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Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2019	Mar. 20, 2020	Jun. 30, 2019
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Trading Symbol	NK
Entity Registrant Name	NANTKWEST, INC.
Entity Central Index Key	0001326110
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Non-accelerated Filer
Entity Emerging Growth Company	true
Entity Small Business	true
Entity Ex Transition Period	true
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		98,483,161
Entity Public Float			$ 28.8
Title of 12(b) Security	Common Stock, par value $0.0001 per share
Entity File Number	001-37507
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	43-1979754
Entity Interactive Data Current	Yes
Security Exchange Name	NASDAQ
Entity Address, Address Line One	3530 John Hopkins Court
Entity Address, City or Town	San Diego
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	92121
City Area Code	858
Local Phone Number	633-0300
Document Annual Report	true
Document Transition Report	false
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCE As noted herein, the information called for by Part III is incorporated by reference to specified portions of the Registrant’s definitive proxy statement to be filed in conjunction with the Registrant’s 2020 Annual Meeting of Stockholders, which is expected to be filed not later than 120 days after the Registrant’s fiscal year ended December 31, 2019.

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 15,508	$ 16,821
Prepaid expenses and other current assets (including related parties)	4,105	13,900
Marketable debt securities, available-for-sale	36,144	57,328
Notes receivable, held-to-maturity	0	723
Total current assets	55,757	88,772
Marketable debt securities, noncurrent	1,497	5,701
Property, plant and equipment, net	60,501	76,885
Operating lease right-of-use assets, net (including related parties)	11,729	0
Equity investment	9,253	8,500
Intangible assets, net	0	565
Other assets (including related parties)	4,386	1,527
Total assets	143,123	181,950
Current liabilities:
Accounts payable	1,749	2,793
Accrued expenses	5,343	21,104
Due to related parties	486	1,696
Other current liabilities (including related parties)	3,981	1,667
Total current liabilities	11,559	27,260
Operating lease liability, less current portion (including related parties)	10,885	0
Financing obligation, less current portion	0	5,945
Deferred rent	0	2,739
Total liabilities	22,444	35,944
Commitments and contingencies (Note 8)	0	0
Stockholders’ equity:
Common stock, $0.0001 par value; 500,000,000 shares authorized; 98,460,404 and 79,087,734 issued and outstanding as of December 31, 2019 and December 31, 2018	10	8
Additional paid-in capital	782,965	741,246
Accumulated other comprehensive loss	(105)	(267)
Accumulated deficit	(662,191)	(594,981)
Total stockholders’ equity	120,679	146,006
Total liabilities and stockholders’ equity	$ 143,123	$ 181,950

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2019	Dec. 31, 2018
Statement Of Financial Position [Abstract]
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	500,000,000	500,000,000
Common stock, shares issued	98,460,404	79,087,734
Common stock, shares outstanding	98,460,404	79,087,734

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Revenue	$ 43	$ 47	$ 45
Operating expenses:
Research and development (including amounts with related parties)	49,785	55,718	42,044
Selling, general and administrative (including amounts with related parties)	18,065	42,718	57,121
Total operating expenses	67,850	98,436	99,165
Loss from operations	(67,807)	(98,389)	(99,120)
Other income (expense):
Investment income, net	1,642	1,857	2,665
Interest expense (including amounts with related parties)	(19)	(433)	(618)
Other income, net (including amounts with related parties)	298	236	157
Total other income	1,921	1,660	2,204
Loss before income taxes	(65,886)	(96,729)	(96,916)
Income tax benefit	97	503	493
Net loss	$ (65,789)	$ (96,226)	$ (96,423)
Net loss per share:
Basic and diluted	$ (0.70)	$ (1.22)	$ (1.20)
Weighted-average number of shares during the period:
Basic and diluted	94,210,087	79,132,220	80,583,910

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (65,789)	$ (96,226)	$ (96,423)
Other comprehensive income (loss), net of income taxes:
Net unrealized gains (losses) on available-for-sale securities	158	114	(65)
Reclassification of net realized gains (losses) on available-for-sale securities included in net loss	4	0	(32)
Total other comprehensive income (loss)	162	114	(97)
Comprehensive loss	$ (65,627)	$ (96,112)	$ (96,520)

- Definition

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

+ References + Details

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning Balance at Dec. 31, 2016	$ 293,418	$ 8	$ 680,757	$ (284)	$ (387,063)
Beginning Balance, Shares at Dec. 31, 2016		81,983,937
Stock-based compensation expense	36,997	$ 0	36,997	0	0
Exercise of warrants	61	$ 0	61	0	0
Exercise of warrants, Shares		47,226
Exercise of stock options	1,154	$ 0	1,154	0	0
Exercise of stock options, Shares		614,136
Vesting of restricted stock units (RSUs)	0	$ 0	0	0	0
Vesting of restricted stock units (RSUs), Shares		244,209
Net share settlement for restricted stock unit vesting and option/warrant exercises	(1,039)	$ 0	(1,039)	0	0
Net share settlement for restricted stock unit vesting and option/warrant exercises, Shares		(234,020)
Repurchase of common stock	$ (15,227)	$ 0	0	0	(15,227)
Repurchase of common stock, Shares	(3,633,610)	(3,633,610)
Other comprehensive income (loss)	$ (97)	$ 0	0	(97)	0
Net loss	(96,423)	0	0	0	(96,423)
Ending Balance at Dec. 31, 2017	218,844	$ 8	717,930	(381)	(498,713)
Ending Balance, Shares at Dec. 31, 2017		79,021,878
Stock-based compensation expense	23,382	$ 0	23,382	0	0
Exercise of warrants	57	$ 0	57	0	0
Exercise of warrants, Shares		93,254
Vesting of restricted stock units (RSUs)	0	$ 0	0	0	0
Vesting of restricted stock units (RSUs), Shares		172,330
Net share settlement for restricted stock unit vesting and option/warrant exercises	(123)	$ 0	(123)	0	0
Net share settlement for restricted stock unit vesting and option/warrant exercises, Shares		(61,379)
Repurchase of common stock	$ (228)	$ 0	0	0	(228)
Repurchase of common stock, Shares	(138,349)	(138,349)
Cumulative effect of the adoption of the new standard \| Accounting Standards Update 2014-09	$ 186	$ 0	0	0	186
Other comprehensive income (loss)	114	0	0	114	0
Net loss	(96,226)	0	0	0	(96,226)
Ending Balance at Dec. 31, 2018	$ 146,006	$ 8	741,246	(267)	(594,981)
Ending Balance, Shares at Dec. 31, 2018	79,087,734	79,087,734
Stock-based compensation expense	$ 2,627	$ 0	2,627	0	0
Exercise of warrants	35,151	$ 2	35,149	0	0
Exercise of warrants, Shares		17,589,250
Exercise of stock options	4,070	$ 0	4,070	0	0
Exercise of stock options, Shares		1,986,300
Vesting of restricted stock units (RSUs)	0	$ 0	0	0	0
Vesting of restricted stock units (RSUs), Shares		395,051
Net share settlement for restricted stock unit vesting and option/warrant exercises	(127)	$ 0	(127)	0	0
Net share settlement for restricted stock unit vesting and option/warrant exercises, Shares		(124,345)
Repurchase of common stock	$ (501)	$ 0	0	0	(501)
Repurchase of common stock, Shares	(473,586)	(473,586)
Cumulative effect of the adoption of the new standard \| Accounting Standards Update 2016-02	$ (920)	$ 0	0	0	(920)
Other comprehensive income (loss)	162	0	0	162	0
Net loss	(65,789)	0	0	0	(65,789)
Ending Balance at Dec. 31, 2019	$ 120,679	$ 10	$ 782,965	$ (105)	$ (662,191)
Ending Balance, Shares at Dec. 31, 2019	98,460,404	98,460,404

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating activities:
Net loss	$ (65,789)	$ (96,226)	$ (96,423)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	9,012	9,555	5,566
Stock-based compensation expense	2,627	23,382	36,997
Non-cash lease expense related to operating lease right-of-use assets	2,604	0	0
Amortization of net premiums and discounts on marketable debt securities	0	463	1,597
Non-cash interest items, net	246	291	720
Loss on impairment of assets	869	0	0
Loss on disposal of assets	0	209	64
Deferred income tax benefit	0	(498)	(497)
Gains (losses) on sales of marketable debt securities	4	(3)	(32)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	9,276	(9,818)	156
Operating lease right-of-use assets, net	(800)	0	0
Other assets	(4,063)	(1,151)	458
Accounts payable	41	(1,100)	150
Accrued expenses and other liabilities	(12,020)	12,708	(299)
Due to related parties	(1,093)	(685)	1,562
Operating lease liabilities	(2,276)	0	0
Deferred rent and revenue	0	(508)	1,201
Net cash used in operating activities	(61,362)	(63,381)	(48,780)
Investing activities:
Purchases of property, plant and equipment	(4,182)	(13,102)	(34,815)
Proceeds from sales of property, plant and equipment	0	412	0
Purchases of debt securities, held-to-maturity	0	(723)	0
Purchases of investments in equity securities	(3)	0	(8,500)
Purchases of marketable debt securities, available-for-sale	(86,618)	(94,770)	(111,355)
Sales/maturities of marketable debt securities	112,259	165,284	254,222
Net cash provided by investing activities	21,456	57,101	99,552
Financing activities:
Principal payments of financing/capital lease obligations	0	(477)	(19,932)
Proceeds from exercises of stock options and warrants	39,221	57	1,215
Repurchases of common stock with commissions	(501)	(228)	(15,227)
Net share settlement for restricted stock unit vesting and warrant and option exercises	(127)	(123)	(1,039)
Net cash provided by (used in) financing activities	38,593	(771)	(34,983)
Net (decrease) increase in cash, cash equivalents, and restricted cash	(1,313)	(7,051)	15,789
Cash, cash equivalents and restricted cash, beginning of period	17,000	24,051	8,262
Cash, cash equivalents and restricted cash, end of period	15,687	17,000	24,051
Reconciliation of cash, cash equivalents, and restricted cash at end of period:
Cash and cash equivalents	15,508	16,821	23,872
Restricted cash included in other assets	179	179	179
Cash, cash equivalents and restricted cash, end of period	15,687	17,000	24,051
Supplemental disclosure of cash flow information:
Interest	19	475	668
Income taxes	3	4	3
Supplemental disclosure of non-cash investing and financing activities:
Property and equipment purchases acquired under capital lease	0	0	19,448
Property and equipment purchases included in accounts payable, accrued expenses, and other liabilities	74	4,664	9,500
Conversion of Viracta convertible notes and accrued interest into investment in equity securities of Viracta (Note 4)	751	0	0
Unrealized gains (losses) on marketable debt securities	258	123	(97)
Cashless exercises of stock options and warrants	$ 29	$ 94	$ 16

Description of Business

12 Months Ended

Dec. 31, 2019

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Description of Business

1. Description of Business

Organization

NantKwest, Inc., or NantKwest, was incorporated in Illinois on October 7, 2002 under the name ZelleRx Corporation. On January 22, 2010, the company changed its name to Conkwest, Inc., and on July 10, 2015, the company changed its name to NantKwest, Inc. In March 2014, the company redomesticated from the State of Illinois to the State of Delaware and the Illinois company ceased to exist. We are a pioneering clinical-stage immunotherapy biotechnology company headquartered in San Diego, California with certain operations in Culver City and El Segundo, California and Woburn, Massachusetts. In these notes, the terms “we,” “our,” “the company” and “us” refer to NantKwest.

We are focused on harnessing the power of the innate immune system by using its natural killer cells, or NK cells, to treat cancer and viral infectious diseases. A critical aspect of our strategy is to invest significantly in innovating new therapeutic candidates, based upon our proprietary activated NK, or aNK, cell platform, and conducting clinical testing and scale manufacturing of our most promising biologic product candidates.

We hold the exclusive right to commercialize aNK cells, a commercially viable NK cell line, and a wide range of genetically modified derivatives capable of killing cancer and virally infected cells. We own corresponding United States, or U.S., and foreign composition and methods-of-use patents and applications covering the cells, improvements, methods of expansion and manufacture and use of aNK cells and their improvements as therapeutics to treat a spectrum of clinical conditions.

We also license exclusive commercial rights to a high-affinity CD16 receptor expressing enhancement of our aNK cell platform, covered in a portfolio of U.S. and foreign composition and methods-of-use patents and applications covering both the clinical use as a therapeutic to treat cancers in combination with antibody products, as well as the non-clinical use in laboratory testing of monoclonal antibodies. We have non-exclusively licensed or sub-licensed our high-affinity CD16 bearing aNK cell platform and corresponding intellectual property to numerous pharmaceutical and biotechnology companies for such non-clinical uses.

Liquidity

As of December 31, 2019, the company had an accumulated deficit of approximately $662.2 million. We also had negative cash flow from operations of approximately $61.4 million during the year ended December 31, 2019. The company expects that it will likely need additional capital to further fund development of, and seek regulatory approvals for, our product candidates, and to begin to commercialize any approved products.

We are currently focused primarily on the development of immunotherapeutic treatments for cancers and debilitating viral infections using targeted cancer and viral killing cell lines, and we believe such activities will result in the company’s continued incurrence of significant research and development and other expenses related to those programs. If the clinical trials for any of the company’s product candidates fail or produce unsuccessful results and those product candidates do not gain regulatory approval, or if any of our product candidates, if approved, fail to achieve market acceptance, we may never become profitable. Even if the company achieves profitability in the future, it may not be able to sustain profitability in subsequent periods. We intend to cover our future operating expenses through cash and cash equivalents and marketable debt securities on hand and through a combination of equity offerings, debt financings, government or other third party funding, marketing and distribution arrangements and other collaborations, strategic alliances, and licensing arrangements. Additional financing may not be available to us when needed and, if available, financing may not be obtained on terms favorable to the company or its stockholders.

While we expect our existing cash, and cash equivalents and marketable debt securities, together with the ability to borrow from affiliated entities, will enable us to fund operations and capital expenditure requirements for at least the next 12 months, we may not have sufficient funds to reach commercialization. Failure to obtain adequate financing when needed may require us to delay, reduce, limit, or terminate some or all of our development programs or future commercialization efforts or grant rights to develop and market product candidates that we might otherwise prefer to develop and market ourselves, which could adversely affect our ability to operate as a going concern. If we raise additional funds from the issuance of equity securities, substantial dilution to existing stockholders may result. If we raise additional funds by incurring debt financing, the terms of the debt may involve significant cash payment obligations, as well as covenants and specific financial ratios that may restrict our ability to operate our business.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

Basis of Presentation

The consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America, or U.S. GAAP.

The consolidated financial statements have been prepared assuming the company will continue as a going concern, which contemplates the realization of assets and the satisfaction of liabilities in the normal course of business, and do not include any adjustments to reflect the possible future effects on the recoverability and classification of assets or amounts and classification of liabilities that may result from the outcome of the uncertainty discussed in the Liquidity section of Note 1. We believe our existing cash, cash equivalents, and investments in marketable debt securities, and our ability to borrow from affiliated entities, will be sufficient to fund operations through at least the next 12 months following the issuance date of the financial statements based upon our Chairman and CEO’s intent and ability to support the company’s operations with additional funds, including loans from affiliated entities, as required. We may also seek to sell additional equity, through one or more follow-on public offerings, or in separate financings, or obtain a credit facility. However, we may not be able to secure such financing in a timely manner or on favorable terms. Without additional funds, we may choose to delay or reduce our operating or investment expenditures. Further, because of the risk and uncertainties associated with the commercialization of the company’s product candidates in development, we may need additional funds to meet our needs sooner than planned. To date, the company’s primary sources of capital were its initial public offering and the concurrent private placement of common shares. In addition, during the year ended December 31, 2019, our Chairman and CEO exercised warrants and options resulting in aggregate cash proceeds of $39.2 million.

Principles of Consolidation

The consolidated financial statements include the accounts of NantKwest and its wholly owned subsidiaries. All intercompany amounts have been eliminated.

We apply the variable interest model under Accounting Standards Codification, or ASC Topic 810, Consolidation, to any entity in which we hold an equity investment or to which we have the power to direct the entity's most significant economic activities and the ability to participate in the entity's economics. If the entity is within the scope of the variable interest model and meets the definition of a variable interest entity, or VIE, we consider whether we must consolidate the VIE or provide additional disclosures regarding our involvement with the VIE. If we determine that we are the primary beneficiary of the VIE, we will consolidate the VIE. This analysis is performed at the initial investment in the entity or upon any reconsideration event.

For entities we hold as an equity investment that are not consolidated under the VIE Model, we consider whether our investment constitutes ownership of a majority of the voting interests in the entity and therefore should be considered for consolidation under the voting interest model.

Unconsolidated equity investments in the common stock or in-substance common stock of an entity under which we are able to exercise significant influence, but not control, are accounted for using the equity method. Our ability to exercise significant influence is generally indicated by ownership of 20 to 50 percent interest in the voting securities of the entity.

All other unconsolidated equity investments on which we are not able to exercise significant influence will be subsequently measured at fair value with unrealized holding gains and losses included in other income, net on the consolidated statements of operations. In the instance the equity investment does not have a readily determinable fair value and does not qualify for the practical expedient to estimate fair value in accordance with ASC 820, Fair Value Measurement, or ASC 820, we will apply the measurement alternative under ASC 321, Investments—Equity Securities, or ASC 321, pursuant to which we will measure the investment at its cost less impairment, adjusted for observable price changes in an orderly market for an identical or similar investment of the same issuer.

We own non-marketable equity securities that are accounted for using the measurement alternative under ASC 321 because the preferred stock held by us is not considered in-substance common stock and such preferred stock does not have a readily determinable fair value. All investments are reviewed on a regular basis for possible impairment. If an investment's fair value is determined to be less than its net carrying value, the investment is written down to its fair value. Such an evaluation is judgmental and dependent on specific facts and circumstances. Factors considered in determining whether an impairment indicator is present include: the investees’ earnings performance and clinical trial performance, change in the investees’ industry and geographic area in which it operates, offers to purchase or sell the security for a price less than the cost of the investment, issues that raise concerns about the investee's ability to continue as a going concern, and any other information that we may be aware of related to the investment. Factors considered in determining whether an observable price change has occurred include: the price at which the investee issues equity instruments similar to those of our investment and the rights and preferences of those equity instruments compared to ours.

Use of Estimates

The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make certain 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 revenues and expenses during the reporting period. On an ongoing basis, we evaluate our estimates, including those related to valuation of equity-based awards, deferred income taxes and related valuation allowances, preclinical and clinical trial accruals, impairment assessments, useful lives of long-lived assets, loss contingencies, and fair value measurements. We base our estimates on historical experience and on various other market-specific and relevant assumptions that we believe to be reasonable under the circumstances. Actual results could differ from those estimates.

Risks and Uncertainties

Contingencies

We record accruals for loss contingencies to the extent that we conclude it is probable that a liability has been incurred and the amount of the related loss can be reasonably estimated. We evaluate, on a quarterly basis, developments in legal proceedings and other matters that could cause a change in the potential amount of the liability recorded or of the range of potential losses disclosed. Additionally, we record our rights to insurance recoveries, limited to the extent of incurred or probable losses, as a receivable when such recoveries have been agreed to with our third-party insurers and when receipt is deemed probable. This includes instances when our third-party insurers have agreed to pay, on our behalf, certain legal defense costs and settlement amounts directly to applicable law firms and a settlement fund.

Concentration of Credit Risk and Other Risks and Uncertainties

Financial instruments that potentially subject us to concentrations of risk consist principally of cash and cash equivalents and marketable debt securities.

Our cash and cash equivalents are held by one major financial institution in the U.S. and one in Korea.

Product candidates developed by us will require approvals or clearances from the U.S. Food and Drug Administration, or FDA, or international regulatory agencies prior to commercial sales. There can be no assurance that any of our product candidates will receive any of the required approvals or clearances. If we were to be denied approval or clearance or any such approval or clearance was to be delayed, it would have a material adverse impact on us.

Cash, Cash Equivalents and Marketable Debt Securities

We invest our excess funds in investment grade short- to intermediate-term corporate debt securities, commercial paper, government sponsored securities, and foreign government bonds. We consider all highly liquid investments purchased with original maturities of three months or less to be cash equivalents and all investments purchased with original maturities of greater than three months as marketable debt securities, classified as available-for-sale. Marketable debt securities with remaining maturities of 12 months or less are classified as short-term and marketable debt securities with remaining maturities greater than 12 months are classified as long-term. All marketable debt securities are reported at fair value and any unrealized gains and losses are reported as a component of accumulated other comprehensive income (loss), net of tax, on the consolidated statements of stockholders’ equity, with the exception of unrealized losses believed to be other-than-temporary, which are recorded in investment income, net, on the consolidated statements of operations. Realized gains and losses are included in investment income, net, on the consolidated statements of operations. Realized gains and losses from sale of the securities and the amounts, net of tax, reclassified out of accumulated other comprehensive loss, if any, are determined on a specific identification basis.

We periodically evaluate whether declines in fair values of our investments below their book value are other-than-temporary. This evaluation consists of several qualitative and quantitative factors regarding the severity and duration of the unrealized loss, as well as our ability and intent to hold the investment until a forecasted recovery occurs. Additionally, we assess whether or not we have plans to sell the security or whether or not it is more likely than not we will be required to sell any investment before recovery of its amortized cost basis. Factors considered include quoted market prices, recent financial results and operating trends, implied values from any recent transactions or offers of investee securities, credit quality of debt instrument issuers, other publicly available information that may affect the value of our investments, duration and severity of the decline in value, and our strategy and intentions for holding the investment. There were no other-than-temporary impairments recorded in the years ended December 31, 2019, 2018 and 2017.

We minimize credit risk associated with our cash and cash equivalents by periodically evaluating the credit quality of our primary financial institutions. While we maintain cash deposits in FDIC insured financial institutions in excess of federally insured limits, we do not believe that we are exposed to significant credit risk due to the financial position of the depository institutions in which those deposits are held. We have not experienced any losses on such accounts.

We have funded a certificate of deposit (CD) as a substitute letter of credit for one of our leased properties. This CD is reported as long term restricted cash and is included in other assets on the consolidated balance sheets as the landlord is the beneficiary of the account and we are not able to access the funds during the term of the lease.

Property, Plant and Equipment

Property, plant and equipment is stated at historical cost less accumulated depreciation. Historical cost includes expenditures that are directly attributable to the acquisition of the items. All repairs and maintenance are charged to net loss during the financial period in which they are incurred. Depreciation of property, plant and equipment is calculated using the straight-line method over the estimated useful lives of the assets, as follows:

Buildings		39 years
Software		3 years
Laboratory equipment		5 years
Furniture & fixtures		5 years
IT equipment		3 years
Leasehold improvements		The lesser of the lease term or the life of the asset

Upon disposal or impairment of property, plant and equipment, the cost and related accumulated depreciation is removed from the consolidated financial statements and the net amount, less any proceeds, is included in the consolidated statements of operations.

Intangible Assets

Intangible assets, which consisted of the cost of reacquiring a technology license during 2015, were amortized using the straight-line method over an estimated useful life of 4 years. As of December 31, 2019, our intangible assets were fully amortized.

Patents

Patent costs, including related legal costs, are expensed as incurred and recorded in selling, general and administrative expenses on the consolidated statements of operations.

Impairments

Long-lived assets include property, plant and equipment and intangible assets. We review long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability is measured by comparison of the carrying amount to the future net cash flows that the assets are expected to generate. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the assets exceeds the projected undiscounted future cash flows arising from the assets using a discount rate determined by management to be commensurate with the risk inherent to our current business model.

During the second quarter of 2019, we determined that certain bioreactor laboratory equipment could no longer be utilized in the production process. As a result, we recorded an impairment charge totaling $0.9 million, which is included in research and development expense on the consolidated statements of operations. There were no impairment losses recognized during the years ended December 31, 2018 and 2017.

Fair Value of Financial Instruments

The accounting standard for fair value measurements provides a framework for measuring fair value and requires disclosures regarding fair value measurements. Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date, based on our principal or, in absence of a principal, most advantageous market for the specific asset or liability.

We use a three-tier fair value hierarchy to classify and disclose all assets and liabilities measured at fair value on a recurring basis, as well as assets and liabilities measured at fair value on a non-recurring basis, in periods subsequent to their initial measurement. The hierarchy requires us to use observable inputs when available, and to minimize the use of unobservable inputs, when determining fair value.

The three tiers are defined as follows:

•

Level 1— Observable inputs that reflect quoted market prices (unadjusted) for identical assets or liabilities in active markets at the measurement date. Since valuations are based on quoted prices that are readily and regularly available in an active market, valuation of these products does not entail a significant degree of judgment. Our Level 1 assets consist of bank deposits and money market funds.

•

Level 2— Observable inputs other than quoted prices in active markets that are observable either directly or indirectly in the marketplace for identical or similar assets and liabilities. Our Level 2 assets consist of corporate debt securities including commercial paper, government sponsored securities and corporate bonds, as well as foreign municipal securities.

•

Level 3— Valuations based on inputs that are unobservable and significant to the overall fair value measurement.

During the years ended December 31, 2019, 2018 and 2017, no transfers were made into or out of the Level 1, 2 or 3 categories. We will continue to review the fair value inputs on a quarterly basis.

We utilize a third-party pricing service to assist in obtaining fair value pricing for our investments in marketable debt securities. Inputs are documented in accordance with the fair value disclosure hierarchy.

Preclinical and Clinical Trial Accruals

As part of the process of preparing the financial statements, we are required to estimate expenses resulting from obligations under contracts with vendors, clinical research organizations and consultants. The financial terms of these contracts vary and may result in payment flows that do not match the periods over which materials or services are provided under such contracts.

We estimate clinical trial and research agreement related expenses based on the services performed, pursuant to contracts with research institutions and clinical research organizations and other vendors that conduct clinical trials and research on our behalf. In accruing clinical and research related fees, we estimate the time period over which services will be performed and activity expended in each period. If the actual timing of the performance of services or the level of effort varies from the estimate, we will adjust the accrual accordingly. Payments made under these arrangements in advance of the receipt of the related services are recorded as prepaid expenses until the services are rendered.

Transactions with Related Parties

As outlined in Note 9 – Related Party Agreements, we have various agreements with different related parties. Some are billed and settled in cash monthly. Others are billed quarterly and settled in cash the following month. Monthly accruals are made for all quarterly billing arrangements.

Lease Obligations

We adopted FASB ASC Topic 842, Leases, or ASC 842, effective January 1, 2019. For contracts entered into on or after the effective date, we determine if an arrangement is, or contains, a lease at lease inception. Our assessment is based on: (1) whether the contract involves the use of a distinct identified asset; (2) whether we obtain the right to substantially all of the economic benefit from the use of the asset throughout the period; and (3) whether we have the right to direct the use of the asset. At inception of a lease, we allocate the consideration in the contract to each lease component based on its relative stand-alone price to determine the lease payments. Leases entered into prior to January 1, 2019, which were accounted for under ASC 840, Leases, were not reassessed as we elected the package of practical expedients permitted under the transition guidance within the new standard, which among other things, allowed us to carry forward the historical lease classification. We determine the lease term by assuming the exercise of renewal options that are reasonably assured. The exercise of lease renewal options is at our sole discretion. Several of our leases have renewal options, however, exercise of renewal is only assured for the El Segundo current Good Manufacturing Practices, or cGMP, facility, where we have made significant improvements.

For all leases at the lease commencement date, a right-of-use asset and a lease liability are recognized. The right-of-use asset represents the right to use the leased asset for the lease term. At lease commencement, leases are classified as either finance leases or operating leases. A lease is classified as a finance lease if any one of the following criteria are met: (1) the lease transfers ownership of the underlying asset by the end of the lease term; (2) the lease contains an option to purchase the underlying asset that is reasonably certain to be exercised; (3) the lease term is for a major part of the remaining economic life of the underlying asset; (4) the present value of the sum of the lease payments and any guaranteed residual value that is not already included in the lease payments equals or exceeds substantially all of the fair value of the underlying asset; or (5) the underlying asset is of such a specialized nature that it is expected to have no alternative use to the lessor at the end of the lease term. A lease is classified as an operating lease if it does not meet any one of these criteria.

We do not currently have any leases classified as finance leases. Our operating leases are included in operating lease right-of-use assets, net, other current liabilities, and operating lease liabilities on the consolidated balance sheets. At the commencement date, operating lease right-of-use assets and operating lease liabilities are determined based on the present value of lease payments to be made over the lease term. Operating lease right-of-use assets also include any rent paid prior to the commencement date, less any lease incentives received, and initial direct costs incurred. Lease expense for minimum lease payments is recognized on a straight-line basis over the lease term. We have elected to combine our lease components (e.g., fixed payments including rent, real estate taxes and insurance costs) with non-lease components (e.g., common-area maintenance costs and equipment maintenance costs) and as such, we account for lease and non-lease components as a single component. Lease expense also includes amounts relating to variable lease payments. Variable lease payments include amounts relating to common area maintenance and real estate taxes.

We also elected not to recognize right-of-use assets and lease liabilities for qualifying short-term leases with an initial lease term of 12 months or less at lease inception. Such leases are expensed on a straight-line basis over the lease term.

The depreciable life of operating right-of-use-assets and leasehold improvements is limited by the expected lease term.

Income Taxes

We recognize deferred tax assets and liabilities for the expected future tax consequences of temporary differences between the financial reporting and tax basis of assets and liabilities, as well as for operating loss and tax credit carryforwards. Deferred tax assets and liabilities are measured using the tax rates that are expected to apply to taxable income for the years in which those tax assets and liabilities are expected to be realized or settled. We record valuation allowances to reduce deferred tax assets to the amount we believe is more likely than not to be realized.

We recognize uncertain tax positions when the position will be more likely than not upheld on examination by the taxing authorities based solely upon the technical merits of the positions. We recognize interest and penalties, if any, related to unrecognized income tax uncertainties in income tax expense. We did not have any accrued interest or penalties associated with uncertain tax positions as of December 31, 2019 and 2018.

We are subject to U.S. federal income tax, as well as income tax in Korea, California and other states. The federal returns for tax years 2016 through 2019 remain open to examination; the California returns remain subject to examination for tax years 2015 through 2019. Carryforward attributes that were generated in years where the statute of limitations is closed may still be adjusted upon examination by the Internal Revenue Service or other respective tax authority. All other state jurisdictions remain open to examination. No income tax returns are currently under examination by taxing authorities.

Stock Repurchases

In November 2015, the board of directors approved the 2015 Share Repurchase Program (Note 10) allowing the CEO or CFO, on behalf of the company, to repurchase from time to time, in the open market or in privately negotiated transactions, up to $50.0 million of our outstanding shares of common stock, exclusive of any commissions, markups or expenses. The timing and amounts of any purchases were and will continue to be based on market conditions and other factors, including price, regulatory requirements and other corporate considerations. The 2015 Share Repurchase Program does not require the purchase of any minimum number of shares and may be suspended, modified or discontinued at any time without prior notice. We have financed, and expect to continue to finance, the purchases with existing cash balances. As it is the intent for the repurchased shares to be retired, we have elected to account for the shares repurchased under the constructive retirement method. For shares repurchased in excess of par, we allocate the purchase price in excess of par value to accumulated deficit.

Revenue Recognition

Beginning January 1, 2018, we adopted the provisions of FASB ASC Topic 606, Revenue from Contracts with Customers, or ASC 606. This guidance requires that entities recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. We adopted ASC 606 on January 1, 2018 by recording the cumulative effect of the adoption to accumulated deficit. We applied the new guidance to contracts that were not complete as of January 1, 2018. Implementation of ASC 606 did not have a material impact on our consolidated financial statements.

We derive substantially all of our revenue from non-exclusive license agreements with a limited number of pharmaceutical and biotechnology companies granting them the right to use our cell lines and intellectual property for non-clinical use. These agreements generally include upfront fees and annual research license fees for such use, as well as commercial license fees for sales of the licensee products developed or manufactured using our intellectual property and cell lines.

A performance obligation is a promise in a contract to transfer a distinct good or service to the customer and is the unit of account in ASC 606. A contract’s transaction price is allocated to each distinct performance obligation based on relative standalone selling price and recognized as revenue when, or as, the performance obligation is satisfied.

Under the company’s license agreements with customers, the company typically promises to provide a license to use certain cell lines and related patents, the related know-how, and future research and development data that affect the license. We have concluded that these promises represent one performance obligation due to the highly interrelated nature of the promises. We provide the cell lines and know-how immediately upon entering into the contracts. The research and development data is provided throughout the term of the contract when and if available.

Our license agreement with Intrexon (Note 7) included a nonrefundable upfront payment of $0.4 million, received when we entered into the contract in 2010. In this instance, we determined that under ASC 606 it would be appropriate to recognize the initial milestone payment at a point in time, when we transferred the license. In this case, the intellectual property provided under the contract is functional intellectual property under ASC 606 and was determined to be a distinct performance obligation in the context of the arrangement. Prior to adoption, the upfront payment had been initially recorded as deferred revenue and was being recognized into revenue on a straight-line basis. As a result, upon adoption of ASC 606, we adjusted our accumulated deficit for the effects of recognizing revenue upfront for the initial milestone. The adjustment to accumulated deficit upon adoption was not material.

The license agreements may include nonrefundable upfront payments, event-based milestone payments, sales-based royalty payments, or some combination of these. The event-based milestone payments represent variable consideration and we use the most likely amount method to estimate this variable consideration. Given the high degree of uncertainly around achievement of these milestones, we do not recognize revenue from these milestone payments until the uncertainty associated with these payments is resolved. We currently estimate variable consideration related to milestone payments to be zero and, as such, no revenue has been recognized for milestone payments. We recognize revenue from sales-based royalty payments when or as the sales occur. On a quarterly basis, we re-evaluate our estimate of milestone variable consideration to determine whether any amount should be included in the transaction price and recorded in revenue prospectively.

Upon adoption, we changed our accounting policy from accounting for milestones payments under the milestone method to accounting for variable consideration as discussed above. The change in accounting policy did not change any amounts in the financial statements because of the significant uncertainty surrounding the estimate of variable consideration for milestone payments.

To date, we have generated minimal revenue related to the non-clinical use of our cells lines and intellectual property. We have no products approved for commercial sale and we have not generated any revenue from product sales. If we fail to complete the development of our product candidates in a timely manner or fail to obtain regulatory approval for them, we may never be able to generate substantial future revenue.

Research and Development Costs

Major components of research and development costs include cash compensation and other personnel-related expenses, stock-based compensation, depreciation and amortization expense on research and development property and equipment and intangible assets, costs of preclinical studies, clinical trials and related clinical manufacturing, costs of drug development, costs of materials and supplies, facilities cost, overhead costs, regulatory and compliance costs, and fees paid to consultants and other entities that conduct certain research and development activities on our behalf. Costs incurred in research and development are expensed as incurred.

Included in research and development costs are clinical trial and research expenses based on the services performed pursuant to contracts with research institutions and clinical research organizations and other vendors that conduct clinical trials and research on our behalf. We record accruals for estimated costs under these contracts. When evaluating the adequacy of the accrued liabilities, we analyze the progress of the studies or clinical trials, including the phase or completion of events, invoices received, contracted costs and purchase orders. Significant judgments and estimates are made in determining the accrued balances at the end of any reporting period based on the facts and circumstances known at that time. Although we do not expect the estimates to be materially different from the amounts actually incurred, if the estimates of the status and timing of services performed differs from the actual status and timing of services performed, we may report amounts that are too high or too low in any particular period. Actual results could differ from our estimates.

Stock-Based Compensation

We account for stock-based compensation under the provisions of ASC Topic 718, Compensation—Stock Compensation, or ASC 718, which applies to share-based payments issued to employees and nonemployees in exchange for goods or services. Under ASC 718, the fair value of an equity-classified award is estimated on the grant date without regard to service or performance conditions. The grant date fair values for options and warrants are estimated using the Black-Scholes-Merton option pricing model, and the grant date fair values for restricted stock units, or RSUs, are based upon the closing market price of our common stock on the date of grant.

We use the straight-line method to recognize stock-based compensation expense for our outstanding share awards that do not contain a performance condition. For awards subject to performance-based vesting conditions, we assess the probability of the individual milestones under the award being achieved and stock-based compensation expense is recognized over the service period commencing once management believes the performance criteria is probable of being met. For awards with service or performance conditions, we recognize the effect of forfeitures in compensation cost in the period that the award was forfeited.

Litigation Costs

We expense legal fees as they are incurred.

Comprehensive Income (Loss)

Comprehensive income or loss is defined as the change in equity of a business enterprise during a period from transactions and other events and circumstances from non-owner sources. Comprehensive income or loss is composed of net income (loss) and other comprehensive income (loss). Our other comprehensive income or loss consists of unrealized gains and losses on marketable debt securities classified as available-for-sale, net of income taxes.

Basic and Diluted Net Loss per Share of Common Stock

Basic net loss per share is calculated by dividing the net loss by the weighted-average number of common shares outstanding for the period. Diluted loss per share is computed similarly to basic loss per share except that the denominator is increased to include the number of additional shares that would have been outstanding if the potential common shares had been issued and if the additional common shares were dilutive.

For all periods presented, potentially dilutive securities are excluded from the computation of fully diluted loss per share as their effect is anti-dilutive. The following table details those securities that have been excluded from the computation of potentially dilutive securities:

	As of December 31,
	2019		2018		2017
Outstanding options		4,506,950		6,493,250		5,693,250
Outstanding RSUs		1,139,428		867,911		888,189
Outstanding warrants		—		17,589,250		17,721,088
Total		5,646,378		24,950,411		24,302,527

Amounts in the table above reflect the common stock equivalents of the noted instruments.

Segment and Geographic Information

Operating segments are defined as components of an enterprise (business activity from which it earns revenue and incurs expenses) for which discrete financial information is available and regularly reviewed by the chief operating decision maker in deciding how to allocate resources and in assessing performance. Our chief operating decision maker is the company’s CEO. We view our operations and manage our business as a single operating and reporting segment. As of December 31, 2019 and 2018, the majority of our assets were held in the U.S. For the years ended December 31, 2019, 2018 and 2017, all of our revenue was derived in the U.S.

Recent Accounting Pronouncements

Application of New or Revised Accounting Standards – Adopted

We adopted ASC 842 on January 1, 2019, using the simplified transition approach which allowed us to not recast the comparative periods presented when transitioning to the new lease standard, while including required disclosures under ASC 840 for all periods presented under ASC 840. In addition, we elected the package of practical expedients permitted under the transition guidance, which among other things, allowed us to not reassess (1) whether a contract is or contains a lease, and (2) the classification of existing leases.

The adoption of ASC 842 had a substantial impact on our balance sheet. The most significant impacts were (i) the recognition of $13.5 million of operating lease right-of-use assets, net, and $16.4 million of operating lease liabilities, and (ii) the derecognition of assets and liabilities associated with the build-to-suit leases under ASC 840 (resulting in the derecognition of property, plant and equipment, net, of $6.6 million and net adjustments to related liabilities of $5.7 million). The build-to-suit leases were recorded as normal operating leases under ASC 842. The difference between the excess of build-to-suit related liabilities and assets of $0.9 million was recorded as an increase to our accumulated deficit. The cumulative-effect adjustment had no tax impact due to the valuation allowance against the gross deferred tax asset less reversing deferred tax liabilities. Adoption of this standard had no material impact on our results of operations and cash flows.

In August 2018, the FASB issued ASU 2018‑15, Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract (ASU 2018‑15). This update aligns guidance for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs to develop or obtain internal-use software (and hosting arrangements that include an internal-use software license). Capitalized implementation costs will be amortized over the term of the hosting arrangement and expense related to the capitalized implementation costs will be presented in the same line item in the statements of operations as the fees associated with the service contract. As permitted by the standard, we elected to early adopt ASU 2018‑15 on a prospective basis as of October 1, 2019. The adoption did not have a material effect on our consolidated financial statements.

Application of New or Revised Accounting Standards – Not Yet Adopted

In December 2019, the FASB issued ASU 2019-12, Simplifying the Accounting for Income Taxes. The amendments in this update include removing the exception to the incremental approach for intraperiod tax allocation when there is a loss from continuing operations and income, or a gain, from other items (e.g., discontinued operations or other comprehensive income), and the exception to the general methodology for calculating income taxes in an interim period when a year-to-date loss exceeds the anticipated loss for the year. We are currently evaluating the impact that these amendments will have on our consolidated financial statements and we intend to early adopt these amendments on January 1, 2020. We do not expect that the adoption of these amendments will have a significant impact on our consolidated financial statements.

In June 2016, the FASB issued ASU 2016‑13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. The new guidance supersedes existing U.S. GAAP for measuring and recording of credit losses on financial assets measured at amortized cost by replacing the incurred-loss model with an expected-loss model. Accordingly, these financial assets will be presented at the net amount expected to be collected. This new standard also requires that credit losses related to available-for-sale debt securities be recorded as an allowance through net income rather than reducing the carrying amount under the current, other-than-temporary-impairment model. The new guidance is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019, but may be adopted earlier. With certain exceptions, adjustments are to be applied using a modified-retrospective approach by reflecting adjustments through a cumulative-effect impact on retained earnings as of the beginning of the fiscal year of adoption. In May 2019, the FASB issued ASU 2019-05, Financial Instruments—Credit Losses (Topic 326): Targeted Transition Relief, which provides companies with an option to irrevocably elect the fair value option for certain financial assets previously measured at amortized cost basis upon adoption of Topic 326. We are currently evaluating the impact that this new standard and its related amendments will have on our consolidated financial statements and we intend to adopt the standard on January 1, 2021. However, as the impact is dependent upon the investments held as of the adoption date, it is not possible for us to quantify the impact until the date of adoption.

Other recent authoritative guidance issued by the FASB (including technical corrections to the ASC), the American Institute of Certified Public Accountants, and the Securities and Exchange Commission during the three months ended December 31, 2019 did not, or are not expected to, have a material effect on our consolidated financial statements.

Financial Statement Details

12 Months Ended

Dec. 31, 2019

Financial Statement Details [Abstract]

Financial Statement Details

3. Financial Statement Details

Prepaid expenses and other current assets

As of December 31, 2019 and 2018, prepaid expenses and other current assets were made up of (in thousands):

	As of December 31,
	2019		2018
Prepaid preclinical and clinical trial services - with related party (Note 9)	$	1,021	$	—
Insurance premium financing asset		757		339
Prepaid supplies - with related party (Note 9)		467		532
Prepaid services		440		230
Prepaid rent		392		536
Prepaid insurance		372		343
Prepaid equipment maintenance		251		329
Interest receivable - marketable debt securities		222		473
Prepaid license fees		78		104
Insurance claim receivables		34		10,882
Due from related parties		47		90
Other		24		42
	$	4,105	$	13,900

Property, plant and equipment, net

As of December 31, 2019 and 2018, property, plant and equipment, net, was made up of (in thousands):

	As of December 31,
	2019			2018
Construction in progress	$	—		$	2,480
Leasehold improvements		33,406			4,087
Buildings		22,690			59,356
Equipment		21,434			20,878
Software		1,195			1,264
Furniture & fixtures		383			381
		79,108			88,446
Accumulated depreciation		(18,607	)		(11,561	)
	$	60,501		$	76,885

Depreciation expense related to property, plant and equipment was $8.4 million, $7.3 million and $3.3 million for the years ended December 31, 2019, 2018 and 2017, respectively.

As a result of adoption of ASC 842 (Note 2), we (i) reclassified $32.0 million of assets from buildings to leasehold improvements, and (ii) derecognized $6.6 million of assets associated with build-to-suit leases under ASC 840.

The impact of adoption of ASC 842 on property, plant, and equipment at December 31, 2018 was as follows (in thousands):

	Balance December 31, 2018			Adoption of ASC 842 Increase (Decrease)			Balance January 1, 2019
Leasehold improvements	$	4,087		$	32,014		$	36,101
Buildings		59,356			(39,893	)		19,463
Property, plant and equipment, gross		88,446			(7,879	)		80,567
Accumulated depreciation		(11,561	)		1,293			(10,268	)
Property, plant and equipment, net	$	76,885		$	(6,586	)	$	70,299

Intangible assets, net

As of December 31, 2019 and 2018, intangible assets were made up of (in thousands):

	As of December 31,
	2019			2018
Technology license	$	9,042		$	9,042
Less accumulated amortization		(9,042	)		(8,477	)
	$	—		$	565

Our intangible assets were fully amortized as of March 31, 2019. Amortization expense was $0.6 million, $2.3 million and $2.3 million for the years ended December 31, 2019, 2018 and 2017, respectively. Amortization for the company’s technology license is included in research and development expense on the consolidated statements of operations.

Other assets

As of December 31, 2019 and 2018, other assets were made up of (in thousands):

	As of December 31,
	2019		2018
Prepaid preclinical and clinical trial services - with related party (Note 9)	$	4,075	$	—
Restricted cash		179		179
Security deposit		113		113
Prepaid rent		—		1,205
Other		19		30
	$	4,386	$	1,527

Restricted cash is comprised of a certificate of deposit that serves as collateral for a letter of credit required by our landlord as a security deposit related to our facility in San Diego, California.

Accrued expenses

As of December 31, 2019 and 2018, accrued expenses were made up of (in thousands):

	As of December 31,
	2019		2018
Accrued bonus	$	2,002	$	2,079
Accrued compensation		1,064		943
Accrued professional and service fees		975		912
Accrued laboratory equipment and supplies		640		678
Accrued preclinical and clinical trial costs		281		704
Accrued franchise, sales/use and property taxes		200		250
Litigation settlement accruals		—		12,000
Accrued construction costs		—		3,341
Other		181		197
	$	5,343	$	21,104

Other current liabilities

As of December 31, 2019 and 2018, other current liabilities were made up of (in thousands):

	As of December 31,
	2019		2018
Operating lease liability - current portion (including amounts with related parties, Note 9)	$	3,206	$	—
Financing obligation - current portion		757		965
Deferred rent - current portion		—		598
Other		18		104
	$	3,981	$	1,667

Investment income, net

Net investment income is as follows for the years ended December 31, 2019, 2018 and 2017 (in thousands):

	For the Year Ended December 31,
	2019			2018			2017
Interest income	$	1,643		$	2,317		$	4,225
Investment accretion income (amortization expense), net		3			(463	)		(1,597	)
Net realized (losses) gains on investments		(4	)		3			37
	$	1,642		$	1,857		$	2,665

Interest income includes interest from marketable debt securities, notes receivable, other assets, and interest from bank deposits. We did not recognize an impairment loss on any investments during the years ended December 31, 2019, 2018 and 2017.

Viracta Investment and Convertible Notes

12 Months Ended

Dec. 31, 2019

Investments All Other Investments [Abstract]

Viracta Investment and Convertible Notes

4. Viracta Investment and Convertible Notes

In March 2017, we participated in a Series B convertible preferred stock financing and invested $8.5 million in Viracta Therapeutics, Inc., or Viracta, a clinical stage drug development company. In May 2017, we executed an exclusive worldwide license with Viracta to develop and commercialize Viracta’s proprietary histone deacetylase inhibitor drug candidate for use in combination with natural killer cell therapy and possibly additional therapies. See Note 7 – Collaboration and License Agreements – Royalties and In-licensing Agreements – Viracta License Agreement for further information.

In June 2018, Viracta executed a 2018 Note and Warrant Purchase Agreement with existing and new investors, including us. The initial closing under the Purchase Agreement occurred in June 2018, at which point we purchased a convertible note for $0.4 million, which under certain circumstances was convertible into preferred stock of Viracta, and a warrant to purchase Viracta’s common shares. The convertible note accrued interest at 8% and had a one-year maturity date. In September 2018, a milestone closing under the Purchase Agreement occurred, at which point we purchased an additional convertible note for $0.4 million, which under certain circumstances was convertible into preferred stock of Viracta, and a warrant to purchase Viracta’s common shares. The convertible note accrued interest at 8% and had a one-year maturity date. We classified the convertible notes as held-to-maturity notes receivable on the consolidated balance sheets. Effective January 31, 2019, the notes, together with accrued interest then outstanding, were converted to Series B preferred stock resulting in an increase to our investment in Viracta’s Series B convertible preferred stock of $0.8 million. In May 2019, we exercised warrants to acquire 253,120 shares of Viracta common stock. At December 31, 2019, our investment in Viracta totaled $9.3 million.

Based on the level of equity investment at risk, Viracta is not a VIE and therefore is not consolidated under the VIE Model. In addition, we do not hold a controlling financial interest in Viracta and therefore we do not consolidate Viracta under the voting interest model. As the preferred stock is not considered in-substance common stock, the investment is not within the scope of accounting for the investment under the equity method. As the preferred stock does not have a readily determinable fair value and does not qualify for the practical expedient to estimate fair value in accordance with ASC 820, we have elected to apply the measurement alternative under ASC 321, pursuant to which we measure our investment in Viracta at cost, less impairment, adjusted for observable price changes in an orderly market for an identical or similar investment of the same issuer.

As of December 31, 2019, our qualitative impairment assessment did not indicate there were events or changes in circumstances that may have had a significant adverse effect on the fair value of the investment. We have not recorded any impairments as of December 31, 2019, or on a cumulative basis. Further, we have not identified any downward or upward adjustments due to observable price changes in the investment as of December 31, 2019, or on a cumulative basis. Our investment in Viracta is reflected in equity investment on the consolidated balance sheets.

Financial Instruments Investments in Debt Securities

12 Months Ended

Dec. 31, 2019

Cash Equivalents And Marketable Securities [Abstract]

Financial Instruments Investments in Debt Securities

5. Financial Instruments – Investments in Debt Securities

At December 31, 2019, our investments in debt securities are detailed below (in thousands):

	December 31, 2019
	Weighted- Average Remaining Contractual Life (in years)		Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Current:
Available-for-sale:
Corporate debt securities		0.2	$	32,382	$	10	$	(3	)	$	32,389
Foreign government bonds		0.3		1,007		—		—			1,007
Government sponsored securities		0.5		2,752		—		(4	)		2,748
Current portion		0.2		36,141		10		(7	)		36,144
Noncurrent:
Available-for-sale:
Corporate debt securities		1.7		1,501		—		(4	)		1,497
Noncurrent portion		1.7		1,501		—		(4	)		1,497
Total		0.3	$	37,642	$	10	$	(11	)	$	37,641

At December 31, 2018, our investments in debt securities are detailed below (in thousands):

	December 31, 2018
	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Current:
Available-for-sale:
Corporate debt securities	$	57,463	$	1	$	(136	)	$	57,328
Total available-for-sale		57,463		1		(136	)		57,328
Held-to-maturity, notes receivable (Note 4)	723			—		—			723
Current portion		58,186		1		(136	)		58,051
Noncurrent:
Available-for-sale:
Corporate debt securities		3,067		—		(76	)		2,991
Government sponsored securities		2,756		—		(46	)		2,710
Noncurrent portion		5,823		—		(122	)		5,701
Total	$	64,009	$	1	$	(258	)	$	63,752

Accumulated unrealized losses on debt securities classified as available-for-sale that have been in a continuous loss position for less than 12 months and for more than 12 months at December 31, 2019 and 2018 were as follows (in thousands):

	December 31, 2019
	Less than 12 months					More than 12 months
	Estimated Fair Value		Gross Unrealized Losses			Estimated Fair Value		Gross Unrealized Losses
Corporate debt securities	$	11,021	$	(3	)	$	1,497	$	(4	)
Government sponsored securities		—		—			2,748		(4	)
Total	$	11,021	$	(3	)	$	4,245	$	(8	)

	December 31, 2018
	Less than 12 months					More than 12 months
	Estimated Fair Value		Gross Unrealized Losses			Estimated Fair Value		Gross Unrealized Losses
Corporate debt securities	$	32,010	$	(26	)	$	26,663	$	(186	)
Government sponsored securities		—		—			2,710		(46	)
Total	$	32,010	$	(26	)	$	29,373	$	(232	)

At December 31, 2019, 14 of the securities were in an unrealized loss position. We evaluated our securities for other-than-temporary impairment and concluded that the decline in value was primarily caused by current economic and market conditions. We do not intend to sell the investments and it is not more likely than not that we will be required to sell the investments before recovery of their amortized cost bases. Therefore, we did not recognize any other-than-temporary impairment loss during the years ended December 31, 2019, 2018 and 2017.

We recorded realized gains and losses on sales of available-for-sale debt securities as follows (in thousands):

	Gross Realized Gains		Gross Realized Losses			Net Realized Gains (Losses)
2019	$	4	$	(8	)	$	(4	)
2018	$	3	$	—		$	3
2017	$	52	$	(15	)	$	37

Fair Value Measurements

12 Months Ended

Dec. 31, 2019

Fair Value Disclosures [Abstract]

Fair Value Measurements

6. Fair Value Measurements

Fair value is defined as an exit price that would be received from the sale of an asset or paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Authoritative guidance establishes a three-level hierarchy for disclosure that is based on the extent and level of judgment used to estimate the fair value of assets and liabilities.

Recurring Valuations

Financial assets and liabilities measured at fair value on a recurring basis are summarized below at December 31, 2019 and 2018 (in thousands):

	Fair Value Measurements at December 31, 2019
	Total		Level 1		Level 2		Level 3
Assets:
Current:
Cash and cash equivalents	$	15,508	$	15,508	$	—	$	—
Corporate debt securities		32,389		—		32,389		—
Foreign government bonds		1,007		—		1,007		—
Government sponsored securities		2,748		—		2,748		—
Noncurrent:
Corporate debt securities		1,497		—		1,497		—
Total assets measured at fair value	$	53,149	$	15,508	$	37,641	$	—

	Fair Value Measurements at December 31, 2018
	Total		Level 1		Level 2		Level 3
Assets:
Current:
Cash and cash equivalents	$	16,821	$	16,821	$	—	$	—
Corporate debt securities		57,328		—		57,328		—
Noncurrent:
Corporate debt securities		2,991		—		2,991		—
Government sponsored securities		2,710		—		2,710		—
Total assets measured at fair value	$	79,850	$	16,821	$	63,029	$	—

Non-recurring Valuations

Non-financial assets and liabilities are recognized at fair value subsequent to initial recognition when they are deemed to be other-than-temporarily impaired. There were no material non-financial assets and liabilities deemed to be other-than-temporarily impaired and measured at fair value on a non-recurring basis for the years ended December 31, 2019, 2018 and 2017.

Collaboration and License Agreements

12 Months Ended

Dec. 31, 2019

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Collaboration and License Agreements

7. Collaboration and License Agreements

Collaborative Arrangements

A collaborative arrangement is a contractual arrangement that involves a joint operating activity. These arrangements involve two or more parties who are (i) active participants in the activity, and (ii) exposed to significant risks and rewards dependent on the commercial success of the activity.

In January 2020, we entered into a Cost Sharing Agreement with ImmunityBio as further described in Note 15 – Subsequent Events.

Exclusive Co-Development Agreement

In August 2016, we entered into an exclusive Co-Development Agreement, or the Co-Development Agreement, with Altor BioScience, LLC, or Altor. Altor is a related party, as it is a wholly owned subsidiary of ImmunityBio (Note 9). Under the Co-Development Agreement, the parties agreed to exclusively collaborate on the development of certain therapeutic applications combining our proprietary NK cells with Altor's N‑801 and/or N‑803 products with respect to certain technologies and intellectual property rights as may be agreed between the parties for the purpose of jointly developing therapeutic applications of certain effector cell lines.

We are the lead developer for each product developed by the parties pursuant to the Co-Development Agreement unless otherwise agreed to under a given project plan. Under the terms of the Co-Development Agreement, both parties granted a co-exclusive, royalty free, fully paid-up, worldwide license, with the right to sublicense (only to a third-party contractor assisting with research and development activities under this Co-Development Agreement and subject to prior consent, not to be unreasonably withheld), under the intellectual property, or IP, including the parties interest in the joint IP, solely to conduct any development activities agreed to by the steering committee as set forth in any development plan. Unless otherwise mutually agreed by the parties in the development plan for a project, we are responsible for all costs and expenses incurred by either party related to conducting clinical trials and other activities under each development program, including costs associated with patient enrollment, materials and supplies, third-party staffing and regulatory filings. Altor supplies free of charge, sufficient amounts of Altor products for all pre-clinical requirements and certain clinical requirements for up to 400 patients in phase I and/or phase II clinical trials, as required under the development plan for a project per the Co-Development Agreement.

Each company owns an undivided interest in and to all rights, title and interest in and to the joint product rights. The Co-Development Agreement expires upon the fifth anniversary of the effective date. We have dosed patients with N‑803, an IL‑15 superagonist, in several phase Ib/II trials during the years ended December 31, 2019, 2018 and 2017. No charges for supplies by Altor were incurred in association with the above trials during the years ended December 31, 2019, 2018 and 2017.

Royalties and In-licensing Agreements

Viracta License Agreement

In May 2017, we entered into an agreement with Viracta under which we were granted exclusive worldwide rights to Viracta’s phase II drug candidate, VRx‑3996, for use in combination with our platform of NK cell therapies. In consideration for the license, we are obligated to pay to Viracta (i) mid-single digit percentage royalties of net sales of licensed products for therapeutic use; and (ii) milestone payments ranging from $10.0 million to $25.0 million for various regulatory approvals and cumulative net sales levels. We may terminate the agreement, in its sole discretion, in whole or on a product by product and/or country by country basis, at any time upon 90 days’ prior written notice. In addition, either party may terminate the agreement in the event of a material breach or for bankruptcy of the other party.

Chemotherapeutisches Forschungsinstitut Georg-Speyer-Haus, or GSH, and DRK-Blutspendedienst Baden-Wurttenberg-Hessen gGmbH, or BSD, License Agreement

In August 2015, we entered into a license agreement with GSH and BSD under which we were granted an exclusive license to certain GSH‑BSD patents, materials and know-how that specifically targets ErbB2 expressing cancers. In addition, GSH granted us an exclusive license to certain GSH only technology and materials. In consideration for the licenses, we agreed to pay initial and annual licensing fees, regulatory and commercial milestones and low single-digit percentage royalties on net sales of licensed products. We paid $1.1 million for the initial license fees, which was included in research and development expenses on the consolidated statements of operations for the year ended December 31, 2015. Annual license fees under the agreement began in 2018. In October 2018, we terminated this agreement in accordance with the terms of the agreement.

Fox Chase Cancer Center License Agreement

In 2004 and amended in 2008, we entered into an exclusive license agreement with Fox Chase Cancer Center, or Fox Chase, for the exclusive, worldwide right to certain patents and know-how pertaining to CD16 receptor bearing NK‑92 cell lines. In consideration for this exclusive license, we agreed to pay Fox Chase (i) low single-digit percentage royalties on net sales of licensed products for therapeutic and diagnostic use; and (ii) mid-twenties percentage royalties on any compensation we receive from sublicensees.

Rush University Medical Center License Agreement

In 2004, we entered into a 12-year licensing agreement with Rush University Medical Center for the exclusive rights to license and grant sublicenses of certain intellectual property related to clinical use of NK‑92. We are required to pay low to mid-single digit percentage royalties on net sales depending upon the various fields of studies and other factors. We were required to pay a minimum annual royalty of $25,000. The Rush University Medical Center License Agreement also provides for payments in the aggregate amount of $2.5 million upon the company achieving various milestones, including upon (i) the completion of phase II clinical trial associated with the licensed intellectual property; (ii) the approval by the FDA of a new drug application for a licensed product; and (iii) the first year that sales of the licensed product equals or exceeds $0.3 million. The license had a term of 12 years from 2006, the year in which royalty payments were first made, and included customary termination rights for both parties. Beginning in 2018, this license converted to a perpetual, irrevocable, fully paid, royalty-free, exclusive license.

During the years ended December 31, 2019, 2018 and 2017, we recorded royalty expense of $0, $4,200 and $25,000, respectively, related to the Rush University Medical Center License Agreement. Royalty expense is included in selling, general and administrative on the consolidated statements of operations. No milestones were met during the years ended December 31, 2019, 2018 and 2017.

Out-Licensing Agreement

Intrexon License Agreement

In February 2010, we entered into a 17-year license agreement with Intrexon Corporation, or Intrexon, pursuant to which we granted to Intrexon a non-exclusive, worldwide, sublicensable license to research and sell products under certain patents relating to modified NK‑92 cells that express Intrexon’s proprietary gene sequences for use as a therapeutic and prophylactic agent in humans in specified therapeutic areas. In consideration for the license agreement, Intrexon paid us a one-time fee of $0.4 million. Prior to adoption of ASC 606, this upfront payment had initially been recorded as deferred revenue and was being recognized into revenue on a straight-line basis. Upon adoption of ASC 606, we adjusted our accumulated deficit in an amount equal to the then remaining deferred revenue after concluding that under ASC 606 the upfront payment would have been recognized when the license was transferred in 2010. Intrexon will pay the following milestone payments: $0.1 million upon the first IND filing; $0.1 million upon the commencement of the first phase II clinical trial; $0.4 million upon the commencement of the first phase III clinical trial; and $0.5 million upon the first commercial sale relating to the licensed products. Intrexon is obligated to pay us a low single digit percentage royalty based on net sales of the licensed products by Intrexon and a mid-teen percentage royalty based on revenues received by Intrexon in connection with sublicenses of the licensed products. No milestone payments were due or received in the years ended December 31, 2019, 2018 and 2017, and, therefore, we recorded no milestone revenue for any of those years on the consolidated statements of operations.

Commitment and Contingencies

12 Months Ended

Dec. 31, 2019

Commitments And Contingencies Disclosure [Abstract]

Commitments and contingencies

8. Commitments and Contingencies

Contingencies

We record accruals for loss contingencies to the extent that we conclude it is probable that a liability has been incurred and the amount of the related loss can be reasonably estimated. We evaluate, on a quarterly basis, developments in legal proceedings and other matters that could cause a change in the potential amount of the liability recorded or of the range of potential losses disclosed. Additionally, we record our rights to insurance recoveries, limited to the extent of incurred or probable losses, as a receivable when such recoveries have been agreed to with our third-party insurers and when receipt is deemed probable. This includes instances where our third-party insurers have agreed to pay, on our behalf, certain legal defense costs and settlement amounts directly to applicable law firms and a settlement fund.

Securities Litigation

In March 2016, a putative securities class action complaint captioned Sudunagunta v. NantKwest, Inc., et al., No. 16‑cv‑01947 was filed in federal district court for the Central District of California related to the company’s restatement of certain interim financial statements for the periods ended June 30, 2015 and September 30, 2015. A number of similar putative class actions were filed in federal and state court in California. The actions originally filed in state court were removed to federal court, and the various related actions were consolidated. Plaintiffs asserted causes of action for alleged violations of Sections 11 and 15 of the Securities Act of 1933 and Sections 10(b) and 20(a) of the Securities Exchange Act of 1934 and Rule 10b‑5 promulgated thereunder. Plaintiffs sought unspecified damages, costs and attorneys’ fees, and equitable/injunctive or other relief on behalf of putative classes of persons who purchased or acquired the company’s securities during various time periods from July 28, 2015 through March 11, 2016. In September 2017, the court denied defendants' motion to dismiss the third amended consolidated complaint. On August 13, 2018, the district court granted plaintiffs’ motions for class certification and to strike plaintiffs’ claims under the Securities Exchange Act of 1934 and Rule 10b‑5. On August 24, 2018, at the district court’s direction, plaintiffs filed a fourth amended consolidated complaint. On August 27, 2018, defendants petitioned the U.S. Court of Appeals for the Ninth Circuit to authorize interlocutory appeal of the class certification order. On September 7, 2018, defendants answered the fourth amended consolidated complaint. On September 21, 2018, the parties informed the Ninth Circuit that they had reached a settlement in principle, and the parties moved to stay appellate proceedings. On September 24, 2018, the parties notified the district court that they had reached a settlement in principle. On November 9, 2018, the plaintiffs filed an unopposed motion for preliminary approval of the settlement and notice to class members. On January 9, 2019, the district court granted the motion for preliminary approval. A final approval hearing was held on April 29, 2019, and the district court granted final approval and entered judgment on May 31, 2019.

Under the terms of the settlement, we paid $12.0 million to the plaintiffs as full and complete settlement of the litigation. We were responsible for $1.2 million of the settlement amount, which was recognized in selling, general and administrative expense during the third quarter of 2018, while the remaining $10.8 million was fully funded by our insurance carriers under our directors’ and officers’ insurance policy. We and the insurance carriers paid the settlement amount into a settlement fund in January 2019. Subsequent to receiving final approval of the settlement on May 13, 2019, the aforementioned settlement accrual, associated insurance claim receivable and restricted cash were released and are no longer reflected on our consolidated balance sheets as of December 31, 2019.

Stipulation of Settlement

In early April 2019, following board approval, which occurred in late March 2019, we entered into a settlement agreement, or the Stipulation of Settlement, with three stockholders of the company, each of whom had submitted a stockholder demand for the board to take action to remedy purported harm to the company resulting from certain alleged wrongful conduct concerning, among other things, disclosures about Dr. Soon-Shiong’s compensation and a related-party lease agreement. The Stipulation of Settlement called for us to adopt certain governance changes, and for the three stockholders to file a stockholder derivative action in the Superior Court of the State of California, County of San Diego, followed by an application for court approval of the Stipulation of Settlement. On May 31, 2019, the court entered an order preliminarily approving the Stipulation of Settlement and scheduling the final settlement hearing for August 9, 2019. Pursuant to the Stipulation of Settlement, we have provided stockholders with notice of the settlement and the final settlement hearing.

Under the terms of the Stipulation of Settlement, which received final approval by the court on August 9, 2019, we paid an attorney’s fee of $0.5 million to the plaintiffs as part of the settlement. Of that amount, we were responsible for half, which was recognized in selling, general and administrative expense on the consolidated statements of operations during the first quarter of 2019, while the other half was funded by our insurance carrier. We and the insurance carrier paid the settlement amount into a settlement fund in June 2019. Subsequent to receiving final approval of the settlement on August 9, 2019, the aforementioned settlement accrual, associated insurance claim receivable and restricted cash were released and are no longer reflected on our consolidated balance sheets as of December 31, 2019.

Insurance Recoveries

We have reflected our right to insurance recoveries, limited to the extent of incurred or probable losses, as a receivable when such recoveries have been agreed to with our third-party insurers and receipt is deemed probable. This includes instances where our third-party insurers have agreed to pay, on our behalf, certain legal defense costs and settlement amounts directly to applicable law firms and a settlement fund. The amount of such receivable recorded at December 31, 2019 and 2018 was $34,000 and $10.9 million, respectively, and is included in prepaid expenses and other current assets on our consolidated balance sheets.

Contractual Obligations - Leases

We adopted ASC 842, as of January 1, 2019, using the simplified transition approach discussed in further detail in Note 2. As a result, prior periods were not recast. The following disclosures relate to our lease balances as of January 1, 2019 and December 31, 2019, under ASC 842 (in thousands):

	Balance January 1, 2019		Balance December 31, 2019
Operating lease right-of-use assets, net	$	13,532	$	11,729
Other current liabilities	$	2,960	$	3,206
Operating lease liability, less current portion	$	13,407	$	10,885

As a result of new agreements entered into subsequent to our adoption of ASC 842, we recognized an increase of $0.8 million in both operating lease right-of-use assets and operating lease liabilities during the year ended December 31, 2019.

Substantially all of our operating lease right-of-use assets and operating lease liabilities relate to facilities leases. We lease: (i) a research facility and office space in San Diego, California; (ii) a research and manufacturing space in Culver City, California, from a related party; (iii) a research and manufacturing facility in El Segundo, California, also from a related party; (iv) a research facility in Torrance, California, and (v) a research facility in Woburn, Massachusetts. See Note 9 – Related Party Agreements for further information.

Operating lease expense of $5.1 million, including variable lease costs of $1.2 million, was recorded in operating expenses on the consolidated statements of operations for year ended December 31, 2019. The weighted-average remaining lease term as of January 1, 2019 and December 31, 2019 was 5.4 years and 4.5 years, respectively. The weighted-average discount rate as of January 1, 2019 and December 31, 2019 was 9%. For the year ended December 31, 2019, cash outflows from operating leases, excluding variable lease costs, was $4.4 million.

Future minimum lease payments at December 31, 2019 are presented in the following table (in thousands). Common area maintenance costs and taxes are not included in these payments.

Years ending December 31:	Operating Leases (a)
2020	$	4,271
2021		3,753
2022		3,671
2023		2,546
2024		1,083
Thereafter		1,729
Total future minimum lease payments		17,053
Less: Interest		2,962
Present value of operating lease liabilities	$	14,091

(a)

Operating lease payments include $3.3 million related to options to extend lease terms that are reasonably certain of being exercised.

In August 2018, NantBio, Inc., or NantBio, a related party (Note 9) assigned an agreement to us for the use of a third-party research facility, which provides us with the exclusive right to use and access to a portion of the third party’s laboratory and vivarium premises. In conjunction with the assignment, we reimbursed NantBio for upfront payments, which it had made to the third party of $0.9 million, and paid $0.5 million directly to the third party for an aggregate value of $1.4 million. The assigned agreement is for a term of ten years and expires in June 2027. The agreement may be terminated by us at any time, with or without cause. In case of termination of the agreement, the third party will reimburse us for a pro-rata amount based upon the passage of time.

In September 2016, we entered into a lease agreement with 605 Doug St, LLC, a related party (Note 9), for approximately 24,250 square feet in El Segundo, California, which has been converted to a research and development laboratory and a cGMP manufacturing facility. The lease runs from July 2016 through July 2023. We have the option to extend the lease for an additional three year term through July 2026. The monthly rent is $0.1 million with annual increases of 3% beginning in July 2017.

In March 2016, we entered into a lease agreement for an approximately 7,893 square foot facility in Woburn, Massachusetts, for a research and development laboratory, related office and other related uses. The initial lease term runs for 48 months from April 29, 2016 through May 31, 2020. In June 2016, the lease was amended to add 260 square feet, for a total of 8,153 square feet. Base rent for the initial term of the lease is $19,000 per month with a $1 per square foot annual increase on each anniversary date. In August 2019, we exercised our right pursuant to the lease agreement to extend the term of the lease for an additional two years through May 31, 2022. Consequently, we recognized an increase of $0.6 million in both operating lease right-of-use assets and operating lease liabilities on the consolidated balance sheets.

In November 2015, we entered into a facility license agreement with NantWorks LLC, or NantWorks, a related party (Note 9), for approximately 9,500 square feet of office space in Culver City, California, which has been converted to a research and development laboratory and a cGMP manufacturing facility. The license was effective in May 2015 and extends through December 2020. The monthly rent is $47,000, with annual increases of 3% beginning in January 2017.

In June 2015, we entered into a lease agreement for an approximately 44,700 square foot facility in San Diego, California, for a research and development laboratory, related office and other related uses. The term of the lease extends for seven years commencing on August 1, 2016. The base rent is $0.2 million per month with 3% annual increases on each anniversary date.

Prior to adopting ASC 842 on January 1, 2019, we recognized rent expense under operating leases on a straight-line basis. Fixed rent expense under ASC 840 for the years ended December 31, 2018 and 2017 was $2.8 million and $2.7 million, respectively.

Related Party Agreements

12 Months Ended

Dec. 31, 2019

Related Party Agreements

9. Related Party Agreements

Our Chairman and CEO founded and has a controlling interest in NantWorks, which is a collection of multiple companies in the healthcare and technology space. As described below, we have entered into arrangements with NantWorks, and certain affiliates of NantWorks, to facilitate the development of new genetically modified NK cells for our product pipeline.

Share Repurchase

In November 2018, we entered into a share repurchase agreement with an immediate family member of a director of the company, pursuant to which we repurchased 138,349 of our common shares for a total of $0.2 million under our existing share repurchase program.

NantHealth Labs, Inc.

In March 2018, we entered into an agreement with NantHealth Labs, Inc., or NantHealth Labs, to obtain blood-based tumor profiling services. NantHealth Labs is a related party, as it is a wholly owned subsidiary of NantHealth, Inc., a majority owned subsidiary of NantWorks. We are obligated to pay NantHealth Labs fixed, per-patient fees. The agreement has an initial term of five years and renews automatically for successive one-year periods, unless terminated earlier. During the years ended December 31, 2019 and 2018, $10,000 and $0.3 million, respectively, has been recognized in research and development expense on the consolidated statements of operations. At December 31, 2018, we owed NantHealth Labs $49,300, which is included in due to related parties on the consolidated balance sheets. At December 31, 2019, no balances were due between the parties.

Immuno-Oncology Clinic, Inc.

Beginning in 2017, we entered into multiple agreements with Immuno-Oncology Clinic, Inc., or the Clinic, to conduct various clinical trials. The Clinic was formerly known as John Lee, M.D. and Leonard Sender, M.D., Inc., a professional medical corporation, dba Chan Soon-Shiong Institutes for Medicine, in El Segundo, California. The Clinic is a related party as it is owned by one officer of NantKwest and NantWorks manages the administrative operations of the Clinic. Prior to June 30, 2019, one of the company’s officers was an investigator or sub-investigator for all of the company’s trials conducted at the Clinic.

In July 2019, we entered into a new agreement with the Clinic which superseded our existing agreements with the Clinic, effective as of July 1, 2019. The new agreement covers clinical trial and research related activities on a non-exclusive basis relating to our existing clinical trials, commenced prior to July 1, 2019, and prospective clinical trials and research projects. The new agreement also specifies certain services and related costs that are excluded from the new agreement. Prior to commencing any work under the new agreement, the parties have agreed to execute written work orders setting forth the terms and conditions related to specific services to be performed, including financial terms. For existing clinical trials, commenced prior to July 1, 2019, fees incurred for services performed after July 1, 2019 are covered under the new agreement and applied towards the below-mentioned prepayments. The initial term of the new agreement is for one year, but the agreement allows for an automatic renewal and additional extensions beyond the initial term. In July 2019, we executed a clinical trial work order under the new agreement with the Clinic for an open-label, phase I study of PD‑L1.t‑haNK for infusion in subjects with locally advanced or metastatic solid cancers.

In consideration of the services to be performed under the new agreement, we agreed to make payments of $7.5 million to the Clinic, of which $3.75 million and $1.875 million were paid in July 2019 and October 2019, respectively. The prepayments constitute a prepayment by us for services to be performed by the Clinic. Under the term of the new agreement, the outstanding balance of our prepayment shall be increased on a quarterly basis by an interest credit computed in accordance with terms specified in the new agreement.

To the extent any portion of the prepayments remain unearned by the Clinic on the third anniversary of the new agreement, we may elect at our sole discretion either to (i) not extend the term of the new agreement and have the Clinic reimburse us for the total amount of any remaining unused portion of the prepayments, or (ii) extend the term of the new agreement for up to three additional one year periods, at which time the Clinic will reimburse us for the total amount of any remaining unused portion of the prepayments plus interest if reimbursement is not made within 60 days of expiration. The Clinic may terminate this agreement upon each anniversary date upon sixty (60) days prior written notice and reimbursement in full to us of any outstanding unearned balance of the prepayments, provided that any such termination by the Clinic will not apply with respect to any work orders still in effect at the time of such termination.

During the years ended December 31, 2019, 2018 and 2017, expense of $1.1 million, $2.7 million and $0.8 million, respectively, has been recognized in research and development expense on the consolidated statements of operations. At December 31, 2019 and 2018, we owed the Clinic $0.1 million and $0.6 million, respectively, for services excluded from the new agreement, which are included in due to related parties on the consolidated balance sheets, and as of December 31, 2019, we had a prepaid balance with the Clinic of $5.1 million, which is included in prepaid expenses and other currents assets, and other assets, on the consolidated balance sheets. We anticipate that the remaining prepayment amount as of December 31, 2019 will be utilized in future periods as the Clinic provides additional services pursuant to the new agreement.

Tensorcom, LLC

In April 2017, we entered into a sublease agreement with Tensorcom, LLC, or Tensorcom, for a portion of our San Diego, California, research and development laboratory and office space. The lease ran from May 1, 2017 through April 30, 2018. Tensorcom is a related party, as it is an affiliate of NantWorks. The sublease included a portion of the premises consisting of approximately 6,557 rentable square feet of space. The monthly base rent was $25,000 per month. For the years ended December 31, 2018 and 2017, $0.1 million and $0.2 million, respectively, was recognized in other income on the consolidated statements of operations under the sublease agreement. At December 31, 2019 and 2018, there were no balances due between the parties.

605 Doug St, LLC

In September 2016, we entered into a lease agreement with 605 Doug St, LLC, an entity owned by our Chairman and CEO, for approximately 24,250 square feet in El Segundo, California, which has been converted to a research and development laboratory and a cGMP laboratory manufacturing facility. The lease runs from July 2016 through July 2023. We have the option to extend the lease for an additional three-year term through July 2026. The monthly rent is $0.1 million with annual increases of 3% beginning in July 2017. Lease expense for this facility is recorded in research and development expense on the consolidated statements of operations and was $0.9 million, $0.2 million and $0.2 million, respectively, for the years ended December 31, 2019, 2018 and 2017. At December 31, 2019 and 2018, no balances were due between the parties.

NantBio, Inc.

In August 2018, NantBio assigned an agreement to us for the use of a third-party research facility, which provides us with the exclusive right to use and access to a portion of the third party’s laboratory and vivarium premises. NantBio is a related party as it is an affiliate of NantWorks. In conjunction with the assignment, we reimbursed NantBio for upfront payments which it had made to the third party of $0.9 million and paid $0.5 million directly to the third party for an aggregate value of $1.4 million. The assigned agreement is for a term of ten years and expires in June 2027. The agreement may be terminated by us at any time, with or without cause. In case of termination of the agreement, the third party will reimburse us for a pro-rata amount based upon the passage of time.

In January 2018, we entered into a laboratory services agreement with NantBio. The agreement, effective December 2017, included a sublease of approximately 1,965 square feet of laboratory and office space at our San Diego, California, research facility. This sublease was terminated effective December 31, 2019, pursuant to the terms of the agreement. We recognized $0.1 million, $0.1 million and $10,000, respectively, in other income on the consolidated statements of operations for the years ended December 31, 2019, 2018 and 2017. At December 31, 2019 and 2018, NantBio owed us $8,400 and $49,000, respectively, which is included in prepaid expenses and other current assets on the consolidated balance sheets.

In March 2016, NantBio and the National Cancer Institute entered into a cooperative research and development agreement. The initial five-year agreement covers NantBio and its affiliates, including us. Under the agreement, the parties are collaborating on the preclinical and clinical development of proprietary recombinant natural killer cells and monoclonal antibodies in monotherapy and in combination immunotherapies. We benefited from the preclinical and clinical research conducted during the first four years under this agreement. In each of April 2016, April 2017, August 2018, and May 2019, we paid $0.6 million to the National Cancer Institute as a prepayment for services under the agreement. We recognize research and development expense related to this agreement ratably over a 12-month period for each funding year and recorded $0.6 million, of expense associated with the agreement in each of the years ended December 31, 2019, 2018 and 2017. At December 31, 2019 and 2018, we had balances of $0.1 million and $0.1 million, respectively, included in prepaid expenses and other current assets related to this agreement, on the consolidated balance sheets.

NantWorks

In May 2018, we entered into an assignment agreement with NantWorks and a third-party construction firm. In connection with the agreement, we assigned our deposit of $0.4 million with the third-party firm to NantWorks for which NantWorks reimbursed us. This assignment represented unutilized deposits that NantKwest had previously made with the construction company, for which NantWorks can now utilize in applying such funds to future planned construction projects.

Under the NantWorks shared services agreement executed in November 2015, but effective August 2015, NantWorks provides corporate, general and administrative, manufacturing strategy, research and development, regulatory and clinical trial strategy, and other support services. We are charged for the services at cost plus reasonable allocations for indirect costs that relate to the employees providing the services. For the years ended December 31, 2019, 2018 and 2017, we recorded $2.1 million, $2.8 million and $3.6 million, respectively, to selling, general and administrative expense, and $1.5 million, $3.3 million and $3.2 million, respectively, in research and development expense under this arrangement on the consolidated statements of operations. These amounts exclude certain general and administrative expenses provided by third party vendors directly for our benefit, which have been reimbursed to NantWorks based on those vendors’ invoiced amounts without markup by NantWorks.

In June 2016, we amended the existing shared services agreement with NantWorks whereby we can provide support services to NantWorks and/or any of its affiliates. For the years ended December 31, 2019, 2018 and 2017, we recorded expense reimbursements of $1.2 million, $0.6 million and $0.4 million, respectively, to selling, general and administrative expense and $2.3 million, $2.6 million and $1.0 million, respectively, to research and development expense.

At December 31, 2019 and 2018, we owed NantWorks a net amount of $0.4 million and $1.1 million, respectively, for all agreements between the two affiliates, which is included in due to related parties on the consolidated balance sheets.

In November 2015, we entered into a facility license agreement with NantWorks, which became effective May 2015, for approximately 9,500 square feet in Culver City, California, which has been converted to a research and development laboratory and a cGMP manufacturing facility. Lease expense for this facility is recorded in research and development expense on the consolidated statements of operations and was $0.6 million, $0.2 million, and $0.2 million for the years ended December 31, 2019, 2018 and 2017.

NantOmics, LLC

In June 2015, we entered into an agreement, as amended in May 2018, with NantOmics, LLC, or NantOmics, which is a related party, as it is an affiliate of NantWorks. Pursuant to this agreement we obtain genomic sequencing and proteomic analysis services, as well as related data management and bioinformatics services, exclusively from NantOmics. We will have rights to use the data and results generated from NantOmics’ services in connection with the performance of the particular oncology trial with respect to which the services were performed, but NantOmics owns the data and results, as well as any other intellectual property it creates in performing these services on our behalf. We are obligated to pay NantOmics a fixed, per sample fee, determined based on the type of services being provided. The agreement has an initial term of five years and renews automatically for successive one-year periods, unless terminated earlier. For the years ended December 31, 2019, 2018 and 2017, we recorded operating expense of $0.1 million, $0.1 million and $0.1 million, respectively, to research and development under this arrangement on the consolidated statements of operations. At December 31, 2018, we owed NantOmics $24,000, which is included in due to related parties on the consolidated balance sheets. At December 31, 2019, no balances were due between the parties.

ImmunityBio

ImmunityBio, Inc., or ImmunityBio, is a related party, as it is an affiliate of NantWorks. ImmunityBio was formerly known as NantCell, Inc.

In January 2020, we entered into a cost sharing agreement with ImmunityBio as further described in Note 15 ‑ Subsequent Events.

In November 2018, we entered into an agreement with Etubics Corporation, or Etubics, a subsidiary of ImmunityBio. Pursuant to this agreement we sold used laboratory equipment to Etubics for $0.3 million. In conjunction with this sale, we recognized a loss on disposal of related laboratory equipment of $0.1 million, which was included in other income, net on the consolidated statements of operations.

In February 2017, we entered into a research grant agreement with VivaBioCell S.p.A., or VBC, a subsidiary of ImmunityBio. VBC conducted research and development activities related to our NK cell lines using VBC’s proprietary technology. For the years ended December 31, 2018 and 2017, $0.1 million and $0.6 million, respectively, was recognized in research and development expense on the consolidated statements of operations. No expense was incurred for the year ended December 31, 2019.

In August 2016, we entered into an exclusive Co-Development Agreement with Altor as described in Note 7 – Collaboration and License Agreements. Altor is a related party as it is a wholly owned subsidiary of ImmunityBio. No charges for supplies by Altor were incurred in association with the trials during the years ended December 31, 2019, 2018 and 2017.

In June 2015, we also entered into a supply agreement with ImmunityBio pursuant to which we have the right to purchase ImmunityBio’s proprietary bioreactors, made according to specifications mutually agreed to with ImmunityBio. We also have the right to purchase reagents and consumables associated with such equipment from ImmunityBio. When an upfront payment is made, it is included in prepaid expenses on the consolidated balance sheets until the product is received. The agreement has an initial term of five years and renews automatically for successive one-year periods unless terminated earlier.

At December 31, 2019 and 2018, we had $1.8 million and $1.1 million, respectively, in capitalized equipment purchased from ImmunityBio, which is included in property, plant and equipment, net, on the consolidated balance sheets. During the years ended December 31, 2019, 2018 and 2017, we recorded research and development expense associated with reagents and consumables purchased from ImmunityBio of $0.1 million, $0.1 million and $0.3 million, respectively, on the consolidated statements of operations.

At December 31, 2019 and 2018, we had $0.5 million and $0.5 million, respectively, included in prepaid expenses and other current assets on the consolidated balance sheets related to consumables purchased from ImmunityBio. At December 31, 2019 and December 31, 2018, no balances were due between the parties.

Stockholders' Equity

12 Months Ended

Dec. 31, 2019

Equity [Abstract]

Stockholders' Equity

10. Stockholders’ Equity

Stock Repurchase – In November 2015, the board of directors approved a share repurchase program, or the 2015 Share Repurchase Program, allowing the CEO or CFO, on behalf of the company, to repurchase from time to time, in the open market or in privately negotiated transactions, up to $50.0 million of our outstanding shares of common stock, exclusive of any commissions, markups or expenses. The timing and amounts of any purchases were and will continue to be based on market conditions and other factors, including price, regulatory requirements and other corporate considerations. The 2015 Share Repurchase Program does not require the purchase of any minimum number of shares and may be suspended, modified, or discontinued at any time without prior notice. We have financed, and expect to continue to finance, the purchases with existing cash balances. The shares are formally retired through board approval upon repurchase.

To date, we have repurchased 6,403,489 shares of our common stock under the 2015 Share Repurchase Program at a total cost of $31.7 million. In addition, we have paid approximately $0.1 million of broker commissions on repurchases. We repurchased 473,586 shares, 138,349 shares (Note 9), and 3,633,610 shares during the years ended December 31, 2019, 2018 and 2017, respectively, for a total of $0.5 million, $0.2 million, and $15.2 million, respectively. At December 31, 2019, $18.3 million remained authorized for repurchase under the 2015 Share Repurchase Program.

Common Stock Reserved for Future Issuance

We are authorized to issue up to 500,000,000 shares of our common stock, par value $0.0001 per share at December 31, 2019. As of December 31, 2019, there were 98,460,404 shares of our common stock issued and outstanding.

The following table summarizes the common shares reserved for issuance on exercise or vesting of various awards at December 31, 2019:

Outstanding stock options			4,506,950
Outstanding RSUs			1,139,428
Outstanding warrants			—
Total shares reserved for future issuance			5,646,378

Stock-Based Compensation

12 Months Ended

Dec. 31, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation

11. Stock-Based Compensation

2014 Equity Incentive Plan – In March 2014, the company’s board of directors and stockholders approved the 2014 Equity Incentive Plan, or 2014 Plan, under which 11,109,000 shares of Class A common stock were reserved for the granting of incentive stock options, within the meaning of Section 422 of the Internal Revenue Code, or IRC, non-statutory stock options, stock appreciation rights, restricted stock awards, restricted stock units and performance awards to employees, directors and consultants. Recipients of stock awards are eligible to purchase shares of our common stock at an exercise price equal to no less than the estimated fair market value of such stock on the date of grant. The maximum term of awards granted under the 2014 Plan is ten years. Stock awards are generally not exercisable prior to the applicable vesting date, unless otherwise accelerated under the terms of the applicable stock plan agreement. Unvested shares of our common stock issued in connection with an early exercise allowed by the company may be repurchased by us upon termination of the optionee’s service.

2015 Equity Incentive Plan – In July 2015, the company’s board of directors adopted and the company’s stockholders approved the 2015 Equity Incentive Plan, or 2015 Plan. In April 2019, the company’s board of directors adopted, and in June 2019 the company’s stockholders approved, an amendment to the 2015 Plan to reserve a further 3,000,000 shares of common stock for issuance pursuant to the 2015 Plan. The 2015 Plan, as amended, permits the grant of incentive stock options to the company’s employees, and for the grant of non-statutory stock options, restricted stock, restricted stock units, stock appreciation rights, performance units and performance shares to the company’s employees, directors and consultants.

As of December 31, 2019 there were approximately 4.3 million shares of common stock reserved for future grants pursuant to the 2015 Plan. In addition, the shares reserved for future grants under the 2015 Plan include shares subject to stock options or similar awards granted under the 2014 Plan that expire or terminate without having been exercised in full and shares issued pursuant to awards granted under the 2014 Plan that are forfeited to or repurchased by us (provided that the maximum number of shares that may be added to the 2015 Plan pursuant to this provision is approximately 2.3 million shares as of December 31, 2019).

Stock-Based Compensation

The following table presents all stock-based compensation as included on the consolidated statements of operations (in thousands):

	For the Year Ended December 31,
	2019		2018		2017
Stock-based compensation expense:
Warrants for common stock to an officer	$	—	$	17,817	$	31,584
Employee stock options		1,309		4,057		4,267
Employee RSUs		938		1,193		894
Non-employee RSUs		380		315		252
	$	2,627	$	23,382	$	36,997
Stock-based compensation expense in operating expenses:
Research and development	$	499	$	460	$	102
Selling, general and administrative		2,128		22,922		36,895
	$	2,627	$	23,382	$	36,997

Stock Options

The following table summarizes stock option activity under all equity incentive plans for the years ended December 31, 2019, 2018 and 2017:

	Number of Shares			Weighted- Average Exercise Price		Aggregate Intrinsic Value (in thousands)		Weighted- Average Remaining Contractual Life (in years)
Outstanding at December 31, 2016		6,307,386		$	7.14	$	19,100		6.4
Options exercised		(614,136	)	$	1.88
Outstanding at December 31, 2017		5,693,250		$	7.71	$	11,920		5.3
Options granted		800,000		$	3.07
Outstanding at December 31, 2018		6,493,250		$	7.14	$	563		4.8
Options exercised		(1,986,300	)	$	2.06
Outstanding at December 31, 2019		4,506,950		$	9.37	$	5,710		5.8
Vested and Exercisable at December 31, 2019		3,973,614		$	10.22	$	5,326		5.5

The vested and exercisable shares at December 31, 2018 and 2017 were 5,577,531 and 5,114,656, respectively.

The following table provides a summary of options outstanding and vested as of December 31, 2019:

Exercise Prices	Number Outstanding		Weighted- Average Remaining Contractual Life (in years)		Number Exercisable		Weighted- Average Remaining Contractual Life (in years)
$0.42		589,660		4.9		589,660		4.9
$1.76		699,060		5.0		699,060		5.0
$2.00		962,780		5.1		962,780		5.1
$3.07		800,000		8.7		266,664		8.7
$25.00		1,455,450		5.6		1,455,450		5.6
		4,506,950		5.8		3,973,614		5.5

The aggregate intrinsic value of stock options exercised during the years ended December 31, 2019, 2018 and 2017 was $0.2 million, $0.6 million and $1.7 million, respectively. The cash received from exercised options was $4.1 million, $0 and $1.2 million, respectively, for the years ended December 31, 2019, 2018 and 2017.

During the year ended December 31, 2018, the company granted 800,000 stock options to key executives. These options have an exercise price of $3.07 per share, which was equal to the closing price of the company’s common stock on the date of grant, and 25% vest on the one-year anniversary of the date of grant with the remaining options vesting ratably each month over the following three years. No stock options were granted to employees during the years ended December 31, 2019 and 2017. No stock options were granted to non-employees during the years ended December 31, 2019, 2018 and 2017.

The total unrecognized compensation cost related to non-vested stock options as of December 31, 2019 is $1.1 million, which is expected to be recognized over a weighted-average period of 2.7 years.

The company uses a Black-Scholes option-pricing model to determine the fair value of stock-based compensation under ASC Topic 718, Stock Compensation. The assumptions used for employee stock options granted during the year ended December 31, 2018, are presented in the table below:

Expected term (years)		6.0 - 6.1
Risk-free interest rate		2.8%
Expected volatility		75.9%
Dividend yield		0%
Weighted-average measurement date fair value		$2.09

The assumed dividend yield was based on the company’s expectation of not paying dividends in the foreseeable future. The estimated volatility was based on a weighted-average calculation of the company’s common stock together with a peer group of comparable companies whose share prices are publicly available. The risk-free interest rate assumption was based on the U.S. Treasury’s rates for U.S. Treasury zero-coupon bonds with maturities similar to those of the expected term of the award being valued. The weighted-average expected life of options was estimated using the average of the contractual term and the weighted-average vesting term of the options.

Restricted Stock Units

The following table summarizes the restricted stock units, or RSUs, activity under the 2015 Plan:

	Number of RSUs Outstanding			Weighted- Average Grant Date Fair Value
Unvested balance at December 31, 2016		814,456		$	13.98
Granted		615,983		$	4.50
Vested		(244,209	)	$	15.82
Forfeited/canceled		(298,041	)	$	10.28
Unvested balance at December 31, 2017		888,189		$	8.14
Granted		487,472		$	3.57
Vested		(172,330	)	$	6.16
Forfeited/canceled		(335,420	)	$	6.27
Unvested balance at December 31, 2018		867,911		$	6.69
Granted		749,793		$	1.12
Vested		(395,051	)	$	8.83
Forfeited/canceled		(83,225	)	$	7.29
Unvested balance at December 31, 2019		1,139,428		$	2.23

We may grant RSUs to both employees and directors of the company and to employees of related parties that provide shared services to the company under the company’s shared services agreement with NantWorks (Note 9). During the years ended December 31, 2018 and 2017, we granted 90,906 RSUs and 77,250 RSUs, respectively, to non-employees. All of the RSUs granted to non-employees during these periods were granted to employees of related companies under our shared services agreement with NantWorks (Note 9). There were no new grants made to non-employees during the year ended December 31, 2019.

As of December 31, 2019, there was $1.4 million of unrecognized stock-based compensation expense related to RSUs that is expected to be recognized over a weighted-average period of 1.7 years. Of that amount, $1.3 million of unrecognized expense is related to employee grants with a remaining weighted-average period of 1.8 years and $0.1 million of unrecognized expense is related to non-employee grants with a remaining weighted-average period of 0.8 years.

Warrants

The following table summarizes the company’s warrant activity:

Outstanding at December 31, 2016	17,768,314
Warrants exercised	(47,226	)
Outstanding at December 31, 2017	17,721,088
Warrants exercised	(93,254	)
Warrants expired	(38,584	)
Outstanding at December 31, 2018	17,589,250
Warrants exercised	(17,589,250	)
Outstanding at December 31, 2019	—
Vested and exercisable at December 31, 2019	—

During the years ended December 31, 2019, 2018 and 2017, cash proceeds recognized from exercises of warrants were $35.2 million, $0.1 million and $0.1 million, respectively.

Common Stock Reserved for Future Grants under the 2015 Equity Incentive Plan

At December 31, 2019, there were approximately 4.3 million shares of common stock reserved for future grants of equity awards.

Income Taxes

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

Income Taxes

12. Income Taxes

The amount of loss before taxes is as follows (in thousands):

	For the Year Ended December 31,
	2019			2018			2017
U.S. loss before taxes	$	(65,286	)	$	(94,423	)	$	(94,734	)
Foreign loss before taxes		(600	)		(2,306	)		(2,182	)
Loss before income taxes	$	(65,886	)	$	(96,729	)	$	(96,916	)

Income tax benefit for the years ended December 31, 2019, 2018 and 2017 consists of the following (in thousands):

	For the Year Ended December 31,
	2019			2018			2017
Current:
Federal	$	—		$	—		$	—
State		3			3			4
Foreign		—			—			—
Total Current		3			3			4
Deferred:
Federal		(79	)		—			—
State		(21	)		(8	)		—
Foreign		—			(498	)		(497	)
Total Deferred		(100	)		(506	)		(497	)
Income tax benefit	$	(97	)	$	(503	)	$	(493	)

The components that comprise the company’s net deferred tax assets at December 31, 2019 and 2018 consist of the following (in thousands):

	As of December 31,
	2019			2018
Deferred tax assets:
Net operating loss carryforwards	$	78,377		$	61,915
Stock compensation		8,536			79,281
Operating lease liabilities		3,884			—
Depreciation and amortization		2,042			—
Tax credits		898			845
Accrued compensation		775			795
Leases and other accrued liabilities		453			2,909
Accrued legal expenses		—			308
Total deferred tax assets		94,965			146,053
Deferred tax liabilities:
Foreign intangibles		—			(1	)
Operating lease right-of-use assets		(3,233	)		—
Depreciation and amortization		—			(1,279	)
Total deferred tax liabilities		(3,233	)		(1,280	)
Net deferred tax assets		91,732			144,773
Valuation allowance		(91,732	)		(144,773	)
Net deferred tax liability	$	—		$	—

A reconciliation of the federal statutory income tax rate to the company’s effective income tax rate is as follows:

	For the Year Ended December 31,
	2019				2018				2017
Tax computed at federal statutory rate		21.0		%		21.0		%		34.0		%
State income taxes, net of federal tax benefit		(19.4	)			6.2				5.3
Tax rate adjustment		0.1				(0.3	)			4.8
Tax Cuts and Jobs Act		—				—				(53.4	)
Research and development credits		0.2				0.1				0.6
Stock-based compensation		(82.5	)			(0.1	)			(0.3	)
Other		(0.1	)			0.3				0.8
Valuation allowance		80.5				(26.7	)			8.7
Effective income tax rate		(0.2	)	%		0.5		%		0.5		%

On December 22, 2017, the Tax Cuts and Jobs Act, or the TCJA, was enacted into law. The TCJA made significant changes to U.S. tax laws, including, but not limited to, the following: (a) reducing the federal corporate income tax rate from 35% to a flat 21%, effective January 1, 2018; (b) eliminating the federal corporate alternative minimum tax, or AMT, and changing how existing AMT credits can be realized; and (c) eliminating several business deductions and credits, including deductions for certain executive compensation in excess of $1.0 million.

As a result of the rate reduction, the company reduced the deferred tax asset balance as of December 31, 2017 by $51.7 million. Due to the company’s full valuation allowance position, we also reduced the valuation allowance by the same amount.

In December 2017, the Securities and Exchange Commission issued Staff Accounting Bulletin No. 118, or SAB 118, which provides guidance on accounting for the income tax effects of the TCJA. SAB 118 provides a measurement period that should not extend beyond one year from the TCJA enactment date for companies to complete the accounting related to the TCJA under ASC Topic 740, Income Taxes, or ASC 740. In accordance with SAB 118, a company must reflect the income tax effects of those aspects of the TCJA for which the accounting under ASC 740 is complete. To the extent that a company’s accounting for TCJA-related income tax effects is incomplete, but the company is able to determine a reasonable estimate, it must record a provisional estimate in its financial statements. If a company cannot determine a provisional estimate to be included in its financial statements, it should continue to apply ASC 740 on the basis of the provisions of the tax laws that were in effect immediately before enactment of the TCJA. We completed our evaluation of the potential impacts of IRC Section 162(m) as amended by the TJCA on our December 31, 2018 consolidated financial statements, resulting in no adjustment for the years ended December 31, 2019, 2018 and 2017.

Pursuant to IRC Sections 382 and 383, annual use of the company's net operating loss and research and development credit carryforwards may be limited in the event a cumulative change in ownership of more than 50% occurs within a three-year period. We completed an IRC Section 382/383 analysis through March 2019 regarding the limitation of net operating loss and research and development credit carryforwards. As a result, we derecognized a portion of the deferred tax assets for net operating losses and federal and state research and development credits of $0.8 million from our deferred tax asset schedule as of December 31, 2019. There is no impact to tax expense for the derecognition of the net operating losses and federal and state research and development credits due to the valuation allowance recorded against the deferred tax assets. Additionally, we have not recognized the deferred tax asset for research and development credits carryforwards as of December 31, 2019 and 2018 because we are a part of a controlled group of affiliated companies with common ownership and cannot complete our calculation of the credit until the time that all members of the controlled group complete their analysis and calculation of qualified research expenditures. We do not expect that the unrecognized tax benefits will change within 12 months of this reporting date. Due to the existence of the valuation allowance, future changes in our unrecognized tax benefits will not impact the company's effective tax rate.

In assessing the realization of deferred tax assets, management considers whether it is more likely than not that some portion or all of the deferred tax assets will not be realized. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income during the periods in which those temporary differences become deductible. Management considers the scheduled reversal of deferred tax liabilities, projected future taxable income and tax planning strategies in making this assessment. Based on the level of historical operating results and the uncertainty of the economic conditions, we have recorded a full valuation allowance of $91.7 million at December 31, 2019. The change in the valuation allowance for the year ended December 31, 2019 was a decrease of $53.0 million which was mainly driven by the reversal of deferred tax assets related to stock compensation that will not be realized. The portion of the valuation allowance for deferred tax assets for which subsequently recognized tax benefits will be credited directly to contributed capital is $0.2 million.

We have not incurred any material interest or penalties as of the current reporting date with respect to income tax matters. We do not expect that there will be unrecognized tax benefits of a significant nature that will increase or decrease within 12 months of the reporting date. We are subject to U.S. federal income tax, as well as income tax in California and other states. The federal returns for tax years 2016 through 2019 remain open to examination and the California returns remain subject to examination for tax years 2015 through 2019. Carryforward attributes that were generated in years where the statute of limitations is closed may still be adjusted upon examination by the Internal Revenue Service or other respective tax authority. All other state jurisdictions remain open to examination.

At December 31, 2019, the company has federal net operating losses, or NOLs, of approximately $291.8 million, state NOLs of $255.7 million, and foreign NOLs of $0.2 million. The federal NOL carryforwards begin to expire in 2024, the state NOL carryforwards begin to expire in 2030 and the foreign NOL carryforwards begin to expire in 2022. At December 31, 2019, the company also had federal research tax credit carryforwards of approximately $8.5 million and California research tax credits of $5.7 million. The federal research tax credit carryforwards begin to expire in 2034 and the state research tax credit carryforwards begin to expire in 2031.

The following table summarizes the changes to the amount of unrecognized tax benefits (in thousands):

Unrecognized tax benefits at December 31, 2017	$	6,577
Increase for prior year tax positions		798
Increase for current year tax positions		4,608
Unrecognized tax benefits at December 31, 2018		11,983
Decrease for prior year tax positions		(7	)
Increase for current year tax positions		3,680
Unrecognized tax benefits at December 31, 2019	$	15,656

Included in the balance of unrecognized tax benefits at December 31, 2019, is $14.1 million that, if recognized, would not impact our income tax benefit or effective tax rate as long as the deferred tax asset remains subject to a full valuation allowance. We do not expect any significant increases or decreases to our unrecognized tax benefits within the next 12 months.

Summarized Quarterly Data (Unaudited)

12 Months Ended

Dec. 31, 2019

Quarterly Financial Information Disclosure [Abstract]

Summarized Quarterly Data (Unaudited)

13. Summarized Quarterly Data (Unaudited)

The following financial information reflects all normal recurring adjustments that are, in the opinion of management, necessary for a fair statement of the results of the interim periods.

The table below presents unaudited quarterly data for fiscal 2019 and 2018 (in thousands, except for share and per share amounts):

	1st Quarter			2nd Quarter			3rd Quarter			4th Quarter
2019
Revenue	$	5		$	17		$	12		$	9
Operating expenses		18,340			17,313			16,077			16,120
Operating loss		(18,335	)		(17,296	)		(16,065	)		(16,111	)
Net loss		(17,885	)		(16,682	)		(15,581	)		(15,641	)
Net loss per share - basic and diluted	$	(0.22	)	$	(0.17	)	$	(0.16	)	$	(0.16	)
Shares used in calculating net loss per share - basic and diluted		81,261,302			98,594,355			98,331,695			98,419,166

	1st Quarter			2nd Quarter			3rd Quarter			4th Quarter
2018
Revenue	$	5		$	4		$	31		$	7
Operating expenses		28,289			28,282			24,139			17,726
Operating loss		(28,284	)		(28,278	)		(24,108	)		(17,719	)
Net loss		(27,519	)		(27,732	)		(23,635	)		(17,340	)
Net loss per share - basic and diluted	$	(0.35	)	$	(0.35	)	$	(0.30	)	$	(0.22	)
Shares used in calculating net loss per share - basic and diluted		79,036,614			79,107,208			79,204,765			79,177,962

Employee Benefits

12 Months Ended

Dec. 31, 2019

Compensation And Retirement Disclosure [Abstract]

Employee Benefits

14. Employee Benefits

Defined Contribution Benefit Plan – In December 2015, the company adopted a 401(k) retirement and savings plan, or the 401(k) Plan, covering all employees. The 401(k) Plan allows employees to make pre- and post-tax contributions up to the maximum allowable amount set by the Internal Revenue Service. The company, at its discretion, may make certain contributions to the 401(k) Plan. We made contributions of $0.6 million, $0.5 million and $0.4 million during the years ended December 31, 2019, 2018 and 2017, respectively.

Compensated Absences – Under our vacation policy, salaried employees are provided unlimited vacation leave. Therefore, we do not record an accrual for paid leave related to these employees since we are unable to reasonably estimate the compensated absences that these employees will take.

Subsequent Events

12 Months Ended

Dec. 31, 2019

Subsequent Events [Abstract]

Subsequent Events

15. Subsequent Events

Collaborative Arrangement

Cost Allocation Agreement— On January 29, 2020, we entered into a Cost Allocation Agreement, or the Agreement, with ImmunityBio, Inc. and its subsidiaries, or ImmunityBio. The Agreement is effective as of October 1, 2019. ImmunityBio is a related party, as it is an affiliate of NantWorks (Note 9). Simultaneously, we and ImmunityBio entered into Work Order Number One under the Agreement. Under the Agreement and Work Order Number One, the parties agreed to conduct a joint study, the clinical research trial being conducted pursuant to the protocol titled QUILT 3.063: A phase 2 study of combination therapy with an IL-15 superagonist (N‑803), off-the-shelf CD16‑targeted natural killer cells (haNK), and avelumab without cytotoxic chemotherapy in subjects with Merkel Cell Carcinoma (MCC) that has progressed on or after treatment with a checkpoint inhibitor. The ImmunityBio study drug included in the joint study is ImmunityBio’s proprietary IL-15 superagonist known as N‑803 and our study drug is our proprietary “off-the-shelf” CD16-targeted natural killer cell therapy known as haNK.

We will act as the sponsor of this joint study for purposes of regulatory matters, including submissions, correspondence, and communications. Additionally, we are designated as the contracting party to execute agreements with third and related parties relating to the joint study under Work Order Number One. We and ImmunityBio will split certain joint study costs equally related to Work Order Number One, in accordance with the terms of the Agreement. Shared joint study costs include cost related to conducting the joint study development activities, such as personnel related costs, as well as all costs associated to regulatory matters. Costs and expenses incurred in connection with the development, manufacturing, supply, delivery, and pre-patient administration dosing mechanism of each party’s study drug, are excluded from the shared joint study costs. We expect that the joint study cost sharing component under the Agreement related to Work Order Number One will total approximately $2.1 million, subject to change dependent on clinical trial enrollments and progress. At December 31, 2019, there was minimal joint research activity under the Agreement and we incurred approximately $0.1 million in costs related to the joint study that are subject to joint cost sharing under the Agreement and are recorded in research in research and development expense on the consolidated statements of operations.

Under the agreement, each of ImmunityBio and the company will receive exclusive rights to any new intellectual property developed that relates solely to its respective study drug, and the parties will have joint co-equal rights in any other intellectual property. The Agreement expires upon the second anniversary of the effective date with the option to renew for additional successive one-year terms, but work orders for any joint studies still in process at the time of termination will continue until the applicable study is completed.

Coronavirus Pandemic

Due to the global viral outbreak caused by Coronavirus Disease 2019 (COVID‑19) in 2020, there have been resulting effects which could negatively impact our financial condition or operations, including significant stock market exchange volatility, including various temporary volatility trading halts which commenced initially on March 9, 2020 due to market declines, various temporary business closures and event cancellations, and other effects including strains on hospitals and health provider resources which could result in clinical trial disruptions as the broader economic impact of COVID‑19 develops. The ultimate impact of these matters to us and our financial condition and operations is presently unknown. The accompanying consolidated financial statements as of and for the year ended December 31, 2019 do not reflect the effects of these subsequent events.

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Liquidity

Basis of Presentation

The consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America, or U.S. GAAP.

Principles of Consolidation

The consolidated financial statements include the accounts of NantKwest and its wholly owned subsidiaries. All intercompany amounts have been eliminated.

Use of Estimates

Risks and Uncertainties

Contingencies

Concentration of Credit Risk and Other Risks and Uncertainties

Financial instruments that potentially subject us to concentrations of risk consist principally of cash and cash equivalents and marketable debt securities.

Our cash and cash equivalents are held by one major financial institution in the U.S. and one in Korea.

Cash, Cash Equivalents and Marketable Debt Securities

Property, Plant and Equipment

Buildings		39 years
Software		3 years
Laboratory equipment		5 years
Furniture & fixtures		5 years
IT equipment		3 years
Leasehold improvements		The lesser of the lease term or the life of the asset

Intangible Assets

Patents

Patent costs, including related legal costs, are expensed as incurred and recorded in selling, general and administrative expenses on the consolidated statements of operations.

Impairments

Fair Value of Financial Instruments

The three tiers are defined as follows:

•

Level 3— Valuations based on inputs that are unobservable and significant to the overall fair value measurement.

During the years ended December 31, 2019, 2018 and 2017, no transfers were made into or out of the Level 1, 2 or 3 categories. We will continue to review the fair value inputs on a quarterly basis.

Preclinical and Clinical Trial Accruals

Transactions with Related Parties

Lease Obligations

The depreciable life of operating right-of-use-assets and leasehold improvements is limited by the expected lease term.

Income Taxes

Stock Repurchases

Revenue Recognition

Research and Development Costs

Stock-Based Compensation

Litigation Costs

We expense legal fees as they are incurred.

Comprehensive Income (Loss)

Basic and Diluted Net Loss Per Share of Common Stock

Basic and Diluted Net Loss per Share of Common Stock

	As of December 31,
	2019		2018		2017
Outstanding options		4,506,950		6,493,250		5,693,250
Outstanding RSUs		1,139,428		867,911		888,189
Outstanding warrants		—		17,589,250		17,721,088
Total		5,646,378		24,950,411		24,302,527

Amounts in the table above reflect the common stock equivalents of the noted instruments.

Segment and Geographic Information

Recent Accounting Pronouncements

Application of New or Revised Accounting Standards – Adopted

Application of New or Revised Accounting Standards – Not Yet Adopted

Investment in Viracta

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Schedule of Estimated Useful Lives of Property, Plant and Equipment

Depreciation of property, plant and equipment is calculated using the straight-line method over the estimated useful lives of the assets, as follows:

Buildings		39 years
Software		3 years
Laboratory equipment		5 years
Furniture & fixtures		5 years
IT equipment		3 years
Leasehold improvements		The lesser of the lease term or the life of the asset

Securities Excluded from the Computation of Potentially Dilutive Securities

The following table details those securities that have been excluded from the computation of potentially dilutive securities:

	As of December 31,
	2019		2018		2017
Outstanding options		4,506,950		6,493,250		5,693,250
Outstanding RSUs		1,139,428		867,911		888,189
Outstanding warrants		—		17,589,250		17,721,088
Total		5,646,378		24,950,411		24,302,527

Amounts in the table above reflect the common stock equivalents of the noted instruments.

Financial Statement Details (Tables)

12 Months Ended

Dec. 31, 2019

Financial Statement Details [Abstract]

Prepaid Expenses and Other Current Assets

As of December 31, 2019 and 2018, prepaid expenses and other current assets were made up of (in thousands):

	As of December 31,
	2019		2018
Prepaid preclinical and clinical trial services - with related party (Note 9)	$	1,021	$	—
Insurance premium financing asset		757		339
Prepaid supplies - with related party (Note 9)		467		532
Prepaid services		440		230
Prepaid rent		392		536
Prepaid insurance		372		343
Prepaid equipment maintenance		251		329
Interest receivable - marketable debt securities		222		473
Prepaid license fees		78		104
Insurance claim receivables		34		10,882
Due from related parties		47		90
Other		24		42
	$	4,105	$	13,900

Property, Plant and Equipment, Net

As of December 31, 2019 and 2018, property, plant and equipment, net, was made up of (in thousands):

	As of December 31,
	2019			2018
Construction in progress	$	—		$	2,480
Leasehold improvements		33,406			4,087
Buildings		22,690			59,356
Equipment		21,434			20,878
Software		1,195			1,264
Furniture & fixtures		383			381
		79,108			88,446
Accumulated depreciation		(18,607	)		(11,561	)
	$	60,501		$	76,885

Impact of Adoption of ASC 842 on Property, Plant and Equipment

The impact of adoption of ASC 842 on property, plant, and equipment at December 31, 2018 was as follows (in thousands):

	Balance December 31, 2018			Adoption of ASC 842 Increase (Decrease)			Balance January 1, 2019
Leasehold improvements	$	4,087		$	32,014		$	36,101
Buildings		59,356			(39,893	)		19,463
Property, plant and equipment, gross		88,446			(7,879	)		80,567
Accumulated depreciation		(11,561	)		1,293			(10,268	)
Property, plant and equipment, net	$	76,885		$	(6,586	)	$	70,299

Intangible Assets, Net

As of December 31, 2019 and 2018, intangible assets were made up of (in thousands):

	As of December 31,
	2019			2018
Technology license	$	9,042		$	9,042
Less accumulated amortization		(9,042	)		(8,477	)
	$	—		$	565

Other Assets

As of December 31, 2019 and 2018, other assets were made up of (in thousands):

	As of December 31,
	2019		2018
Prepaid preclinical and clinical trial services - with related party (Note 9)	$	4,075	$	—
Restricted cash		179		179
Security deposit		113		113
Prepaid rent		—		1,205
Other		19		30
	$	4,386	$	1,527

Accrued Expenses

As of December 31, 2019 and 2018, accrued expenses were made up of (in thousands):

	As of December 31,
	2019		2018
Accrued bonus	$	2,002	$	2,079
Accrued compensation		1,064		943
Accrued professional and service fees		975		912
Accrued laboratory equipment and supplies		640		678
Accrued preclinical and clinical trial costs		281		704
Accrued franchise, sales/use and property taxes		200		250
Litigation settlement accruals		—		12,000
Accrued construction costs		—		3,341
Other		181		197
	$	5,343	$	21,104

Other Current Liabilities

As of December 31, 2019 and 2018, other current liabilities were made up of (in thousands):

	As of December 31,
	2019		2018
Operating lease liability - current portion (including amounts with related parties, Note 9)	$	3,206	$	—
Financing obligation - current portion		757		965
Deferred rent - current portion		—		598
Other		18		104
	$	3,981	$	1,667

Investment Income, Net

Net investment income is as follows for the years ended December 31, 2019, 2018 and 2017 (in thousands):

	For the Year Ended December 31,
	2019			2018			2017
Interest income	$	1,643		$	2,317		$	4,225
Investment accretion income (amortization expense), net		3			(463	)		(1,597	)
Net realized (losses) gains on investments		(4	)		3			37
	$	1,642		$	1,857		$	2,665

Financial Instruments Investments in Debt Securities (Tables)

12 Months Ended

Dec. 31, 2019

Cash Equivalents And Marketable Securities [Abstract]

Schedule of Investments in Debt Securities

At December 31, 2019, our investments in debt securities are detailed below (in thousands):

	December 31, 2019
	Weighted- Average Remaining Contractual Life (in years)		Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Current:
Available-for-sale:
Corporate debt securities		0.2	$	32,382	$	10	$	(3	)	$	32,389
Foreign government bonds		0.3		1,007		—		—			1,007
Government sponsored securities		0.5		2,752		—		(4	)		2,748
Current portion		0.2		36,141		10		(7	)		36,144
Noncurrent:
Available-for-sale:
Corporate debt securities		1.7		1,501		—		(4	)		1,497
Noncurrent portion		1.7		1,501		—		(4	)		1,497
Total		0.3	$	37,642	$	10	$	(11	)	$	37,641

At December 31, 2018, our investments in debt securities are detailed below (in thousands):

	December 31, 2018
	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Current:
Available-for-sale:
Corporate debt securities	$	57,463	$	1	$	(136	)	$	57,328
Total available-for-sale		57,463		1		(136	)		57,328
Held-to-maturity, notes receivable (Note 4)	723			—		—			723
Current portion		58,186		1		(136	)		58,051
Noncurrent:
Available-for-sale:
Corporate debt securities		3,067		—		(76	)		2,991
Government sponsored securities		2,756		—		(46	)		2,710
Noncurrent portion		5,823		—		(122	)		5,701
Total	$	64,009	$	1	$	(258	)	$	63,752

Accumulated Unrealized Losses on Debt Securities Classified as Available-for-Sale in Continuous Loss Position

	December 31, 2019
	Less than 12 months					More than 12 months
	Estimated Fair Value		Gross Unrealized Losses			Estimated Fair Value		Gross Unrealized Losses
Corporate debt securities	$	11,021	$	(3	)	$	1,497	$	(4	)
Government sponsored securities		—		—			2,748		(4	)
Total	$	11,021	$	(3	)	$	4,245	$	(8	)

	December 31, 2018
	Less than 12 months					More than 12 months
	Estimated Fair Value		Gross Unrealized Losses			Estimated Fair Value		Gross Unrealized Losses
Corporate debt securities	$	32,010	$	(26	)	$	26,663	$	(186	)
Government sponsored securities		—		—			2,710		(46	)
Total	$	32,010	$	(26	)	$	29,373	$	(232	)

Schedule of Realized Gains and Losses on Sales of Available-for-Sale Debt Securities

We recorded realized gains and losses on sales of available-for-sale debt securities as follows (in thousands):

	Gross Realized Gains		Gross Realized Losses			Net Realized Gains (Losses)
2019	$	4	$	(8	)	$	(4	)
2018	$	3	$	—		$	3
2017	$	52	$	(15	)	$	37

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2019

Fair Value Disclosures [Abstract]

Summary of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis

Financial assets and liabilities measured at fair value on a recurring basis are summarized below at December 31, 2019 and 2018 (in thousands):

	Fair Value Measurements at December 31, 2019
	Total		Level 1		Level 2		Level 3
Assets:
Current:
Cash and cash equivalents	$	15,508	$	15,508	$	—	$	—
Corporate debt securities		32,389		—		32,389		—
Foreign government bonds		1,007		—		1,007		—
Government sponsored securities		2,748		—		2,748		—
Noncurrent:
Corporate debt securities		1,497		—		1,497		—
Total assets measured at fair value	$	53,149	$	15,508	$	37,641	$	—

	Fair Value Measurements at December 31, 2018
	Total		Level 1		Level 2		Level 3
Assets:
Current:
Cash and cash equivalents	$	16,821	$	16,821	$	—	$	—
Corporate debt securities		57,328		—		57,328		—
Noncurrent:
Corporate debt securities		2,991		—		2,991		—
Government sponsored securities		2,710		—		2,710		—
Total assets measured at fair value	$	79,850	$	16,821	$	63,029	$	—

Commitment and Contingencies (Tables)

12 Months Ended

Dec. 31, 2019

Commitments And Contingencies Disclosure [Abstract]

Schedule of Lease Balances

The following disclosures relate to our lease balances as of January 1, 2019 and December 31, 2019, under ASC 842 (in thousands):

	Balance January 1, 2019		Balance December 31, 2019
Operating lease right-of-use assets, net	$	13,532	$	11,729
Other current liabilities	$	2,960	$	3,206
Operating lease liability, less current portion	$	13,407	$	10,885

Summary of Future Minimum Lease Payments

Future minimum lease payments at December 31, 2019 are presented in the following table (in thousands). Common area maintenance costs and taxes are not included in these payments.

Years ending December 31:	Operating Leases (a)
2020	$	4,271
2021		3,753
2022		3,671
2023		2,546
2024		1,083
Thereafter		1,729
Total future minimum lease payments		17,053
Less: Interest		2,962
Present value of operating lease liabilities	$	14,091

(a)

Operating lease payments include $3.3 million related to options to extend lease terms that are reasonably certain of being exercised.

Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2018

Equity [Abstract]

Summary Of Common Stock Reserved For Issuance

The following table summarizes the common shares reserved for issuance on exercise or vesting of various awards at December 31, 2019:

Outstanding stock options			4,506,950
Outstanding RSUs			1,139,428
Outstanding warrants			—
Total shares reserved for future issuance			5,646,378

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock Based Compensation Expenses Included on Operations Statement

The following table presents all stock-based compensation as included on the consolidated statements of operations (in thousands):

	For the Year Ended December 31,
	2019		2018		2017
Stock-based compensation expense:
Warrants for common stock to an officer	$	—	$	17,817	$	31,584
Employee stock options		1,309		4,057		4,267
Employee RSUs		938		1,193		894
Non-employee RSUs		380		315		252
	$	2,627	$	23,382	$	36,997
Stock-based compensation expense in operating expenses:
Research and development	$	499	$	460	$	102
Selling, general and administrative		2,128		22,922		36,895
	$	2,627	$	23,382	$	36,997

Summarizes Stock Option Activity Under Equity Intensive Plan

The following table summarizes stock option activity under all equity incentive plans for the years ended December 31, 2019, 2018 and 2017:

	Number of Shares			Weighted- Average Exercise Price		Aggregate Intrinsic Value (in thousands)		Weighted- Average Remaining Contractual Life (in years)
Outstanding at December 31, 2016		6,307,386		$	7.14	$	19,100		6.4
Options exercised		(614,136	)	$	1.88
Outstanding at December 31, 2017		5,693,250		$	7.71	$	11,920		5.3
Options granted		800,000		$	3.07
Outstanding at December 31, 2018		6,493,250		$	7.14	$	563		4.8
Options exercised		(1,986,300	)	$	2.06
Outstanding at December 31, 2019		4,506,950		$	9.37	$	5,710		5.8
Vested and Exercisable at December 31, 2019		3,973,614		$	10.22	$	5,326		5.5

Summary of Options Outstanding and Vested

The following table provides a summary of options outstanding and vested as of December 31, 2019:

Exercise Prices	Number Outstanding		Weighted- Average Remaining Contractual Life (in years)		Number Exercisable		Weighted- Average Remaining Contractual Life (in years)
$0.42		589,660		4.9		589,660		4.9
$1.76		699,060		5.0		699,060		5.0
$2.00		962,780		5.1		962,780		5.1
$3.07		800,000		8.7		266,664		8.7
$25.00		1,455,450		5.6		1,455,450		5.6
		4,506,950		5.8		3,973,614		5.5

Weighted Average of Fair Value of Options Under Black-Scholes Option-Pricing Model

Expected term (years)		6.0 - 6.1
Risk-free interest rate		2.8%
Expected volatility		75.9%
Dividend yield		0%
Weighted-average measurement date fair value		$2.09

Restricted Stock Units (RSUs) Activity

The following table summarizes the restricted stock units, or RSUs, activity under the 2015 Plan:

	Number of RSUs Outstanding			Weighted- Average Grant Date Fair Value
Unvested balance at December 31, 2016		814,456		$	13.98
Granted		615,983		$	4.50
Vested		(244,209	)	$	15.82
Forfeited/canceled		(298,041	)	$	10.28
Unvested balance at December 31, 2017		888,189		$	8.14
Granted		487,472		$	3.57
Vested		(172,330	)	$	6.16
Forfeited/canceled		(335,420	)	$	6.27
Unvested balance at December 31, 2018		867,911		$	6.69
Granted		749,793		$	1.12
Vested		(395,051	)	$	8.83
Forfeited/canceled		(83,225	)	$	7.29
Unvested balance at December 31, 2019		1,139,428		$	2.23

Summary of Warrant Activity

The following table summarizes the company’s warrant activity:

Outstanding at December 31, 2016	17,768,314
Warrants exercised	(47,226	)
Outstanding at December 31, 2017	17,721,088
Warrants exercised	(93,254	)
Warrants expired	(38,584	)
Outstanding at December 31, 2018	17,589,250
Warrants exercised	(17,589,250	)
Outstanding at December 31, 2019	—
Vested and exercisable at December 31, 2019	—

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

Summary of Loss Before Taxes

The amount of loss before taxes is as follows (in thousands):

	For the Year Ended December 31,
	2019			2018			2017
U.S. loss before taxes	$	(65,286	)	$	(94,423	)	$	(94,734	)
Foreign loss before taxes		(600	)		(2,306	)		(2,182	)
Loss before income taxes	$	(65,886	)	$	(96,729	)	$	(96,916	)

Summary of Income Tax Benefit

Income tax benefit for the years ended December 31, 2019, 2018 and 2017 consists of the following (in thousands):

	For the Year Ended December 31,
	2019			2018			2017
Current:
Federal	$	—		$	—		$	—
State		3			3			4
Foreign		—			—			—
Total Current		3			3			4
Deferred:
Federal		(79	)		—			—
State		(21	)		(8	)		—
Foreign		—			(498	)		(497	)
Total Deferred		(100	)		(506	)		(497	)
Income tax benefit	$	(97	)	$	(503	)	$	(493	)

Components of Net Deferred Tax Assets and Liabilities

The components that comprise the company’s net deferred tax assets at December 31, 2019 and 2018 consist of the following (in thousands):

	As of December 31,
	2019			2018
Deferred tax assets:
Net operating loss carryforwards	$	78,377		$	61,915
Stock compensation		8,536			79,281
Operating lease liabilities		3,884			—
Depreciation and amortization		2,042			—
Tax credits		898			845
Accrued compensation		775			795
Leases and other accrued liabilities		453			2,909
Accrued legal expenses		—			308
Total deferred tax assets		94,965			146,053
Deferred tax liabilities:
Foreign intangibles		—			(1	)
Operating lease right-of-use assets		(3,233	)		—
Depreciation and amortization		—			(1,279	)
Total deferred tax liabilities		(3,233	)		(1,280	)
Net deferred tax assets		91,732			144,773
Valuation allowance		(91,732	)		(144,773	)
Net deferred tax liability	$	—		$	—

Reconciliation of Federal Statutory Income Tax Rate

A reconciliation of the federal statutory income tax rate to the company’s effective income tax rate is as follows:

	For the Year Ended December 31,
	2019				2018				2017
Tax computed at federal statutory rate		21.0		%		21.0		%		34.0		%
State income taxes, net of federal tax benefit		(19.4	)			6.2				5.3
Tax rate adjustment		0.1				(0.3	)			4.8
Tax Cuts and Jobs Act		—				—				(53.4	)
Research and development credits		0.2				0.1				0.6
Stock-based compensation		(82.5	)			(0.1	)			(0.3	)
Other		(0.1	)			0.3				0.8
Valuation allowance		80.5				(26.7	)			8.7
Effective income tax rate		(0.2	)	%		0.5		%		0.5		%

Summarizes of Changes in Unrecognized Tax Benefits

The following table summarizes the changes to the amount of unrecognized tax benefits (in thousands):

Unrecognized tax benefits at December 31, 2017	$	6,577
Increase for prior year tax positions		798
Increase for current year tax positions		4,608
Unrecognized tax benefits at December 31, 2018		11,983
Decrease for prior year tax positions		(7	)
Increase for current year tax positions		3,680
Unrecognized tax benefits at December 31, 2019	$	15,656

Summarized Quarterly Data (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2019

Quarterly Financial Information Disclosure [Abstract]

Summary of Quarterly Data (Unaudited)

The table below presents unaudited quarterly data for fiscal 2019 and 2018 (in thousands, except for share and per share amounts):

	1st Quarter			2nd Quarter			3rd Quarter			4th Quarter
2019
Revenue	$	5		$	17		$	12		$	9
Operating expenses		18,340			17,313			16,077			16,120
Operating loss		(18,335	)		(17,296	)		(16,065	)		(16,111	)
Net loss		(17,885	)		(16,682	)		(15,581	)		(15,641	)
Net loss per share - basic and diluted	$	(0.22	)	$	(0.17	)	$	(0.16	)	$	(0.16	)
Shares used in calculating net loss per share - basic and diluted		81,261,302			98,594,355			98,331,695			98,419,166

	1st Quarter			2nd Quarter			3rd Quarter			4th Quarter
2018
Revenue	$	5		$	4		$	31		$	7
Operating expenses		28,289			28,282			24,139			17,726
Operating loss		(28,284	)		(28,278	)		(24,108	)		(17,719	)
Net loss		(27,519	)		(27,732	)		(23,635	)		(17,340	)
Net loss per share - basic and diluted	$	(0.35	)	$	(0.35	)	$	(0.30	)	$	(0.22	)
Shares used in calculating net loss per share - basic and diluted		79,036,614			79,107,208			79,204,765			79,177,962

Description of Business - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Accumulated deficit	$ (662,191)	$ (594,981)
Net cash used in operating activities	$ (61,362)	$ (63,381)	$ (48,780)

Summary of Significant Accounting Policies - Additional Information (Detail)	1 Months Ended	3 Months Ended	12 Months Ended
	Feb. 28, 2010 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($) Product	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jan. 01, 2019 USD ($)	Nov. 30, 2015 USD ($)
Accounting Policies [Line Items]
Proceeds from exercise of stock options and warrants			$ 39,221,000	$ 57,000	$ 1,215,000
Cash and cash equivalents original maturities			3 months
Maximum original maturity period of short-term marketable securities			12 months
Minimum original maturity period of long-term marketable securities			12 months
Other than temporary impairments for marketable securities			$ 0	0	0
Estimated useful lives of intangible assets			4 years
Fair value inputs, transfers into or out of Level 1, 2 or 3 categories			$ 0	0	0
Lease practical expedients package			true
Operating lease, description			elected not to recognize right-of-use assets and lease liabilities for qualifying short-term leases with an initial lease term of 12 months or less at lease inception
Accrued interest or penalties associated with uncertain tax positions			$ 0	0
Total amount authorized for repurchase							$ 50,000,000
Variable consideration related to milestone payment			0
Revenue recognized for milestone payment			$ 0
Number of products approved for commercial sale \| Product			0
Operating lease right-of-use assets			$ 11,729,000	0		$ 13,532,000
Operating lease liabilities			14,091,000
Property, plant and equipment, net			60,501,000	76,885,000
Liabilities			22,444,000	35,944,000
Accounting Standards Update 2016-02
Accounting Policies [Line Items]
Operating lease right-of-use assets						13,500,000
Operating lease liabilities						16,400,000
Property, plant and equipment, net						70,299,000
Accounting Standards Update 2016-02 \| Accumulated Deficit
Accounting Policies [Line Items]
Build-to-suit related liabilities and assets adjust as accumulated deficit						(900,000)
Accounting Standards Update 2016-02 \| Difference between Lease Guidance in Effect before and after Topic 842
Accounting Policies [Line Items]
Property, plant and equipment, net						(6,600,000)
Liabilities						$ (5,700,000)
Intrexon Corporation
Accounting Policies [Line Items]
Nonrefundable upfront payment	$ 400,000
Revenue recognized for milestone payment			$ 0	0	0
Research and Development
Accounting Policies [Line Items]
Impairment charge/losses of long-lived assets		$ 900,000		$ 0	$ 0
Minimum
Accounting Policies [Line Items]
Marketable securities original maturities			3 months
Minimum \| California
Accounting Policies [Line Items]
Tax year open for examination			2015
Minimum \| Federal
Accounting Policies [Line Items]
Tax year open for examination			2016
Maximum \| California
Accounting Policies [Line Items]
Tax year open for examination			2019
Maximum \| Federal
Accounting Policies [Line Items]
Tax year open for examination			2019
VIE \| Minimum
Accounting Policies [Line Items]
Percentage of ownership interest			20.00%
VIE \| Maximum
Accounting Policies [Line Items]
Percentage of ownership interest			50.00%
Chairman and Chief Executive Officer
Accounting Policies [Line Items]
Proceeds from exercise of stock options and warrants			$ 39,200,000

Summary of Significant Accounting Policies - Schedule of Estimated Useful Lives of Property, Plant and Equipment (Detail)	12 Months Ended
	Dec. 31, 2019
Buildings
Property Plant And Equipment [Line Items]
Property and equipment estimated useful lives	39 years
Software
Property Plant And Equipment [Line Items]
Property and equipment estimated useful lives	3 years
Laboratory Equipment
Property Plant And Equipment [Line Items]
Property and equipment estimated useful lives	5 years
Furniture And Fixtures
Property Plant And Equipment [Line Items]
Property and equipment estimated useful lives	5 years
IT Equipment
Property Plant And Equipment [Line Items]
Property and equipment estimated useful lives	3 years
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment estimated useful lives, term	The lesser of the lease term or the life of the asset

Summary of Significant Accounting Policies - Securities Excluded from the Computation of Potentially Dilutive Securities (Detail) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	5,646,378	24,950,411	24,302,527
Employee Stock Option
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	4,506,950	6,493,250	5,693,250
Outstanding RSUs
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	1,139,428	867,911	888,189
Outstanding Warrants
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	0	17,589,250	17,721,088

Financial Statement Details - Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Financial Statement Details [Abstract]
Prepaid preclinical and clinical trial services - with related party (Note 9)	$ 1,021	$ 0
Insurance premium financing asset	757	339
Prepaid supplies - with related party (Note 9)	467	532
Prepaid services	440	230
Prepaid rent	392	536
Prepaid insurance	372	343
Prepaid equipment maintenance	251	329
Interest receivable - marketable debt securities	222	473
Prepaid license fees	78	104
Insurance claim receivables	34	10,882
Due from related parties	47	90
Other	24	42
Total prepaid expenses and other current assets	$ 4,105	$ 13,900

Financial Statement Details - Property, Plant and Equipment, Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	$ 79,108	$ 88,446
Accumulated depreciation	(18,607)	(11,561)
Property, plant and equipment, net	60,501	76,885
Construction in Progress
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	0	2,480
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	33,406	4,087
Buildings
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	22,690	59,356
Equipment
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	21,434	20,878
Software
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	1,195	1,264
Furniture And Fixtures
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	$ 383	$ 381

Financial Statement Details - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Financial Statement Details [Line Items]
Depreciation expense related to property, plant and equipment	$ 8,400,000	$ 7,300,000	$ 3,300,000
Amortization expense	600,000	2,300,000	2,300,000
Impairment loss on recognized investments	0	$ 0	$ 0
Accounting Standards Update 2016-02
Financial Statement Details [Line Items]
Reclassification of assets from buildings to leasehold improvements	32,000,000
Derecognized build-to-suit lease assets	$ 6,600,000

Financial Statement Details - Impact of Adoption of ASC 842 on Property, Plant and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Financial Statement Details [Line Items]
Property, plant and equipment, gross	$ 79,108		$ 88,446
Accumulated depreciation	(18,607)		(11,561)
Property, plant and equipment, net	60,501		76,885
Leasehold Improvements
Financial Statement Details [Line Items]
Property, plant and equipment, gross	33,406		4,087
Buildings
Financial Statement Details [Line Items]
Property, plant and equipment, gross	$ 22,690		$ 59,356
Accounting Standards Update 2016-02
Financial Statement Details [Line Items]
Property, plant and equipment, gross		$ 80,567
Accumulated depreciation		(10,268)
Property, plant and equipment, net		70,299
Accounting Standards Update 2016-02 \| Restatement Adjustment
Financial Statement Details [Line Items]
Property, plant and equipment, gross		(7,879)
Accumulated depreciation		1,293
Property, plant and equipment, net		(6,586)
Accounting Standards Update 2016-02 \| Leasehold Improvements
Financial Statement Details [Line Items]
Property, plant and equipment, gross		36,101
Accounting Standards Update 2016-02 \| Leasehold Improvements \| Restatement Adjustment
Financial Statement Details [Line Items]
Property, plant and equipment, gross		32,014
Accounting Standards Update 2016-02 \| Buildings
Financial Statement Details [Line Items]
Property, plant and equipment, gross		19,463
Accounting Standards Update 2016-02 \| Buildings \| Restatement Adjustment
Financial Statement Details [Line Items]
Property, plant and equipment, gross		$ (39,893)

Financial Statement Details - Intangible Assets, Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Finite Lived Intangible Assets [Line Items]
Intangible assets, net	$ 0	$ 565
Technology License
Finite Lived Intangible Assets [Line Items]
Total intangible assets	9,042	9,042
Less accumulated amortization	(9,042)	(8,477)
Intangible assets, net	$ 0	$ 565

Financial Statement Details - Other Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Financial Statement Details [Abstract]
Prepaid preclinical and clinical trial services - with related party (Note 9)	$ 4,075	$ 0
Restricted cash	179	179	$ 179
Security deposit	113	113
Prepaid rent	0	1,205
Other	19	30
Other Assets Noncurrent	$ 4,386	$ 1,527

Financial Statement Details - Accrued Expenses (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Financial Statement Details [Abstract]
Accrued bonus	$ 2,002	$ 2,079
Accrued compensation	1,064	943
Accrued professional and service fees	975	912
Accrued laboratory equipment and supplies	640	678
Accrued preclinical and clinical trial costs	281	704
Accrued franchise, sales/use and property taxes	200	250
Litigation settlement accruals	0	12,000
Accrued construction costs	0	3,341
Other	181	197
Accrued Liabilities Current	$ 5,343	$ 21,104

Financial Statement Details - Other Current Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Financial Statement Details [Abstract]
Operating lease liability - current portion (including amounts with related parties, Note 9)	$ 3,206	$ 2,960	$ 0
Financing obligation - current portion	757		965
Deferred rent - current portion	0		598
Other	18		104
Other current liabilities	$ 3,981		$ 1,667

Financial Statement Details - Investment Income, Net (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Financial Statement Details [Abstract]
Interest income	$ 1,643	$ 2,317	$ 4,225
Investment accretion income (amortization expense), net	3	(463)	(1,597)
Net realized (losses) gains on investments	(4)	3	37
Investment income, net	$ 1,642	$ 1,857	$ 2,665

Viracta Investment and Convertible Notes - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2019	May 31, 2019	Jan. 31, 2019	Dec. 31, 2018	Mar. 31, 2017
Schedule Of Investments [Line Items]
Equity securities			$ 9,253			$ 8,500	$ 8,500
2018 Note and Warrant Purchase Agreement
Schedule Of Investments [Line Items]
Equity securities			$ 9,300
Purchase of convertible note	$ 400	$ 400
Convertible note accrued interest rate	8.00%	8.00%
Debt instrument maturity date	1 year	1 year
2018 Note and Warrant Purchase Agreement \| Common Stock
Schedule Of Investments [Line Items]
Warrants exercised to acquire shares				253,120
2018 Note and Warrant Purchase Agreement \| Series B Preferred Stock
Schedule Of Investments [Line Items]
Preferred stock value					$ 800

Financial Instruments Investments in Debt Securities - Schedule of Investments in Debt Securities (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale, Amortized Cost	$ 37,642
Available-for-sale, Unrealized Gains	10
Available-for-sale, Unrealized Losses	(11)
Available-for-sale, Fair Value	$ 37,641
Available-for-sale, Weighted- Average Remaining Contractual Life	3 months 18 days
Notes Receivable
Schedule Of Available For Sale Securities [Line Items]
Held-to-maturity, Amortized Cost		$ 723
Held-to-maturity, Unrealized Gains		0
Held-to-maturity, Unrealized Losses		0
Held-to-maturity, Fair Value		723
Current Assets
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale, Amortized Cost	$ 36,141	57,463
Available-for-sale, Unrealized Gains	10	1
Available-for-sale, Unrealized Losses	(7)	(136)
Available-for-sale, Fair Value	$ 36,144	57,328
Available-for-sale, Weighted- Average Remaining Contractual Life	2 months 12 days
Available-for-sale and held-to-maturity, Amortized Cost		58,186
Available-for-sale and held-to-maturity, Unrealized Gains		1
Available-for-sale and held-to-maturity, Unrealized Losses		(136)
Available-for-sale and held-to-maturity, Fair Value		58,051
Current Assets \| Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale, Amortized Cost	$ 32,382	57,463
Available-for-sale, Unrealized Gains	10	1
Available-for-sale, Unrealized Losses	(3)	(136)
Available-for-sale, Fair Value	$ 32,389	57,328
Available-for-sale, Weighted- Average Remaining Contractual Life	2 months 12 days
Current Assets \| Foreign Government Bonds
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale, Amortized Cost	$ 1,007
Available-for-sale, Unrealized Gains	0
Available-for-sale, Unrealized Losses	0
Available-for-sale, Fair Value	$ 1,007
Available-for-sale, Weighted- Average Remaining Contractual Life	3 months 18 days
Current Assets \| Government Sponsored Securities
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale, Amortized Cost	$ 2,752
Available-for-sale, Unrealized Gains	0
Available-for-sale, Unrealized Losses	(4)
Available-for-sale, Fair Value	$ 2,748
Available-for-sale, Weighted- Average Remaining Contractual Life	6 months
Noncurrent Assets
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale, Amortized Cost	$ 1,501	5,823
Available-for-sale, Unrealized Gains	0	0
Available-for-sale, Unrealized Losses	(4)	(122)
Available-for-sale, Fair Value	$ 1,497	5,701
Available-for-sale, Weighted- Average Remaining Contractual Life	1 year 8 months 12 days
Available-for-sale and held-to-maturity, Amortized Cost		64,009
Available-for-sale and held-to-maturity, Unrealized Gains		1
Available-for-sale and held-to-maturity, Unrealized Losses		(258)
Available-for-sale and held-to-maturity, Fair Value		63,752
Noncurrent Assets \| Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale, Amortized Cost	$ 1,501	3,067
Available-for-sale, Unrealized Gains	0	0
Available-for-sale, Unrealized Losses	(4)	(76)
Available-for-sale, Fair Value	$ 1,497	2,991
Available-for-sale, Weighted- Average Remaining Contractual Life	1 year 8 months 12 days
Noncurrent Assets \| Government Sponsored Securities
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale, Amortized Cost		2,756
Available-for-sale, Unrealized Gains		0
Available-for-sale, Unrealized Losses		(46)
Available-for-sale, Fair Value		$ 2,710

Financial Instruments Investments in Debt Securities - Additional Information (Detail) - Security	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Maximum
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale securities, period of unrealized loss positions	12 months	12 months
Minimum
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale securities, period of unrealized loss positions	12 months	12 months
Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Number of available-for-sale securities in unrealized loss positions	14

Financial Instruments Investments in Debt Securities - Accumulated Unrealized Losses on Debt Securities Classified as Available-for-Sale in Continuous Loss Position (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Schedule Of Available For Sale Securities [Line Items]
Available-for-Sale Investments, Less than 12 months, Estimated Fair Value	$ 11,021	$ 32,010
Available-for-Sale Investments, Less than 12 months, Gross Unrealized Losses	(3)	(26)
Available-for-Sale Investments, More than 12 months, Estimated Fair Value	4,245	29,373
Available-for-Sale Investments, More than 12 months, Gross Unrealized Losses	(8)	(232)
Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Available-for-Sale Investments, Less than 12 months, Estimated Fair Value	11,021	32,010
Available-for-Sale Investments, Less than 12 months, Gross Unrealized Losses	(3)	(26)
Available-for-Sale Investments, More than 12 months, Estimated Fair Value	1,497	26,663
Available-for-Sale Investments, More than 12 months, Gross Unrealized Losses	(4)	(186)
Government Sponsored Securities
Schedule Of Available For Sale Securities [Line Items]
Available-for-Sale Investments, Less than 12 months, Estimated Fair Value	0	0
Available-for-Sale Investments, Less than 12 months, Gross Unrealized Losses	0	0
Available-for-Sale Investments, More than 12 months, Estimated Fair Value	2,748	2,710
Available-for-Sale Investments, More than 12 months, Gross Unrealized Losses	$ (4)	$ (46)

Financial Instruments Investments in Debt Securities - Schedule of Realized Gains and Losses on Sales of Available-for-Sale Debt Securities (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Debt Securities Realized Gain Loss [Abstract]
Available-for-sale Securities, Gross Realized Gains	$ 4	$ 3	$ 52
Available-for-sale Securities, Gross Realized Losses	(8)	0	(15)
Available for Sale Securities, Net Realized Gains (Losses)	$ (4)	$ 3	$ 37

Collaboration and License Agreements - Additional Information (Detail)	1 Months Ended		12 Months Ended
	May 31, 2017 USD ($)	Feb. 28, 2010 USD ($)	Dec. 31, 2019 USD ($) Patient	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2004 USD ($)
Licensing Agreement [Line Items]
Milestone payments			$ 0
Intrexon Corporation
Licensing Agreement [Line Items]
Milestone Payment Amount			0	$ 0	$ 0
Milestone payments			0	0	0
License agreement term (years)		17 years
Agreement one time fee		$ 400,000
First IND Filing \| Intrexon Corporation
Licensing Agreement [Line Items]
Milestone Payment Amount		100,000
First Phase II Clinical Trial \| Intrexon Corporation
Licensing Agreement [Line Items]
Milestone Payment Amount		100,000
First Phase III Clinical Trial \| Intrexon Corporation
Licensing Agreement [Line Items]
Milestone Payment Amount		400,000
Commercial Sale Related to Licensed Products \| Intrexon Corporation
Licensing Agreement [Line Items]
Milestone Payment Amount		$ 500,000
Rush University Medical Center License Agreement
Licensing Agreement [Line Items]
Period of license agreement							12 years
Minimum annual royalty payment							$ 25,000
Payments in license agreement							2,500,000
Minimum sales milestone of license for first year							$ 300,000
Royalty expense earned or paid			0	4,200	25,000
Milestone payments			$ 0	0	0
GSH-BSD
Licensing Agreement [Line Items]
Payments for initial license fees						$ 1,100,000
Viracta Therapeutics, Inc.
Licensing Agreement [Line Items]
License agreement termination notice period	90 days
Viracta Therapeutics, Inc. \| Minimum
Licensing Agreement [Line Items]
Milestone Payment Amount	$ 10,000,000
Viracta Therapeutics, Inc. \| Maximum
Licensing Agreement [Line Items]
Milestone Payment Amount	$ 25,000,000
Altor
Licensing Agreement [Line Items]
Maximum number of patients in phase 1 and 2 for clinical trials \| Patient			400
Supplies and milestone charges for conducting clinical trials			$ 0	$ 0	$ 0

Commitment and Contingencies - Additional Information (Detail)		1 Months Ended							3 Months Ended	12 Months Ended
	Aug. 09, 2019 USD ($)	Aug. 31, 2019	Aug. 31, 2018 USD ($)	Sep. 30, 2016 USD ($) ft²	Jun. 30, 2016 USD ($) ft² $ / ft²	Mar. 31, 2016 ft²	Nov. 30, 2015 USD ($) ft²	Jun. 30, 2015 USD ($) ft²	Sep. 30, 2018 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($) ft²	Jan. 01, 2019
Commitments And Contingencies [Line Items]
Litigation settlement amount										$ 12,000,000
Attorney's fee to plaintiffs	$ 500,000
Increase in operating lease right-of-use assets										$ 800,000
Weighted average remaining lease term										4 years 6 months			5 years 4 months 24 days
Weighted average discount rate										9.00%			9.00%
Cash outflows from operating leases excluding variable lease cost										$ 4,400,000
Period of agreement										elected not to recognize right-of-use assets and lease liabilities for qualifying short-term leases with an initial lease term of 12 months or less at lease inception
Rent expense											$ 2,800,000	$ 2,700,000
Woburn, Massachusetts
Commitments And Contingencies [Line Items]
Increase in operating lease right-of-use assets										$ 600,000
Number of square foot of facility leased \| ft²					8,153	7,893
Base rent - monthly					$ 19,000
Initial term of lease arrangement						48 months
Lease commencement date						Apr. 29, 2016
Lease expiration date						May 31, 2020
Addition to number of square foot of facility leased \| ft²					260
Annual increase of base rent \| $ / ft²					1
Period of agreement										In June 2016, the lease was amended to add 260 square feet, for a total of 8,153 square feet. Base rent for the initial term of the lease is $19,000 per month with a $1 per square foot annual increase on each anniversary date.
Optional extended lease term		2 years
Lease agreement extended lease period		May 31, 2022
Commitment; San Diego
Commitments And Contingencies [Line Items]
Number of square foot of facility leased \| ft²								44,700
Base rent - monthly								$ 200,000
Percentage of annual increase of base rent								3.00%
Initial term of lease arrangement								7 years
NantBioScience
Commitments And Contingencies [Line Items]
Reimbursed upfront payment to third-party			$ 900,000
Related party transaction, amount paid to third-party			500,000
Related party transaction, aggregate value			$ 1,400,000
Initial term of agreement entered into with the related party by the entity			10 years			5 years
Related party agreement expiration date			2027-06
Number of square foot of facility leased \| ft²												1,965
Doug St, LLC
Commitments And Contingencies [Line Items]
Period of agreement										The lease runs from July 2016 through July 2023. We have the option to extend the lease for an additional three year term through July 2026. The monthly rent is $0.1 million with annual increases of 3% beginning in July 2017.
Optional extended lease term				3 years
Base rent - monthly				$ 100,000
Percentage of annual increase of base rent				3.00%
Annual percentage increases to base rent commencement date				Jul. 31, 2017
Doug St, LLC \| El Segundo California
Commitments And Contingencies [Line Items]
Number of square foot of facility leased \| ft²				24,250
NantWorks
Commitments And Contingencies [Line Items]
Number of square foot of facility leased \| ft²							9,500
Period of agreement										The license was effective in May 2015 and extends through December 2020. The monthly rent is $47,000, with annual increases of 3% beginning in January 2017.
Base rent - monthly							$ 47,000
Percentage of annual increase of base rent							3.00%
Annual percentage increases to base rent commencement date							Jan. 31, 2017
Prepaid Expenses and Other Current Assets
Commitments And Contingencies [Line Items]
Insurance claim receivable										$ 34,000,000	$ 10,900,000
Directors and Officers Insurance Policy
Commitments And Contingencies [Line Items]
Litigation settlement amount										10,800,000
Selling, General and Administrative
Commitments And Contingencies [Line Items]
Litigation settlement amount									$ 1,200,000
Operating Expenses
Commitments And Contingencies [Line Items]
Operating lease expense										5,100,000
Variable lease costs										$ 1,200,000

Commitment and Contingencies - Schedule of Lease Balances (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Assets And Liabilities Lessee [Abstract]
Operating lease right-of-use assets, net	$ 11,729	$ 13,532	$ 0
Other current liabilities	3,206	2,960	0
Operating lease liability, less current portion	$ 10,885	$ 13,407	$ 0

Commitment and Contingencies - Summary of Future Minimum Lease Payments (Detail) $ in Thousands	Dec. 31, 2019 USD ($)
Commitments And Contingencies Disclosure [Abstract]
2020	$ 4,271
2021	3,753
2022	3,671
2023	2,546
2024	1,083
Thereafter	1,729
Total future minimum lease payments	17,053
Less: Interest	2,962
Present value of operating lease liabilities	$ 14,091

Commitment and Contingencies - Summary of Future Minimum Lease Payments (Parenthetical) (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($)
Commitments And Contingencies Disclosure [Abstract]
Operating lease payments related to options to extend lease terms	$ 3.3

Related Party Agreements - Additional Information (Detail)	1 Months Ended													12 Months Ended			50 Months Ended
	Oct. 31, 2019 USD ($)	Jul. 31, 2019 USD ($)	May 31, 2019 USD ($)	Nov. 30, 2018 USD ($) shares	Aug. 31, 2018 USD ($)	May 31, 2018 USD ($)	Mar. 31, 2018	Apr. 30, 2017 USD ($) ft²	Sep. 30, 2016 USD ($) ft²	Apr. 30, 2016 USD ($)	Mar. 31, 2016	Nov. 30, 2015 USD ($) ft²	Jun. 30, 2015	Dec. 31, 2019 USD ($) Officer shares	Dec. 31, 2018 USD ($) shares	Dec. 31, 2017 USD ($) ft² shares	Dec. 31, 2019 USD ($) Officer shares
Related Party Transaction [Line Items]
Repurchase of common stock, shares \| shares				138,349										473,586	138,349	3,633,610	6,403,489
Repurchase of common stock, value				$ 200,000										$ 501,000	$ 228,000	$ 15,227,000
Research and development														49,785,000	55,718,000	42,044,000
Due to related parties														486,000	1,696,000		$ 486,000
Selling, general and administrative expense														18,065,000	42,718,000	57,121,000
Proceeds from sales of property, plant and equipment														0	412,000	0
NantHealth Labs, Inc.
Related Party Transaction [Line Items]
Initial term of agreement entered into with the related party by the entity							5 years
Related party, agreement renewal term							1 year
Research and development														10,000	300,000
Due to related parties														0	49,300		0
Immuno-Oncology Clinic, Inc. \| California
Related Party Transaction [Line Items]
Research and development														1,100,000	2,700,000	800,000
Due to related parties														$ 100,000	600,000		$ 100,000
Number of officers \| Officer														1			1
Initial term of agreement		1 year
Estimated cost for new agreement with clinic		$ 7,500,000
Related party transaction installment payment	$ 1,875,000	3,750,000
Prepayments remain unearned extension description														To the extent any portion of the prepayments remain unearned by the Clinic on the third anniversary of the new agreement, we may elect at our sole discretion either to (i) not extend the term of the new agreement and have the Clinic reimburse us for the total amount of any remaining unused portion of the prepayments, or (ii) extend the term of the new agreement for up to three additional one year periods, at which time the Clinic will reimburse us for the total amount of any remaining unused portion of the prepayments plus interest if reimbursement is not made within 60 days of expiration.
Notice period to terminate new agreement														60 days
Prepaid balance included in prepaid expenses and other current assets and other assets														$ 5,100,000			$ 5,100,000
Related party transaction, aggregate value		$ 7,500,000
Tensorcom, Inc \| San Diego California
Related Party Transaction [Line Items]
Period of agreement														The lease ran from May 1, 2017 through April 30, 2018.
Number of square foot of facility leased \| ft²								6,557
Base rent - monthly								$ 25,000
Due between parties														$ 0	0		0
Tensorcom, Inc \| San Diego California \| Other Income
Related Party Transaction [Line Items]
Sublease revenue recognized															100,000	200,000
Doug St, LLC
Related Party Transaction [Line Items]
Period of agreement														The lease runs from July 2016 through July 2023.
Base rent - monthly									$ 100,000
Due between parties														$ 0	0		0
Percentage of annual increase of base rent									3.00%
Annual percentage increases to base rent commencement date									Jul. 31, 2017
Doug St, LLC \| Research and Development
Related Party Transaction [Line Items]
Lease expense														900,000	200,000	200,000
Doug St, LLC \| El Segundo California
Related Party Transaction [Line Items]
Number of square foot of facility leased \| ft²									24,250
NantBioScience
Related Party Transaction [Line Items]
Initial term of agreement entered into with the related party by the entity					10 years						5 years
Research and development														$ 600,000	600,000	$ 600,000
Estimated cost for new agreement with clinic					$ 1,400,000
Number of square foot of facility leased \| ft²																1,965
Related party transaction,reimbursement payment to a related-party					900,000
Related party transaction, amount paid to third-party					500,000
Related party transaction, aggregate value					$ 1,400,000
Related party agreement expiration date					2027-06
Research and development expense, ratable payment period														12 months
Prepayment for services amount			$ 600,000		$ 600,000			$ 600,000		$ 600,000
NantBioScience \| Prepaid Expenses and Other Current Assets
Related Party Transaction [Line Items]
Research and development														$ 100,000	100,000
Due between parties														8,400	49,000		8,400
NantBioScience \| Other Income
Related Party Transaction [Line Items]
Sublease revenue recognized														100,000	100,000	$ 10,000
NantWorks
Related Party Transaction [Line Items]
Number of square foot of facility leased \| ft²												9,500
Base rent - monthly												$ 47,000
Percentage of annual increase of base rent												3.00%
Annual percentage increases to base rent commencement date												Jan. 31, 2017
Transfer of deposit amount to third party						$ 400,000
NantWorks \| Shared Services Agreement
Related Party Transaction [Line Items]
Research and development														1,500,000	3,300,000	3,200,000
Selling, general and administrative expense														2,100,000	2,800,000	3,600,000
NantWorks \| Reimbursements \| Shared Services Agreement
Related Party Transaction [Line Items]
Research and development														2,300,000	2,600,000	1,000,000
Due to related parties														400,000	1,100,000		400,000
Selling, general and administrative expense														1,200,000	600,000	400,000
NantWorks \| Research and Development
Related Party Transaction [Line Items]
Lease expense														600,000	200,000	200,000
NantOmics
Related Party Transaction [Line Items]
Initial term of agreement entered into with the related party by the entity													5 years
Related party, agreement renewal term													1 year
Research and development														100,000	100,000	100,000
Due to related parties														0	24,000		0
ImmunityBio
Related Party Transaction [Line Items]
Initial term of agreement entered into with the related party by the entity													5 years
Related party, agreement renewal term													1 year
Research and development														100,000	100,000	300,000
Due between parties														0	0		0
Proceeds from sales of property, plant and equipment				300,000
Loss on disposal of assets				$ 100,000
Related parties, capitalized equipment amount														1,800,000	1,100,000
Prepaid expenses and other current assets														500,000	500,000		$ 500,000
VivaBioCell S.p.A.
Related Party Transaction [Line Items]
Research and development														0	100,000	600,000
Altor
Related Party Transaction [Line Items]
Supplies and milestone charges for conducting clinical trials														$ 0	$ 0	$ 0

Stockholders' Equity - Additional Information (Detail) - USD ($)	1 Months Ended	12 Months Ended			50 Months Ended
	Nov. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2019	Nov. 30, 2015
Equity [Abstract]
Total amount authorized for repurchase						$ 50,000,000
Repurchase of common stock, shares	138,349	473,586	138,349	3,633,610	6,403,489
Repurchase of common stock excluding commissions, value		$ 500,000	$ 200,000	$ 15,200,000	$ 31,700,000
Broker commissions on repurchases					100,000
Remaining authorized repurchase amount		$ 18,300,000			$ 18,300,000
Common stock, shares authorized		500,000,000	500,000,000		500,000,000
Common stock, par value		$ 0.0001	$ 0.0001		$ 0.0001
Common stock, shares issued		98,460,404	79,087,734		98,460,404
Common stock, shares outstanding		98,460,404	79,087,734		98,460,404

Stockholders' Equity - Summary of Common Shares Reserved for Issuance (Detail)	Dec. 31, 2019 shares
Class Of Stock [Line Items]
Total shares reserved for future issuance	5,646,378
Outstanding Stock Options
Class Of Stock [Line Items]
Total shares reserved for future issuance	4,506,950
Outstanding RSUs
Class Of Stock [Line Items]
Total shares reserved for future issuance	1,139,428
Outstanding Warrants
Class Of Stock [Line Items]
Total shares reserved for future issuance	0

Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended		12 Months Ended
	Jun. 30, 2019	Mar. 31, 2014	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Proceeds from exercises of warrants			$ 35.2	$ 0.1	$ 0.1
2015 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future grants			4,300,000
Additional Shares that may be added to shares reserved for issuance			2,300,000
Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock options, vested and exercisable				5,577,531	5,114,656
Aggregate intrinsic value of stock options exercised			$ 0.2	$ 0.6	$ 1.7
Cash received from exercised options			$ 4.1	$ 0.0	$ 1.2
Shares granted to employee			0		0
Unrecognized compensation cost related to non-vested stock options			$ 1.1
Weighted-average period for recognition			2 years 8 months 12 days
Employee Stock Option \| 2014 Equity Incentive Plan \| Common Class A
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for issuance		11,109,000
Share-based compensation, expiration period		10 years
Employee Stock Option \| 2015 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Additional common shares reserved for future issuance	3,000,000
Key Executives Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares granted to employee				800,000
Exercise price			$ 3.07
Share-based compensation arrangement, award vesting rights, percentage			25.00%
Remaining vesting period			3 years
Non Employee Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares granted to employee			0	0	0
Non Employee Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average period for recognition			9 months 18 days
Grants of restricted stock			0	90,906	77,250
Unrecognized compensation cost related to non-vested stock options			$ 0.1
Outstanding RSUs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average period for recognition			1 year 8 months 12 days
Grants of restricted stock			749,793	487,472	615,983
Unrecognized compensation cost related to non-vested stock options			$ 1.4
Employee Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average period for recognition			1 year 9 months 18 days
Unrecognized compensation cost related to non-vested stock options			$ 1.3

Stock-Based Compensation - Stock Based Compensation Expenses Related to Statement of Operations (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 2,627	$ 23,382	$ 36,997
Warrants For Common Stock \| Officer
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	0	17,817	31,584
Employee Stock Option
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	1,309	4,057	4,267
Employee RSUs
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	938	1,193	894
Non-employee RSUs
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	380	315	252
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	499	460	102
Selling, General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 2,128	$ 22,922	$ 36,895

Stock-Based Compensation - Stock Option Activity (Detail) - Employee Stock Option - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Number of Shares
Stock Options, Beginning Balance	6,493,250	5,693,250	6,307,386
Stock Options, Options exercised	(1,986,300)		(614,136)
Stock Options, Options granted		800,000
Stock Options, Ending Balance	4,506,950	6,493,250	5,693,250	6,307,386
Stock Options, Vested and Exercisable	3,973,614
Weighted Average Exercise Price
Weighted Average Exercise Price, Outstanding Beginning balance	$ 7.14	$ 7.71	$ 7.14
Weighted Average Exercise Price, Options exercised	2.06		1.88
Weighted Average Exercise Price, Options granted		3.07
Weighted Average Exercise Price, Outstanding Ending balance	9.37	$ 7.14	$ 7.71	$ 7.14
Weighted Average Exercise Price, Vested and Exercisable	$ 10.22
Aggregate Intrinsic Value
Aggregate Intrinsic Value, Outstanding, Beginning balance	$ 563	$ 11,920	$ 19,100
Aggregate Intrinsic Value, Outstanding, Ending balance	5,710	$ 563	$ 11,920	$ 19,100
Aggregate Intrinsic Value, Vested and Exercisable	$ 5,326
Weighted Average Remaining Contractual Life
Weighted Average Remaining Contractual Life, Outstanding	5 years 9 months 18 days	4 years 9 months 18 days	5 years 3 months 18 days	6 years 4 months 24 days
Weighted Average Remaining Contractual Life, Vested and Exercisable	5 years 6 months

Stock-Based Compensation - Summary of Options Outstanding and Vested Pricing of Exercise Prices (Detail) - Employee Stock Option	12 Months Ended
	Dec. 31, 2019 $ / shares shares
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Options Outstanding, Number Outstanding	4,506,950
Options Outstanding, Weighted- Average Remaining Contractual Life (in years)	5 years 9 months 18 days
Options Outstanding, Number Exercisable	3,973,614
Options Outstanding, Weighted- Average Remaining Contractual Life (in years)	5 years 6 months
$0.42
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise Prices \| $ / shares	$ 0.42
Options Outstanding, Number Outstanding	589,660
Options Outstanding, Weighted- Average Remaining Contractual Life (in years)	4 years 10 months 24 days
Options Outstanding, Number Exercisable	589,660
Options Outstanding, Weighted- Average Remaining Contractual Life (in years)	4 years 10 months 24 days
$1.76
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise Prices \| $ / shares	$ 1.76
Options Outstanding, Number Outstanding	699,060
Options Outstanding, Weighted- Average Remaining Contractual Life (in years)	5 years
Options Outstanding, Number Exercisable	699,060
Options Outstanding, Weighted- Average Remaining Contractual Life (in years)	5 years
$2.00
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise Prices \| $ / shares	$ 2.00
Options Outstanding, Number Outstanding	962,780
Options Outstanding, Weighted- Average Remaining Contractual Life (in years)	5 years 1 month 6 days
Options Outstanding, Number Exercisable	962,780
Options Outstanding, Weighted- Average Remaining Contractual Life (in years)	5 years 1 month 6 days
$3.07
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise Prices \| $ / shares	$ 3.07
Options Outstanding, Number Outstanding	800,000
Options Outstanding, Weighted- Average Remaining Contractual Life (in years)	8 years 8 months 12 days
Options Outstanding, Number Exercisable	266,664
Options Outstanding, Weighted- Average Remaining Contractual Life (in years)	8 years 8 months 12 days
$25.00
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise Prices \| $ / shares	$ 25.00
Options Outstanding, Number Outstanding	1,455,450
Options Outstanding, Weighted- Average Remaining Contractual Life (in years)	5 years 7 months 6 days
Options Outstanding, Number Exercisable	1,455,450
Options Outstanding, Weighted- Average Remaining Contractual Life (in years)	5 years 7 months 6 days

Stock-Based Compensation - Black-Scholes Option-Pricing Model to Determine Fair Value of Assumptions Used for Employee Stock Options Granted (Detail) - Employee Stock Option	12 Months Ended
	Dec. 31, 2018 $ / shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate	2.80%
Expected volatility	75.90%
Dividend yield	0.00%
Weighted-average measurement date fair value	$ 2.09
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (years)	6 years
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (years)	6 years 1 month 6 days

Stock-Based Compensation - Restricted Stock Units (RSUs) Activity (Detail) - Outstanding RSUs - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Shares, Unvested, Beginning balance	867,911	888,189	814,456
Number of Shares, Granted	749,793	487,472	615,983
Number of Shares, Vested	(395,051)	(172,330)	(244,209)
Number of Shares, Forfeited/Canceled	(83,225)	(335,420)	(298,041)
Number of Shares, Unvested, Ending balance	1,139,428	867,911	888,189
Weighted-Average Grant Date Fair Value, Unvested, beginning balance	$ 6.69	$ 8.14	$ 13.98
Weighted-Average Grant Date Fair Value, Granted	1.12	3.57	4.50
Weighted-Average Grant Date Fair Value, Vested	8.83	6.16	15.82
Weighted-Average Grant Date Fair Value, Forfeited/Canceled	7.29	6.27	10.28
Weighted-Average Grant Date Fair Value, Unvested, ending balance	$ 2.23	$ 6.69	$ 8.14

Stock-Based Compensation - Summary of Warrant Activity (Detail) - Outstanding Warrants - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Warrant [Line Items]
Number of shares Warrants, Beginning Balance	17,589,250	17,721,088	17,768,314
Number of shares Warrants exercised	(17,589,250)	(93,254)	(47,226)
Number of shares Warrants expired		(38,584)
Number of shares Warrants, Ending Balance	0	17,589,250	17,721,088
Number of shares Warrants, Vested and exercisable Ending Balance	0

Income Taxes - Summary of Loss Before Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
U.S. loss before taxes	$ (65,286)	$ (94,423)	$ (94,734)
Foreign loss before taxes	(600)	(2,306)	(2,182)
Loss before income taxes	$ (65,886)	$ (96,729)	$ (96,916)

Income Taxes - Summary of Income Tax Benefit (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Current:
Federal	$ 0	$ 0	$ 0
State	3	3	4
Foreign	0	0	0
Total Current	3	3	4
Deferred:
Federal	(79)	0	0
State	(21)	(8)	0
Foreign	0	(498)	(497)
Total Deferred	(100)	(506)	(497)
Income tax benefit	$ (97)	$ (503)	$ (493)

Income Taxes - Components of Net Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Net operating loss carryforwards	$ 78,377	$ 61,915
Stock compensation	8,536	79,281
Operating lease liabilities	3,884	0
Depreciation and amortization	2,042	0
Tax credits	898	845
Accrued compensation	775	795
Leases and other accrued liabilities	453	2,909
Accrued legal expenses	0	308
Total deferred tax assets	94,965	146,053
Deferred tax liabilities:
Foreign intangibles	0	(1)
Operating lease right-of-use assets	(3,233)	0
Depreciation and amortization	0	(1,279)
Total deferred tax liabilities	(3,233)	(1,280)
Net deferred tax assets	91,732	144,773
Valuation allowance	(91,732)	(144,773)
Net deferred tax liability	$ 0	$ 0

Income Taxes - Reconciliation of Federal Statutory Income Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Tax computed at federal statutory rate	21.00%	21.00%	34.00%
State income taxes, net of federal tax benefit	(19.40%)	6.20%	5.30%
Tax rate adjustment	0.10%	(0.30%)	4.80%
Tax Cuts and Jobs Act	0.00%	0.00%	(53.40%)
Research and development credits	0.20%	0.10%	0.60%
Stock-based compensation	(82.50%)	(0.10%)	(0.30%)
Other	(0.10%)	0.30%	0.80%
Valuation allowance	80.50%	(26.70%)	8.70%
Effective income tax rate	(0.20%)	0.50%	0.50%

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax [Line Items]
Corporate tax rate	21.00%	21.00%	34.00%
Minimum Amount for elimination of several business deductions and credits, including deductions for certain executive compensation	$ 1,000,000
Reduction in deferred tax asset balance			$ 51,700,000
Cumulative change in ownership	50.00%
Period of cumulative ownership change	3 years
Derecognized deferred tax assets	$ 800,000
Deferred tax assets valuation allowance	91,732,000	$ 144,773,000
Deferred tax assets change in valuation allowance	53,000,000
Tax benefits credited to contributed capital	200,000
Unrecognized tax benefits that would not impact effective tax rate	14,100,000
California \| Research Tax Credits
Income Tax [Line Items]
Tax credit carryforwards	5,700,000
Federal
Income Tax [Line Items]
Net operating loss carryforwards	$ 291,800,000
Net operating loss carryforwards expiration date	2024
Federal \| Research Tax Credits
Income Tax [Line Items]
Tax credit carryforwards	$ 8,500,000
Tax credit carryforward expiration period	2034
State
Income Tax [Line Items]
Net operating loss carryforwards	$ 255,700,000
Net operating loss carryforwards expiration date	2030
State \| Research Tax Credits
Income Tax [Line Items]
Tax credit carryforward expiration period	2031
Foreign
Income Tax [Line Items]
Net operating loss carryforwards	$ 200,000
Net operating loss carryforwards expiration date	2022
Maximum
Income Tax [Line Items]
Corporate tax rate			35.00%
Maximum \| California
Income Tax [Line Items]
Tax year open for examination	2019
Maximum \| Federal
Income Tax [Line Items]
Tax year open for examination	2019
Minimum \| California
Income Tax [Line Items]
Tax year open for examination	2015
Minimum \| Federal
Income Tax [Line Items]
Tax year open for examination	2016

Income Taxes - Summarizes of Changes in Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Unrecognized tax benefits at beginning balance	$ 11,983	$ 6,577
Increase for prior year tax positions		798
Decrease for prior year tax positions	(7)
Increase for current year tax positions	3,680	4,608
Unrecognized tax benefits at ending balance	$ 15,656	$ 11,983

Summary of Quarterly Data (Unaudited) (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Data [Abstract]
Revenue	$ 9	$ 12	$ 17	$ 5	$ 7	$ 31	$ 4	$ 5	$ 43	$ 47	$ 45
Operating expenses	16,120	16,077	17,313	18,340	17,726	24,139	28,282	28,289	67,850	98,436	99,165
Operating loss	(16,111)	(16,065)	(17,296)	(18,335)	(17,719)	(24,108)	(28,278)	(28,284)	(67,807)	(98,389)	(99,120)
Net loss	$ (15,641)	$ (15,581)	$ (16,682)	$ (17,885)	$ (17,340)	$ (23,635)	$ (27,732)	$ (27,519)	$ (65,789)	$ (96,226)	$ (96,423)
Net loss per share - basic and diluted	$ (0.16)	$ (0.16)	$ (0.17)	$ (0.22)	$ (0.22)	$ (0.30)	$ (0.35)	$ (0.35)	$ (0.70)	$ (1.22)	$ (1.20)
Shares used in calculating net loss per share - basic and diluted	98,419,166	98,331,695	98,594,355	81,261,302	79,177,962	79,204,765	79,107,208	79,036,614	94,210,087	79,132,220	80,583,910

- Definition

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

+ References + Details

Employee Benefits - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
401(k) Plan
Defined Contribution Plan Disclosure [Line Items]
Employee benefit plan, company contributions	$ 0.6	$ 0.5	$ 0.4

Subsequent Events - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 29, 2020
Subsequent Event [Line Items]
Research and development (including amounts with related parties)	$ 49,785	$ 55,718	$ 42,044
Collaborative Arrangement
Subsequent Event [Line Items]
Research and development (including amounts with related parties)	$ 100
Collaborative Arrangement \| Subsequent Event
Subsequent Event [Line Items]
Expect joint study cost				$ 2,100

Fair Value Measurements - Summary of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	$ 53,149	$ 79,850
Current Assets \| Cash and cash equivalents
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	15,508	16,821
Current Assets \| Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	32,389	57,328
Current Assets \| Foreign Government Bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	1,007
Current Assets \| Government Sponsored Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	2,748
Noncurrent Assets \| Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	1,497	2,991
Noncurrent Assets \| Government Sponsored Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value		2,710
Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	15,508	16,821
Level 1 \| Current Assets \| Cash and cash equivalents
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	15,508	16,821
Level 1 \| Current Assets \| Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	0	0
Level 1 \| Current Assets \| Foreign Government Bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	0
Level 1 \| Current Assets \| Government Sponsored Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	0
Level 1 \| Noncurrent Assets \| Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	0	0
Level 1 \| Noncurrent Assets \| Government Sponsored Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value		0
Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	37,641	63,029
Level 2 \| Current Assets \| Cash and cash equivalents
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	0	0
Level 2 \| Current Assets \| Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	32,389	57,328
Level 2 \| Current Assets \| Foreign Government Bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	1,007
Level 2 \| Current Assets \| Government Sponsored Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	2,748
Level 2 \| Noncurrent Assets \| Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	1,497	2,991
Level 2 \| Noncurrent Assets \| Government Sponsored Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value		2,710
Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	0	0
Level 3 \| Current Assets \| Cash and cash equivalents
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	0	0
Level 3 \| Current Assets \| Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	0	0
Level 3 \| Current Assets \| Foreign Government Bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	0
Level 3 \| Current Assets \| Government Sponsored Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	0
Level 3 \| Noncurrent Assets \| Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	$ 0	0
Level 3 \| Noncurrent Assets \| Government Sponsored Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value		$ 0