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Document and Entity Information - shares	9 Months Ended
Document and Entity Information - shares	Sep. 30, 2017	Oct. 31, 2017
Document Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	Q3
Trading Symbol	NK
Entity Registrant Name	NANTKWEST, INC.
Entity Central Index Key	0001326110
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		79,455,139

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 20,920	$ 8,083
Due from related parties	61	1,089
Prepaid expenses and other current assets	4,525	5,135
Marketable securities	131,347	190,838
Total current assets	156,853	205,145
Marketable securities, noncurrent	34,198	87,571
Property, plant and equipment, net	74,471	18,906
Cost method investment	8,500	0
Intangible assets, net	3,391	5,086
Other assets	324	788
Total assets	277,737	317,496
Current liabilities:
Accounts payable	9,485	4,045
Accrued expenses	15,838	5,864
Due to related parties	1,986	1,753
Other current liabilities	1,365	891
Total current liabilities	28,674	12,553
Build-to-suit liability, less current portion	5,062	5,651
Financing obligation, less current portion	1,814	2,025
Deferred rent	3,461	2,426
Deferred tax liability	681	996
Other liabilities	341	427
Total liabilities	40,033	24,078
Commitments and contingencies (Note 8)	0	0
Stockholders’ equity
Common stock	8	8
Additional paid-in capital	709,353	680,757
Accumulated other comprehensive loss	(202)	(284)
Accumulated deficit	(471,455)	(387,063)
Total stockholders’ equity	237,704	293,418
Total liabilities and stockholders’ equity	$ 277,737	$ 317,496

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2017	Dec. 31, 2016
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	79,440,700	81,983,937
Common stock, shares outstanding	79,440,700	81,983,937

Condensed Consolidated Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Statement [Abstract]
Revenue	$ 8	$ 12	$ 33	$ 30
Operating expenses:
Research and development	11,069	8,364	30,023	19,708
Selling, general and administrative	13,381	24,423	43,736	79,678
Total operating expenses	24,450	32,787	73,759	99,386
Loss from operations	(24,442)	(32,775)	(73,726)	(99,356)
Other income:
Investment income, net	680	795	2,140	2,302
Interest expense	(393)	(29)	(584)	(29)
Other income (expense), net	87	60	(87)	89
Total other income	374	826	1,469	2,362
Loss before income taxes	(24,068)	(31,949)	(72,257)	(96,994)
Income tax benefit	(99)	(52)	(321)	(423)
Net loss	$ (23,969)	$ (31,897)	$ (71,936)	$ (96,571)
Net loss per share:
Basic and diluted	$ (0.30)	$ (0.39)	$ (0.89)	$ (1.18)
Weighted average number of shares during the period:
Basic and diluted	79,440,591	82,154,219	80,996,732	82,019,203

Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (23,969)	$ (31,897)	$ (71,936)	$ (96,571)
Other comprehensive income, net of income taxes:
Net unrealized gain (loss) on available-for-sale securities	59	(241)	(177)	405
Reclassification of net realized gains on available-for-sale securities included in net loss	(24)	(48)	(25)	(78)
Total other comprehensive income (loss)	35	(289)	(202)	327
Comprehensive loss	$ (23,934)	$ (32,186)	$ (72,138)	$ (96,244)

Condensed Consolidated Statement of Stockholders' Equity (Unaudited) - 9 months ended Sep. 30, 2017 - 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	81,983,937
Exercise of stock options	$ 1,154	$ 0	1,154	0	0
Exercise of stock options, Shares		614,136
Stock-based compensation expense	28,113	$ 0	28,113	0	0
Vesting of restricted stock units		35,793
Exercise of warrants	38	$ 0	38	0	0
Exercise of warrants, Shares		32,787
Employee payroll taxes withheld related to option exercises and vesting of restricted stock units	(709)	$ 0	(709)	0	0
Employee payroll taxes withheld related to option exercises and vesting of restricted stock units, Shares		(153,744)
Repurchase of common stock	$ (12,456)	$ 0	0	0	(12,456)
Repurchase of common stock, Shares	(3,072,209)	(3,072,209)
Other comprehensive income, net	$ 82	$ 0	0	82	0
Net loss	(71,936)	0	0	0	(71,936)
Ending Balance at Sep. 30, 2017	$ 237,704	$ 8	$ 709,353	$ (202)	$ (471,455)
Ending Balance, Shares at Sep. 30, 2017	79,440,700	79,440,700

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Operating activities:
Net loss	$ (71,936)	$ (96,571)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	3,997	1,768
Stock-based compensation expense	28,113	62,586
Deferred income tax benefit	(315)	(423)
Non-cash interest items, net	648	(273)
Loss on disposal of assets	64	18
Amortization of net premiums on marketable securities	1,298	1,567
Gain on sales of marketable securities	(25)	(118)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(576)	(1,380)
Other assets	464	75
Accounts payable	1,493	321
Accrued expenses and other liabilities	(446)	2,454
Due to related parties	759	501
Deferred rent and revenue	1,322	1,635
Net cash used in operating activities	(35,140)	(27,840)
Investing activities:
Purchases of property, plant and equipment	(23,382)	(5,202)
Purchase of cost method investment	(8,500)	0
Purchases of marketable securities	(75,115)	(207,891)
Sales/maturities of marketable securities	186,815	107,885
Net cash provided by (used in) investing activities	79,818	(105,208)
Financing activities:
Principal payments of financing/capital lease obligations	(19,868)	(10)
Proceeds from exercise of stock options and warrants	1,192	1,044
Repurchase of common stock with commissions	(12,456)	(11,898)
Net share settlement for RSU vesting and option exercises	(709)	(592)
Net cash used in financing activities	(31,841)	(11,456)
Net increase (decrease) in cash and cash equivalents	12,837	(144,504)
Cash and cash equivalents, beginning of period	8,083	175,908
Cash and cash equivalents, end of period	20,920	31,404
Cash paid during the period for:
Interest	632	29
Income taxes	3	1
Supplemental disclosure of non-cash investing and financing activities:
Property and equipment purchases acquired under capital lease	19,448	0
Estimated fair value of building under build-to-suit lease	0	5,139
Property and equipment purchases included in accounts payable and accrued expenses	17,561	1,092
Unrealized gain on marketable securities	108	506
Cashless exercise of stock options and warrants	16	456
Lease incentive	$ 0	$ 239

Description of Business and Basis of Presentation	9 Months Ended
Description of Business and Basis of Presentation	Sep. 30, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Description of Business and Basis of Presentation	1. Description of Business and Basis of Presentation Organization NantKwest, Inc. (the Company) 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. The Company is 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. The Company is focused on harnessing the power of the innate immune system by using the natural killer cell to treat cancer, infectious diseases and inflammatory diseases. A critical aspect of our strategy is to invest significantly in expanding our aNK platform and the development of our product candidates. The Company holds the exclusive right to commercialize activated natural killer (aNK) cells, a commercially viable natural killer cell-line, and a variety of genetically modified derivatives capable of killing cancer and virally infected cells. The Company owns corresponding U.S. and foreign composition and methods-of-use patents and applications covering the clinical use of aNK cells as a therapeutic to treat a spectrum of clinical conditions. In addition, the Company licensed exclusive commercial rights to a portfolio of CD16 bearing aNK cells along with the corresponding U.S. and foreign composition and methods-of-use patents and applications covering the non-clinical use in laboratory testing of monoclonal antibodies, as well as clinical use as a therapeutic to treat cancers in combination with antibody products. The Company has licensed or sub-licensed its CD16 bearing aNK cell lines and intellectual property to numerous pharmaceutical and biotechnology companies for such non-clinical uses. The Company also licensed exclusive commercial rights to a unique HER2-specific receptor bearing aNK cell line along with the corresponding U.S. and foreign composition and methods-of-use patents and applications covering clinical use as a therapeutic to treat cancers. The Company retains exclusive worldwide rights to clinical and research data, intellectual property and know-how developed with the Company’s aNK cells, as well as the only clinical grade master cell bank. Unaudited Interim Financial Information The accompanying condensed consolidated balance sheet at September 30, 2017, the condensed consolidated statements of operations and comprehensive loss for the three and nine months ended September 30, 2017, the condensed consolidated statements of cash flows for the nine months ended September 30, 2017, and the condensed consolidated statement of stockholders’ equity for the nine months ended September 30, 2017 have been prepared by management of the Company and have not been audited. These financial statements have been prepared on the same basis as the audited consolidated financial statements for the fiscal year ended December 31, 2016 and, in the opinion of management, include all normal recurring adjustments necessary for a fair statement of the Company’s results for the periods presented. These financial statements should be read in conjunction with the financial statements and notes thereto for the fiscal year ended December 31, 2016 included in the Company’s Annual Report on Form 10-K. Interim operating results are not necessarily indicative of operating results for the full year. The year-end condensed consolidated balance sheet data was derived from audited financial statements, but does not include all disclosures required by accounting principles generally accepted in the United States of America (GAAP). Principles of Consolidation The Company’s condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries, Inex Bio, Inc. and 557 Doug St, LLC, and have been prepared in accordance with GAAP. All intercompany amounts have been eliminated. Liquidity As of September 30, 2017, the Company had an accumulated deficit of approximately $471.5 million. The Company also had negative cash flow from operations of approximately $35.1 million during the nine months ended September 30, 2017. The Company expects that it will likely need additional capital to further fund development of, and seek regulatory approvals for, its product candidates, and begin to commercialize any approved products. The Company is currently focused primarily on the development of immunotherapeutic treatments for cancers and debilitating viral infections using targeted cancer killing cell lines, and believes 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 the Company’s product candidates, if approved, fails to achieve market acceptance, the Company may never become profitable. Even if the Company achieves profitability in the future, it may not be able to sustain profitability in subsequent periods. The Company intends to cover its future operating expenses through cash and cash equivalents and marketable 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 the Company when needed and, if available, financing may not be obtained on terms favorable to the Company or its stockholders. While the Company expects its existing cash and cash equivalents and marketable securities will enable it to fund operations and capital expenditure requirements for at least the next twelve months, it may not have sufficient funds to reach commercialization. Failure to obtain adequate financing when needed may require the Company to delay, reduce, limit or terminate some or all of its development programs or future commercialization efforts or grant rights to develop and market product candidates that the Company might otherwise prefer to develop and market itself which could adversely affect the Company’s ability to operate as a going concern. If the Company raises additional funds from the issuance of equity securities, substantial dilution to existing stockholders may result. If the Company raises 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 the Company’s ability to operate its business.

Summary of Significant Accounting Policies

9 Months Ended

Sep. 30, 2017

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

With the exception of the policy for cost method investments noted below, there have been no significant changes to the items that the Company disclosed as its summary of significant accounting policies in the Annual Report on Form 10-K for the year ended December 31, 2016.

Accounting for Cost Method Investments

The Company owns non-marketable equity securities that are accounted for under the cost method because the preferred stock is not considered in-substance common stock and the 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 and the decline is determined to be other-than-temporary, 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 other-than-temporary decline in value has occurred include: market value of the investment based on most recent rounds of financing by the investee, length of time that the market value was below its cost basis, financial condition and business prospects of the investee, the Company’s intent and ability to retain the investment for a sufficient period of time to allow for recovery in market value of the investment, issues that raise concerns about the investee's ability to continue as a going concern, and any other information that the Company may be aware of related to the investment.

Use of Estimates

The preparation of condensed consolidated financial statements in conformity with accounting principles generally accepted in the United States of America 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 condensed consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. On an ongoing basis, the Company evaluates its estimates, including those related to stock-based compensation, warrants, the valuation allowance for deferred tax assets, preclinical and clinical trial accruals, impairment assessments, and the valuation of build-to-suit lease assets. The Company bases its estimates on historical experience and on various other market-specific and relevant assumptions that it believes to be reasonable under the circumstances. Actual results could differ from those estimates.

Basic and Diluted Net Loss per Share of Common Stock

Basic net loss per share is calculated by dividing 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 September 30,
	2017		2016
Outstanding options		5,693,250		6,518,062
Outstanding restricted stock units		1,066,993		859,022
Outstanding warrants		17,735,527		17,775,257
Total		24,495,770		25,152,341

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

Recent Accounting Pronouncements

Application of New or Revised Accounting Standards – Not Yet Adopted

In November 2016, the FASB issued ASU 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash. This guidance requires restricted cash and restricted cash equivalents to be included with the cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown in the consolidated statement of cash flows. ASU 2016-18 is effective for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. Early adoption is permitted, but the Company does not plan to adopt early. The evaluation of ASU 2016-18 has been completed and will not have a significant impact in the Company’s consolidated financial statements and disclosures.

In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. This new guidance is intended to present credit losses on available for sale debt securities as an allowance rather than as a write-down. ASU 2016-13 is effective for annual reporting periods, including interim periods within those annual periods, beginning after December 15, 2019, with early adoption permitted for those fiscal years beginning after December 15, 2018. Adoption of ASU 2016-13 is not expected to have a significant impact in the Company’s consolidated financial statements and disclosures.

In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842), which requires lessees to recognize assets and liabilities for operating leases with lease terms greater than twelve months in the balance sheet. The update also requires improved disclosures to help users of financial statements better understand the amount, timing and uncertainty of cash flows arising from leases. ASU 2016-02 is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years, with early adoption permitted. The Company is currently evaluating the impact of the adoption of ASU 2016-02 in its financial statements and disclosures. The adoption is expected to result in a significant increase in the total assets and liabilities reported in the Company’s consolidated balance sheet.

In January 2016, the FASB issued ASU 2016-01, Financial Instruments – Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities. This new guidance changes the recognition of the periodic revaluation of financial assets for fair value purposes from unrealized gains and losses in the equity section of the consolidated balance sheet to realized gains and losses in the consolidated statement of operations from the time of purchase through the final conversion back to cash. ASU 2016-01 is effective for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. Early adoption is not permitted. Adoption of ASU 2016-01 is not expected to have a significant impact in the Company’s consolidated financial statements and disclosures.

In May 2014, the FASB issued guidance codified in ASC Topic 606, ASU 2014-09, Revenue Recognition—Revenue from Contracts with Customers, which amends the guidance in former ASC Topic 605, Revenue Recognition, and was initially to be effective beginning January 1, 2017. On August 12, 2015, the FASB issued guidance which defers the effective date of ASC Topic 606 by one year to January 1, 2018 for public companies. 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. ASU 2014-09 defines a five-step process to achieve this core principle and, in doing so, it is possible more judgment and estimates may be required within the revenue recognition process than are required under existing GAAP, including identifying performance obligations in a contract, estimating the amount of variable consideration to include in the transaction price and allocating the transaction price to each separate performance obligation. The new standard allows for two methods of adoption: (1) full retrospective adoption, meaning the standard is applied to all periods presented, or (2) modified retrospective adoption, meaning the cumulative effect of applying the new standard is recognized as an adjustment to the opening retained earnings balance. The Company is in the process of finalizing its initial impact assessment and does not currently anticipate a material impact of the adoption of ASU 2014-09 on revenue in the condensed consolidated statements of operations. Changes to the Company’s accounting policies, business processes, internal controls and disclosures to support the new accounting are not expected to be significant.

Financial Statement Details

9 Months Ended

Sep. 30, 2017

Financial Statement Details [Abstract]

Financial Statement Details

3. Financial Statement Details

Prepaid Expenses and Other Current Assets

As of September 30, 2017 and December 31, 2016, prepaid expenses and other current assets consisted of (in thousands):

	September 30, 2017		December 31, 2016
	(Unaudited)
Prepaid services	$	1,037	$	1,191
Interest receivable - marketable securities		836		1,484
Prepaid insurance		816		531
Equipment and supply deposits		602		482
Tenant improvement allowance receivable		387		—
Prepaid rent		369		360
Prepaid license fees		192		462
Prepaid legal fees		—		350
Other		286		275
	$	4,525	$	5,135

Property, Plant and Equipment, Net

As of September 30, 2017 and December 31, 2016, property, plant and equipment consisted of (in thousands):

	September 30, 2017			December 31, 2016
	(Unaudited)
Construction in progress	$	41,025		$	6,939
Buildings		23,811			4,348
Equipment		9,104			5,458
Leasehold improvements		2,494			2,367
Software		1,082			769
Furniture & fixtures		233			203
		77,749			20,084
Accumulated depreciation		(3,278	)		(1,178	)
	$	74,471		$	18,906

Depreciation expense related to property, plant and equipment was $0.9 million and $0.3 million for the three months ended September 30, 2017 and 2016, respectively, and $2.3 million and $0.4 million for the nine months ended September 30, 2017 and 2016, respectively.

Construction in progress as of September 30, 2017 includes the estimated fair value of $5.1 million for the Company’s build-to-suit lease related to its facility in El Segundo, California, for which the Company is the “deemed owner” for accounting purposes only. See Note 8 – Build-to-suit Lease.

Buildings of $23.8 million are comprised of $19.5 million related to the purchased warehouse and distribution facility in El Segundo, California, originally accounted for as a capital lease (See Note 8 – Capital Lease) and $4.3 million under a financing lease representing the estimated fair market value of a building in Culver City, California, for which the Company is the “deemed owner” for accounting purposes only, and related non-normal tenant improvements. See Note 8 – Financing Lease Obligation.

Intangible Assets, Net

As of September 30, 2017 and December 31, 2016, intangible assets consisted of (in thousands):

	September 30, 2017			December 31, 2016
	(Unaudited)
Technology license	$	9,042		$	9,042
Less accumulated amortization		(5,651	)		(3,956	)
	$	3,391		$	5,086

Amortization expense was $0.6 million and $0.4 million for the three months ended September 30, 2017 and 2016, respectively, and $1.7 million and $1.3 million for the nine months ended September 30, 2017 and 2016, respectively. Amortization for the Company’s technology license is included in research and development expense in the condensed consolidated statement of operations.

Other Assets

As of September 30, 2017 and December 31, 2016, other assets consisted of (in thousands):

	September 30, 2017		December 31, 2016
	(Unaudited)
Restricted cash	$	179	$	179
Security deposits		127		137
Equipment not placed in service		—		362
Other		18		110
	$	324	$	788

Accrued Expenses

As of September 30, 2017 and December 31, 2016, accrued expenses consisted of (in thousands):

	September 30, 2017		December 31, 2016
	(Unaudited)
Accrued construction costs	$	11,068	$	1,053
Accrued bonus		1,434		1,732
Accrued compensation		992		898
Accrued professional and service fees		882		1,008
Accrued preclinical and clinical trial costs		651		662
Accrued laboratory equipment and supplies		393		190
Other		418		321
	$	15,838	$	5,864

Other Current Liabilities

As of September 30, 2017 and December 31, 2016, other current liabilities were made up of (in thousands):

	September 30, 2017		December 31, 2016
	(Unaudited)
Deferred rent - current portion	$	501	$	197
Build-to-suit lease liability - current portion		355		281
Financing obligation - current portion		276		253
Other		233		160
	$	1,365	$	891

Investment Income, Net

Net investment income includes interest income from all bank accounts as well as marketable securities, net realized gains or losses on sales of investments and the amortization of the premiums and discounts of the investments and is as follows for the three and nine months ended September 30, 2017 and 2016 (in thousands):

	Three Months Ended September 30,						Nine Months Ended September 30,
	(Unaudited)						(Unaudited)
	2017			2016			2017			2016
Interest income	$	1,005		$	1,371		$	3,408		$	3,802
Investment amortization accretion expense, net		(359	)		(625	)		(1,298	)		(1,567	)
Net realized gains on investments		34			49			30			67
	$	680		$	795		$	2,140		$	2,302

Interest income includes interest from the Company’s bank deposits. The Company did not recognize an impairment loss on any investments for the nine months ended September 30, 2017 and 2016.

Cost Method Investment	9 Months Ended
Cost Method Investment	Sep. 30, 2017
Investments All Other Investments [Abstract]
Cost Method Investment	4. Cost Method Investment In March 2017, the Company participated in a Series B convertible preferred stock financing and invested $8.5 million in Viracta Therapeutics, Inc. (Viracta), a clinical stage drug development company. The Company did not exercise the option to purchase up to an additional $8.5 million worth of shares of the Series B convertible preferred stock by September 30, 2017. In May 2017, the Company executed an exclusive worldwide license with Viracta to develop and commercialize Viracta’s proprietary histone deacetylase inhibitor drug candidate for use in combination with NK cell therapy and possibly additional therapies. See Note 7 for further information regarding the license. Based on the level of equity investment at risk, Viracta is not a Variable Interest Entity (VIE). The Company is not consolidating Viracta, but is accounting for this investment using the cost method because the preferred stock is not considered in-substance common stock and preferred stock does not have a readily determinable fair value. As of September 30, 2017, the Company did not estimate the fair value of this cost method investment as there were no events or changes in circumstances that may have had a significant adverse effect on the fair value of the investment. The $8.5 million cost of the investment is recorded in cost method investment in the condensed consolidated balance sheet as of September 30, 2017.

Cash Equivalents and Marketable Securities

9 Months Ended

Sep. 30, 2017

Cash Equivalents And Marketable Securities [Abstract]

Cash Equivalents and Marketable Securities

5. Cash Equivalents and Marketable Securities

As of September 30, 2017, all of the Company’s marketable securities are classified as available-for-sale and are scheduled to mature within 4.8 years. At September 30, 2017, the detail of the Company’s cash equivalents and marketable securities is as follows (in thousands):

	September 30, 2017
	(unaudited)
	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Current:
Commercial paper	$	5,145	$	1	$	—		$	5,146
Corporate debt securities		93,609		19		(58	)		93,570
Government sponsored securities		24,263		—		(28	)		24,235
Foreign government bonds		8,402		—		(6	)		8,396
Current portion		131,419		20		(92	)		131,347
Noncurrent:
Corporate debt securities		31,540		25		(109	)		31,456
Government sponsored securities		2,761		—		(19	)		2,742
Noncurrent portion		34,301		25		(128	)		34,198
Total	$	165,720	$	45	$	(220	)	$	165,545

At December 31, 2016, the detail of the Company’s cash equivalents and marketable securities is as follows (in thousands):

	December 31, 2016
	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Current:
Corporate debt securities	$	165,605	$	40	$	(76	)	$	165,569
Government sponsored securities		22,252		21		(1	)		22,272
Foreign government bonds		5,004		—		(2	)		5,002
Current portion		192,861		61		(79	)		192,843
Noncurrent:
Corporate debt securities		69,414		71		(290	)		69,195
Government sponsored securities		17,018		2		(38	)		16,982
Foreign government bonds		1,405		—		(11	)		1,394
Noncurrent portion		87,837		73		(339	)		87,571
Total	$	280,698	$	134	$	(418	)	$	280,414

Included in corporate debt securities is $2.0 million of cash equivalents at December 31, 2016.

Available-for-sale investments that had been in an unrealized loss position for more and less than 12 months at September 30, 2017 and December 31, 2016 are as follows (in thousands):

	September 30, 2017
	(unaudited)
	Less than 12 months					More than 12 months
	Estimated Fair Value		Gross Unrealized Losses			Estimated Fair Value		Gross Unrealized Losses
Corporate debt securities	$	76,280	$	(130	)	$	10,892	$	(36	)
Government sponsored securities		26,978		(47	)		—		—
Foreign government bonds		7,000		(1	)		1,397		(6	)
Total	$	110,258	$	(178	)	$	12,289	$	(42	)

	December 31, 2016
	Less than 12 months					More than 12 months
	Estimated Fair Value		Gross Unrealized Losses			Estimated Fair Value		Gross Unrealized Losses
Corporate debt securities	$	17,204	$	(39	)	$	—	$	—
Government sponsored securities		150,320		(366	)		—		—
Foreign government bonds		6,396		(13	)		—		—
Total	$	173,920	$	(418	)	$	—	$	—

The Company evaluated its securities for other-than-temporary impairment and concluded that the decline in value was primarily caused by current economic and market conditions. The Company does not intend to sell the investments and it is not more likely than not that the Company will be required to sell the investments before recovery of their amortized cost bases. Therefore, the Company did not have any other-than-temporary impairment loss during the nine months ended September 30, 2017. At September 30, 2017, 57 of the securities and bonds are in an unrealized loss position.

The Company recorded realized gains and losses on sales or maturities of available-for-sale securities as follows (in thousands):

	Three Months Ended September 30,						Nine Months Ended September 30,
	(unaudited)						(unaudited)
	2017			2016			2017			2016
Gross realized gains	$	43		$	51		$	45		$	143
Gross realized losses		(9	)		(2	)		(15	)		(76	)
Net realized gains	$	34		$	49		$	30		$	67

Fair Value Measurements

9 Months Ended

Sep. 30, 2017

Fair Value Disclosures [Abstract]

Fair Value Measurements

6. Fair Value Measurements

Recurring Valuations

In accordance with the authoritative guidance for financial assets and liabilities measured at fair value on a recurring basis (ASC Topic 820), the Company prioritizes the inputs used to measure fair value from market-based assumptions to entity specific assumptions as follows:

•

Level 1—Inputs based on quoted market prices for identical assets or liabilities in active markets at the measurement date.

•

Level 2—Observable inputs other than quoted prices in Level 1, such as quoted prices for similar assets and liabilities in active markets; quoted prices for identical or similar assets and liabilities in markets that are not active; or other inputs that are observable or can be corroborated by observable market data.

•

Level 3—Inputs which reflect management’s best estimate of what market participants would use in pricing the asset or liability at the measurement date. The inputs are unobservable in the market and significant to the instruments valuation.

The following tables present the Company’s hierarchy for its assets measured at fair value on a recurring basis as of September 30, 2017 and December 31, 2016 (in thousands):

	Fair Value Measurements at September 30, 2017
	(unaudited)
	Total		Level 1		Level 2		Level 3
Assets:
Current:
Commercial paper	$	5,146	$	—	$	5,146	$	—
Corporate debt securities		93,570		—		93,570		—
Government sponsored securities		24,235		—		24,235		—
Foreign government bonds		8,396		—		8,396		—
Noncurrent:
Corporate debt securities		31,456		—		31,456		—
Government sponsored securities		2,742		—		2,742		—
Total assets measured at fair value	$	165,545	$	—	$	165,545	$	—

The table above excludes $20.9 million in depository institutions that are classified as Level 1 assets.

	Fair Value Measurements at December 31, 2016
	Total		Level 1		Level 2		Level 3
Assets:
Current:
Cash and cash equivalents*	$	2,005	$	—	$	2,005	$	—
Corporate debt securities		163,564		—		163,564		—
Government sponsored securities		22,272		—		22,272		—
Foreign government bonds		5,002		—		5,002		—
Noncurrent:
Corporate debt securities		69,195		—		69,195		—
Government sponsored securities		16,982		—		16,982
Foreign government bonds		1,394		—		1,394		—
Total assets measured at fair value	$	280,414	$	—	$	280,414	$	—

*This amount excludes $6.1 million in depository institutions that are classified as Level 1 assets.

Non-recurring Valuation

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 nine months ended September 30, 2017.

Collaboration and License Agreements	9 Months Ended
Collaboration and License Agreements	Sep. 30, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Collaboration and License Agreements	7. Collaboration and License Agreements Collaborative Arrangement 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. Exclusive Co-Development Agreement In August 2016, the Company entered into an exclusive Co-Development Agreement (the Co-Development Agreement) with Altor BioScience Corporation (Altor), a related party (Note 9). Under the Co-Development Agreement, the Company and Altor agreed to exclusively collaborate on the development of therapeutic applications combining the Company’s proprietary natural killer cells with Altor's ALT-801 and/or ALT-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. The Company will be 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 grant 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 (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, the Company shall be 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 will supply free of charge sufficient amounts of Altor products for all pre-clinical requirements and all 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. Altor and the Company each will own 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. During the nine months ended September 30, 2017, the Company has dosed several patients with ALT-803 in its Phase II Merkel Cell Carcinoma trial. No charges for supplies or milestones by Altor have been incurred in association with the above trial during the nine months ended September 30, 2017. Royalties and In-licensing Agreement Viracta License Agreement In May 2017, the Company entered into an agreement with Viracta to grant the Company exclusive world-wide rights to Viracta’s Phase II drug candidate, VRx-3996, for use in combination with the Company’s platform of natural killer cell therapies. In consideration for the license, the Company is 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. The Company 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 (GSH) and DRK-Blutspendedienst Baden-Wurttemberg-Hessen gGmbH (BSD) License Agreement In August 2015, the Company entered into a license agreement with GSH and BSD under which the Company was granted an exclusive license to certain GSH-BSD patents, materials and know-how that specifically targets ErbB2 expressing cancers. In addition, GSH granted the Company an exclusive license to certain GSH only technology and materials. In consideration for the licenses, the Company agreed to pay initial and annual licensing fees, regulatory and commercial milestones and low single-digit percentage royalties on net sales of licensed products. The royalty term shall continue in a particular country until the later of (i) the expiration of the valid patent claims in such country, or (ii) a specified period of time after the first commercial sale of licensed product in such country. The license agreement shall continue until no further payments are due at which time the licenses and rights will continue on a non-exclusive, royalty-free basis. The license agreement can be terminated earlier: (i) for material breach by either party after 60 days cure period, (ii) if the Company declares bankruptcy or insolvency, (iii) by the Company in its sole discretion upon 60 days prior written notice. Annual license fees under the agreement begin in 2018. During the third quarter of 2017, GSH reached the first regulatory milestone of a receipt of the first Institutional Review Board (IRB) approval for the Phase I Glioblastoma Study. The Company expensed $0.9 million for the first milestone payment under the agreement, which is included in research and development expenses in the condensed consolidated statements of operations for the three and nine months ended September 30, 2017.

Commitment and Contingencies	9 Months Ended
Commitment and Contingencies	Sep. 30, 2017
Commitments And Contingencies Disclosure [Abstract]
Commitments and contingencies	8. Commitments and Contingencies Contingencies The Company records accruals for loss contingencies to the extent that the Company concludes it is probable that a liability has been incurred and the amount of the related loss can be reasonably estimated. The Company evaluates, 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. Appeal of USPTO Decision In March 2009, the Company received a final rejection in one of the Company’s original patent applications pertaining to certain limited methods of use claims for NK-92 from the U.S. Patent and Trademark Office (the USPTO), but the USPTO allowed claims on all of the other proposed claims, including other methods of use. The Company appealed this decision with the USPTO Board of Appeals and, in the fall of 2013, the Board of Appeals reversed the Examiner’s rejection of the claim to certain limited methods of use with NK-92, but affirmed the Examiner’s rejection of the remaining patent claims. In December 2013, the Company brought an action in the U.S. District Court for the Eastern District of Virginia to review the decision of the USPTO as the Company disagreed with the decision as to the certain limited non-allowed claims. On September 2, 2015, the U.S. District Court granted the USPTO’s motion for summary judgment. On September 24, 2015, the Company filed a notice of appeal to the United States Court of Appeals for the Federal Circuit. In September 2015, the USPTO filed a Motion for Expenses seeking $0.1 million for attorney’s fees and the USPTO’s expert witness fees. In February 2016, the U.S. District Court denied the USPTO’s Motion for Expenses for attorney’s fees and granted Director’s Motion for Expenses for the USPTO’s expert witness fees. The USPTO filed a notice of appeal on April 5, 2016. In May 2017, the Federal Circuit affirmed the U.S. District Court’s summary judgement ruling. The formal mandate was issued on June 26, 2017. In June 2017, the Federal Circuit reversed the U.S. District Court and remanded the case for the U.S. District Court to enter an award of $0.1 million in favor of the USPTO. On August 31, 2017, a majority of active Federal Circuit judges voted to vacate the June 2017 decision and hear the case en banc sua sponte. The USPTO’s opening en banc brief is due on November 15, 2017. Based on the information available at present, the Company cannot reasonably estimate a range of loss for this action beyond the attorney and expert witness fees. Accordingly, the awarded fees have been accrued, but no liability associated with this action beyond the fees has been accrued. The Company is expensing legal costs associated with defending this litigation as the costs are incurred. 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 have been consolidated. Plaintiffs assert 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 seek 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. No trial date has been set. Management intends to vigorously defend these proceedings. At this time, the Company cannot predict how the Court will rule on the merits of the claims and/or the scope of the potential loss in the event of an adverse outcome. Therefore, based on the information available at present, the Company cannot reasonably estimate a range of loss for this action. Should the Company ultimately be found liable, the liability could have a material adverse effect on the Company’s results of operations for the period or periods in which it is incurred. On September 6, 2016, a putative shareholder derivative complaint captioned Bushansky v. Soon-Shiong, et al., No. 37-2016-00030867-CU-SL-CTL was filed in California Superior Court, San Diego County also related to the Company’s restatement of certain interim financial statements. The complaint named as defendants the Company’s directors and outside auditor at the time of the IPO. The Company is named solely as a nominal defendant. The complaint alleges the directors breached their fiduciary duties to the Company and wasted corporate assets, and that the outside auditors committed malpractice. The complaint seeks, on behalf of the Company, unspecified damages, the return of directors’ salaries for unspecified periods, and injunctive relief. At this time, the Company cannot predict how the Court will rule on the merits of the claims and/or the scope of the potential loss in the event of an adverse outcome. In April 2017, the court entered a written order of dismissal after granting the Company’s motion to dismiss the California complaint based on a corporate charter provision specifying a Delaware forum. Plaintiffs have filed a notice of appeal. Should the Company ultimately be found liable, the liability could have a material adverse effect on the Company’s results of operations for the period or periods in which it is incurred. On October 30, 2017, a putative stockholder derivative complaint captioned Mudd v. Soon-Shiong, et al., C.A. No. 2017-0774-JTL was filed in the Delaware Court of Chancery. The complaint asserts that various of the Company's current and former directors and officers breached their fiduciary duties to the Company based on factual allegations similar to those in the Sudunagunta and Bushansky actions. The complaint seeks damages and other relief on behalf of the Company, which is named solely as a nominal defendant. At this time, the Company cannot predict how the Court will rule on the merits of the claims and/or the scope of the potential loss in the event of an adverse outcome. Therefore, based on the information available at present, the Company cannot reasonably estimate a range of loss for this action. Should the Company ultimately be found liable, the liability could have a material adverse effect on the Company’s results of operations for the period or periods in which it is incurred. Contractual Obligations - Leases The Company leases: (i) office space in Cardiff-by-the-Sea, California; (ii) a research facility in Woburn, Massachusetts; (iii) office space in Cary, North Carolina; (iv) a research facility and office space in San Diego, California; (v) research and manufacturing space in Culver City, California, from a related party (Note 9); (vi) a research and manufacturing facility in El Segundo, California, also from a related party (Note 9); and (vii) a warehouse and distribution facility in El Segundo, California. The Company recognizes rent expense under its operating leases on a straight-line basis. Rent expense for the three months ended September 30, 2017 and 2016 was $0.6 million and $0.8 million, respectively, and $2.0 million and $2.2 million for the nine months ended September 30, 2017 and 2016, respectively. Capital Lease In April 2017, the Company entered into an agreement to purchase a commercial building with approximately 36,000 square feet, located in El Segundo, California. The Company intends to use this facility as a warehouse and distribution facility as it is adjacent to the El Segundo, California, research and manufacturing facility. Upon the execution of the purchase agreement, the Company made a deposit of $5.0 million to the escrow holder and entered into a lease agreement related to this facility commencing on May 1, 2017. There was no monthly base rent under the lease. The escrow closed in September 2017 and the Company paid the remaining purchase price, including closing costs, of $15.3 million and terminated the lease agreement. The Company had a bargain purchase option to purchase the building upon termination of the escrow period and, initially, accounted for the lease as a capital lease. Upon purchase of the building in September 2017, which resulted in the termination of the capital lease, the Company accounted for the transaction as a single transaction and the carrying amount of the asset was adjusted for any differences between the carrying amount of the lease obligation and the initial carrying amount of the asset. Build-to-suit Lease In September 2016, the Company 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 is to be converted to a research and development laboratory and a Good Manufacturing Practices (GMP) laboratory. The lease runs from July 2016 through July 2023. The Company has 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. During the construction period, the Company records the rent payments as (1) a reduction of the build-to-suit lease liability; (2) deferred rent; and (3) rent expense on the imputed cost to lease the underlying land of the facility, which is considered an operating lease. For the three months ended September 30, 2017 and 2016, the Company recorded $0.1 million and $0.1 million in rent expense, respectively, and $0.2 million and $0.1 million in rent expense, respectively, for the nine months ended September 30, 2017 and 2016, which is recorded in research and development expense in the condensed consolidated statement of operations. The Company is responsible for costs to build out the laboratory and has incurred costs of approximately $29.1 million as of September 30, 2017, which is reflected in construction in progress as part of property, plant and equipment, net in the condensed consolidated balance sheet. Additionally, in order for the facility to meet the Company's research and development and GMP laboratory specifications, the Company started to make certain structural changes to the facility as part of the conversion to laboratory space. As a result of these changes, the Company concluded that it is the “deemed owner” of the building (for accounting purposes only) during the construction period. Accordingly, the Company recorded a non-cash build-to-suit lease asset of $5.1 million, representing its estimate of the fair market value of the building, and a corresponding construction build-to-suit lease liability, recorded as a component of other current and non-current liabilities in the condensed consolidated balance sheet as of September 30, 2017. Upon completion of construction of this facility, the Company evaluates the de-recognition of the asset and liability under the provisions of ASC 840-40 Leases - Sale-Leaseback Transactions. However, if the Company does not comply with the provisions needed for sale-leaseback accounting, the lease will be accounted for as a financing obligation and lease payments will be attributed to (1) a reduction of the principal financing obligation; (2) imputed interest expense; and (3) land lease expense (which is considered an operating lease and a component of research and development expenses) representing an imputed cost to lease the underlying land of the facility. In addition, the underlying building asset will be depreciated over the building's estimated useful life which is estimated at 39 years. And at the conclusion of the lease term, the Company would de-recognize both the net book values of the asset and financing obligation. Financing Lease Obligation In November 2015, the Company entered into a facility license agreement with NantWorks LLC (NantWorks) (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 GMP laboratory. The license was effective in May 2015 and extends through December 2020. The Company has the option to extend the license through December 2023. The monthly license fee is $47,000 with annual increases of 3% beginning in January 2017. The Company records the rent payments as (1) a reduction of the financing obligation; (2) imputed interest expense; and (3) rent expense on the imputed cost to lease the underlying land of the facility, which is considered an operating lease. For the three months ended September 30, 2017 and 2016, the Company recorded $47,000 and $0.1 million, respectively, and $0.1 million and $0.3 million for the nine months ended September 30, 2017 and 2016, respectively, in rent expense, which is reflected in research and development expense in the condensed consolidated statement of operations. Under the facility license agreement, the Company was responsible for costs to build out the laboratory and incurred costs of approximately $3.5 million. The Company concluded that it was the “deemed owner” of the building (for accounting purposes only) during the construction period. The Company recorded the build out costs as an asset with a corresponding build-to-suit liability, which was recorded as a component of other current and non-current liabilities in the condensed consolidated balance sheet while the building was under construction. Upon completion of construction of this building in August 2016, the Company evaluated the de-recognition of the asset and liability under the provisions of ASC 840-40, Leases – Sale-Leaseback Transactions. The Company determined that the lease does not meet the criteria for sale-leaseback accounting treatment, due to the continuing involvement in the project resulting from the significant collateral the Company provided to the landlord in the form of building improvements. As a result, the building is being accounted for as a financing obligation. The underlying assets of $4.3 million are depreciated over the building’s estimated useful life, which is 39 years. At the conclusion of the lease term, the Company will de-recognize both the net book values of the assets and financing obligation. Commitments The Company did not enter into any significant contracts during the nine months ended September 30, 2017 other than those disclosed in this document.

Related Party Agreements	9 Months Ended
Related Party Agreements	Sep. 30, 2017
Related Party Transactions [Abstract]
Related Party Agreements	9. Related Party Agreements The Company’s 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, the Company has entered into arrangements with NantWorks and certain affiliates of NantWorks to facilitate the development of new genetically modified NK cells for the Company’s product pipeline. John Lee, M.D. and Leonard Sender, M.D., Inc., a professional medical corporation, dba Chan Soon-Shiong Institutes for Medicine (CSSIM) In July 2017, the Company entered into an agreement with John Lee, M.D. and Leonard Sender, M.D., Inc., a professional medical corporation, dba Chan Soon-Shiong Institutes for Medicine (CSSIM), in El Segundo, California. CSSIM is a related party as it is owned by two officers of the Company and NantWorks provides administrative services to CSSIM. One of the Company’s officers is the principal investigator for the trial on behalf of CSSIM. The clinical trial is an open-label, Phase I study of haNK for infusion in subjects with metastatic or locally advanced solid tumors. During the three and nine months ended September 30, 2017 estimated expense of $36,000 has been recognized in research and development expense in the condensed consolidated statement of operations and accrued expense in the condensed consolidated balance sheet. Tensorcom, Inc. In April 2017, the Company entered into a sublease agreement with Tensorcom, Inc. (Tensorcom) related to its San Diego, California, research and development laboratory and office space, with an initial lease from May 1, 2017 through April 30, 2018. The Company’s Chairman and CEO indirectly owns all of the outstanding equity of Tensorcom. The sublease agreement converts to a month-to-month lease after the initial lease term, not to exceed the expiration of the lease agreement between the Company and the third party landlord. After the initial term, the sublease agreement can be terminated by either party by providing a thirty day written notice. The sublease includes a portion of the premises consisting of approximately 6,557 rentable square feet of space. The monthly base rent is $25,000 per month, with an annual 3% increase. For the three and nine months ended September 30, 2017, the Company recognized $0.1 million and $0.1 million, respectively, in other income in the condensed consolidated statement of operations under the sublease agreement. At September 30, 2017, there was no balance due between the parties. VivaBioCell S.p.A. In February 2017, the Company entered into a research grant agreement with VivaBioCell S.p.A. (VBC), an affiliated company of NantWorks, under which VBC will conduct research and development activities related to the Company’s NK cell lines using VBC’s proprietary technology. The Company paid $0.6 million to VBC, which is recorded in prepaid expenses and other current assets in the condensed consolidated balance sheet, and expects to benefit from the research and development activities over a one year timeframe. For the three and nine months ended September 30, 2017, $0.2 million and $0.4 million, respectively, has been recognized in research and development expense in the condensed consolidated statement of operations and prepaid expenses and other current assets in the condensed consolidated balance sheet has been reduced by that amount. 605 Doug St. LLC In September 2016, the Company entered into a lease agreement with 605 Doug St. LLC, an entity owned by the Company’s Chairman and CEO, for approximately 24,250 square feet in El Segundo, California, which is to be converted to a research and development laboratory and a GMP laboratory. The lease runs from July 2016 through July 2023. The Company has 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. See Note 8 – Build-to-suit Lease for further details on this lease. For the three months ended September 30, 2017 and 2016, the Company recorded rent expense of $0.1 million and $0.1 million, respectively, and $0.2 million and $0.1 million, respectively, for the nine months ended September 30, 2017 and 2016, which is reflected in research and development expense in the condensed consolidated statement of operations. At September 30, 2017, there is no balance due between the parties. Altor In August 2016, the Company entered into a Co-Development Agreement with Altor as described in Note 7. The Company’s Chairman and CEO is also the Chairman of Altor. Altor is a wholly owned subsidiary of NantCell Inc. (NantCell), and the Company’s Chairman and CEO is also the Chairman and CEO of NantCell and holds a greater than 20% ownership interest in NantCell. No charges for supplies or milestones by Altor have been incurred in association with the above trial during the three and nine months ended September 30, 2017. NantBio, Inc. In March 2016, NantBio, Inc. (NantBio), a NantWorks company, and the National Cancer Institute entered into a cooperative research and development agreement. The agreement covers NantBio and its affiliates, including the Company. Under the agreement, the parties will collaborate on the preclinical and clinical development of proprietary recombinant NK cells and monoclonal antibodies in monotherapy and in combination immunotherapies. The Company expects to benefit from the preclinical and clinical research conducted during the first and second year under this agreement and is providing the first and second year funding under the five-year agreement. In both April 2016 and April 2017, the Company paid $0.6 million to the National Cancer Institute as a prepayment for the first and second year of funding. The Company recognizes research and development expense ratably over a 12-month period for each funding year and recorded $0.2 million and $0.1 million of expense for the three months ended September 30, 2017 and 2016, respectively, and $0.5 million and $0.3 million for the nine months ended September 30, 2017 and 2016, respectively. NantWorks 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, and the Company is charged for the services at cost plus reasonable allocations for indirect costs that relate to the employees providing the services. For the three months ended September 30, 2017 and 2016, the Company recorded selling, general and administrative expense of $0.7 million and $0.8 million, respectively, and $2.0 million and $2.3 million for the nine months ended September 30, 2017 and 2016, respectively. For the three months ended September 30, 2017 and 2016, the Company recorded research and development expense of $0.6 million and $0.4 million, respectively, and $2.1 million and $1.2 million for the nine months ended September 30, 2017 and 2016, respectively, under this arrangement in the condensed consolidated statement of operations. In June 2016, the Company amended the existing shared services agreement with NantWorks whereby the Company can provide such support services to NantWorks and/or any of its affiliates. For the three months ended September 30, 2017 and 2016, the Company recorded selling, general and administrative expense reimbursements of $0 and $17,000, respectively, and $0.2 million and $26,000 for the nine months ended September 30, 2017 and 2016, respectively. For the three months ended September 30, 2017 and 2016, the Company recorded research and development expense reimbursements of $0.3 million and $0.1 million, respectively, and $0.6 million and $0.1 million for the nine months ended September 30, 2017 and 2016, respectively. The Company owed NantWorks a net amount of $1.9 million for all agreements between the two affiliates at September 30, 2017, which is included in due to related parties in the condensed consolidated balance sheet. In November 2015, the Company 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 GMP laboratory. See Note 8 - Financing Lease Obligation for further details on this lease. For the three months ended September 30, 2017 and 2016, the Company recorded rent expense of $47,000 and $0.1 million, respectively, and $0.1 million and $0.3 million for the nine months ended September 30, 2017 and 2016, respectively, which is reflected in research and development expense in the condensed consolidated statement of operations. NantOmics, LLC In June 2015, the Company entered into an agreement with NantOmics, LLC (NantOmics) to obtain genomic sequencing and proteomic analysis services, as well as related data management and bioinformatics services, exclusively from NantOmics. The Company is 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 three months ended September 30, 2017 and 2016, the Company recorded operating expense of $0 and $0.1 million, respectively, and $13,000 and $0.2 million for the nine months ended September 30, 2017 and 2016, respectively, under the agreement to research and development expense in the condensed consolidated statement of operations. At September 30, 2017, there is no balance due between the parties. NantCell In June 2015, the Company also entered into a supply agreement with NantCell pursuant to which the Company has the right to purchase NantCell’s proprietary bioreactors, made according to specifications mutually agreed to with NantCell. The agreement has an initial term of five years and renews automatically for successive one year periods unless terminated earlier. During the three months ended September 30, 2017, the Company ordered and partially received bioreactors, resulting in $0.3 million in capitalized equipment and $0.1 million in payable to related parties for the units received in the condensed consolidated balance sheet as of September 30, 2017. Under the same agreement, the Company also has the right to purchase reagents and consumables associated with such equipment from NantCell. During the three months ended September 30, 2017, the Company paid a deposit of $0.1 million for the consumables, which was recorded in prepaid expenses and other current assets in the condensed consolidated balance sheet. During the three and nine months ended September 30, 2017, the Company recorded research and development expense of $0 and $0.3 million, respectively, in the condensed consolidated statement of operations. No expense was recorded during the three and nine months ended September 30, 2016.

Stockholders' Equity	9 Months Ended
Stockholders' Equity	Sep. 30, 2017
Equity [Abstract]
Stockholders' Equity	10. Stockholders’ Equity Stock Repurchase—In November 2015, the board of directors approved a share repurchase program (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 the Company’s outstanding shares of common stock, exclusive of any commissions, markups or expenses. The timing and amounts of any purchases will 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. The Company expects to finance the purchases with existing cash balances. During the three and nine months ended September 30, 2017, the Company repurchased 0 and 3,072,209 shares of its common stock, respectively, at prices ranging between $3.10 and $4.75 per share for a total of $12.5 million, including $0.1 million of broker commissions on the repurchases. During the year ended December 31, 2016, the Company repurchased 2,157,944 shares of common stock for a total of $15.8 million. The shares are formally retired through board approval upon repurchase. The Company accounted for the repurchases under the constructive retirement method and allocated the excess of the repurchase price over par value to accumulated deficit. At September 30, 2017, $21.8 million remained authorized for repurchase under the Company’s 2015 Share Repurchase Program and no shares were repurchased during the three months ended September 30, 2017.

Stock-Based Compensation

9 Months Ended

Sep. 30, 2017

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation

11. Stock-Based Compensation

The following table presents stock-based compensation expense included in the Company’s condensed consolidated statement of operations (in thousands):

	Three Months Ended September 30,					Nine Months Ended September 30,
	(unaudited)					(unaudited)
	2017			2016		2017		2016
Stock-based compensation expense:
Warrants for common stock to an officer	$	7,635		$	14,171	$	23,948	$	41,443
Employee stock options		978			3,075		3,281		12,826
Employee restricted stock units		298			1,321		523		7,851
Non-employee restricted stock units		(197	)		102		361		466
	$	8,714		$	18,669	$	28,113	$	62,586
Stock-based compensation expense in operating expenses:
Research and development	$	(3	)	$	116	$	40	$	680
Selling, general and administrative		8,717			18,553		28,073		61,906
	$	8,714		$	18,669	$	28,113	$	62,586

In the third quarter of 2017, the Company early adopted ASU 2017-09, Compensation – Stock Compensation (Topic 718): Scope of Modification Accounting. This guidance determines which changes to the terms and conditions of share-based payment awards require an entity to apply modification accounting. The adoption of this guidance had no impact to the Company’s condensed consolidated financial statements.

In the second quarter of 2016, the Company adopted ASU 2016-09, Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting. ASU 2016-09 requires that certain other amendments relevant to the Company be applied using a modified-retrospective transition method by means of a cumulative-effect adjustment to accumulated deficit as of the beginning of the period in which the guidance is adopted. As a result of adopting ASU 2016-09 during the three months ended June 30, 2016, the Company adjusted accumulated deficit for amendments related to an entity-wide accounting policy election to recognize share-based award forfeitures only as they occur rather than an estimate by applying a forfeiture rate. The Company recorded a $31,000 charge to accumulated deficit as of January 1, 2016 and an associated charge to additional paid-in capital for previously unrecognized stock compensation expense as a result of applying this policy election. The Company also recorded $27,000 in additional stock compensation expense for the three months ended March 31, 2016 as a result of applying this policy election.

ASU 2016-09 also requires the recognition of the income tax effects of awards in the condensed consolidated statement of operations when the awards vest or are settled, thus eliminating addition paid-in capital pools. The Company elected to adopt the amendments related to the presentation of excess tax benefits in the condensed consolidated statement of cash flows using a prospective transition method.

Stock Options

The following table summarizes stock option activity for the nine months ended September 30, 2017 (in thousands, except for share and year amounts):

	Number of Shares			Weighted- Average Exercise Price		Aggregate Intrinsic Value		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 September 30, 2017		5,693,250		$	7.71	$	16,076		5.5
Vested and Exercisable at September 30, 2017		4,998,937		$	8.47	$	13,173		6.1

The aggregate intrinsic value of stock options exercised during the nine months ended September 30, 2017 was $1.7 million.

The total unrecognized stock-based compensation expense related to non-vested stock options as of September 30, 2017 is $5.8 million, which is expected to be recognized over a weighted-average period of 1.5 years.

Restricted Stock Units

The following table summarizes the activity for restricted stock units:

	Number of Restricted Stock Units Outstanding			Weighted-Average Grant Date Fair Value
Unvested balance at December 31, 2016		814,456		$	13.98
Granted		563,483		$	4.53
Vested		(35,793	)	$	8.21
Forfeited		(275,153	)	$	10.51
Unvested balance at September 30, 2017		1,066,993		$	10.08

During the nine months ended September 30, 2017, the Company granted 486,233 shares of restricted stock units to employees and 77,250 shares to non-employees. Of the 77,250 shares granted to non-employees, 27,250 shares were granted to employees of related companies under the Company’s shared services agreement with NantWorks (Note 9).

As of September 30, 2017, there was $4.7 million of unrecognized stock-based compensation expense related to restricted stock units that is expected to be recognized over a weighted-average period of 2.9 years. Of that amount, $3.4 million of unrecognized expense is related to employee grants with a weighted-average period of 3.0 years and $1.3 million of unrecognized expense is related to non-employee grants with a weighted-average period of 2.6 years that is impacted by periodic mark-to-market adjustments.

Warrants

The following table summarizes the warrant activity for the nine months ended September 30, 2017:

Outstanding at December 31, 2016	17,768,314
Warrants exercised	(32,787	)
Outstanding at September 30, 2017	17,735,527
Vested and exercisable at September 30, 2017	15,884,027

The total unrecognized stock-based compensation expense related to non-vested warrants as of September 30, 2017 is $25.5 million, which is expected to be recognized over a weighted-average period of 0.8 years.

Income Taxes	9 Months Ended
Income Taxes	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Income Taxes	12. Income Taxes The difference between the federal statutory tax rate of 34% and the Company’s 0% tax rate is due to losses in jurisdictions from which the Company cannot benefit. Intraperiod tax allocation rules require the Company to allocate the provision for income taxes between continuing operations and other categories of earnings, such as other comprehensive income. In periods in which the Company has a year-to-date pre-tax loss from continuing operations and pre-tax income in other categories of earnings, such as other comprehensive income, the Company must allocate the tax provision to the other categories of earnings. The Company then records a related tax benefit in continuing operations. During the nine months ended September 30, 2017, the Company recorded unrealized gains on its marketable securities in other comprehensive income, net of taxes. As a result, the Company recorded a tax benefit of $13,000 and tax expense of $39,000 for the three months ended September 30, 2017 and 2016, respectively, and tax expense of $23,000 and $0.1 million for the nine months ended September 30, 2017 and 2016, respectively, in the condensed consolidated statement of operations. The Company also recorded other comprehensive income of $15,000 and other comprehensive loss of $0.2 million for the three months ended September 30, 2017 and 2016, respectively, and income of $43,000 and $0.2 million for the nine months ended September 30, 2017 and 2016, respectively, in the condensed consolidated balance sheet. The Company is operating in Korea. During the three months ended September 30, 2017 and 2016, the tax benefit related to Korea is $0.1 million for each period. During the nine months ended September 30, 2017 and 2016, the tax benefit related to Korea is $0.3 million for each period. The Company currently files federal and state income tax returns in the United States and in Korea. Income tax expense consists of U.S. federal, state, and Korean income taxes. To date, the Company has not been required to pay U.S. federal, state, and Korean income taxes because of current and accumulated net operating losses.

Subsequent Events	9 Months Ended
Subsequent Events	Sep. 30, 2017
Subsequent Events [Abstract]
Subsequent Events	13. Subsequent Events Related Party Agreement In November 2017, the Company entered into an agreement with John Lee, M.D. and Leonard Sender, M.D., Inc., a professional medical corporation, dba Chan Soon-Shiong Institutes for Medicine (CSSIM), in El Segundo, California. CSSIM is a related party as it is owned by two officers of the Company and NantWorks provides administrative services to CSSIM. One of the Company’s officers will be the principal investigator for the trial on behalf of CSSIM. The clinical trial is a Phase Ib study, combination immunotherapy with haNK therapy in subjects with pancreatic cancer who have progressed on or after standard-of-care therapy. The cost under this agreement is estimated at $7.1 million.

Summary of Significant Accounting Policies (Policies)

9 Months Ended

Sep. 30, 2017

Accounting Policies [Abstract]

Principles of Consolidation

The Company’s condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries, Inex Bio, Inc. and 557 Doug St, LLC, and have been prepared in accordance with GAAP. All intercompany amounts have been eliminated.

Liquidity

As of September 30, 2017, the Company had an accumulated deficit of approximately $471.5 million. The Company also had negative cash flow from operations of approximately $35.1 million during the nine months ended September 30, 2017. The Company expects that it will likely need additional capital to further fund development of, and seek regulatory approvals for, its product candidates, and begin to commercialize any approved products.

The Company is currently focused primarily on the development of immunotherapeutic treatments for cancers and debilitating viral infections using targeted cancer killing cell lines, and believes 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 the Company’s product candidates, if approved, fails to achieve market acceptance, the Company may never become profitable. Even if the Company achieves profitability in the future, it may not be able to sustain profitability in subsequent periods. The Company intends to cover its future operating expenses through cash and cash equivalents and marketable 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 the Company when needed and, if available, financing may not be obtained on terms favorable to the Company or its stockholders.

While the Company expects its existing cash and cash equivalents and marketable securities will enable it to fund operations and capital expenditure requirements for at least the next twelve months, it may not have sufficient funds to reach commercialization. Failure to obtain adequate financing when needed may require the Company to delay, reduce, limit or terminate some or all of its development programs or future commercialization efforts or grant rights to develop and market product candidates that the Company might otherwise prefer to develop and market itself which could adversely affect the Company’s ability to operate as a going concern. If the Company raises additional funds from the issuance of equity securities, substantial dilution to existing stockholders may result. If the Company raises 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 the Company’s ability to operate its business.

Accounting for Cost Method Investments

Use of Estimates

Basic and Diluted Net Loss Per Share of Common Stock

Basic and Diluted Net Loss per Share of Common Stock

	As of September 30,
	2017		2016
Outstanding options		5,693,250		6,518,062
Outstanding restricted stock units		1,066,993		859,022
Outstanding warrants		17,735,527		17,775,257
Total		24,495,770		25,152,341

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

Recent Accounting Pronouncements

Application of New or Revised Accounting Standards – Not Yet Adopted

Summary of Significant Accounting Policies (Tables)

9 Months Ended

Sep. 30, 2017

Accounting Policies [Abstract]

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 September 30,
	2017		2016
Outstanding options		5,693,250		6,518,062
Outstanding restricted stock units		1,066,993		859,022
Outstanding warrants		17,735,527		17,775,257
Total		24,495,770		25,152,341

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

Financial Statement Details (Tables)

9 Months Ended

Sep. 30, 2017

Financial Statement Details [Abstract]

Prepaid Expenses and Other Current Assets

As of September 30, 2017 and December 31, 2016, prepaid expenses and other current assets consisted of (in thousands):

	September 30, 2017		December 31, 2016
	(Unaudited)
Prepaid services	$	1,037	$	1,191
Interest receivable - marketable securities		836		1,484
Prepaid insurance		816		531
Equipment and supply deposits		602		482
Tenant improvement allowance receivable		387		—
Prepaid rent		369		360
Prepaid license fees		192		462
Prepaid legal fees		—		350
Other		286		275
	$	4,525	$	5,135

Property, Plant and Equipment, Net

As of September 30, 2017 and December 31, 2016, property, plant and equipment consisted of (in thousands):

	September 30, 2017			December 31, 2016
	(Unaudited)
Construction in progress	$	41,025		$	6,939
Buildings		23,811			4,348
Equipment		9,104			5,458
Leasehold improvements		2,494			2,367
Software		1,082			769
Furniture & fixtures		233			203
		77,749			20,084
Accumulated depreciation		(3,278	)		(1,178	)
	$	74,471		$	18,906

Intangible Assets, Net

As of September 30, 2017 and December 31, 2016, intangible assets consisted of (in thousands):

	September 30, 2017			December 31, 2016
	(Unaudited)
Technology license	$	9,042		$	9,042
Less accumulated amortization		(5,651	)		(3,956	)
	$	3,391		$	5,086

Other Assets

As of September 30, 2017 and December 31, 2016, other assets consisted of (in thousands):

	September 30, 2017		December 31, 2016
	(Unaudited)
Restricted cash	$	179	$	179
Security deposits		127		137
Equipment not placed in service		—		362
Other		18		110
	$	324	$	788

Accrued Expenses

As of September 30, 2017 and December 31, 2016, accrued expenses consisted of (in thousands):

	September 30, 2017		December 31, 2016
	(Unaudited)
Accrued construction costs	$	11,068	$	1,053
Accrued bonus		1,434		1,732
Accrued compensation		992		898
Accrued professional and service fees		882		1,008
Accrued preclinical and clinical trial costs		651		662
Accrued laboratory equipment and supplies		393		190
Other		418		321
	$	15,838	$	5,864

Other Current Liabilities

As of September 30, 2017 and December 31, 2016, other current liabilities were made up of (in thousands):

	September 30, 2017		December 31, 2016
	(Unaudited)
Deferred rent - current portion	$	501	$	197
Build-to-suit lease liability - current portion		355		281
Financing obligation - current portion		276		253
Other		233		160
	$	1,365	$	891

Investment Income, Net

	Three Months Ended September 30,						Nine Months Ended September 30,
	(Unaudited)						(Unaudited)
	2017			2016			2017			2016
Interest income	$	1,005		$	1,371		$	3,408		$	3,802
Investment amortization accretion expense, net		(359	)		(625	)		(1,298	)		(1,567	)
Net realized gains on investments		34			49			30			67
	$	680		$	795		$	2,140		$	2,302

Cash Equivalents and Marketable Securities (Tables)

9 Months Ended

Sep. 30, 2017

Cash Equivalents And Marketable Securities [Abstract]

Schedule of Cash Equivalents and Marketable Securities Available-for-Sale

	September 30, 2017
	(unaudited)
	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Current:
Commercial paper	$	5,145	$	1	$	—		$	5,146
Corporate debt securities		93,609		19		(58	)		93,570
Government sponsored securities		24,263		—		(28	)		24,235
Foreign government bonds		8,402		—		(6	)		8,396
Current portion		131,419		20		(92	)		131,347
Noncurrent:
Corporate debt securities		31,540		25		(109	)		31,456
Government sponsored securities		2,761		—		(19	)		2,742
Noncurrent portion		34,301		25		(128	)		34,198
Total	$	165,720	$	45	$	(220	)	$	165,545

At December 31, 2016, the detail of the Company’s cash equivalents and marketable securities is as follows (in thousands):

	December 31, 2016
	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Current:
Corporate debt securities	$	165,605	$	40	$	(76	)	$	165,569
Government sponsored securities		22,252		21		(1	)		22,272
Foreign government bonds		5,004		—		(2	)		5,002
Current portion		192,861		61		(79	)		192,843
Noncurrent:
Corporate debt securities		69,414		71		(290	)		69,195
Government sponsored securities		17,018		2		(38	)		16,982
Foreign government bonds		1,405		—		(11	)		1,394
Noncurrent portion		87,837		73		(339	)		87,571
Total	$	280,698	$	134	$	(418	)	$	280,414

Available-for-Sale Investments in Unrealized Loss Position

Available-for-sale investments that had been in an unrealized loss position for more and less than 12 months at September 30, 2017 and December 31, 2016 are as follows (in thousands):

	September 30, 2017
	(unaudited)
	Less than 12 months					More than 12 months
	Estimated Fair Value		Gross Unrealized Losses			Estimated Fair Value		Gross Unrealized Losses
Corporate debt securities	$	76,280	$	(130	)	$	10,892	$	(36	)
Government sponsored securities		26,978		(47	)		—		—
Foreign government bonds		7,000		(1	)		1,397		(6	)
Total	$	110,258	$	(178	)	$	12,289	$	(42	)

	December 31, 2016
	Less than 12 months					More than 12 months
	Estimated Fair Value		Gross Unrealized Losses			Estimated Fair Value		Gross Unrealized Losses
Corporate debt securities	$	17,204	$	(39	)	$	—	$	—
Government sponsored securities		150,320		(366	)		—		—
Foreign government bonds		6,396		(13	)		—		—
Total	$	173,920	$	(418	)	$	—	$	—

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

The Company recorded realized gains and losses on sales or maturities of available-for-sale securities as follows (in thousands):

	Three Months Ended September 30,						Nine Months Ended September 30,
	(unaudited)						(unaudited)
	2017			2016			2017			2016
Gross realized gains	$	43		$	51		$	45		$	143
Gross realized losses		(9	)		(2	)		(15	)		(76	)
Net realized gains	$	34		$	49		$	30		$	67

Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2017

Fair Value Disclosures [Abstract]

Summary of Financial Assets Measured at Fair Value on Recurring Basis

The following tables present the Company’s hierarchy for its assets measured at fair value on a recurring basis as of September 30, 2017 and December 31, 2016 (in thousands):

	Fair Value Measurements at September 30, 2017
	(unaudited)
	Total		Level 1		Level 2		Level 3
Assets:
Current:
Commercial paper	$	5,146	$	—	$	5,146	$	—
Corporate debt securities		93,570		—		93,570		—
Government sponsored securities		24,235		—		24,235		—
Foreign government bonds		8,396		—		8,396		—
Noncurrent:
Corporate debt securities		31,456		—		31,456		—
Government sponsored securities		2,742		—		2,742		—
Total assets measured at fair value	$	165,545	$	—	$	165,545	$	—

The table above excludes $20.9 million in depository institutions that are classified as Level 1 assets.

	Fair Value Measurements at December 31, 2016
	Total		Level 1		Level 2		Level 3
Assets:
Current:
Cash and cash equivalents*	$	2,005	$	—	$	2,005	$	—
Corporate debt securities		163,564		—		163,564		—
Government sponsored securities		22,272		—		22,272		—
Foreign government bonds		5,002		—		5,002		—
Noncurrent:
Corporate debt securities		69,195		—		69,195		—
Government sponsored securities		16,982		—		16,982
Foreign government bonds		1,394		—		1,394		—
Total assets measured at fair value	$	280,414	$	—	$	280,414	$	—

*This amount excludes $6.1 million in depository institutions that are classified as Level 1 assets.

Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2017

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock Based Compensation Expense Included in Operations Statement

The following table presents stock-based compensation expense included in the Company’s condensed consolidated statement of operations (in thousands):

	Three Months Ended September 30,					Nine Months Ended September 30,
	(unaudited)					(unaudited)
	2017			2016		2017		2016
Stock-based compensation expense:
Warrants for common stock to an officer	$	7,635		$	14,171	$	23,948	$	41,443
Employee stock options		978			3,075		3,281		12,826
Employee restricted stock units		298			1,321		523		7,851
Non-employee restricted stock units		(197	)		102		361		466
	$	8,714		$	18,669	$	28,113	$	62,586
Stock-based compensation expense in operating expenses:
Research and development	$	(3	)	$	116	$	40	$	680
Selling, general and administrative		8,717			18,553		28,073		61,906
	$	8,714		$	18,669	$	28,113	$	62,586

Summarizes Stock Option Activity

The following table summarizes stock option activity for the nine months ended September 30, 2017 (in thousands, except for share and year amounts):

	Number of Shares			Weighted- Average Exercise Price		Aggregate Intrinsic Value		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 September 30, 2017		5,693,250		$	7.71	$	16,076		5.5
Vested and Exercisable at September 30, 2017		4,998,937		$	8.47	$	13,173		6.1

Restricted Stock Units Activity

The following table summarizes the activity for restricted stock units:

	Number of Restricted Stock Units Outstanding			Weighted-Average Grant Date Fair Value
Unvested balance at December 31, 2016		814,456		$	13.98
Granted		563,483		$	4.53
Vested		(35,793	)	$	8.21
Forfeited		(275,153	)	$	10.51
Unvested balance at September 30, 2017		1,066,993		$	10.08

Summary of Warrant Activity

The following table summarizes the warrant activity for the nine months ended September 30, 2017:

Outstanding at December 31, 2016	17,768,314
Warrants exercised	(32,787	)
Outstanding at September 30, 2017	17,735,527
Vested and exercisable at September 30, 2017	15,884,027

- Definition

Tabular disclosure of warrants or rights issued. Warrants and rights outstanding are derivative securities that give the holder the right to purchase securities (usually equity) from the issuer at a specific price within a certain time frame. Warrants are often included in a new debt issue to entice investors by a higher return potential. The main difference between warrants and call options is that warrants are issued and guaranteed by the company, whereas options are exchange instruments and are not issued by the company. Also, the lifetime of a warrant is often measured in years, while the lifetime of a typical option is measured in months. Disclose the title of issue of securities called for by warrants and rights outstanding, the aggregate amount of securities called for by warrants and rights outstanding, the date from which the warrants or rights are exercisable, and the price at which the warrant or right is exercisable.

+ References + Details

Description of Business and Basis of Presentation - Additional Information (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Jan. 01, 2016
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Accumulated deficit	$ (471,455)		$ (387,063)	$ 31,000
Net cash used in operating activities	$ (35,140)	$ (27,840)

Summary of Significant Accounting Policies - Securities Excluded from the Computation of Potentially Dilutive Securities (Detail) - shares	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	24,495,770	25,152,341
Employee Stock Option
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	5,693,250	6,518,062
Outstanding Restricted Stock Units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	1,066,993	859,022
Outstanding Warrants
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	17,735,527	17,775,257

Financial Statement Details - Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Financial Statement Details [Abstract]
Prepaid services	$ 1,037	$ 1,191
Interest receivable - marketable securities	836	1,484
Prepaid insurance	816	531
Equipment and supply deposits	602	482
Tenant improvement allowance receivable	387	0
Prepaid rent	369	360
Prepaid license fees	192	462
Prepaid legal fees	0	350
Other	286	275
Total prepaid expenses and other current assets	$ 4,525	$ 5,135

Financial Statement Details - Property, Plant and Equipment, Net (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	$ 77,749	$ 20,084
Accumulated depreciation	(3,278)	(1,178)
Property, plant and equipment, net	74,471	18,906
Construction in Progress
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	41,025	6,939
Buildings
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	23,811	4,348
Equipment
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	9,104	5,458
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	2,494	2,367
Software
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	1,082	769
Furniture And Fixtures
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	$ 233	$ 203

Financial Statement Details - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Financial Statement Details [Line Items]
Depreciation expense related to property, plant and equipment	$ 900,000	$ 300,000	$ 2,300,000	$ 400,000
Non cash build to suit lease asset	5,100,000		5,100,000
Property, plant and equipment, gross	77,749,000		77,749,000		$ 20,084,000
Amortization expense	600,000	$ 400,000	1,700,000	1,300,000
Impairment loss on recognized investments			0	$ 0
Buildings
Financial Statement Details [Line Items]
Property, plant and equipment, gross	23,811,000		23,811,000		$ 4,348,000
Capital Lease
Financial Statement Details [Line Items]
Property, plant and equipment, gross	19,500,000		19,500,000
Financing Lease
Financial Statement Details [Line Items]
Property, plant and equipment, gross	$ 4,300,000		$ 4,300,000

Financial Statement Details - Intangible Assets, Net (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Finite Lived Intangible Assets [Line Items]
Intangible assets, net	$ 3,391	$ 5,086
Technology License
Finite Lived Intangible Assets [Line Items]
Total intangible assets	9,042	9,042
Less accumulated amortization	(5,651)	(3,956)
Intangible assets, net	$ 3,391	$ 5,086

Financial Statement Details - Other Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Financial Statement Details [Abstract]
Restricted cash	$ 179	$ 179
Security deposits	127	137
Equipment not placed in service	0	362
Other	18	110
Other Assets Noncurrent	$ 324	$ 788

Financial Statement Details - Accrued Expenses (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Financial Statement Details [Abstract]
Accrued construction costs	$ 11,068	$ 1,053
Accrued bonus	1,434	1,732
Accrued compensation	992	898
Accrued professional and service fees	882	1,008
Accrued preclinical and clinical trial costs	651	662
Accrued laboratory equipment and supplies	393	190
Other	418	321
Accrued Liabilities Current	$ 15,838	$ 5,864

Financial Statement Details - Other Current Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Financial Statement Details [Abstract]
Deferred rent - current portion	$ 501	$ 197
Build-to-suit lease liability - current portion	355	281
Financing obligation - current portion	276	253
Other	233	160
Other current liabilities	$ 1,365	$ 891

Financial Statement Details - Investment Income, Net (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Financial Statement Details [Abstract]
Interest income	$ 1,005	$ 1,371	$ 3,408	$ 3,802
Investment amortization accretion expense, net	(359)	(625)	(1,298)	(1,567)
Net realized gains on investments	34	49	30	67
Investment income, net	$ 680	$ 795	$ 2,140	$ 2,302

Cost Method Investment - Additional Information (Detail) - USD ($)	Sep. 30, 2017	Mar. 31, 2017	Dec. 31, 2016
Schedule Of Cost Method Investments [Line Items]
Cost method investment	$ 8,500,000		$ 0
Viracta Therapeutics, Inc. \| Series B Convertible Preferred Stock
Schedule Of Cost Method Investments [Line Items]
Cost method investment		$ 8,500,000
Viracta Therapeutics, Inc. \| Series B Convertible Preferred Stock \| Maximum
Schedule Of Cost Method Investments [Line Items]
Option to purchase additional shares under cost method investment	$ 8,500,000

Cash Equivalents and Marketable Securities - Additional Information (Detail) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2017 Security	Dec. 31, 2016 USD ($)
Schedule Of Available For Sale Securities [Line Items]
Available for sale securities maturity period	4 years 9 months 19 days
Maximum
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale securities, period of unrealized loss positions	12 months	12 months
Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Cash equivalent portions included in current fair values \| $		$ 2.0
Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Number of available-for-sale securities in unrealized loss positions \| Security	57

Cash Equivalents and Marketable Securities - Schedule of Cash Equivalents and Marketable Securities Available-for-Sale (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 165,720	$ 280,698
Unrealized Gains	45	134
Unrealized Losses	(220)	(418)
Fair Value	165,545	280,414
Current Assets
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	131,419	192,861
Unrealized Gains	20	61
Unrealized Losses	(92)	(79)
Fair Value	131,347	192,843
Current Assets \| Government Sponsored Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	24,263	22,252
Unrealized Gains	0	21
Unrealized Losses	(28)	(1)
Fair Value	24,235	22,272
Current Assets \| Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	93,609	165,605
Unrealized Gains	19	40
Unrealized Losses	(58)	(76)
Fair Value	93,570	165,569
Current Assets \| Commercial Paper
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	5,145
Unrealized Gains	1
Unrealized Losses	0
Fair Value	5,146
Current Assets \| Foreign Government Bonds
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	8,402	5,004
Unrealized Gains	0	0
Unrealized Losses	(6)	(2)
Fair Value	8,396	5,002
Noncurrent Assets
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	34,301	87,837
Unrealized Gains	25	73
Unrealized Losses	(128)	(339)
Fair Value	34,198	87,571
Noncurrent Assets \| Government Sponsored Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	2,761	17,018
Unrealized Gains	0	2
Unrealized Losses	(19)	(38)
Fair Value	2,742	16,982
Noncurrent Assets \| Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	31,540	69,414
Unrealized Gains	25	71
Unrealized Losses	(109)	(290)
Fair Value	$ 31,456	69,195
Noncurrent Assets \| Foreign Government Bonds
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost		1,405
Unrealized Gains		0
Unrealized Losses		(11)
Fair Value		$ 1,394

Cash Equivalents and Marketable Securities - Available-for-Sale Investments in Unrealized Loss Position (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Schedule Of Available For Sale Securities [Line Items]
Available-for-Sale Investments, Less than 12 months, Estimated Fair Value	$ 110,258	$ 173,920
Available-for-Sale Investments, Less than 12 months, Gross Unrealized Losses	(178)	(418)
Available-for-Sale Investments, More than 12 months, Estimated Fair Value	12,289	0
Available-for-Sale Investments, More than 12 months, Gross Unrealized Losses	(42)	0
Government Sponsored Securities
Schedule Of Available For Sale Securities [Line Items]
Available-for-Sale Investments, Less than 12 months, Estimated Fair Value	26,978	150,320
Available-for-Sale Investments, Less than 12 months, Gross Unrealized Losses	(47)	(366)
Available-for-Sale Investments, More than 12 months, Estimated Fair Value	0	0
Available-for-Sale Investments, More than 12 months, Gross Unrealized Losses	0	0
Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Available-for-Sale Investments, Less than 12 months, Estimated Fair Value	76,280	17,204
Available-for-Sale Investments, Less than 12 months, Gross Unrealized Losses	(130)	(39)
Available-for-Sale Investments, More than 12 months, Estimated Fair Value	10,892	0
Available-for-Sale Investments, More than 12 months, Gross Unrealized Losses	(36)	0
Foreign Government Bonds
Schedule Of Available For Sale Securities [Line Items]
Available-for-Sale Investments, Less than 12 months, Estimated Fair Value	7,000	6,396
Available-for-Sale Investments, Less than 12 months, Gross Unrealized Losses	(1)	(13)
Available-for-Sale Investments, More than 12 months, Estimated Fair Value	1,397	0
Available-for-Sale Investments, More than 12 months, Gross Unrealized Losses	$ (6)	$ 0

Cash Equivalents and Marketable Securities -Schedule of Realized Gains and Losses on Sales or Maturities of Available-for-Sale Securities (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Cash Equivalents And Marketable Securities [Abstract]
Available-for-sale Securities, Gross Realized Gains	$ 43	$ 51	$ 45	$ 143
Available-for-sale Securities, Gross Realized Losses	(9)	(2)	(15)	(76)
Available-for-sale Securities, Net Realized Gains	$ 34	$ 49	$ 30	$ 67

Fair Value Measurements - Summary of Financial Assets Measured at Fair Value on Recurring Basis (Parenthetical) (Detail) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash in depository institutions	$ 20.9	$ 6.1

Collaboration and License Agreements - Additional Information (Detail)	1 Months Ended	3 Months Ended	9 Months Ended
	May 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2017 USD ($) Patient
GSH-BSD
Licensing Agreement [Line Items]
License agreement termination notice period			60 days
GSH \| Phase I Glioblastoma Study
Licensing Agreement [Line Items]
Milestone Payment Amount		$ 900,000	$ 900,000
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

Commitment and Contingencies - Additional Information (Detail)	1 Months Ended		3 Months Ended		9 Months Ended
	Apr. 30, 2017 USD ($) ft²	Sep. 30, 2015 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($) ft²	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($) ft²	Dec. 31, 2016 USD ($)	Nov. 30, 2015 ft²	May 31, 2015 ft²
Commitments And Contingencies [Line Items]
Rent expense			$ 600,000	$ 800,000	$ 2,000,000	$ 2,200,000
Non cash build to suit lease asset			5,100,000		5,100,000
Property, plant and equipment, gross			77,749,000		77,749,000		$ 20,084,000
Doug St, LLC
Commitments And Contingencies [Line Items]
Base rent - monthly					$ 100,000
Period of agreement					The lease runs from July 2016 through July 2023. The Company has 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
Percentage of annual increase of base rent					3.00%
Annual percentage increases to base rent commencement date					Jul. 31, 2017
Costs incurred			29,100,000		$ 29,100,000
Non cash build to suit lease asset			5,100,000		$ 5,100,000
Property and equipment estimated useful lives					39 years
Doug St, LLC \| Research and Development
Commitments And Contingencies [Line Items]
Rent expense			100,000	100,000	$ 200,000	100,000
NantWorks
Commitments And Contingencies [Line Items]
Base rent - monthly					$ 47,000
Number of square foot of facility leased \| ft²								9,500	9,500
Period of agreement					The license was effective in May 2015 and extends through December 2020. The Company has the option to extend the license through December 2023. The monthly license fee is $47,000 with annual increases of 3% beginning in January 2017.
Percentage of annual increase of base rent					3.00%
Annual percentage increases to base rent commencement date					Jan. 31, 2017
Costs incurred				3,500,000		3,500,000
Property and equipment estimated useful lives					39 years
NantWorks \| Building Under Financing Lease
Commitments And Contingencies [Line Items]
Property, plant and equipment, gross			4,300,000		$ 4,300,000
NantWorks \| Research and Development
Commitments And Contingencies [Line Items]
Rent expense			$ 47,000	$ 100,000	100,000	$ 300,000
El Segundo California \| Doug St, LLC
Commitments And Contingencies [Line Items]
Number of square foot of facility leased \| ft²				24,250		24,250
El Segundo California \| Agreement to Purchase Commercial Building
Commitments And Contingencies [Line Items]
Area of Land \| ft²	36,000
Escrow deposit	$ 5,000,000
Remaining purchase price paid including closing costs					$ 15,300,000
Base rent - monthly	$ 0
Escrow closed period					2017-09
USPTO
Commitments And Contingencies [Line Items]
Attorney's fees and expert witness fees		$ 100,000

Related Party Agreements - Additional Information (Detail)	1 Months Ended		3 Months Ended		9 Months Ended
	Apr. 30, 2017 USD ($) ft²	Apr. 30, 2016 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($) ft²	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($) ft²	Jul. 31, 2017 Officer	Jun. 30, 2017 USD ($)	Feb. 28, 2017 USD ($)	Dec. 31, 2016 USD ($)	Aug. 31, 2016	Nov. 30, 2015 ft²	May 31, 2015 ft²
Related Party Transaction [Line Items]
Research and development			$ 11,069,000	$ 8,364,000	$ 30,023,000	$ 19,708,000
Prepaid expenses and other current assets			4,525,000		4,525,000					$ 5,135,000
Due to related parties			1,986,000		1,986,000					$ 1,753,000
Selling, general and administrative			13,381,000	24,423,000	43,736,000	79,678,000
Chan Soon-Shiong Institutes for Medicine (CSSIM) \| CALIFORNIA
Related Party Transaction [Line Items]
Number of officers \| Officer							2
Research and development			36,000		$ 36,000
Tensorcom, Inc \| San Diego California
Related Party Transaction [Line Items]
Period of agreement					Initial lease from May 1, 2017 through April 30, 2018
Sublease termination notice period	30 days
Number of square foot of facility leased \| ft²	6,557
Base rent - monthly	$ 25,000
Percentage of annual increase of base rent	3.00%
Due between parties			0		$ 0
Tensorcom, Inc \| San Diego California \| Other Income
Related Party Transaction [Line Items]
Sublease revenue recognized			100,000		100,000
VivaBioCell S.p.A.
Related Party Transaction [Line Items]
Research and development			200,000		$ 400,000
Prepaid expenses and other current assets									$ 600,000
Doug St, LLC
Related Party Transaction [Line Items]
Period of agreement					The lease runs from July 2016 through July 2023. The Company has 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.
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
Due to related parties			0		$ 0
Doug St, LLC \| Research and Development
Related Party Transaction [Line Items]
Rent expense			100,000	$ 100,000	200,000	$ 100,000
Doug St, LLC \| El Segundo California
Related Party Transaction [Line Items]
Number of square foot of facility leased \| ft²				24,250		24,250
Altor
Related Party Transaction [Line Items]
Research and development charges incurred for supplies or milestone			0		0
Altor \| Minimum
Related Party Transaction [Line Items]
Percentage of ownership interest owned by CEO											20.00%
NantBioScience
Related Party Transaction [Line Items]
Research and development	$ 600,000	$ 600,000	$ 200,000	$ 100,000	$ 500,000	$ 300,000
Initial term of agreement entered into with the related party by the entity					5 years
Research and development expense, ratable payment period			12 months	12 months	12 months	12 months
NantWorks
Related Party Transaction [Line Items]
Number of square foot of facility leased \| ft²												9,500	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
Due to related parties			$ 1,900,000		$ 1,900,000
NantWorks \| Shared Services Agreement
Related Party Transaction [Line Items]
Research and development			600,000	$ 400,000	2,100,000	$ 1,200,000
Selling, general and administrative			700,000	800,000	2,000,000	2,300,000
NantWorks \| Reimbursements \| Shared Services Agreement
Related Party Transaction [Line Items]
Research and development			300,000	100,000	600,000	100,000
Selling, general and administrative			0	17,000	200,000	26,000
NantWorks \| Research and Development
Related Party Transaction [Line Items]
Rent expense			47,000	100,000	100,000	300,000
NantOmnics
Related Party Transaction [Line Items]
Research and development			0	100,000	$ 13,000	200,000
Due to related parties								$ 0
Initial term of agreement entered into with the related party by the entity					5 years
Related party, agreement renewal term					1 year
Nant Cell Inc
Related Party Transaction [Line Items]
Research and development			0	$ 0	$ 300,000	$ 0
Due to related parties			100,000		$ 100,000
Initial term of agreement entered into with the related party by the entity					5 years
Related party, agreement renewal term					1 year
Related parties, capitalized equipment amount			300,000
Related parties, deposit paid for consumables			$ 100,000

Stockholders' Equity - Additional Information (Detail) - USD ($)	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2017	Dec. 31, 2016	Nov. 30, 2015
Class Of Stock [Line Items]
Total amount authorized for repurchase				$ 50,000,000
Repurchase of common stock, shares	0	3,072,209	2,157,944
Repurchase of common stock before commissions, value		$ 12,500,000	$ 15,800,000
Broker commissions on the repurchases		100,000
Remained authorized shares for repurchase	$ 21,800,000	$ 21,800,000
Minimum
Class Of Stock [Line Items]
Repurchase of common stock, par value		$ 3.10
Maximum
Class Of Stock [Line Items]
Repurchase of common stock, par value		$ 4.75

Stock-Based Compensation - Stock Based Compensation Expenses Related to Statement of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 8,714	$ 18,669	$ 28,113	$ 62,586
Warrants For Common Stock \| Officer
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	7,635	14,171	23,948	41,443
Employee Stock Option
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	978	3,075	3,281	12,826
Employee Restricted Stock Units
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	298	1,321	523	7,851
Non Employee Restricted Stock Units
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	(197)	102	361	466
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	(3)	116	40	680
Selling, General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 8,717	$ 18,553	$ 28,073	$ 61,906

Stock-Based Compensation - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Mar. 31, 2016	Sep. 30, 2017	Dec. 31, 2016	Jan. 01, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Accumulated deficit		$ (471,455)	$ (387,063)	$ 31,000
Additional stock compensation expense	$ 27,000
Outstanding Warrants
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized stock-based compensation expense related to non-vested stock options		$ 25,500
Weighted-average period for recognition		9 months 19 days
Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Aggregate intrinsic value of stock options exercised		$ 1,700
Unrecognized stock-based compensation expense related to non-vested stock options		$ 5,800
Weighted-average period for recognition		1 year 6 months
Employee Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average period for recognition		3 years
Number of Shares, Granted		486,233
Unrecognized compensation cost related to non-vested stock options		$ 3,400
Non Employee Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average period for recognition		2 years 7 months 7 days
Number of Shares, Granted		77,250
Unrecognized compensation cost related to non-vested stock options		$ 1,300
Employee Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average period for recognition		2 years 10 months 25 days
Number of Shares, Granted		563,483
Unrecognized compensation cost related to non-vested stock options		$ 4,700
Employee Restricted Stock Units \| Employees Of Related Company
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Shares, Granted		27,250

Stock-Based Compensation - Stock Option Activity (Detail) - Employee Stock Option - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Number of Shares
Stock Options, Beginning Balance	6,307,386
Stock Options, Options exercised	(614,136)
Stock Options, Ending Balance	5,693,250	6,307,386
Stock Options, Vested and Exercisable	4,998,937
Weighted Average Exercise Price
Weighted Average Exercise Price, Outstanding Beginning balance	$ 7.14
Weighted Average Exercise Price, Options exercised	1.88
Weighted Average Exercise Price, Outstanding Ending balance	7.71	$ 7.14
Weighted Average Exercise Price, Vested and Exercisable	$ 8.47
Aggregate Intrinsic Value
Aggregate Intrinsic Value, Outstanding	$ 16,076	$ 19,100
Aggregate Intrinsic Value, Vested and Exercisable	$ 13,173
Weighted Average Remaining Contractual Life
Weighted Average Remaining Contractual Life, Outstanding	5 years 6 months	6 years 4 months 24 days
Weighted Average Remaining Contractual Life, Vested and Exercisable	6 years 1 month 6 days

Stock-Based Compensation - Restricted Stock Units Activity (Detail) - Outstanding Restricted Stock Units	9 Months Ended
	Sep. 30, 2017 $ / shares shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Shares, Unvested, Beginning balance \| shares	814,456
Number of Shares, Granted \| shares	563,483
Number of Shares, Vested \| shares	(35,793)
Number of Shares, Forfeited \| shares	(275,153)
Number of Shares, Unvested, Ending balance \| shares	1,066,993
Weighted-Average Grant Date Fair Value, Unvested, beginning balance \| $ / shares	$ 13.98
Weighted-Average Grant Date Fair Value, Granted \| $ / shares	4.53
Weighted-Average Grant Date Fair Value, Vested \| $ / shares	8.21
Weighted-Average Grant Date Fair Value, Forfeited \| $ / shares	10.51
Weighted-Average Grant Date Fair Value, Unvested, ending balance \| $ / shares	$ 10.08

Stock-Based Compensation - Summary of Warrant Activity (Detail) - Outstanding Warrants	9 Months Ended
	Sep. 30, 2017 shares
Warrant [Line Items]
Warrants, Beginning Balance	17,768,314
Warrants exercised	(32,787)
Warrants, Ending Balance	17,735,527
Warrants, Vested and exercisable Ending Balance	15,884,027

Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Tax [Line Items]
Federal statutory tax rate			34.00%
Company's effective tax rate			0.00%
Tax (benefit) expense	$ (13,000)	$ 39,000	$ 23,000	$ 100,000
Tax benefit in other comprehensive income (loss)	15,000	(200,000)	43,000	200,000
Korea
Income Tax [Line Items]
Tax benefit	$ 100,000	$ 100,000	$ 300,000	$ 300,000

Subsequent Events - Additional Information (Detail) - Chan Soon-Shiong Institutes for Medicine (CSSIM) - CALIFORNIA $ in Millions	1 Months Ended
	Nov. 06, 2017 USD ($) Officer	Jul. 31, 2017 Officer
Subsequent Event [Line Items]
Number of officers		2
Subsequent Event
Subsequent Event [Line Items]
Number of officers	2
Estimated cost of clinical trial agreement \| $	$ 7.1

Fair Value Measurements - Summary of Financial Assets Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	$ 165,545	$ 280,414
Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	0	0
Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	165,545	280,414
Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	0	0
Current Assets \| Foreign Government Bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	8,396	5,002
Current Assets \| Government Sponsored Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	24,235	22,272
Current Assets \| Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	5,146
Current Assets \| Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	93,570	163,564
Current Assets \| Cash and cash equivalents
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value		2,005
Current Assets \| Level 1 \| Foreign Government Bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	0	0
Current Assets \| Level 1 \| Government Sponsored Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	0	0
Current Assets \| Level 1 \| Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	0
Current Assets \| Level 1 \| Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	0	0
Current Assets \| Level 1 \| Cash and cash equivalents
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value		0
Current Assets \| Level 2 \| Foreign Government Bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	8,396	5,002
Current Assets \| Level 2 \| Government Sponsored Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	24,235	22,272
Current Assets \| Level 2 \| Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	5,146
Current Assets \| Level 2 \| Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	93,570	163,564
Current Assets \| Level 2 \| Cash and cash equivalents
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value		2,005
Current Assets \| Level 3 \| Foreign Government Bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	0	0
Current Assets \| Level 3 \| Government Sponsored Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	0	0
Current Assets \| Level 3 \| Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	0
Current Assets \| Level 3 \| Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	0	0
Current Assets \| Level 3 \| Cash and cash equivalents
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value		0
Noncurrent Assets \| Foreign Government Bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value		1,394
Noncurrent Assets \| Government Sponsored Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	2,742	16,982
Noncurrent Assets \| Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	31,456	69,195
Noncurrent Assets \| Level 1 \| Foreign Government Bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value		0
Noncurrent Assets \| Level 1 \| Government Sponsored Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	0	0
Noncurrent Assets \| Level 1 \| Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	0	0
Noncurrent Assets \| Level 2 \| Foreign Government Bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value		1,394
Noncurrent Assets \| Level 2 \| Government Sponsored Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	2,742	16,982
Noncurrent Assets \| Level 2 \| Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	31,456	69,195
Noncurrent Assets \| Level 3 \| Foreign Government Bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value		0
Noncurrent Assets \| Level 3 \| Government Sponsored Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	0	0
Noncurrent Assets \| Level 3 \| Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	$ 0	$ 0