Nektar Therapeutics (NKTR) 10-Q 9 May 19 2019 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2019	May 01, 2019
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Trading Symbol	NKTR
Entity Registrant Name	NEKTAR THERAPEUTICS
Entity Central Index Key	0000906709
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		174,306,995

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 106,752	$ 194,905
Short-term investments	1,281,913	1,140,445
Accounts receivable	42,894	43,213
Inventory	11,778	11,381
Advance payments to contract manufacturers	27,425	26,450
Other current assets	19,352	21,293
Total current assets	1,490,114	1,437,687
Long-term investments	455,867	582,889
Property, plant and equipment, net	58,158	48,851
Operating lease right-of-use assets	83,475
Goodwill	76,501	76,501
Other assets	2,367	4,244
Total assets	2,166,482	2,150,172
Current liabilities:
Accounts payable	11,012	5,854
Accrued compensation	18,371	9,937
Accrued contract manufacturing expenses	21,384	23,841
Accrued clinical trial expenses	17,496	14,700
Other accrued expenses	14,624	9,580
Interest payable	4,090	4,198
Operating lease liabilities, current portion	1,649
Deferred revenue, current portion	11,092	13,892
Total current liabilities	99,718	82,002
Senior secured notes, net	247,386	246,950
Operating lease liabilities, less current portion	95,024
Liability related to the sale of future royalties, net	80,837	82,911
Deferred revenue, less current portion	9,340	10,744
Other long-term liabilities	666	9,990
Total liabilities	532,971	432,597
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $0.0001 par value; 10,000 shares authorized; no shares designated or outstanding at March 31, 2019 or December 31, 2018	0	0
Common stock, $0.0001 par value; 300,000 shares authorized; 174,228 shares and 173,530 shares outstanding at March 31, 2019 and December 31, 2018, respectively	17	17
Capital in excess of par value	3,178,773	3,147,925
Accumulated other comprehensive loss	(2,716)	(6,316)
Accumulated deficit	(1,542,563)	(1,424,051)
Total stockholders’ equity	1,633,511	1,717,575
Total liabilities and stockholders’ equity	$ 2,166,482	$ 2,150,172

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Mar. 31, 2019	Dec. 31, 2018
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares designated	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	300,000,000	300,000,000
Common stock, shares outstanding	174,228,000	173,530,000

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Revenue:
Total revenue	$ 28,222	$ 38,018
Operating costs and expenses:
Cost of goods sold	$ 5,440	$ 6,646
Type of Cost, Good or Service [Extensible List]	us-gaap:ProductMember	us-gaap:ProductMember
Research and development	$ 118,463	$ 99,424
General and administrative	25,006	18,687
Total operating costs and expenses	148,909	124,757
Loss from operations	(120,687)	(86,739)
Non-operating income (expense):
Interest expense	(5,226)	(5,340)
Non-cash interest expense on liability related to sale of future royalties	(6,065)	(5,019)
Interest income and other income (expense), net	12,483	1,571
Total non-operating income (expense), net	1,192	(8,788)
Loss before provision for income taxes	(119,495)	(95,527)
Provision (benefit) for income taxes	(983)	265
Net loss	$ (118,512)	$ (95,792)
Basic and diluted net loss per share	$ (0.68)	$ (0.60)
Weighted average shares outstanding used in computing basic and diluted net loss per share	173,859	160,884
Product Sales [Member]
Revenue:
Total revenue	$ 4,398	$ 6,295
Royalty Revenue [Member]
Revenue:
Total revenue	11,390	11,076
Non-cash Royalty Revenue Related to Sale of Future Royalties [Member]
Revenue:
Total revenue	8,230	6,920
License, Collaboration and Other Revenue [Member]
Revenue:
Total revenue	$ 4,204	$ 13,727

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement Of Income And Comprehensive Income [Abstract]
Comprehensive loss	$ (114,912)	$ (96,477)

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Shares [Member]	Capital in Excess of Par Value [Member]	Accumulated Other Comprehensive Loss [Member]	Accumulated Deficit [Member]
Beginning Balance at Dec. 31, 2017	$ 87,828	$ 15	$ 2,207,865	$ (2,111)	$ (2,117,941)
Beginning Balance, Shares at Dec. 31, 2017		159,524,000
Shares issued under equity compensation plans	$ 34,406	$ 1	34,405
Shares issued under equity compensation plans, Shares	2,854,816	2,855,000
Stock-based compensation	$ 19,949		19,949
Adoption of new accounting standards	12,577				12,577
Other comprehensive loss	(685)			(685)
Net loss	(95,792)				(95,792)
Ending Balance at Mar. 31, 2018	58,283	$ 16	2,262,219	(2,796)	(2,201,156)
Ending Balance, Shares at Mar. 31, 2018		162,379,000
Beginning Balance at Dec. 31, 2018	1,717,575	$ 17	3,147,925	(6,316)	(1,424,051)
Beginning Balance, Shares at Dec. 31, 2018		173,530,000
Shares issued under equity compensation plans	$ 5,463		5,463
Shares issued under equity compensation plans, Shares	698,000	698,000
Stock-based compensation	$ 25,385		25,385
Other comprehensive loss	3,600			3,600
Net loss	(118,512)				(118,512)
Ending Balance at Mar. 31, 2019	$ 1,633,511	$ 17	$ 3,178,773	$ (2,716)	$ (1,542,563)
Ending Balance, Shares at Mar. 31, 2019		174,228,000

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities:
Net loss	$ (118,512,000)	$ (95,792,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Non-cash royalty revenue related to sale of future royalties	(8,230,000)	(6,920,000)
Non-cash interest expense on liability related to sale of future royalties	6,065,000	5,019,000
Stock-based compensation	25,385,000	19,949,000
Depreciation and amortization	3,077,000	2,541,000
Accretion of discounts, net and other non-cash transactions	(4,303,000)	(370,000)
Changes in operating assets and liabilities:
Accounts receivable	319,000	151,000
Inventory	(397,000)	51,000
Other assets	4,209,000	1,853,000
Accounts payable	5,156,000	6,492,000
Accrued compensation	8,434,000	6,867,000
Other accrued expenses	774,000	10,826,000
Deferred revenue	(4,204,000)	(3,678,000)
Other liabilities	1,332,000	545,000
Net cash used in operating activities	(80,895,000)	(52,466,000)
Cash flows from investing activities:
Purchases of investments	(368,739,000)
Maturities of investments	362,249,000	37,232,000
Sales of investments	0	11,963,000
Purchases of property, plant and equipment	(5,648,000)	(985,000)
Net cash provided by (used in) investing activities	(12,138,000)	48,210,000
Cash flows from financing activities:
Proceeds from shares issued under equity compensation plans	4,894,000	34,352,000
Net cash provided by financing activities	4,894,000	34,352,000
Effect of exchange rates on cash and cash equivalents	(14,000)	(53,000)
Net increase (decrease) in cash and cash equivalents	(88,153,000)	30,043,000
Cash and cash equivalents at beginning of period	194,905,000	4,762,000
Cash and cash equivalents at end of period	106,752,000	34,805,000
Supplemental disclosure of cash flow information:
Cash paid for interest	$ 4,805,000	$ 4,952,000

Organization and Summary of Sig

Organization and Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization and Summary of Significant Accounting Policies	Note 1 — Organization and Summary of Significant Accounting Policies Organization We are a research-based biopharmaceutical company headquartered in San Francisco, California and incorporated in Delaware. We are developing a pipeline of drug candidates that utilize our 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 treatments for cancer, autoimmune disease and chronic pain. 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 March 31, 2019, we had approximately $1.8 billion in cash and investments in marketable securities and debt of $250.0 million in principal of senior secured notes due in October 2020. Basis of Presentation and Principles of Consolidation Our consolidated financial statements include the financial position, results of operations and cash flows of our wholly-owned subsidiaries: Nektar Therapeutics (India) Private Limited (Nektar India), Inheris Pharmaceuticals, Inc. and Nektar Therapeutics UK Limited. All intercompany accounts and transactions have been eliminated 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, certain footnotes or other financial information that are normally required by U.S. generally accepted accounting principles (GAAP) for annual periods can be condensed or omitted. 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. Translation gains and losses are included in accumulated other comprehensive loss in the stockholders’ equity section of the 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, neither of which were significant during the three months ended March 31, 2019 and 2018. In addition, there were no significant reclassifications out of accumulated other comprehensive loss to the statements of operations during the three months ended March 31, 2019 and 2018. The accompanying Condensed Consolidated Financial Statements are unaudited. The Condensed Consolidated Balance Sheet data as of December 31, 2018 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, 2018 filed with the SEC on March 1, 2019. 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, 2018. 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. Our estimates include those related to estimated selling prices of performance obligations and estimates of variable consideration in collaboration agreements, estimated royalty revenue, other estimates required for revenue recognition as described further below, the net realizable value of inventory, the impairment of investments, goodwill and long-lived assets, contingencies, accrued clinical trial, contract manufacturing and other expenses, estimated non-cash royalty revenue and non-cash interest expense from our liability related to our sale of future royalties, stock-based compensation, and ongoing litigation, among other estimates. We base our estimates on historical experience and on other assumptions that management believes are reasonable under the circumstances. These estimates form the basis for making judgments about the carrying values of assets and liabilities when these values are not readily apparent from other sources. As appropriate, estimates are assessed each period and updated to reflect current information and any changes in estimates will generally be reflected 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 We are dependent on our suppliers and contract manufacturers to provide raw materials and drugs of appropriate quality and reliability and to meet applicable contract and regulatory requirements. In certain cases, we rely on single sources of supply of one or more critical materials. Consequently, in the event that supplies are delayed or interrupted for any reason, our ability to develop and produce our drug candidates or our ability to meet our supply obligations could be significantly impaired, which could have a material adverse effect on our business, financial condition and results of operations. Adoption of New Accounting Principle On January 1, 2019, we adopted Accounting Standards Codification (ASC) 842, Leases Leases Under ASC 842, an entity recognizes a right-of-use asset and a corresponding lease liability, measured as the present value of the lease payments, for leases with terms greater than one year. As a result of the adoption of ASC 842 on January 1, 2019, we recorded right-of-use assets of $83.5 million and lease liabilities of $96.2 million with no cumulative effect adjustment to accumulated deficit. Our lease arrangements are further described in Note 4. 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 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 Revenue from Contracts with Customers Revenue Recognition For elements of those arrangements that we determine should be accounted for under ASC 606, we assess which activities in our collaboration agreements are performance obligations that should be accounted for separately and determine the transaction price of the arrangement, which includes the assessment of the probability of achievement of future milestones and other potential consideration. For arrangements that include multiple performance obligations, such as granting a license or performing contract research and development activities or participation on joint steering or other committees, we allocate upfront and milestone payments under a relative standalone selling price method. Accordingly, we develop assumptions that require judgment to determine the standalone selling price for each performance obligation identified in the contract. These key assumptions may include revenue forecasts, clinical development timelines and costs, discount rates and probabilities of clinical and regulatory success. Product Sales Product sales are primarily derived from manufacturing and supply agreements with our customers. We have assessed our current manufacturing and supply arrangements and have generally determined that they provide the customer an option to purchase our proprietary PEGylation materials. Accordingly, we treat each purchase order as a discrete exercise of the customer’s option (i.e. a separate contract) rather than as a component of the overall arrangement. The pricing for the manufacturing and supply is generally at a fixed price and may be subject to annual producer price index (PPI) adjustments. We invoice and recognize product sales when title and risk of loss pass to the customer, which generally occurs upon shipment. Customer payments are generally due 30 days from receipt of 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, we are entitled to royalties from our collaboration partners based on the net sales of their approved drugs that are marketed and sold in one or more countries where we hold royalty rights. For arrangements that include sales-based royalties, including commercial milestone payments based on the level of sales, we have concluded that the license is the predominant item to which the royalties relate. 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. We present commercial milestone payments within license, collaboration and other revenue. 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 or filing for or receipt of regulatory approval, 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. Our partners generally pay development milestones subsequent to achievement of the triggering event. Research and Development Services : For amounts allocated to our research and development obligations in a collaboration arrangement, we recognize revenue over time using a proportional performance model, representing the transfer of goods or services as we perform activities over the term of the agreement. Research and Development Expense Research and development costs are expensed as incurred and include salaries, benefits and other operating costs such as outside services, supplies and allocated overhead costs. We perform research and development 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 clinical joint development collaboration, such as our collaboration with Bristol-Myers Squibb Company (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 total estimated cost of the treatment phase on a per patient basis and we 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 to be considered the delivery of a good, as evidenced by predictive or contractually required yields in the production process, 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. Advance payments for goods or services that will be used or rendered for future research and development activities are capitalized as prepaid expenses and recognized as expense as the related goods are delivered or the related services are performed. We base our estimates on the best information available at the time. However, additional information may become available to us 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. Such increases or decreases in cost are generally considered to be changes in estimates and will be reflected in research and development expenses in the period identified. Long-Lived Assets We assess the impairment of long-lived assets whenever events or changes in business circumstances indicate that the carrying amounts of the assets may not be fully recoverable. In the case of property, plant and equipment and right-of-use assets, we determine whether there has been an impairment by comparing the carrying value of the asset to the anticipated undiscounted net cash flows associated with the asset. If such cash flows are less than the carrying value, we write down the asset to its fair value, which may be measured as anticipated discounted net cash flows associated with the asset. In the case of goodwill impairment, we compare the carrying value of the reporting unit to its fair value, which we generally measure using market capitalization for our single reporting unit. If an impairment exists, we write down goodwill such that the carrying value of the reporting units equals its fair value. Income Taxes For the three months ended March 31, 2019 and 2018, we recorded an income tax provision for our Nektar India operations at an effective tax rate of approximately 29% and 31%, respectively. Due to our unrealized gain on available-for-sale securities in the three months ended March 31, 2019, we recorded a tax provision against such gain with an offsetting tax benefit in continuing operations of $1.1 million. The U.S. federal deferred tax assets generated from our net operating losses have been fully reserved, as we believe it is not more likely than not that the benefit will be realized. Recent Accounting Pronouncements In November 2018, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update 2018-18: Clarifying the Interaction between Topic 808 and Topic 606 (ASU 2018-18). The guidance clarifies that certain transactions between collaborative arrangement participants should be accounted for as revenue under ASC 606 when the collaborative arrangement participant is a customer for a promised good or service that is distinct within the collaborative arrangement. The guidance also precludes entities from presenting amounts related to transactions with a collaborative arrangement participant that is not a customer as revenue, unless those transactions are directly related to third-party sales. ASU 2018-18 is effective in the first quarter of 2020 and should be applied retrospectively to January 1, 2018, when we adopted ASC 606. Early adoption is permitted. We are evaluating the effect of adoption, but we do not expect a material effect on our revenue.

Cash and Investments in Marketa

Cash and Investments in Marketable Securities	3 Months Ended
	Mar. 31, 2019
Fair Value Disclosures [Abstract]
Cash and Investments in Marketable Securities	Note 2 — Cash and Investments in Marketable Securities Cash and investments in marketable securities, including cash equivalents, are as follows (in thousands): Estimated Fair Value at March 31, 2019 December 31, 2018 Cash and cash equivalents $ 106,752 $ 194,905 Short-term investments 1,281,913 1,140,445 Long-term investments 455,867 582,889 Total cash and investments in marketable securities $ 1,844,532 $ 1,918,239 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 March 31, 2019 and December 31, 2018, all of our long-term investments had maturities between one and two years. Gross unrealized gains and losses were not significant at either March 31, 2019 or December 31, 2018. During the three months ended March 31, 2018, we sold available-for-sale securities totaling $12.0 million, and during the three months ended March 31, 2019, we sold no available-for-sale securities. Gross realized gains and losses on those 2018 sales were not significant. The cost of securities sold is based on the specific identification method. Under the terms of our 7.75% senior secured notes due October 2020, we are required to maintain a minimum cash and investments in marketable securities balance of $60.0 million. Our portfolio of cash and investments in marketable securities includes (in thousands): Estimated Fair Value at Fair Value Hierarchy Level March 31, 2019 December 31, 2018 Corporate notes and bonds 2 $ 1,363,836 $ 1,288,986 Corporate commercial paper 2 412,372 498,048 Obligations of U.S. government agencies 2 13,005 12,977 Available-for-sale investments 1,789,213 1,800,011 Money market funds 1 42,171 105,656 Certificate of deposit N/A 6,759 6,760 Cash N/A 6,389 5,812 Total cash and investments in marketable securities $ 1,844,532 $ 1,918,239 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. 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. 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. During the three months ended March 31, 2019 and 2018, there were no transfers between Level 1 and Level 2 of the fair value hierarchy. Additionally, as of March 31, 2019, based on a discounted cash flow analysis using Level 3 inputs including financial discount rates, we believe the fair value of the $250.0 million in principal amount of our 7.75% senior secured notes due October 2020 is approximately $257.2 million. We may redeem some or all of these notes at a redemption price equal to 102

Inventory

Inventory	3 Months Ended
	Mar. 31, 2019
Inventory Disclosure [Abstract]
Inventory	Note 3 — Inventory Inventory consists of the following (in thousands): March 31, 2019 December 31, 2018 Raw materials $ 1,688 $ 1,846 Work-in-process 8,932 6,403 Finished goods 1,158 3,132 Total inventory $ 11,778 $ 11,381 Inventory is generally manufactured upon receipt of firm purchase orders from our collaboration partners. Inventory includes direct materials, direct labor, and manufacturing overhead and cost is determined on a first-in, first-out basis for raw materials and on a specific identification basis for work-in-process and finished goods. Inventory is valued at the lower of cost or net realizable value and defective or excess inventory is written down to net realizable value based on historical experience or projected usage. Inventory related to our research and development activities is expensed as manufactured by us or when purchased.

Leases

Leases	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
Leases	Note 4 — Leases As discussed in Note 1, we adopted ASC 842 as of January 1, 2019. Prior period amounts have not been adjusted and continue to be reported in accordance with our historic accounting under ASC 840. We determine if an arrangement contains a lease at the inception of the arrangement. We include operating leases in operating lease right-of-use assets, operating lease liabilities, current portion, and operating lease liabilities, less current portion in our Condensed Consolidated Balance Sheets as of March 31, 2019. Right-of-use assets represent our right to use an underlying asset for the lease term and lease liabilities represent our obligation to make lease payments arising from the lease. We recognize operating lease right-of-use assets and liabilities at the lease commencement date based on the present value of lease payments over the expected lease term. In determining the present value of lease payments, we use our incremental borrowing rate based on the information available at the lease commencement date. However, in determining the present value of our lease payments for leases in effect when we adopted ASC 842, we used our incremental borrowing rate as of January 1, 2019. We have elected to recognize lease incentives, such as tenant improvement allowances, at the lease commencement date as a reduction of the right-of-use asset and lease liability to the extent that the lease provides a specified fixed or maximum level of reimbursement and we are reasonably certain to incur reimbursable costs at least equaling such amounts. For leases in effect as of January 1, 2019, we recognized our lease incentives as part of our transition adjustment. Our expected lease terms may include options to extend or terminate the lease when it is reasonably certain that we will exercise any such options. We recognize lease expense on a straight-line basis over the expected lease term. For our facilities leases, we have elected a practical expedient provided by ASC 842 to account for the lease and non-lease components, such as common area maintenance charges, as a single lease component. In August 2017, we entered into a Lease Agreement (the Mission Bay Lease) with ARE-San Francisco No. 19, LLC (ARE) and terminated our sublease with Pfizer, Inc., effectively extending our lease term from 2020 to 2030 for our 137,046 square foot corporate office and R&D facility located at 455 Mission Bay Boulevard, San Francisco, California (the Mission Bay Facility). The term of the Mission Bay Lease commenced on September 1, 2017, and will expire January 31, 2030, subject to our right to extend the term of the lease for two consecutive five-year periods, which we have excluded from our determination of the lease term. The monthly base rent for the Mission Bay Facility will escalate over the term of the lease at various intervals. During the term of the Mission Bay Lease, we are responsible for paying our share of operating expenses specified in the lease, including utilities, common area maintenance, insurance and taxes. The Mission Bay Lease also obligates us to rent from ARE a total of an additional approximately 15,000 square feet of space at the Mission Bay Facility. During the three months ended March 31, 2019, ARE delivered 2,690 square feet of space, and therefore we recognized a right-of-use asset and lease liability of $1.3 million for this space. The Mission Bay Lease includes various covenants, indemnities, defaults, termination rights, security deposits and other provisions customary for lease transactions of this nature. In May 2018, we entered into a Lease Agreement (the Third Street Lease) with Kilroy Realty Finance Partnership, L.P. to lease 135,936 square feet of space located at 360 Third Street, San Francisco, California (the Third Street Facility) from June 2018 to January 31, 2030, subject to our right to extend the term for a consecutive five-year period, which we have excluded from our determination of the lease term. An initial 1,726 square feet was delivered in June 2018, and a total of 67,105 square feet for two additional spaces was delivered in December 2018. The remaining space will be delivered in phases during 2019. The Third Street Lease will provide us additional facilities to support increased personnel for our San Francisco-based R&D activities. Our fixed monthly base rent on an industrial gross lease basis includes certain expenses and property taxes paid directly by the landlord and will escalate each year over the term at specified intervals. We have a onetime right of first offer with respect to certain additional rental space at the Third Street Facility. The Third Street Lease includes various covenants, indemnities, defaults, termination rights, security deposits and other provisions customary for lease transactions of this nature. The components of lease costs, which were included in Operating expenses in our Condensed Consolidated Statements of Operations, were as follows (in thousands): Three months ended March 31, 2019 2018 Operating lease cost $ 2,957 $ 1,838 Variable lease cost 1,273 1,093 Total lease costs $ 4,230 $ 2,931 Cash paid for amounts included in the measurement of lease liabilities for the three months ended March 31, 2019 was $1.8 million, which we included in Net cash used in operating activities in our Condensed Consolidated Statement of Cash Flows. As of March 31, 2019, the maturities of our operating lease liabilities were as follows (in thousands): Year ending December 31, 2019 (Nine months ended) $ 5,749 2020 9,690 2021 12,671 2022 13,087 2023 13,515 2024 13,956 2025 and thereafter 78,233 Total lease payments 146,901 Less: portion representing interest (44,681 ) Less: lease incentives (5,547 ) Operating lease liabilities 96,673 Less: current portion (1,649 ) Operating lease liabilities, less current portion $ 95,024 As of March 31, 2019, we are entitled to an additional lease incentive of $4.1 million, which we present in other current assets on our Condensed Consolidated Balance Sheet, representing the excess of our lease incentive over the current portion of the lease liability for that lease. As of March 31, 2019, the weighted-average remaining lease term is 10.8 years and the weighted-average discount rate used to determine the operating lease liability was 6.5%.

Liability Related to Sale of Fu

Liability Related to Sale of Future Royalties	3 Months Ended
	Mar. 31, 2019
Liability Related To Sale Of Potential Future Royalties [Abstract]
Liability Related to Sale of Future Royalties	Note 5 — Liability Related to Sale of Future Royalties On February 24, 2012, we entered into a Purchase and Sale Agreement (the Purchase and Sale Agreement) with RPI Finance Trust (RPI), an affiliate of Royalty Pharma, pursuant to which we sold, and RPI purchased, our right to receive royalty payments (the Royalty Entitlement) arising from the worldwide net sales, from and after January 1, 2012, of (a) CIMZIA ® ® ® ® ® ® ® ® We periodically assess the estimated royalty payments to RPI from UCB and Roche and to the extent such payments are greater or less than our initial estimates or the timing of such payments is materially different from our original estimates, we will prospectively adjust the amortization of the Royalty Obligation. From inception through 2017, our estimate of the total interest expense on the Royalty Obligation resulted in an effective annual interest rate of approximately 17%. During the three months ended December 31, 2017, our estimate of the effective annual interest rate over the life of the agreement increased to 17.6%, which resulted in a prospective interest rate of ® The Purchase and Sale Agreement grants RPI the right to receive certain reports and other information relating to the Royalty Entitlement and contains other representations and warranties, covenants and indemnification obligations that are customary for a transaction of this nature. To our knowledge, we are currently in compliance with these provisions of the Purchase and Sale Agreement; however, if we were to breach our obligations, we could be required to pay damages to RPI that are not limited to the purchase price we received in the sale transaction.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2019
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	Note 6 — Commitments and Contingencies Legal Matters From time to time, we are involved in lawsuits, arbitrations, claims, investigations and proceedings, consisting of intellectual property, commercial, employment and other matters, which arise in the ordinary course of business. We make provisions for liabilities when it is both probable that a liability has been incurred and the amount of the loss can be reasonably estimated. Such provisions are reviewed at least quarterly and adjusted to reflect the impact of settlement negotiations, judicial and administrative rulings, advice of legal counsel, and other information and events pertaining to a particular case. Litigation is inherently unpredictable. If any unfavorable ruling were to occur in any specific period, there exists the possibility of a material adverse impact on the results of our operations of that period and on our cash flows and liquidity. On October 30, 2018, we and our CEO and CFO were named in a putative securities class action entitled, Mulquin v. Nektar Therapeutics et. al., N.D. Cal. Also, on February 13, 2019, and February 18, 2019, shareholder derivative complaints were filed in the U.S. District Court for the District of Delaware naming the CEO, CFO and certain members of Nektar’s board. Both the class action and shareholder derivative actions assert, among other things, that for a period beginning at least from November 11, 2017 through October 2, 2018, our stock was inflated due to alleged misrepresentations about the efficacy and safety of NKTR-214. These cases are in the early stages. Accordingly, we cannot reasonably estimate any range of potential future charges, and we have not recorded any accrual for a contingent liability associated with these legal proceedings. 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. 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 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. Because the aggregate amount of any potential indemnification obligation is not a stated amount, the overall maximum amount of any such obligations cannot be reasonably estimated. No liabilities have been recorded for these obligations in our Condensed Consolidated Balance Sheets at either March 31, 2019 or December 31, 2018.

License and Collaboration Agree

License and Collaboration Agreements	3 Months Ended
	Mar. 31, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
License and Collaboration Agreements	Note 7 — License and Collaboration Agreements We have entered into various collaboration agreements including license agreements and collaborative research, development and commercialization agreements with various pharmaceutical and biotechnology companies. Under these collaboration arrangements, we are entitled to receive license fees, upfront payments, milestone and other contingent payments, royalties, sales milestone payments, and payments for the manufacture and supply of our proprietary PEGylation materials and/or reimbursement for research and development activities. All of our collaboration agreements are generally cancelable by our partners without significant financial penalty. Our costs of performing these services are generally included in research and development expense, except that costs for product sales to our collaboration partners are included 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 March 31, Partner Drug or Drug Candidate 2019 2018 Baxalta Incorporated/Takeda ADYNOVATE ® 20 10,011 Eli Lilly and Company NKTR-358 2,500 2,354 Amgen, Inc. Neulasta ® 1,250 1,250 Other 434 112 License, collaboration and other revenue $ 4,204 $ 13,727 In the three months ended March 31, 2019 and 2018, we recognized $19.6 million and $28.0 million of revenue for performance obligations that we had satisfied in prior periods, respectively. This amount includes all of our royalty revenue and non-cash royalty revenue because these royalties substantially relate to the licenses that we had previously granted. This amount also includes the $10.0 million development milestone payment earned and received from Baxalta in the three months ended March 31, 2018 described below. The following table presents the changes in our deferred revenue balance from our collaboration agreements during the three months ended March 31, 2019 (in thousands): Three months ended March 31, 2019 Deferred revenue—December 31, 2018 $ 24,636 Recognition of previously unearned revenue (4,204 ) Deferred revenue—March 31, 2019 $ 20,432 Our balance of deferred revenue contains the transaction price from our collaboration agreements allocated to performance obligations which are partially unsatisfied. We expect to recognize approximately $11.1 million of our deferred revenue over the next twelve months and recognize approximately one-third of the remaining $9.3 million over the following twelve months. As of March 31, 2019, 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 Lilly 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 months ended March 31, 2019, except as described below. Bristol-Myers Squibb (BMS) : Bempegaldesleukin, also referred to as NKTR-214 On February 13, 2018, we entered into a Strategic Collaboration Agreement (BMS Collaboration Agreement) and a Share Purchase Agreement with BMS, both of which became effective on April 3, 2018. Pursuant to these agreements, we and BMS will jointly develop NKTR-214, including, without limitation, in combination with BMS’s Opdivo ® ® ® In accordance with the agreement, the parties will share development costs for NKTR-214 in combination with Opdivo ® , 67.5% of costs to BMS and 32.5% to Nektar, and for NKTR-214 in a triplet combination with Opdivo ® and Yervoy ® , 78% of costs to BMS and 22% to Nektar. The parties will share costs for the production of NKTR-214, 35% of costs to BMS and 65% to Nektar. The BMS Collaboration Agreement superseded and replaced the Clinical Trial Agreement we entered into with BMS in September 2016 to develop NKTR-214 in combination with Opdivo ® Upon the effective date of the BMS Collaboration Agreement in April 2018, BMS paid us a non-refundable upfront cash payment of $1.0 billion. We are eligible to receive additional cash payments up to a total of approximately $1.4 billion 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. 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 months ended March 31, 2019 and 2018, we recorded $28.8 million and $2.3 million, respectively, as a reduction of research and development expenses for BMS’ share of our expenses, net of our share of BMS’ expenses. As of March 31, 2019, we have recorded a receivable of $28.4 million from BMS in accounts receivable in our Condensed Consolidated Balance Sheet. We analogized to ASC 606 for the accounting for our two performance obligations, consisting of the delivery of the licenses to develop and commercialize NKTR-214 and our participation on joint steering and other collaboration committees. We determined that our committee participation is not material. 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 based on the closing date price of our common stock of $99.36, adjusted for a discount for lack of marketability reflecting the unregistered nature of the shares. We allocated the remaining $1,059.8 million to the transaction price of the collaboration agreement. We consider the future potential development, regulatory and sales milestones of up to approximately $1.8 billion to be variable consideration. We excluded these milestones from the transaction price as of March 31, 2019 due to the significant uncertainties involved with clinical development and regulatory approval. We will re-evaluate the transaction price at each reporting period and as uncertain events are resolved or other changes in circumstances occur. Accordingly, we allocated the entire transaction price of $1,059.8 million to the granting of the licenses and therefore recognized $1,059.8 million for the year ended December 31, 2018 as license, collaboration and other revenue. Eli Lilly and Company (Lilly ): NKTR-358 Effective August 23, 2017, we entered into a worldwide license agreement with Eli Lilly and Company (Lilly) to co-develop NKTR-358, a novel immunological drug candidate that we invented. The 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 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 ongoing Phase 1 clinical development obligation and our drug product development obligation as the significant performance obligations in the arrangement. The valuation of each performance obligation involves significant estimates and assumptions, including but not limited to, expected market opportunity and pricing, assumed royalty rates, clinical trial costs, timelines and likelihood of success; in each case these estimates and assumptions covering long time periods. We determined the selling price for the license based on a discounted cash flow analysis of projected revenues from NKTR-358 and development and commercial costs using a discount rate based on a market participant’s weighted average cost of capital adjusted for forecasting risk. We determined the selling prices for our Phase 1 clinical development and drug product development deliverables based on the nature of the services to be performed and estimates of the associated efforts and third-party rates for similar services. Although we are entitled to significant development milestones under this arrangement, as of March 31, 2019, we have excluded such milestones from the transaction price due to the significant uncertainties involved with clinical development. We have therefore determined the transaction price to consist of the upfront payment of $150.0 million in September 2017. 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 the Phase 1 clinical development and $6.5 million to the drug product development. We recognized the $125.9 million of revenue allocated to the license upon the effective date of the license agreement in August 2017, since we determined that the license was a right to use our intellectual property, for which, as of the effective date, we had provided all necessary information to Lilly to benefit from the license and the license term had begun. We recognize revenue for the Phase 1 clinical development and drug product development using an input method, using costs incurred, as this method depicts our progress towards providing Lilly with the results of clinical trials and drug production processes. As of March 31, 2019, we have deferred revenue of approximately $5.8 million related to this agreement, which we expect to recognize through December 2019, the estimated end of our performance obligations under this agreement. Baxalta Incorporated/Takeda : Hemophilia We are a party to an exclusive research, development, license and manufacturing and supply agreement with Baxalta Incorporated (Baxalta), a subsidiary of Takeda Pharmaceutical Company Ltd. (Takeda), entered into in September 2005 to develop products designed to improve therapies for Hemophilia A patients using our PEGylation technology. Under the terms of the agreement, we are entitled to research and development funding for our active programs, which are now complete for Factor VIII, and are responsible for supplying Takeda with its requirements for our proprietary materials. Takeda is responsible for all clinical development, regulatory, and commercialization expenses. The agreement is terminable by the parties under customary conditions. This Hemophilia A program includes ADYNOVATE ® In December 2018, we earned an additional $10.0 million milestone for annual sales of ADYNOVATE ® /ADYNOVI TM reaching a certain specified amount. In October 2017, we entered into a right to sublicense agreement with Baxalta, under which we granted to Baxalta the right to grant a nonexclusive sublicense to certain patents that were previously exclusively licensed to Baxalta under our 2005 agreement. Under the right to sublicense agreement, Baxalta paid us $12.0 million in November 2017 and agreed to pay us single digit royalty payments based upon net sales of the products covered under the sublicense throughout the term of the agreement. Our remaining unsatisfied performance obligation consists of our ongoing supply of PEGylation materials at a price less than the standalone selling price of these materials. As of March 31, 2019, our deferred revenue from this arrangement is not significant. Amgen, Inc .: Neulasta ® In October 2010, we amended and restated an existing supply and license agreement by entering into a supply, dedicated suite and manufacturing guarantee agreement (the Amended and Restated Agreement) and a license agreement with Amgen Inc. and Amgen Manufacturing, Limited (together referred to as Amgen). Under the terms of the Amended and Restated Agreement, we received a $50.0 million payment in the fourth quarter of 2010 in return for our guaranteeing the supply of certain quantities of our proprietary PEGylation materials to Amgen. We determined that our obligation to manufacture and supply our PEGylation materials and to maintain the dedicated manufacturing suite solely for the production of such materials for Amgen represented an obligation to stand ready to manufacture such materials. We concluded that we should recognize revenue based on the passage of time as this method depicts the satisfaction of Amgen’s right to require production of PEGylation materials at any time. As of March 31, 2019, we have deferred revenue of approximately $7.9 million related to this agreement, which we expect to recognize through October 2020, the estimated end of our obligations under this agreement. AstraZeneca AB : MOVANTIK ® (naloxegol oxalate), previously referred to as naloxegol and NKTR-118 In September 2009, we entered into an agreement with AstraZeneca AB (AstraZeneca) under which we granted AstraZeneca a worldwide, exclusive license under our patents and other intellectual property to develop, market, and sell MOVANTIK ® ® ® ® ® In March 2016, AstraZeneca announced that it had entered into an agreement with ProStrakan Group plc, a subsidiary of Kyowa Hakko Kirin Co. Ltd. (Kirin), granting Kirin exclusive marketing rights to MOVENTIG ® Other In addition, as of March 31, 2019, we have a number of other collaboration agreements, including with our collaboration partners UCB Pharma and Halozyme Therapeutics, Inc., under which we are entitled to up to a total of $45.5 million of development milestone payments upon achievement of certain development objectives, 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. As of March 31, 2019, we have deferred revenue of approximately $6.0 million related to these other collaboration agreements.

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	Note 8 — Stock-Based Compensation Total stock-based compensation expense was recognized in our Condensed Consolidated Statements of Operations as follows (in thousands): Three months ended March 31, 2019 2018 Cost of goods sold $ 820 $ 1,131 Research and development 16,623 12,094 General and administrative 7,942 6,724 Total stock-based compensation $ 25,385 $ 19,949 During the three months ended March 31, 2019 and 2018, we granted 20,455 and 209,700 stock options, respectively, and these options had a weighted average grant-date fair value of $25.51 per share and $68.88 per share, respectively. During the three months ended March 31, 2019 and 2018, we granted 132,820 and 10,000 RSUs, respectively. As a result of stock issuances under our equity compensation plans, during the three months ended March 31, 2019 and 2018, we issued 698,000 and 2,854,816

Net Loss Per Share

Net Loss Per Share	3 Months Ended
	Mar. 31, 2019
Earnings Per Share [Abstract]
Net Loss Per Share	Note 9 — Net Loss Per Share Basic net loss per share is calculated based on the weighted-average number of common shares outstanding during the periods presented. Diluted net loss per share is calculated 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, the net loss available to common stockholders is equal to the reported net loss. For the three months ended March 31, 2019 and 2018, 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 months ended March 31, 2019 and 2018, potentially dilutive securities consisted of common shares underlying outstanding stock options and RSUs. During the three months ended March 31, 2019 and 2018, there were weighted average outstanding stock options and RSUs of 18.9 million and 20.0 million shares, respectively.

Organization and Summary of S_2

Organization and Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2019
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 utilize our 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 treatments for cancer, autoimmune disease and chronic pain. 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 March 31, 2019, we had approximately $1.8 billion in cash and investments in marketable securities and debt of $250.0 million in principal of senior secured notes due in October 2020.
Basis of Presentation and Principles of Consolidation	Basis of Presentation and Principles of Consolidation Our consolidated financial statements include the financial position, results of operations and cash flows of our wholly-owned subsidiaries: Nektar Therapeutics (India) Private Limited (Nektar India), Inheris Pharmaceuticals, Inc. and Nektar Therapeutics UK Limited. All intercompany accounts and transactions have been eliminated 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, certain footnotes or other financial information that are normally required by U.S. generally accepted accounting principles (GAAP) for annual periods can be condensed or omitted. 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. Translation gains and losses are included in accumulated other comprehensive loss in the stockholders’ equity section of the 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, neither of which were significant during the three months ended March 31, 2019 and 2018. In addition, there were no significant reclassifications out of accumulated other comprehensive loss to the statements of operations during the three months ended March 31, 2019 and 2018. The accompanying Condensed Consolidated Financial Statements are unaudited. The Condensed Consolidated Balance Sheet data as of December 31, 2018 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, 2018 filed with the SEC on March 1, 2019. 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, 2018. 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. Our estimates include those related to estimated selling prices of performance obligations and estimates of variable consideration in collaboration agreements, estimated royalty revenue, other estimates required for revenue recognition as described further below, the net realizable value of inventory, the impairment of investments, goodwill and long-lived assets, contingencies, accrued clinical trial, contract manufacturing and other expenses, estimated non-cash royalty revenue and non-cash interest expense from our liability related to our sale of future royalties, stock-based compensation, and ongoing litigation, among other estimates. We base our estimates on historical experience and on other assumptions that management believes are reasonable under the circumstances. These estimates form the basis for making judgments about the carrying values of assets and liabilities when these values are not readily apparent from other sources. As appropriate, estimates are assessed each period and updated to reflect current information and any changes in estimates will generally be reflected 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 We are dependent on our suppliers and contract manufacturers to provide raw materials and drugs of appropriate quality and reliability and to meet applicable contract and regulatory requirements. In certain cases, we rely on single sources of supply of one or more critical materials. Consequently, in the event that supplies are delayed or interrupted for any reason, our ability to develop and produce our drug candidates or our ability to meet our supply obligations could be significantly impaired, which could have a material adverse effect on our business, financial condition and results of operations.
Adoption of New Accounting Principle	Adoption of New Accounting Principle On January 1, 2019, we adopted Accounting Standards Codification (ASC) 842, Leases Leases Under ASC 842, an entity recognizes a right-of-use asset and a corresponding lease liability, measured as the present value of the lease payments, for leases with terms greater than one year. As a result of the adoption of ASC 842 on January 1, 2019, we recorded right-of-use assets of $83.5 million and lease liabilities of $96.2 million with no cumulative effect adjustment to accumulated deficit. Our lease arrangements are further described in Note 4.
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 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 Revenue from Contracts with Customers
Revenue Recognition	Revenue Recognition For elements of those arrangements that we determine should be accounted for under ASC 606, we assess which activities in our collaboration agreements are performance obligations that should be accounted for separately and determine the transaction price of the arrangement, which includes the assessment of the probability of achievement of future milestones and other potential consideration. For arrangements that include multiple performance obligations, such as granting a license or performing contract research and development activities or participation on joint steering or other committees, we allocate upfront and milestone payments under a relative standalone selling price method. Accordingly, we develop assumptions that require judgment to determine the standalone selling price for each performance obligation identified in the contract. These key assumptions may include revenue forecasts, clinical development timelines and costs, discount rates and probabilities of clinical and regulatory success. Product Sales Product sales are primarily derived from manufacturing and supply agreements with our customers. We have assessed our current manufacturing and supply arrangements and have generally determined that they provide the customer an option to purchase our proprietary PEGylation materials. Accordingly, we treat each purchase order as a discrete exercise of the customer’s option (i.e. a separate contract) rather than as a component of the overall arrangement. The pricing for the manufacturing and supply is generally at a fixed price and may be subject to annual producer price index (PPI) adjustments. We invoice and recognize product sales when title and risk of loss pass to the customer, which generally occurs upon shipment. Customer payments are generally due 30 days from receipt of 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, we are entitled to royalties from our collaboration partners based on the net sales of their approved drugs that are marketed and sold in one or more countries where we hold royalty rights. For arrangements that include sales-based royalties, including commercial milestone payments based on the level of sales, we have concluded that the license is the predominant item to which the royalties relate. 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. We present commercial milestone payments within license, collaboration and other revenue. 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 or filing for or receipt of regulatory approval, 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. Our partners generally pay development milestones subsequent to achievement of the triggering event. Research and Development Services : For amounts allocated to our research and development obligations in a collaboration arrangement, we recognize revenue over time using a proportional performance model, representing the transfer of goods or services as we perform activities over the term of the agreement.
Research and Development Expense	Research and Development Expense Research and development costs are expensed as incurred and include salaries, benefits and other operating costs such as outside services, supplies and allocated overhead costs. We perform research and development 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 clinical joint development collaboration, such as our collaboration with Bristol-Myers Squibb Company (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 total estimated cost of the treatment phase on a per patient basis and we 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 to be considered the delivery of a good, as evidenced by predictive or contractually required yields in the production process, 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. Advance payments for goods or services that will be used or rendered for future research and development activities are capitalized as prepaid expenses and recognized as expense as the related goods are delivered or the related services are performed. We base our estimates on the best information available at the time. However, additional information may become available to us 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. Such increases or decreases in cost are generally considered to be changes in estimates and will be reflected in research and development expenses in the period identified.
Long-Lived Assets	Long-Lived Assets We assess the impairment of long-lived assets whenever events or changes in business circumstances indicate that the carrying amounts of the assets may not be fully recoverable. In the case of property, plant and equipment and right-of-use assets, we determine whether there has been an impairment by comparing the carrying value of the asset to the anticipated undiscounted net cash flows associated with the asset. If such cash flows are less than the carrying value, we write down the asset to its fair value, which may be measured as anticipated discounted net cash flows associated with the asset. In the case of goodwill impairment, we compare the carrying value of the reporting unit to its fair value, which we generally measure using market capitalization for our single reporting unit. If an impairment exists, we write down goodwill such that the carrying value of the reporting units equals its fair value.
Income Taxes	Income Taxes For the three months ended March 31, 2019 and 2018, we recorded an income tax provision for our Nektar India operations at an effective tax rate of approximately 29% and 31%, respectively. Due to our unrealized gain on available-for-sale securities in the three months ended March 31, 2019, we recorded a tax provision against such gain with an offsetting tax benefit in continuing operations of $1.1 million. The U.S. federal deferred tax assets generated from our net operating losses have been fully reserved, as we believe it is not more likely than not that the benefit will be realized.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In November 2018, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update 2018-18: Clarifying the Interaction between Topic 808 and Topic 606 (ASU 2018-18). The guidance clarifies that certain transactions between collaborative arrangement participants should be accounted for as revenue under ASC 606 when the collaborative arrangement participant is a customer for a promised good or service that is distinct within the collaborative arrangement. The guidance also precludes entities from presenting amounts related to transactions with a collaborative arrangement participant that is not a customer as revenue, unless those transactions are directly related to third-party sales. ASU 2018-18 is effective in the first quarter of 2020 and should be applied retrospectively to January 1, 2018, when we adopted ASC 606. Early adoption is permitted. We are evaluating the effect of adoption, but we do not expect a material effect on our revenue.
Inventory	Inventory is valued at the lower of cost or net realizable value and defective or excess inventory is written down to net realizable value based on historical experience or projected usage. Inventory related to our research and development activities is expensed as manufactured by us or when purchased.
Liability Related to Sale of Future Royalties	We periodically assess the estimated royalty payments to RPI from UCB and Roche and to the extent such payments are greater or less than our initial estimates or the timing of such payments is materially different from our original estimates, we will prospectively adjust the amortization of the Royalty Obligation.

Cash and Investments in Marke_2

Cash and Investments in Marketable Securities (Tables)	3 Months Ended
	Mar. 31, 2019
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 March 31, 2019 December 31, 2018 Cash and cash equivalents $ 106,752 $ 194,905 Short-term investments 1,281,913 1,140,445 Long-term investments 455,867 582,889 Total cash and investments in marketable securities $ 1,844,532 $ 1,918,239
Portfolio of Cash and Investments in Marketable Securities	Our portfolio of cash and investments in marketable securities includes (in thousands): Estimated Fair Value at Fair Value Hierarchy Level March 31, 2019 December 31, 2018 Corporate notes and bonds 2 $ 1,363,836 $ 1,288,986 Corporate commercial paper 2 412,372 498,048 Obligations of U.S. government agencies 2 13,005 12,977 Available-for-sale investments 1,789,213 1,800,011 Money market funds 1 42,171 105,656 Certificate of deposit N/A 6,759 6,760 Cash N/A 6,389 5,812 Total cash and investments in marketable securities $ 1,844,532 $ 1,918,239

Inventory (Tables)

Inventory (Tables)	3 Months Ended
	Mar. 31, 2019
Inventory Disclosure [Abstract]
Inventory	Inventory consists of the following (in thousands): March 31, 2019 December 31, 2018 Raw materials $ 1,688 $ 1,846 Work-in-process 8,932 6,403 Finished goods 1,158 3,132 Total inventory $ 11,778 $ 11,381

Leases (Tables)

Leases (Tables)	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
Components of Lease Costs Included in Operating Expenses	The components of lease costs, which were included in Operating expenses in our Condensed Consolidated Statements of Operations, were as follows (in thousands): Three months ended March 31, 2019 2018 Operating lease cost $ 2,957 $ 1,838 Variable lease cost 1,273 1,093 Total lease costs $ 4,230 $ 2,931
Summary of Maturities of Operating Lease Liabilities	As of March 31, 2019, the maturities of our operating lease liabilities were as follows (in thousands): Year ending December 31, 2019 (Nine months ended) $ 5,749 2020 9,690 2021 12,671 2022 13,087 2023 13,515 2024 13,956 2025 and thereafter 78,233 Total lease payments 146,901 Less: portion representing interest (44,681 ) Less: lease incentives (5,547 ) Operating lease liabilities 96,673 Less: current portion (1,649 ) Operating lease liabilities, less current portion $ 95,024

License and Collaboration Agr_2

License and Collaboration Agreements (Tables)	3 Months Ended
	Mar. 31, 2019
Organization Consolidation And Presentation Of Financial Statements [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 March 31, Partner Drug or Drug Candidate 2019 2018 Baxalta Incorporated/Takeda ADYNOVATE ® 20 10,011 Eli Lilly and Company NKTR-358 2,500 2,354 Amgen, Inc. Neulasta ® 1,250 1,250 Other 434 112 License, collaboration and other revenue $ 4,204 $ 13,727
Changes in Deferred Revenue Balance from Collaboration Agreements	The following table presents the changes in our deferred revenue balance from our collaboration agreements during the three months ended March 31, 2019 (in thousands): Three months ended March 31, 2019 Deferred revenue—December 31, 2018 $ 24,636 Recognition of previously unearned revenue (4,204 ) Deferred revenue—March 31, 2019 $ 20,432

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation Expense	Total stock-based compensation expense was recognized in our Condensed Consolidated Statements of Operations as follows (in thousands): Three months ended March 31, 2019 2018 Cost of goods sold $ 820 $ 1,131 Research and development 16,623 12,094 General and administrative 7,942 6,724 Total stock-based compensation $ 25,385 $ 19,949

Organization and Summary of S_3

Organization and Summary of Significant Accounting Policies - Additional Information (Detail)	Jan. 01, 2019USD ($)	Mar. 31, 2019USD ($)Segment	Mar. 31, 2018USD ($)	Dec. 31, 2018USD ($)
Organization And Summary Of Significant Accounting Policies [Line Items]
Cash and investments in marketable securities		$ 1,844,532,000		$ 1,918,239,000
Senior secured notes		$ 250,000,000
Senior secured notes, maturity date		Oct. 5, 2020
Number of business segment | Segment		1
Accounts receivable from contracts with customers		$ 14,500,000		24,200,000
Accounts receivable for expense reimbursements from collaboration partner		42,894,000		43,213,000
Operating lease, right-of-use assets	$ 83,500,000	83,475,000
Operating lease, lease liabilities	96,200,000	96,673,000
Cumulative effect adjustment to accumulated deficit			$ 12,577,000
Tax provision on unrealized gain on available-for-sale securities, offset by benefit in continuing operations		$ 1,100,000
India
Organization And Summary Of Significant Accounting Policies [Line Items]
Effective income tax rate		29.00%	31.00%
ASC 842 [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Cumulative effect adjustment to accumulated deficit	$ 0
Collaboration Partner [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Accounts receivable for expense reimbursements from collaboration partner		$ 28,400,000		$ 19,000,000

Cash and Investments in Marke_3

Cash and Investments in Marketable Securities - Cash and Investments in Marketable Securities, Including Cash Equivalents (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Cash and cash equivalents	$ 106,752	$ 194,905
Short-term investments	1,281,913	1,140,445
Long-term investments	455,867	582,889
Total cash and investments in marketable securities	$ 1,844,532	$ 1,918,239

Cash and Investments in Marke_4

Cash and Investments in Marketable Securities - Additional Information (Detail) - USD ($)	Mar. 31, 2019	Dec. 31, 2018	Oct. 05, 2015	Mar. 31, 2019	Mar. 31, 2018
Cash and Investments in Marketable Securities [Line Items]
Maximum maturity term for debt securities investment				Two years or less
Weighted average maturity term for debt securities investment				One year or less
Available-for-sale securities, sold				$ 0	$ 11,963,000
Senior secured notes, maturity date				Oct. 5, 2020
Level 1 to level 2 transfers	$ 0			$ 0	0
Level 2 to level 1 transfers	0			0	$ 0
Senior secured notes, principal amount	$ 250,000,000			$ 250,000,000
Senior Notes [Member] | Level 3 [Member]
Cash and Investments in Marketable Securities [Line Items]
Debt instrument redemption terms				We may redeem some or all of these notes at a redemption price equal to 102% of the principal amount of the notes if the redemption date is prior to October 5, 2019, or 100% of the principal amount of the notes if the redemption date is on or after October 5, 2019, plus, in each case, accrued and unpaid interest to the applicable redemption date.
Senior Notes [Member] | 7.75% Senior Secured Notes Due October 2020 [Member]
Cash and Investments in Marketable Securities [Line Items]
Senior secured notes, interest rate			7.75%
Senior secured notes, maturity date			Oct. 5, 2020
Minimum cash and investments in marketable securities to be maintained			$ 60,000,000
Senior Notes [Member] | 7.75% Senior Secured Notes Due October 2020 [Member] | Level 3 [Member]
Cash and Investments in Marketable Securities [Line Items]
Senior secured notes, interest rate	7.75%			7.75%
Senior secured notes, maturity date				Oct. 5, 2020
Senior secured notes, principal amount	$ 250,000,000			$ 250,000,000
Senior notes, fair value	$ 257,200,000			$ 257,200,000
Senior Notes [Member] | 7.75% Senior Secured Notes Redemption Date Before October 5, 2019 [Member] | Level 3 [Member]
Cash and Investments in Marketable Securities [Line Items]
Debt redemption price percentage of principal amount				102.00%
Senior Notes [Member] | 7.75% Senior Secured Notes Redemption Date After October 5, 2019 [Member] | Level 3 [Member]
Cash and Investments in Marketable Securities [Line Items]
Debt redemption price percentage of principal amount				100.00%
Minimum [Member]
Cash and Investments in Marketable Securities [Line Items]
Long term investment maturity period	1 year	1 year
Maximum [Member]
Cash and Investments in Marketable Securities [Line Items]
Long term investment maturity period	2 years	2 years

Cash and Investments in Marke_5

Cash and Investments in Marketable Securities - Portfolio of Cash and Investments in Marketable Securities (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	$ 1,789,213	$ 1,800,011
Cash	6,389	5,812
Total cash and investments in marketable securities	1,844,532	1,918,239
Corporate Notes and Bonds [Member] | Fair Value Hierarchy Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	1,363,836	1,288,986
Corporate Commercial Paper [Member] | Fair Value Hierarchy Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	412,372	498,048
Obligations of U.S. government agencies [Member] | Fair Value Hierarchy Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	13,005	12,977
Money Market Funds [Member] | Fair Value Hierarchy Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	42,171	105,656
Certificates of Deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	$ 6,759	$ 6,760

Inventory - Inventory (Detail)

Inventory - Inventory (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Inventory Disclosure [Abstract]
Raw materials	$ 1,688	$ 1,846
Work-in-process	8,932	6,403
Finished goods	1,158	3,132
Total inventory	$ 11,778	$ 11,381

Leases - Additional Information

Leases - Additional Information (Detail) $ in Millions	1 Months Ended			3 Months Ended
	Dec. 31, 2018ft²Space	May 31, 2018ft²	Aug. 31, 2017ft²yr	Mar. 31, 2019USD ($)ft²	Jun. 30, 2018ft²
Lessee Lease Description [Line Items]
Cash paid for amounts included in the measurement of lease liabilities | $				$ 1.8
Operating lease liability, weighted-average remaining lease term				10 years 9 months 18 days
Operating lease liability, weighted-average discount rate, percent				6.50%
Other Current Assets [Member]
Lessee Lease Description [Line Items]
Additional operating lease incentive | $				$ 4.1
ARE-San Francisco No. 19, LLC [Member] | Mission Bay Lease [Member]
Lessee Lease Description [Line Items]
Extended lease term start year			2020
Lease expiration year			2030
Lease space | ft²			137,046	2,690
Lease commencement date			Sep. 1, 2017
Lessee operating lease, lease expiration date			Jan. 31, 2030
Lease, option to extend, description				The term of the Mission Bay Lease commenced on September 1, 2017, and will expire January 31, 2030, subject to our right to extend the term of the lease for two consecutive five-year periods, which we have excluded from our determination of the lease term.
Number of consecutive 5 year terms to extend lease | yr			2
Lease extension term			5 years
Additional space required to be leased in the future | ft²			15,000
Recognized a right-of-use asset and lease liability | $				$ 1.3
Kilroy Realty Finance Partnership, L.P [Member] | Third Street Lease [Member]
Lessee Lease Description [Line Items]
Lease space | ft²	67,105	135,936			1,726
Lessee operating lease, lease expiration date		Jan. 31, 2030
Lease, option to extend, description				our right to extend the term for a consecutive five-year period
Lease extension term		5 years
Lease term start month and year		2018-06
Number of additional spaces delivered | Space	2
Remaining square feet of space expected delivery year		2019

Leases - Components of Lease Co

Leases - Components of Lease Costs Included in Operating Expenses (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Lease Cost [Abstract]
Operating lease cost	$ 2,957	$ 1,838
Variable lease cost	1,273	1,093
Total lease costs	$ 4,230	$ 2,931

Leases - Summary of Maturities

Leases - Summary of Maturities of Operating Lease Liabilities (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Jan. 01, 2019
Leases [Abstract]
2019 (Nine months ended)	$ 5,749
2020	9,690
2021	12,671
2022	13,087
2023	13,515
2024	13,956
2025 and thereafter	78,233
Total lease payments	146,901
Less: portion representing interest	(44,681)
Less: lease incentives	(5,547)
Operating lease liabilities	96,673	$ 96,200
Less: current portion	(1,649)
Operating lease liabilities, less current portion	$ 95,024

Liability Related to Sale of _2

Liability Related to Sale of Future Royalties - Additional Information (Detail) - USD ($) $ in Thousands	Feb. 24, 2012	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2017
Liability Related to Sale of Future Royalties [Line Items]
Non-cash royalty revenue related to sale of future royalties		$ 8,230		$ 6,920
Non-cash interest expense on liability related to sale of future royalties		$ 6,065		$ 5,019
Annual interest rate			18.70%		17.60%	17.00%
Prospective interest rate			29.00%		21.00%
Purchase and Sale Agreement with RPI [Member]
Liability Related to Sale of Future Royalties [Line Items]
Proceeds from sale of royalty rights	$ 124,000
Transaction costs related to sale of potential future royalties	$ 4,400

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($)	Mar. 31, 2019	Dec. 31, 2018
Indemnification Obligation [Member]
Loss Contingencies [Line Items]
Litigation matters, liabilities	$ 0	$ 0

License and Collaboration Agr_3

License and Collaboration Agreements - License, Collaboration and Other Revenue (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	$ 4,204	$ 13,727
Baxalta Incorporated/Takeda [Member] | ADYNOVATE [Member]
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	20	10,011
Eli Lilly and Company [Member] | NKTR-358 [Member]
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	2,500	2,354
Amgen, Inc. [Member] | Neulasta [Member]
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	1,250	1,250
Other [Member]
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	$ 434	$ 112

License and Collaboration Agr_4

License and Collaboration Agreements - Additional Information (Detail) - USD ($)

Feb. 13, 2018

Aug. 23, 2017

Dec. 31, 2018

Apr. 30, 2018

Mar. 31, 2018

Jan. 31, 2018

Nov. 30, 2017

Sep. 30, 2017

Sep. 30, 2016

Mar. 31, 2016

Mar. 31, 2019

Mar. 31, 2018

Sep. 30, 2017

Dec. 31, 2010

Sep. 30, 2017

Dec. 31, 2018

Dec. 31, 2015

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Revenue recognized in period related to performance in prior periods

$ 19,600,000

$ 28,000,000

Deferred revenue, current portion

$ 13,892,000

11,092,000

$ 13,892,000

Deferred revenue, less current portion

10,744,000

9,340,000

10,744,000

Potential future additional development and regulatory milestones

1,700,000,000

Accounts receivable

43,213,000

42,894,000

43,213,000

Revenue recognized from contracts with customers

28,222,000

38,018,000

Deferred revenue

24,636,000

20,432,000

24,636,000

NKTR-358 [Member] | Nektar's [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Deferred revenue

$ 5,800,000

BMS Collaboration Agreement [Member] | NKTR-214 [Member] | Nektar's [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Upfront and milestone payments received from license agreements

$ 1,000,000,000

Global commercialization profits and losses sharing percentage

65.00%

Percentage of sharing production costs

65.00%

BMS Collaboration Agreement [Member] | NKTR-214 [Member] | Nektar's [Member] | Maximum [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Maximum total additional cash payments receivable upon achievement of certain development and regulatory milestones

1,400,000,000

Eligible additional cash payments receivable upon achievement of certain sales milestones

$ 350,000,000

BMS Collaboration Agreement [Member] | NKTR-214 [Member] | Nektar's [Member] | Opdivo [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Percentage of sharing development costs

32.50%

BMS Collaboration Agreement [Member] | NKTR-214 [Member] | Nektar's [Member] | Opdivo and Yervoy [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Percentage of sharing development costs

22.00%

NKTR-358 [Member] | Nektar's [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Received upfront and milestone payment

$ 150,000,000

Percentage of sharing in Phase 2 development costs

25.00%

Regulatory milestones payment, description

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.

AstraZeneca-Kirin [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Percentage of upfront payment, market access milestones, royalties and sales milestones

40.00%

Baxalta Incorporated/Takeda [Member] | Hemophilia [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Received under right to sublicense agreement

$ 12,000,000

Baxalta Incorporated/Takeda [Member] | Hemophilia [Member] | Annual Sales Level Milestone [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Revenue recognized from contracts with customers

$ 10,000,000

Baxalta Incorporated/Takeda [Member] | Hemophilia [Member] | European Union [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Upfront and milestone payments received from license agreements

$ 10,000,000

Revenue recognized from contracts with customers

$ 10,000,000

10,000,000

Bristol-Myers Squibb [Member] | Purchase Agreement [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Shares issued

8,284,600

Sale of stock consideration received

$ 850,000,000

Bristol-Myers Squibb [Member] | NKTR-214 [Member] | Research and Development Expense [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Reimbursement of expenses

$ 28,800,000

$ 2,300,000

Bristol-Myers Squibb [Member] | BMS Collaboration Agreement [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Accounts receivable

28,400,000

Bristol-Myers Squibb [Member] | BMS Collaboration Agreement [Member] | Purchase Agreement [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Total consideration received under agreements

1,850,000,000

Estimated fair value of shares

$ 790,200,000

Closing date price of common stock

$ 99.36

Remaining amount allocated to transaction price

$ 1,059,800,000

Potential future development, regulatory and sales milestones

$ 1,800,000,000

Bristol-Myers Squibb [Member] | BMS Collaboration Agreement [Member] | NKTR-214 [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Global commercialization profits and losses sharing percentage

35.00%

Percentage of sharing production costs

35.00%

Amount recognized for granting licenses

$ 1,059,800,000

Bristol-Myers Squibb [Member] | BMS Collaboration Agreement [Member] | NKTR-214 [Member] | Opdivo [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Percentage of sharing development costs

67.50%

Bristol-Myers Squibb [Member] | BMS Collaboration Agreement [Member] | NKTR-214 [Member] | Opdivo and Yervoy [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Percentage of sharing development costs

78.00%

Bristol-Myers Squibb [Member] | Clinical Trial Agreement [Member] | NKTR-214 [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Percentage of out-of-pocket costs to be reimbursed by partner

50.00%

Eli Lilly and Company [Member] | NKTR-358 License [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Amount of transaction price allocated to performance obligation

125,900,000

Eli Lilly and Company [Member] | NKTR-358 [Member] | ASC 606 [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Revenue recognized from contracts with customers

$ 125,900,000

$ 125,900,000

Eli Lilly and Company [Member] | NKTR-358 [Member] | Maximum [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Potential future additional development and regulatory milestones

$ 250,000,000

Eli Lilly and Company [Member] | NKTR-358 [Member] | Nektar's [Member]

Collaborative Arrangements And Noncollaborative 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%

Eli Lilly and Company [Member] | NKTR-358 [Member] | Nektar's [Member] | Maximum [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Percentage of funding phase 3 development costs on an indication by indication basis borne

25.00%

Eli Lilly and Company [Member] | NKTR-358 [Member] | Nektar's [Member] | Minimum [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Percentage of funding phase 3 development costs on an indication by indication basis borne

0.00%

Eli Lilly and Company [Member] | Phase 1 Clinical Development [Member] | NKTR-358 License [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Amount of transaction price allocated to performance obligation

17,600,000

Eli Lilly and Company [Member] | Drug Product Development [Member] | NKTR-358 License [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Amount of transaction price allocated to performance obligation

$ 6,500,000

Eli Lilly [Member] | NKTR-358 [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Percentage of sharing in Phase 2 development costs

75.00%

Amgen, Inc. [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Received upfront and milestone payment

$ 50,000,000

Amgen, Inc. [Member] | ASC 606 [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Deferred revenue

7,900,000

AstraZeneca AB [Member] | MOVANTIK and MOVENTIG [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Received upfront and milestone payment

$ 385,000,000

AstraZeneca AB [Member] | AstraZeneca-Kirin [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Deferred revenue

0

Percentage of upfront payment, market access milestone payments, royalties and sales milestone payments from sublicense agreement retained by our collaboration partner

60.00%

Other [Member]

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Deferred revenue

6,000,000

Potential future additional payments for development milestones

$ 45,500,000

License and Collaboration Agr_5

License and Collaboration Agreements - Changes in Deferred Revenue Balance from Collaboration Agreements (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Deferred revenue, Beginning balance	$ 24,636
Recognition of previously unearned revenue	(4,204)
Deferred revenue, Ending balance	$ 20,432

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	$ 25,385	$ 19,949
Cost of Goods Sold [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	820	1,131
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	16,623	12,094
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	$ 7,942	$ 6,724

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - $ / shares	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock issuances under equity compensation plans	698,000	2,854,816
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted stock options	20,455	209,700
Weighted average grant-date fair value	$ 25.51	$ 68.88
Restricted Stock Units (RSU) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted	132,820	10,000

Net Loss Per Share - Additional

Net Loss Per Share - Additional Information (Detail) - shares shares in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Stock Options and Restricted Stock Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted average antidilutive securities excluded from computation of earnings per share	18.9	20