ImmunityBio (IBRX) 10-Q 8 May 17 2017 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2017	May 03, 2017
Document Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q1
Trading Symbol	NK
Entity Registrant Name	NANTKWEST, INC.
Entity Central Index Key	1,326,110
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		82,155,862

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 13,596	$ 8,083
Due from related parties	82	1,089
Prepaid expenses and other current assets	4,896	5,135
Marketable securities	177,374	190,838
Total current assets	195,948	205,145
Marketable securities, noncurrent	71,487	87,571
Property, plant and equipment, net	22,558	18,906
Cost method investment	8,500	0
Intangible assets, net	4,521	5,086
Other assets	661	788
Total assets	303,675	317,496
Current liabilities:
Accounts payable	4,280	4,045
Accrued expenses	6,858	5,864
Due to related parties	2,124	1,753
Other current liabilities	939	891
Total current liabilities	14,201	12,553
Build-to-suit liability, less current portion	5,475	5,651
Financing obligation, less current portion	1,955	2,025
Deferred rent	2,374	2,426
Deferred revenue	182	187
Deferred tax liability	903	996
Other liabilities	216	240
Total liabilities	25,306	24,078
Commitments and contingencies (Note 7)	0	0
Stockholders’ equity
Common stock	8	8
Additional paid-in capital	691,229	680,757
Accumulated other comprehensive loss	(240)	(284)
Accumulated deficit	(412,628)	(387,063)
Total stockholders’ equity	278,369	293,418
Total liabilities and stockholders’ equity	$ 303,675	$ 317,496

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 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	82,155,862	81,983,937
Common stock, shares outstanding	82,155,862	81,983,937

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Income Statement [Abstract]
Revenue	$ 11	$ 6
Operating expenses:
Research and development	9,248	4,955
Selling, general and administrative	16,227	26,667
Total operating expenses	25,475	31,622
Loss from operations	(25,464)	(31,616)
Other income:
Investment income, net	779	768
Interest expense	(37)	0
Other income, net	109	28
Total other income	851	796
Loss before income taxes	(24,613)	(30,820)
Income tax benefit	(98)	(143)
Net loss	$ (24,515)	$ (30,677)
Net loss per share:
Basic and diluted	$ (0.30)	$ (0.38)
Weighted average number of shares during the period:
Basic and diluted	82,138,438	81,574,709

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (24,515)	$ (30,677)
Other comprehensive income, net of income taxes:
Net unrealized gain on available-for-sale securities	44	517
Reclassification of net realized gains on available-for-sale securities included in net loss	0	(7)
Total other comprehensive income	44	510
Comprehensive loss	$ (24,471)	$ (30,167)

Condensed Consolidated Stateme6

Condensed Consolidated Statement of Stockholders' Equity (Unaudited) - 3 months ended Mar. 31, 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	10,018	$ 0	10,018	0	0
Vesting of restricted stock units		6,625
Employee payroll taxes withheld related to option exercises and vesting of restricted stock units	(700)	$ 0	(700)	0	0
Employee payroll taxes withheld related to option exercises and vesting of restricted stock units, Shares		(148,836)
Repurchase of common stock	$ (1,050)	$ 0	0	0	(1,050)
Repurchase of common stock, Shares	(300,000)	(300,000)
Other comprehensive income, net	$ 44	$ 0	0	44	0
Net loss	(24,515)	0	0	0	(24,515)
Ending Balance at Mar. 31, 2017	$ 278,369	$ 8	$ 691,229	$ (240)	$ (412,628)
Ending Balance, Shares at Mar. 31, 2017	82,155,862	82,155,862

Condensed Consolidated Stateme7

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Operating activities:
Net loss	$ (24,515)	$ (30,677)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,162	485
Stock-based compensation expense	10,018	20,562
Deferred income tax benefit	(93)	(145)
Loss on disposal of assets	0	15
Non-cash interest items, net	253	(295)
Amortization of net premiums on marketable securities	572	426
Gain on sales of marketable securities	0	(46)
Changes in operating assets and liabilities:
Prepaid and other current assets	(13)	(160)
Other assets	126	(337)
Accounts payable	725	(737)
Accrued expenses and other liabilities	434	1,236
Due to related parties	1,314	322
Deferred rent and revenue	(40)	495
Net cash used in operating activities	(10,057)	(8,856)
Investing activities:
Purchases of property, plant and equipment	(4,509)	(1,067)
Purchase of cost method investment	(8,500)	0
Purchases of marketable securities	(25,207)	(111,397)
Sales/maturities of marketable securities	54,254	10,552
Net cash provided by (used in) investing activities	16,038	(101,912)
Financing activities:
Principal payments of financing obligation	(22)	0
Proceeds from exercise of stock options and warrants	1,154	660
Repurchase of common stock	(1,050)	(2,550)
Net share settlement for RSU vesting and option exercises	(550)	0
Net cash used in financing activities	(468)	(1,890)
Net increase (decrease) in cash and cash equivalents	5,513	(112,658)
Cash and cash equivalents, beginning of period	8,083	175,908
Cash and cash equivalents, end of period	13,596	63,250
Cash paid during the period for:
Interest	37	0
Income taxes	0	1
Supplemental disclosure of non-cash investing and financing activities:
Property and equipment purchases included in accounts payable and accrued expenses	2,492	1,074
Unrealized gain on marketable securities	$ 70	$ 796

Description of Business and Bas

Description of Business and Basis of Presentation	3 Months Ended
	Mar. 31, 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. The Company also 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 cell lines and intellectual property to numerous pharmaceutical and biotechnology companies for such non-clinical uses. 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 The accompanying condensed consolidated balance sheet at March 31, 2017, the condensed consolidated statements of operations and comprehensive loss for the three months ended March 31, 2017, the condensed consolidated statements of cash flows for the three months ended March 31, 2017, and the condensed consolidated statement of stockholders’ equity for the three months ended March 31, 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 subsidiary, Inex Bio, Inc., and have been prepared in accordance with GAAP. All intercompany amounts have been eliminated. Liquidity As of March 31, 2017, the Company had an accumulated deficit of approximately $412.6 million. The Company also had negative cash flow from operations of approximately $10.1 million during the three months ended March 31, 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 the foreseeable future, 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 Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 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 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 March 31, 2017 2016 Outstanding options 5,693,248 7,788,883 Outstanding restricted stock units 1,060,381 1,329,438 Outstanding warrants 17,768,314 17,817,687 Total 24,521,943 26,936,008 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. Adoption of ASU 2016-18 is not expected to 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. 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 In January 2016, the FASB issued ASU 2016-01, Financial Instruments – Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities. 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 Revenue Recognition doption of ASU 2014-09 is not expected to have a significant impact, the Company is currently evaluating the impact of the adoption in the Company’s consolidated financial statements and disclosures.

Financial Statement Details

Financial Statement Details	3 Months Ended
	Mar. 31, 2017
Financial Statement Details [Abstract]
Financial Statement Details	3. Financial Statement Details Prepaid Expenses and Other Current Assets As of March 31, 2017 and December 31, 2016, prepaid expenses and other current assets consisted of (in thousands): March 31, 2017 December 31, 2016 (Unaudited) Prepaid services $ 1,436 $ 1,191 Interest receivable - marketable securities 1,232 1,484 Equipment deposits 482 482 Prepaid license fees 423 462 Prepaid insurance 371 531 Prepaid rent 360 360 Prepaid legal fees 350 350 Other 242 275 $ 4,896 $ 5,135 Property, Plant and Equipment, Net As of March 31, 2017 and December 31, 2016, property, plant and equipment consisted of (in thousands): March 31, 2017 December 31, 2016 (Unaudited) Construction in progress $ 9,627 $ 6,939 Equipment 6,933 5,458 Building under financing lease 4,348 4,348 Leasehold improvements 2,370 2,367 Software 857 769 Furniture & fixtures 221 203 24,356 20,084 Accumulated depreciation (1,798 ) (1,178 ) $ 22,558 $ 18,906 Depreciation expense related to property, plant and equipment was $0.6 million and $37,000 for the three months ended March 31, 2017 and 2016, respectively. Building value of $4.3 million under a financing lease represents 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 7 – Financing Lease Obligation Construction in progress as of March 31, 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 7 – Build-to-suit Lease Intangible Assets, Net As of March 31, 2017 and December 31, 2016, intangible assets consisted of (in thousands): March 31, 2017 December 31, 2016 (Unaudited) Technology license $ 9,042 $ 9,042 Less accumulated amortization (4,521 ) (3,956 ) $ 4,521 $ 5,086 Amortization expense was $0.6 million and $0.4 million for the three months ended March 31, 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 March 31, 2017 and December 31, 2016, other assets consisted of (in thousands): March 31, 2017 December 31, 2016 (Unaudited) Equipment not placed in service $ 326 $ 362 Restricted cash 179 179 Security deposit 139 137 Other 17 110 $ 661 $ 788 Accrued Expenses As of March 31, 2017 and December 31, 2016, accrued expenses consisted of (in thousands): March 31, 2017 December 31, 2016 (Unaudited) Accrued bonus $ 2,379 $ 1,732 Accrued compensation 1,374 898 Accrued construction costs 1,261 1,243 Accrued professional and service fees 850 1,008 Accrued preclinical and clinical trial costs 434 662 Accrued software license fees 193 121 Other 367 200 $ 6,858 $ 5,864 Other Current Liabilities As of March 31, 2017 and December 31, 2016, other current liabilities were made up of (in thousands): March 31, 2017 December 31, 2016 (Unaudited) Build-to-suit lease liability - current portion $ 290 $ 281 Financing obligation - current portion 261 253 Deferred rent - current portion 215 197 Other 173 160 $ 939 $ 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 months ended March 31, 2017 and 2016 (in thousands): Three Months Ended March 31, (Unaudited) 2017 2016 Interest income $ 1,354 $ 1,193 Investment amortization accretion expense, net (572 ) (426 ) Net realized gains (losses) on investments (3 ) 1 $ 779 $ 768 Interest income includes interest from the Company’s bank deposits. The Company did not recognize an impairment loss on any investments for the three months ended March 31, 2017 and 2016.

Cost Method Investment

Cost Method Investment	3 Months Ended
	Mar. 31, 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 has an option (but not the obligation) 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 12 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 March 31, 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 cost of the investment is recorded in cost method investment in the condensed consolidated balance sheet as of March 31, 2017.

Cash Equivalents and Marketable

Cash Equivalents and Marketable Securities	3 Months Ended
	Mar. 31, 2017
Cash Equivalents And Marketable Securities [Abstract]
Cash Equivalents and Marketable Securities	5. Cash Equivalents and Marketable Securities As of March 31, 2017, all of the Company’s marketable securities are classified as available-for-sale and are scheduled to mature within 4.5 years. At March 31, 2017, the detail of the Company’s cash equivalents and marketable securities is as follows (in thousands): March 31, 2017 (unaudited) Amortized Cost Unrealized Gains Unrealized Losses Fair Value Current: Corporate debt securities $ 144,473 $ 38 $ (94 ) $ 144,417 Government sponsored securities 23,972 2 (14 ) 23,960 Foreign government bonds 8,998 — (1 ) 8,997 Current portion 177,443 40 (109 ) 177,374 Noncurrent: Corporate debt securities 54,946 88 (184 ) 54,850 Government sponsored securities 15,282 1 (43 ) 15,240 Foreign government bonds 1,404 — (7 ) 1,397 Noncurrent portion 71,632 89 (234 ) 71,487 Total $ 249,075 $ 129 $ (343 ) $ 248,861 There are no cash equivalents as of March 31, 2017. 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 March 31, 2017 and December 31, 2016 are as follows (in thousands): March 31, 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 $ 129,429 $ (277 ) $ — $ — Government sponsored securities 22,176 (57 ) — — Foreign government bonds 6,392 (9 ) — — Total $ 157,997 $ (343 ) $ — $ — 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 $ 150,320 $ (366 ) $ — $ — Government sponsored securities 17,204 (39 ) — — 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 three months ended March 31, 2017. At March 31, 2017, 73 The Company recorded realized gains and losses on sales or maturities of available-for-sale securities as follows (in thousands): Three Months Ended March 31, (unaudited) 2017 2016 Gross realized gains $ 2 $ 58 Gross realized losses (5 ) (57 ) Net realized (losses) gains $ (3 ) $ 1

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 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 table presents the Company’s hierarchy for its assets measured at fair value on a recurring basis as of March 31, 2017 and December 31, 2016 (in thousands): Fair Value Measurements at March 31, 2017 (unaudited) Total Level 1 Level 2 Level 3 Assets: Current: Corporate debt securities $ 144,417 $ — $ 144,417 $ — Government sponsored securities 23,960 — 23,960 — Foreign government bonds 8,997 — 8,997 — Noncurrent: Corporate debt securities 54,850 — 54,850 — Government sponsored securities 15,240 — 15,240 — Foreign government bonds 1,397 — 1,397 — Total assets measured at fair value $ 248,861 $ — $ 248,861 $ — All cash and cash equivalents reported in the condensed consolidated balance sheet as of March 31, 2017 are in depository institutions and 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 three months ended March 31, 2017 and 2016. As of March 31, 2017, the Company did not estimate the fair value of the Viracta 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.

Commitment and Contingencies

Commitment and Contingencies	3 Months Ended
	Mar. 31, 2017
Commitments And Contingencies Disclosure [Abstract]
Commitments and contingencies	7. Commitments and Contingencies 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 8). 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 three months ended March 31, 2017, the Company dosed the first patient with ALT-803 in its Phase II Merkel Cell Carcinoma trial and is preparing to dose the second patient. No charges for supplies or milestones by Altor have been incurred in association with the above trial during the three months ended March 31, 2017. 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. On February 9, 2017, a three-judge panel of the Federal Circuit heard oral arguments on our appeal and took the matter under submission. In May 2017, the Federal Circuit affirmed the U.S. District Court’s summary judgement ruling. Based on the information available at present, the Company cannot reasonably estimate a range of loss for this action. Accordingly, no liability associated with this action 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. On September 6, 2016, a shareholder derivative complaint captioned Bushansky v. Soon-Shiong, et al. 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 in San Diego, California; (v) research and manufacturing space in Culver City, California, from a related party (Note 8) and; (vi) a research and manufacturing facility in El Segundo, California, also from a related party (Note 8). The Company recognizes rent expense under its operating leases on a straight-line basis. Rent expense for each of the three months ended March 31, 2017 and 2016 was $0.7 million. Build-to-suit Lease In September 2016, the Company entered into a lease agreement with 605 Doug St, LLC, a related party (Note 8), 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 March 31, 2017, the Company recorded $0.1 million in rent expense, 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 $4.3 million as of March 31, 2017, which is reflected in construction in progress 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 March 31, 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 Financing Lease Obligation In November 2015, the Company entered into a facility license agreement with NantWorks LLC (NantWorks) (Note 8) 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 March 31, 2017 and 2016, the Company recorded $47,000 and $0.1 million, 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. Commitments The Company has not entered into any new significant contracts during the three months ended March 31, 2017.

Related Party Agreements

Related Party Agreements	3 Months Ended
	Mar. 31, 2017
Related Party Transactions [Abstract]
Related Party Agreements	8. 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. 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 recognized 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 months ended March 31, 2017, $0.1 million 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 7 – Build-to-suit Lease 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 and holds a greater than 20% ownership interest in Altor. No charges for supplies or milestones by Altor have been incurred in association with the above trial during the three months ended March 31, 2017. NantBioScience, Inc. In March 2016, NantBioScience, Inc. (NantBioScience), a NantWorks company, and the National Cancer Institute entered into a cooperative research and development agreement. The agreement covers NantBioScience 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 this 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 $0.1 million and $0 of expense, respectively, as of three months ended March 31, 2017 and 2016. 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 March 31, 2017 and 2016, the Company recorded $0.7 million and $0.8 million, respectively, to selling, general and administrative expense and $0.8 million and $0.3 million, respectively, in research and development expense 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 March 31, 2017, the Company recorded expense reimbursements of $0.1 million to selling, general and administrative expense and $0.1 million to research and development expense. The Company owed NantWorks a net amount of $2.1 million for all agreements between the two affiliates at March 31, 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 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 7 - Financing Lease Obligation 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 March 31, 2017 and 2016, the Company recorded operating expense of $0 and $0.1 million, respectively, under the agreement to research and development expense in the condensed consolidated statement of operations. The Company owed NantOmics $0 at March 31, 2017. NantCell, Inc. In June 2015, the Company also entered into a supply agreement with NantCell, Inc. (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 Company also has the right to purchase reagents and consumables associated with such equipment from NantCell. In September 2015, the Company made a $0.5 million nonrefundable, upfront payment to NantCell as required by the agreement, which upfront payment is creditable against the Company’s future development activities and equipment purchases under the agreement. The agreement has an initial term of five years and renews automatically for successive one year periods unless terminated earlier. The upfront payment was included in prepaid expenses in the condensed consolidated balance sheets. During the three months ended March 31, 2017, the Company consumed the remaining $0.3 million of the $0.5 million prepayment, which was recorded to research and development expense in the condensed consolidated statement of operations.

Stockholders' Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2017
Equity [Abstract]
Stockholders' Equity	9. 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 months ended March 31, 2017, the Company repurchased 300,000 shares of its common stock, at $3.50 per share for a total of $1.1 million. 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 March 31, 2017, $33.1 million remained authorized for repurchase under the Company’s 2015 Share Repurchase Program. A summary of common stock repurchases for the three months ended March 31, 2017 is as follows: Total number of shares purchased Average price paid per share Total number of shares purchased as part of publicly announced plans or programs Maximum approximate dollar value of shares that may yet be purchased under the plans or programs March 300,000 $ 3.50 300,000 $33.1 million

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	10. Stock-Based Compensation The following table presents stock-based compensation expense included in the Company’s condensed consolidated statements of operations (in thousands): Three Months Ended March 31, (unaudited) 2017 2016 Stock-based compensation expense: Warrants for common stock to an officer $ 8,486 $ 12,090 Employee stock options 1,351 4,893 Employee restricted stock units 318 3,382 Non-employee restricted stock units (137 ) 197 $ 10,018 $ 20,562 Stock-based compensation expense in operating expenses: Research and development $ 92 $ 273 Selling, general and administrative 9,926 20,289 $ 10,018 $ 20,562 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 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 three months ended March 31, 2017 (in thousands, except for share and per share amounts): Number of Shares Weighted- Average Exercise Price Aggregate Intrinsic Value Weighted- Average Remaining Contractual Life (in years) Outstanding at December 31, 2016 6,307,384 $ 7.14 $ 19,100 6.4 Options exercised (614,136 ) $ 1.88 Outstanding at March 31, 2017 5,693,248 $ 7.71 $ 7,546 6.0 Vested and Exercisable at March 31, 2017 4,767,500 $ 8.78 $ 6,294 6.8 The aggregate intrinsic value of stock options exercised during the three months ended March 31, 2017 was $1.7 million. The total unrecognized stock-based compensation expense related to non-vested stock options as of March 31, 2017 is $7.7 million, which is expected to be recognized over a weighted-average period of 2.0 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 274,150 $ 3.92 Vested (6,625 ) $ 8.60 Forfeited (21,600 ) $ 10.66 Unvested balance at March 31, 2017 1,060,381 $ 11.48 During the three months ended March 31, 2017, the Company granted 196,900 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 8). As of March 31, 2017, there was $5.3 million of unrecognized stock-based compensation expense related to restricted stock units that is expected to be recognized over a weighted-average period of 3.2 years. Of that amount, $4.1 million of unrecognized expense is related to employee grants with a weighted-average period of 3.3 year and $1.2 million of unrecognized expense is related to non-employee grants with a weighted-average period of 3.0 years that is impacted by periodic mark-to-market adjustments. Warrants The following table summarizes the warrant activity for the three months ended March 31, 2017: Outstanding at December 31, 2016 17,768,314 Warrants exercised or forfeited — Outstanding at March 31, 2017 17,768,314 Vested and exercisable at March 31, 2017 14,620,764 The total unrecognized stock-based compensation expense related to non-vested warrants as of March 31, 2017 is $40.9 million, which is expected to be recognized over a weighted-average period of 1.3 years.

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	11. 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 three months ended March 31, 2017 and 2016, the Company recorded unrealized gains on its marketable securities in other comprehensive income, net of taxes. As a result, for the three months ended March 31, 2017 and 2016, the Company recorded a $6,000 and $0.1 million tax benefit, respectively, in the condensed consolidated statement of operations and $26,000 and $0.3 million, respectively, in other comprehensive income in the condensed consolidated balance sheet. The Company is operating in Korea. During the three months ended March 31, 2017 and 2016, the tax benefit related to Korea is $0.1 million and $0.1 million, respectively. 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 income taxes because of current and accumulated net operating losses.

Subsequent Event

Subsequent Event	3 Months Ended
	Mar. 31, 2017
Subsequent Events [Abstract]
Subsequent Events	12. Subsequent Events Viracta License Agreement 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. In consideration for the license, the Company will pay mid-single digit royalties to Viracta on net sales of products by the Company, its affiliates and sublicensees. The Company will pay Viracta development and sales milestone payments upon the first occurrence of each milestone event related to sales targets. Related Party Sublease Agreement In April 2017, the Company entered into a sublease agreement with Tensorcom, Inc. (sublessee) 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, Inc. 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. The sublease agreement can be terminated by either party by providing a thirty day written notice. The sublessee leases 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 annual 3% increase. Building Purchase Agreement 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 agreement contemplates the purchase of the building by January 31, 2018 or earlier dependent on the close of escrow. The Company made a deposit of $5 million to the escrow holder upon execution of the purchase agreement. The balance of the purchase price is due upon close of escrow. The closing of the transaction is contingent upon certain seller and buyer performance conditions. The deposit is refundable in the event of the seller’s default under the purchase agreement subject to termination fees of up to $38,000. The Company further entered into a lease agreement related to this facility which commences on May 1, 2017 and terminates on the earlier of close of escrow or termination of the purchase agreement. There is no monthly base rent under the lease.

Summary of Significant Accoun20

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2017
Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation The Company’s condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiary, Inex Bio, Inc., and have been prepared in accordance with GAAP. All intercompany amounts have been eliminated.
Liquidity	Liquidity As of March 31, 2017, the Company had an accumulated deficit of approximately $412.6 million. The Company also had negative cash flow from operations of approximately $10.1 million during the three months ended March 31, 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 the foreseeable future, 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	Accounting for 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	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 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 March 31, 2017 2016 Outstanding options 5,693,248 7,788,883 Outstanding restricted stock units 1,060,381 1,329,438 Outstanding warrants 17,768,314 17,817,687 Total 24,521,943 26,936,008 Amounts in the table above reflect the common stock equivalents of the noted instruments.
Recent Accounting Pronouncements	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. Adoption of ASU 2016-18 is not expected to 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. 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 In January 2016, the FASB issued ASU 2016-01, Financial Instruments – Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities. 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 Revenue Recognition doption of ASU 2014-09 is not expected to have a significant impact, the Company is currently evaluating the impact of the adoption in the Company’s consolidated financial statements and disclosures.

Summary of Significant Accoun21

Summary of Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 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 March 31, 2017 2016 Outstanding options 5,693,248 7,788,883 Outstanding restricted stock units 1,060,381 1,329,438 Outstanding warrants 17,768,314 17,817,687 Total 24,521,943 26,936,008 Amounts in the table above reflect the common stock equivalents of the noted instruments.

Financial Statement Details (Ta

Financial Statement Details (Tables)	3 Months Ended
	Mar. 31, 2017
Financial Statement Details [Abstract]
Prepaid Expenses and Other Current Assets	As of March 31, 2017 and December 31, 2016, prepaid expenses and other current assets consisted of (in thousands): March 31, 2017 December 31, 2016 (Unaudited) Prepaid services $ 1,436 $ 1,191 Interest receivable - marketable securities 1,232 1,484 Equipment deposits 482 482 Prepaid license fees 423 462 Prepaid insurance 371 531 Prepaid rent 360 360 Prepaid legal fees 350 350 Other 242 275 $ 4,896 $ 5,135
Property, Plant and Equipment, Net	As of March 31, 2017 and December 31, 2016, property, plant and equipment consisted of (in thousands): March 31, 2017 December 31, 2016 (Unaudited) Construction in progress $ 9,627 $ 6,939 Equipment 6,933 5,458 Building under financing lease 4,348 4,348 Leasehold improvements 2,370 2,367 Software 857 769 Furniture & fixtures 221 203 24,356 20,084 Accumulated depreciation (1,798 ) (1,178 ) $ 22,558 $ 18,906
Intangible Assets, Net	As of March 31, 2017 and December 31, 2016, intangible assets consisted of (in thousands): March 31, 2017 December 31, 2016 (Unaudited) Technology license $ 9,042 $ 9,042 Less accumulated amortization (4,521 ) (3,956 ) $ 4,521 $ 5,086
Other Assets	As of March 31, 2017 and December 31, 2016, other assets consisted of (in thousands): March 31, 2017 December 31, 2016 (Unaudited) Equipment not placed in service $ 326 $ 362 Restricted cash 179 179 Security deposit 139 137 Other 17 110 $ 661 $ 788
Accrued Expenses	As of March 31, 2017 and December 31, 2016, accrued expenses consisted of (in thousands): March 31, 2017 December 31, 2016 (Unaudited) Accrued bonus $ 2,379 $ 1,732 Accrued compensation 1,374 898 Accrued construction costs 1,261 1,243 Accrued professional and service fees 850 1,008 Accrued preclinical and clinical trial costs 434 662 Accrued software license fees 193 121 Other 367 200 $ 6,858 $ 5,864
Other Current Liabilities	As of March 31, 2017 and December 31, 2016, other current liabilities were made up of (in thousands): March 31, 2017 December 31, 2016 (Unaudited) Build-to-suit lease liability - current portion $ 290 $ 281 Financing obligation - current portion 261 253 Deferred rent - current portion 215 197 Other 173 160 $ 939 $ 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 months ended March 31, 2017 and 2016 (in thousands): Three Months Ended March 31, (Unaudited) 2017 2016 Interest income $ 1,354 $ 1,193 Investment amortization accretion expense, net (572 ) (426 ) Net realized gains (losses) on investments (3 ) 1 $ 779 $ 768

Cash Equivalents and Marketab23

Cash Equivalents and Marketable Securities (Tables)	3 Months Ended
	Mar. 31, 2017
Cash Equivalents And Marketable Securities [Abstract]
Schedule of Cash Equivalents and Marketable Securities Available-for-Sale	At March 31, 2017, the detail of the Company’s cash equivalents and marketable securities is as follows (in thousands): March 31, 2017 (unaudited) Amortized Cost Unrealized Gains Unrealized Losses Fair Value Current: Corporate debt securities $ 144,473 $ 38 $ (94 ) $ 144,417 Government sponsored securities 23,972 2 (14 ) 23,960 Foreign government bonds 8,998 — (1 ) 8,997 Current portion 177,443 40 (109 ) 177,374 Noncurrent: Corporate debt securities 54,946 88 (184 ) 54,850 Government sponsored securities 15,282 1 (43 ) 15,240 Foreign government bonds 1,404 — (7 ) 1,397 Noncurrent portion 71,632 89 (234 ) 71,487 Total $ 249,075 $ 129 $ (343 ) $ 248,861 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 March 31, 2017 and December 31, 2016 are as follows (in thousands): March 31, 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 $ 129,429 $ (277 ) $ — $ — Government sponsored securities 22,176 (57 ) — — Foreign government bonds 6,392 (9 ) — — Total $ 157,997 $ (343 ) $ — $ — 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 $ 150,320 $ (366 ) $ — $ — Government sponsored securities 17,204 (39 ) — — 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 March 31, (unaudited) 2017 2016 Gross realized gains $ 2 $ 58 Gross realized losses (5 ) (57 ) Net realized (losses) gains $ (3 ) $ 1

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2017
Fair Value Disclosures [Abstract]
Summary of Financial Assets Measured at Fair Value on Recurring Basis	The following table presents the Company’s hierarchy for its assets measured at fair value on a recurring basis as of March 31, 2017 and December 31, 2016 (in thousands): Fair Value Measurements at March 31, 2017 (unaudited) Total Level 1 Level 2 Level 3 Assets: Current: Corporate debt securities $ 144,417 $ — $ 144,417 $ — Government sponsored securities 23,960 — 23,960 — Foreign government bonds 8,997 — 8,997 — Noncurrent: Corporate debt securities 54,850 — 54,850 — Government sponsored securities 15,240 — 15,240 — Foreign government bonds 1,397 — 1,397 — Total assets measured at fair value $ 248,861 $ — $ 248,861 $ — All cash and cash equivalents reported in the condensed consolidated balance sheet as of March 31, 2017 are in depository institutions and 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.

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	3 Months Ended
	Mar. 31, 2017
Equity [Abstract]
Summary of Common Stock Repurchases	A summary of common stock repurchases for the three months ended March 31, 2017 is as follows: Total number of shares purchased Average price paid per share Total number of shares purchased as part of publicly announced plans or programs Maximum approximate dollar value of shares that may yet be purchased under the plans or programs March 300,000 $ 3.50 300,000 $33.1 million

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 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 statements of operations (in thousands): Three Months Ended March 31, (unaudited) 2017 2016 Stock-based compensation expense: Warrants for common stock to an officer $ 8,486 $ 12,090 Employee stock options 1,351 4,893 Employee restricted stock units 318 3,382 Non-employee restricted stock units (137 ) 197 $ 10,018 $ 20,562 Stock-based compensation expense in operating expenses: Research and development $ 92 $ 273 Selling, general and administrative 9,926 20,289 $ 10,018 $ 20,562
Summarizes Stock Option Activity	The following table summarizes stock option activity for the three months ended March 31, 2017 (in thousands, except for share and per share amounts): Number of Shares Weighted- Average Exercise Price Aggregate Intrinsic Value Weighted- Average Remaining Contractual Life (in years) Outstanding at December 31, 2016 6,307,384 $ 7.14 $ 19,100 6.4 Options exercised (614,136 ) $ 1.88 Outstanding at March 31, 2017 5,693,248 $ 7.71 $ 7,546 6.0 Vested and Exercisable at March 31, 2017 4,767,500 $ 8.78 $ 6,294 6.8
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 274,150 $ 3.92 Vested (6,625 ) $ 8.60 Forfeited (21,600 ) $ 10.66 Unvested balance at March 31, 2017 1,060,381 $ 11.48
Summary of Warrant Activity	The following table summarizes the warrant activity for the three months ended March 31, 2017: Outstanding at December 31, 2016 17,768,314 Warrants exercised or forfeited — Outstanding at March 31, 2017 17,768,314 Vested and exercisable at March 31, 2017 14,620,764

Description of Business and B27

Description of Business and Basis of Presentation - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	Jan. 01, 2016
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Accumulated deficit	$ (412,628)		$ (387,063)	$ 31,000
Net cash used in operating activities	$ (10,057)	$ (8,856)

Summary of Significant Accoun28

Summary of Significant Accounting Policies - Securities Excluded from the Computation of Potentially Dilutive Securities (Detail) - shares	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	24,521,943	26,936,008
Employee Stock Option
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	5,693,248	7,788,883
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	1,060,381	1,329,438
Outstanding Warrants
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	17,768,314	17,817,687

Financial Statement Details - P

Financial Statement Details - Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Financial Statement Details [Abstract]
Prepaid services	$ 1,436	$ 1,191
Interest receivable - marketable securities	1,232	1,484
Equipment deposits	482	482
Prepaid license fees	423	462
Prepaid insurance	371	531
Prepaid rent	360	360
Prepaid legal fees	350	350
Other	242	275
Total prepaid expenses and other current assets	$ 4,896	$ 5,135

Financial Statement Details -30

Financial Statement Details - Property, Plant and Equipment, Net (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	$ 24,356	$ 20,084
Accumulated depreciation	(1,798)	(1,178)
Property, plant and equipment, net	22,558	18,906
Construction in Progress
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	9,627	6,939
Equipment
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	6,933	5,458
Building Under Financing Lease
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	4,348	4,348
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	2,370	2,367
Software
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	857	769
Furniture And Fixtures
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	$ 221	$ 203

Financial Statement Details - A

Financial Statement Details - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Financial Statement Details [Line Items]
Depreciation expense related to property, plant and equipment	$ 600,000	$ 37,000
Property, plant and equipment, gross	24,356,000		$ 20,084,000
Amortization expense	600,000	400,000
Impairment loss on recognized investments	0	$ 0
El Segundo California
Financial Statement Details [Line Items]
Non cash build to suit lease asset	5,100,000
Building Under Financing Lease
Financial Statement Details [Line Items]
Property, plant and equipment, gross	$ 4,348,000		$ 4,348,000

Financial Statement Details - I

Financial Statement Details - Intangible Assets, Net (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Finite Lived Intangible Assets [Line Items]
Intangible assets, net	$ 4,521	$ 5,086
Technology License
Finite Lived Intangible Assets [Line Items]
Total intangible assets	9,042	9,042
Less accumulated amortization	(4,521)	(3,956)
Intangible assets, net	$ 4,521	$ 5,086

Financial Statement Details - O

Financial Statement Details - Other Assets (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Financial Statement Details [Abstract]
Equipment not placed in service	$ 326	$ 362
Restricted cash	179	179
Security deposit	139	137
Other	17	110
Other Assets Noncurrent	$ 661	$ 788

Financial Statement Details -34

Financial Statement Details - Accrued Expenses (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Financial Statement Details [Abstract]
Accrued bonus	$ 2,379	$ 1,732
Accrued compensation	1,374	898
Accrued construction costs	1,261	1,243
Accrued professional and service fees	850	1,008
Accrued preclinical and clinical trial costs	434	662
Accrued software license fees	193	121
Other	367	200
Accrued Liabilities Current	$ 6,858	$ 5,864

Financial Statement Details -35

Financial Statement Details - Other Current Liabilities (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Financial Statement Details [Abstract]
Build-to-suit lease liability - current portion	$ 290	$ 281
Financing obligation - current portion	261	253
Deferred rent - current portion	215	197
Other	173	160
Other current liabilities	$ 939	$ 891

Financial Statement Details -36

Financial Statement Details - Investment Income, Net (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Financial Statement Details [Abstract]
Interest income	$ 1,354	$ 1,193
Investment amortization accretion expense, net	(572)	(426)
Net realized gains (losses) on investments	(3)	1
Investment income, net	$ 779	$ 768

Cost Method Investment - Additi

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 | Scenario, Forecast | Maximum
Schedule Of Cost Method Investments [Line Items]
Option to purchase additional shares under cost method investment	$ 8,500,000

Cash Equivalents and Marketab38

Cash Equivalents and Marketable Securities - Additional Information (Detail)	3 Months Ended	12 Months Ended
	Mar. 31, 2017USD ($)Security	Dec. 31, 2016USD ($)
Schedule Of Available For Sale Securities [Line Items]
Available for sale securities maturity period	4 years 6 months
Cash equivalent portions included in current fair values	$ 0
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		$ 2,000,000
Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Number of available-for-sale securities in unrealized loss positions | Security	73

Cash Equivalents and Marketab39

Cash Equivalents and Marketable Securities - Schedule of Cash Equivalents and Marketable Securities Available-for-Sale (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 249,075	$ 280,698
Unrealized Gains	129	134
Unrealized Losses	(343)	(418)
Fair Value	248,861	280,414
Current Assets
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	177,443	192,861
Unrealized Gains	40	61
Unrealized Losses	(109)	(79)
Fair Value	177,374	192,843
Current Assets | Government Sponsored Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	23,972	22,252
Unrealized Gains	2	21
Unrealized Losses	(14)	(1)
Fair Value	23,960	22,272
Current Assets | Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	144,473	165,605
Unrealized Gains	38	40
Unrealized Losses	(94)	(76)
Fair Value	144,417	165,569
Current Assets | Foreign Government Bonds
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	8,998	5,004
Unrealized Gains	0	0
Unrealized Losses	(1)	(2)
Fair Value	8,997	5,002
Noncurrent Assets
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	71,632	87,837
Unrealized Gains	89	73
Unrealized Losses	(234)	(339)
Fair Value	71,487	87,571
Noncurrent Assets | Government Sponsored Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	15,282	17,018
Unrealized Gains	1	2
Unrealized Losses	(43)	(38)
Fair Value	15,240	16,982
Noncurrent Assets | Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	54,946	69,414
Unrealized Gains	88	71
Unrealized Losses	(184)	(290)
Fair Value	54,850	69,195
Noncurrent Assets | Foreign Government Bonds
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	1,404	1,405
Unrealized Gains	0	0
Unrealized Losses	(7)	(11)
Fair Value	$ 1,397	$ 1,394

Cash Equivalents and Marketab40

Cash Equivalents and Marketable Securities - Available-for-Sale Investments in Unrealized Loss Position (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Schedule Of Available For Sale Securities [Line Items]
Available-for-Sale Investments, Less than 12 months, Estimated Fair Value	$ 157,997	$ 173,920
Available-for-Sale Investments, Less than 12 months, Gross Unrealized Losses	(343)	(418)
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
Government Sponsored Securities
Schedule Of Available For Sale Securities [Line Items]
Available-for-Sale Investments, Less than 12 months, Estimated Fair Value	22,176	17,204
Available-for-Sale Investments, Less than 12 months, Gross Unrealized Losses	(57)	(39)
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	129,429	150,320
Available-for-Sale Investments, Less than 12 months, Gross Unrealized Losses	(277)	(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
Foreign Government Bonds
Schedule Of Available For Sale Securities [Line Items]
Available-for-Sale Investments, Less than 12 months, Estimated Fair Value	6,392	6,396
Available-for-Sale Investments, Less than 12 months, Gross Unrealized Losses	(9)	(13)
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

Cash Equivalents and Marketab41

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
	Mar. 31, 2017	Mar. 31, 2016
Cash Equivalents And Marketable Securities [Abstract]
Available-for-sale Securities, Gross Realized Gains	$ 2	$ 58
Available-for-sale Securities, Gross Realized Losses	(5)	(57)
Available-for-sale Securities, Net Realized Gains	$ (3)	$ 1

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Financial Assets Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	$ 248,861	$ 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	248,861	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	8,997	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	23,960	22,272
Current Assets | Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	144,417	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 | 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	8,997	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	23,960	22,272
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	144,417	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 | 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	1,397	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	15,240	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	54,850	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	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	1,397	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	15,240	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	54,850	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	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

Fair Value Measurements - Sum43

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

Commitment and Contingencies -

Commitment and Contingencies - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2017USD ($)Patient	Mar. 31, 2016USD ($)	Dec. 31, 2016USD ($)	Sep. 30, 2016USD ($)ft²	Nov. 30, 2015ft²
Commitments And Contingencies [Line Items]
Rent expense	$ 700,000	$ 700,000
Property, plant and equipment, gross	24,356,000		$ 20,084,000
Building Under Financing Lease
Commitments And Contingencies [Line Items]
Property, plant and equipment, gross	4,348,000		$ 4,348,000
El Segundo California
Commitments And Contingencies [Line Items]
Non cash build to suit lease asset	$ 5,100,000
Altor
Commitments And Contingencies [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
Doug St, LLC
Commitments And Contingencies [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.
Optional extended lease term	3 years
Base rent - monthly	$ 100,000
Percentage of annual increase of base rent	3.00%
Annual percentage increases to base rent commencement date	Jul. 31, 2017
Costs incurred	$ 4,300,000
Non cash build to suit lease asset	$ 5,100,000
Property and equipment estimated useful lives	39 years
Doug St, LLC | El Segundo California
Commitments And Contingencies [Line Items]
Number of square foot of facility leased | ft²				24,250
Doug St, LLC | Research and Development
Commitments And Contingencies [Line Items]
Rent expense	$ 100,000
NantWorks
Commitments And Contingencies [Line Items]
Number of square foot of facility leased | ft²					9,500
Period of agreement	The license was effective in May 2015 and extends through December 2020. The 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.
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
Costs incurred				$ 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
NantWorks | Research and Development
Commitments And Contingencies [Line Items]
Rent expense	$ 47,000	$ 100,000

Related Party Agreements - Addi

Related Party Agreements - Additional Information (Detail)	1 Months Ended			3 Months Ended
	Apr. 30, 2017USD ($)	Apr. 30, 2016USD ($)	Sep. 30, 2015USD ($)	Mar. 31, 2017USD ($)	Mar. 31, 2016USD ($)	Feb. 28, 2017USD ($)	Dec. 31, 2016USD ($)	Sep. 30, 2016ft²	Aug. 31, 2016	Nov. 30, 2015ft²
Related Party Transaction [Line Items]
Prepaid expenses and other current assets				$ 4,896,000			$ 5,135,000
Research and development				9,248,000	$ 4,955,000
Due to related parties				2,124,000			$ 1,753,000
Selling, general and administrative				16,227,000	26,667,000
VivaBioCell S.p.A.
Related Party Transaction [Line Items]
Prepaid expenses and other current assets						$ 600,000
Research and development				$ 100,000
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
Doug St, LLC | El Segundo California
Related Party Transaction [Line Items]
Number of square foot of facility leased | ft²								24,250
Doug St, LLC | Research and Development
Related Party Transaction [Line Items]
Rent expense				100,000
Altor
Related Party Transaction [Line Items]
Research and development charges incurred for supplies or milestone				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		$ 100,000	$ 0
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
NantWorks
Related Party Transaction [Line Items]
Number of square foot of facility leased | ft²										9,500
Base rent - monthly				$ 47,000
Percentage of annual increase of base rent				3.00%
Annual percentage increases to base rent commencement date				Jan. 31, 2017
Due to related parties				$ 2,100,000
NantWorks | Shared Services Agreement
Related Party Transaction [Line Items]
Research and development				800,000	$ 300,000
Selling, general and administrative				700,000	800,000
NantWorks | Reimbursements | Shared Services Agreement
Related Party Transaction [Line Items]
Research and development				100,000
Selling, general and administrative				100,000
NantWorks | Research and Development
Related Party Transaction [Line Items]
Rent expense				47,000	100,000
NantOmnics
Related Party Transaction [Line Items]
Research and development				0	$ 100,000
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
NantCell
Related Party Transaction [Line Items]
Research and development				$ 300,000
Initial term of agreement entered into with the related party by the entity				5 years
Related party, agreement renewal term				1 year
Non refundable upfront payment			$ 500,000

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016	Nov. 30, 2015
Equity [Abstract]
Total amount authorized for repurchase			$ 50,000,000
Repurchase of common stock, shares	300,000	2,157,944
Repurchase of common stock, par value	$ 3.50
Repurchase of common stock, value	$ 1,050,000	$ 15,800,000
Remained authorized shares for repurchase	$ 33,100,000

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Common Stock Repurchases (Detail) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Equity [Abstract]
Total number of shares purchased	300,000	2,157,944
Average price paid per share	$ 3.50
Total number of shares purchased as part of publicly announced plans or programs	300,000
Maximum approximate dollar value of shares that may yet be purchased under the plans or programs	$ 33,100,000

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock Based Compensation Expenses Related to Statement of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 10,018	$ 20,562
Warrants For Common Stock | Officer
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	8,486	12,090
Employee Stock Option
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	1,351	4,893
Employee Restricted Stock Units
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	318	3,382
Non Employee Restricted Stock Units
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	(137)	197
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	92	273
Selling, General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 9,926	$ 20,289

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	Jan. 01, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Accumulated deficit	$ (412,628)		$ (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	$ 40,900
Weighted-average period for recognition	1 year 3 months 18 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	$ 7,700
Weighted-average period for recognition	2 years
Employee Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average period for recognition	3 years 3 months 18 days
Number of Shares, Granted	196,900
Unrecognized compensation cost related to non-vested stock options	$ 4,100
Non 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	77,250
Unrecognized compensation cost related to non-vested stock options	$ 1,200
Employee Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average period for recognition	3 years 2 months 12 days
Number of Shares, Granted	274,150
Unrecognized compensation cost related to non-vested stock options	$ 5,300
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 - St50

Stock-Based Compensation - Stock Option Activity (Detail) - Employee Stock Option - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Number of Shares
Stock Options, Beginning Balance	6,307,384
Stock Options, Options exercised	(614,136)
Stock Options, Ending Balance	5,693,248	6,307,384
Stock Options, Vested and Exercisable	4,767,500
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	$ 8.78
Aggregate Intrinsic Value
Aggregate Intrinsic Value, Outstanding	$ 7,546	$ 19,100
Aggregate Intrinsic Value, Vested and Exercisable	$ 6,294
Weighted Average Remaining Contractual Life
Weighted Average Remaining Contractual Life, Outstanding	6 years	6 years 4 months 24 days
Weighted Average Remaining Contractual Life, Vested and Exercisable	6 years 9 months 18 days

Stock-Based Compensation - Rest

Stock-Based Compensation - Restricted Stock Units Activity (Detail) - Outstanding Restricted Stock Units	3 Months Ended
	Mar. 31, 2017$ / sharesshares
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	274,150
Number of Shares, Vested | shares	(6,625)
Number of Shares, Forfeited | shares	(21,600)
Number of Shares, Unvested, Ending balance | shares	1,060,381
Weighted-Average Grant Date Fair Value, Unvested, beginning balance | $ / shares	$ 13.98
Weighted-Average Grant Date Fair Value, Granted | $ / shares	3.92
Weighted-Average Grant Date Fair Value, Vested | $ / shares	8.60
Weighted-Average Grant Date Fair Value, Forfeited | $ / shares	10.66
Weighted-Average Grant Date Fair Value, Unvested, ending balance | $ / shares	$ 11.48

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Warrant Activity (Detail) - Outstanding Warrants	3 Months Ended
	Mar. 31, 2017shares
Warrant [Line Items]
Warrants, Beginning Balance	17,768,314
Warrants exercised or forfeited	0
Warrants, Ending Balance	17,768,314
Warrants, Vested and exercisable Ending Balance	14,620,764

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Income Tax [Line Items]
Federal statutory tax rate	34.00%
Company's effective tax rate	0.00%
Tax benefit	$ 6,000	$ 100,000
Tax benefit in other comprehensive income	26,000	300,000
Korea
Income Tax [Line Items]
Tax benefit	$ 100,000	$ 100,000

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) - Subsequent Event	1 Months Ended
	Apr. 30, 2017USD ($)ft²	Apr. 27, 2017ft²
San Diego California | Tensorcom, Inc
Subsequent Event [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%
El Segundo California | Agreement to Purchase Commercial Building
Subsequent Event [Line Items]
Base rent - monthly	$ 0
Area of Land | ft²	36,000
Escrow deposit	$ 5,000,000
Purchase agreement, termination fees	$ 38,000