Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2018	Jan. 31, 2019	Jun. 30, 2018
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY
Trading Symbol	VICL
Entity Registrant Name	VICAL INC
Entity Central Index Key	0000819050
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		21,820,195
Entity Public Float			$ 19,828,148

Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 11,870	$ 24,841
Marketable securities, available-for-sale	36,201	35,658
Restricted cash	0	192
Deferred contract costs	0	10,502
Receivables and other assets	1,128	5,124
Total current assets	49,199	76,317
Long-term investments	2,386	2,209
Property and equipment, net	100	606
Intangible assets, net	0	703
Other assets	659	659
Total assets	52,344	80,494
Current liabilities:
Accounts payable and accrued expenses	3,551	5,217
Deferred revenue	30	11,700
Total current liabilities	3,581	16,917
Long-term liabilities:
Commitments and contingencies (Notes 6 and 7)	0	0
Stockholders’ equity:
Preferred stock, $0.01 par value, 5,000 shares authorized, none issued and outstanding	0	0
Common stock, $0.01 par value, 50,000 shares authorized, 21,817 and 21,802 shares issued and outstanding at December 31, 2018 and 2017, respectively	218	218
Additional paid-in capital	490,337	489,975
Accumulated deficit	(442,064)	(426,738)
Accumulated other comprehensive income	272	122
Total stockholders’ equity	48,763	63,577
Total liabilities and stockholders’ equity	$ 52,344	$ 80,494

Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2018	Dec. 31, 2017
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	50,000,000	50,000,000
Common stock, shares issued	21,817,000	21,802,000
Common stock, shares outstanding	21,817,000	21,802,000

Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues:
Contract revenue	$ 1,582	$ 13,401	$ 12,804
License and royalty revenue	40	418	1,727
Total revenues	1,622	13,819	14,531
Operating expenses:
Research and development	12,327	14,391	10,355
Manufacturing and production	1,436	6,479	6,291
General and administrative	7,505	6,335	7,062
Total operating expenses	21,268	27,205	23,708
Loss from operations	(19,646)	(13,386)	(9,177)
Other income:
Investment and other income, net	3,392	426	204
Net loss	$ (16,254)	$ (12,960)	$ (8,973)
Basic and diluted net loss per share	$ (0.74)	$ (1.01)	$ (0.90)
Weighted average shares used in computing basic and diluted net loss per share	21,842	12,888	10,019

Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
Statements of Comprehensive Loss - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (16,254)	$ (12,960)	$ (8,973)
Unrealized gain (loss) on available-for-sale and long-term marketable securities:
Unrealized gain (loss) arising during holding period, net of tax benefit of $37, $56 and $0 for years ended December 31, 2018, 2017 and 2016, respectively	150	97	(15)
Other comprehensive gain (loss)	150	97	(15)
Total comprehensive loss	$ (16,104)	$ (12,863)	$ (8,988)

- Definition

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

+ References + Details

Statements of Comprehensive Loss (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement Of Income And Comprehensive Income [Abstract]
Unrealized gain (loss) arising during holding period, tax benefit	$ 37	$ 56	$ 0

Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income/(Loss) [Member]
Beginning Balance at Dec. 31, 2015	$ 45,393	$ 92	$ 450,166	$ (404,905)	$ 40
Beginning Balance, shares at Dec. 31, 2015		9,154
Net loss	(8,973)			(8,973)
Other comprehensive income (loss)	(15)				(15)
Issuance of common stock	7,753	$ 18	7,735
Issuance of common stock, shares		1,841
Issuance of common stock underlying restricted stock units net of shares withheld to settle withholding taxes	(9)	$ 1	(10)
Issuance of common stock underlying restricted stock units net of shares withheld to settle withholding taxes, shares		57
Non-cash compensation expense related to grant of equity based compensation	990		990
Ending Balance at Dec. 31, 2016	45,139	$ 111	458,881	(413,878)	25
Ending Balance, shares at Dec. 31, 2016		11,052
Net loss	(12,960)			(12,960)
Other comprehensive income (loss)	97		(100)	100	97
Issuance of common stock	17,956	$ 107	17,849
Issuance of common stock, shares		10,704
Issuance of pre-funded warrants	12,588		12,588
Issuance of common stock underlying restricted stock units net of shares withheld to settle withholding taxes	1		1
Issuance of common stock underlying restricted stock units net of shares withheld to settle withholding taxes, shares		46
Non-cash compensation expense related to grant of equity based compensation	756		756
Ending Balance at Dec. 31, 2017	$ 63,577	$ 218	489,975	(426,738)	122
Ending Balance, shares at Dec. 31, 2017	21,802	21,802
Net loss	$ (16,254)			(16,254)
Retained earnings adjustment upon adoption of ASU 2014-09	928			928
Other comprehensive income (loss)	150				150
Issuance of common stock underlying restricted stock units net of shares withheld to settle withholding taxes	1		1
Issuance of common stock underlying restricted stock units net of shares withheld to settle withholding taxes, shares		15
Non-cash compensation expense related to grant of equity based compensation	361		361
Ending Balance at Dec. 31, 2018	$ 48,763	$ 218	$ 490,337	$ (442,064)	$ 272
Ending Balance, shares at Dec. 31, 2018	21,817	21,817

Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
Statements of Cash Flows - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net loss	$ (16,254)	$ (12,960)	$ (8,973)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	151	793	1,117
Accretion of discount on short-term investments	(249)	0	0
Write-off of abandoned patents	673	0	374
Gain on sale of property and equipment	(2,286)	0	0
Compensation expense related to stock options and awards	361	756	990
Changes in operating assets and liabilities:
Deferred contract costs	0	(4,989)	(5,428)
Receivables and other assets	5,064	(1,973)	840
Accounts payable and accrued expenses	(1,666)	1,313	557
Deferred revenue	(239)	8,682	2,768
Deferred rent	0	(223)	(633)
Net cash used in operating activities	(14,445)	(8,601)	(8,388)
Cash flows from investing activities:
Maturities of marketable securities	44,688	31,429	30,652
Purchases of marketable securities	(45,009)	(36,640)	(38,069)
Purchases of property and equipment	(36)	(80)	(255)
Proceeds from the sale of property and equipment	1,639	0	0
Net cash provided by (used in) investing activities	1,282	(5,291)	(7,672)
Cash flows from financing activities:
Net proceeds from issuance of common stock and pre-funded warrants	1	30,549	7,758
Payment of withholding taxes for net settlement of restricted stock units	(1)	(4)	(14)
Net cash provided by financing activities	0	30,545	7,744
Net (decrease) increase in cash, cash equivalents and restricted cash	(13,163)	16,653	(8,316)
Cash, cash equivalents and restricted cash at beginning of year	25,033	8,380	16,696
Cash, cash equivalents and restricted cash at end of year	11,870	25,033	8,380
Supplemental disclosure of noncash investing and financing activities:
Gain related to deferred rent	$ 1,067	$ 0	$ 0

Organization and Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2018

Accounting Policies [Abstract]

Organization and Summary of Significant Accounting Policies

1. Organization and Summary of Significant Accounting Policies

Organization and Business Activity

Vical Incorporated, or the Company, a Delaware corporation, was incorporated in April 1987 and has devoted substantially all of its resources since that time to its research and development programs. The Company researches and develops biopharmaceutical products, including those based on its patented DNA delivery technologies for the prevention and treatment of serious or life-threatening diseases.

All of the Company’s potential products are in research and development phases. No revenues have been generated from the sale of any such products, nor are any such revenues expected for at least the next several years. The Company earns revenue from research and development agreements with pharmaceutical collaborators and from contract manufacturing agreements. Most of the Company’s product candidates will require significant additional research and development efforts, including extensive preclinical and clinical testing. All product candidates that advance to clinical testing will require regulatory approval prior to commercial use, and will require significant costs for commercialization. There can be no assurance that the Company’s research and development efforts, or those of its collaborators, will be successful. The Company expects to continue to incur substantial losses and not generate positive cash flows from operations for at least the next several years. No assurance can be given that the Company can generate sufficient product revenue to become profitable or generate positive cash flows from operations.

Basis of Presentation

These financial statements are prepared in conformity with accounting principles generally accepted in the United States of America.

Use of Estimates

The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make informed estimates and assumptions that affect the amounts reported in the financial statements and disclosures made in the accompanying notes. Actual results could differ materially from those estimates.

Cash, Cash Equivalents and Marketable Securities

Cash and cash equivalents consist of cash and highly liquid securities with original maturities at the date of acquisition of ninety days or less and can be liquidated without prior notice or penalty. Investments with an original maturity of more than ninety days are considered marketable securities and have been classified by management as available-for-sale. These investments are classified as current assets, even though the stated maturity date may be one year or more beyond the current balance sheet date which reflects management’s intention to use the proceeds from sales of these securities to fund its operations, as necessary. Such investments are carried at fair value, with unrealized gains and losses included as a separate component of stockholders’ equity. Realized gains and losses from the sale of available-for-sale securities or the amounts, net of tax, reclassified out of accumulated other comprehensive income (loss), if any, are determined on a specific identification basis.

Restricted Cash

The Company was required to maintain a letter of credit securing an amount equal to twelve months of the then current monthly installment of base rent for the original term of the lease for its facilities, which ended on August 31, 2017. In July 2016, the term of the lease was extended for 16 months through December 2018. During the extended term, the Company was required to maintain a letter of credit securing an amount equal to $0.2 million. At December 31, 2017, restricted cash of $0.2 million was pledged as collateral for the letter of credit. The letter of credit expired on December 31, 2018 and, therefore, no cash was pledged as collateral as of that date.

Concentrations of Credit Risk

Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash equivalents, marketable securities and receivables. The Company invests its excess cash in debt instruments of financial institutions and of corporations with above average credit ratings, in U.S. government obligations, and in money market funds and certificates of deposits at financial institutions.

Property and Equipment

Property and equipment is recorded at cost and depreciation is computed using the straight-line method over the estimated useful lives of the assets. Assets acquired pursuant to capital lease arrangements and leasehold improvements are amortized using the straight-line method over the shorter of the life of the remaining lease term or the remaining useful life of the asset. Manufacturing equipment has estimated useful lives of 5 to 10 years. All other property and equipment have estimated useful lives of 3 to 5 years. Maintenance and repairs of property and equipment are expensed as incurred.

Intangible Assets

Intangible assets include certain costs related to patent applications. The Company capitalizes license fees paid to acquire access to proprietary technology if the technology is expected to have alternative future use in multiple research and development projects. The cost of licensed technology rights is amortized using the straight-line method over the estimated useful life of the technology. Certain costs related to patent applications are amortized over the estimated economic lives of the patents, which is generally 20 years and typically commences at the time the patent application is filed. As of December 31, 2018, the Company had no capitalized patent costs. Amortization expense for licensed technology and capitalized patent cost is included in research and development expenses.

Impairment of Long-lived Assets

The Company reviews long-lived assets for impairment at least annually, quarterly for intangible assets, and whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Should an impairment exist, the impairment loss would be measured based on the excess of the carrying amount of the asset over the asset’s estimated fair value and the loss recognized in current earnings. The Company recognized research and development expense of approximately $0.7 million, $0.0 million and $0.4 million for the years ended December 31, 2018, 2017 and 2016, respectively, related to patents for which the value was deemed to be impaired.

Revenue Recognition

The Company recognizes revenue when control of its products and services is transferred to its customers in an amount that reflects the consideration the Company expects to receive from its customers in exchange for those products and services. This process involves identifying the contract with a customer, determining the performance obligations in the contract, determining the contract price, allocating the contract price to the distinct performance obligations in the contract, and recognizing revenue when the performance obligations have been satisfied. A performance obligation is considered distinct from other obligations in a contract when it provides a benefit to the customer either on its own or together with other resources that are readily available to the customer and is separately identified in the contract. The Company considers a performance obligation satisfied once it has transferred control of a good or service to the customer, meaning the customer has the ability to use and obtain the benefit of the good or service. The Company recognizes revenue for satisfied performance obligations only when it determines there are no uncertainties regarding payment terms or transfer of control.

Research and Development Costs

Research and development costs are expensed as incurred. Research and development costs include salaries and personnel-related costs, supplies and materials, outside services, costs of conducting preclinical and clinical trials, facilities costs and amortization of intangible assets. The Company accounts for its clinical trial costs by estimating the total cost to treat a patient in each clinical trial, and accruing this total cost for the patient over the estimated treatment period, which corresponds with the period over which the services are performed, beginning when the patient enrolls in the clinical trial. This estimated cost includes payments to the site conducting the trial, and patient-related lab and other costs related to the conduct of the trial. Cost per patient varies based on the type of clinical trial, the site of the clinical trial, the method of administration of the treatment, and the number of treatments that a patient receives. Treatment periods vary depending on the clinical trial. The Company makes revisions to the clinical trial cost estimates in the current period, as clinical trials progress.

Manufacturing and Production Costs

Manufacturing and production costs include expenses related to manufacturing contracts and expenses for the production of plasmid DNA for use in the Company’s research and development efforts. Manufacturing expenses related to manufacturing contracts are deferred and expensed when the related revenue is recognized. Deferred contract costs at December 31, 2018 and 2017 were $0.0 million and $10.5 million, respectively. Production expenses related to the Company’s research and development efforts are expensed as incurred.

Net Loss Per Share

Basic and diluted net loss per share has been computed using the weighted-average number of shares of common stock outstanding during the period. The weighted-average number of shares used to compute diluted loss per share excludes any assumed exercise of stock options, and the assumed issuance of common stock under RSUs, as the effect would be antidilutive. Common stock equivalents of 7.2 million, 1.8 million and 7,350 for the years ended December 31, 2018, 2017 and 2016, respectively, were excluded from the calculation because of their antidilutive effect.

Fair Value of Financial Instruments

The carrying amounts of cash, cash equivalents, restricted cash, marketable securities, receivables, accounts payable and accrued expenses at December 31, 2018 and 2017, are considered to approximate fair value because of the short term nature of those items.

Income Taxes

The impact of an uncertain income tax position on the income tax return must be recognized at the largest amount that is more-likely-than-not to be sustained upon audit by the relevant taxing authority. An uncertain income tax position will not be recognized if it has less than a 50% likelihood of being sustained. There were no unrecognized tax benefits recorded by the Company as of the date of adoption in 2007. There are no unrecognized tax benefits included in the balance sheets that would, if recognized, affect the effective tax rate.

Deferred income taxes result primarily from temporary differences between financial and tax reporting. Deferred tax assets and liabilities are determined based on the difference between the financial statement bases and the tax bases of assets and liabilities using enacted tax rates. A valuation allowance is established to reduce a deferred tax asset to the amount that is expected more likely than not to be realized.

The Tax Cuts and Jobs Act (“the Act”) was enacted on December 22, 2017. The Act reduces the U.S. federal corporate tax rate from 35% to 21%. Pursuant to the Securities and Exchange Commission Staff Accounting Bulletin No. 118, Income Tax Accounting Implications of the Tax Cuts and Jobs Act (SAB 118), we have finalized the accounting for the income tax effects of the Tax Legislation and believe the disclosures made in the financial statements as of December 31, 2017 are still accurate.

Comprehensive Loss

Comprehensive loss consists of net loss and certain changes in equity that are excluded from net loss. Comprehensive loss for the years ended December 31, 2018, 2017 and 2016, has been reflected in the accompanying Statements of Comprehensive Loss. Accumulated other comprehensive income (loss), which is included in stockholders’ equity, represents unrealized gains and losses on marketable securities.

Business Segments

The Company operates in one business segment, which is within the United States, and is dedicated to research and development of biopharmaceutical products.

Stock-Based Compensation

The Company records its compensation expense associated with stock options and other forms of equity compensation based on their fair value at the date of grant using the Black-Scholes-Merton option pricing model. Stock-based compensation expense includes amortization related to stock option awards based on the estimated grant date fair value. The compensation expense related to stock options is recognized ratably over the vesting period of the options. In addition, the Company records expense related to RSUs granted based on the fair value of those awards on the grant date. The fair value related to the RSUs is amortized to expense over the vesting term of those awards. Stock-based compensation expense related to stock options and RSUs for the year ended December 31, 2016 includes an estimate of 8.75% for forfeitures. Effective January 1, 2017, the Company adopted ASU No. 2016-09, “Compensation – Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting” which allowed the Company to change its methodology for recording forfeitures from estimated forfeitures to actual forfeitures and recorded an adjustment to beginning retained earnings of $0.1 million.

The fair value of each option award is estimated on the date of grant using the Black-Scholes-Merton valuation model using the assumptions noted in the following table. The expected life of options is based on the Company’s observed historical exercise patterns. The expected volatility of stock options is based upon the historical volatility of the Company’s stock commensurate with the expected life of the option. The risk-free interest rate is based on the implied yield on a U.S. Treasury zero-coupon issue with a remaining term equal to the expected term of the option. The dividend yield reflects that the Company has not paid any cash dividends since inception and does not intend to pay any cash dividends in the foreseeable future.

	Year Ended December 31,
	2018		2017		2016
Assumptions:
Assumed risk-free interest rate	2.34%		1.86%		1.44%
Assumed volatility	60%		72%		72%
Average expected option life	4.5 years		4.5 years		4.5 years
Expected dividend yield		—		—		—

Recent Accounting Pronouncements

In May 2014, the Financial Accounting Standards Board (the “FASB”) issued ASU No. 2014-09, “Revenue from Contracts with Customers” which outlines a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers. The Company adopted the new standard effective January 1, 2018 using the modified retrospective method applied to contracts not completed as of December 31, 2017. As it relates to process validation lots and stock piling lots completed but not delivered as of December 31, 2017 at the request of a customer, the Company concluded that, under ASC 606, the criteria for transfer of control were met prior to January 1, 2018 and as a result, the Company recorded an adjustment as of January 1, 2018 to recognize previously deferred revenue of $11.4 million and previously deferred contract costs of $10.5 million, with an adjustment to retained earnings of $0.9 million. There was no tax impact, as the effect of the implementation for tax purposes was offset by the valuation allowance. The impact of adoption on the Company’s income statement and balance sheet as of December 31, 2018 and for the 12 months then ended was as follows (in thousands):

Income Statement	As Reported			Balances Without Adoption of ASC 606			Effect of Change Increase/(Decrease)
Revenues
Contract revenue	$	1,582		$	13,012		$	(11,430	)
Operating expenses
Manufacturing and production		1,436			11,938			(10,502	)
Net loss		(16,254	)		(15,326	)		928

Balance Sheet	As Reported			Balances Without Adoption of ASC 606			Effect of Change Increase/(Decrease)
Assets
Deferred contract costs	$	—		$	—		$	—
Liabilities
Deferred revenue		30			30			—
Equity
Accumulated deficit		(442,064	)		(442,064	)		—

In February 2016, the FASB issued ASU No. 2016-02, “Leases (Topic 842).” The new standard requires a lessee to record on the balance sheet the assets and liabilities for the rights and obligations created by leases with lease terms of more than 12 months and will require both lessees and lessors to disclose certain key information about lease transactions. The standard is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. The Company will adopt the new standard in the first quarter of 2019. While the Company is continuing to assess the potential impacts of the new standard, the Company estimates that the adoption of ASU No. 2016-02 will have no significant impact on its financial statements.

Short-Term Marketable Securities

12 Months Ended

Dec. 31, 2018

Investments Debt And Equity Securities [Abstract]

Short-Term Marketable Securities

2. Short-Term Marketable Securities

The following is a summary of short-term marketable securities classified as available-for-sale (in thousands):

December 31, 2018

Amortized

Cost

Unrealized

Gain

Unrealized

Loss

Market

Value

U.S. treasuries

$

36,219

$

—

$

18

$

36,201

$

36,219

$

—

$

18

$

36,201

December 31, 2017	Amortized Cost		Unrealized Gain		Unrealized Loss		Market Value
U.S. treasuries	$	34,462	$	—	$	29	$	34,433
Certificates of deposit		1,225		—		—		1,225
	$	35,687	$	—	$	29	$	35,658

At December 31, 2018, none of these securities were scheduled to mature outside of one year. There were no net realized gains (losses) on sales of available-for-sale securities for the years ended December 31, 2018, 2017 and 2016. None of these investments have been in a continuous unrealized loss position for more than 12 months as of December 31, 2018 and 2017.

Long-Term Investments

12 Months Ended

Dec. 31, 2018

Investments All Other Investments [Abstract]

Long-Term Investments

3. Long-Term Investments

As of December 31, 2018, the Company held an auction rate security with a par value of $2.5 million. This auction rate security has not experienced a successful auction since the liquidity issues experienced in the global credit and capital markets in 2008. As a result the security is classified as a long-term investment as it is scheduled to mature in 2038. The security was rated BBB by Standard and Poor’s as of December 31, 2018. The security continues to pay interest according to its stated terms.

The valuation of the Company’s auction rate security is subject to uncertainties that are difficult to predict. The fair value of the security is estimated utilizing a discounted cash flow analysis. The key drivers of the valuation model include the expected term, collateral underlying the security investment, the creditworthiness of the counterparty, the timing of expected future cash flows, discount rates, liquidity and the expected holding period. The security was also compared, when possible, to other observable market data for securities with similar characteristics. As of December 31, 2018, the inputs used in the Company’s discounted cash flow analysis assumed an interest rate of 6.71%, an estimated redemption period of five years and a discount rate of 1.0%. Based on the valuation of the security, the Company has recognized cumulative losses of $0.4 million as of December 31, 2018, none of which were realized during the year ended December 31, 2018. The losses, when recognized, are included in investment and other income. The market value of the security has partially recovered. Included in other comprehensive (loss) income are unrealized gains (losses) of $139,000, $108,000 and $(6,000) for the years ended December 31, 2018, 2017 and 2016, respectively. As of December 31, 2018, the Company had recorded cumulative unrealized gains of $0.6 million. The resulting carrying value of the auction rate security at December 31, 2018, was $2.4 million. Any future decline in market value may result in additional losses being recognized.

Fair Value Measurements

12 Months Ended

Dec. 31, 2018

Fair Value Disclosures [Abstract]

Fair Value Measurements

4. Fair Value Measurements

The Company measures fair value as an exit price, representing the amount 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. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. Fair value measurements are based on a three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value as follows:

•

Level 1: Observable inputs such as quoted prices in active markets;

•

Level 2: Inputs, other than the quoted prices in active markets, that are observable either directly or indirectly; and

•

Level 3: Unobservable inputs for which there is little or no market data, which require the reporting entity to develop its own assumptions.

Cash equivalents, marketable securities and long-term investments measured at fair value are classified in the table below in one of the three categories described above (in thousands):

	Fair Value Measurements
December 31, 2018	Level 1		Level 2		Level 3		Total
Money market funds	$	11,523	$	—	$	—	$	11,523
U.S. treasuries		36,201		—		—		36,201
Auction rate securities		—		—		2,386		2,386
	$	47,724	$	—	$	2,386	$	50,110

	Fair Value Measurements
December 31, 2017	Level 1		Level 2		Level 3		Total
Certificates of deposit	$	1,225	$	—	$	—	$	1,225
Money market funds		21,760		—		—		21,760
U.S. treasuries		34,433		—		—		34,433
Auction rate securities		—		—		2,209		2,209
	$	57,418	$	—	$	2,209	$	59,627

The Company’s investments in U.S. treasury securities, certificates of deposit and money market funds are valued based on publicly available quoted market prices for identical securities as of December 31, 2018. The Company determines the fair value of other government-sponsored enterprise related securities with the aid of valuations provided by third parties using proprietary valuation models and analytical tools. These valuation models and analytical tools use market pricing or similar instruments that are both objective and publicly available, including matrix pricing or reported trades, benchmark yields, broker/dealer quotes, issuer spreads, two-sided markets, benchmark securities, bids and/or offers. The Company validates the valuations received from its primary pricing vendors for its level 2 securities by examining the inputs used in that vendor’s pricing process and determines whether they are reasonable and observable. The Company also compares those valuations to recent reported trades for those securities. The Company did not adjust any of the valuations received from these third parties with respect to any of its level 2 securities at December 31, 2018. The valuation of the Company’s investment in auction rate securities is more fully described in Note 3.

Activity for assets measured at fair value using significant unobservable inputs (Level 3) is presented in the table below (in thousands):

Balance at December 31, 2017	$	2,209
Total net realized gains included in earnings		—
Total net unrealized gains included in other comprehensive income		177
Net transfers in and/out of Level 3		—
Balance at December 31, 2018	$	2,386
Amount of total losses for the period included in net loss attributable to the change in unrealized gains or losses relating to assets still held at December 31, 2018	$	—

Total cumulative unrealized losses of $0.1 million relate to Level 3 assets still held as of December 31, 2018, none of which were recognized during the years ended December 31, 2018, 2017 and 2016. The losses, when recognized, are included in investment and other income.

Other Balance Sheet Accounts

12 Months Ended

Dec. 31, 2018

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Other Balance Sheet Accounts

5. Other Balance Sheet Accounts

Property and equipment consisted of the following at December 31 (in thousands):

	2018			2017
Equipment	$	3,270		$	16,908
Leasehold improvements		—			8,144
		3,270			25,052
Less accumulated depreciation and amortization		(3,170	)		(24,446	)
	$	100		$	606

Depreciation and amortization of equipment and leasehold improvements for the years ended December 31, 2018, 2017 and 2016, was $0.1 million, $0.6 million and $0.9 million, respectively.

Intangible assets consisted of the following at December 31 (in thousands):

	2018		2017
Patent application costs	$	—	$	1,500
Accumulated amortization patent costs		—		(797	)
	$	—	$	703

Amortization of licensed technology rights and patent application costs was $0.1 million for each of the years ended December 31, 2018, 2017 and 2016.

Accounts payable and accrued expenses consisted of the following at December 31 (in thousands):

	2018		2017
Employee compensation	$	1,768	$	2,654
Clinical trial accruals		1,000		1,017
Accounts payable		412		1,213
Other accrued liabilities		371		333
	$	3,551	$	5,217

Significant Contract, License and Royalty Agreements

12 Months Ended

Dec. 31, 2018

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Significant Contract, License and Royalty Agreements

6. Significant Contract, License and Royalty Agreements

Contracts

Astellas

In July 2011, the Company entered into license agreements with Astellas, granting Astellas exclusive, worldwide, royalty-bearing licenses under certain of the Company’s know-how and intellectual property to develop and commercialize certain products containing plasmids encoding certain forms of glycoprotein B and/or phosphoprotein 65. Under the terms of the license agreements, Astellas paid a nonrefundable upfront license fee of $25.0 million. In 2012, the Company received a $10.0 million milestone payment upon finalization of the trial design for a Phase 3 registration trial of ASP0113 in hematopoietic stem cell transplant recipients.

The Company identified the deliverables at the inception of the agreements. The Company determined that the license and related know-how, the development and regulatory services and the drug product supply individually represent separate units of accounting, because each deliverable has standalone value. The best estimated selling prices for these units of accounting was determined based on market conditions, the terms of comparable collaborative arrangements for similar technology in the pharmaceutical and biotechnology industry and entity-specific factors, such as the terms of the Company’s previous collaborative agreements, the Company’s pricing practices and pricing objectives and the nature of the research and development services to be performed for the partner. The arrangement consideration was allocated to the deliverables based on the relative selling price method.

The amount of allocable arrangement consideration is limited to amounts that are fixed or determinable; therefore, the amount allocated to the licenses was limited to the extent of cash received. As a result, during the years ended December 31, 2018, 2017 and 2016, the Company recognized $0.0 million, $0.3 million and $1.5 million, respectively, related to the license fee and know-how. The Company recognized the amounts allocated to research and development services as revenues under the agreements as the related services were delivered and as reimbursements were received. During the years ended December 31, 2018, 2017 and 2016, the Company recognized $1.2 million, $12.9 million and $10.1 million, respectively, of revenue related to contract services delivered. The Company recognized as revenue the amounts allocated to the sales of drug product when the sale of that drug product had met all required specifications and the related title and risk of loss and damages passed to Astellas. During the years ended December 31, 2018, 2017 and 2016, the Company recognized $0.0 million, $0.0 million and $2.4 million, respectively, of revenue related to drug product delivered.

In January 2018, Astellas announced the results from a Phase 3 trial of ASP0113 in approximately 515 CMV seropositive subjects undergoing HCT procedures. Top-line results from the Phase 3 study demonstrated that the trial did not meet its primary endpoint in CMV end organ disease. Based on these results, Astellas determined to cease further clinical development of ASP0113 and has terminated the license agreement.

In-licensing Agreements

Astellas

In March 2015, the Company entered into a license agreement with Astellas which grants to the Company exclusive worldwide license to develop and commercialize a novel antifungal, VL-2397. As consideration for the rights under the license, the Company issued 86,121 shares of our common stock to Astellas and made an up-front payment of $250,000 in cash. The License Agreement provides for potential development, regulatory and sales milestone payments totaling up to $99.0 million, the vast majority of which are payable upon achievement of commercial and sales milestones, and single-digit royalties on net sales of commercial products. The Company is responsible for the worldwide development, manufacturing and commercialization of licensed products, at the Company’s cost, and we are required to use commercially reasonable efforts with respect to such development and commercialization activities.

The license agreement, unless terminated earlier, will continue until expiration of Vical’s royalty obligations with respect to licensed products. Either party may terminate the license agreement earlier if the other party materially breaches the agreement and does not cure the breach within a specified notice period, or upon the other party’s insolvency. Astellas may terminate the license agreement earlier if Vical or any of its affiliates or sublicensees oppose or challenge any of the licensed patents. Vical may terminate the license agreement on a country-by-country basis for reasonable scientific, regulatory, commercial, financial, ethical or other reasons.

Milestone Payments

The Company may be required to make future payments to its licensors based on the achievement of milestones set forth in various in-licensing agreements. In most cases, these milestone payments are based on the achievement of development or regulatory milestones, including the exercise of options to obtain licenses related to specific disease targets, commencement of various phases of clinical trials, filing of product license applications, approval of product licenses from the FDA or a foreign regulatory agency, and the first commercial sale of a related product. Payment for the achievement of milestones under the Company’s in-license agreements is highly speculative and subject to a number of contingencies.

The aggregate amount of additional milestone payments that the Company could be required to pay under its active in-license agreements in place at December 31, 2018, is approximately $99.0 million. These amounts assume that all remaining milestones associated with the milestone payments are met. In the event that product license approval for any of the related products is obtained, the Company may be required to make royalty payments in addition to these milestone payments. Although the Company believes that some of the milestones contained in its in-license agreements may be achieved, it is highly unlikely that a significant number of them will be achieved. Because the milestones are contingent the Company is not in a position to reasonably estimate how much, if any, of the potential milestone payments will ultimately be paid. Additionally, under the in-license agreements, many of the milestone events are related to progress in clinical trials which the Company estimates will take several years to achieve.

Commitments and Contingencies

12 Months Ended

Dec. 31, 2018

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

7. Commitments and Contingencies

Facility Leases

The Company occupied approximately 68,400 square feet of manufacturing, research laboratory and office space until July 2018 when the Company entered into an agreement with Genopis, Inc. (“Genopis”) to sell the Company’s idle manufacturing assets for $1.7 million. As part of the agreement, Genopis agreed to sublease 51,400 square feet of the Company’s facility through the remaining term of the Company’s lease which expired on December 31, 2018. Genopis was also required to sign a long-term lease with the facility’s landlord beginning on January 1, 2019. Genopis agreed to sublease 17,000 square feet of the facility to the Company at no cost for the one-year period ending on December 31, 2019. A gain on the sale of assets of $2.3 million was recorded, with $1.1 million attributable to the fair value of rent for the space that the Company is occupying at no cost. The amount was recorded to deferred rent expense in Receivables and Other Assets and is being amortized as rent expense through December 31, 2019.

Rent expense for the years ended December 31, 2018, 2017 and 2016 was $1.5 million, $2.4 million, and $2.6 million, respectively.

At December 31, 2018, there were no future minimum rental payments due by the Company.

Other Contingencies

In the ordinary course of business, the Company may become a party to additional lawsuits involving various matters. The Company is unaware of any such lawsuits presently pending against it which, individually or in the aggregate, are deemed to be material to the Company’s financial condition or results of operations.

The Company prosecutes its intellectual property vigorously to obtain the broadest valid scope for its patents. Due to uncertainty of the ultimate outcome of these matters, the impact on future operating results or the Company’s financial condition is not subject to reasonable estimates.

Stockholders' Equity

12 Months Ended

Dec. 31, 2018

Equity [Abstract]

Stockholders' Equity

8. Stockholders’ Equity

As of the date of this filing the Company has on file a shelf registration statement that allows it to raise up to an additional $40.0 million from the sale of common stock, preferred stock, debt securities and/or warrants. Specific terms of any offering under the shelf registration statements and the securities involved would be established at the time of sale.

In November 2017, the Company sold 9,194,286 shares of its common stock in a public offering at a price of $1.75 per share, including an overallotment of 2,142,857 shares issued at a price of $1.75 per share, and pre-funded warrants to purchase 7,234,285 shares of common stock at a purchase price of $1.74 per share. Net proceeds from the offering, after deducting underwriting discounts and commissions and other offering expenses payable by the Company, totaled $26.4 million. The pre-funded warrants have an exercise price of $0.01 per share and are immediately exercisable and may be exercised at any time.

In October 2016, we entered into an At-The-Market Issuance Sales Agreement, or the ATM Agreement, with IFS Securities, Inc. (doing business as Brinson Patrick, a division of IFS Securities, Inc.), or BP, under which we could issue and sell up to $10.0 million of shares of our common stock from time to time. The ATM expired in October 2018. For the 12 months ended December 31, 2017, we sold 1,509,370 shares under the ATM Agreement and received gross proceeds of $4.3 million. We sold no shares under the agreement in 2018.

On August 1, 2016, the Company entered into a stock purchase agreement with AnGes, Inc., or AnGes, an existing stockholder, to purchase 1,841,420 shares of the Company’s common stock in a private placement. The shares were sold at a price of $4.24 per share. Gross proceeds totaled approximately $7.8 million. The private placement closed on August 2, 2016. The shares are subject to a two-year lock-up period during which they may not be sold and AnGes has agreed to not increase its ownership position beyond 19.9% and to refrain from taking certain other actions with respect to the Company’s stock, subject to certain conditions. AnGes is entitled to have a representative attend meetings of the Company’s Board of Directors in a non-voting capacity and may in the future be entitled to have a representative appointed to the Company’s Board of Directors, subject to certain conditions. AnGes has also agreed to vote its shares in accordance with the recommendations of the Company’s Board of Directors for so long as it continues to hold a specified percentage of the Company’s outstanding common stock. The Company also agreed under certain circumstances in the future to register the private placement shares for resale by AnGes.

Stock Based Compensation

12 Months Ended

Dec. 31, 2018

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock Based Compensation

9. Stock Based Compensation

The Company has a stock-based compensation plan which is described below. Total stock-based compensation expense of $0.4 million, $0.8 million and $1.0 million was recognized for the years ended December 31, 2018, 2017 and 2016, respectively. Total stock-based compensation expense was allocated to research and development, manufacturing and production and general and administrative expense as follows (in thousands):

	Year Ended December 31,
	2018			2017		2016
Research and development	$	154		$	239	$	290
Manufacturing and production		(67	)		124		111
General and administrative		274			393		589
Total stock-based compensation expense	$	361		$	756	$	990
Cash received from RSU grants	$	—		$	—	$	1

Stock Incentive Plan

The Company has a stock incentive plan, under which 3,370,000 shares of common stock, subject to adjustment as provided in the plan, are reserved for issuance to employees, non-employee directors and consultants of the Company. As of December 31, 2018 there were 2,927,509 shares reserved for future issuance under the plan. The plan provides for the grant of incentive and nonstatutory stock options and the direct award or sale of shares, including restricted stock. The exercise price of stock options must equal at least the fair market value of the underlying common stock on the date of grant. The maximum term of options granted under the plan is ten years. Except for annual grants to non-employee directors which vest at the next annual meeting, options generally vest 25% on the first anniversary of the date of grant, with the balance vesting quarterly over the remaining three years. The plan also limits the number of options that may be granted to any plan participant in a single calendar year to 1,300,000 shares.

The Company has granted RSUs to executive officers, other executives, and employees under the stock incentive plan. There were no RSUs granted in the years ended December 31, 2018, 2017 or 2016. These RSUs generally vest 25% on the first anniversary date of the grant, with the remaining rights vesting quarterly over the remaining three years and, once vested, allow the participants to acquire the underlying shares of common stock at par value. The participants are not entitled to sell or transfer any unvested RSUs and are not entitled to vote or receive dividends on any shares of common stock covered by the RSUs prior to the acquisition of such shares. Granted but unvested RSUs are forfeited at termination of employment. Compensation expense related to the RSUs for the years ended December 31, 2018, 2017, and 2016 was approximately $23,000, $95,000 and $316,000, respectively.

The following table summarizes stock option transactions under the Company’s stock incentive plans for the years ended December 31, 2018, 2017 and 2016:

	Shares			Weighted Average Exercise Price
Outstanding December 31, 2015		945,584		$	23.27
Granted		339,975		$	3.51
Exercised		—		$	—
Forfeited		(82,758	)	$	24.37
Outstanding December 31, 2016		1,202,801		$	17.61
Granted		590,200		$	2.30
Exercised		—		$	—
Forfeited		(68,330	)	$	22.17
Outstanding December 31, 2017		1,724,671		$	12.19
Granted		547,701		$	1.77
Exercised		—		$	—
Forfeited		(376,816	)	$	10.00
Outstanding December 31, 2018		1,895,556		$	9.61
Vested and unvested options expected to vest as of December 31, 2018		1,895,556		$	9.61

The number of underlying shares and weighted average exercise price of options exercisable at December 31, 2018, 2017 and 2016, were 1,222,876 shares at $13.71, 1,005,400 shares at $18.72, and 808,639 shares at $23.43, respectively. The weighted average remaining contractual term of options outstanding and options exercisable at December 31, 2018, was 6.6 years and 5.5 years, respectively. The weighted average remaining contractual term of vested and unvested options expected to vest at December 31, 2018, was 6.6 years. The aggregate intrinsic value of options outstanding and options exercisable at December 31, 2018 was $0.0 million and $0.0 million, respectively. As of December 31, 2018, the total unrecognized compensation cost related to unvested options was $0.2 million, which is expected to be recognized over a weighted-average period of 1.39 years.

The weighted average grant-date fair value of options granted during the years ended December 31, 2018, 2017 and 2016, was $0.81, $1.21 and $1.85 per share, respectively. There were no options exercised during the years ended December 31, 2018, 2017 or 2016. At December 31, 2018, there were 1,000,068 shares available for grant under the Company’s stock incentive plans.

A summary of the outstanding RSUs as of December 31, 2018, and changes during the year then ended is presented below:

	Shares			Weighted Average Grant-Date Fair Value per Share
Unvested at December 31, 2017		21,204		$	10.43
Granted		—		$	—
Vested		(16,187	)	$	5.96
Cancelled		(942	)	$	10.30
Unvested at December 31, 2018		4,075		$	10.20

There were no RSUs granted in the years ended December 31, 2018, 2017 or 2016. As of December 31, 2018, the total unrecognized compensation cost related to unvested RSUs was $1,000, which is expected to be recognized over a weighted average period of one year. The aggregate grant-date fair value of shares subject to RSUs vested during the years ended December 31, 2018, 2017 and 2016, was $0.1 million, $0.3 million and $0.8 million, respectively. As of December 31, 2018, there were 27,809 shares of common stock underlying RSUs that were fully vested but the issuance of such shares has been deferred.

Related Party Transaction

12 Months Ended

Dec. 31, 2018

Related Party Transaction

10. Related Party Transaction

On April 4, 2017, the Company entered into a research collaboration agreement with AnGes. As of the date of the transaction, AnGes held 18.6% of the outstanding stock of the Company. Pursuant to the collaboration agreement, AnGes agreed to make a non-refundable payment to the Company of $750,000 and the Company agreed to conduct certain research activities related to a development program targeting chronic hepatitis B. An amendment to the agreement was executed in September 2018 that added an additional non-refundable payment from AnGes to the Company of $145,000. In exchange for the payments, AnGes received an option to negotiate exclusive rights in Japan related to the program. The parties also agreed to share the costs of prosecuting and maintaining intellectual property rights arising from the research program after such costs reach a specified limit. The decision to sell, license or sublicense rights is a contingent event within the Company’s control. There are no guarantees for any outcomes of the research activities, no purchase obligations required by the Company and no debt or equity arrangements connected with the research activities. There are no other written or oral side agreements between the Company and AnGes that indicate that the funding of the research activities will be repaid. The Company is responsible for the conduct of the research activities. The upfront payments were deferred and recognized as contract revenue as the related research costs are incurred. Contract revenue relating to this collaboration of $0.4 million and $0.5 million was recognized in the years ended December 31, 2018 and 2017, respectively.

Restructuring Costs

12 Months Ended

Dec. 31, 2018

Restructuring And Related Activities [Abstract]

Restructuring Costs

11. Restructuring Costs

In January 2018, the Company and Astellas announced that ASP0113 did not meet its primary endpoint in a Phase 3 clinical study in CMV end organ disease, after which Astellas informed the Company that it was terminating further development. As a result, the Company restructured its operations to conserve capital, which included a staff reduction of 40 employees and the write-off of certain intangible assets. The Company recorded charges for one-time employee termination benefits of $1.1 million and for intangible asset impairments of $0.3 million during the twelve months ended December 31, 2018. Overhead costs associated with the former manufacturing facility of $1.2 million have been recognized as general and administrative expense during the twelve months ended December 31, 2018. The following table summarizes the components of the restructuring charges (in thousands):

	Employee
	Termination		Asset
	Benefits		Impairments		Total
Research and development	$	272	$	267	$	539
Manufacturing and production		735		—		735
General and administrative		117		—		117
	$	1,124	$	267	$	1,391

The following table sets forth the accrual activity for employee termination benefits for the 12 months ended December 31, 2018 (in thousands). No additional charges are expected to be incurred.


Balance at December 31, 2017	$	—
Accruals		1,124
Payments		(1,124	)
Balance at December 31, 2018	$	—

Sale of Manufacturing Assets

12 Months Ended

Dec. 31, 2018

Sale Of Manufacturing Assets [Abstract]

Sale of Manufacturing Assets

12. Sale of Manufacturing Assets

In July 2018, the Company entered into an agreement with Genopis to sell the Company’s idle manufacturing assets for $1.7 million. As part of the agreement, Genopis agreed to sublease 51,400 square feet of the Company’s facility through the remaining term of the Company’s lease, which expired on December 31, 2018. Genopis was also required to sign a long-term lease with the facility’s landlord beginning on January 1, 2019. Genopis agreed to sublease 17,000 square feet of the facility (consisting of lab and office space) to the Company at no cost for the one-year period ending on December 31, 2019. A gain on the sale of assets of $2.3 million was recorded and is included in Investment and Other Income, Net. The gain includes $1.1 million for the fair value of rent for the lab and office space that the Company is occupying at no cost, with the offset recorded to deferred rent expense in Receivables and Other Assets.

Income Taxes

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

Income Taxes

13. Income Taxes

At December 31, 2018, the Company had deferred tax assets of $87.4 million. Due to uncertainties surrounding the Company’s ability to generate future taxable income to realize these assets, a full valuation allowance has been established to offset the net deferred tax asset. Pursuant to Sections 382 and 383 of the Internal Revenue Code, or IRC, annual use of the Company’s net operating loss and credit carryforwards may be limited in the event a cumulative change in ownership of more than 50% occurs within a three-year period. The Company determined that such an ownership change occurred on December 29, 2006, as defined in the provisions of Section 382 of the IRC as a result of various stock issuances used to finance the Company’s operations. Such ownership change resulted in annual limitations on the utilization of tax attributes, including net operating loss carryforwards and tax credits. The Company estimates that $94.6 million of its net operating loss carryforwards were effectively eliminated under Section 382 for federal tax purposes. A portion of the remaining net operating losses limited by Section 382 become available each year. The Company also estimates that $11.8 million of its research and development credits and other tax credits were effectively eliminated under Section 383 for federal purposes. The Company’s Section 382 analysis was completed through December 31, 2011. The Company has not, however, conducted a Section 382 study for any periods subsequent to December 31, 2011, and as such, the Company cannot provide any assurance that a change in ownership within the meaning of the IRC has not occurred since that date. There is a risk that additional changes in ownership could have occurred since that date. If a change in ownership were to have occurred, additional net operating loss and tax credit carryforwards could be eliminated or restricted. If eliminated, the related asset would be removed from the deferred tax asset schedule with a corresponding reduction in the valuation allowance.

Deferred income taxes result primarily from temporary differences between financial and tax reporting. Deferred tax assets and liabilities are determined based on the difference between the financial statement basis and the tax basis of assets and liabilities using enacted tax rates. A valuation allowance is established to reduce deferred tax assets to the amount that is expected more likely than not to be realized.

Significant components of the Company’s deferred tax assets as of December 31, 2018 and 2017 are listed below. A valuation allowance of $87.4 million and $83.6 million at December 31, 2018 and 2017, respectively, has been recognized to offset the net deferred tax assets as realization of such assets is uncertain.

Amounts for the years ended December 31 were as follows (in thousands):

Deferred Tax Assets	2018			2017
Net operating losses	$	63,933		$	59,756
Credit carryovers		11,304			10,527
Depreciation and amortization		10,635			10,893
Deferred revenue		—			634
Accruals and reserves		275			450
Other		1,242			1,350
Total deferred tax assets		87,389			83,610
Less valuation allowance		(87,389	)		(83,610	)
Net deferred tax assets	$	—		$	—

The reconciliation between the provision for income taxes and income taxes computed using the U.S. federal statutory corporate tax rate were as follows for the years ended December 31 (in thousands):

	2018			2017			2016
Computed “expected” tax benefit	$	(3,421	)	$	(4,425	)	$	(3,051	)
State income taxes, net of federal benefit		(676	)		(268	)		(534	)
Tax effect of:
Change in valuation allowance		2,632			(31,665	)		(6,030	)
Impact of Tax Cuts and Jobs Act		—			34,439			—
Rate change		—			—			—
Expiration of prior year credits and net operating losses		1,386			1,256			692
Research and development and other tax credit carryovers		(1,320	)		—			—
Stock compensation		121			458			491
Uncertain tax positions		1,357			276			9,010
Other		(79	)		(71	)		(578	)
Provision for income taxes	$	—		$	—		$	—

As of December 31, 2018 and 2017, the Company had available federal net operating loss carryforwards of approximately $331.3 million and $319.1 million, respectively. The net operating loss generated in 2018 of $18.8 million will carry forward indefinitely and be available to offset up to 80% of future taxable income each year. Net operating losses generated prior to 2018 will expire from 2019 through 2038. In addition, the Company had federal research and development credit and orphan drug credit carryforwards of $27.1 million and $26.3 million as of December 31, 2018 and 2017, respectively, to reduce future federal income taxes, if any. These carryforwards expire from 2019 through 2038 and are subject to review and possible adjustment by the Internal Revenue Service. The Company also has available California state net operating loss carryforwards of approximately $264.6 million and $254.9 million as of December 31, 2018 and 2017, respectively, which expire from 2028 to 2038. In addition, the Company had California research and development credits of approximately $9.3 million and $8.8 million as of December 31, 2018 and 2017, respectively, to reduce future California income tax, if any. The California research and development credits do not expire. All federal and state net operating loss and credit carryforwards listed above are reflected before the reduction for amounts effectively eliminated under Sections 382 and 383. Based upon statute, federal and state losses and credits are expected to expire as follows (in millions):

Expiration Date	Federal NOLs		State NOLs		Federal R&D Credits		Federal Orphan Drug Credits		State R&D Credits
2019	$	5.3	$	—	$	0.4	$	0.6	$	—
2020		12.3		—		0.3		2.3		—
2021		7.5		—		0.3		2.0		—
2022		22.4		—		0.5		1.6		—
2023		22.4		—		0.3		0.9		—
2024 and thereafter		242.6		264.6		3.4		14.5		—
Indefinite		18.8		—		—		—		9.3
	$	331.3	$	264.6	$	5.2	$	21.9	$	9.3

In March 2016, the FASB issued Accounting Standards Update No. 2016-09, "Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting (“ASU 2016-09”). ASU 2016-09 simplifies how several aspects of share-based payments are accounted for and presented in the financial statements. ASU 2016-09 was effective for public companies for annual reporting periods beginning after December 15, 2016. Upon adoption of this ASU as of January 1, 2017, unrecognized excess tax benefits of approximately $(0.2) million were recognized with the impact recorded to retained earnings including a corresponding change to the valuation allowance.

The Tax Cuts and Jobs Act (the “Act”) was enacted on December 22, 2017. The Act reduced the U.S. federal corporate tax rate from 35% to 21% beginning in 2018. The Company applied the guidance in SAB 118 when accounting for the enactment-date effects of the Act in 2017 and throughout 2018. As of December 31, 2017, the Company remeasured certain deferred tax assets and liabilities based on the rates at which they were expected to reverse in the future (which is generally 21%), by recording a provisional amount of $34.4 million, which was fully offset by the valuation allowance. Upon further analysis of certain aspects of the Act and refinement of our calculations during the twelve months ended December 31, 2018, the Company determined that no adjustment was necessary to the provisional amount.

The Company recognizes liabilities for uncertain tax positions based on a two-step process. The first step is to evaluate the tax position for recognition by determining if the weight of available evidence indicates that it is more likely than not that the position will be sustained on audit, including resolution of related appeals or litigation processes, if any. The second step is to measure the tax benefit as the largest amount that is more than 50% likely of being realized upon settlement. While the Company believes that it has appropriate support for the positions taken on its tax returns, the Company regularly assesses the potential outcome of examinations by tax authorities in determining the adequacy of its provision for income taxes.

The following table summarizes the activity related to the Company’s unrecognized tax benefits (in thousands):

	2018		2017			2016
Beginning balance	$	17,836	$	17,561		$	4,340
Increases (decreases) related to prior year tax positions		48		(140	)		12,348
Increases related to current year tax positions		1,616		415			873
Ending balance	$	19,500	$	17,836		$	17,561

As of December 31, 2018 and 2017, the Company had gross unrecognized tax benefits of $19.5 million and $17.8 million, respectively, none of which would affect the effective tax rate. The Company does not anticipate any significant decreases in its unrecognized tax benefits over the next 12 months. The Company’s policy is to recognize the interest expense and/or penalties related to income tax matters as a component of income tax expense. The Company had no accrual for interest or penalties on its balance sheets at December 31, 2018 or December 31, 2017, and has not recognized interest and/or penalties in its statements of operations for any of the years ended December 31, 2018, 2017 or 2016.

The Company is subject to taxation in the United States and state jurisdictions where applicable. The Company’s tax years for 1998 and forward are subject to examination by the United States and California tax authorities due to the carryforward of unutilized net operating losses and R&D credits.

Employee Benefit Plan

12 Months Ended

Dec. 31, 2018

Compensation And Retirement Disclosure [Abstract]

Employee Benefit Plan

14. Employee Benefit Plan

The Company has a defined contribution savings plan under section 401(k) of the IRC. The plan covers substantially all employees. The Company matches employee contributions made to the plan according to a specified formula. The Company’s matching contributions totaled approximately $0.1 million, $0.2 million and $0.1 million for the years ended December 31, 2018, 2017 and 2016, respectively.

Summary of (Unaudited) Quarterly Financial Information

12 Months Ended

Dec. 31, 2018

Quarterly Financial Information Disclosure [Abstract]

Summary of (Unaudited) Quarterly Financial Information

15. Summary of (Unaudited) Quarterly Financial Information

The following is a summary of the Company’s (unaudited) quarterly results of operations for the years ended December 31 (in thousands, except per share amounts):

2018:	March 31,			June 30,			Sept. 30,			Dec. 31,
Total revenues	$	716		$	735		$	47		$	124
Total operating expenses		7,217			5,863			4,113			4,075
Net loss		(6,270	)		(4,868	)		(1,511	)		(3,605	)
Basic and diluted net loss per share (1)		(0.29	)		(0.22	)		(0.07	)		(0.17	)

2017:	March 31,			June 30,			Sept. 30,			Dec. 31,
Total revenues	$	3,205		$	3,421		$	3,240		$	3,953
Total operating expenses		6,118			6,832			6,421			7,834
Net income (loss)		(2,824	)		(3,320	)		(3,088	)		(3,728	)
Basic and diluted net loss per share (1)		(0.25	)		(0.30	)		(0.27	)		(0.21	)

(1)	Net income (loss) per share is computed independently for each quarter and the full year based upon respective shares outstanding. Therefore, the sum of the quarterly loss per share amounts may not equal the annual amounts reported.

Subsequent Event

12 Months Ended

Dec. 31, 2018

Subsequent Events [Abstract]

Subsequent Event

16. Subsequent Event

In February 2019, the Company decided to discontinue the Phase 2 clinical trial of VL-2397. As a result, the Company will be restructuring its operations to conserve capital, which will include a staff reduction and may include a write-off of certain assets. The Company will record these restructuring charges during the three months ended March 31, 2019.

Organization and Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2018

Accounting Policies [Abstract]

Organization and Business Activity

Vical Incorporated, or the Company, a Delaware corporation, was incorporated in April 1987 and has devoted substantially all of its resources since that time to its research and development programs. The Company researches and develops biopharmaceutical products, including those based on its patented DNA delivery technologies for the prevention and treatment of serious or life-threatening diseases.

All of the Company’s potential products are in research and development phases. No revenues have been generated from the sale of any such products, nor are any such revenues expected for at least the next several years. The Company earns revenue from research and development agreements with pharmaceutical collaborators and from contract manufacturing agreements. Most of the Company’s product candidates will require significant additional research and development efforts, including extensive preclinical and clinical testing. All product candidates that advance to clinical testing will require regulatory approval prior to commercial use, and will require significant costs for commercialization. There can be no assurance that the Company’s research and development efforts, or those of its collaborators, will be successful. The Company expects to continue to incur substantial losses and not generate positive cash flows from operations for at least the next several years. No assurance can be given that the Company can generate sufficient product revenue to become profitable or generate positive cash flows from operations.

Basis of Presentation

These financial statements are prepared in conformity with accounting principles generally accepted in the United States of America.

Use of Estimates

The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make informed estimates and assumptions that affect the amounts reported in the financial statements and disclosures made in the accompanying notes. Actual results could differ materially from those estimates.

Cash, Cash Equivalents and Marketable Securities

Cash and cash equivalents consist of cash and highly liquid securities with original maturities at the date of acquisition of ninety days or less and can be liquidated without prior notice or penalty. Investments with an original maturity of more than ninety days are considered marketable securities and have been classified by management as available-for-sale. These investments are classified as current assets, even though the stated maturity date may be one year or more beyond the current balance sheet date which reflects management’s intention to use the proceeds from sales of these securities to fund its operations, as necessary. Such investments are carried at fair value, with unrealized gains and losses included as a separate component of stockholders’ equity. Realized gains and losses from the sale of available-for-sale securities or the amounts, net of tax, reclassified out of accumulated other comprehensive income (loss), if any, are determined on a specific identification basis.

Restricted Cash

The Company was required to maintain a letter of credit securing an amount equal to twelve months of the then current monthly installment of base rent for the original term of the lease for its facilities, which ended on August 31, 2017. In July 2016, the term of the lease was extended for 16 months through December 2018. During the extended term, the Company was required to maintain a letter of credit securing an amount equal to $0.2 million. At December 31, 2017, restricted cash of $0.2 million was pledged as collateral for the letter of credit. The letter of credit expired on December 31, 2018 and, therefore, no cash was pledged as collateral as of that date.

Concentrations of Credit Risk

Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash equivalents, marketable securities and receivables. The Company invests its excess cash in debt instruments of financial institutions and of corporations with above average credit ratings, in U.S. government obligations, and in money market funds and certificates of deposits at financial institutions.

Property and Equipment

Property and equipment is recorded at cost and depreciation is computed using the straight-line method over the estimated useful lives of the assets. Assets acquired pursuant to capital lease arrangements and leasehold improvements are amortized using the straight-line method over the shorter of the life of the remaining lease term or the remaining useful life of the asset. Manufacturing equipment has estimated useful lives of 5 to 10 years. All other property and equipment have estimated useful lives of 3 to 5 years. Maintenance and repairs of property and equipment are expensed as incurred.

Intangible Assets

Intangible assets include certain costs related to patent applications. The Company capitalizes license fees paid to acquire access to proprietary technology if the technology is expected to have alternative future use in multiple research and development projects. The cost of licensed technology rights is amortized using the straight-line method over the estimated useful life of the technology. Certain costs related to patent applications are amortized over the estimated economic lives of the patents, which is generally 20 years and typically commences at the time the patent application is filed. As of December 31, 2018, the Company had no capitalized patent costs. Amortization expense for licensed technology and capitalized patent cost is included in research and development expenses.

Impairment of Long-lived Assets

The Company reviews long-lived assets for impairment at least annually, quarterly for intangible assets, and whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Should an impairment exist, the impairment loss would be measured based on the excess of the carrying amount of the asset over the asset’s estimated fair value and the loss recognized in current earnings. The Company recognized research and development expense of approximately $0.7 million, $0.0 million and $0.4 million for the years ended December 31, 2018, 2017 and 2016, respectively, related to patents for which the value was deemed to be impaired.

Revenue Recognition

The Company recognizes revenue when control of its products and services is transferred to its customers in an amount that reflects the consideration the Company expects to receive from its customers in exchange for those products and services. This process involves identifying the contract with a customer, determining the performance obligations in the contract, determining the contract price, allocating the contract price to the distinct performance obligations in the contract, and recognizing revenue when the performance obligations have been satisfied. A performance obligation is considered distinct from other obligations in a contract when it provides a benefit to the customer either on its own or together with other resources that are readily available to the customer and is separately identified in the contract. The Company considers a performance obligation satisfied once it has transferred control of a good or service to the customer, meaning the customer has the ability to use and obtain the benefit of the good or service. The Company recognizes revenue for satisfied performance obligations only when it determines there are no uncertainties regarding payment terms or transfer of control.

Research and Development Costs

Research and development costs are expensed as incurred. Research and development costs include salaries and personnel-related costs, supplies and materials, outside services, costs of conducting preclinical and clinical trials, facilities costs and amortization of intangible assets. The Company accounts for its clinical trial costs by estimating the total cost to treat a patient in each clinical trial, and accruing this total cost for the patient over the estimated treatment period, which corresponds with the period over which the services are performed, beginning when the patient enrolls in the clinical trial. This estimated cost includes payments to the site conducting the trial, and patient-related lab and other costs related to the conduct of the trial. Cost per patient varies based on the type of clinical trial, the site of the clinical trial, the method of administration of the treatment, and the number of treatments that a patient receives. Treatment periods vary depending on the clinical trial. The Company makes revisions to the clinical trial cost estimates in the current period, as clinical trials progress.

Manufacturing and Production Costs

Manufacturing and production costs include expenses related to manufacturing contracts and expenses for the production of plasmid DNA for use in the Company’s research and development efforts. Manufacturing expenses related to manufacturing contracts are deferred and expensed when the related revenue is recognized. Deferred contract costs at December 31, 2018 and 2017 were $0.0 million and $10.5 million, respectively. Production expenses related to the Company’s research and development efforts are expensed as incurred.

Net Loss Per Share

Basic and diluted net loss per share has been computed using the weighted-average number of shares of common stock outstanding during the period. The weighted-average number of shares used to compute diluted loss per share excludes any assumed exercise of stock options, and the assumed issuance of common stock under RSUs, as the effect would be antidilutive. Common stock equivalents of 7.2 million, 1.8 million and 7,350 for the years ended December 31, 2018, 2017 and 2016, respectively, were excluded from the calculation because of their antidilutive effect.

Fair Value of Financial Instruments

The carrying amounts of cash, cash equivalents, restricted cash, marketable securities, receivables, accounts payable and accrued expenses at December 31, 2018 and 2017, are considered to approximate fair value because of the short term nature of those items.

Income Taxes

The impact of an uncertain income tax position on the income tax return must be recognized at the largest amount that is more-likely-than-not to be sustained upon audit by the relevant taxing authority. An uncertain income tax position will not be recognized if it has less than a 50% likelihood of being sustained. There were no unrecognized tax benefits recorded by the Company as of the date of adoption in 2007. There are no unrecognized tax benefits included in the balance sheets that would, if recognized, affect the effective tax rate.

Deferred income taxes result primarily from temporary differences between financial and tax reporting. Deferred tax assets and liabilities are determined based on the difference between the financial statement bases and the tax bases of assets and liabilities using enacted tax rates. A valuation allowance is established to reduce a deferred tax asset to the amount that is expected more likely than not to be realized.

The Tax Cuts and Jobs Act (“the Act”) was enacted on December 22, 2017. The Act reduces the U.S. federal corporate tax rate from 35% to 21%. Pursuant to the Securities and Exchange Commission Staff Accounting Bulletin No. 118, Income Tax Accounting Implications of the Tax Cuts and Jobs Act (SAB 118), we have finalized the accounting for the income tax effects of the Tax Legislation and believe the disclosures made in the financial statements as of December 31, 2017 are still accurate.

Comprehensive Loss

Comprehensive loss consists of net loss and certain changes in equity that are excluded from net loss. Comprehensive loss for the years ended December 31, 2018, 2017 and 2016, has been reflected in the accompanying Statements of Comprehensive Loss. Accumulated other comprehensive income (loss), which is included in stockholders’ equity, represents unrealized gains and losses on marketable securities.

Business Segments

The Company operates in one business segment, which is within the United States, and is dedicated to research and development of biopharmaceutical products.

Stock-Based Compensation

The Company records its compensation expense associated with stock options and other forms of equity compensation based on their fair value at the date of grant using the Black-Scholes-Merton option pricing model. Stock-based compensation expense includes amortization related to stock option awards based on the estimated grant date fair value. The compensation expense related to stock options is recognized ratably over the vesting period of the options. In addition, the Company records expense related to RSUs granted based on the fair value of those awards on the grant date. The fair value related to the RSUs is amortized to expense over the vesting term of those awards. Stock-based compensation expense related to stock options and RSUs for the year ended December 31, 2016 includes an estimate of 8.75% for forfeitures. Effective January 1, 2017, the Company adopted ASU No. 2016-09, “Compensation – Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting” which allowed the Company to change its methodology for recording forfeitures from estimated forfeitures to actual forfeitures and recorded an adjustment to beginning retained earnings of $0.1 million.

The fair value of each option award is estimated on the date of grant using the Black-Scholes-Merton valuation model using the assumptions noted in the following table. The expected life of options is based on the Company’s observed historical exercise patterns. The expected volatility of stock options is based upon the historical volatility of the Company’s stock commensurate with the expected life of the option. The risk-free interest rate is based on the implied yield on a U.S. Treasury zero-coupon issue with a remaining term equal to the expected term of the option. The dividend yield reflects that the Company has not paid any cash dividends since inception and does not intend to pay any cash dividends in the foreseeable future.

	Year Ended December 31,
	2018		2017		2016
Assumptions:
Assumed risk-free interest rate	2.34%		1.86%		1.44%
Assumed volatility	60%		72%		72%
Average expected option life	4.5 years		4.5 years		4.5 years
Expected dividend yield		—		—		—

Recent Accounting Pronouncements

In May 2014, the Financial Accounting Standards Board (the “FASB”) issued ASU No. 2014-09, “Revenue from Contracts with Customers” which outlines a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers. The Company adopted the new standard effective January 1, 2018 using the modified retrospective method applied to contracts not completed as of December 31, 2017. As it relates to process validation lots and stock piling lots completed but not delivered as of December 31, 2017 at the request of a customer, the Company concluded that, under ASC 606, the criteria for transfer of control were met prior to January 1, 2018 and as a result, the Company recorded an adjustment as of January 1, 2018 to recognize previously deferred revenue of $11.4 million and previously deferred contract costs of $10.5 million, with an adjustment to retained earnings of $0.9 million. There was no tax impact, as the effect of the implementation for tax purposes was offset by the valuation allowance. The impact of adoption on the Company’s income statement and balance sheet as of December 31, 2018 and for the 12 months then ended was as follows (in thousands):

Income Statement	As Reported			Balances Without Adoption of ASC 606			Effect of Change Increase/(Decrease)
Revenues
Contract revenue	$	1,582		$	13,012		$	(11,430	)
Operating expenses
Manufacturing and production		1,436			11,938			(10,502	)
Net loss		(16,254	)		(15,326	)		928

Balance Sheet	As Reported			Balances Without Adoption of ASC 606			Effect of Change Increase/(Decrease)
Assets
Deferred contract costs	$	—		$	—		$	—
Liabilities
Deferred revenue		30			30			—
Equity
Accumulated deficit		(442,064	)		(442,064	)		—

In February 2016, the FASB issued ASU No. 2016-02, “Leases (Topic 842).” The new standard requires a lessee to record on the balance sheet the assets and liabilities for the rights and obligations created by leases with lease terms of more than 12 months and will require both lessees and lessors to disclose certain key information about lease transactions. The standard is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. The Company will adopt the new standard in the first quarter of 2019. While the Company is continuing to assess the potential impacts of the new standard, the Company estimates that the adoption of ASU No. 2016-02 will have no significant impact on its financial statements.

Organization and Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2018

Accounting Policies [Abstract]

Schedule of Assumptions Used to Estimate the Fair Value of Each Option Award

The fair value of each option award is estimated on the date of grant using the Black-Scholes-Merton valuation model using the assumptions noted in the following table.

	Year Ended December 31,
	2018		2017		2016
Assumptions:
Assumed risk-free interest rate	2.34%		1.86%		1.44%
Assumed volatility	60%		72%		72%
Average expected option life	4.5 years		4.5 years		4.5 years
Expected dividend yield		—		—		—

Summary of Impact of Adoption of New Accounting Standard on Income Statement and Balance Sheet

The impact of adoption on the Company’s income statement and balance sheet as of December 31, 2018 and for the 12 months then ended was as follows (in thousands)

Income Statement	As Reported			Balances Without Adoption of ASC 606			Effect of Change Increase/(Decrease)
Revenues
Contract revenue	$	1,582		$	13,012		$	(11,430	)
Operating expenses
Manufacturing and production		1,436			11,938			(10,502	)
Net loss		(16,254	)		(15,326	)		928

Balance Sheet	As Reported			Balances Without Adoption of ASC 606			Effect of Change Increase/(Decrease)
Assets
Deferred contract costs	$	—		$	—		$	—
Liabilities
Deferred revenue		30			30			—
Equity
Accumulated deficit		(442,064	)		(442,064	)		—

Short-Term Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2018

Investments Debt And Equity Securities [Abstract]

Summary of Short-Term Marketable Securities

The following is a summary of short-term marketable securities classified as available-for-sale (in thousands):

December 31, 2018

Amortized

Cost

Unrealized

Gain

Unrealized

Loss

Market

Value

U.S. treasuries

$

36,219

$

—

$

18

$

36,201

$

36,219

$

—

$

18

$

36,201

December 31, 2017	Amortized Cost		Unrealized Gain		Unrealized Loss		Market Value
U.S. treasuries	$	34,462	$	—	$	29	$	34,433
Certificates of deposit		1,225		—		—		1,225
	$	35,687	$	—	$	29	$	35,658

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2018

Fair Value Disclosures [Abstract]

Summary of Cash Equivalents, Marketable Securities and Long-Term Investments Measured at Fair Value

Cash equivalents, marketable securities and long-term investments measured at fair value are classified in the table below in one of the three categories described above (in thousands):

	Fair Value Measurements
December 31, 2018	Level 1		Level 2		Level 3		Total
Money market funds	$	11,523	$	—	$	—	$	11,523
U.S. treasuries		36,201		—		—		36,201
Auction rate securities		—		—		2,386		2,386
	$	47,724	$	—	$	2,386	$	50,110

	Fair Value Measurements
December 31, 2017	Level 1		Level 2		Level 3		Total
Certificates of deposit	$	1,225	$	—	$	—	$	1,225
Money market funds		21,760		—		—		21,760
U.S. treasuries		34,433		—		—		34,433
Auction rate securities		—		—		2,209		2,209
	$	57,418	$	—	$	2,209	$	59,627

Summary of Activity for Assets Measured at Fair Value Using Significant Unobservable Inputs

Activity for assets measured at fair value using significant unobservable inputs (Level 3) is presented in the table below (in thousands):

Balance at December 31, 2017	$	2,209
Total net realized gains included in earnings		—
Total net unrealized gains included in other comprehensive income		177
Net transfers in and/out of Level 3		—
Balance at December 31, 2018	$	2,386
Amount of total losses for the period included in net loss attributable to the change in unrealized gains or losses relating to assets still held at December 31, 2018	$	—

- Definition

Tabular disclosure of financial instruments measured at fair value, including those classified in shareholders' equity measured on a recurring or nonrecurring basis. Disclosures include, but are not limited to, fair value measurements recorded and the reasons for the measurements, level within the fair value hierarchy in which the fair value measurements are categorized and transfers between levels 1 and 2. Nonrecurring fair value measurements are those that are required or permitted in the statement of financial position in particular circumstances.

+ References + Details

Other Balance Sheet Accounts (Tables)

12 Months Ended

Dec. 31, 2018

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Summary of Property and Equipment

Property and equipment consisted of the following at December 31 (in thousands):

	2018			2017
Equipment	$	3,270		$	16,908
Leasehold improvements		—			8,144
		3,270			25,052
Less accumulated depreciation and amortization		(3,170	)		(24,446	)
	$	100		$	606

Summary of Intangible Assets

Intangible assets consisted of the following at December 31 (in thousands):

	2018		2017
Patent application costs	$	—	$	1,500
Accumulated amortization patent costs		—		(797	)
	$	—	$	703

Summary of Accounts Payable and Accrued Expenses

Accounts payable and accrued expenses consisted of the following at December 31 (in thousands):

	2018		2017
Employee compensation	$	1,768	$	2,654
Clinical trial accruals		1,000		1,017
Accounts payable		412		1,213
Other accrued liabilities		371		333
	$	3,551	$	5,217

Stock Based Compensation (Tables)

12 Months Ended

Dec. 31, 2018

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Total Stock-Based Compensation Expense

Total stock-based compensation expense was allocated to research and development, manufacturing and production and general and administrative expense as follows (in thousands):

	Year Ended December 31,
	2018			2017		2016
Research and development	$	154		$	239	$	290
Manufacturing and production		(67	)		124		111
General and administrative		274			393		589
Total stock-based compensation expense	$	361		$	756	$	990
Cash received from RSU grants	$	—		$	—	$	1

Summary of Stock Option Transactions under Company's Stock Incentive Plans

The following table summarizes stock option transactions under the Company’s stock incentive plans for the years ended December 31, 2018, 2017 and 2016:

	Shares			Weighted Average Exercise Price
Outstanding December 31, 2015		945,584		$	23.27
Granted		339,975		$	3.51
Exercised		—		$	—
Forfeited		(82,758	)	$	24.37
Outstanding December 31, 2016		1,202,801		$	17.61
Granted		590,200		$	2.30
Exercised		—		$	—
Forfeited		(68,330	)	$	22.17
Outstanding December 31, 2017		1,724,671		$	12.19
Granted		547,701		$	1.77
Exercised		—		$	—
Forfeited		(376,816	)	$	10.00
Outstanding December 31, 2018		1,895,556		$	9.61
Vested and unvested options expected to vest as of December 31, 2018		1,895,556		$	9.61

Summary of Outstanding RSUs

A summary of the outstanding RSUs as of December 31, 2018, and changes during the year then ended is presented below:

	Shares			Weighted Average Grant-Date Fair Value per Share
Unvested at December 31, 2017		21,204		$	10.43
Granted		—		$	—
Vested		(16,187	)	$	5.96
Cancelled		(942	)	$	10.30
Unvested at December 31, 2018		4,075		$	10.20

Restructuring Costs (Tables)

12 Months Ended

Dec. 31, 2018

Restructuring And Related Activities [Abstract]

Summary of Components of Restructuring Charges

The following table summarizes the components of the restructuring charges (in thousands):

	Employee
	Termination		Asset
	Benefits		Impairments		Total
Research and development	$	272	$	267	$	539
Manufacturing and production		735		—		735
General and administrative		117		—		117
	$	1,124	$	267	$	1,391

Schedule of Accrual Activity for Employee Termination Benefits

The following table sets forth the accrual activity for employee termination benefits for the 12 months ended December 31, 2018 (in thousands). No additional charges are expected to be incurred.


Balance at December 31, 2017	$	—
Accruals		1,124
Payments		(1,124	)
Balance at December 31, 2018	$	—

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

Summary of Deferred Tax Assets

Amounts for the years ended December 31 were as follows (in thousands):

Deferred Tax Assets	2018			2017
Net operating losses	$	63,933		$	59,756
Credit carryovers		11,304			10,527
Depreciation and amortization		10,635			10,893
Deferred revenue		—			634
Accruals and reserves		275			450
Other		1,242			1,350
Total deferred tax assets		87,389			83,610
Less valuation allowance		(87,389	)		(83,610	)
Net deferred tax assets	$	—		$	—

Reconciliation Between Provision for Income Taxes and Income Taxes

The reconciliation between the provision for income taxes and income taxes computed using the U.S. federal statutory corporate tax rate were as follows for the years ended December 31 (in thousands):

	2018			2017			2016
Computed “expected” tax benefit	$	(3,421	)	$	(4,425	)	$	(3,051	)
State income taxes, net of federal benefit		(676	)		(268	)		(534	)
Tax effect of:
Change in valuation allowance		2,632			(31,665	)		(6,030	)
Impact of Tax Cuts and Jobs Act		—			34,439			—
Rate change		—			—			—
Expiration of prior year credits and net operating losses		1,386			1,256			692
Research and development and other tax credit carryovers		(1,320	)		—			—
Stock compensation		121			458			491
Uncertain tax positions		1,357			276			9,010
Other		(79	)		(71	)		(578	)
Provision for income taxes	$	—		$	—		$	—

Summary of Expected Expiry of Net Operating Losses and Tax Credits

Based upon statute, federal and state losses and credits are expected to expire as follows (in millions):

Expiration Date	Federal NOLs		State NOLs		Federal R&D Credits		Federal Orphan Drug Credits		State R&D Credits
2019	$	5.3	$	—	$	0.4	$	0.6	$	—
2020		12.3		—		0.3		2.3		—
2021		7.5		—		0.3		2.0		—
2022		22.4		—		0.5		1.6		—
2023		22.4		—		0.3		0.9		—
2024 and thereafter		242.6		264.6		3.4		14.5		—
Indefinite		18.8		—		—		—		9.3
	$	331.3	$	264.6	$	5.2	$	21.9	$	9.3

Summary of Activity Related to Unrecognized Tax Benefits

The following table summarizes the activity related to the Company’s unrecognized tax benefits (in thousands):

	2018		2017			2016
Beginning balance	$	17,836	$	17,561		$	4,340
Increases (decreases) related to prior year tax positions		48		(140	)		12,348
Increases related to current year tax positions		1,616		415			873
Ending balance	$	19,500	$	17,836		$	17,561

Summary of (Unaudited) Quarterly Financial Information (Tables)

12 Months Ended

Dec. 31, 2018

Quarterly Financial Information Disclosure [Abstract]

Summary of Company's (Unaudited) Quarterly Results of Operations

The following is a summary of the Company’s (unaudited) quarterly results of operations for the years ended December 31 (in thousands, except per share amounts):

2018:	March 31,			June 30,			Sept. 30,			Dec. 31,
Total revenues	$	716		$	735		$	47		$	124
Total operating expenses		7,217			5,863			4,113			4,075
Net loss		(6,270	)		(4,868	)		(1,511	)		(3,605	)
Basic and diluted net loss per share (1)		(0.29	)		(0.22	)		(0.07	)		(0.17	)

2017:	March 31,			June 30,			Sept. 30,			Dec. 31,
Total revenues	$	3,205		$	3,421		$	3,240		$	3,953
Total operating expenses		6,118			6,832			6,421			7,834
Net income (loss)		(2,824	)		(3,320	)		(3,088	)		(3,728	)
Basic and diluted net loss per share (1)		(0.25	)		(0.30	)		(0.27	)		(0.21	)

(1)	Net income (loss) per share is computed independently for each quarter and the full year based upon respective shares outstanding. Therefore, the sum of the quarterly loss per share amounts may not equal the annual amounts reported.

Organization and Summary of Significant Accounting Policies - Additional Information (Detail)	1 Months Ended	12 Months Ended
	Jul. 31, 2016	Dec. 31, 2018 USD ($) Segment shares	Dec. 31, 2017 USD ($) shares	Dec. 31, 2016 USD ($) shares	Jan. 01, 2018 USD ($)	Jan. 01, 2017 USD ($)
Organization and Summary of Significant Accounting Policies [Line Items]
Maximum period for cash and highly liquid securities with original maturities		90 days or less
Minimum period for marketable securities classified as available-for-sale with original maturities		More than 90 days
Amount of letter of credit, description		The Company was required to maintain a letter of credit securing an amount equal to twelve months of the then current monthly installment of base rent for the original term of the lease for its facilities, which ended on August 31, 2017.
Restricted cash		$ 0	$ 192,000
Secured letter of credit for the extended lease term		200,000
Renewal period for lease for lease beyond its expiration	16 months
Renewal lease agreement expiry date	Dec. 31, 2018
Research and development expense		673,000	0	$ 374,000
Deferred contract costs		$ 0	$ 10,500,000
Common stock equivalents excluded from the calculation of diluted net income per share \| shares		7,200,000	1,800,000	7,350
Likelihood threshold for recognition of uncertain tax position		50.00%
Unrecognized tax benefits			$ 0
U.S. federal corporate tax rate		21.00%	35.00%
Number of business segment \| Segment		1
Deferred revenue		$ 30,000	$ 11,700,000
Deferred contract costs		0	$ 10,502,000
Stock Options and RSUs [Member]
Organization and Summary of Significant Accounting Policies [Line Items]
Estimated forfeiture rate of stock-based compensation				8.75%
ASU No. 2016-09 [Member]
Organization and Summary of Significant Accounting Policies [Line Items]
Adjustment to beginning retained earnings due to adoption of new accounting standard						$ 100,000
ASU No. 2014-09 [Member]
Organization and Summary of Significant Accounting Policies [Line Items]
Adjustment to beginning retained earnings due to adoption of new accounting standard					$ 900,000
Deferred revenue					11,400,000
Deferred contract costs					$ 10,500,000
ASU No. 2016-02 [Member]
Organization and Summary of Significant Accounting Policies [Line Items]
New accounting pronouncements, impact on financial statements		$ 0
Patent application costs [Member]
Organization and Summary of Significant Accounting Policies [Line Items]
Estimated economic lives of the patents		20 years
Capitalized patent cost		$ 0
Minimum [Member] \| Manufacturing Equipment [Member]
Organization and Summary of Significant Accounting Policies [Line Items]
Estimated useful life of property and equipment		5 years
Minimum [Member] \| All other property and equipment [Member]
Organization and Summary of Significant Accounting Policies [Line Items]
Estimated useful life of property and equipment		3 years
Maximum [Member] \| Manufacturing Equipment [Member]
Organization and Summary of Significant Accounting Policies [Line Items]
Estimated useful life of property and equipment		10 years
Maximum [Member] \| All other property and equipment [Member]
Organization and Summary of Significant Accounting Policies [Line Items]
Estimated useful life of property and equipment		5 years

Organization and Summary of Significant Accounting Policies - Summary of Fair Value of Share-Based Compensation, Stock Options (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Assumed risk-free interest rate	2.34%	1.86%	1.44%
Assumed volatility	60.00%	72.00%	72.00%
Average expected option life	4 years 6 months	4 years 6 months	4 years 6 months
Expected dividend yield	0.00%	0.00%	0.00%

Organization and Summary of Significant Accounting Policies - Summary of Impact of Adoption of New Accounting Standard on Income Statement and Balance Sheet (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2018
Revenues:
Contract revenue									$ 1,582	$ 13,401	$ 12,804
Operating expenses:
Manufacturing and production									1,436	6,479	6,291
Net loss	$ (3,605)	$ (1,511)	$ (4,868)	$ (6,270)	$ (3,728)	$ (3,088)	$ (3,320)	$ (2,824)	(16,254)	(12,960)	$ (8,973)
Assets
Deferred contract costs	0				10,502				0	10,502
Liabilities
Deferred revenue	30				11,700				30	11,700
Equity
Accumulated deficit	(442,064)				$ (426,738)				(442,064)	$ (426,738)
ASU No. 2014-09 [Member]
Assets
Deferred contract costs												$ 10,500
Liabilities
Deferred revenue												$ 11,400
ASU No. 2014-09 [Member] \| Balances Without Adoption of ASC 606 [Member]
Revenues:
Contract revenue									13,012
Operating expenses:
Manufacturing and production									11,938
Net loss									(15,326)
Assets
Deferred contract costs	0								0
Liabilities
Deferred revenue	30								30
Equity
Accumulated deficit	(442,064)								(442,064)
ASU No. 2014-09 [Member] \| Effect of Change Increase/(Decrease) [Member]
Revenues:
Contract revenue									(11,430)
Operating expenses:
Manufacturing and production									(10,502)
Net loss									928
Assets
Deferred contract costs	0								0
Liabilities
Deferred revenue	0								0
Equity
Accumulated deficit	$ 0								$ 0

Short-Term Marketable Securities - Summary of Short-Term Marketable Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 36,219	$ 35,687
Unrealized Gain	0	0
Unrealized Loss	18	29
Market Value	36,201	35,658
U.S. treasuries [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	36,219	34,462
Unrealized Gain	0	0
Unrealized Loss	18	29
Market Value	$ 36,201	34,433
Certificates of deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		1,225
Unrealized Gain		0
Unrealized Loss		0
Market Value		$ 1,225

Short-Term Marketable Securities - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Investments Debt And Equity Securities [Abstract]
Available-for-sale securities maturing outside of one year	$ 0
Net realized gains (losses) on sales of available-for-sale securities	0	$ 0	$ 0
Available-for-sale securities in a continuous unrealized loss position more than 12 months	$ 0	$ 0

Long-Term Investments - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Investment [Line Items]
Auction rate securities held, at par value	$ 2,500,000
Maturity of long-term investment	2038
Recognized cumulative losses	$ 400,000
Unrealized gains (losses) on auction rate securities	139,000	$ 108,000	$ (6,000)
Cumulative unrealized gains	600,000
Carrying value of auction rate security	$ 2,386,000	$ 2,209,000
Assumed interest rate	6.71%
Estimated redemption period	5 years
Recognized cumulative losses realized	$ 0
Discount Rate [Member]
Investment [Line Items]
Fair value input discount rate	1.0

Fair Value Measurements - Summary of Cash Equivalents, Marketable Securities and Long-Term Investments Measured at Fair Value (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 50,110	$ 59,627
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	47,724	57,418
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	2,386	2,209
Money market funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	11,523	21,760
Money market funds [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	11,523	21,760
Money market funds [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Money market funds [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
U.S. treasuries [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	36,201	34,433
U.S. treasuries [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	36,201	34,433
U.S. treasuries [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
U.S. treasuries [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Auction rate securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	2,386	2,209
Auction rate securities [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Auction rate securities [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Auction rate securities [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 2,386	2,209
Certificates of deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		1,225
Certificates of deposit [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		1,225
Certificates of deposit [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		0
Certificates of deposit [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		$ 0

Fair Value Measurements - Summary of Activity for Assets Measured at Fair Value Using Significant Unobservable Inputs (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($)
Fair Value Disclosures [Abstract]
Balance at December 31, 2017	$ 2,209
Total net realized gains included in earnings	0
Total net unrealized gains included in other comprehensive income	177
Net transfers in and/out of Level 3	0
Balance at December 31, 2018	2,386
Amount of total losses for the period included in net loss attributable to the change in unrealized gains or losses relating to assets still held at December 31, 2018	$ 0

Fair Value Measurements - Additional Information (Detail) - Level 3 [Member] - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total cumulative unrealized losses related to Level3 assets	$ 100,000
Unrealized losses	$ 0	$ 0	$ 0

Other Balance Sheet Accounts - Summary of Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Total of property and equipment	$ 3,270	$ 25,052
Less accumulated depreciation and amortization	(3,170)	(24,446)
Property and equipment, net	100	606
Equipment [Member]
Property, Plant and Equipment [Line Items]
Total of property and equipment	3,270	16,908
Leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Total of property and equipment	$ 0	$ 8,144

Other Balance Sheet Accounts - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Balance Sheet Related Disclosures [Abstract]
Depreciation and amortization of equipment and leasehold improvements	$ 0.1	$ 0.6	$ 0.9
Amortization of licensed technology rights and patent application costs	$ 0.1	$ 0.1	$ 0.1

Other Balance Sheet Accounts - Summary of Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Net total of intangible assets	$ 0	$ 703
Patent application costs [Member]
Finite-Lived Intangible Assets [Line Items]
Total of summary of intangible assets	0	1,500
Accumulated amortization	$ 0	$ (797)

Other Balance Sheet Accounts - Summary of Accounts Payable and Accrued Expenses (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Payables And Accruals [Abstract]
Employee compensation	$ 1,768	$ 2,654
Clinical trial accruals	1,000	1,017
Accounts payable	412	1,213
Other accrued liabilities	371	333
Total accounts payable and accrued expenses	$ 3,551	$ 5,217

Significant Contract, License and Royalty Agreements - Additional Information (Detail) - USD ($)	1 Months Ended		12 Months Ended
	Mar. 31, 2015	Jul. 31, 2011	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2012
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Contract revenue			$ 1,582,000	$ 13,401,000	$ 12,804,000
Additional milestone payments related to active in-license agreements			99,000,000
Collaborative Arrangement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payment upon finalization of the trial design						$ 10,000,000
Revenue related to contract services delivered			1,200,000	12,900,000	10,100,000
Revenue related to drug product delivered			0	0	2,400,000
Collaborative Arrangement [Member] \| Astellas In-License Agreements [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Restricted stock issued, shares	86,121
Potential future milestone payments	$ 99,000,000
Collaborative Arrangement [Member] \| Astellas In-License Agreements [Member] \| Research and development [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Cash payment for license agreement	$ 250,000
Collaborative Arrangement [Member] \| License Fee Revenue [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Contract revenue		$ 25,000,000
Collaborative Arrangement [Member] \| License Fee And Know-How [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Contract revenue			$ 0	$ 300,000	$ 1,500,000

Commitments and Contingencies - Additional Information (Detail)		1 Months Ended		12 Months Ended
	Jul. 31, 2016 USD ($) ft²	Jul. 31, 2018 USD ($) ft²	Jul. 31, 2016	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($) ft²	Dec. 31, 2016 USD ($) ft²
Operating Leased Assets [Line Items]
Renewal lease agreement expiry date			Dec. 31, 2018
Gain on the sale of assets		$ 2,300,000		$ 2,286,000	$ 0	$ 0
Gain related to deferred rent		1,100,000		1,067,000	0	0
Rent expense				1,500,000	$ 2,400,000	$ 2,600,000
Future minimum rental payments				$ 0
Genopis Inc [Member]
Operating Leased Assets [Line Items]
Area for leasing facility of manufacturing, research laboratory and office space \| ft²					68,400
Sale of idle manufacturing assets		$ 1,700,000
Genopis Inc [Member] \| Period Through December 31, 2018 [Member]
Operating Leased Assets [Line Items]
Area of square feet agreed to sublease of facility \| ft²		51,400
Renewal lease agreement expiry date		Dec. 31, 2018
Sublease expiration date		Dec. 31, 2018
Genopis Inc [Member] \| Period Ending December 31, 2019 [Member]
Operating Leased Assets [Line Items]
Area of square feet agreed to sublease of facility \| ft²	0	17,000			0	0
Long-term lease beginning date		Jan. 01, 2019
Facility lease cost	$ 0	$ 0			$ 0	$ 0
Facility sublease expiration period		1 year
Sublease expiration date		Dec. 31, 2019

Stockholders' Equity - Additional Information (Detail) - USD ($)		1 Months Ended	12 Months Ended
	Aug. 01, 2016	Nov. 30, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016
Stockholders Equity [Line Items]
Sale of common stock, preferred stock, debt securities and warrants			$ 40,000,000
At-The-Market Issuance Sales Agreement, maximum value of common stock to be issued						$ 10,000,000
Shares of common stock issued during period under At-The-Market Issuance Sales Agreement			0	1,509,370
Gross proceeds from the sales agreement				$ 4,300,000
Private placement, share lock-up period	2 years
Maximum [Member]
Stockholders Equity [Line Items]
Equity position under stock purchase agreement	19.90%
Common Stock [Member]
Stockholders Equity [Line Items]
Shares issued				10,704,000	1,841,000
Pre-funded warrants to purchase common stock		7,234,285
Pre-funded warrants to purchase common stock, price per share		$ 1.74
Net proceeds from offering		$ 26,400,000
Pre-funded warrants exercise price per share		$ 0.01
Public Offering [Member] \| Common Stock [Member]
Stockholders Equity [Line Items]
Shares issued		9,194,286
Public offering, price per share		$ 1.75
Overallotment [Member] \| Common Stock [Member]
Stockholders Equity [Line Items]
Shares issued		2,142,857
Public offering, price per share		$ 1.75
Stock Purchase Agreement with AnGes, MG, Inc in Private Placement [Member]
Stockholders Equity [Line Items]
Pre-funded warrants to purchase common stock, price per share	$ 4.24
Number of shares of common stock sold under the sales agreement	1,841,420
Private placement, gross proceeds	$ 7,800,000
Private placement, closing date	Aug. 02, 2016

Stock Based Compensation - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	$ 400,000	$ 800,000	$ 1,000,000
Common stock reserved	3,370,000
Shares reserved for future issuance	2,927,509
Maximum term of options granted	10 years
Number of options to be granted to any one individual	1,300,000
Number of underlying shares exercisable	1,222,876	1,005,400	808,639
Weighted average exercise price of options exercisable	$ 13.71	$ 18.72	$ 23.43
Weighted average remaining contractual term of options outstanding	6 years 7 months 6 days
Weighted average remaining contractual term of options exercisable	5 years 6 months
Weighted average remaining contractual term of vested and unvested options expected to vest	6 years 7 months 6 days
Aggregate intrinsic value of options outstanding	$ 0
Aggregate intrinsic value of options exercisable	0
Unrecognized compensation cost related to unvested options	$ 200,000
Unvested stock-based awards expected to be recognized, weighted-average period	1 year 4 months 20 days
Weighted average grant-date fair value of options granted	$ 0.81	$ 1.21	$ 1.85
Number of options exercised	0	0	0
Shares available for grant	1,000,068
Aggregate grant-date fair value of RSUs vested	$ 100,000	$ 300,000	$ 800,000
Common stock underlying RSUs that were fully vested	27,809
Restricted stock units (RSUs) [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	$ 23,000	$ 95,000	$ 316,000
Aggregate RSUs granted	0	0	0
Unvested stock-based awards expected to be recognized, weighted-average period	1 year
Aggregate grant-date fair value of RSUs granted	$ 0	$ 0	$ 0
Total unrecognized compensation cost related to unvested RSUs	$ 1,000
Share-based Compensation Award, Tranche One [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of options vested	25.00%
Share-based Compensation Award, Tranche One [Member] \| Restricted stock units (RSUs) [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of options vested	25.00%	25.00%	25.00%

Stock Based Compensation - Summary of Total Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 361	$ 756	$ 990
Cash received from RSU grants			1
Research and development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	154	239	290
Manufacturing and production [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	(67)	124	111
General and administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 274	$ 393	$ 589

Stock Based Compensation - Summary of Stock Option Transactions under Company's Stock Incentive Plans (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Shares Outstanding, Beginning Balance	1,724,671	1,202,801	945,584
Shares, Granted	547,701	590,200	339,975
Shares, Exercised	0	0	0
Shares, Forfeited	(376,816)	(68,330)	(82,758)
Shares Outstanding, Ending Balance	1,895,556	1,724,671	1,202,801
Shares Vested and unvested options expected to vest as of December 31, 2018	1,895,556
Weighted Average Exercise Price, Beginning Balance	$ 12.19	$ 17.61	$ 23.27
Weighted Average Exercise Price, Granted	1.77	2.30	3.51
Weighted Average Exercise Price, Exercised	0	0	0
Weighted Average Exercise Price, Forfeited	10.00	22.17	24.37
Weighted Average Exercise Price, Ending Balance	9.61	$ 12.19	$ 17.61
Weighted Average Exercise Price, Vested and unvested options expected to vest as of December 31, 2018	$ 9.61

Stock Based Compensation - Summary of Outstanding RSUs (Detail) - Restricted stock units (RSUs) [Member] - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares Unvested, Beginning Balance	21,204
Shares, Granted	0	0	0
Shares, Vested	(16,187)
Shares, Cancelled	(942)
Shares Unvested, Ending Balance	4,075	21,204
Weighted Average Grant-Date Fair Value per Share, Unvested, Beginning Balance	$ 10.43
Weighted Average Grant-Date Fair Value per Share, Granted	0
Weighted Average Grant-Date Fair Value per Share, Vested	5.96
Weighted Average Grant-Date Fair Value per Share, Cancelled	10.30
Weighted Average Grant-Date Fair Value per Share, Unvested, Ending Balance	$ 10.20	$ 10.43

Related Party Transaction - Additional Information (Detail) - Research Collaboration Agreement [Member] - AnGes MG, Inc [Member] - USD ($)		12 Months Ended
	Apr. 04, 2017	Dec. 31, 2018	Dec. 31, 2017	Sep. 30, 2018
Related Party Transaction [Line Items]
Percentage of common stock outstanding	18.60%
Non- refundable amount receivable under research collaboration agreement	$ 750,000			$ 145,000
Contract revenue		$ 400,000	$ 500,000

Restructuring Costs - Additional Information (Detail) $ in Thousands	1 Months Ended	12 Months Ended
	Jan. 31, 2018 Employee	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Restructuring Cost And Reserve [Line Items]
Number of staff reduced \| Employee	40
One-time employee termination benefits		$ 1,100
Overhead costs associated with manufacturing facility		1,436	$ 6,479	$ 6,291
Intangible asset impairment charges		267
General and administrative [Member]
Restructuring Cost And Reserve [Line Items]
Overhead costs associated with manufacturing facility		$ 1,200

Restructuring Costs - Summary of Components of Restructuring Charges (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($)
Restructuring Cost And Reserve [Line Items]
Employee Termination Benefits	$ 1,124
Asset Impairments	267
Total	1,391
Research and development [Member]
Restructuring Cost And Reserve [Line Items]
Employee Termination Benefits	272
Asset Impairments	267
Total	539
Manufacturing and production [Member]
Restructuring Cost And Reserve [Line Items]
Employee Termination Benefits	735
Total	735
General and administrative [Member]
Restructuring Cost And Reserve [Line Items]
Employee Termination Benefits	117
Total	$ 117

Restructuring Costs - Schedule of Accrual Activity for Employee Termination Benefits (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($)
Restructuring And Related Activities [Abstract]
Balance at December 31, 2017	$ 0
Accruals	1,124
Payments	(1,124)
Balance at December 31, 2018	$ 0

Sale of Manufacturing Assets - Additional Information (Detail)		1 Months Ended	12 Months Ended
	Jul. 31, 2016 USD ($) ft²	Jul. 31, 2018 USD ($) ft²	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($) ft²	Dec. 31, 2016 USD ($) ft²
Sale Of Manufacturing Assets [Line Items]
Gain on the sale of assets		$ 2,300,000	$ 2,286,000	$ 0	$ 0
Gain related to deferred rent		1,100,000	$ 1,067,000	$ 0	$ 0
Lab and Office Space Occupied at No Cost [Member]
Sale Of Manufacturing Assets [Line Items]
Gain related to deferred rent		1,100,000
Genopis Inc [Member]
Sale Of Manufacturing Assets [Line Items]
Sale of idle manufacturing assets		$ 1,700,000
Genopis Inc [Member] \| Period Through December 31, 2018 [Member]
Sale Of Manufacturing Assets [Line Items]
Area of square feet agreed to sublease of facility \| ft²		51,400
Sublease expiration date		Dec. 31, 2018
Genopis Inc [Member] \| Period Ending December 31, 2019 [Member]
Sale Of Manufacturing Assets [Line Items]
Area of square feet agreed to sublease of facility \| ft²	0	17,000		0	0
Sublease expiration date		Dec. 31, 2019
Long-term lease beginning date		Jan. 01, 2019
Facility lease cost	$ 0	$ 0		$ 0	$ 0
Facility sublease expiration period		1 year

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2017	Dec. 31, 2015
Operating Loss Carryforwards [Line Items]
Cumulative change in ownership	More than 50% occurs within a three-year period.
Deferred tax assets	$ 87,389,000	$ 83,610,000
Percentage of cumulative change in ownership	50.00%
Valuation allowance	$ 87,389,000	83,610,000
Net operating loss generated	$ (19,646,000)	$ (13,386,000)	$ (9,177,000)
Operating loss carryforwards, percentage of offset available	80.00%
U.S. federal corporate tax rate	21.00%	35.00%
Tax cuts and jobs act of 2017, incomplete accounting, change in tax rate, provisional income tax expense (benefit)	$ 0	$ 34,439,000	0
Tax cuts and jobs act of 2017, incomplete accounting, change in tax rate, adjustment to provisional income tax expense (benefit)	0
Gross unrecognized tax benefits	19,500,000	17,836,000	17,561,000		$ 4,340,000
Accrual for interest or penalties	0	0
Interest or penalties expense	$ 0	0	$ 0
Tax year open to examination	1998
ASU 2016-09 [Member]
Operating Loss Carryforwards [Line Items]
Adoption of new accounting pronouncement of unrecognized excess tax benefits				$ (200,000)
Domestic Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	$ 94,600,000
Research and development credits and other tax credits	11,800,000
Net operating loss carryforwards	331,300,000	319,100,000
Net operating loss generated	18,800,000
Federal research and development credit and orphan drug credit carryforwards	$ 27,100,000	26,300,000
Domestic Tax Authority [Member] \| Earliest Tax Year [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards, expiration year	2019
Federal research and development credit and orphan drug credit carryforwards, expiration year	2019
Domestic Tax Authority [Member] \| Latest Tax Year [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards, expiration year	2038
Federal research and development credit and orphan drug credit carryforwards, expiration year	2038
State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	$ 264,600,000	254,900,000
Federal research and development credit and orphan drug credit carryforwards	$ 9,300,000	$ 8,800,000
State and Local Jurisdiction [Member] \| Earliest Tax Year [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards, expiration year	2028
State and Local Jurisdiction [Member] \| Latest Tax Year [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards, expiration year	2038

Income Taxes - Summary of Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Net operating losses	$ 63,933	$ 59,756
Credit carryovers	11,304	10,527
Depreciation and amortization	10,635	10,893
Deferred revenue	0	634
Accruals and reserves	275	450
Other	1,242	1,350
Total deferred tax assets	87,389	83,610
Less valuation allowance	(87,389)	(83,610)
Net deferred tax assets	$ 0	$ 0

Income Taxes - Reconciliation Between Provision for Income Taxes and Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Computed “expected” tax benefit	$ (3,421)	$ (4,425)	$ (3,051)
State income taxes, net of federal benefit	(676)	(268)	(534)
Tax effect of:
Change in valuation allowance	2,632	(31,665)	(6,030)
Impact of Tax Cuts and Jobs Act	0	34,439	0
Rate change	0	0	0
Expiration of prior year credits and net operating losses	1,386	1,256	692
Research and development and other tax credit carryovers	(1,320)	0	0
Stock compensation	121	458	491
Uncertain tax positions	1,357	276	9,010
Other	(79)	(71)	(578)
Provision for income taxes	$ 0	$ 0	$ 0

Income Taxes - Summary of Expected Expiry of Net Operating Losses and Tax Credits (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Federal [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	$ 331.3	$ 319.1
Tax credit carryforwards	27.1	26.3
Federal [Member] \| R&D Credit [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	5.2
Federal [Member] \| Orphan Drug Credits [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	21.9
State [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	264.6	254.9
Tax credit carryforwards	9.3	$ 8.8
State [Member] \| R&D Credit [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	9.3
2019 [Member] \| Federal [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	5.3
2019 [Member] \| Federal [Member] \| R&D Credit [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	0.4
2019 [Member] \| Federal [Member] \| Orphan Drug Credits [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	0.6
2019 [Member] \| State [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	0.0
2019 [Member] \| State [Member] \| R&D Credit [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	0.0
2020 [Member] \| Federal [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	12.3
2020 [Member] \| Federal [Member] \| R&D Credit [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	0.3
2020 [Member] \| Federal [Member] \| Orphan Drug Credits [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	2.3
2020 [Member] \| State [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	0.0
2020 [Member] \| State [Member] \| R&D Credit [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	0.0
2021 [Member] \| Federal [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	7.5
2021 [Member] \| Federal [Member] \| R&D Credit [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	0.3
2021 [Member] \| Federal [Member] \| Orphan Drug Credits [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	2.0
2021 [Member] \| State [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	0.0
2021 [Member] \| State [Member] \| R&D Credit [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	0.0
2022 [Member] \| Federal [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	22.4
2022 [Member] \| Federal [Member] \| R&D Credit [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	0.5
2022 [Member] \| Federal [Member] \| Orphan Drug Credits [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	1.6
2022 [Member] \| State [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	0.0
2022 [Member] \| State [Member] \| R&D Credit [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	0.0
2023 [Member] \| Federal [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	22.4
2023 [Member] \| Federal [Member] \| R&D Credit [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	0.3
2023 [Member] \| Federal [Member] \| Orphan Drug Credits [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	0.9
2023 [Member] \| State [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	0.0
2023 [Member] \| State [Member] \| R&D Credit [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	0.0
2024 and Thereafter [Member] \| Federal [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	242.6
2024 and Thereafter [Member] \| Federal [Member] \| R&D Credit [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	3.4
2024 and Thereafter [Member] \| Federal [Member] \| Orphan Drug Credits [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	14.5
2024 and Thereafter [Member] \| State [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	264.6
2024 and Thereafter [Member] \| State [Member] \| R&D Credit [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	0.0
Indefinite [Member] \| Federal [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	18.8
Indefinite [Member] \| Federal [Member] \| R&D Credit [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	0.0
Indefinite [Member] \| Federal [Member] \| Orphan Drug Credits [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	0.0
Indefinite [Member] \| State [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	0.0
Indefinite [Member] \| State [Member] \| R&D Credit [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	$ 9.3

Income Taxes - Summary of Activity Related to Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Beginning balance	$ 17,836	$ 17,561	$ 4,340
Increases (decreases) related to prior year tax positions	48	(140)	12,348
Increases related to current year tax positions	1,616	415	873
Ending balance	$ 19,500	$ 17,836	$ 17,561

Employee Benefit Plan - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Compensation And Retirement Disclosure [Abstract]
Company's contributions towards employee benefit plan	$ 0.1	$ 0.2	$ 0.1

Summary of (Unaudited) Quarterly Financial Information - Summary of Company's (Unaudited) Quarterly Results of Operations (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Total revenues	$ 124	$ 47	$ 735	$ 716	$ 3,953	$ 3,240	$ 3,421	$ 3,205	$ 1,622	$ 13,819	$ 14,531
Total operating expenses	4,075	4,113	5,863	7,217	7,834	6,421	6,832	6,118	21,268	27,205	23,708
Net income (loss)	$ (3,605)	$ (1,511)	$ (4,868)	$ (6,270)	$ (3,728)	$ (3,088)	$ (3,320)	$ (2,824)	$ (16,254)	$ (12,960)	$ (8,973)
Basic and diluted net loss per share	$ (0.17)	$ (0.07)	$ (0.22)	$ (0.29)	$ (0.21)	$ (0.27)	$ (0.30)	$ (0.25)	$ (0.74)	$ (1.01)	$ (0.90)

- Definition

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

+ References + Details