0 million in milestones, respectively, recognized under our BMS Collaboration Agreement during the nine months ended September 30, 2020, as further described below, because we had previously completed our performance obligations of granting the licenses.

As of September 30, 2021, our collaboration agreements with partners included potential future payments for development and regulatory milestones totaling approximately $1.7 billion, including amounts from our agreements with BMS and Eli Lilly and Company described below. In addition, under our collaboration agreements we are entitled to receive contingent sales milestone payments, other contingent payments and royalty payments, as described below.

There have been no material changes to our collaboration agreements in the three and nine months ended September 30, 2021.

Bristol-Myers Squibb Company (BMS): Bempegaldesleukin, also referred to as NKTR-214

On February 13, 2018, we entered into a Strategic Collaboration Agreement (the BMS Collaboration Agreement) and a Share Purchase Agreement with BMS, both of which became effective on April 3, 2018. Pursuant to the BMS Collaboration Agreement, we and BMS are jointly developing bempegaldesleukin, including, without limitation, in combination with BMS’s Opdivo® (nivolumab), and other compounds of BMS, ours or any third party. The parties have agreed to jointly commercialize bempegaldesleukin on a worldwide basis. We retained the right to record all worldwide sales for bempegaldesleukin. We will share global commercialization profits and losses with BMS for bempegaldesleukin, with Nektar sharing 65% and BMS sharing 35% of the net profits and losses. 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 BMS Collaboration 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 share costs for the manufacturing of bempegaldesleukin, 35% of costs to BMS and 65% to Nektar.

In April 2018, BMS paid us a non-refundable upfront cash payment of $1.0 billion. We are eligible to receive additional cash payments up to a total of approximately $1.455 billion (including the milestones which we have received under Amendment No. 1 described below) upon the achievement of certain development and regulatory milestones, and up to a total of $350.0 million upon the achievement of certain sales milestones. In April 2018, BMS also purchased 8,284,600 shares of our common stock pursuant to the Share Purchase Agreement for total additional cash consideration of $850.0 million.

We determined that the BMS Collaboration Agreement falls within the scope of ASC 808, and we analogized to ASC 606 for the accounting for our performance obligation of the delivery of the licenses to develop and commercialize bempegaldesleukin.

During 2018, we aggregated the total consideration of $1.85 billion received under the agreements and allocated it between the stock purchase and the revenue-generating elements, because we and BMS negotiated the agreements together and the effective date of the BMS Collaboration Agreement was dependent upon the effective date of the Share Purchase Agreement. We recorded the estimated fair value of the shares of $790.2 million in stockholders’ equity. We allocated the remaining $1,059.8 million to the transaction price of the collaboration agreement, which we recognized in 2018. We consider the future potential development, regulatory and sales milestones to be variable consideration.

On January 9, 2020, we and BMS entered into Amendment No. 1 (the Amendment) to the BMS Collaboration Agreement. Pursuant to the Amendment, we and BMS agreed to update the Collaboration Development Plan under which we are collaborating and developing bempegaldesleukin. The cost sharing under the BMS Collaboration Agreement remains unchanged. We received a non-refundable, creditable milestone payment of $25.0 million for the achievement of the first patient, first visit in the registrational muscle-invasive bladder cancer trial on January 30, 2020, which we recognized in the three months ended March 31, 2020. We also received a non-refundable, non-creditable milestone payment of $25.0 million for the achievement of the first patient, first visit in the registrational adjuvant melanoma trial on July 27, 2020, which we recognized in the three months ended June 30, 2020. For the creditable milestone, BMS is entitled to deduct the amount paid from future development milestones due to us under the original agreement.

Other than these two milestones which we recognized during 2020, we continue to exclude the other milestones of up to $1.8 billion from the transaction price as of September 30, 2021 due to the significant uncertainties involved with clinical development and regulatory approval. We re-evaluate the transaction price at each reporting period and as uncertain events are resolved or other changes in circumstances occur.

As mentioned above, BMS shares certain percentages of development costs incurred by us and we share certain percentages of development costs incurred by BMS. We consider these activities to represent collaborative activities under ASC 808, and we recognize such cost sharing proportionately with the performance of the underlying services. We recognize BMS’ reimbursement of our costs as a reduction of research and development expense and our reimbursement of BMS’ costs as research and development expense. During the three and nine months ended September 30, 2021, we recorded $24.3 million and $76.5 million, respectively, as a reduction of research and development expense for BMS’ share of our expenses, net of our share of BMS’ expenses. During the three and nine months ended September 30, 2020, we recorded $29.2 million and $93.8 million, respectively, as a reduction of research and development expense for BMS’ share of our expenses, net of our share of BMS’ expenses. As of September 30, 2021, we have recorded an unbilled receivable of $24.9 million from BMS in accounts receivable in our Condensed Consolidated Balance Sheet.

Eli Lilly and Company (Lilly): NKTR-358

On July 23, 2017, we entered into a worldwide license agreement (the Lilly Agreement) with Eli Lilly and Company (Lilly), which became effective on August 23, 2017, to co-develop NKTR-358, a novel immunological drug candidate that we invented. Under the terms of the Lilly Agreement, we (i) received an initial payment of $150.0 million in September 2017 and are eligible for up to $250.0 million in additional development and regulatory milestones, (ii) will co-develop NKTR-358 with Lilly, for which we were responsible for completing Phase 1 clinical development and certain drug product development and supply activities, (iii) share with Lilly Phase 1B and 2 development costs with 75% of those costs borne by Lilly and 25% of the costs borne by us, (iv) will have the option to contribute funding to Phase 3 development on an indication-by-indication basis ranging from zero to 25% of development costs, and (v) will have the opportunity to receive a royalty rate up to the low twenties based upon our Phase 3 development cost contribution and the level of annual global product sales. Lilly will be responsible for all costs of global commercialization, and we will have an option to co-promote in the U.S. under certain conditions. A portion of the development milestones may be reduced by 50% under certain conditions, related to the final formulation of the approved product and the timing of prior approval (if any) of competitive products with a similar mechanism of action, which could reduce these milestone payments by 75% if both conditions occur.

The Lilly Agreement will continue until Lilly no longer has any royalty payment obligations or, if earlier, the termination of the agreement in accordance with its terms. The Lilly Agreement may be terminated by Lilly for convenience, and may also be terminated under certain other circumstances, including material breach.

We identified our license grant to Lilly, our Phase 1 clinical development obligation and our drug product development obligation as the significant performance obligations in the arrangement. Based on our estimates of the standalone selling prices of the performance obligations, we allocated the $150.0 million upfront payment as $125.9 million to the license, $17.6 million to our portion of the Phase 1 clinical development and $6.5 million to the drug product development. We recognized the revenue allocated to the license upon the effective date of the Lilly Agreement in August 2017. We recognized revenue for our performance obligations for Phase 1 clinical development and drug product development through March 31, 2020.

Although we are entitled to significant development milestones under this arrangement, through September 30, 2021, we have excluded such milestones from the transaction price due to the significant uncertainties involved with clinical development. We re-evaluate the transaction price at each reporting period and as uncertain events are resolved or other changes in circumstances occur.

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. As discussed in Note 5, in 2012, we sold all of our rights to receive royalties for CIMZIA® under our collaboration with UCB Pharma and MIRCERA® under our collaboration agreement with Roche. Additionally, in 2020, we sold our rights to receive royalties for ADYNOVATE® under our collaboration with Baxalta (a subsidiary of Takeda Pharmaceutical Company Ltd.), MOVANTIK® under our collaboration with AstraZeneca and REBINYN® under license agreement with Novo Nordisk. The 2020 Purchase and Sale Agreement provides for a cap on the amount of 2020 Transaction Royalties to be paid to HCR, such that, if the cap is achieved, future royalties on these products will return to us. See Note 5 for additional information regarding these agreements.

Additionally, we have collaboration agreements for products under development, under which we are entitled to up to a total of $40.0 million of development milestones, as well as sales milestones upon achievement of annual sales targets and royalties based on net sales of commercialized products, if any. However, given the current phase of development of the potential products under these collaboration agreements, we cannot estimate the probability or timing of achieving these milestones, and, therefore, have excluded all development milestones from the respective transaction prices for these agreements.

Stock-Based Compensation

9 Months Ended

Sep. 30, 2021

Share-based Payment Arrangement [Abstract]

Stock-Based Compensation

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


	Three months ended September 30,				Nine months ended September 30,
	2021		2020		2021		2020
Cost of goods sold	$	688	$	744	$	2,131	$	2,168
Research and development	14,138		14,212		41,779		43,826
General and administrative	9,831		8,711		28,359		25,255
Impairment of assets and other costs for terminated program	—		—		—		1,025
Total stock-based compensation	$	24,657	$	23,667	$	72,269	$	72,274

The stock-based compensation expense reported in impairment of assets and other costs for terminated program resulted from executive severance.

We issued stock-based awards our common stock as follows (shares in thousands):


	Three months ended September 30,				Nine months ended September 30,
	2021		2020		2021		2020
Options granted	397		233		674		282
Weighted-average grant-date fair value of options granted	$	9.36	$	11.64	$	9.72	$	11.68
RSUs granted	727		693		1,614		1,213
Weighted-average grant-date fair value of RSUs granted	$	16.48	$	21.56	$	17.98	$	21.04

On June 10, 2021, the stockholders of Nektar approved an amendment to the Amended and Restated 2017 Performance Incentive Plan to increase the aggregate number of shares of Common Stock authorized for issuance thereunder by 5,000,000 shares.

Net Loss Per Share

9 Months Ended

Sep. 30, 2021

Earnings Per Share [Abstract]

Net Loss Per Share

We calculate basic net loss per share based on the weighted-average number of common shares outstanding during the periods presented and calculate diluted net loss per share based on the weighted-average number of shares of common stock outstanding, including potentially dilutive securities. For all periods presented in the accompanying Condensed Consolidated Statements of Operations, our net loss available to common stockholders equals the reported net loss.

For the three and nine months ended September 30, 2021 and 2020, 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. During the three and nine months ended September 30, 2021 and 2020, potentially dilutive securities consisted of

weighted-average common shares underlying outstanding stock options and RSUs as follows (in thousands):


	Three months ended September 30,		Nine months ended September 30,
	2021	2020	2021	2020
Potentially dilutive securities	17,634	16,575	18,454	17,499

Organization and Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization	Organization We are a research-based biopharmaceutical company headquartered in San Francisco, California and incorporated in Delaware. We are developing a pipeline of drug candidates that leverage our proprietary and proven advanced polymer conjugate technology platforms, which are designed to enable the development of new molecular entities that target known mechanisms of action. Our research and development pipeline of new investigational drugs includes potential therapies for oncology, immunology and virology. 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.
Basis of Presentation and Principles of Consolidation	Basis of Presentation and Principles of Consolidation Our Condensed Consolidated Financial Statements include the financial position, results of operations and cash flows of our wholly-owned subsidiaries: Inheris Biopharma, Inc., Nektar Therapeutics (India) Private Limited (Nektar India), Nektar Therapeutics Europe GmbH, and certain other entities in Europe. We have eliminated all intercompany accounts and transactions in consolidation. We prepared our Condensed Consolidated Financial Statements following the requirements of the Securities and Exchange Commission (SEC) for interim reporting. As permitted under those rules, we may condense or omit certain footnotes or other financial information that are normally required by U.S. generally accepted accounting principles (GAAP) for annual periods. In the opinion of management, these financial statements include all normal and recurring adjustments that we consider necessary for the fair presentation of our financial position and operating results. Our Condensed 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 Condensed Consolidated Balance Sheets. To date, such cumulative currency translation adjustments have not been significant to our consolidated financial position. 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. There were no significant reclassifications out of accumulated other comprehensive loss to the statements of operations during the three and nine months ended September 30, 2021 and 2020. The accompanying Condensed Consolidated Financial Statements are unaudited. The Condensed Consolidated Balance Sheet data as of December 31, 2020 was derived from the audited consolidated financial statements which are included in our Annual Report on Form 10-K for the year ended December 31, 2020 filed with the SEC on February 26, 2021. The information included in this Quarterly Report on Form 10-Q should be read in conjunction with the consolidated financial statements and the accompanying notes to those financial statements included in our Annual Report on Form 10-K for the year ended December 31, 2020. Revenue, expenses, assets, and liabilities can vary during each quarter of the year. The results and trends in these interim Condensed Consolidated Financial Statements are not necessarily indicative of the results to be expected for the full year or any other period.
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with 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. As appropriate, we assess our estimates each period, update them to reflect current information and generally recognize any changes in such estimates in the period first identified.
Reclassifications	Reclassifications Certain items previously reported in specific financial statement captions have been reclassified to conform to the current period presentation. Such reclassifications do not materially impact previously reported revenue, operating loss, net loss, total assets, liabilities or stockholders’ equity.
Segment Information	Segment Information We operate in one business segment which focuses on applying our technology platform 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.
Significant Concentrations	Significant Concentrations Our customers are primarily pharmaceutical and biotechnology companies that are 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), and other contingent payments, as well as reimbursable costs from collaborative research and development agreements. As of September 30, 2021, our accounts receivable includes $24.9 million for unbilled net expense reimbursements from our collaboration partner Bristol-Myers Squibb Company (BMS) and $3.1 million under customer contracts from our collaboration partners. As of December 31, 2020, our accounts receivable included $38.7 million for unbilled net expense reimbursements from BMS and $0.2 million from customer contracts. We generally do not require collateral from our customers. We perform a regular review of our customers’ credit risk and payment histories, including payments made after period end. Historically, we have not experienced credit losses from our accounts receivable and recorded no bad debt expense for the three and nine months ended September 30, 2021 and 2020. We have not recorded a reserve for credit losses at September 30, 2021 or December 31, 2020. 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, including as a result of the COVID-19 pandemic, our ability to develop and produce our drug candidates, our ability to supply comparator drugs for our clinical trials, 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. 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 deterioration in this industry could have a material effect on our results of operations and financial position. 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, including the effects of the COVID-19 pandemic, result in downgrades below our minimum credit rating requirements and if we decide to sell these securities, we may experience losses on such sales.
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 proprietary 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 proprietary 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 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 invoice. We test our products for adherence to technical specifications before shipment; accordingly, we have not experienced any significant returns from our customers. 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. As of December 30, 2020, 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, including for our non-cash royalties, when the underlying sales occur based on our best estimates of sales of the drugs. Our partners generally pay royalties or commercial milestones after the end of the calendar quarter in accordance with contractual terms. 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 after 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 for our proprietary drug candidates and technology development and for certain third parties under collaboration agreements. For our proprietary 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 costs of our clinical trial 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 accrue costs associated with the start-up and reporting phases of the clinical trials ratably over the estimated duration of the start-up and reporting phases. We generally accrue costs associated with the treatment phase of clinical trials based on the estimated activities performed by third parties. 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 based on patient enrollment in the trials. In specific circumstances, such as for certain time-based costs, we recognize clinical trial expenses using a methodology that we consider to be more reflective of the timing of costs incurred. We record an accrued expense for the estimated costs of our contract manufacturing 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 include upfront payments and milestone payments, which depend on factors such as the achievement of the completion of certain stages of the manufacturing process. For purposes of recognizing expense, we assess whether we consider the production process is sufficiently defined such that the resulting product can be considered the delivery of a good, as evidenced by predictive or contractually required yields in the production process or payment terms based on the actual yield, or the delivery of a service, where processes and yields are developing and less certain. If we consider the process to be the delivery of a good, we recognize expense when the drug product is delivered, or we otherwise bear risk of loss. If we consider the process to be the delivery of a service, we recognize expense based on our best estimates of the contract manufacturer’s progress towards completion of the stages in the contracts. We recognize and amortize upfront payments and accrue liabilities based on the specific terms of each arrangement. Certain arrangements may provide upfront payments for certain stages of the arrangement and milestone payments for the completion of certain stages, and, accordingly, we may record advance payments for services that have not been completed or goods not delivered and liabilities for stages where the contract manufacturer is entitled to a milestone payment. 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. Impairment of Assets and Other Costs for Terminated ProgramOn January 14, 2020, the joint FDA Anesthetic Drug Products Advisory Committee and Drug Safety and Risk Management Committee did not recommend approval of our New Drug Application (NDA) for NKTR-181. As a result, we withdrew our NDA and decided to make no further investments in this program.We present these costs in the Impairment of assets and other costs for terminated program line in our Condensed Consolidated Statement of Operations.
Income Taxes	Income Taxes For the three and nine months ended September 30, 2021 and 2020, our income tax expense primarily results from our foreign operations. We have fully reserved our U.S. federal deferred tax assets generated from our net operating losses, as we believe it is not more likely than not that the benefit will be realized.
Inventory	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 as manufactured by us or when purchased.
Fair Value Measurement	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. We use a market approach to value our Level 2 investments. The disclosed fair value related to our investments is based on market prices from a variety of industry standard data providers and generally represents quoted prices for similar assets in active markets or has been derived from observable market data. For the nine months ended September 30, 2021, 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. For the reconciliation of the changes in the development derivative liability and the description of the significant inputs used in estimating its fair value, see Note 4.

Cash and Investments in Marketable Securities (Tables)

9 Months Ended

Sep. 30, 2021

Fair Value Disclosures [Abstract]

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
	September 30, 2021		December 31, 2020
Cash and cash equivalents	$	54,017	$	198,955
Short-term investments	867,063		862,941
Long-term investments	34,219		136,662
Total cash and investments in marketable securities	$	955,299	$	1,198,558

Portfolio of Cash and Investments in Marketable Securities

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


	September 30, 2021								December 31, 2020
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value		Fair Value
Corporate notes and bonds	$	329,376	$	53	$	(90)	$	329,339	$	687,469
Corporate commercial paper	555,989		35		(100)		555,924		313,497
Obligations of U.S. government agencies	5,880		2		—		5,882		2,382
Available-for-sale investments	$	891,245	$	90	$	(190)	$	891,145	$	1,003,348
Money market funds							48,336		179,302
Certificates of deposit							10,137		9,623
Cash							5,681		6,285
Total cash and investments in marketable securities							$	955,299	$	1,198,558

Inventory (Tables)

9 Months Ended

Sep. 30, 2021

Inventory Disclosure [Abstract]

Inventory

Inventory consists of the following (in thousands):


	September 30, 2021		December 31, 2020
Raw materials	$	1,744	$	2,422
Work-in-process	9,388		10,703
Finished goods	4,198		2,167
Total inventory	$	15,330	$	15,292

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

9 Months Ended

Sep. 30, 2021

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Schedule of Derivative Liabilities at Fair Value

The following table presents the changes in the development derivative liability for the three and nine months ended September 30, 2021:


	Three Months Ended September 30, 2021		Nine Months Ended September 30, 2021
Fair value at beginning of period	$	11,607	$	—
Non-cash research and development expense	5,702		11,497
Cash receipts from SFJ	750		2,250
Change in the fair value of development derivative liability	3,328		7,640
Fair value at end of period	$	21,387	$	21,387

Liabilities Related to Sales of Future Royalties (Tables)

9 Months Ended

Sep. 30, 2021

Other Liabilities Disclosure [Abstract]

Schedule Of Liability Related To Sale Of Potential Future Royalties


	2012 Purchase and Sale Agreement				2020 Purchase and Sale Agreement
	Three and nine months ended September 30,				Three and nine months ended September 30,
	2021		2020		2021
Interest rates - end of period presented
Implicit interest rate over the life of the agreement	20.2	%	20.2	%	16.0	%
Prospective effective interest rate	48.0	%	48.0	%	16.0	%

Fair Value Measurement (Tables)

9 Months Ended

Sep. 30, 2021

Fair Value Disclosures [Abstract]

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis


	As of September 30, 2021
	Level 1		Level 2		Level 3		Total
Assets:
Corporate notes and bonds	$	—	$	329,339	$	—	$	329,339
Corporate commercial paper	—		555,924		—		555,924
Obligations of U.S. government agencies	—		5,882		—		5,882
Money market funds	48,336		—		—		48,336
Total assets	$	48,336	$	891,145	$	—	$	939,481
Liabilities:
Development derivative liability	$	—	$	—	$	21,387	$	21,387


	As of December 31, 2020
	Level 1		Level 2		Level 3		Total
Assets:
Corporate notes and bonds	$	—	$	687,469	$	—	$	687,469
Corporate commercial paper	—		313,497		—		313,497
Obligations of U.S. government agencies	—		2,382		—		2,382
Money market funds	179,302		—		—		179,302
Total assets	179,302		$	1,003,348	$	—	$	1,182,650
Liabilities:
Development derivative liability	$	—	$	—	$	—	$	—

License and Collaboration Agreements (Tables)

9 Months Ended

Sep. 30, 2021

License And Collaboration Agreements [Abstract]

License, Collaboration and Other Revenue

In accordance with our collaboration agreements, we recognized license, collaboration and other revenue as follows (in thousands):


		Three months ended September 30,				Nine months ended September 30,
Partner	Drug or Drug Candidate	2021		2020		2021		2020
Bristol-Myers Squibb Company	Bempegaldesleukin	$	—	$	—	$	—	$	50,000
Eli Lilly and Company	NKTR-358	—		—		—		1,259
Other		314		1,631		396		4,162
Total license, collaboration and other revenue		$	314	$	1,631	$	396	$	55,421

Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2021

Share-based Payment Arrangement [Abstract]

Stock-Based Compensation Expense

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


	Three months ended September 30,				Nine months ended September 30,
	2021		2020		2021		2020
Cost of goods sold	$	688	$	744	$	2,131	$	2,168
Research and development	14,138		14,212		41,779		43,826
General and administrative	9,831		8,711		28,359		25,255
Impairment of assets and other costs for terminated program	—		—		—		1,025
Total stock-based compensation	$	24,657	$	23,667	$	72,269	$	72,274

Share-based Compensation, Activity

We issued stock-based awards our common stock as follows (shares in thousands):


	Three months ended September 30,				Nine months ended September 30,
	2021		2020		2021		2020
Options granted	397		233		674		282
Weighted-average grant-date fair value of options granted	$	9.36	$	11.64	$	9.72	$	11.68
RSUs granted	727		693		1,614		1,213
Weighted-average grant-date fair value of RSUs granted	$	16.48	$	21.56	$	17.98	$	21.04

Net Loss Per Share (Tables)

9 Months Ended

Sep. 30, 2021

Earnings Per Share [Abstract]

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share

During the three and nine months ended September 30, 2021 and 2020, potentially dilutive securities consisted of weighted-average common shares underlying outstanding stock options and RSUs as follows (in thousands):


	Three months ended September 30,		Nine months ended September 30,
	2021	2020	2021	2020
Potentially dilutive securities	17,634	16,575	18,454	17,499

Organization and Summary of Significant Accounting Policies - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2021 USD ($) segment	Dec. 31, 2020 USD ($)	Mar. 31, 2020 USD ($)
Organization And Summary Of Significant Accounting Policies [Line Items]
Cash and investments in marketable securities	$ 955,299,000	$ 1,198,558,000
Number of business segment \| segment	1
Accounts receivable	$ 28,994,000	38,889,000
Allowance for credit loss	0	0
Aggregate offering price	300,000,000
NKTR - 181
Organization And Summary Of Significant Accounting Policies [Line Items]
Write off of prepayment			$ 19,700,000
Purchase commitment, remaining minimum amount committed			$ 25,500,000
Bristol Myers Squibb Collaboration Agreement
Organization And Summary Of Significant Accounting Policies [Line Items]
Accounts receivable	24,900,000	38,700,000
Collaboration Partner
Organization And Summary Of Significant Accounting Policies [Line Items]
Accounts receivable	$ 3,100,000	$ 200,000

Cash and Investments in Marketable Securities - Cash and Investments in Marketable Securities, Including Cash Equivalents (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Cash and cash equivalents	$ 54,017	$ 198,955
Short-term investments	867,063	862,941
Long-term investments	34,219	136,662
Total cash and investments in marketable securities	$ 955,299	$ 1,198,558

Cash and Investments in Marketable Securities - Additional Information (Detail) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Cash and Investments in Marketable Securities [Line Items]
Maximum maturity term for debt securities investment	2 years
Weighted average maturity term for debt securities investment (or less)	1 year
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax		$ 1.1
Debt securities, available-for-sale accumulated gross unrealized loss, before tax		$ 0.2
Minimum
Cash and Investments in Marketable Securities [Line Items]
Long term investment maturity period	1 year	1 year
Maximum
Cash and Investments in Marketable Securities [Line Items]
Long term investment maturity period	2 years	2 years

Cash and Investments in Marketable Securities - Portfolio of Cash and Investments in Marketable Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gross Unrealized Gains		$ 1,100
Gross Unrealized Losses		(200)
Cash	$ 5,681	6,285
Total cash and investments in marketable securities	955,299	1,198,558
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	891,245
Gross Unrealized Gains	90
Gross Unrealized Losses	(190)
Fair Value	891,145	1,003,348
Corporate notes and bonds \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	329,376
Gross Unrealized Gains	53
Gross Unrealized Losses	(90)
Fair Value	329,339	687,469
Corporate commercial paper \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	555,989
Gross Unrealized Gains	35
Gross Unrealized Losses	(100)
Fair Value	555,924	313,497
Obligations of U.S. government agencies \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	5,880
Gross Unrealized Gains	2
Gross Unrealized Losses	0
Fair Value	5,882	2,382
Money market funds \| Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	48,336	179,302
Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	$ 10,137	$ 9,623

Inventory (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Inventory Disclosure [Abstract]
Raw materials	$ 1,744	$ 2,422
Work-in-process	9,388	10,703
Finished goods	4,198	2,167
Total inventory	$ 15,330	$ 15,292

Co-Development Agreement with SFJ Pharmaceuticals and Development Derivative Liability - Additional Information (Details)	Feb. 12, 2021 USD ($)
Cost of Borrowing
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Counterparty cost of borrowing	0.122
SFJ
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Committed funding (up to)	$ 150,000,000
Success-based annual payments, first indication	$ 450,000,000
Installment period, first indication	5 years
Success-based payments, first payment	$ 30,000,000
Success-based annual payments, second indication	$ 150,000,000
Installment period, second indication	7 years
One time payment	$ 37,500,000
SFJ \| Cost of Borrowing
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Counterparty cost of borrowing	0.010

Co-Development Agreement with SFJ Pharmaceuticals and Development Derivative Liability - Fair Value of Derivative Liability (Details) - Development Derivative Liability - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2021
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value at beginning of period	$ 11,607	$ 0
Non-cash research and development expense	5,702	11,497
Cash receipts from SFJ	750	2,250
Change in the fair value of development derivative liability	3,328	7,640
Fair value at end of period	$ 21,387	$ 21,387

Liabilities Related to Sales of Future Royalties - Additional Information (Detail) - USD ($)	Dec. 30, 2020	Dec. 16, 2020	Feb. 24, 2012
2012 Purchase and Sale Agreement
Liability Related to Sale of Future Royalties [Line Items]
Proceeds from sale of royalty rights			$ 124,000,000
Transaction costs related to sale of potential future royalties			$ 4,400,000
2020 Purchase and Sale Agreement
Liability Related to Sale of Future Royalties [Line Items]
Proceeds from sale of royalty rights	$ 150,000,000
Transaction costs related to sale of potential future royalties	$ 3,800,000
Payment of transaction related to purchase and sale agreement		$ 210,000,000
Payment of transaction related to purchase and sale agreement if threshold is not achieved		240,000,000
Minimum transaction royalties payments needed to pay the difference between the 2025 threshold and 2020 transaction royalties		$ 208,000,000

Liabilities Related to Sales of Future Royalties - Estimates of Annual Interest Rate (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
2012 Purchase and Sale Agreement
Liability Related to Sale of Future Royalties [Line Items]
Implicit interest rate over the life of the agreement	20.20%	20.20%	20.20%	20.20%
Prospective effective interest rate	48.00%	48.00%	48.00%	48.00%
2020 Purchase and Sale Agreement
Liability Related to Sale of Future Royalties [Line Items]
Implicit interest rate over the life of the agreement	16.00%		16.00%
Prospective effective interest rate	16.00%		16.00%

Commitments and Contingencies - Additional Information (Detail) - USD ($)	Sep. 30, 2021	Dec. 31, 2020
Legal Matters
Loss Contingencies [Line Items]
Litigation matters, liabilities	$ 0	$ 0
Indemnification Obligation
Loss Contingencies [Line Items]
Litigation matters, liabilities	$ 0	$ 0

Fair Value Measurement (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Level 2
Assets:
Available-for-sale investments	$ 891,145	$ 1,003,348
Recurring
Assets:
Total assets	939,481	1,182,650
Liabilities:
Development derivative liability	21,387	0
Recurring \| Corporate notes and bonds
Assets:
Available-for-sale investments	329,339	687,469
Recurring \| Corporate commercial paper
Assets:
Available-for-sale investments	555,924	313,497
Recurring \| Obligations of U.S. government agencies
Assets:
Available-for-sale investments	5,882	2,382
Recurring \| Money market funds
Assets:
Money market funds	48,336	179,302
Recurring \| Level 1
Assets:
Total assets	48,336	179,302
Liabilities:
Development derivative liability	0	0
Recurring \| Level 1 \| Corporate notes and bonds
Assets:
Available-for-sale investments	0	0
Recurring \| Level 1 \| Corporate commercial paper
Assets:
Available-for-sale investments	0	0
Recurring \| Level 1 \| Obligations of U.S. government agencies
Assets:
Available-for-sale investments	0	0
Recurring \| Level 1 \| Money market funds
Assets:
Money market funds	48,336	179,302
Recurring \| Level 2
Assets:
Total assets	891,145	1,003,348
Liabilities:
Development derivative liability	0	0
Recurring \| Level 2 \| Corporate notes and bonds
Assets:
Available-for-sale investments	329,339	687,469
Recurring \| Level 2 \| Corporate commercial paper
Assets:
Available-for-sale investments	555,924	313,497
Recurring \| Level 2 \| Obligations of U.S. government agencies
Assets:
Available-for-sale investments	5,882	2,382
Recurring \| Level 2 \| Money market funds
Assets:
Money market funds	0	0
Recurring \| Level 3
Assets:
Total assets	0	0
Liabilities:
Development derivative liability	21,387	0
Recurring \| Level 3 \| Corporate notes and bonds
Assets:
Available-for-sale investments	0	0
Recurring \| Level 3 \| Corporate commercial paper
Assets:
Available-for-sale investments	0	0
Recurring \| Level 3 \| Obligations of U.S. government agencies
Assets:
Available-for-sale investments	0	0
Recurring \| Level 3 \| Money market funds
Assets:
Money market funds	$ 0	$ 0

License and Collaboration Agreements - License, Collaboration and Other Revenue (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
License And Collaboration Agreements [Line Items]
Total license, collaboration and other revenue	$ 314	$ 1,631	$ 396	$ 55,421
Bristol-Myers Squibb Company \| Bempegaldesleukin
License And Collaboration Agreements [Line Items]
Total license, collaboration and other revenue	0	0	0	50,000
Eli Lilly and Company \| NKTR-358
License And Collaboration Agreements [Line Items]
Total license, collaboration and other revenue	0	0	0	1,259
Other
License And Collaboration Agreements [Line Items]
Total license, collaboration and other revenue	$ 314	$ 1,631	$ 396	$ 4,162

License and Collaboration Agreements - Additional Information (Detail) - USD ($)			1 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended
	Feb. 13, 2018	Aug. 23, 2017	Apr. 30, 2018	Sep. 30, 2017	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2018	Dec. 31, 2020	Jan. 09, 2020
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognized in period related to performance in prior periods					$ 19,400,000	$ 22,700,000	$ 58,700,000	$ 109,400,000
Potential future additional development and regulatory milestones (up to)					1,700,000,000		1,700,000,000
Accounts receivable					28,994,000		28,994,000			$ 38,889,000
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 Collaboration Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Sales milestone, revenue								50,000,000
Bristol Myers Squibb Collaboration Agreement \| Bristol-Myers Squibb Company \| Purchase Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total consideration received under agreements									$ 1,850,000,000
Estimated fair value of shares									790,200,000
Remaining amount allocated to transaction price									$ 1,059,800,000
Nektar-358 \| Nektar's
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-358 \| Eli Lilly and Company \| Maximum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential future additional development and regulatory milestones (up to)		$ 250,000,000
Nektar-358 \| Eli Lilly and Company \| Nektar's
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of regulatory milestones payments will be reduced under certain conditions		50.00%
Percentage of regulatory milestones payments will be reduced if conditions occur		75.00%
Nektar-358 \| Eli Lilly and Company \| Nektar's \| Maximum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of funding phase 3 development costs on an indication by indication basis borne		25.00%
Nektar-358 \| Eli Lilly and Company \| Nektar's \| Minimum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of funding phase 3 development costs on an indication by indication basis borne		0.00%
Nektar-358 \| Eli Lilly
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of sharing in Phase 2 development costs		75.00%
Other \| Nektar's
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential future additional payments for development milestones (up to)					40,000,000		40,000,000
Nektar 214 \| Bristol-Myers Squibb Company \| Research and Development Expense
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Reimbursement of expenses					24,300,000	$ 29,200,000	76,500,000	$ 93,800,000
Nektar 214 \| Bristol Myers Squibb Collaboration Agreement \| Nektar's
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Global commercialization profits and losses sharing percentage	65.00%
Percentage of sharing production costs	65.00%
Upfront and milestone payments received from license agreements			1,000,000,000
Maximum total additional cash payments receivable upon achievement of certain development and regulatory milestones							1,455,000,000
Nektar 214 \| Bristol Myers Squibb Collaboration Agreement \| Nektar's \| Milestone One
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential future additional payments for development milestones (up to)											$ 25,000,000
Potential development milestones excluded from transaction price (up to)					$ 1,800,000,000		$ 1,800,000,000
Nektar 214 \| Bristol Myers Squibb Collaboration Agreement \| Nektar's \| Maximum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Eligible additional cash payments receivable upon achievement of certain sales milestones			$ 350,000,000
Nektar 214 \| Bristol Myers Squibb Collaboration Agreement \| Nektar's \| Opdivo
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of sharing development costs	32.50%
Nektar 214 \| Bristol Myers Squibb Collaboration Agreement \| Bristol-Myers Squibb Company
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Global commercialization profits and losses sharing percentage	35.00%
Percentage of sharing production costs	35.00%
Nektar 214 \| Bristol Myers Squibb Collaboration Agreement \| Bristol-Myers Squibb Company \| Opdivo
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of sharing development costs	67.50%
Nektar 358 License \| Eli Lilly and Company
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Amount of transaction price allocated to performance obligation				125,900,000
Nektar 358 License \| Phase 1 Clinical Development \| Eli Lilly and Company
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Amount of transaction price allocated to performance obligation				17,600,000
Nektar 358 License \| Drug Product Development \| Eli Lilly and Company
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Amount of transaction price allocated to performance obligation				$ 6,500,000

Stock-Based Compensation - Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	$ 24,657	$ 23,667	$ 72,269	$ 72,274
Cost of goods sold
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	688	744	2,131	2,168
Research and development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	14,138	14,212	41,779	43,826
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	9,831	8,711	28,359	25,255
Impairment of assets and other costs for terminated program
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	$ 0	$ 0	$ 0	$ 1,025

Stock-Based Compensation - Activity (Detail) - $ / shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted (in shares)	397	233	674	282
Weighted average grant-date fair value of options granted (in dollars per share)	$ 9.36	$ 11.64	$ 9.72	$ 11.68
Restricted Stock Units (RSU)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSUs granted (in shares)	727	693	1,614	1,213
Weighted average grant-date fair value, of RSUs granted (in dollars per share)	$ 16.48	$ 21.56	$ 17.98	$ 21.04

Stock-Based Compensation - Additional Information (Detail)	Jun. 10, 2021 shares
Share-based Payment Arrangement [Abstract]
Aggregate number of shares authorized (in shares)	5,000,000

Net Loss Per Share (Detail) - shares shares in Thousands	3 Months Ended		9 Months Ended
Net Loss Per Share (Detail) - shares shares in Thousands	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Earnings Per Share [Abstract]
Potentially dilutive securities (in shares)	17,634	16,575	18,454	17,499