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Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2019	May 03, 2019
Document Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Trading Symbol	NK
Entity Registrant Name	NANTKWEST, INC.
Entity Central Index Key	0001326110
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Emerging Growth Company	true
Entity Small Business	true
Entity Ex Transition Period	true
Entity Common Stock, Shares Outstanding		98,674,153

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 22,279	$ 16,821
Restricted cash	1,200	0
Due from related parties	86	90
Prepaid expenses and other current assets	13,595	13,810
Marketable debt securities, available-for-sale	76,270	57,328
Notes receivable, held-to-maturity	0	723
Total current assets	113,430	88,772
Marketable debt securities, noncurrent	4,190	5,701
Property, plant and equipment, net	67,921	76,885
Operating lease right-of-use assets, net	13,155	0
Investment in equity securities	9,251	8,500
Intangible assets, net	0	565
Other assets	314	1,527
Total assets	208,261	181,950
Current liabilities:
Accounts payable	2,804	2,793
Accrued expenses	20,242	21,104
Due to related parties	1,531	1,696
Other current liabilities	3,124	1,667
Total current liabilities	27,701	27,260
Operating lease liability, less current portion	12,752	0
Financing obligation, less current portion	0	5,945
Deferred rent	0	2,739
Total liabilities	40,453	35,944
Commitments and contingencies (Note 8)	0	0
Stockholders’ equity
Common stock, $0.0001 par value; 500,000,000 shares authorized; 98,674,153 and 79,087,734 issued and outstanding as of March 31, 2019 and December 31, 2018	10	8
Additional paid-in capital	781,790	741,246
Accumulated other comprehensive loss	(206)	(267)
Accumulated deficit	(613,786)	(594,981)
Total stockholders’ equity	167,808	146,006
Total liabilities and stockholders’ equity	$ 208,261	$ 181,950

Condensed Consolidated Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Revenue	$ 5	$ 5
Operating expenses:
Research and development (including amounts with related parties)	12,598	13,991
Selling, general and administrative (including amounts with related parties)	5,742	14,298
Total operating expenses	18,340	28,289
Loss from operations	(18,335)	(28,284)
Other income (expense):
Investment income, net	370	505
Interest expense (including amounts to related parties)	(3)	(33)
Other income, net (including amounts with related parties)	47	169
Total other income	414	641
Loss before income taxes	(17,921)	(27,643)
Income tax benefit	36	124
Net loss	$ (17,885)	$ (27,519)
Net loss per share:
Basic and diluted	$ (0.22)	$ (0.35)
Weighted-average number of shares during the period:
Basic and diluted	81,261,302	79,036,614

Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning Balance at Dec. 31, 2017	$ 218,844	$ 8	$ 717,930	$ (381)	$ (498,713)
Beginning Balance, Shares at Dec. 31, 2017		79,021,878
Stock-based compensation expense	9,073	$ 0	9,073	0	0
Exercise of warrants	23	$ 0	23	0	0
Exercise of warrants, Shares		14,270
Vesting of restricted stock units (RSUs)	0	$ 0	0	0	0
Vesting of restricted stock units (RSUs), Shares		70,200
Employee payroll taxes withheld related to vesting of RSUs and exercise of stock options	(73)	$ 0	(73)	0	0
Employee payroll taxes withheld related to vesting of RSUs and exercise of stock options, Shares		(18,148)
Cumulative effect of the adoption of the new standard \| Accounting Standards Update 2014-09	186	$ 0	0	0	186
Other comprehensive income (loss), net	(174)	0	0	(174)	0
Net loss	(27,519)	0	0	0	(27,519)
Ending Balance at Mar. 31, 2018	200,360	$ 8	726,953	(555)	(526,046)
Ending Balance, Shares at Mar. 31, 2018		79,088,200
Beginning Balance at Dec. 31, 2018	$ 146,006	$ 8	741,246	(267)	(594,981)
Beginning Balance, Shares at Dec. 31, 2018	79,087,734	79,087,734
Stock-based compensation expense	$ 1,351	$ 0	1,351	0	0
Exercise of warrants	35,151	$ 2	35,149	0	0
Exercise of warrants, Shares		17,589,250
Exercise of stock options	4,070	$ 0	4,070	0	0
Exercise of stock options, Shares		1,986,300
Vesting of restricted stock units (RSUs)	0	$ 0	0	0	0
Vesting of restricted stock units (RSUs), Shares		49,775
Employee payroll taxes withheld related to vesting of RSUs and exercise of stock options	(26)	$ 0	(26)	0	0
Employee payroll taxes withheld related to vesting of RSUs and exercise of stock options, Shares		(38,906)
Cumulative effect of the adoption of the new standard \| Accounting Standards Update 2016-02	(920)	$ 0	0	0	(920)
Other comprehensive income (loss), net	61	0	0	61	0
Net loss	(17,885)	0	0	0	(17,885)
Ending Balance at Mar. 31, 2019	$ 167,808	$ 10	$ 781,790	$ (206)	$ (613,786)
Ending Balance, Shares at Mar. 31, 2019	98,674,153	98,674,153

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Operating activities:
Net loss	$ (17,885)	$ (27,519)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	2,395	1,623
Stock-based compensation expense	1,351	9,073
Amortization of operating lease right-of-use assets	624	0
Amortization of net premiums on marketable debt securities	41	201
Non-cash interest items, net	(95)	149
Deferred income tax benefit	0	(124)
Loss on disposal of assets	0	36
Changes in operating assets and liabilities:
Prepaid expenses, other current assets and other assets	88	(847)
Operating lease right-of-use assets	(247)	0
Accounts payable	670	117
Accrued expenses and other liabilities	797	1,878
Due to related parties	(162)	20
Operating lease liability, less current portion	(655)	0
Deferred rent	0	(118)
Net cash used in operating activities	(13,078)	(15,511)
Investing activities:
Purchases of property, plant and equipment	(2,104)	(4,902)
Purchases of marketable debt securities, available-for-sale	(50,273)	(32,038)
Sales/maturities of marketable debt securities	32,918	39,860
Net cash (used in) provided by investing activities	(19,459)	2,920
Financing activities:
Principal payments of financing lease obligations	0	(65)
Proceeds from exercise of stock options and warrants	39,221	23
Net share settlement for RSU vesting and option exercises	(26)	(43)
Net cash provided by (used in) financing activities	39,195	(85)
Net increase (decrease) in cash, cash equivalents, and restricted cash	6,658	(12,676)
Cash, cash equivalents and restricted cash, beginning of period	17,000	24,051
Cash, cash equivalents, and restricted cash, end of period	23,658	11,375
Reconciliation of cash, cash equivalents, and restricted cash at end of period:
Cash and cash equivalents	22,279
Restricted cash	1,379	179
Cash, cash equivalents, and restricted cash, end of period	23,658	11,375
Supplemental disclosure of cash flow information:
Interest	3	34
Income taxes	0	0
Supplemental disclosure of non-cash investing and financing activities:
Property and equipment purchases included in accounts payable, accrued expenses, and other liabilities	2,031	5,930
Conversion of Viracta convertible notes and accrued interest into investment in equity securities of Viracta (Note 4)	751	0
Unrealized gains (losses) on marketable debt securities	118	(174)
Cashless exercise of stock options	$ 29	$ 0

Summary of Significant Accounting Policies

3 Months Ended

Mar. 31, 2019

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

There have been no material changes in our significant accounting policies other than the adoption of accounting pronouncements described below under Application of New or Revised Accounting Standards – Adopted, as compared to the significant accounting policies described in our Annual Report on Form 10‑K for the year ended December 31, 2018.

Basis of Presentation

The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America, or U.S. GAAP. The condensed consolidated financial statements reflect all adjustments which are, in the opinion of management, necessary to present fairly the results for the interim periods presented and have been prepared on the same basis as the audited consolidated financial statements for the fiscal year ended December 31, 2018.

The unaudited condensed consolidated financial statements do not include all information and notes necessary for a complete presentation of results of income, comprehensive income, financial position, and cash flows in conformity with U.S. GAAP. Accordingly, these financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto for the fiscal year ended December 31, 2018 included in our Annual Report on Form 10‑K. Interim operating results are not necessarily indicative of operating results for the full year. The year-end consolidated balance sheet data was derived from our audited financial statements, but does not include all disclosures required by U.S. GAAP.

Principles of Consolidation and Equity Investments

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

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

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

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

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

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

Use of Estimates

The preparation of condensed consolidated financial statements in conformity with U.S. GAAP requires management to make certain estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. On an ongoing basis, we evaluate our estimates, including those related to valuation of equity-based awards, valuation of the allowance for deferred tax assets, preclinical and clinical trial accruals, impairment assessments, and the useful lives of long-lived assets. We base our estimates on historical experience and on various other market-specific and relevant assumptions that we believe to be reasonable under the circumstances. Actual results could differ from those estimates.

Risks and Uncertainties

Contingencies

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

Concentration of Credit Risk and Other Risks and Uncertainties

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

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

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

Lease Obligations

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

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

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

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

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

Basic and Diluted Net Loss per Share of Common Stock

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

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

	As of March 31,
	2019		2018
Outstanding options		4,506,950		5,693,250
Outstanding RSUs		821,936		874,164
Outstanding warrants		—		17,706,818
Total		5,328,886		24,274,232

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

Recent Accounting Pronouncements

Application of New or Revised Accounting Standards – Adopted

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

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

In February 2018, the FASB issued Accounting Standards Update, or ASU, 2018‑02, Income Statement—Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income, which provides financial statement preparers with an option to reclassify stranded tax effects within accumulated other comprehensive income or loss to retained earnings or accumulated deficit in each period in which the effect of the change in the U.S. federal corporate income tax rate in the Tax Cuts and Jobs Act is recorded. Our adoption of this standard on January 1, 2019 did not have a material impact on our condensed consolidated financial statements and disclosures.

Application of New or Revised Accounting Standards – Not Yet Adopted

In June 2016, the FASB issued ASU 2016‑13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. The new guidance supersedes existing U.S. GAAP for measuring and recording of credit losses on financial assets measured at amortized cost by replacing the incurred-loss model with an expected-loss model. Accordingly, these financial assets will be presented at the net amount expected to be collected. This new standard also requires that credit losses related to available-for-sale debt securities be recorded as an allowance through net income rather than reducing the carrying amount under the current, other-than-temporary-impairment model. The new guidance is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019, but may be adopted earlier. With certain exceptions, adjustments are to be applied using a modified-retrospective approach by reflecting adjustments through a cumulative-effect impact on retained earnings as of the beginning of the fiscal year of adoption. We are currently evaluating the impact that this new standard will have on our consolidated financial statements and we intend to adopt the standard on January 1, 2020. However, as the impact is dependent upon the investments held as of the adoption date, it is not possible for us to quantify the impact until the date of adoption.

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

Financial Statement Details

3 Months Ended

Mar. 31, 2019

Financial Statement Details [Abstract]

Financial Statement Details

3. Financial Statement Details

Prepaid expenses and other current assets

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

	March 31, 2019		December 31, 2018
	(Unaudited)
Insurance claim receivables	$	11,144	$	10,882
Interest receivable - marketable debt securities		563		473
Prepaid supplies		431		532
Prepaid rent		368		536
Prepaid insurance		344		343
Prepaid services		341		230
Prepaid equipment maintenance		188		329
Insurance premium financing asset		85		339
Prepaid license fees		51		104
Other		80		42
	$	13,595	$	13,810

Property, plant and equipment, net

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

	March 31, 2019			December 31, 2018
	(Unaudited)
Construction in progress	$	—		$	2,480
Leasehold improvements		33,540			4,087
Buildings		23,463			59,356
Equipment		21,222			20,878
Software		1,264			1,264
Furniture & fixtures		369			381
		79,858			88,446
Accumulated depreciation		(11,937	)		(11,561	)
	$	67,921		$	76,885

Depreciation expense related to property, plant and equipment was $1.8 million and $1.1 million for the three months ended March 31, 2019 and 2018, respectively.

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

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

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

Intangible assets, net

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

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

Amortization expense was $0.6 million and $0.6 million for the three months ended March 31, 2019 and 2018, respectively. Amortization of our technology license is included in research and development expense on the condensed consolidated statements of operations.

Other assets

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

	March 31, 2019		December 31, 2018
	(Unaudited)
Prepaid rent	$	—	$	1,205
Restricted cash		179		179
Security deposit		113		113
Other		22		30
	$	314	$	1,527

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

Accrued expenses

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

	March 31, 2019		December 31, 2018
	(Unaudited)
Litigation settlement accruals	$	12,500	$	12,000
Accrued bonus		2,654		2,079
Accrued construction costs		1,379		3,341
Accrued compensation		1,272		943
Accrued preclinical and clinical trial costs		1,082		704
Accrued professional and service fees		806		912
Accrued laboratory equipment and supplies		277		678
Accrued franchise, sales/use and property taxes		173		250
Other		99		197
	$	20,242	$	21,104

Other current liabilities

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

	March 31, 2019		December 31, 2018
	(Unaudited)
Operating lease liability - current portion	$	2,938	$	—
Financing obligation - current portion		85		965
Deferred rent - current portion		—		598
Other		101		104
	$	3,124	$	1,667

Investment income, net

Net investment income is as follows for the three months ended March 31, 2019 and 2018 (in thousands):

	Three Months Ended March 31,
	2019			2018
	(Unaudited)
Interest income	$	410		$	704
Investment amortization accretion expense, net		(40	)		(201	)
Net realized gains on investments		—			2
	$	370		$	505

Interest income includes interest from marketable debt securities, notes receivable, and interest from our bank deposits. We did not recognize an impairment loss on any investments for the three months ended March 31, 2019 and 2018.

Financial Instruments Investments in Debt Securities

3 Months Ended

Mar. 31, 2019

Cash Equivalents And Marketable Securities [Abstract]

Financial Instruments Investments in Debt Securities

5. Financial Instruments – Investments in Debt Securities

At March 31, 2019, our investments in debt securities, excluding $1.2 million of corporate debt securities included in cash and cash equivalents, are detailed below (in thousands):

	March 31, 2019
	(Unaudited)
	Weighted- Average Remaining Contractual Life (in years)		Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Current:
Available-for-sale
Corporate debt securities		0.4	$	69,330	$	4	$	(76	)	$	69,258
Commercial paper		0.2		3,489		1		—			3,490
Foreign government bonds		0.6		3,248		—		(2	)		3,246
Government sponsored securities		0.3		277		—		(1	)		276
Current portion		0.4		76,344		5		(79	)		76,270
Noncurrent:
Available-for-sale
Corporate debt securities		2.5		1,501		—		(31	)		1,470
Government sponsored securities		1.2		2,755		—		(35	)		2,720
Noncurrent portion		1.7		4,256		—		(66	)		4,190
Total		0.4	$	80,600	$	5	$	(145	)	$	80,460

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

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

Available-for-sale investments that had been in an unrealized loss position for less than 12 months and for more than 12 months at March 31, 2019 and December 31, 2018 were as follows (in thousands):

	March 31, 2019
	(Unaudited)
	Less than 12 months					More than 12 months
	Estimated Fair Value		Gross Unrealized Losses			Estimated Fair Value		Gross Unrealized Losses
Corporate debt securities	$	34,111	$	(9	)	$	12,465	$	(99	)
Government sponsored securities		—		—			2,720		(35	)
Foreign government bonds		3,246		(2	)		—		—
Total	$	37,357	$	(11	)	$	15,185	$	(134	)

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

At March 31, 2019, 46 of the securities are in an unrealized loss position. We evaluated our securities for other-than-temporary impairment and concluded that the decline in value was primarily caused by current economic and market conditions. We do not intend to sell the investments and it is not more likely than not that we will be required to sell the investments before recovery of their amortized cost bases. Therefore, we did not recognize any other-than-temporary impairment loss during the three months ended March 31, 2019.

Realized gains and losses on sales or maturities of available-for-sale debt securities during the three months ended March 31, 2019 and 2018 were immaterial.

Fair Value Measurements

3 Months Ended

Mar. 31, 2019

Fair Value Disclosures [Abstract]

Fair Value Measurements

6. Fair Value Measurements

Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date, based on our principal or, in absence of a principal, most advantageous market for the specific asset or liability.

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

The three tiers are defined as follows:

•

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

•

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

•

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

During the periods presented, no transfers were made into or out of the Level 1, 2 or 3 categories. We will continue to review the fair value inputs on quarterly basis.

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

Recurring Valuations

The following tables present our assets that are measured at fair value on a recurring basis as of March 31, 2019 and December 31, 2018 (in thousands):

	Fair Value Measurements at March 31, 2019
	(Unaudited)
	Total		Level 1		Level 2		Level 3
Assets:
Current:
Cash and cash equivalents	$	22,279	$	21,031	$	1,248	$	—
Corporate debt securities		69,258		—		69,258		—
Commercial paper		3,490		—		3,490		—
Foreign government bonds		3,246		—		3,246		—
Government sponsored securities		276		—		276		—
Noncurrent:
Government sponsored securities		2,720		—		2,720		—
Corporate debt securities		1,470		—		1,470		—
Total assets measured at fair value	$	102,739	$	21,031	$	81,708	$	—

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

Non-recurring Valuations

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

Commitment and Contingencies

3 Months Ended

Mar. 31, 2019

Commitments And Contingencies Disclosure [Abstract]

Commitments and contingencies

8. Commitments and Contingencies

Contingencies

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

Securities Litigation

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

Under the terms of the settlement, which is subject to final approval by the court, we agreed to pay $12.0 million to the plaintiffs as full and complete settlement of the litigation. We are responsible for $1.2 million of the settlement amount, which was recognized in selling, general and administrative expense during the third quarter of 2018, while the remaining $10.8 million is being fully funded by our insurance carriers under our directors’ and officers’ insurance policy. We and the insurance carriers paid the settlement amount into a settlement fund in January 2019, and as of March 31, 2019, our share of the settlement is included in restricted cash on the condensed consolidated balance sheets.

Management intends to continue to vigorously defend these proceedings. If for some reason the settlement is not approved and the company is ultimately found liable, the liability could have a material adverse effect on the company’s consolidated financial statements for the period or periods in which it is incurred.

Stipulation of Settlement

In early April 2019, following board approval, which occurred in late March 2019, we entered into a settlement agreement, or the Stipulation of Settlement, with three stockholders of the company, each of whom had submitted a stockholder demand for the board to take action to remedy purported harm to the company resulting from certain alleged wrongful conduct concerning, among other things, disclosures about Dr. Soon-Shiong’s compensation and a related-party lease agreement. The Stipulation of Settlement calls for us to adopt certain governance changes, and for the three stockholders to file a stockholder derivative action in the Superior Court of the State of California, County of San Diego, followed by an application for court approval of the Stipulation of Settlement. Following entry of a preliminary approval order by the court, we will provide stockholders with notice of the settlement and a final settlement hearing in accordance with the Stipulation of Settlement. Due to the foregoing, the company determined that it is probable that a liability has been incurred as of the date of the financial statements and that the amount of loss can be reasonably estimated.

Under the terms of the Stipulation of Settlement, which remains subject to preliminary and final approval by the court, we have agreed to pay an attorney’s fee of $0.5 million to the plaintiffs as part of the settlement. Of that amount, we are responsible for half, which has been recognized in selling, general and administrative expense on the condensed consolidated statements of operations, while the other half will be fully funded by our insurance carriers.

Insurance Recoveries

We have reflected our right to insurance recoveries, limited to the extent of incurred or probable losses, as a receivable when such recoveries have been agreed to with our third-party insurers and receipt is deemed probable. This includes instances where our third-party insurers have agreed to pay, on our behalf, certain legal defense costs and settlement amounts directly to applicable law firms and a settlement fund. The amount of such receivable recorded at March 31, 2019 and December 31, 2018 was $11.1 million and $10.9 million, respectively, and is included in prepaid expenses and other current assets on the condensed consolidated balance sheets.

Contractual Obligations - Leases

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

	Balance January 1, 2019		Balance March 31, 2019
Operating lease right-of-use assets, net	$	13,532	$	13,155
Other current liabilities	$	2,960	$	2,938
Operating lease liability, less current portion	$	13,407	$	12,752

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

Operating lease expense of $1.2 million, including variable lease costs of $0.2 million, was recorded in research and development expense and selling, general and administrative expense on the condensed consolidated statements of operations for the three months ended March 31, 2019. The weighted-average remaining lease term as of January 1, 2019 and March 31, 2019 was 5.4 years and 5.2 years respectively. The weighted-average discount rate as of January 1, 2019 and March 31, 2019 was 9%. For the three months ending March 31, 2019, cash outflows from operating leases was $1.3 million.

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

Years ending December 31:	Operating Leases (a)
2019 (excluding the three months ended March 31, 2019)	$	3,102
2020		4,080
2021		3,438
2022		3,538
2023		2,545
Thereafter		2,813
Total future minimum lease payments		19,516
Less: Interest		3,826
Present value of operating lease liabilities	$	15,690

(a)

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

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

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

In March 2016, we entered into a lease agreement for an approximately 7,893 square foot facility in Woburn, Massachusetts, for a research and development laboratory, related office and other related uses. The term of the lease is 48 months commencing on April 29, 2016. In June 2016, the lease was amended to add 260 square feet, for a total of 8,153 square feet. The base rent, including the amendment, is $19,000 per month with a $1 per square foot annual increase on each anniversary date.

In November 2015, we entered into a facility license agreement with NantWorks LLC, or NantWorks, a related party (Note 9), for approximately 9,500 square feet of office space in Culver City, California, which has been converted to a research and development laboratory and a cGMP manufacturing facility. The license was effective in May 2015 and extends through December 2020. We have 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.

In June 2015, we entered into a lease agreement for an approximately 44,700 square foot facility in San Diego, California, for a research and development laboratory, related office and other related uses. The term of the lease extends for seven years commencing on August 1, 2016. The base rent is $0.2 million per month with 3% annual increases on each anniversary date. We are currently subleasing approximately 2,000 square feet of the premises to a related party (Note 9).

We leased a total of approximately 2,550 square feet of office space in Cardiff-by-the-Sea, California, for general office use, pursuant to an operating lease. The lease term was extended through August 31, 2018. Our total monthly lease payment was $13,200 per month. In August 2017, we subleased these premises for the remainder of the lease term for the same payment. The lease expired on August 31, 2018 and we vacated the premises.

We recognized rent expense under operating leases on a straight-line basis. Rent expense under ASC 840 for the three months ended March 31, 2018, was $0.7 million.

Commitments

We did not enter into any significant contracts during the three months ended March 31, 2019.

Related Party Agreements

3 Months Ended

Mar. 31, 2019

Related Party Agreements

9. Related Party Agreements

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

NantHealth Labs, Inc.

In March 2018, we entered into an agreement with NantHealth Labs, Inc., or NantHealth Labs, to obtain blood-based tumor profiling services. NantHealth Labs is a related party, as it is a wholly owned subsidiary of NantHealth, Inc., a majority owned subsidiary of NantWorks. We are obligated to pay NantHealth Labs fixed, per-patient fees. The agreement has an initial term of five years and renews automatically for successive one-year periods, unless terminated earlier. During the three months ended March 31, 2019 and 2018, $10,000 and $37,000, respectively, has been recognized in research and development expense on the condensed consolidated statements of operations. As of March 31, 2019 and December 31, 2018, we owed NantHealth Labs $59,000 and $49,300, respectively, which is included in due to related parties on the condensed consolidated balance sheets.

John Lee, M.D. and Leonard Sender, M.D., Inc., a professional medical corporation, dba Chan Soon-Shiong Institutes for Medicine

In 2017 and 2018, we entered into multiple agreements with John Lee, M.D. and Leonard Sender, M.D., Inc., a professional medical corporation, dba Chan Soon-Shiong Institutes for Medicine, or CSSIM, in El Segundo, California, to conduct various clinical trials. CSSIM is a related party as it is owned by two officers of NantKwest and NantWorks provides administrative services to CSSIM. One of these officers is an investigator for the trials on behalf of CSSIM. During the three months ended March 31, 2019 and 2018, $0.4 million and $0.7 million, respectively, has been recognized in research and development expense on the condensed consolidated statements of operations. As of March 31, 2019 and December 31, 2018, we owed CSSIM $0.6 million and $0.6 million, respectively, which is included in due to related parties on the condensed consolidated balance sheets.

Tensorcom, LLC

In April 2017, we entered into a sublease agreement with Tensorcom, LLC, or Tensorcom, for a portion of our San Diego, California, research and development laboratory and office space. The lease ran from May 1, 2017 through April 30, 2018. Tensorcom is a related party, as it is an affiliate of NantWorks. The sublease included a portion of the premises consisting of approximately 6,557 rentable square feet of space. The monthly base rent was $25,000 per month. For the three months ended March 31, 2018, we recognized $0.1 million in other income on the condensed consolidated statements of operations under the sublease agreement.

VivaBioCell S.p.A.

In February 2017, we entered into a research grant agreement with VivaBioCell S.p.A., or VBC, a subsidiary of NantCell. NantCell is an affiliate of NantWorks. VBC conducted research and development activities related to our NK cell lines using VBC’s proprietary technology. We recognized research and development expense of $0.1 million on the condensed consolidated statements of operations for the three months ended March 31, 2018. No expense was incurred for the three months ended March 31, 2019.

605 Doug St. LLC

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

Altor

In August 2016, we entered into an exclusive Co-Development Agreement with Altor as described in Note 7. Altor is a related party, as it is a wholly owned subsidiary of NantCell. NantCell is an affiliate of NantWorks. No charges for supplies by Altor have been incurred in association with the trials during the three months ended March 31, 2019 and 2018.

NantBio

In January 2018, we entered into a laboratory services agreement with NantBio. NantBio is a related-party as it is an affiliate of NantWorks. The agreement, effective December 2017, includes a sublease of approximately 1,965 square feet of laboratory and office space at our San Diego, California, research facility. The term of the sublease is 24 months, but can be terminated by either party with 30 days prior written notice. The sublease agreement converts to a month-to-month lease after the initial term, not to exceed the expiration of the lease agreement between us and the landlord. The monthly sublease and service fee of $10,000 is subject to an annual 3% increase on the agreement anniversary date. Rent income from this sublease is recorded in other income on the condensed consolidated statements of operations and was $32,000 and $31,000 for the three months ended March 31, 2019 and 2018, respectively. At March 31, 2019 and December 31, 2018, NantBio owed us $18,000 and $49,000, respectively, which is included in due from related parties on the condensed consolidated balance sheets.

In March 2016, NantBio and the National Cancer Institute entered into a cooperative research and development agreement. The initial five year agreement covers NantBio and its affiliates, including us. Under the agreement, the parties are collaborating on the preclinical and clinical development of proprietary recombinant NK cells and monoclonal antibodies in monotherapy and in combination immunotherapies. We benefited from the preclinical and clinical research conducted during the first three years under this agreement and provided the first, second, and third year of funding under the agreement. In each of April 2016, April 2017, and August 2018, we paid $0.6 million to the National Cancer Institute as a prepayment for services under the agreement. We recognized research and development expense relating to this agreement ratably over a 12 month period for each funding year and recorded $0.1 million and $0.1 million of expense for the three months ended March 31, 2019 and 2018, respectively. At March 31, 2019, we have accrued $25,000 in anticipation of funding in 2019. As of December 31, 2018, we had a balance of $0.1 million included in prepaid expenses and other current assets related to this agreement, on the condensed consolidated balance sheets.

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. We are 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, 2019 and 2018, we recorded selling, general and administrative expense of $0.6 million and $0.8 million, respectively. For the three months ended March 31, 2019 and 2018, we recorded research and development expense of $0.3 million and $0.9 million, respectively. These amounts exclude certain general and administrative expenses provided by third party vendors directly for our benefit, which have been reimbursed to NantWorks based on those vendors’ invoiced amounts without markup by NantWorks. In June 2016, we amended the existing shared services agreement with NantWorks whereby we can provide such support services to NantWorks and/or any of its affiliates. For the three months ended March 31, 2019 and 2018, we recorded selling, general and administrative expense reimbursements of $0.2 million and $0.1 million, respectively. For the three months ended March 31, 2019 and 2018, we recorded research and development expense reimbursements of $0.5 million and $0.6 million, respectively. We owed NantWorks a net amount of $0.8 million and $1.1 million for all agreements between the two affiliates at March 31, 2019 and December 31, 2018, respectively, which is included in due to related parties on the condensed consolidated balance sheets.

In November 2015, we entered into a facility license agreement with NantWorks, which became effective May 2015, for approximately 9,500 square feet in Culver City, California, which has been converted to a research and development laboratory and a cGMP manufacturing facility. Lease expense for this facility is recorded in research and development expense on the condensed consolidated statements of operations and was $0.1 million and $47,000 for the three months ended March 31, 2019 and 2018, respectively.

NantOmics, LLC

In June 2015, we entered into an agreement, as amended in May 2018, with NantOmics, LLC, or NantOmics, an affiliate of NantWorks, to obtain genomic sequencing and proteomic analysis services, as well as related data management and bioinformatics services, exclusively from NantOmics. We have rights to use the data and results generated from NantOmics’ services in connection with the performance of the particular oncology trial with respect to which the services were performed, but NantOmics owns the data and results, as well as any other intellectual property it creates in performing these services on our behalf. We are obligated to pay NantOmics a fixed, per sample fee, determined based on the type of services being provided. The agreement has an initial term of five years and renews automatically for successive one-year periods, unless terminated earlier. For the three months ended March 31, 2019 and 2018, we recorded operating expense of $30,000 and $42,000, respectively, to research and development under this arrangement on the condensed consolidated statements of operations. We owed NantOmics $29,000 and $24,000, respectively, at March 31, 2019 and December 31, 2018, which is included in due to related parties on the condensed consolidated balance sheets.

NantCell

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

As of March 31, 2019 and December 31, 2018, we had $1.2 million and $1.1 million in capitalized equipment, respectively, on the condensed consolidated balance sheets. During the three months ended March 31, 2019 and 2018, no expense was recorded in research and development expense on the condensed consolidated statement of operations. At March 31, 2019 and December 31, 2018 we had $0.4 million and $0.5 million, respectively, included in prepaid expenses and other current assets on the condensed consolidated balance sheets. As of March 31, 2019, NantCell owed us $33,000, which is included in due from related parties on the condensed consolidated balance sheets. As of December 31, 2018, there were no balances due between the parties.

Stock-Based Compensation

3 Months Ended

Mar. 31, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation

11. Stock-Based Compensation

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

	Three Months Ended March 31,
	2019		2018
	(Unaudited)
Stock-based compensation expense:
Warrants for common stock to an officer	$	—	$	7,636
Employee stock options		997		978
Employee RSUs		250		392
Non-employee RSUs		104		67
	$	1,351	$	9,073
Stock-based compensation expense in operating expenses:
Research and development	$	111	$	139
Selling, general and administrative		1,240		8,934
	$	1,351	$	9,073

Stock Options

The following table summarizes stock option activity for all equity incentive plans for the three months ended March 31, 2019:

	Number of Shares			Weighted- Average Exercise Price		Aggregate Intrinsic Value (in thousands)		Weighted- Average Remaining Contractual Life (in years)
Outstanding at December 31, 2018		6,493,250		$	7.14	$	563		4.8
Options exercised		(1,986,300	)	$	2.06
Outstanding at March 31, 2019		4,506,950		$	9.37	$	683		6.6
Vested and Exercisable at March 31, 2019		3,706,950		$	10.73	$	683		6.0

The total unrecognized compensation cost related to non-vested stock options as of March 31, 2019 is $1.4 million, which is expected to be recognized over a weighted-average period of 3.4 years.

During the three months ended March 31, 2019, we recognized proceeds of $4.1 million from exercises of stock options. The aggregate intrinsic value of stock options exercised during the three months ended March 31, 2019, was $0.2 million. There were no option exercises during the three months ended March 31, 2018.

Restricted Stock Units

The following table summarizes the RSUs activity under the 2015 Plan for the three months ended March 31, 2019:

	Number of Shares			Weighted- Average Grant Date Fair Value
Unvested at December 31, 2018		867,911		$	6.69
Granted		45,000		$	1.64
Vested		(49,775	)	$	3.92
Forfeited		(41,200	)	$	4.79
Unvested at March 31, 2019		821,936		$	6.67

During the three months ended March 31, 2019, we granted 45,000 RSUs to employees. As of March 31, 2019, there was $2.0 million of unrecognized stock-based compensation expense related to RSUs that is expected to be recognized over a weighted-average remaining amortization period of 2.0 years. Of that amount, $1.6 million of unrecognized expense is related to employee grants with a remaining weighted-average amortization period of 2.2 years and $0.4 million of unrecognized expense is related to non-employee grants with a remaining weighted-average amortization period of 1.2 years.

Warrants

The following table summarizes the warrant activity for the three months ended March 31, 2019:

	Number of Shares
Outstanding at December 31, 2018		17,589,250
Warrants exercised		(17,589,250	)
Outstanding at March 31, 2019		—

During the three months ended March 31, 2019 and 2018, we recognized proceeds of $35.2 million and $23,100, respectively, from exercises of warrants.

Summary of Significant Accounting Policies (Policies)

3 Months Ended

Mar. 31, 2019

Accounting Policies [Abstract]

Liquidity

As of March 31, 2019, the company had an accumulated deficit of approximately $613.8 million. We also had negative cash flow from operations of approximately $13.1 million during the three months ended March 31, 2019. The company expects that it will likely need additional capital to further fund development of, and seek regulatory approvals for, our product candidates, and to begin to commercialize any approved products.

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

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

Basis of Presentation

Principles of Consolidation and Equity Investments

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

Use of Estimates

Risks and Uncertainties

Contingencies

Concentration of Credit Risk and Other Risks and Uncertainties

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

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

Lease Obligations

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

Basic and Diluted Net Loss Per Share of Common Stock

Basic and Diluted Net Loss per Share of Common Stock

	As of March 31,
	2019		2018
Outstanding options		4,506,950		5,693,250
Outstanding RSUs		821,936		874,164
Outstanding warrants		—		17,706,818
Total		5,328,886		24,274,232

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

Recent Accounting Pronouncements

Application of New or Revised Accounting Standards – Adopted

Application of New or Revised Accounting Standards – Not Yet Adopted

Investment in Viracta Preferred Stock

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

Fair Value Measurements

The three tiers are defined as follows:

•

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

During the periods presented, no transfers were made into or out of the Level 1, 2 or 3 categories. We will continue to review the fair value inputs on quarterly basis.

Financial Statement Details (Tables)

3 Months Ended

Mar. 31, 2019

Financial Statement Details [Abstract]

Prepaid Expenses and Other Current Assets

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

	March 31, 2019		December 31, 2018
	(Unaudited)
Insurance claim receivables	$	11,144	$	10,882
Interest receivable - marketable debt securities		563		473
Prepaid supplies		431		532
Prepaid rent		368		536
Prepaid insurance		344		343
Prepaid services		341		230
Prepaid equipment maintenance		188		329
Insurance premium financing asset		85		339
Prepaid license fees		51		104
Other		80		42
	$	13,595	$	13,810

Property, Plant and Equipment, Net

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

	March 31, 2019			December 31, 2018
	(Unaudited)
Construction in progress	$	—		$	2,480
Leasehold improvements		33,540			4,087
Buildings		23,463			59,356
Equipment		21,222			20,878
Software		1,264			1,264
Furniture & fixtures		369			381
		79,858			88,446
Accumulated depreciation		(11,937	)		(11,561	)
	$	67,921		$	76,885

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

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

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

Intangible Assets, Net

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

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

Other Assets

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

	March 31, 2019		December 31, 2018
	(Unaudited)
Prepaid rent	$	—	$	1,205
Restricted cash		179		179
Security deposit		113		113
Other		22		30
	$	314	$	1,527

Accrued Expenses

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

	March 31, 2019		December 31, 2018
	(Unaudited)
Litigation settlement accruals	$	12,500	$	12,000
Accrued bonus		2,654		2,079
Accrued construction costs		1,379		3,341
Accrued compensation		1,272		943
Accrued preclinical and clinical trial costs		1,082		704
Accrued professional and service fees		806		912
Accrued laboratory equipment and supplies		277		678
Accrued franchise, sales/use and property taxes		173		250
Other		99		197
	$	20,242	$	21,104

Other Current Liabilities

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

	March 31, 2019		December 31, 2018
	(Unaudited)
Operating lease liability - current portion	$	2,938	$	—
Financing obligation - current portion		85		965
Deferred rent - current portion		—		598
Other		101		104
	$	3,124	$	1,667

Investment Income, Net

Net investment income is as follows for the three months ended March 31, 2019 and 2018 (in thousands):

	Three Months Ended March 31,
	2019			2018
	(Unaudited)
Interest income	$	410		$	704
Investment amortization accretion expense, net		(40	)		(201	)
Net realized gains on investments		—			2
	$	370		$	505

Financial Instruments Investments in Debt Securities (Tables)

3 Months Ended

Mar. 31, 2019

Cash Equivalents And Marketable Securities [Abstract]

Schedule of Investments in Debt Securities

At March 31, 2019, our investments in debt securities, excluding $1.2 million of corporate debt securities included in cash and cash equivalents, are detailed below (in thousands):

	March 31, 2019
	(Unaudited)
	Weighted- Average Remaining Contractual Life (in years)		Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Current:
Available-for-sale
Corporate debt securities		0.4	$	69,330	$	4	$	(76	)	$	69,258
Commercial paper		0.2		3,489		1		—			3,490
Foreign government bonds		0.6		3,248		—		(2	)		3,246
Government sponsored securities		0.3		277		—		(1	)		276
Current portion		0.4		76,344		5		(79	)		76,270
Noncurrent:
Available-for-sale
Corporate debt securities		2.5		1,501		—		(31	)		1,470
Government sponsored securities		1.2		2,755		—		(35	)		2,720
Noncurrent portion		1.7		4,256		—		(66	)		4,190
Total		0.4	$	80,600	$	5	$	(145	)	$	80,460

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

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

Available-for-Sale Investments in Unrealized Loss Position

Available-for-sale investments that had been in an unrealized loss position for less than 12 months and for more than 12 months at March 31, 2019 and December 31, 2018 were as follows (in thousands):

	March 31, 2019
	(Unaudited)
	Less than 12 months					More than 12 months
	Estimated Fair Value		Gross Unrealized Losses			Estimated Fair Value		Gross Unrealized Losses
Corporate debt securities	$	34,111	$	(9	)	$	12,465	$	(99	)
Government sponsored securities		—		—			2,720		(35	)
Foreign government bonds		3,246		(2	)		—		—
Total	$	37,357	$	(11	)	$	15,185	$	(134	)

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

Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2019

Fair Value Disclosures [Abstract]

Summary of Financial Assets Measured at Fair Value on Recurring Basis

The following tables present our assets that are measured at fair value on a recurring basis as of March 31, 2019 and December 31, 2018 (in thousands):

	Fair Value Measurements at March 31, 2019
	(Unaudited)
	Total		Level 1		Level 2		Level 3
Assets:
Current:
Cash and cash equivalents	$	22,279	$	21,031	$	1,248	$	—
Corporate debt securities		69,258		—		69,258		—
Commercial paper		3,490		—		3,490		—
Foreign government bonds		3,246		—		3,246		—
Government sponsored securities		276		—		276		—
Noncurrent:
Government sponsored securities		2,720		—		2,720		—
Corporate debt securities		1,470		—		1,470		—
Total assets measured at fair value	$	102,739	$	21,031	$	81,708	$	—

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

Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock Based Compensation Expenses Included on Operations Statement

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

	Three Months Ended March 31,
	2019		2018
	(Unaudited)
Stock-based compensation expense:
Warrants for common stock to an officer	$	—	$	7,636
Employee stock options		997		978
Employee RSUs		250		392
Non-employee RSUs		104		67
	$	1,351	$	9,073
Stock-based compensation expense in operating expenses:
Research and development	$	111	$	139
Selling, general and administrative		1,240		8,934
	$	1,351	$	9,073

Summarizes Stock Option Activity Under Equity Intensive Plan

The following table summarizes stock option activity for all equity incentive plans for the three months ended March 31, 2019:

	Number of Shares			Weighted- Average Exercise Price		Aggregate Intrinsic Value (in thousands)		Weighted- Average Remaining Contractual Life (in years)
Outstanding at December 31, 2018		6,493,250		$	7.14	$	563		4.8
Options exercised		(1,986,300	)	$	2.06
Outstanding at March 31, 2019		4,506,950		$	9.37	$	683		6.6
Vested and Exercisable at March 31, 2019		3,706,950		$	10.73	$	683		6.0

Summary of (RSUs) Activity

The following table summarizes the RSUs activity under the 2015 Plan for the three months ended March 31, 2019:

	Number of Shares			Weighted- Average Grant Date Fair Value
Unvested at December 31, 2018		867,911		$	6.69
Granted		45,000		$	1.64
Vested		(49,775	)	$	3.92
Forfeited		(41,200	)	$	4.79
Unvested at March 31, 2019		821,936		$	6.67

Summary of Warrant Activity

The following table summarizes the warrant activity for the three months ended March 31, 2019:

	Number of Shares
Outstanding at December 31, 2018		17,589,250
Warrants exercised		(17,589,250	)
Outstanding at March 31, 2019		—

- Definition

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

+ References + Details

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Accounting Policies [Line Items]
Lease practical expedients package	true
Operating lease, description	elected not to recognize right-of-use assets and lease liabilities for qualifying short-term leases with an initial lease term of 12 months or less at lease inception
Operating lease right-of-use assets, net	$ 13,155	$ 13,532	$ 0
Operating lease liabilities	15,690
Property, plant and equipment, net	67,921		76,885
Liabilities	$ 40,453		$ 35,944
Accounting Standards Update 2016-02
Accounting Policies [Line Items]
Operating lease right-of-use assets, net		13,500
Operating lease liabilities		16,400
Property, plant and equipment, net		70,299
Accounting Standards Update 2016-02 \| Accumulated Deficit
Accounting Policies [Line Items]
Build-to-suit related liabilities and assets adjust as accumulated deficit		(900)
Accounting Standards Update 2016-02 \| Difference between Lease Guidance in Effect before and after Topic 842
Accounting Policies [Line Items]
Property, plant and equipment, net		(6,600)
Liabilities		$ (5,700)
VIE \| Minimum
Accounting Policies [Line Items]
Percentage of ownership interest	20.00%
VIE \| Maximum
Accounting Policies [Line Items]
Percentage of ownership interest	50.00%

Financial Statement Details - Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Financial Statement Details [Abstract]
Insurance claim receivables	$ 11,144	$ 10,882
Interest receivable - marketable debt securities	563	473
Prepaid supplies	431	532
Prepaid rent	368	536
Prepaid insurance	344	343
Prepaid services	341	230
Prepaid equipment maintenance	188	329
Insurance premium financing asset	85	339
Prepaid license fees	51	104
Other	80	42
Total prepaid expenses and other current assets	$ 13,595	$ 13,810

Financial Statement Details - Accrued Expenses (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Financial Statement Details [Abstract]
Litigation settlement accruals	$ 12,500	$ 12,000
Accrued bonus	2,654	2,079
Accrued construction costs	1,379	3,341
Accrued compensation	1,272	943
Accrued preclinical and clinical trial costs	1,082	704
Accrued professional and service fees	806	912
Accrued laboratory equipment and supplies	277	678
Accrued franchise, sales/use and property taxes	173	250
Other	99	197
Accrued Liabilities Current	$ 20,242	$ 21,104

Financial Instruments Investments in Debt Securities - Schedule of Investments in Debt Securities (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale, Amortized Cost	$ 0	$ 0
Available-for-sale, Unrealized Gains	0	0
Available-for-sale, Unrealized Losses	0	0
Available-for-sale, Fair Value	$ 0	0
Available-for-sale, Weighted- Average Remaining Contractual Life	4 months 24 days
Available-for-sale and held-to-maturity, Amortized Cost	$ 80,600	64,009
Available-for-sale and held-to-maturity, Unrealized Gains	5	1
Available-for-sale and held-to-maturity, Unrealized Losses	(145)	(258)
Available-for-sale and held-to-maturity, Fair Value	80,460	63,752
Notes Receivable
Schedule Of Available For Sale Securities [Line Items]
Held-to-maturity, Amortized Cost		723
Held-to-maturity, Unrealized Gains		0
Held-to-maturity, Unrealized Losses		0
Held-to-maturity, Fair Value		723
Current Assets
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale, Amortized Cost		57,463
Available-for-sale, Unrealized Gains		1
Available-for-sale, Unrealized Losses		(136)
Available-for-sale, Fair Value		57,328
Available-for-sale and held-to-maturity, Amortized Cost	76,344	58,186
Available-for-sale and held-to-maturity, Unrealized Gains	5	1
Available-for-sale and held-to-maturity, Unrealized Losses	(79)	(136)
Available-for-sale and held-to-maturity, Fair Value	76,270	58,051
Current Assets \| Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale, Amortized Cost	69,330	57,463
Available-for-sale, Unrealized Gains	4	1
Available-for-sale, Unrealized Losses	(76)	(136)
Available-for-sale, Fair Value	$ 69,258	57,328
Available-for-sale, Weighted- Average Remaining Contractual Life	4 months 24 days
Current Assets \| Commercial Paper
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale, Amortized Cost	$ 3,489
Available-for-sale, Unrealized Gains	1
Available-for-sale, Unrealized Losses	0
Available-for-sale, Fair Value	$ 3,490
Available-for-sale, Weighted- Average Remaining Contractual Life	2 months 12 days
Current Assets \| Foreign Government Bonds
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale, Amortized Cost	$ 3,248
Available-for-sale, Unrealized Gains	0
Available-for-sale, Unrealized Losses	(2)
Available-for-sale, Fair Value	$ 3,246
Available-for-sale, Weighted- Average Remaining Contractual Life	7 months 6 days
Current Assets \| Government Sponsored Securities
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale, Amortized Cost	$ 277
Available-for-sale, Unrealized Gains	0
Available-for-sale, Unrealized Losses	(1)
Available-for-sale, Fair Value	$ 276
Available-for-sale, Weighted- Average Remaining Contractual Life	3 months 18 days
Noncurrent Assets
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale, Amortized Cost	$ 4,256	5,823
Available-for-sale, Unrealized Gains	0	0
Available-for-sale, Unrealized Losses	(66)	(122)
Available-for-sale, Fair Value	$ 4,190	5,701
Available-for-sale, Weighted- Average Remaining Contractual Life	1 year 8 months 12 days
Noncurrent Assets \| Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale, Amortized Cost	$ 1,501	3,067
Available-for-sale, Unrealized Gains	0	0
Available-for-sale, Unrealized Losses	(31)	(76)
Available-for-sale, Fair Value	$ 1,470	2,991
Available-for-sale, Weighted- Average Remaining Contractual Life	2 years 6 months
Noncurrent Assets \| Government Sponsored Securities
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale, Amortized Cost	$ 2,755	2,756
Available-for-sale, Unrealized Gains	0	0
Available-for-sale, Unrealized Losses	(35)	(46)
Available-for-sale, Fair Value	$ 2,720	$ 2,710
Available-for-sale, Weighted- Average Remaining Contractual Life	1 year 2 months 12 days

Commitment and Contingencies - Additional Information (Detail)	1 Months Ended								3 Months Ended			12 Months Ended
	Apr. 30, 2019 USD ($)	Aug. 31, 2018 USD ($)	Dec. 31, 2017 USD ($) ft²	Sep. 30, 2016 USD ($) ft²	Jun. 30, 2016 USD ($) ft² $ / ft²	Mar. 31, 2016	Nov. 30, 2015 USD ($) ft²	Jun. 30, 2015 USD ($) ft²	Mar. 31, 2019 USD ($) ft²	Sep. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($) ft²	Jan. 01, 2019
Commitments And Contingencies [Line Items]
Litigation settlement amount									$ 12,000,000
Weighted average remaining lease term									5 years 2 months 12 days				5 years 4 months 24 days
Weighted average discount rate									9.00%				9.00%
Cash outflows from operating leases									$ 1,300,000
Rent expense											$ 700,000
Woburn, Massachusetts
Commitments And Contingencies [Line Items]
Number of square foot of facility leased \| ft²					8,153				7,893
Term of lease arrangement									48 months
Lease commencement date						Apr. 29, 2016
Addition to number of square foot of facility leased \| ft²					260
Base rent - yearly					$ 19,000
Annual increase of base rent \| $ / ft²					1
Period of agreement									In June 2016, the lease was amended to add 260 square feet, for a total of 8,153 square feet. The base rent, including the amendment, is $19,000 per month with a $1 per square foot annual increase on each anniversary date
Commitment; San Diego
Commitments And Contingencies [Line Items]
Number of square foot of facility leased \| ft²								44,700
Base rent - monthly								$ 200,000
Percentage of annual increase of base rent								3.00%
Base lease term								7 years
Sub Lease Agreements
Commitments And Contingencies [Line Items]
Number of square foot of facility leased \| ft²												2,000
Cardiff-by-the-Sea, California
Commitments And Contingencies [Line Items]
Number of square foot of facility leased \| ft²												2,550
Base rent - monthly												$ 13,200
Lease agreement extended lease period												Aug. 31, 2018
NantBioScience
Commitments And Contingencies [Line Items]
Reimbursed upfront payment to third-party		$ 900,000
Related party transaction, amount paid to third-party		500,000
Related party transaction, aggregate value		$ 1,400,000
Initial term of agreement entered into with the related party by the entity		10 years				5 years
Related party agreement expiration date		2027-06
Number of square foot of facility leased \| ft²			1,965
Base rent - monthly			$ 10,000
Percentage of annual increase of base rent			3.00%
Doug St, LLC
Commitments And Contingencies [Line Items]
Period of agreement									The lease runs from July 2016 through July 2023. We have the option to extend the lease for an additional three year term through July 2026. The monthly rent is $0.1 million with annual increases of 3% beginning in July 2017
Optional extended lease term				3 years
Base rent - monthly				$ 100,000
Percentage of annual increase of base rent				3.00%
Annual percentage increases to base rent commencement date				Jul. 31, 2017
Doug St, LLC \| El Segundo California
Commitments And Contingencies [Line Items]
Number of square foot of facility leased \| ft²				24,250
NantWorks
Commitments And Contingencies [Line Items]
Number of square foot of facility leased \| ft²							9,500
Period of agreement									The license was effective in May 2015 and extends through December 2020. We have 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
Prepaid Expenses and Current Assets
Commitments And Contingencies [Line Items]
Insurance claim receivable									$ 11,100,000			$ 10,900,000
Subsequent Event
Commitments And Contingencies [Line Items]
Attorney's fee to plaintiffs	$ 500,000
Directors and Officers Insurance Policy
Commitments And Contingencies [Line Items]
Litigation settlement amount									10,800,000
Selling, General and Administrative
Commitments And Contingencies [Line Items]
Litigation settlement amount										$ 1,200,000
Research and Development Expense and Selling, General and Administrative Expense
Commitments And Contingencies [Line Items]
Operating lease expense									1,200,000
Variable lease costs									$ 200,000

Commitment and Contingencies - Summary of Future Minimum Lease Payments (Detail) $ in Thousands	Mar. 31, 2019 USD ($)
Commitments And Contingencies Disclosure [Abstract]
2019 (excluding the three months ended March 31, 2019)	$ 3,102
2020	4,080
2021	3,438
2022	3,538
2023	2,545
Thereafter	2,813
Total future minimum lease payments	19,516
Less: Interest	3,826
Present value of operating lease liabilities	$ 15,690

Related Party Agreements - Additional Information (Detail)	1 Months Ended								3 Months Ended		12 Months Ended
	Aug. 31, 2018 USD ($)	Dec. 31, 2017 USD ($) ft²	Apr. 30, 2017 USD ($) ft²	Sep. 30, 2016 USD ($) ft²	Apr. 30, 2016 USD ($)	Mar. 31, 2016	Nov. 30, 2015 USD ($) ft²	Jun. 30, 2015	Mar. 31, 2019 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)
Related Party Transaction [Line Items]
Research and development									$ 12,598,000	$ 13,991,000
Due to related parties									1,531,000		$ 1,696,000
Selling, general and administrative expense									5,742,000	14,298,000
Prepaid expenses and other current assets									$ 13,595,000		13,810,000
NantHealth Labs, Inc.
Related Party Transaction [Line Items]
Initial term of agreement entered into with the related party by the entity									5 years
Related party, agreement renewal term									1 year
Research and development									$ 10,000	37,000
Due to related parties									59,000		49,300
Chan Soon-Shiong Institutes for Medicine (CSSIM) \| California
Related Party Transaction [Line Items]
Research and development									400,000	700,000
Due to related parties									$ 600,000		600,000
Tensorcom, Inc \| San Diego California
Related Party Transaction [Line Items]
Period of agreement									lease ran from May 1, 2017 through April 30, 2018
Number of square foot of facility leased \| ft²			6,557
Base rent - monthly			$ 25,000
Tensorcom, Inc \| San Diego California \| Other Income
Related Party Transaction [Line Items]
Sublease revenue recognized										100,000
VivaBioCell S.p.A.
Related Party Transaction [Line Items]
Research and development									$ 0	100,000
Doug St, LLC
Related Party Transaction [Line Items]
Period of agreement									The lease runs from July 2016 through July 2023. We have the option to extend the lease for an additional three-year term through July 2026.
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 between parties									$ 0		0
Doug St, LLC \| Research and Development
Related Party Transaction [Line Items]
Lease expense									200,000	100,000
Doug St, LLC \| El Segundo California
Related Party Transaction [Line Items]
Number of square foot of facility leased \| ft²				24,250
Altor
Related Party Transaction [Line Items]
Supplies and milestone charges for conducting clinical trials									0	0
NantBioScience
Related Party Transaction [Line Items]
Initial term of agreement entered into with the related party by the entity	10 years					5 years
Research and development									100,000	100,000
Due to related parties									$ 25,000
Number of square foot of facility leased \| ft²		1,965
Base rent - monthly		$ 10,000
Percentage of annual increase of base rent		3.00%
Sublease term		24 months
Sublease termination notice period		30 days
Research and development expense, ratable payment period									12 months
Prepayment for services amount	$ 600,000		$ 600,000		$ 600,000
NantBioScience \| Prepaid Expenses and Current Assets
Related Party Transaction [Line Items]
Research and development											100,000
Due between parties									$ 18,000		49,000
NantBioScience \| Other Income
Related Party Transaction [Line Items]
Sublease revenue recognized									32,000	31,000
NantWorks
Related Party Transaction [Line Items]
Number of square foot of facility leased \| ft²							9,500
Base rent - monthly							$ 47,000
Percentage of annual increase of base rent							3.00%
Annual percentage increases to base rent commencement date							Jan. 31, 2017
NantWorks \| Shared Services Agreement
Related Party Transaction [Line Items]
Research and development									300,000	900,000
Selling, general and administrative expense									600,000	800,000
NantWorks \| Reimbursements \| Shared Services Agreement
Related Party Transaction [Line Items]
Research and development									500,000	600,000
Due to related parties									800,000		1,100,000
Selling, general and administrative expense									200,000	100,000
NantWorks \| Research and Development
Related Party Transaction [Line Items]
Lease expense									100,000	47,000
NantOmics
Related Party Transaction [Line Items]
Initial term of agreement entered into with the related party by the entity								5 years
Related party, agreement renewal term								1 year
Research and development									30,000	42,000
Due to related parties									29,000		24,000
NantCell Inc
Related Party Transaction [Line Items]
Initial term of agreement entered into with the related party by the entity								5 years
Related party, agreement renewal term								1 year
Research and development									0	$ 0
Due between parties									33,000		0
Related parties, capitalized equipment amount									1,200,000		1,100,000
Prepaid expenses and other current assets									$ 400,000		$ 500,000

Stock-Based Compensation - Stock Option Activity (Detail) - Employee Stock Option - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Number of Shares
Stock Options, Beginning Balance	6,493,250
Stock Options, Options exercised	(1,986,300)
Stock Options, Ending Balance	4,506,950	6,493,250
Stock Options, Vested and Exercisable	3,706,950
Weighted Average Exercise Price
Weighted Average Exercise Price, Outstanding Beginning balance	$ 7.14
Weighted Average Exercise Price, Options exercised	2.06
Weighted Average Exercise Price, Outstanding Ending balance	9.37	$ 7.14
Weighted Average Exercise Price, Vested and Exercisable	$ 10.73
Aggregate Intrinsic Value
Aggregate Intrinsic Value, Outstanding, Beginning balance	$ 563
Aggregate Intrinsic Value, Outstanding, Ending balance	683	$ 563
Aggregate Intrinsic Value, Vested and Exercisable	$ 683
Weighted Average Remaining Contractual Life
Weighted Average Remaining Contractual Life, Outstanding	6 years 7 months 6 days	4 years 9 months 18 days
Weighted Average Remaining Contractual Life, Vested and Exercisable	6 years

Stock-Based Compensation - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Exercise of stock options	$ 4,070,000
Proceeds from exercises of warrants	35,200,000	$ 23,100
Chief Executive Officer
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Proceeds from stock options exercised	4,100,000
Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation cost related to non-vested stock options	$ 1,400,000
Weighted-average period for recognition	3 years 4 months 24 days
Exercise of stock options, Shares	1,986,300
Exercise of stock options		$ 0
Intrinsic value of stock options exercised	$ 200,000
Outstanding RSUs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average period for recognition	2 years
Grants of restricted stock	45,000
Unrecognized compensation cost related to non-vested stock options	$ 2,000,000
Employee RSUs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average period for recognition	2 years 2 months 12 days
Grants of restricted stock	45,000
Unrecognized compensation cost related to non-vested stock options	$ 1,600,000
Non Employee Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average period for recognition	1 year 2 months 12 days
Unrecognized compensation cost related to non-vested stock options	$ 400,000

Stock-Based Compensation - Summary of (RSUs) Activity (Detail) - Outstanding RSUs	3 Months Ended
	Mar. 31, 2019 $ / shares shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Shares, Unvested, Beginning balance \| shares	867,911
Number of Shares, Granted \| shares	45,000
Number of Shares, Vested \| shares	(49,775)
Number of Shares, Forfeited \| shares	(41,200)
Number of Shares, Unvested, Ending balance \| shares	821,936
Weighted-Average Grant Date Fair Value, Unvested, beginning balance \| $ / shares	$ 6.69
Weighted-Average Grant Date Fair Value, Granted \| $ / shares	1.64
Weighted-Average Grant Date Fair Value, Vested \| $ / shares	3.92
Weighted-Average Grant Date Fair Value, Forfeited \| $ / shares	4.79
Weighted-Average Grant Date Fair Value, Unvested, ending balance \| $ / shares	$ 6.67

Financial Statement Details - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Financial Statement Details [Line Items]
Depreciation expense related to property, plant and equipment	$ 1,800,000	$ 1,100,000
Amortization expense	600,000	600,000
Impairment loss on recognized investments	0	$ 0
Accounting Standards Update 2016-02
Financial Statement Details [Line Items]
Reclassification of assets from buildings to leasehold improvements	32,000,000
Derecognized build-to-suit lease assets	$ 6,600,000

Viracta Investment and Convertible Notes - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended		3 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2019	Jan. 31, 2019	Dec. 31, 2018	Mar. 31, 2017
Schedule Of Investments [Line Items]
Equity securities			$ 9,251		$ 8,500	$ 8,500
2018 Note and Warrant Purchase Agreement
Schedule Of Investments [Line Items]
Purchase of convertible note	$ 400	$ 400
Convertible note accrued interest rate			8.00%
Debt instrument maturity date			1 year
2018 Note and Warrant Purchase Agreement \| Series B Preferred Stock
Schedule Of Investments [Line Items]
Preferred stock value			$ 9,300	$ 800

Fair Value Measurements - Summary of Financial Assets Measured at Fair Value on Recurring Basis (Detail) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	$ 102,739	$ 79,850
Current Assets \| Cash and cash equivalents
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	22,279	16,821
Current Assets \| Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	69,258	57,328
Current Assets \| Government Sponsored Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	276
Current Assets \| Foreign Government Bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	3,246
Current Assets \| Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	3,490
Noncurrent Assets \| Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	1,470	2,991
Noncurrent Assets \| Government Sponsored Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	2,720	2,710
Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	21,031	16,821
Level 1 \| Current Assets \| Cash and cash equivalents
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	21,031	16,821
Level 1 \| Current Assets \| Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	0	0
Level 1 \| Current Assets \| Government Sponsored Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	0
Level 1 \| Current Assets \| Foreign Government Bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	0
Level 1 \| Current Assets \| Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	0
Level 1 \| Noncurrent Assets \| Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	0	0
Level 1 \| Noncurrent Assets \| Government Sponsored Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	0	0
Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	81,708	63,029
Level 2 \| Current Assets \| Cash and cash equivalents
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	1,248	0
Level 2 \| Current Assets \| Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	69,258	57,328
Level 2 \| Current Assets \| Government Sponsored Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	276
Level 2 \| Current Assets \| Foreign Government Bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	3,246
Level 2 \| Current Assets \| Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	3,490
Level 2 \| Noncurrent Assets \| Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	1,470	2,991
Level 2 \| Noncurrent Assets \| Government Sponsored Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	2,720	2,710
Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	0	0
Level 3 \| Current Assets \| Cash and cash equivalents
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	0	0
Level 3 \| Current Assets \| Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	0	0
Level 3 \| Current Assets \| Government Sponsored Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	0
Level 3 \| Current Assets \| Foreign Government Bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	0
Level 3 \| Current Assets \| Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	0
Level 3 \| Noncurrent Assets \| Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	0	0
Level 3 \| Noncurrent Assets \| Government Sponsored Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	$ 0	$ 0

Stockholders' Equity - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2019	Nov. 30, 2015
Equity [Abstract]
Total amount authorized for repurchase		$ 50,000,000
Repurchase of common stock, shares	0
Remaining authorized repurchase amount	$ 18,800,000

Stock-Based Compensation - Summary of Warrant Activity (Detail) - Outstanding Warrants	3 Months Ended
	Mar. 31, 2019 shares
Warrant [Line Items]
Number of shares Warrants, Beginning Balance	17,589,250
Number of shares Warrants exercised	(17,589,250)
Number of shares Warrants, Ending Balance	0

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2019	Dec. 31, 2018
Statement Of Financial Position [Abstract]
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	500,000,000	500,000,000
Common stock, shares issued	98,674,153	79,087,734
Common stock, shares outstanding	98,674,153	79,087,734

Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (17,885)	$ (27,519)
Other comprehensive income (loss), net of income taxes:
Net unrealized gain (loss) on available-for-sale securities	61	(174)
Total other comprehensive income (loss)	61	(174)
Comprehensive loss	$ (17,824)	$ (27,693)

Summary of Significant Accounting Policies - Securities Excluded from the Computation of Potentially Dilutive Securities (Detail) - shares	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	5,328,886	24,274,232
Employee Stock Option
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	4,506,950	5,693,250
Outstanding RSUs
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	821,936	874,164
Outstanding Warrants
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	0	17,706,818

Financial Statement Details - Property, Plant and Equipment, Net (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	$ 79,858	$ 88,446
Accumulated depreciation	(11,937)	(11,561)
Property, plant and equipment, net	67,921	76,885
Construction in Progress
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	0	2,480
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	33,540	4,087
Buildings
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	23,463	59,356
Equipment
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	21,222	20,878
Software
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	1,264	1,264
Furniture And Fixtures
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	$ 369	$ 381

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

Financial Statement Details - Other Assets (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Financial Statement Details [Abstract]
Prepaid rent	$ 0	$ 1,205
Restricted cash	179	179
Security deposit	113	113
Other	22	30
Other Assets Noncurrent	$ 314	$ 1,527

Financial Statement Details - Other Current Liabilities (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Financial Statement Details [Abstract]
Operating lease liability - current portion	$ 2,938	$ 2,960	$ 0
Financing obligation - current portion	85		965
Deferred rent - current portion	0		598
Other	101		104
Other current liabilities	$ 3,124		$ 1,667

Financial Instruments Investments in Debt Securities - Additional Information (Detail) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019 USD ($) Security	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)
Schedule Of Available For Sale Securities [Line Items]
Cash and cash equivalents	$ 22,279	$ 16,821	$ 22,279	$ 11,196
Maximum
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale securities, period of unrealized loss positions	12 months	12 months
Minimum
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale securities, period of unrealized loss positions	12 months	12 months
Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Cash and cash equivalents	$ 1,200
Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Number of available-for-sale securities in unrealized loss positions \| Security	46

Financial Instruments Investments in Debt Securities - Available-for-Sale Investments in Unrealized Loss Position (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Schedule Of Available For Sale Securities [Line Items]
Available-for-Sale Investments, Less than 12 months, Estimated Fair Value	$ 37,357	$ 32,010
Available-for-Sale Investments, Less than 12 months, Gross Unrealized Losses	(11)	(26)
Available-for-Sale Investments, More than 12 months, Estimated Fair Value	15,185	29,373
Available-for-Sale Investments, More than 12 months, Gross Unrealized Losses	(134)	(232)
Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Available-for-Sale Investments, Less than 12 months, Estimated Fair Value	34,111	32,010
Available-for-Sale Investments, Less than 12 months, Gross Unrealized Losses	(9)	(26)
Available-for-Sale Investments, More than 12 months, Estimated Fair Value	12,465	26,663
Available-for-Sale Investments, More than 12 months, Gross Unrealized Losses	(99)	(186)
Government Sponsored Securities
Schedule Of Available For Sale Securities [Line Items]
Available-for-Sale Investments, Less than 12 months, Estimated Fair Value	0	0
Available-for-Sale Investments, Less than 12 months, Gross Unrealized Losses	0	0
Available-for-Sale Investments, More than 12 months, Estimated Fair Value	2,720	2,710
Available-for-Sale Investments, More than 12 months, Gross Unrealized Losses	(35)	$ (46)
Foreign Government Bonds
Schedule Of Available For Sale Securities [Line Items]
Available-for-Sale Investments, Less than 12 months, Estimated Fair Value	3,246
Available-for-Sale Investments, Less than 12 months, Gross Unrealized Losses	(2)
Available-for-Sale Investments, More than 12 months, Estimated Fair Value	0
Available-for-Sale Investments, More than 12 months, Gross Unrealized Losses	$ 0

Collaboration and License Agreements - Additional Information (Detail) - Altor	3 Months Ended
	Mar. 31, 2019 USD ($) Patient	Mar. 31, 2018 USD ($)
Licensing Agreement [Line Items]
Maximum number of patients in phase 1 and 2 for clinical trials \| Patient	400
Supplies and milestone charges for conducting clinical trials \| $	$ 0	$ 0

Commitment and Contingencies - Schedule of Lease Balances (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Assets And Liabilities Lessee [Abstract]
Operating lease right-of-use assets, net	$ 13,155	$ 13,532	$ 0
Operating lease liability - current portion	2,938	2,960	0
Operating lease liability, less current portion	$ 12,752	$ 13,407	$ 0

Commitment and Contingencies - Summary of Future Minimum Lease Payments (Parenthetical) (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($)
Commitments And Contingencies Disclosure [Abstract]
Operating lease payments related to options to extend lease terms	$ 3.3

Stock-Based Compensation - Stock Based Compensation Expenses Related to Statement of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 1,351	$ 9,073
Warrants For Common Stock \| Officer
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	0	7,636
Employee Stock Option
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	997	978
Employee RSUs
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	250	392
Non-employee RSUs
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	104	67
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	111	139
Selling, General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 1,240	$ 8,934

Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Tax [Line Items]
Federal statutory tax rate	21.00%
Company's effective tax rate	0.00%
Unrealized gains in other comprehensive income		$ 0
Tax benefit	$ (36,000)	0
Tax benefit in other comprehensive income	(100,000)	0
Korea
Income Tax [Line Items]
Tax benefit	$ 0	$ 100,000