Cymabay Therapeutics (CBAY) 10-K 23 Mar 17 2016 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2016	Mar. 01, 2017	Jun. 30, 2016
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2016
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	FY
Trading Symbol	CBAY
Entity Registrant Name	CYMABAY THERAPEUTICS, INC.
Entity Central Index Key	1,042,074
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	Smaller Reporting Company
Entity Common Stock, Shares Outstanding		28,752,451
Entity Public Float			$ 37,357,482

Balance Sheets

Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 10,495	$ 7,706
Marketable securities	6,499	33,774
Prepaid expenses	1,369	608
Other current assets	165	186
Total current assets	18,528	42,274
Property and equipment, net	77	64
Other assets	754	741
Total assets	19,359	43,079
Current liabilities:
Accounts payable	899	1,008
Accrued liabilities	4,501	3,336
Warrant liability	1,145	1,220
Facility loan	2,700	509
Accrued interest payable	66	73
Total current liabilities	9,311	6,146
Facility loan, less current portion	6,098	8,799
Other liabilities	13	19
Total liabilities	15,422	14,964
Commitments and contingencies
Stockholders' equity:
Preferred stock, $0.0001 par value: 10,000,000 shares authorized; no shares issued and outstanding
Common stock, $0.0001 par value: 100,000,000 shares authorized; 23,447,003 and 23,447,003 shares issued and outstanding as of December 31, 2016 and December 31, 2015, respectively	2	2
Additional paid-in capital	426,895	424,422
Accumulated other comprehensive loss	(1)	(21)
Accumulated deficit	(422,959)	(396,288)
Total stockholders' equity	3,937	28,115
Total liabilities and stockholders' equity	$ 19,359	$ 43,079

Balance Sheets (Parenthetical)

Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	23,447,003	23,447,003
Common stock, shares outstanding	23,447,003	23,447,003

Statements of Operations and Co

Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Operating expenses:
Research and development	$ 15,941	$ 17,026
General and administrative	9,645	8,871
Total operating expenses	25,586	25,897
Loss from operations	(25,586)	(25,897)
Other income (expense):
Interest income	176	160
Interest expense	(1,337)	(913)
Other income, net	76	11,121
Net loss	(26,671)	(15,529)
Net loss	(26,671)	(15,529)
Other comprehensive income (loss):
Unrealized gain (loss) on marketable securities	20	(7)
Other comprehensive income (loss)	20	(7)
Comprehensive loss	$ (26,651)	$ (15,536)
Basic net loss per common share	$ (1.14)	$ (0.82)
Diluted net loss per common share	$ (1.14)	$ (0.83)
Weighted average common shares outstanding used to calculate basic net loss per common share	23,447,003	18,900,473
Weighted average common shares outstanding used to calculate diluted net loss per common share	23,447,003	18,917,213

Statement of Shareholders' Equi

Statement of Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Deficit [Member]
Balance at beginning of period at Dec. 31, 2014	$ 13,850	$ 1	$ 394,622	$ (14)	$ (380,759)
Balance at beginning of period (in shares) at Dec. 31, 2014		14,696,108
Issuance of common stock upon exercise of warrants, value	1,939		1,939
Issuance of common stock upon exercise of warrants (Shares)		132,295
Stock-based compensation expense	2,487		2,487
Issuance of common stock, value	25,375	$ 1	25,374
Issuance of common stock, (in shares)		8,618,600
Net loss	(15,529)				(15,529)
Net unrealized gain (loss) on marketable securities	(7)			(7)
Balance at end of period at Dec. 31, 2015	28,115	$ 2	424,422	(21)	(396,288)
Balance at end of period (in shares) at Dec. 31, 2015		23,447,003
Stock-based compensation expense	2,473		2,473
Net loss	(26,671)				(26,671)
Net unrealized gain (loss) on marketable securities	20			20
Balance at end of period at Dec. 31, 2016	$ 3,937	$ 2	$ 426,895	$ (1)	$ (422,959)
Balance at end of period (in shares) at Dec. 31, 2016		23,447,003

Statement of Shareholders' Equ6

Statement of Shareholders' Equity (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2015USD ($)
Statement of Stockholders' Equity [Abstract]
Stock issuance cost	$ 2,028

Statements of Cash Flows

Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Operating activities
Net loss	$ (26,671)	$ (15,529)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	29	22
Stock-based compensation expense	2,473	2,487
Amortization of premium on marketable securities	125	511
Non-cash interest associated with debt discount accretion	476	228
Change in fair value of warrant liability	(75)	(11,121)
Changes in assets and liabilities:
Other current assets	165	161
Prepaid expenses	(761)	1,383
Other assets	(13)	(486)
Accounts payable	(109)	(1,077)
Accrued liabilities	1,015	(46)
Accrued interest payable	(7)	143
Net cash used in operating activities	(23,353)	(23,324)
Investing activities
Purchases of property and equipment	(42)
Purchases of marketable securities	(22,906)	(42,788)
Proceeds from maturities of marketable securities	50,076	31,705
Net cash provided by (used in) investing activities	27,128	(11,083)
Financing activities
Proceeds from facility loan		9,482
Repayment of facility loan principal	(986)	(4,756)
Proceeds from issuance of common stock and warrants, net of issuance costs		25,375
Proceeds from issuance of common stock upon exercise of warrants		426
Net cash (used in) provided by financing activities	(986)	30,527
Net increase (decrease) in cash and cash equivalents	2,789	(3,880)
Cash and cash equivalents at beginning of period	7,706	11,586
Cash and cash equivalents at end of period	10,495	7,706
Supplemental disclosure
Cash paid for interest	866	535
Supplemental non-cash investing and financing activities
Issuance of common stock warrants to lenders		258
Issuance of common stock upon warrant exercises		$ 1,513
Net change in accrued financing costs	$ 144

Organization and Description of

Organization and Description of Business	12 Months Ended
	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Description of Business	1. Organization and Description of Business CymaBay Therapeutics, Inc. (the “Company” or “CymaBay”) is a biopharmaceutical company focused on developing therapies to treat specialty and orphan diseases with high unmet medical need. The Company’s two key clinical development candidates are seladelpar (MBX-8025) and arhalofenate. Seladelpar is currently being developed primarily for the treatment of primary biliary cholangitis (PBC). Arhalofenate is being developed for the treatment of gout and has been outliscensed in the United States. The Company was incorporated in Delaware in October 1988 as Transtech Corporation. The Company’s headquarters and operations are located in Newark, California and it operates in one segment. The Company is an “emerging growth company,” as defined in the Jumpstart Our Business Startups Act of 2012, or the JOBS Act. Under the JOBS Act, emerging growth companies can delay adopting new or revised accounting standards issued subsequent to the enactment of the JOBS Act until such time as those standards apply to private companies. The Company has irrevocably elected not to avail itself of this exemption from new or revised accounting standards, and, therefore, is subject to the same new or revised accounting standards as other public companies that are not emerging growth companies. Liquidity The Company has incurred net operating losses and negative cash flows from operations since its inception. During the year ended December 31, 2016, the Company incurred a net loss of $26.7 million and used $23.4 million of cash in operations. At December 31, 2016, the Company had an accumulated deficit of $423.0 million. CymaBay expects to incur substantial research and development expenses as it continues to study its product candidates in clinical trials. To date, none of the Company’s product candidates have been approved for marketing and sale, and the Company has not recorded any revenue from product sales. As a result, management expects operating losses to continue in future years. The Company’s ability to achieve profitability is dependent primarily on its ability to successfully develop, acquire or in-license additional product candidates, continue clinical trials for product candidates currently in clinical development, obtain regulatory approvals, and support commercialization activities for partnered product candidates. Products developed by the Company will require approval of the U.S. Food and Drug Administration (FDA) or a foreign regulatory authority prior to commercial sale. The regulatory approval process is expensive, time-consuming, and uncertain, and any denial or delay of approval could have a material adverse effect on the Company. Even if approved, the Company’s products may not achieve market acceptance and will face competition from both generic and branded pharmaceutical products. As of December 31, 2016, the Company’s cash, cash equivalents and marketable securities totaled $17.0 million. These funds, together with $9.4 million received from financings and $5.0 million received from a license arrangement in January and February 2017, are expected to satisfy the Company’s liquidity requirements through at least the next 12 months. The Company expects to incur substantial expenditures in the future for the development and potential commercialization of its product candidates. Because of this, the Company expects its future liquidity and capital resource needs will be impacted by numerous factors, including but not limited to, the repayment of the Company’s facility loan, the timing of initiation of planned clinical trials, including phase 2 trials to study the therapeutic benefits of seladelpar on patients with certain orphan diseases. The Company has and expects to obtain additional funding to develop its products and fund future operating losses through equity offerings, debt financing, one or more possible licenses, collaborations or other similar arrangements with respect to development and/or commercialization rights of its product candidates, or a combination of the above. It is unclear if or when any such transactions will occur, on satisfactory terms or at all. The Company’s failure to raise capital as and when needed could have a negative impact on its financial condition and its ability to pursue its business strategies. If adequate funds are not available, the Company may be required to reduce current development activities or limit or cease operations.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2016
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation and Use of Estimates The accompanying financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (U.S. GAAP), which requires management to make informed estimates and assumptions that impact the amounts and disclosures reported in the financial statements and accompanying notes. Accounting estimates and assumptions are inherently uncertain. Management bases its estimates on historical experience and on assumptions believed to be reasonable under the circumstances. The estimation process often may yield a range of potentially reasonable estimates of the ultimate future outcomes, and management must select an amount that falls within that range of reasonable estimates. Actual results could differ materially from those estimates and assumptions. The Company believes significant judgment is involved in determining and in estimating the valuation of stock-based compensation, accrued clinical expenses, and equity instrument valuations. These estimates form the basis for making judgments about the carrying values of assets and liabilities when these values are not readily apparent from other sources. Estimates are assessed each reporting period and updated to reflect current information and any changes in estimates will generally be reflected in the period first identified. Reclassifications Accrued interest receivable as of December 31, 2015 which was previously presented separately has been combined with other current assets in the accompanying balance sheets to conform to the December 31, 2016 presentation. Additionally, the Company has reclassified retainer fees paid to a vendor from prepaid expenses to other assets in the accompanying balance sheet as of December 31, 2015 to conform to the December 31, 2016 presentation. Fair Value of Financial Instruments The Company’s financial instruments during the periods reported consist of cash and cash equivalents, marketable securities, prepaid expenses, other current assets, accounts payable, accrued interest payable, accrued expenses, the Facility Loan, and warrant liabilities. Fair value estimates of these instruments are made at a specific point in time, based on relevant market information. These estimates may be subjective in nature and involve uncertainties and matters of significant judgment. The carrying amounts of financial instruments such as cash and cash equivalents, prepaid expenses, other current assets, accounts payable, accrued expenses, and accrued interest payable approximate the related fair values due to the short maturities of these instruments. Based on prevailing borrowing rates available to the Company for loans with similar terms, the Company believes the fair value of the Facility Loan, considering level 2 inputs, approximates its carrying value. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants at the measurement date. Assets and liabilities that are measured at fair value are reported using a three-level fair value hierarchy that prioritizes the inputs used to measure fair value. This hierarchy maximizes the use of observable inputs and maximizes the use of unobservable inputs and is as follows: Level 1—Quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date. Level 2—Inputs other than quoted prices in active markets that are observable for the asset or liability, either directly or indirectly. Level 3—Inputs that are significant to the fair value measurement and are unobservable (i.e. supported by little market activity), which requires the reporting entity to develop its own valuation techniques and assumptions. The following tables present the fair value of the Company’s financial assets and liabilities measured at fair value on a recurring basis using the above input categories (in thousands): (In thousands) As of December 31, 2016 Description Level 1 Level 2 Level 3 Fair Value Cash equivalents: Money market funds $ 9,456 $ — $ — $ 9,456 Commercial paper — 599 — 599 Corporate debt securities — 500 — 500 Total cash equivalents 9,456 1,099 — 10,555 Short-term investments: Commercial paper — 4,295 — 4,295 Corporate debt securities — 2,204 — 2,204 Total short-term investments — 6,499 — 6,499 Total assets measured at fair value $ 9,456 $ 7,598 $ — $ 17,054 Warrant liability $ — $ — $ 1,145 $ 1,145 Total liabilities measured at fair value $ — $ — $ 1,145 $ 1,145 (In thousands) As of December 31, 2015 Description Level 1 Level 2 Level 3 Fair Value Cash equivalents: Money market funds $ 6,942 $ — $ — $ 6,942 Total cash equivalents $ 6,942 $ — $ — $ 6,942 Short-term investments: Commercial paper — 5,992 — 5,992 Government debt securities — 1,507 — 1,507 Corporate debt securities — 21,654 — 21,654 Asset-backed securities — 4,621 — 4,621 Total short-term investments — 33,774 — 33,774 Total assets measured at fair value $ 6,942 $ 33,774 $ — $ 40,716 Warrant liability $ — $ — $ 1,220 $ 1,220 Total liabilities measured at fair value $ — $ — $ 1,220 $ 1,220 The Company estimates the fair value of its money market funds, commercial paper, corporate debt, asset backed securities, and government debt securities by taking into consideration valuations obtained from third-party pricing services. The pricing services utilize industry standard valuation models, including both income and market-based approaches, for which all significant inputs are observable, either directly or indirectly, to estimate fair value. These inputs include reported trades of and broker/dealer quotes on the same or similar securities, issuer credit spreads; benchmark securities; prepayment/default projections based on historical data; and other observable inputs. There were no transfers between Level 1 and Level 2 during the periods presented. As of December 31, 2016 and 2015, financial instruments measured using Level 3 inputs consisted of the Company’s warrants which are accounted for as liabilities. The warrants are valued using a binomial lattice option-pricing model, the significant inputs for which include exercise price of the warrants, market price of the underlying common shares, expected term, expected volatility, the risk-free rate, key strategic initiatives, probability of success related to those initiatives, and the expected changes in stock price that follow announcements of the Company’s strategic initiatives. Changes to any of the inputs to the option-pricing models used by the Company can have a significant impact to the estimated fair value of the warrants. The following tables set forth a summary of the changes in the fair value of our liabilities measured using Level 3 inputs (in thousands): For the Twelve 2016 2015 Balance, beginning of period $ 1,220 $ 13,596 Issuance of financial instrument — 258 Change in fair value (75 ) (11,121 ) Settlement of financial instrument — (1,513 ) Balance, end of period $ 1,145 $ 1,220 Cash, Cash Equivalents, and Marketable Securities The Company considers all highly liquid investments with a remaining maturity of 90 days or less at the time of purchase to be cash equivalents. Cash and cash equivalents consist of deposits with commercial banks in checking, interest-bearing, and demand money market accounts. The Company invests excess cash in marketable securities with high credit ratings which are classified in Level 1 and Level 2 of the fair value hierarchy. These securities consist primarily of corporate debt, commercial paper, and asset-backed securities and are classified as “available-for-sale.” Management may liquidate any of these investments in order to meet the Company’s liquidity needs in the next year. Accordingly, any investments with contractual maturities greater than one year from the balance sheet date are classified as short-term in the accompanying balance sheets. Realized gains and losses from the sale of marketable securities, if any, are calculated using the specific-identification method. Realized gains and losses and declines in value judged to be other-than- temporary are included in interest income or expense in the statements of operations and comprehensive loss. Unrealized holding gains and losses are reported in accumulated other comprehensive loss in the balance sheets. To date, the Company has not recorded any impairment charges on its marketable securities related to other-than-temporary declines in market value. In determining whether a decline in market value is other-than-temporary, various factors are considered, including the cause, duration of time and severity of the impairment, any adverse changes in the investees’ financial condition, and the Company’s intent and ability to hold the security for a period of time sufficient to allow for an anticipated recovery in market value. Restricted Cash The Company is required to maintain compensating cash balances with financial institutions that provide the Company with its corporate credit cards. As of December 31, 2016 and 2015, cash restricted under these arrangements was $170,000. These amounts are presented in other assets on the accompanying balance sheets. Concentration of Credit Risk Cash, cash equivalents, and marketable securities consist of financial instruments that potentially subject the Company to a concentration of credit risk to the extent of the fair value recorded in the balance sheet. The Company invests cash that is not required for immediate operating needs primarily in highly liquid instruments that bear minimal risk. The Company has established guidelines relating to the quality, diversification, and maturities of securities to enable the Company to manage its credit risk. We are exposed to credit risk in the event of a default by the financial institutions holding our cash, cash equivalents and investments and issuers of investments to the extent recorded on the balance sheets. Certain materials and key components that the Company utilizes in its operations are obtained through single suppliers. Since the suppliers of key components and materials must be named in a new drug application (NDA) filed with the U.S. Food and Drug Administration (FDA) for a product, significant delays can occur if the qualification of a new supplier is required. If delivery of material from the Company’s suppliers were interrupted for any reason, the Company may be unable to supply any of its product candidates for clinical trials. Property and Equipment Property and equipment is recorded at cost, less accumulated depreciation and amortization. Depreciation and amortization is calculated using the straight-line method, and the cost is amortized over the estimated useful lives of the respective assets, generally three to seven years. Leasehold improvements are amortized over the shorter of the useful lives or the non-cancelable term of the related lease. Maintenance and repair costs are charged as expense in the statements of operations and comprehensive loss as incurred. Impairment of Long-Lived Assets The Company reviews long-lived assets for impairment whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. An impairment loss is recognized if the estimated undiscounted future cash flow expected to result from the use and eventual disposition of an asset is less than the carrying amount. While the Company’s current and historical operating losses and cash flows are indicators of impairment, the Company believes the future cash flows to be received support the carrying value of its long-lived assets. Accordingly, the Company has not recognized any impairment losses as of December 31, 2016. Deferred Rent The Company records its costs under facility operating lease agreements as rent expense. Rent expense is recognized on a straight-line basis over the non-cancelable term of the operating lease. The difference between the actual amounts paid and amounts recorded as rent expense is recorded as deferred rent in the accompanying balance sheets. Revenue Recognition The Company recognizes revenue when (i) persuasive evidence of an arrangement exists, (ii) delivery has occurred or services have been rendered, (iii) the price is fixed or determinable, and (iv) collectability is reasonably assured. Payments received in advance of work performed are recorded as deferred revenue and recognized when earned. Collaboration and license agreements may include non-refundable If the Company determines that multiple deliverables in an arrangement exist, the consideration is allocated to one or more units of accounting based upon the relative-selling-price The Company recognizes payments that are contingent upon achievement of a substantive milestone in their entirety in the period in which the milestone is achieved. Milestones are defined as events that can only be achieved based on the Company’s performance and there is substantive uncertainty about whether the event will be achieved at the inception of the arrangement. Events that are contingent only on the passage of time or only on counterparty performance are not considered milestones subject to this guidance. Further, the amounts received must relate solely to prior performance, be reasonable relative to all of the deliverables and payment terms within the agreement and commensurate with the Company’s performance to achieve the milestone after commencement of the agreement. Any contingent payment that becomes payable upon achievement of events that are not considered substantive milestones are allocated to the units of accounting previously identified at the inception of an arrangement when the contingent payment is received and revenue is recognized based on the revenue recognition criteria for each unit of accounting. Research and Development Expenses Research and development expenses consist of costs incurred in identifying, developing, and testing product candidates. These expenses consist primarily of costs for research and development personnel, including related stock-based compensation; contract research organizations (CRO) and other third parties that assist in managing, monitoring, and analyzing clinical trials; investigator and site fees; laboratory services; consultants; contract manufacturing services; non-clinical studies, including materials; and allocated expenses, such as depreciation of assets, and facilities and information technology that support research and development activities. Research and development costs are expensed as incurred, including expenses that may or may not be reimbursed under research and development funding arrangements. Payments made prior to the receipt of goods or services to be used in research and development are recorded as prepaid assets until the goods are received or services are rendered. Such payments are evaluated for current or long term classification based on when they will be realized. The Company records expenses related to clinical studies and manufacturing development activities based on its estimates of the services received and efforts expended pursuant to contracts with multiple CROs and manufacturing vendors that conduct and manage these activities on its behalf. The financial terms of these agreements are subject to negotiation, vary from contract to contract, and may result in uneven payment flows. There may be instances in which payments made to the Company’s vendors will exceed the level of services provided and result in a prepayment of the expense. Payments under some of these contracts depend on factors such as the successful enrollment of subjects and the completion of clinical trial milestones. In amortizing or accruing service fees, the Company estimates the time period over which services will be performed, enrollment of subjects, number of sites activated and the level of effort to be expended in each period. If the actual timing of the performance of services or the level of effort varies from the Company’s estimate, the Company will adjust the accrued or prepaid expense balance accordingly. To date, there have been no material differences from the Company’s estimates to the amounts actually incurred. Stock-Based Compensation Employee and director stock-based compensation is measured at fair value on the grant date of the award. Compensation cost is recognized as expense on a straight-line basis over the vesting period for options and on an accelerated basis for stock options with performance conditions, net of estimated forfeitures. For stock options with performance conditions, the Company evaluates the probability of achieving performance conditions at each reporting date. The Company begins to recognize the expense when it is deemed probable that the performance conditions will be met. The Company uses the Black-Scholes option pricing model to determine the fair value of stock option awards. The determination of fair value for stock-based awards using an option-pricing model requires management to make certain assumptions regarding subjective input variables such as expected term, dividends, volatility and forfeiture rates. The Company is also required to make estimates as to the probability of achieving the specific performance criteria. If actual results are not consistent with the Company’s assumptions and judgments used in making these estimates, the Company may be required to increase or decrease compensation expense, which could be material to the Company’s results of operations. Equity awards granted to non-employees are valued using the Black-Scholes option pricing model. Stock-based compensation expense for nonemployee services is subject to remeasurement as the underlying equity instruments vest and is recognized as an expense over the period during which services are received. Common Stock Warrant Liabilities The Company’s outstanding common stock warrants issued in connection with certain equity and debt financings that occurred in 2013 through 2015 are classified as liabilities in the accompanying balance sheets because of certain contractual terms that preclude equity classification. The warrants are recorded at fair value using a binomial lattice option-pricing model. The warrants are re-measured at each financial reporting period until the warrants are exercised or expire, with any changes in fair value being recognized as a component of other income (expense), net in the accompanying condensed statements of operations and comprehensive loss. Income Taxes The Company utilizes the liability method of accounting for income taxes. Under this method, deferred tax assets and liabilities are determined based on differences between the financial reporting and the tax bases of assets and liabilities and are measured using enacted tax rates and laws that will be in effect when the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date. A valuation allowance is recorded when it is more likely than not that all or part of a deferred tax asset will not be realized. When the Company establishes or reduces the valuation allowance related to the deferred tax assets, the provision for income taxes will increase or decrease, respectively, in the period such determination is made. The accounting guidance for uncertainty in income taxes prescribes a recognition threshold and measurement attribute criteria for the financial recognition and measurement of tax positions taken or expected to be taken in a tax return. For those benefits to be recognized, a tax position must be more likely than not to be sustained upon examination based on the technical merits of the position. The Company is required to file federal and state income tax returns in the United States. The preparation of these income tax returns requires the Company to interpret the applicable tax laws and regulations in effect which could affect the amount of tax paid to these jurisdictions. The Company records interest related to income tax reserves, if any, as interest expense, and any penalties would be recorded as other expense in the statements of operations and comprehensive loss. There was no interest or penalties related to income tax reserves during the years ended December 31, 2016 and 2015. Comprehensive Loss Comprehensive loss includes net loss and net unrealized gains and losses on marketable securities, which are presented in a single continuous statement. Comprehensive loss is disclosed in the statements of stockholders’ equity, and is stated net of related tax effects, if any. Net Income (Loss) Per Common Share Basic net loss per share of common stock is based on the weighted average number of shares of common stock outstanding equivalents during the period. Diluted net loss per share of common stock is calculated as the weighted average number of shares of common stock outstanding adjusted to include the assumed exercises of stock options and common stock warrants, if dilutive. The calculation of diluted loss per share also requires that, to the extent the average market price of the underlying shares for the reporting period exceeds the exercise price of the common stock warrants and the presumed exercise of such securities are dilutive to earnings (loss) per share for the period, adjustments to net income or net loss used in the calculation are required to remove the change in fair value of the common stock warrant liability for the period. Likewise, adjustments to the denominator are required to reflect the related dilutive shares. In all periods presented, the Company’s outstanding stock options were excluded from the calculation of net loss per share because the effect would be antidilutive. The following table sets forth the computation of basic and diluted net loss per share (in thousands, except share and per share amounts): Year Ended December 31, 2016 2015 Numerator: Net loss allocated to common stock—basic $ (26,671 ) $ (15,529 ) Adjustment for revaluation of warrants — (94 ) Net loss allocated to common stock—diluted $ (26,671 ) $ (15,623 ) Denominator: Weighted average number of common stock shares outstanding—basic 23,447,003 18,900,473 Dilutive common stock warrants — 16,740 Weighted average number of common stock shares outstanding—diluted 23,447,003 18,917,213 Net loss per share—basic $ (1.14 ) $ (0.82 ) Net loss per share—diluted $ (1.14 ) $ (0.83 ) The following table shows the total outstanding securities considered anti-dilutive and therefore excluded from the computation of diluted net loss per share (in thousands): Year Ended 2016 2015 Common stock warrants 1,667 1,553 Common stock options 2,394 1,804 Performance-based stock options 327 — Incentive awards 239 245 4,627 3,602 Recent Accounting Pronouncements Accounting Standards Update 2014-09 In May 2014, the FASB issued Accounting Standards Update 2014-09, Revenue from Contracts with Customers and related amendments. Subsequently, the Financial Accounting Standards Board (the FASB) issued the following standards related to ASU 2014-09: ASU No. 2016-08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations; ASU No. 2016-10, Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing; and ASU No. 2016-12, Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients. This guidance outlines a new, and single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes nearly all of the existing revenue recognition guidance, including industry-specific guidance. This new revenue recognition model provides a five-step analysis in determining when and how revenue is recognized. The new model will require revenue recognition to depict the transfer of promised goods or services to customers in an amount that reflects the consideration a company expects to receive in exchange for those goods or services. The new revenue standard permits two methods of adoption: retrospectively to each prior reporting period presented (full retrospective method), or retrospectively with the cumulative effect of initially applying the guidance recognized at the date of initial application (the modified retrospective method). The Company plans to adopt the new revenue standard in the first quarter of 2018 using the modified retrospective method. While the Company has not completed an assessment of the impact of adoption, the adoption of this guidance may have a material effect on the Company’s financial statements. At the end of 2016, the Company entered into a license agreement. Before executing this agreement, the Company has had no revenues for the last two years. The consideration the Company is eligible to receive under this agreement includes an upfront payment, milestone payments, and royalties. This license agreement is unique and will need to be assessed separately under the five-step process under the new standard. The Company is currently in the early stages of analyzing this agreement to determine the differences in the accounting treatment under the new revenue standard compared to the current accounting treatment. The new revenue standard differs from the current accounting standard in many respects, such as in the accounting for variable consideration, including milestone payments and royalties. Accounting Standards Update 2014-15 In August 2014, the FASB issued guidance codified in ASC 205, Presentation of Financial Statements — Going Concern. Accounting Standards Update 2014-15 requires an entity’s management to evaluate whether there are conditions or events, considered in the aggregate, that raise substantial doubt about the entity’s ability to continue as a going concern and if those conditions exist, to make the required disclosures. The ASU aligns the interpretation of substantial doubt with the definition of “probable” pursuant to ASC 450, Contingencies Accounting Standards Update 2015-03 In April 2015, the FASB issued ASU No. 2015-03, Interest—Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issuance Costs, which requires debt issuance costs related to a recognized debt liability to be presented in the balance sheet as a direct deduction from the corresponding debt liability rather than as an asset. The Company adopted this ASU with retrospective application in the first quarter of 2016. As the Company does not have any debt issuance costs recorded as assets, the adoption of this standard did not have any impact on the Company’s financial statements. Accounting Standards Update 2016-02 In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842). The new standard requires the recognition of assets and liabilities arising from lease transactions on the balance sheet and the disclosure of key information about leasing arrangements. Accordingly, a lessee will recognize a lease asset for its right to use the underlying asset and a lease liability for the corresponding lease obligation. Both the asset and liability will initially be measured at the present value of the future minimum lease payments over the lease term. Subsequent measurement, including the presentation of expenses and cash flows, will depend on the classification of the lease as either a finance or an operating lease. Initial costs directly attributable to negotiating and arranging the lease will be included in the asset. Lessees will also be required to provide additional qualitative and quantitative disclosures regarding the amount, timing and uncertainty of cash flows arising from leases. The new standard is effective for fiscal years beginning after December 15, 2018, and interim periods therein. Early adoption is permitted. The Company is currently evaluating the impact this guidance will have on its financial statements. Accounting Standards Update 2016-09 In March 2016, the FASB issued ASU No. 2016-09, Improvements to Employee Share-Based Payment Accounting, which amends ASC Topic 718, Compensation – Stock Compensation. This guidance simplifies the accounting for the taxes related to stock based compensation, requiring excess tax benefits and deficiencies to be recognized as a component of income tax expense rather than equity. This guidance also requires excess tax benefits and deficiencies to be presented as an operating activity on the statement of cash flows and allows an entity to make an accounting policy election to either estimate expected forfeitures or to account for them as they occur. The amendments in this ASU are effective for annual periods beginning after December 15, 2016 and for the interim periods therein. Early adoption is permitted. The Company is currently evaluating the impact this guidance will have on its financial statements.

Marketable Securities

Marketable Securities	12 Months Ended
	Dec. 31, 2016
Cash and Cash Equivalents [Abstract]
Marketable Securities	3. Marketable Securities Marketable available-for-sale securities as of December 31, 2016 and 2015 consist of the following (in thousands): Amortized Gross Gross Estimated As of December 31, 2016: Short-term investments: Commercial paper $ 4,295 $ — $ — $ 4,295 Corporate debt securities 2,205 — (1 ) 2,204 $ 6,500 $ — $ (1 ) $ 6,499 Amortized Gross Gross Estimated As of December 31, 2015: Short-term investments: Commercial paper $ 5,992 $ — $ — $ 5,992 Government debt securities 1,509 — (2 ) 1,507 Corporate debt securities 21,671 — (17 ) 21,654 Asset-backed securities 4,623 — (2 ) 4,621 $ 33,795 $ — $ (21 ) $ 33,774 As of December 31, 2016 and 2015, the remaining contractual maturities of the Company’s commercial paper, corporate debt securities, and government debt securities were between 1-2 years and asset-backed securities had contractual maturities between 2-5 years. Realized gains and losses were immaterial for the years ended December 31, 2016 and 2015. None of these investments have been in a continuous unrealized loss position for more than 12 months as of December 31, 2016 and 2015.

Certain Balance Sheet Items

Certain Balance Sheet Items	12 Months Ended
	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Certain Balance Sheet Items	4. Certain Balance Sheet Items Property and equipment consist of the following (in thousands): December 31, December 31, Office and computer equipment $ 177 $ 176 Purchased software 83 46 Furniture and fixtures 38 33 Leasehold improvements 65 66 Total 363 321 Less accumulated depreciation and amortization (286 ) (257 ) Property and equipment, net $ 77 $ 64 Accrued liabilities consist of the following (in thousands): December 31, December 31, Accrued compensation $ 1,839 $ 1,010 Accrued pre-clinical and clinical trial expenses 1,623 2,015 Accrued professional fees 982 283 Other accruals 57 28 Total accrued liabilities $ 4,501 $ 3,336

Collaboration and License Agree

Collaboration and License Agreements	12 Months Ended
	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Collaboration and License Agreements	5. Collaboration and License Agreements Kowa Pharmaceuticals America, Inc. On December 30, 2016, the Company entered into a license agreement with Kowa Pharmaceuticals America, Inc. (“Kowa”). Pursuant to the license agreement, the Company granted to Kowa an exclusive license, and right to sublicense, certain patent rights and technology related to arhalofenate. Kowa will have exclusive rights to, among other things, develop, use, manufacture, sell and otherwise exploit the licensed technology in the United States (including all possessions and territories). At Kowa’s option, the Company may also facilitate the placement of arhalofenate product manufacturing orders under the terms of the Company’s existing contract manufacturing agreements. In addition, the Company will complete specified in-process stability testing and non-clinical development services and will participate on a Joint Advisory Committee (“JAC”). Finally, the Company will transfer to Kowa certain arhalofenate product on hand. Under the license agreement, Kowa agreed to pay the Company a non-refundable up-front payment of $5 million upon contract execution which was subsequently received in mid-January 2017. The Company is also eligible to receive up to $200 million in contingent payments based upon either the initiation or achievement of specified development and sales milestones. Finally, the Company will receive tiered, double digit royalties on any product sales and a percentage of any revenue earned by Kowa from sublicensing. The Company identified the following three performance deliverables under the license agreement: 1) transfer of intellectual property rights, inclusive of the related technology know-how know-how”), know-how The Company considered the provisions of the multiple-element As of December 31, 2016, no revenue had been recognized as the up-front payment had not yet been received and delivery had not yet occurred for the license and know-how, The Company determined the future contingent payments related to the development activities do not meet the definition of a milestone. Under current revenue recognition rules, these amounts will be allocated to the Kowa arrangements’ three identified units of accounting when received and recognized as revenue based on the revenue recognition policy for those respective units of accounting. The future contingent payments related to the U.S. sales milestones are recognized upon achievement of the specific milestones. As of December 31, 2016, none of these contingent amounts had been received or recognized as revenue. Janssen Pharmaceutical NV and Janssen Pharmaceuticals, Inc. In June 2006, the Company entered into an exclusive worldwide, royalty-bearing license to seladelpar and certain other PPAR d d d d d d d d In June 2010, the Company entered into two development and license agreements with Janssen Pharmaceuticals, Inc. (Janssen), a subsidiary of Johnson and Johnson, to further develop and discover undisclosed metabolic disease target agonists for the treatment of T2DM and other disorders and received a one-time nonrefundable technology access fee related to the agreements. The Company received a termination notice from Janssen, effectively ending these development and licensing agreements in early April 2015. In December 2015, the Company exercised an option pursuant to the terms of one of the original agreements to continue work to research, develop and commercialize compounds with activity against an undisclosed metabolic disease target. Janssen granted the Company an exclusive, worldwide license (with rights to sublicense) under the Janssen know-how and patents to research, develop, make, have made, use, offer for sale and sell such compounds. The Company has full control and responsibility over the research, development and registration of any products developed and/or discovered from the metabolic disease target and is required to use diligent efforts to conduct all such activities. DiaTex, Inc. In June 1998, the Company entered into a license agreement with DiaTex, Inc. (DiaTex) relating to products containing halofenate, its enantiomers, derivatives, and analogs (the licensed products). The license agreement provides that DiaTex and the Company are joint owners of all of the patents and patent applications covering the licensed products and methods of producing or using such compounds, as well as certain other know-how (the covered IP). As part of the license agreement, the Company received an exclusive worldwide license, including as to DiaTex, to use the covered IP to develop and commercialize the licensed products. The Company also retained the right to sub-license the covered IP. The license agreement contains a $2,000 per month license fee as well as a requirement to make additional payments for development achievements and royalty payments on any sales of licensed products. DiaTex is entitled to up to $0.8 million for the future development of arhalofenate, as well as royalty payments on commercial sales of products containing arhalofenate. No development payments were made or due as of and for the years ended December 31, 2016 and 2015 and no royalties have been paid to date. In December 2016, the agreement was amended by the parties to change the timing of a specified development milestone.

Facility Loans

Facility Loans	12 Months Ended
	Dec. 31, 2016
Debt Disclosure [Abstract]
Facility Loans	6. Facility Loans 2013 Term Loan Facility On September 30, 2013, the Company entered into a facility loan agreement with Silicon Valley Bank and Oxford Finance LLC (referred to herein as the lenders) for a total loan amount of $10.0 million of which the first tranche of $5.0 million was drawn as part of the Company’s September 2013 financing, referred to here as the 2013 Term Loan Facility. The loan had a fixed interest rate of 8.75% payable as interest only for twelve months and a thirty-six month loan amortization period thereafter, with a final interest payment of $0.3 million at the end of the loan period. The second tranche of $5.0 million became available to the Company upon its February 24, 2015 announcement of the achievement of positive Phase 2b data for the Company’s product candidate arhalofenate and remained available to the Company until June 30, 2015. On June 30, 2015, the second tranche portion of the loan facility expired unused by the Company. At the time the first $5 million tranche of the facility loan was drawn down, the Company issued warrants exercisable for a total of 121,739 shares of the Company’s common stock to the lenders at an exercise price of $5.00 per share. Upon issuance, the fair value of a warrant liability was recorded and is being revalued at each balance sheet date until the warrants are exercised or expire. 2015 Term Loan Facility On August 7, 2015, the Company entered into a Loan and Security Agreement pursuant to which it refinanced its existing 2013 Term Loan Facility with Oxford Finance LLC and Silicon Valley Bank, for an aggregate amount of up to $15 million, referred to here as the 2015 Term Loan Facility. The first $10 million tranche of this new loan facility was made available to the Company immediately upon the closing and was used in part to retire all $4.1 million of the Company’s existing debt outstanding under the 2013 Term Loan Facility, and to settle accrued interest and closing costs with the lenders. The remaining $5 million, referred to as the second tranche, was made available to the Company until March 31, 2016, for draw down upon the announcement of a qualified out-license or co-development arrangement for arhalofenate, the Company’s gout therapy drug candidate, which includes an upfront payment of not less than $35.0 million (the “second draw milestone”). Because the present value of the future cash flows under the modified loan terms did not exceed the present value of the future cash flows under the previous loan terms by more than 10%, the Company treated this refinancing as a modification. The remaining debt discount costs will be amortized over the remaining term of the Loan and Security Agreement using the effective interest rate method. The $5.0 million second tranche expired unused in March 2016 as the second draw milestone was not achieved. The first loan tranche bears interest at 8.77%, a rate which was determined on the advance date as being the greater of (i) 8.75% and (ii) the sum of 8.47% and the 90 day U.S. LIBOR rate reported in the Wall Street Journal three business days prior to the funding date of the first tranche. Under the first tranche, the Company is required to make 12 monthly interest only payments after the funding date followed by a repayment schedule equal to 36 equal monthly payments of interest and principal. Upon maturity, the remaining balance of the first tranche and a final payment equal to 6.50% of the original principal amount advanced of the applicable tranche are payable. At the closing, the Company also agreed to pay a facility fee of 1.00% of the 2015 Term Loan Facility commitment. In addition, the Company issued warrants exercisable for a total of 114,436 shares of its common stock to the lenders at an exercise price of $2.84 per share, and with a term of ten years. Upon issuance, the fair value of a warrant liability of $0.3 million was recorded in the accompanying balance sheet and is being revalued at each balance sheet date until the warrants are exercised or expire. The Company’s obligations under the term loan facility are secured, subject to customary permitted liens and other agreed upon exceptions, by a perfected first priority interest in all of the Company’s tangible and intangible assets, excluding intellectual property. The Company also entered into a negative pledge agreement with the lenders pursuant to which the Company has agreed not to encumber any intellectual property. The 2015 Term Loan Facility contains customary representations and warranties and customary affirmative and negative covenants applicable to the Company, and also includes defined customary events of default which include but are not limited to a material adverse change in the Company’s business, operations or condition (financial or otherwise), a material impairment of the prospect of repayment of any portion of the term loan, or a material impairment in the perfection or priority of the collateral agent’s lien in the collateral or in the value of such collateral. As of December 31, 2016, the Company was in compliance with the term loan covenants and there were no events of default. The term loan facility, debt discounts and final payment balances as of December 31, 2016 and 2015 are as follows (in thousands): December 31, 2016 2015 Principal payments due under the loan facility $ 9,014 $ 10,000 Less: unamortized debt discount (599 ) (929 ) Plus: accreted value of final payment 383 237 Term loan facility, net $ 8,798 $ 9,308 Future principal payments due under the loan facility are as follows (in thousands): Principal Year ending December 31: 2017 3,137 2018 3,423 2019 2,454 Total future principal payments due under loan agreement $ 9,014

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	7. Commitments and Contingencies Operating Lease Commitments Rent expense was $0.3 million for each of the years ended December 31, 2016 and 2015. The Company leases 8,894 square feet of office space in Newark, California pursuant to a lease which commenced January 16, 2014 and expires on December 31, 2018. Future minimum lease payments under operating lease commitments are as follows (in thousands): Lease Year ending December 31: 2017 222 2018 228 Total future minimum payments $ 450 Indemnification In the normal course of business, the Company enters into contracts and agreements that contain a variety of representations and warranties and provide for general indemnification, including indemnification associated with product liability or infringement of intellectual property rights. The Company’s exposure under these agreements is unknown because it involves future claims that may be made against the Company that may be, but have not yet been, made. To date, the Company has not paid any claims or been required to defend any action related to these indemnification obligations, and no amounts have been accrued in the accompanying balance sheets related to these indemnification obligations. The Company has agreed to indemnify its executive officers and directors for losses and costs incurred in connection with certain events or occurrences, including advancing money to cover certain costs, subject to certain limitations. The maximum potential amount of future payments the Company could be required to make under this indemnification is unlimited; however, the Company maintains insurance policies that may limit its exposure and may enable it to recover a portion of any future amounts paid. Assuming the applicability of coverage, the willingness of the insurer to assume coverage, and subject to certain retention, loss limits, and other policy provisions, the Company believes the fair value of these indemnification obligations is not material. Accordingly, the Company has not recognized any liabilities relating to these obligations as of December 31, 2016 and 2015. No assurances can be given that the covering insurers will not attempt to dispute the validity, applicability, or amount of coverage without expensive litigation against these insurers, in which case the Company may incur substantial liabilities as a result of these indemnification obligations.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2016
Equity [Abstract]
Stockholders' Equity	8. Stockholders’ Equity The Company is authorized to issue 10,000,000 shares of preferred stock as of December 31, 2016 and 2015, respectively. The Company is authorized to issue 100,000,000 shares of common stock as of December 31, 2016 and 2015, respectively. Common Stock Issuances On July 25, 2014, the Company completed a public offering of 4.6 million shares of common stock at $5.50 per share, which the Company refers to as the 2014 public offering. Net proceeds to the Company in connection with the 2014 public offering were approximately $23.0 million after deducting underwriting discounts, commissions and offering expenses. On November 7, 2014, the Company filed a $100 million registration statement on Form S-3 with the SEC and also entered into an at-the-market facility (ATM) to sell up to $25 million of common stock under the registration statement, under which, as of December 31, 2015, the Company has sold shares of common stock with aggregate net proceeds of $4.3 million. On July 27, 2015, pursuant to a shelf registration statement on Form S-3, the Company completed the issuance of 8.2 million shares of its common stock at $2.81 per share in an underwritten public offering, which the Company refers to as the 2015 public offering. Net proceeds to the Company in connection with this offering were approximately $21.1 million after deducting underwriting discounts, commissions and other offering expenses. Common Stock Warrants In connection with a 2013 financing and the Company’s private placement of common stock and warrants in September 2013, October 2013 and January 2014, the Company issued five-year warrants to purchase 1,741,788 shares of the Company’s common stock at an exercise price of $5.75 per share (referred to as the 2013 financing warrants). The Company also issued seven-year warrants to purchase 121,739 shares of the Company’s common stock to certain lenders at an exercise price of $5.00 per share in September 2013 and in connection with the 2015 loan facility, the Company issued ten-year warrants to purchase 114,436 shares of its common stock to its lenders at an exercise price of $2.84 per share (referred to as the lender warrants). The 2013 financing warrants contain anti-dilution provisions that are contingent on the occurrence of a major transaction (e.g. merger, reorganization, business combination, change in control or a similar transaction, liquidation or bankruptcy) which precludes them from being indexed to the Company’s common stock. Such provisions could also result in the settlement of the 2013 financing warrants for more shares of common stock than the Company has authorized. Due to these provisions, the Company is required to account for the 2013 financing warrants and the lender warrants as liabilities at fair value. In addition, the estimated liability related to these warrants is required to be revalued at each reporting period until the earlier of the exercise of the warrants, at which time the liability will be revalued and reclassified to stockholders’ equity, or expiration of the warrants. These warrants were recorded at fair value upon issuance and were revalued at fair value as of December 31, 2016 and 2015 using a binomial lattice option pricing model. The resulting decreases in fair value of $0.1 million for the year ended December 31, 2016 and $11.1 million for the year ended December 31, 2015 were recorded as revaluation gains in other income (expense), net in the Company’s statement of operations and comprehensive loss. Shares of Common Stock Authorized for Issuance As of December 31, 2016 and December 31, 2015, the Company had reserved shares of authorized but unissued common stock as follows: December 31, December 31, Common stock warrants 1,667,398 1,667,398 Equity incentive plans 3,456,253 2,284,421 Total reserved shares of common stock 5,123,651 3,951,819

Stock Plans and Stock-Based Com

Stock Plans and Stock-Based Compensation	12 Months Ended
	Dec. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock Plans and Stock-Based Compensation	9. Stock Plans and Stock-Based Compensation Stock Plans In September 2013, the Company’s stockholders approved the 2013 Equity Incentive Plan (2013 Plan), under which shares of common stock are reserved for the granting of incentive stock options, nonstatutory stock options, stock appreciation rights, restricted stock awards, restricted stock unit awards, performance stock awards, performance cash awards and other stock awards by the Company. These awards may be granted to employees, members of the Board of Directors, and consultants. The 2013 Plan has a term of ten years and replaced the 2003 Equity Incentive Plan, which had similar terms. The 2013 Plan permits the Company to (i) grant incentive stock options to directors and employees at not less than 100% of the fair value of common stock on the date of grant; (ii) grant nonqualified options to employees, directors, and consultants at not less than 85% of fair value; (iii) award stock bonuses; and (iv) grant rights to acquire restricted stock at not less than 85% of fair value. Options generally vest over a four year period and have a term of ten years. Options granted to 10% stockholders have a maximum term of five years and require an exercise price equal to at least 110% of the fair value on the date of grant. The exercise price of all options granted to date has been at least equal to the fair value of common stock on the date of grant. The share reserve under the 2013 Plan will automatically increase on January 1 st st st Stock Plan Activity As of December 31, 2016, there were 496,120 shares available for issuance under the 2013 Plan. In accordance with the provisions of the 2013 Plan, the number of shares available for issuance under the plan automatically increased by 1,172,350 shares on January 1, 2017. The following table summarizes stock option activity: Shares Weighted- Weighted- Aggregate Outstanding as of December 31, 2014 991,010 $ 6.09 8.91 $ 4,559 Options granted 845,703 9.00 Options exercised — 0 Options forfeited (15,631 ) 4.75 Options expired (16,999 ) 12.31 Outstanding as of December 31, 2015 1,804,083 7.41 8.24 $ — Options granted 646,667 1.28 Options exercised — 0 Options forfeited (14,319 ) 4.50 Options expired (42,043 ) 25.01 Outstanding as of December 31, 2016 2,394,388 $ 5.46 7.75 $ 349 Vested and expected to vest as of December 31, 2016 2,351,745 $ 5.50 7.73 $ 331 Exercisable as of December 31, 2016 1,310,883 $ 6.15 7.18 $ 3 Vested and Unvested Awards The total fair value of options including performance options vested was $2.2 million for each of the years ended December 31, 2016 and 2015. As of December 31, 2016, and 2015 the total compensation expense related to unvested employee stock options including performance options to be recognized in future periods, excluding estimated forfeitures, was $3.5 million and $4.8 million, respectively. The weighted-average periods over which this compensation expense is expected to be recognized are 1.8 years and 2.6 years as of December 31, 2016 and 2015, respectively. Performance Options In July 2016, the Company granted 327,000 performance-based stock options (PSOs) to executives and senior officers. PSOs represent a contingent right to purchase the Company’s common stock upon the achievement of specific conditions. Specifically, these PSOs vest upon the achievement of certain clinical development and capital raising milestones which must occur before December 31, 2016. In December 2016, the PSOs were modified by extending the term by one month to January 31, 2017. The following table summarizes performance option activity: Shares Weighted- Outstanding as of December 31, 2015 — $ — Options granted 327,000 1.82 Outstanding as of December 31, 2016 327,000 $ 1.82 In 2016, the clinical development milestone was achieved and the related expense of $199,000 was recognized. The modification to extend the term of the PSOs did not have a material impact on the Company’s financial statements. The unrecognized stock-based compensation related to the remaining PSOs was $192,000 as of December 31, 2016, and its recognition is dependent upon the achievement of the capital raising milestone. Subsequent to December 31, 2016, the capital raising milestone was achieved within the modified term. Accordingly, all stock-based compensation expense related to this milestone will be recorded in 2017. Incentive Awards In December 2013, January 2014, and April 2014, as permitted by the 2013 Plan, the Company issued certain incentive awards to directors, employees and a consultant which are subject to 252,752 shares of the Company’s common stock and are exercisable at a weighted average price of $5.21 per share when vested. The Company may determine at its option whether to settle exercised awards in shares of common stock or in cash. Each recipient’s incentive award defines the number of common shares that may be acquired upon exercise provided the Company chooses to settle in shares. For awards settled in cash, the Company must pay the recipient the excess of the fair market value of the Company’s common stock on the date of exercise over the exercise price paid by the recipient multiplied by the number of shares the recipient would be entitled to receive had the award been settled in shares of the Company’s common stock. Pursuant to their terms, the incentive awards have a term of 10 years and were initially scheduled to vest 100% on the second anniversary of their grant date. However, as a result of the approval by Company’s shareholders of a 500,000 share increase to the 2013 Plan’s share reserve in June 2014, the incentive awards were automatically modified to vest monthly over four years effective from their grant date. The Company is recognizing the value of the incentive awards over the remaining four year vesting period. The Company recorded $272,000 and $323,000 of stock based compensation expense in the years ended December 31, 2016 and 2015, respectively, pertaining to its incentive awards. Options Granted to Nonemployees The Company has issued options to purchase shares of common stock to certain scientific advisors and consultants. The stock options have various exercise prices, a term of ten years, and vest over periods up to sixty months. The Company granted to these advisors and consultants options to purchase 18,000 and 10,000 shares of common stock, in 2016 and 2015, respectively. As of December 31, 2016, options to purchase 28,410 shares of common stock remained unvested, and compensation related to these stock options is subject to remeasurement each reporting period as the shares vest. In 2013, the Company also issued an incentive award for 2,335 shares to a scientific advisor, of which 584 shares remained unvested as of December 31, 2016. The Company recorded $17,510 and $21,265 of expense in the years ended December 31, 2016 and 2015, respectively, related to these options and awards. Stock-Based Compensation Expense Stock-based compensation expense, net of estimated forfeitures, included in the statements of operations and comprehensive loss is as follows (in thousands): Year Ended 2016 2015 Research and development $ 995 $ 844 General and administrative 1,478 1,643 Total stock-based compensation expense $ 2,473 $ 2,487 Valuation Assumptions The following table presents the weighted-average assumptions the Company used in the Black-Scholes option-pricing model to derive the grant date fair values of stock options and performance-based stock options along with the resulting estimated weighted-average grant date fair values per share: Year Ended December 31, 2016 2015 Expected term Options 6.1 yrs 6.1 yrs Performance options 5.1 yrs — Expected volatility Options 80 % 78 % Performance options 85 % — Risk-free interest rate Options 1.57 % 1.65 % Performance options 1.56 % — Expected dividend yield Options — — Performance options — — Weighted-average grant date fair value per share Options $ 0.89 $ 6.13 Performance options $ 1.20 — Expected Term The Company does not believe it can currently place reliance on its historical exercise and post-vesting termination activity to provide accurate data for estimating the expected term. Therefore, for stock option grants made during the years ended December 31, 2016 and 2015, the Company has opted to use the simplified method for estimating the expected term which is an average of the contractual term of the options and its ordinary vesting period. The expected term represents the period of time that options are expected to be outstanding. Expected Volatility As the Company has limited trading history for its common stock, the expected stock price volatility for the Company’s common stock was estimated by considering the volatility rates of similar publicly traded peer entities within the life sciences industry. The Company will continue to apply this process until a sufficient amount of historical information regarding the volatility of its own stock price becomes available. Risk-Free Interest Rate The risk-free interest rate assumption was based on U.S. Treasury instruments with constant maturities whose term was consistent with the expected term of stock options granted by the Company. Expected Dividend Yield The Company has never declared or paid cash dividends and does not plan to pay cash dividends in the foreseeable future. Consequently, the Company uses an expected dividend yield of zero. Forfeitures The Company estimates forfeitures at the time of grant and revises these estimates in subsequent periods if actual forfeitures differ from those estimates. Changes in forfeiture estimates impact compensation in the period in which the change occurs. The total intrinsic value of options exercised was not significant for the years ended December 31, 2016 and 2015.

401(k) Plan

401(k) Plan	12 Months Ended
	Dec. 31, 2016
Postemployment Benefits [Abstract]
401(k) Plan	10. 401(k) Plan The Company provides a qualified 401(k) savings plan for its employees. All employees are eligible to participate, provided they meet the requirements of the plan. While the Company may elect to match employee contributions, no such matching contributions have been made through December 31, 2016 and 2015.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Income Taxes	11. Income Taxes No provision for U.S. income taxes exists due to tax losses incurred in all periods presented. All losses incurred were U.S. based. Significant components of the Company’s deferred tax assets are as follows (in thousands): December 31 2016 2015 Deferred tax assets: Federal and state net operating loss carryforwards $ 88,111 $ 79,966 Capitalized research and development 22,272 22,287 Federal and state tax credit carryforwards 8,141 7,571 Stock based compensation 2,080 1,384 Other 974 628 Total deferred tax assets 121,578 111,836 Valuation allowance (121,578 ) (111,836 ) Net deferred tax assets $ — $ — Realization of the net deferred tax assets is dependent upon future taxable income, if any, the amount and timing of which is uncertain. Based on the weight of available positive and negative objective evidence, management believes it more likely than not that the Company’s deferred tax assets are not realizable. Accordingly, the net deferred tax assets have been fully offset by a valuation allowance. The net valuation allowance increased by $9.7 million during the year ended December 31, 2016 and increased $9.8 million during the year ended December 31, 2015. The following is a reconciliation of the expected statutory federal income tax provision to the actual income tax provision (in thousands): December 31 2016 2015 Expected income tax benefit at federal statutory tax rate $ (9,068 ) $ (5,280 ) Change in valuation allowance 9,775 9,815 State income taxes, net of federal benefit (458 ) (618 ) Permanent items 196 (3,542 ) Research credits (445 ) (375 ) Income tax (benefit) expense $ — $ — Pursuant to Internal Revenue Code (“IRC”), Section 382 and 383, use of the Company’s U.S. federal and state net operating loss and research and development income tax credit carryforwards may be limited in the event of a cumulative change in ownership of more than 50.0% within a three-year period. The Company completed an analysis under IRC Sections 382 and 383 through December 21, 2007 and determined that the Company’s net operating losses and research and development credits were subject to limitations due to changes in ownership through December 31, 2007. The net operating loss carryforwards reflected in the deferred tax assets at December 31, 2016 have been adjusted to reflect Section 382 limitations resulting from the ownership change. As the Company was in a net operating loss position for the years 2008-2016, the Company has not performed any additional analysis for IRC Sections 382 and 383 and there is a risk that additional changes in ownership could have occurred since December 31, 2007. 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. As of December 31, 2016, the Company has federal net operating loss carryforwards of $229.1 million and state net operating loss carryforwards of $175.1 million to offset future taxable income, if any. In addition, the Company has federal research and development tax credit carry forwards of $7.7 million and state research and development tax credit carryforwards of $6.3 million. If not utilized, the federal net operating loss and tax credit carryforwards will expire beginning in 2024 through 2036 and the state net operating loss carryforwards will expire beginning in 2017 through 2036. The state tax credit will carry forward indefinitely. The following table summarizes activity related to the Company’s gross unrecognized tax benefits (in thousands): Total Balances as of December 31, 2014 $ 1,991 Increases related to prior year tax positions — Increases related to 2015 tax positions 136 Balances as of December 31, 2015 $ 2,127 Increases related to prior year tax positions — Increases related to 2016 tax positions 159 Balances as of December 31, 2016 $ 2,286 The unrecognized tax benefits, if recognized, would not have an impact on the Company’s effective tax rate assuming the Company continues to maintain a full valuation allowance position. Based on prior year’s operations and experience, the Company does not expect a significant change to its unrecognized tax benefits over the next twelve months. The unrecognized tax benefits may increase or change during the next year for unexpected or unusual items for items that arise in the ordinary course of business. The Company files income tax returns in the U.S. federal and California jurisdiction and is not currently under examination by federal, state, or local taxing authorities for any open tax years. The tax years 1998 through 2016 remain open to examination by the major taxing authorities.

Related-Party Transactions

Related-Party Transactions	12 Months Ended
	Dec. 31, 2016
Related Party Transactions [Abstract]
Related-Party Transactions	12. Related-Party Transactions The Company paid a former member of its Board of Directors, who is also a member of its Scientific and Clinical Advisory Boards, a total of $60,000 in each of the years ended December 31, 2016 and 2015 in monthly cash retainers.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2016
Subsequent Events [Abstract]
Subsequent Events	13. Subsequent Events On January 1, 2017, the share reserve of the Company’s 2013 Equity Incentive Plan, or 2013 Plan, automatically increased by 1,172,350 shares. In addition, the Company granted to employees and consultants stock options to purchase 1,016,301 shares of common stock in January 2017. During January 2017, the Company utilized its ATM facility to offer and sell 124,100 shares of common stock for net proceeds of $158,000 as permitted under the Company’s shelf registration statement on Form S-3 and its related prospectus supplements. On February 2, 2017, pursuant to the Company’s shelf registration statement on Form S-3, the Company completed the issuance of 5.2 million shares of common stock at $1.93 per share which the Company refers to as the 2017 public offering. Net proceeds to the Company in connection with the 2017 public offering were approximately $9.2 million after deducting underwriting discounts, commissions and other offering expenses.

Organization and Description 21

Organization and Description of Business (Policies)	12 Months Ended
	Dec. 31, 2016
Accounting Policies [Abstract]
Liquidity	Liquidity The Company has incurred net operating losses and negative cash flows from operations since its inception. During the year ended December 31, 2016, the Company incurred a net loss of $26.7 million and used $23.4 million of cash in operations. At December 31, 2016, the Company had an accumulated deficit of $423.0 million. CymaBay expects to incur substantial research and development expenses as it continues to study its product candidates in clinical trials. To date, none of the Company’s product candidates have been approved for marketing and sale, and the Company has not recorded any revenue from product sales. As a result, management expects operating losses to continue in future years. The Company’s ability to achieve profitability is dependent primarily on its ability to successfully develop, acquire or in-license additional product candidates, continue clinical trials for product candidates currently in clinical development, obtain regulatory approvals, and support commercialization activities for partnered product candidates. Products developed by the Company will require approval of the U.S. Food and Drug Administration (FDA) or a foreign regulatory authority prior to commercial sale. The regulatory approval process is expensive, time-consuming, and uncertain, and any denial or delay of approval could have a material adverse effect on the Company. Even if approved, the Company’s products may not achieve market acceptance and will face competition from both generic and branded pharmaceutical products. As of December 31, 2016, the Company’s cash, cash equivalents and marketable securities totaled $17.0 million. These funds, together with $9.4 million received from financings and $5.0 million received from a license arrangement in January and February 2017, are expected to satisfy the Company’s liquidity requirements through at least the next 12 months. The Company expects to incur substantial expenditures in the future for the development and potential commercialization of its product candidates. Because of this, the Company expects its future liquidity and capital resource needs will be impacted by numerous factors, including but not limited to, the repayment of the Company’s facility loan, the timing of initiation of planned clinical trials, including phase 2 trials to study the therapeutic benefits of seladelpar on patients with certain orphan diseases. The Company has and expects to obtain additional funding to develop its products and fund future operating losses through equity offerings, debt financing, one or more possible licenses, collaborations or other similar arrangements with respect to development and/or commercialization rights of its product candidates, or a combination of the above. It is unclear if or when any such transactions will occur, on satisfactory terms or at all. The Company’s failure to raise capital as and when needed could have a negative impact on its financial condition and its ability to pursue its business strategies. If adequate funds are not available, the Company may be required to reduce current development activities or limit or cease operations.
Basis of Presentation and Use of Estimates	Basis of Presentation and Use of Estimates The accompanying financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (U.S. GAAP), which requires management to make informed estimates and assumptions that impact the amounts and disclosures reported in the financial statements and accompanying notes. Accounting estimates and assumptions are inherently uncertain. Management bases its estimates on historical experience and on assumptions believed to be reasonable under the circumstances. The estimation process often may yield a range of potentially reasonable estimates of the ultimate future outcomes, and management must select an amount that falls within that range of reasonable estimates. Actual results could differ materially from those estimates and assumptions. The Company believes significant judgment is involved in determining and in estimating the valuation of stock-based compensation, accrued clinical expenses, and equity instrument valuations. These estimates form the basis for making judgments about the carrying values of assets and liabilities when these values are not readily apparent from other sources. Estimates are assessed each reporting period and updated to reflect current information and any changes in estimates will generally be reflected in the period first identified.
Reclassifications	Reclassifications Accrued interest receivable as of December 31, 2015 which was previously presented separately has been combined with other current assets in the accompanying balance sheets to conform to the December 31, 2016 presentation. Additionally, the Company has reclassified retainer fees paid to a vendor from prepaid expenses to other assets in the accompanying balance sheet as of December 31, 2015 to conform to the December 31, 2016 presentation.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The Company’s financial instruments during the periods reported consist of cash and cash equivalents, marketable securities, prepaid expenses, other current assets, accounts payable, accrued interest payable, accrued expenses, the Facility Loan, and warrant liabilities. Fair value estimates of these instruments are made at a specific point in time, based on relevant market information. These estimates may be subjective in nature and involve uncertainties and matters of significant judgment. The carrying amounts of financial instruments such as cash and cash equivalents, prepaid expenses, other current assets, accounts payable, accrued expenses, and accrued interest payable approximate the related fair values due to the short maturities of these instruments. Based on prevailing borrowing rates available to the Company for loans with similar terms, the Company believes the fair value of the Facility Loan, considering level 2 inputs, approximates its carrying value. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants at the measurement date. Assets and liabilities that are measured at fair value are reported using a three-level fair value hierarchy that prioritizes the inputs used to measure fair value. This hierarchy maximizes the use of observable inputs and maximizes the use of unobservable inputs and is as follows: Level 1—Quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date. Level 2—Inputs other than quoted prices in active markets that are observable for the asset or liability, either directly or indirectly. Level 3—Inputs that are significant to the fair value measurement and are unobservable (i.e. supported by little market activity), which requires the reporting entity to develop its own valuation techniques and assumptions. The following tables present the fair value of the Company’s financial assets and liabilities measured at fair value on a recurring basis using the above input categories (in thousands): (In thousands) As of December 31, 2016 Description Level 1 Level 2 Level 3 Fair Value Cash equivalents: Money market funds $ 9,456 $ — $ — $ 9,456 Commercial paper — 599 — 599 Corporate debt securities — 500 — 500 Total cash equivalents 9,456 1,099 — 10,555 Short-term investments: Commercial paper — 4,295 — 4,295 Corporate debt securities — 2,204 — 2,204 Total short-term investments — 6,499 — 6,499 Total assets measured at fair value $ 9,456 $ 7,598 $ — $ 17,054 Warrant liability $ — $ — $ 1,145 $ 1,145 Total liabilities measured at fair value $ — $ — $ 1,145 $ 1,145 (In thousands) As of December 31, 2015 Description Level 1 Level 2 Level 3 Fair Value Cash equivalents: Money market funds $ 6,942 $ — $ — $ 6,942 Total cash equivalents $ 6,942 $ — $ — $ 6,942 Short-term investments: Commercial paper — 5,992 — 5,992 Government debt securities — 1,507 — 1,507 Corporate debt securities — 21,654 — 21,654 Asset-backed securities — 4,621 — 4,621 Total short-term investments — 33,774 — 33,774 Total assets measured at fair value $ 6,942 $ 33,774 $ — $ 40,716 Warrant liability $ — $ — $ 1,220 $ 1,220 Total liabilities measured at fair value $ — $ — $ 1,220 $ 1,220 The Company estimates the fair value of its money market funds, commercial paper, corporate debt, asset backed securities, and government debt securities by taking into consideration valuations obtained from third-party pricing services. The pricing services utilize industry standard valuation models, including both income and market-based approaches, for which all significant inputs are observable, either directly or indirectly, to estimate fair value. These inputs include reported trades of and broker/dealer quotes on the same or similar securities, issuer credit spreads; benchmark securities; prepayment/default projections based on historical data; and other observable inputs. There were no transfers between Level 1 and Level 2 during the periods presented. As of December 31, 2016 and 2015, financial instruments measured using Level 3 inputs consisted of the Company’s warrants which are accounted for as liabilities. The warrants are valued using a binomial lattice option-pricing model, the significant inputs for which include exercise price of the warrants, market price of the underlying common shares, expected term, expected volatility, the risk-free rate, key strategic initiatives, probability of success related to those initiatives, and the expected changes in stock price that follow announcements of the Company’s strategic initiatives. Changes to any of the inputs to the option-pricing models used by the Company can have a significant impact to the estimated fair value of the warrants. The following tables set forth a summary of the changes in the fair value of our liabilities measured using Level 3 inputs (in thousands): For the Twelve 2016 2015 Balance, beginning of period $ 1,220 $ 13,596 Issuance of financial instrument — 258 Change in fair value (75 ) (11,121 ) Settlement of financial instrument — (1,513 ) Balance, end of period $ 1,145 $ 1,220
Cash, Cash Equivalents, and Marketable Securities	Cash, Cash Equivalents, and Marketable Securities The Company considers all highly liquid investments with a remaining maturity of 90 days or less at the time of purchase to be cash equivalents. Cash and cash equivalents consist of deposits with commercial banks in checking, interest-bearing, and demand money market accounts. The Company invests excess cash in marketable securities with high credit ratings which are classified in Level 1 and Level 2 of the fair value hierarchy. These securities consist primarily of corporate debt, commercial paper, and asset-backed securities and are classified as “available-for-sale.” Management may liquidate any of these investments in order to meet the Company’s liquidity needs in the next year. Accordingly, any investments with contractual maturities greater than one year from the balance sheet date are classified as short-term in the accompanying balance sheets. Realized gains and losses from the sale of marketable securities, if any, are calculated using the specific-identification method. Realized gains and losses and declines in value judged to be other-than- temporary are included in interest income or expense in the statements of operations and comprehensive loss. Unrealized holding gains and losses are reported in accumulated other comprehensive loss in the balance sheets. To date, the Company has not recorded any impairment charges on its marketable securities related to other-than-temporary declines in market value. In determining whether a decline in market value is other-than-temporary, various factors are considered, including the cause, duration of time and severity of the impairment, any adverse changes in the investees’ financial condition, and the Company’s intent and ability to hold the security for a period of time sufficient to allow for an anticipated recovery in market value.
Restricted Cash	Restricted Cash The Company is required to maintain compensating cash balances with financial institutions that provide the Company with its corporate credit cards. As of December 31, 2016 and 2015, cash restricted under these arrangements was $170,000. These amounts are presented in other assets on the accompanying balance sheets.
Concentration of Credit Risk	Concentration of Credit Risk Cash, cash equivalents, and marketable securities consist of financial instruments that potentially subject the Company to a concentration of credit risk to the extent of the fair value recorded in the balance sheet. The Company invests cash that is not required for immediate operating needs primarily in highly liquid instruments that bear minimal risk. The Company has established guidelines relating to the quality, diversification, and maturities of securities to enable the Company to manage its credit risk. We are exposed to credit risk in the event of a default by the financial institutions holding our cash, cash equivalents and investments and issuers of investments to the extent recorded on the balance sheets. Certain materials and key components that the Company utilizes in its operations are obtained through single suppliers. Since the suppliers of key components and materials must be named in a new drug application (NDA) filed with the U.S. Food and Drug Administration (FDA) for a product, significant delays can occur if the qualification of a new supplier is required. If delivery of material from the Company’s suppliers were interrupted for any reason, the Company may be unable to supply any of its product candidates for clinical trials.
Property and Equipment	Property and Equipment Property and equipment is recorded at cost, less accumulated depreciation and amortization. Depreciation and amortization is calculated using the straight-line method, and the cost is amortized over the estimated useful lives of the respective assets, generally three to seven years. Leasehold improvements are amortized over the shorter of the useful lives or the non-cancelable term of the related lease. Maintenance and repair costs are charged as expense in the statements of operations and comprehensive loss as incurred.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets The Company reviews long-lived assets for impairment whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. An impairment loss is recognized if the estimated undiscounted future cash flow expected to result from the use and eventual disposition of an asset is less than the carrying amount. While the Company’s current and historical operating losses and cash flows are indicators of impairment, the Company believes the future cash flows to be received support the carrying value of its long-lived assets. Accordingly, the Company has not recognized any impairment losses as of December 31, 2016.
Deferred Rent	Deferred Rent The Company records its costs under facility operating lease agreements as rent expense. Rent expense is recognized on a straight-line basis over the non-cancelable term of the operating lease. The difference between the actual amounts paid and amounts recorded as rent expense is recorded as deferred rent in the accompanying balance sheets.
Revenue Recognition	Revenue Recognition The Company recognizes revenue when (i) persuasive evidence of an arrangement exists, (ii) delivery has occurred or services have been rendered, (iii) the price is fixed or determinable, and (iv) collectability is reasonably assured. Payments received in advance of work performed are recorded as deferred revenue and recognized when earned. Collaboration and license agreements may include non-refundable If the Company determines that multiple deliverables in an arrangement exist, the consideration is allocated to one or more units of accounting based upon the relative-selling-price The Company recognizes payments that are contingent upon achievement of a substantive milestone in their entirety in the period in which the milestone is achieved. Milestones are defined as events that can only be achieved based on the Company’s performance and there is substantive uncertainty about whether the event will be achieved at the inception of the arrangement. Events that are contingent only on the passage of time or only on counterparty performance are not considered milestones subject to this guidance. Further, the amounts received must relate solely to prior performance, be reasonable relative to all of the deliverables and payment terms within the agreement and commensurate with the Company’s performance to achieve the milestone after commencement of the agreement. Any contingent payment that becomes payable upon achievement of events that are not considered substantive milestones are allocated to the units of accounting previously identified at the inception of an arrangement when the contingent payment is received and revenue is recognized based on the revenue recognition criteria for each unit of accounting.
Research and Development Expenses	Research and Development Expenses Research and development expenses consist of costs incurred in identifying, developing, and testing product candidates. These expenses consist primarily of costs for research and development personnel, including related stock-based compensation; contract research organizations (CRO) and other third parties that assist in managing, monitoring, and analyzing clinical trials; investigator and site fees; laboratory services; consultants; contract manufacturing services; non-clinical studies, including materials; and allocated expenses, such as depreciation of assets, and facilities and information technology that support research and development activities. Research and development costs are expensed as incurred, including expenses that may or may not be reimbursed under research and development funding arrangements. Payments made prior to the receipt of goods or services to be used in research and development are recorded as prepaid assets until the goods are received or services are rendered. Such payments are evaluated for current or long term classification based on when they will be realized. The Company records expenses related to clinical studies and manufacturing development activities based on its estimates of the services received and efforts expended pursuant to contracts with multiple CROs and manufacturing vendors that conduct and manage these activities on its behalf. The financial terms of these agreements are subject to negotiation, vary from contract to contract, and may result in uneven payment flows. There may be instances in which payments made to the Company’s vendors will exceed the level of services provided and result in a prepayment of the expense. Payments under some of these contracts depend on factors such as the successful enrollment of subjects and the completion of clinical trial milestones. In amortizing or accruing service fees, the Company estimates the time period over which services will be performed, enrollment of subjects, number of sites activated and the level of effort to be expended in each period. If the actual timing of the performance of services or the level of effort varies from the Company’s estimate, the Company will adjust the accrued or prepaid expense balance accordingly. To date, there have been no material differences from the Company’s estimates to the amounts actually incurred.
Stock-Based Compensation	Stock-Based Compensation Employee and director stock-based compensation is measured at fair value on the grant date of the award. Compensation cost is recognized as expense on a straight-line basis over the vesting period for options and on an accelerated basis for stock options with performance conditions, net of estimated forfeitures. For stock options with performance conditions, the Company evaluates the probability of achieving performance conditions at each reporting date. The Company begins to recognize the expense when it is deemed probable that the performance conditions will be met. The Company uses the Black-Scholes option pricing model to determine the fair value of stock option awards. The determination of fair value for stock-based awards using an option-pricing model requires management to make certain assumptions regarding subjective input variables such as expected term, dividends, volatility and forfeiture rates. The Company is also required to make estimates as to the probability of achieving the specific performance criteria. If actual results are not consistent with the Company’s assumptions and judgments used in making these estimates, the Company may be required to increase or decrease compensation expense, which could be material to the Company’s results of operations. Equity awards granted to non-employees are valued using the Black-Scholes option pricing model. Stock-based compensation expense for nonemployee services is subject to remeasurement as the underlying equity instruments vest and is recognized as an expense over the period during which services are received.
Common Stock Warrant Liabilities	Common Stock Warrant Liabilities The Company’s outstanding common stock warrants issued in connection with certain equity and debt financings that occurred in 2013 through 2015 are classified as liabilities in the accompanying balance sheets because of certain contractual terms that preclude equity classification. The warrants are recorded at fair value using a binomial lattice option-pricing model. The warrants are re-measured at each financial reporting period until the warrants are exercised or expire, with any changes in fair value being recognized as a component of other income (expense), net in the accompanying condensed statements of operations and comprehensive loss.
Income Taxes	Income Taxes The Company utilizes the liability method of accounting for income taxes. Under this method, deferred tax assets and liabilities are determined based on differences between the financial reporting and the tax bases of assets and liabilities and are measured using enacted tax rates and laws that will be in effect when the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date. A valuation allowance is recorded when it is more likely than not that all or part of a deferred tax asset will not be realized. When the Company establishes or reduces the valuation allowance related to the deferred tax assets, the provision for income taxes will increase or decrease, respectively, in the period such determination is made. The accounting guidance for uncertainty in income taxes prescribes a recognition threshold and measurement attribute criteria for the financial recognition and measurement of tax positions taken or expected to be taken in a tax return. For those benefits to be recognized, a tax position must be more likely than not to be sustained upon examination based on the technical merits of the position. The Company is required to file federal and state income tax returns in the United States. The preparation of these income tax returns requires the Company to interpret the applicable tax laws and regulations in effect which could affect the amount of tax paid to these jurisdictions. The Company records interest related to income tax reserves, if any, as interest expense, and any penalties would be recorded as other expense in the statements of operations and comprehensive loss. There was no interest or penalties related to income tax reserves during the years ended December 31, 2016 and 2015.
Comprehensive Loss	Comprehensive Loss Comprehensive loss includes net loss and net unrealized gains and losses on marketable securities, which are presented in a single continuous statement. Comprehensive loss is disclosed in the statements of stockholders’ equity, and is stated net of related tax effects, if any.
Net Income (Loss) Per Common Share	Net Income (Loss) Per Common Share Basic net loss per share of common stock is based on the weighted average number of shares of common stock outstanding equivalents during the period. Diluted net loss per share of common stock is calculated as the weighted average number of shares of common stock outstanding adjusted to include the assumed exercises of stock options and common stock warrants, if dilutive. The calculation of diluted loss per share also requires that, to the extent the average market price of the underlying shares for the reporting period exceeds the exercise price of the common stock warrants and the presumed exercise of such securities are dilutive to earnings (loss) per share for the period, adjustments to net income or net loss used in the calculation are required to remove the change in fair value of the common stock warrant liability for the period. Likewise, adjustments to the denominator are required to reflect the related dilutive shares. In all periods presented, the Company’s outstanding stock options were excluded from the calculation of net loss per share because the effect would be antidilutive. The following table sets forth the computation of basic and diluted net loss per share (in thousands, except share and per share amounts): Year Ended December 31, 2016 2015 Numerator: Net loss allocated to common stock—basic $ (26,671 ) $ (15,529 ) Adjustment for revaluation of warrants — (94 ) Net loss allocated to common stock—diluted $ (26,671 ) $ (15,623 ) Denominator: Weighted average number of common stock shares outstanding—basic 23,447,003 18,900,473 Dilutive common stock warrants — 16,740 Weighted average number of common stock shares outstanding—diluted 23,447,003 18,917,213 Net loss per share—basic $ (1.14 ) $ (0.82 ) Net loss per share—diluted $ (1.14 ) $ (0.83 ) The following table shows the total outstanding securities considered anti-dilutive and therefore excluded from the computation of diluted net loss per share (in thousands): Year Ended 2016 2015 Common stock warrants 1,667 1,553 Common stock options 2,394 1,804 Performance-based stock options 327 — Incentive awards 239 245 4,627 3,602
Recent Accounting Pronouncements	Recent Accounting Pronouncements Accounting Standards Update 2014-09 In May 2014, the FASB issued Accounting Standards Update 2014-09, Revenue from Contracts with Customers and related amendments. Subsequently, the Financial Accounting Standards Board (the FASB) issued the following standards related to ASU 2014-09: ASU No. 2016-08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations; ASU No. 2016-10, Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing; and ASU No. 2016-12, Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients. This guidance outlines a new, and single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes nearly all of the existing revenue recognition guidance, including industry-specific guidance. This new revenue recognition model provides a five-step analysis in determining when and how revenue is recognized. The new model will require revenue recognition to depict the transfer of promised goods or services to customers in an amount that reflects the consideration a company expects to receive in exchange for those goods or services. The new revenue standard permits two methods of adoption: retrospectively to each prior reporting period presented (full retrospective method), or retrospectively with the cumulative effect of initially applying the guidance recognized at the date of initial application (the modified retrospective method). The Company plans to adopt the new revenue standard in the first quarter of 2018 using the modified retrospective method. While the Company has not completed an assessment of the impact of adoption, the adoption of this guidance may have a material effect on the Company’s financial statements. At the end of 2016, the Company entered into a license agreement. Before executing this agreement, the Company has had no revenues for the last two years. The consideration the Company is eligible to receive under this agreement includes an upfront payment, milestone payments, and royalties. This license agreement is unique and will need to be assessed separately under the five-step process under the new standard. The Company is currently in the early stages of analyzing this agreement to determine the differences in the accounting treatment under the new revenue standard compared to the current accounting treatment. The new revenue standard differs from the current accounting standard in many respects, such as in the accounting for variable consideration, including milestone payments and royalties. Accounting Standards Update 2014-15 In August 2014, the FASB issued guidance codified in ASC 205, Presentation of Financial Statements — Going Concern. Accounting Standards Update 2014-15 requires an entity’s management to evaluate whether there are conditions or events, considered in the aggregate, that raise substantial doubt about the entity’s ability to continue as a going concern and if those conditions exist, to make the required disclosures. The ASU aligns the interpretation of substantial doubt with the definition of “probable” pursuant to ASC 450, Contingencies Accounting Standards Update 2015-03 In April 2015, the FASB issued ASU No. 2015-03, Interest—Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issuance Costs, which requires debt issuance costs related to a recognized debt liability to be presented in the balance sheet as a direct deduction from the corresponding debt liability rather than as an asset. The Company adopted this ASU with retrospective application in the first quarter of 2016. As the Company does not have any debt issuance costs recorded as assets, the adoption of this standard did not have any impact on the Company’s financial statements. Accounting Standards Update 2016-02 In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842). The new standard requires the recognition of assets and liabilities arising from lease transactions on the balance sheet and the disclosure of key information about leasing arrangements. Accordingly, a lessee will recognize a lease asset for its right to use the underlying asset and a lease liability for the corresponding lease obligation. Both the asset and liability will initially be measured at the present value of the future minimum lease payments over the lease term. Subsequent measurement, including the presentation of expenses and cash flows, will depend on the classification of the lease as either a finance or an operating lease. Initial costs directly attributable to negotiating and arranging the lease will be included in the asset. Lessees will also be required to provide additional qualitative and quantitative disclosures regarding the amount, timing and uncertainty of cash flows arising from leases. The new standard is effective for fiscal years beginning after December 15, 2018, and interim periods therein. Early adoption is permitted. The Company is currently evaluating the impact this guidance will have on its financial statements. Accounting Standards Update 2016-09 In March 2016, the FASB issued ASU No. 2016-09, Improvements to Employee Share-Based Payment Accounting, which amends ASC Topic 718, Compensation – Stock Compensation. This guidance simplifies the accounting for the taxes related to stock based compensation, requiring excess tax benefits and deficiencies to be recognized as a component of income tax expense rather than equity. This guidance also requires excess tax benefits and deficiencies to be presented as an operating activity on the statement of cash flows and allows an entity to make an accounting policy election to either estimate expected forfeitures or to account for them as they occur. The amendments in this ASU are effective for annual periods beginning after December 15, 2016 and for the interim periods therein. Early adoption is permitted. The Company is currently evaluating the impact this guidance will have on its financial statements.

Summary of Significant Accoun22

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2016
Accounting Policies [Abstract]
Schedule of Fair Value Assets and Liabilities Measured on Recurring Basis	(In thousands) As of December 31, 2016 Description Level 1 Level 2 Level 3 Fair Value Cash equivalents: Money market funds $ 9,456 $ — $ — $ 9,456 Commercial paper — 599 — 599 Corporate debt securities — 500 — 500 Total cash equivalents 9,456 1,099 — 10,555 Short-term investments: Commercial paper — 4,295 — 4,295 Corporate debt securities — 2,204 — 2,204 Total short-term investments — 6,499 — 6,499 Total assets measured at fair value $ 9,456 $ 7,598 $ — $ 17,054 Warrant liability $ — $ — $ 1,145 $ 1,145 Total liabilities measured at fair value $ — $ — $ 1,145 $ 1,145 (In thousands) As of December 31, 2015 Description Level 1 Level 2 Level 3 Fair Value Cash equivalents: Money market funds $ 6,942 $ — $ — $ 6,942 Total cash equivalents $ 6,942 $ — $ — $ 6,942 Short-term investments: Commercial paper — 5,992 — 5,992 Government debt securities — 1,507 — 1,507 Corporate debt securities — 21,654 — 21,654 Asset-backed securities — 4,621 — 4,621 Total short-term investments — 33,774 — 33,774 Total assets measured at fair value $ 6,942 $ 33,774 $ — $ 40,716 Warrant liability $ — $ — $ 1,220 $ 1,220 Total liabilities measured at fair value $ — $ — $ 1,220 $ 1,220
Schedule of Changes in Fair Value of Liabilities	The following tables set forth a summary of the changes in the fair value of our liabilities measured using Level 3 inputs (in thousands): For the Twelve 2016 2015 Balance, beginning of period $ 1,220 $ 13,596 Issuance of financial instrument — 258 Change in fair value (75 ) (11,121 ) Settlement of financial instrument — (1,513 ) Balance, end of period $ 1,145 $ 1,220
Computation of Basic and Diluted Net Loss per Share	The following table sets forth the computation of basic and diluted net loss per share (in thousands, except share and per share amounts): Year Ended December 31, 2016 2015 Numerator: Net loss allocated to common stock—basic $ (26,671 ) $ (15,529 ) Adjustment for revaluation of warrants — (94 ) Net loss allocated to common stock—diluted $ (26,671 ) $ (15,623 ) Denominator: Weighted average number of common stock shares outstanding—basic 23,447,003 18,900,473 Dilutive common stock warrants — 16,740 Weighted average number of common stock shares outstanding—diluted 23,447,003 18,917,213 Net loss per share—basic $ (1.14 ) $ (0.82 ) Net loss per share—diluted $ (1.14 ) $ (0.83 )
Anti-Dilutive Securities Excluded from the Computation of Diluted Net Loss per Share	The following table shows the total outstanding securities considered anti-dilutive and therefore excluded from the computation of diluted net loss per share (in thousands): Year Ended 2016 2015 Common stock warrants 1,667 1,553 Common stock options 2,394 1,804 Performance-based stock options 327 — Incentive awards 239 245 4,627 3,602

Marketable Securities (Tables)

Marketable Securities (Tables)	12 Months Ended
	Dec. 31, 2016
Cash and Cash Equivalents [Abstract]
Marketable Available-for-Sale Securities	Marketable available-for-sale securities as of December 31, 2016 and 2015 consist of the following (in thousands): Amortized Gross Gross Estimated As of December 31, 2016: Short-term investments: Commercial paper $ 4,295 $ — $ — $ 4,295 Corporate debt securities 2,205 — (1 ) 2,204 $ 6,500 $ — $ (1 ) $ 6,499 Amortized Gross Gross Estimated As of December 31, 2015: Short-term investments: Commercial paper $ 5,992 $ — $ — $ 5,992 Government debt securities 1,509 — (2 ) 1,507 Corporate debt securities 21,671 — (17 ) 21,654 Asset-backed securities 4,623 — (2 ) 4,621 $ 33,795 $ — $ (21 ) $ 33,774

Certain Balance Sheet Items (Ta

Certain Balance Sheet Items (Tables)	12 Months Ended
	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Property and Equipment	Property and equipment consist of the following (in thousands): December 31, December 31, Office and computer equipment $ 177 $ 176 Purchased software 83 46 Furniture and fixtures 38 33 Leasehold improvements 65 66 Total 363 321 Less accumulated depreciation and amortization (286 ) (257 ) Property and equipment, net $ 77 $ 64
Accrued Liabilities	Accrued liabilities consist of the following (in thousands): December 31, December 31, Accrued compensation $ 1,839 $ 1,010 Accrued pre-clinical and clinical trial expenses 1,623 2,015 Accrued professional fees 982 283 Other accruals 57 28 Total accrued liabilities $ 4,501 $ 3,336

Facility Loans (Tables)

Facility Loans (Tables)	12 Months Ended
	Dec. 31, 2016
Debt Disclosure [Abstract]
Schedule of Term Loan Facility, Debt Discounts and Final Payment	The term loan facility, debt discounts and final payment balances as of December 31, 2016 and 2015 are as follows (in thousands): December 31, 2016 2015 Principal payments due under the loan facility $ 9,014 $ 10,000 Less: unamortized debt discount (599 ) (929 ) Plus: accreted value of final payment 383 237 Term loan facility, net $ 8,798 $ 9,308
Schedule of Future Principal Payments Due under Loan Facility	Future principal payments due under the loan facility are as follows (in thousands): Principal Year ending December 31: 2017 3,137 2018 3,423 2019 2,454 Total future principal payments due under loan agreement $ 9,014

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Future Minimum Lease Payments	Future minimum lease payments under operating lease commitments are as follows (in thousands): Lease Year ending December 31: 2017 222 2018 228 Total future minimum payments $ 450

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2016
Equity [Abstract]
Reserved Shares of Authorized but Unissued Common Stock	As of December 31, 2016 and December 31, 2015, the Company had reserved shares of authorized but unissued common stock as follows: December 31, December 31, Common stock warrants 1,667,398 1,667,398 Equity incentive plans 3,456,253 2,284,421 Total reserved shares of common stock 5,123,651 3,951,819

Stock Plans and Stock-Based C28

Stock Plans and Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2016
Summary of Stock Option Activity	The following table summarizes stock option activity: Shares Weighted- Weighted- Aggregate Outstanding as of December 31, 2014 991,010 $ 6.09 8.91 $ 4,559 Options granted 845,703 9.00 Options exercised — 0 Options forfeited (15,631 ) 4.75 Options expired (16,999 ) 12.31 Outstanding as of December 31, 2015 1,804,083 7.41 8.24 $ — Options granted 646,667 1.28 Options exercised — 0 Options forfeited (14,319 ) 4.50 Options expired (42,043 ) 25.01 Outstanding as of December 31, 2016 2,394,388 $ 5.46 7.75 $ 349 Vested and expected to vest as of December 31, 2016 2,351,745 $ 5.50 7.73 $ 331 Exercisable as of December 31, 2016 1,310,883 $ 6.15 7.18 $ 3
Summary of Stock-Based Compensation Expense, Net of Estimated Forfeitures	Stock-based compensation expense, net of estimated forfeitures, included in the statements of operations and comprehensive loss is as follows (in thousands): Year Ended 2016 2015 Research and development $ 995 $ 844 General and administrative 1,478 1,643 Total stock-based compensation expense $ 2,473 $ 2,487
Estimated Weighted-Average Grant Date Fair Value	The following table presents the weighted-average assumptions the Company used in the Black-Scholes option-pricing model to derive the grant date fair values of stock options and performance-based stock options along with the resulting estimated weighted-average grant date fair values per share: Year Ended December 31, 2016 2015 Expected term Options 6.1 yrs 6.1 yrs Performance options 5.1 yrs — Expected volatility Options 80 % 78 % Performance options 85 % — Risk-free interest rate Options 1.57 % 1.65 % Performance options 1.56 % — Expected dividend yield Options — — Performance options — — Weighted-average grant date fair value per share Options $ 0.89 $ 6.13 Performance options $ 1.20 —
Performance Option [Member]
Summary of Stock Option Activity	The following table summarizes performance option activity: Shares Weighted- Outstanding as of December 31, 2015 — $ — Options granted 327,000 1.82 Outstanding as of December 31, 2016 327,000 $ 1.82

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Components of Deferred Tax Assets	Significant components of the Company’s deferred tax assets are as follows (in thousands): December 31 2016 2015 Deferred tax assets: Federal and state net operating loss carryforwards $ 88,111 $ 79,966 Capitalized research and development 22,272 22,287 Federal and state tax credit carryforwards 8,141 7,571 Stock based compensation 2,080 1,384 Other 974 628 Total deferred tax assets 121,578 111,836 Valuation allowance (121,578 ) (111,836 ) Net deferred tax assets $ — $ —
Summary of Reconciliation of Expected Statutory Federal Income Tax Provision to Actual Income Tax Provision	The following is a reconciliation of the expected statutory federal income tax provision to the actual income tax provision (in thousands): December 31 2016 2015 Expected income tax benefit at federal statutory tax rate $ (9,068 ) $ (5,280 ) Change in valuation allowance 9,775 9,815 State income taxes, net of federal benefit (458 ) (618 ) Permanent items 196 (3,542 ) Research credits (445 ) (375 ) Income tax (benefit) expense $ — $ —
Summary of Gross Unrecognized Tax Benefits	The following table summarizes activity related to the Company’s gross unrecognized tax benefits (in thousands): Total Balances as of December 31, 2014 $ 1,991 Increases related to prior year tax positions — Increases related to 2015 tax positions 136 Balances as of December 31, 2015 $ 2,127 Increases related to prior year tax positions — Increases related to 2016 tax positions 159 Balances as of December 31, 2016 $ 2,286

Organization and Description 30

Organization and Description of Business - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Net loss	$ (26,671)	$ (15,529)
Cash flows from operating activities	(23,353)	(23,324)
Accumulated deficit	(422,959)	$ (396,288)
Cash and cash equivalents and marketable securities	17,000
Cash received from from financings	9,400
Cash received from license agreement	$ 5,000

Summary of Significant Accoun31

Summary of Significant Accounting Policies - Schedule of Fair Value Assets and Liabilities Measured on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	$ 17,054	$ 40,716
Total liabilities measured at fair value	1,145	1,220
Warrant Liability [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total liabilities measured at fair value	1,145	1,220
Cash Equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	10,555	6,942
Cash Equivalents [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	9,456	6,942
Cash Equivalents [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	599
Cash Equivalents [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	500
Short-term Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	6,499	33,774
Short-term Investments [Member] | Government Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value		1,507
Short-term Investments [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	4,295	5,992
Short-term Investments [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	2,204	21,654
Short-term Investments [Member] | Asset-backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value		4,621
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	9,456	6,942
Level 1 [Member] | Cash Equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	9,456	6,942
Level 1 [Member] | Cash Equivalents [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	9,456	6,942
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	7,598	33,774
Level 2 [Member] | Cash Equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	1,099
Level 2 [Member] | Cash Equivalents [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	599
Level 2 [Member] | Cash Equivalents [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	500
Level 2 [Member] | Short-term Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	6,499	33,774
Level 2 [Member] | Short-term Investments [Member] | Government Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value		1,507
Level 2 [Member] | Short-term Investments [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	4,295	5,992
Level 2 [Member] | Short-term Investments [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	2,204	21,654
Level 2 [Member] | Short-term Investments [Member] | Asset-backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value		4,621
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total liabilities measured at fair value	1,145	1,220
Level 3 [Member] | Warrant Liability [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total liabilities measured at fair value	$ 1,145	$ 1,220

Summary of Significant Accoun32

Summary of Significant Accounting Policies - Schedule of Changes in Fair Value of Liabilities (Detail) - Level 3 [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Instruments Classified in Shareholders' Equity Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	$ 1,220	$ 13,596
Issuance of financial instrument		258
Change in fair value	(75)	(11,121)
Settlement of financial instrument		(1,513)
Ending Balance	$ 1,145	$ 1,220

Summary of Significant Accoun33

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Product Information [Line Items]
Cash and cash equivalents, maturity description	90 days or less
Short-term contractual maturities	1 year
Restricted cash	$ 170,000	$ 170,000
Impairment losses	0
Interest or penalties related to income taxes	$ 0	$ 0
Minimum [Member]
Product Information [Line Items]
Property and equipment, estimated useful lives	3 years
Maximum [Member]
Product Information [Line Items]
Property and equipment, estimated useful lives	7 years

Summary of Significant Accoun34

Summary of Significant Accounting Policies - Computation of Basic and Diluted Net Loss per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Numerator:
Net loss allocated to common stock-basic	$ (26,671)	$ (15,529)
Adjustment for revaluation of warrants		(94)
Net loss allocated to common stock-diluted	$ (26,671)	$ (15,623)
Denominator:
Weighted average number of common stock shares outstanding-basic	23,447,003	18,900,473
Dilutive common stock warrants		16,740
Weighted average number of common stock shares outstanding-diluted	23,447,003	18,917,213
Net loss per share-basic	$ (1.14)	$ (0.82)
Net loss per share-diluted	$ (1.14)	$ (0.83)

Summary of Significant Accoun35

Summary of Significant Accounting Policies - Anti-Dilutive Securities Excluded from the Computation of Diluted Net Loss per Share (Detail) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the computation of diluted loss per share	4,627	3,602
Performance Option [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the computation of diluted loss per share	327
Warrants [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the computation of diluted loss per share	1,667	1,553
Common Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the computation of diluted loss per share	2,394	1,804
Incentive Awards [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the computation of diluted loss per share	239	245

Marketable Securities - Marketa

Marketable Securities - Marketable Available-for-Sale Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 6,500	$ 33,795
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1)	(21)
Estimated Fair Value	6,499	33,774
Corporate Debt Securities [Member] | Short-term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,205	21,671
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1)	(17)
Estimated Fair Value	2,204	21,654
Asset-backed Securities [Member] | Short-term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		4,623
Gross Unrealized Gains		0
Gross Unrealized Losses		(2)
Estimated Fair Value		4,621
Commercial Paper [Member] | Short-term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	4,295	5,992
Gross Unrealized Gains	0	0
Estimated Fair Value	$ 4,295	5,992
Government Debt Securities [Member] | Short-term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		1,509
Gross Unrealized Gains		0
Gross Unrealized Losses		(2)
Estimated Fair Value		$ 1,507

Marketable Securities - Additio

Marketable Securities - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Government Debt Securities [Member] | Minimum [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable securities contractual maturities	1 year
Government Debt Securities [Member] | Maximum [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable securities contractual maturities		2 years
Corporate Debt Securities [Member] | Minimum [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable securities contractual maturities	1 year
Corporate Debt Securities [Member] | Maximum [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable securities contractual maturities		2 years
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable investments continuous unrealized loss position	$ 0	$ 0
Commercial Paper [Member] | Minimum [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable securities contractual maturities	1 year
Commercial Paper [Member] | Maximum [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable securities contractual maturities		2 years
Asset-backed Securities [Member] | Minimum [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable securities contractual maturities	2 years
Asset-backed Securities [Member] | Maximum [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable securities contractual maturities		5 years

Certain Balance Sheet Items - P

Certain Balance Sheet Items - Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 363	$ 321
Less accumulated depreciation and amortization	(286)	(257)
Property and equipment, net	77	64
Office and Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	177	176
Purchased Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	83	46
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	38	33
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 65	$ 66

Certain Balance Sheet Items - A

Certain Balance Sheet Items - Accrued Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Accrued compensation	$ 1,839	$ 1,010
Accrued pre-clinical and clinical trial expenses	1,623	2,015
Accrued professional fees	982	283
Other accruals	57	28
Total accrued liabilities	$ 4,501	$ 3,336

Collaboration and License Agr40

Collaboration and License Agreements - Additional Information (Detail)	1 Months Ended	12 Months Ended
	Jun. 30, 1998USD ($)	Dec. 31, 2016USD ($)Agreement	Dec. 31, 2015USD ($)
Kowa Pharmaceuticals America Inc [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Non-refundable up-front payment		$ 5,000,000
Kowa Pharmaceuticals America Inc [Member] | Initiation or Achievement [Member] | Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payments		$ 200,000,000
Janssen Pharmaceutical NV [Member] | Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of royalty on net sales		8.00%
Janssen Pharmaceuticals, Inc. [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
License agreement date		Jun. 30, 2010
Number of development and license agreements | Agreement		2
DiaTex, Inc. [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
License agreement date		Jun. 30, 1998
Monthly license fees	$ 2,000
Potential future development payments	$ 800,000
Development payment		$ 0	$ 0
Royalty payment		$ 0	$ 0

Facility Loans - Additional Inf

Facility Loans - Additional Information (Detail) - USD ($)	Aug. 07, 2015	Sep. 30, 2013	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2013	Mar. 31, 2016
Debt Instrument [Line Items]
Facility loan, drawn				$ 9,482,000
Issued warrants to purchase common stock			114,436
Exercise price of common stock			$ 2.84
Warrant term			10 years
Warrants [Member]
Debt Instrument [Line Items]
Fair value of warrant liabilities		$ 300,000
Warrants, Exercise Price of $5.00 Per Share [Member]
Debt Instrument [Line Items]
Issued warrants to purchase common stock		121,739
Exercise price of common stock		$ 5
Warrant term					7 years
Second Tranche [Member]
Debt Instrument [Line Items]
Facility loan, unused amount expired						$ 5,000,000
2013 Term Loan Facility [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity		$ 10,000,000
Facility loan, interest amortization period		36 months
Facility loan, final interest payment		$ 300,000
Retiring of existing debt	$ 4,100,000
2013 Term Loan Facility [Member] | First Tranche [Member]
Debt Instrument [Line Items]
Facility loan, drawn		$ 5,000,000
Facility loan, fixed interest rate		8.75%
2013 Term Loan Facility [Member] | Second Tranche [Member]
Debt Instrument [Line Items]
Facility loan available for draw down		$ 5,000,000
2015 Term Loan Facility [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 15,000,000
Debt instrument payment terms			Under the first tranche, the Company is required to make 12 monthly interest only payments after the funding date followed by a repayment schedule equal to 36 equal monthly payments of interest and principal.
Percentage of principal amount as final payment	6.50%
Facility fee	1.00%
2015 Term Loan Facility [Member] | Minimum [Member]
Debt Instrument [Line Items]
Upfront payment	$ 35,000,000
Present value of the future cash flows	10.00%
2015 Term Loan Facility [Member] | First Tranche [Member]
Debt Instrument [Line Items]
Facility loan, drawn	$ 10,000,000
Facility loan, fixed interest rate	8.77%
2015 Term Loan Facility [Member] | First Tranche [Member] | Minimum [Member]
Debt Instrument [Line Items]
Facility loan, fixed interest rate	8.75%
2015 Term Loan Facility [Member] | First Tranche [Member] | Wall Street Journal Prime Rate [Member] | Minimum [Member]
Debt Instrument [Line Items]
Facility loan, fixed interest rate	8.47%
2015 Term Loan Facility [Member] | Second Tranche [Member]
Debt Instrument [Line Items]
Facility loan available for draw down	$ 5,000,000

Facility Loans - Schedule of Te

Facility Loans - Schedule of Term Loan Facility, Debt Discounts and Final Payment (Detail) - 2015 Term Loan Facility [Member] - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Line of Credit Facility [Line Items]
Principal payments due under the loan facility	$ 9,014	$ 10,000
Less: unamortized debt discount	(599)	(929)
Plus: accreted value of final payment	383	237
Term loan facility, net	$ 8,798	$ 9,308

Facility Loans - Schedule of Fu

Facility Loans - Schedule of Future Principal Payments Due under Loan Facility (Detail) $ in Thousands	Dec. 31, 2016USD ($)
Maturities of Long-term Debt [Abstract]
2,017	$ 3,137
2,018	3,423
2,019	2,454
Total future principal payments due under loan agreement	$ 9,014

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail)	Nov. 08, 2013ft²	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Loss Contingencies [Line Items]
Rent expenses		$ 300,000	$ 300,000
Accrued in the consolidated balance sheets related to indemnification obligations		0
Indemnification liabilities		$ 0	$ 0
Lease Facility [Member]
Loss Contingencies [Line Items]
Area of office space | ft²	8,894
Lease start date	Jan. 16, 2014
Lease expiration date	Dec. 31, 2018

Commitments and Contingencies45

Commitments and Contingencies - Future Minimum Lease Payments (Detail) $ in Thousands	Dec. 31, 2016USD ($)
Commitments and Contingencies Disclosure [Abstract]
2,017	$ 222
2,018	228
Total future minimum payments	$ 450

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - USD ($)	Jul. 27, 2015	Jul. 25, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2013	Nov. 07, 2014	Sep. 30, 2013
Class of Stock [Line Items]
Preferred stock, shares authorized			10,000,000	10,000,000
Common stock, shares authorized			100,000,000	100,000,000
Common stock shares sold		4,600,000
Common stock offering price	$ 2.81	$ 5.50
Net proceeds from public offering		$ 23,000,000
Registration filed on Form S-3						$ 100,000,000
Registration statement, event description			Entered into an at-the-market facility (ATM) to sell up to $25 million of common stock under the registration statement.
Registration statement, sale of common stock						$ 25,000,000
Net proceeds from public offering	$ 21,100,000			$ 4,300,000
Issued warrants to purchase common stock	8,200,000		23,447,003	23,447,003
Issued warrants to purchase common stock			114,436
Exercise price of common stock			$ 2.84
Warrant term			10 years
Change in fair value of warrant liability			$ (75,000)	$ (11,121,000)
Warrants, Exercise price of $5.75 per share [Member]
Class of Stock [Line Items]
Issued warrants to purchase common stock					1,741,788
Exercise price of common stock					$ 5.75
Warrant term					5 years
Warrants, Exercise Price of $5.00 Per Share [Member]
Class of Stock [Line Items]
Issued warrants to purchase common stock							121,739
Exercise price of common stock							$ 5
Warrant term					7 years
Warrants, Exercise Price of $2.84 Per Share [Member]
Class of Stock [Line Items]
Issued warrants to purchase common stock			114,436
Exercise price of common stock			$ 2.84
Warrant term					10 years
At the Market Facility [Member]
Class of Stock [Line Items]
Common stock shares sold				0

Stockholder's Equity - Reserved

Stockholder's Equity - Reserved Shares of Authorized but Unissued Common Stock (Detail) - shares	Dec. 31, 2016	Dec. 31, 2015
Class of Stock [Line Items]
Total reserved shares of common stock	5,123,651	3,951,819
Common Stock Warrants [Member]
Class of Stock [Line Items]
Total reserved shares of common stock	1,667,398	1,667,398
Equity Incentive Plans [Member]
Class of Stock [Line Items]
Total reserved shares of common stock	3,456,253	2,284,421

Stock Plans and Stock-Based C48

Stock Plans and Stock-Based Compensation - Additional Information (Detail) - USD ($)	Jan. 01, 2017	Jul. 31, 2016	Sep. 30, 2013	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2013	Dec. 31, 2007	Apr. 30, 2014	Jan. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of options vested				$ 2,200,000	$ 2,200,000
Share based compensation, stock option, unamortized expense				$ 3,500,000	$ 4,800,000
Share based compensation, stock option, unamortized expense vesting period				1 year 9 months 18 days	2 years 7 months 6 days
Number of option granted to employees				646,667,000	845,703,000
Clinical development expense recognized				$ 199,000
Share reserved for issue				5,123,651	3,951,819
Allocated share-based compensation expense				$ 2,473,000	$ 2,487,000
Options to purchase common stock				114,436
Performance Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of option granted to employees				327,000,000
Unrecognized stock based compensation				$ 192,000
Scientific Advisors and Consultants [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation arrangement by share based payment award, expiration period				10 years
Share based compensation arrangement by share based payment award, award vesting period				60 months
Allocated share-based compensation expense				$ 17,510	$ 21,265
Options to purchase common stock				18,000	10,000
Options to purchase common stock, unvested				28,410
Incentive award issued				2,335
Incentive awards outstanding, Unvested				584
Executives and Senior Officers [Member] | Performance Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of option granted to employees		327,000
2013 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation arrangement by share based payment award, expiration period			10 years
Share based compensation arrangement percentage increase in share reserved			5.00%
Shares available for grant				496,120
2013 Equity Incentive Plan [Member] | Subsequent Event [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Increased in shares available for issuance	1,172,350
2013 Equity Incentive Plan [Member] | Incentive Stock Options for Employees and Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation arrangement by share based payment award, exercise price percentage			100.00%
2013 Equity Incentive Plan [Member] | Nonqualified Options to Employees, Directors and Consultants [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation arrangement by share based payment award, exercise price percentage			85.00%
2013 Equity Incentive Plan [Member] | Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation arrangement by share based payment award, exercise price percentage			85.00%
Share based compensation arrangement by share based payment award, award vesting period			4 years
2013 Equity Incentive Plan [Member] | Stock Options to 10% Stockholders [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation arrangement by share based payment award, exercise price percentage							110.00%
Share based compensation arrangement by share based payment award, award vesting period							5 years
Incentive Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation arrangement by share based payment award, expiration period						10 years
Share reserved for issue						252,752		252,752	252,752
Exercisable weighted average price per share						$ 5.21		$ 5.21	$ 5.21
Stock option plan, Description				Vest monthly over four years effective from their grant date.
Allocated share-based compensation expense				$ 272,000	$ 323,000
Incentive Awards [Member] | First Tranche [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Incentive awards vested percentage						100.00%

Stock Plans and Stock-Based C49

Stock Plans and Stock-Based Compensation - Summary of Stock Option Activity (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Shares Subject to Outstanding Options
Outstanding at the beginning of period	1,804,083	991,010
Options granted	646,667	845,703
Options exercised	0	0
Options forfeited	14,319	15,631
Options expired	42,043	16,999
Outstanding as end of period	2,394,388	1,804,083	991,010
Vested and expected to vest	2,351,745
Exercisable	1,310,883
Weighted-Average Exercise Price of Options
Outstanding at the beginning of period	$ 7.41	$ 6.09
Options granted	1.28	9
Options exercised	0	0
Options forfeited	4.50	4.75
Options expired	25.01	12.31
Outstanding as end of period	5.46	$ 7.41	$ 6.09
Vested and expected to vest	5.50
Exercisable	$ 6.15
Weighted-Average Remaining Contractual Term (Years)
Outstanding	7 years 9 months	8 years 2 months 27 days	8 years 10 months 28 days
Vested and expected to vest	7 years 8 months 23 days
Exercisable	7 years 2 months 5 days
Aggregate Intrinsic Value (In Thousands)
Outstanding at the beginning of period			$ 4,559
Outstanding as end of period	$ 349
Vested and expected	331
Exercisable	$ 3
Performance Option [Member]
Shares Subject to Outstanding Options
Options granted	327,000
Options exercised	0
Outstanding as end of period	327,000
Weighted-Average Exercise Price of Options
Options granted	$ 1.82
Outstanding as end of period	$ 1.82

Stock Plans and Stock-Based C50

Stock Plans and Stock-Based Compensation - Summary of Stock-Based Compensation Expense, Net of Estimated Forfeitures (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 2,473	$ 2,487
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	995	844
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 1,478	$ 1,643

Stock Plans and Stock-Based C51

Stock Plans and Stock-Based Compensation - Estimated Weighted-Average Grant Date Fair Value (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term	6 years 1 month 6 days	6 years 1 month 6 days
Expected volatility	80.00%	78.00%
Risk-free interest rate	1.57%	1.65%
Expected dividend yield	0.00%	0.00%
Weighted-average grant date fair value per share	$ 0.89	$ 6.13
Performance Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term	5 years 1 month 6 days	0 years
Expected volatility	85.00%
Risk-free interest rate	1.56%
Expected dividend yield	0.00%	0.00%
Weighted-average grant date fair value per share	$ 1.20

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Income Tax [Line Items]
Provision for income taxes	$ 0	$ 0
Net valuation allowance change	$ 9,700,000	$ 9,800,000
Cumulative change in ownership	50.00%
Cumulative change in ownership period	3 years
Significant change to its unrecognized tax benefits over the next twelve months	$ 0
Income tax examination years	The tax years 1998 through 2016 remain open to examination by the major taxing authorities.
Domestic Tax Authority [Member]
Income Tax [Line Items]
Net operating loss carryforward	$ 229,100,000
Research and development tax credit carry forwards	$ 7,700,000
Domestic Tax Authority [Member] | Minimum [Member]
Income Tax [Line Items]
NOL carry forward expiry date	2,024
Domestic Tax Authority [Member] | Maximum [Member]
Income Tax [Line Items]
NOL carry forward expiry date	2,036
State and Local Jurisdiction [Member]
Income Tax [Line Items]
Net operating loss carryforward	$ 175,100,000
Research and development tax credit carry forwards	$ 6,300,000
State and Local Jurisdiction [Member] | Minimum [Member]
Income Tax [Line Items]
NOL carry forward expiry date	2,017
State and Local Jurisdiction [Member] | Maximum [Member]
Income Tax [Line Items]
NOL carry forward expiry date	2,036

Income Taxes - Components of De

Income Taxes - Components of Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets:
Federal and state net operating loss carryforwards	$ 88,111	$ 79,966
Capitalized research and development	22,272	22,287
Federal and state tax credit carryforwards	8,141	7,571
Stock based compensation	2,080	1,384
Other	974	628
Total deferred tax assets	121,578	111,836
Valuation allowance	(121,578)	(111,836)
Net deferred tax assets	$ 0	$ 0

Income Taxes - Summary of Recon

Income Taxes - Summary of Reconciliation of Expected Statutory Federal Income Tax Provision to Actual Income Tax Provision (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Expected income tax benefit at federal statutory tax rate	$ (9,068)	$ (5,280)
Change in valuation allowance	9,775	9,815
State income taxes, net of federal benefit	(458)	(618)
Permanent items	196	(3,542)
Research credits	(445)	(375)
Income tax (benefit) expense	$ 0	$ 0

Income Taxes - Summary of Gross

Income Taxes - Summary of Gross Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Balance at beginning of period	$ 2,127	$ 1,991
Increases related to prior year tax positions	0	0
Increases related to tax positions	159	136
Balance at end of period	$ 2,286	$ 2,127

Related-Party Transactions - Ad

Related-Party Transactions - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Former Member of Board of Directors [Member]
Related Party Transaction [Line Items]
Advisory fee paid to related party	$ 60,000	$ 60,000

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) - USD ($)	Feb. 02, 2017	Jan. 01, 2017	Jul. 27, 2015	Jan. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Nov. 07, 2014	Jul. 25, 2014
Subsequent Event [Line Items]
Options to purchase common stock					114,436
Registration statement, sale of common stock							$ 25,000,000
Proceeds from sale of common stock			$ 21,100,000			$ 4,300,000
Registration statement, event description					Entered into an at-the-market facility (ATM) to sell up to $25 million of common stock under the registration statement.
Proceeds from sale of common stock			8,200,000		23,447,003	23,447,003
Common sock offering price			$ 2.81					$ 5.50
Subsequent Event [Member]
Subsequent Event [Line Items]
Registration statement, sale of common stock				$ 124,100
Proceeds from sale of common stock	$ 9,200,000
Registration statement, event description				The Company utilized its ATM facility to offer and sell 124,100 shares of common stock for net proceeds of $158,000 as permitted under the Company's shelf registration statement
Proceeds from sale of common stock	5,200,000
Common sock offering price	$ 1.93
Subsequent Event [Member] | At the Market Facility [Member]
Subsequent Event [Line Items]
Proceeds from sale of common stock				$ 158,000
Subsequent Event [Member] | Employees And Consultants [Member]
Subsequent Event [Line Items]
Options to purchase common stock		1,016,301
Subsequent Event [Member] | 2013 Equity Incentive Plan [Member]
Subsequent Event [Line Items]
Number of shares automatically increased in share reserves		1,172,350