Cymabay Therapeutics (CBAY) 10-K 29 Mar 16 2015 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2015	Mar. 01, 2016	Jun. 30, 2015
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2015
Document Fiscal Year Focus	2,015
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		23,447,003
Entity Public Float			$ 40,789,823

Condensed Balance Sheets

Condensed Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 7,706	$ 11,586
Marketable securities	33,774	23,209
Contract receivables		211
Accrued interest receivable	186	136
Prepaid expenses	1,128	1,991
Other current assets		96
Total current assets	42,794	37,229
Property and equipment, net	64	86
Other assets	221	159
Total assets	43,079	37,474
Current liabilities:
Accounts payable	1,008	2,085
Accrued liabilities	3,336	3,388
Warrant liability	1,220	13,596
Facility loan	509	1,355
Accrued interest payable	73	35
Total current liabilities	6,146	20,459
Facility loan, less current portion	8,799	3,152
Other liabilities	19	13
Total liabilities	$ 14,964	$ 23,624
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 14,696,108 shares issued and outstanding as of December 31, 2015 and December 31, 2014, respectively	$ 2	$ 1
Additional paid-in capital	424,422	394,622
Accumulated other comprehensive loss	(21)	(14)
Accumulated deficit	(396,288)	(380,759)
Total stockholders' equity	28,115	13,850
Total liabilities and stockholders' equity	$ 43,079	$ 37,474

Condensed Balance Sheets (Paren

Condensed Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2015	Dec. 31, 2014
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	14,696,108
Common stock, shares outstanding	23,447,003	14,696,108

Statements of Operations and Co

Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Operating expenses:
Research and development	$ 17,026	$ 15,823
General and administrative	8,871	8,185
Total operating expenses	25,897	24,008
Loss from operations	(25,897)	(24,008)
Other income (expense):
Interest income	160	74
Interest expense	(913)	(755)
Other income (expense), net	11,121	(7,228)
Net loss	(15,529)	(31,917)
Net loss	(15,529)	(31,917)
Other comprehensive loss:
Unrealized loss on marketable securities	(7)	(16)
Other comprehensive loss	(7)	(16)
Comprehensive loss	$ (15,536)	$ (31,933)
Basic net loss per common share	$ (0.82)	$ (2.65)
Diluted net loss per common share	$ (0.83)	$ (2.65)
Weighted average common shares outstanding used to calculate basic net loss per common share	18,900,473	12,048,985
Weighted average common shares outstanding used to calculate diluted net loss per common share	18,917,213	12,048,985

Statements of Stockholders' Equ

Statements of Stockholders' 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, 2013	$ 18,596	$ 1	$ 367,435	$ 2	$ (348,842)
Balance at beginning of period (in shares) at Dec. 31, 2013		9,455,064
Issuance of common stock upon exercise of warrants, value	595		595
Issuance of common stock upon exercise of warrants (Shares)		36,613
Issuance of common stock upon exercise of options, value	4		4
Issuance of common stock upon exercise of options (in shares)		431
Non-employee stock-based compensation expense	8		8
Employee and director stock-based compensation expense	1,173		1,173
Conversion of incentive award from liability to equity accounting	121		121
Issuance of common stock, value	25,286		25,286
Issuance of common stock, (in shares)		5,204,000
Net loss	(31,917)				(31,917)
Net unrealized loss on marketable securities	(16)			(16)
Balance at end of period at Dec. 31, 2014	13,850	$ 1	394,622	(14)	(380,759)
Balance at end 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
Issuance of common stock upon exercise of options (in shares)	0
Non-employee stock-based compensation expense	$ 21		21
Employee and director stock-based compensation expense	2,466		2,466
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 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

Statements of Stockholders' Eq6

Statements of Stockholders' Equity (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Statement of Stockholders' Equity [Abstract]
Stock issuance cost	$ 2,028	$ 3,034

Statements of Cash Flows

Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Operating activities
Net loss	$ (15,529)	$ (31,917)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	22	18
Non-employee stock-based compensation expense	21	8
Employee and director stock-based compensation expense	2,466	1,284
Amortization of premium on marketable securities	511	453
Non-cash interest associated with debt discount accretion	228	198
Change in fair value of warrant liability	(11,121)	7,236
Loss on sale of property and equipment		2
Changes in assets and liabilities:
Contract receivables	211	(101)
Accrued interest receivable	(50)	(68)
Prepaid expenses	863	(1,627)
Other assets	34	3
Accounts payable	(1,077)	1,388
Accrued liabilities	(52)	1,889
Accrued interest payable	143	107
Other liabilities	6	13
Net cash used in operating activities	(23,324)	(21,114)
Investing activities
Purchases of property and equipment		(103)
Purchases of marketable securities	(42,788)	(27,334)
Proceeds from sales and maturities of marketable securities	31,705	10,499
Net cash used in investing activities	(11,083)	(16,938)
Financing activities
Proceeds from facility loan	9,482
Repayment of facility loan principal	(4,756)	(244)
Proceeds from issuance of common stock and warrants, net of issuance costs	25,375	25,430
Proceeds from issuance of common stock upon exercise of warrants	426	46
Proceeds from issuance of common stock upon exercise of stock options		5
Net cash provided by financing activities	30,527	25,237
Net decrease in cash and cash equivalents	(3,880)	(12,815)
Cash and cash equivalents at beginning of period	11,586	24,401
Cash and cash equivalents at end of period	7,706	11,586
Supplemental disclosure of cash flow information
Cash paid for interest	535	435
Issuance of common stock warrants to lenders	258	443
Issuance of common stock upon warrant exercises	$ 1,513	549
Noncash issuance costs incurred in common stock financing		453
Reclassification of incentive awards to equity		$ 121

Organization and Description of

Organization and Description of Business	12 Months Ended
	Dec. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Description of Business	1. Organization and Description of Business CymaBay Therapeutics, Inc. (The Company) is focused on developing therapies to treat metabolic diseases with high unmet medical need, including serious rare and orphan disorders. The Company’s two key clinical development candidates are MBX-8025 and arhalofenate. MBX-8025 is currently being developed for the treatment of various orphan lipid and liver diseases. Arhalofenate is being developed for the treatment of gout. The Company is an emerging growth company. Under the JOBS Act emerging growth companies can delay adopting new or revised accounting standards until such time of those standards apply to private companies. The Company has adopted this exemption from new or revised accounting standards, and therefore, it may not be 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, 2015, the Company incurred a net loss of $15.5 million and used $23.3 million of cash in operations. At December 31, 2015, the Company had an accumulated deficit of $396.3 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, 2015, the Company’s cash, cash equivalents and marketable securities totaled $41.5 million. These funds 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 timing of initiation of planned clinical trials, including phase 2 trials to study the therapeutic benefits of MBX-8025 on patients with certain orphan diseases as well as a phase 3 clinical trial to study the therapeutic benefits of arhalofenate on patients with gout. The Company will therefore continue to require additional financing to develop its products and fund future operating losses and will seek funds through equity financings, debt, collaborative or other arrangements with corporate sources, or through other sources of financing. It is unclear if or when any such financing 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 to close its business which could have an adverse impact on its ability to achieve its business objectives.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2015
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 trial 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. Fair Value of Financial Instruments The Company’s financial instruments consist of cash and cash equivalents, marketable securities, accounts payable, accrued expenses 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 and therefore cannot be determined with precision. The carrying amounts of cash and cash equivalents, accounts payable and accrued expenses are generally considered to be representative of their respective fair values because of the short-term nature of those instruments. Based on prevailing borrowing rates available to the Company for loans with similar terms, the Company believes that the fair value of long-term debt 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 using the above input categories (in thousands): (In thousands) As of December 31, 2015 Description Level 1 Level 2 Level 3 Fair Value Money market funds $ 6,942 $ — $ — $ 6,942 Corporate debt and asset backed securities — 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 (In thousands) As of December 31, 2014 Description Level 1 Level 2 Level 3 Fair Value Money market funds $ 9,941 $ — $ — $ 9,941 Corporate debt and asset backed securities — 23,209 — 23,209 Total assets measured at fair value $ 9,941 $ 23,209 $ — $ 33,150 Warrant liability $ — $ — $ 13,596 $ 13,596 Total liabilities measured at fair value $ — $ — $ 13,596 $ 13,596 Marketable securities consist of available-for-sale securities that are reported at fair value, with the related unrealized gains and losses included in accumulated other comprehensive income (loss), a component of stockholders’ equity. The Company values cash equivalents and marketable securities using quoted market prices or alternative pricing sources and models utilizing observable market inputs and, as such, classifies cash equivalents and marketable securities within Level 1 or Level 2. As of December 31, 2015 and 2014, the Company held a Level 3 liability associated with warrants, issued in connection with the Company’s financings completed in September and October 2013, January 2014, and August 2015. The warrants are considered liabilities and are valued using a binomial 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, and the expected changes in stock price that follow announcements of the Company’s clinical trial results and other 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 Level 3 financial instruments (in thousands): Warrant Forward Balance as of December 31, 2013 $ 6,466 $ 453 Issuance of financial instrument 443 — Change in fair value 7,236 (10 ) Settlement of financial instrument (549 ) (443 ) Balance as of December 31, 2014 $ 13,596 $ — Warrant Forward Balance as of December 31, 2014 $ 13,596 $ — Issuance of financial instrument 258 — Change in fair value (11,121 ) — Settlement of financial instrument (1,513 ) — Balance as of December 31, 2015 $ 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 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 sheet. 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, 2015 and 2014, cash restricted under these arrangements was $170,000 and $100,000, respectively. 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. 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, 2015. 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. 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 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. Research and development expenses under collaboration agreements approximate the revenue recognized under such agreements. The expenses related to clinical trials are based upon estimates of the services received and efforts expended pursuant to contracts with research institutions and clinical research organizations (CROs) that conduct and manage clinical trials on behalf of the Company. The Company’s objective is to reflect the appropriate trial expenses in its financial statements by matching those expenses with the period in which services and efforts are incurred. Expenses related to clinical trials are accrued based upon the level of activity incurred under each contract as indicated by such factors as progress made against specified milestones or targets in each period, patient enrollment levels, and other trial activities as reported by CROs. Accordingly, the Company’s clinical trial accrual is dependent upon the timely and accurate reporting of expenses by clinical research organizations and other third-party vendors. Payments made to third parties under these clinical trial arrangements in advance of the receipt of the related services are recorded as prepaid assets, depending on the terms of the agreement, until the services are rendered. We base our estimates on the best information available at the time. However, additional information may become available to us which may allow us to make a more accurate estimate in future periods. In this event, we may be required to record adjustments to research and development expenses in future periods when the actual level of activity becomes more certain. Such increases or decreases in cost are generally considered to be changes in estimates and will be reflected in research and development expenses in the period first identified. Stock-Based Compensation Employee and director stock-based compensation is measured at the grant date, based on the fair-value-based measurements of the stock awards, and the portion that is ultimately expected to vest is recognized as an expense over the related vesting periods, net of estimated forfeitures. The Company calculates the fair-value-based measurements of options using the Black-Scholes valuation model and recognizes expense using the straight-line attribution method. The determination of fair value for stock-based awards on the date of grant using an option-pricing model requires management to make certain assumptions regarding subjective variables. Equity awards granted to non-employees are accounted for on the grant date using the Black-Scholes valuation model to determine the fair value-based measurements of such instruments. The fair value-based measurements of options and warrants granted to non-employees are re-measured over the related vesting period and amortized to expense as earned. Common Stock Warrants 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 as they contain provisions that could require the Company to settle the warrants in cash. The warrants were recorded at fair value using either the Black-Scholes option pricing model, or a probability weighted expected return model or a binomial model, depending on the characteristics of the warrants. The fair value of these warrants is re-measured at each financial reporting period with any changes in fair value recognized as a component of other income (expense) in the accompanying statements of operations and comprehensive loss until such time as the warrants are no longer outstanding. 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 we establish or reduce the valuation allowance related to the deferred tax assets, our 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 taxes, if any, as interest, 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 taxes recorded during the years ended December 31, 2015 and 2014. 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 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 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 warrants for the period. Likewise, corresponding 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 earnings (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, 2015 2014 Numerator: Net loss allocated to common stock—basic $ (15,529 ) $ (31,917 ) Adjustment for revaluation of warrants (94 ) — Net loss allocated to common stock—diluted $ (15,623 ) $ (31,917 ) Denominator: Weighted average number of common stock shares outstanding—basic 18,900,473 12,048,985 Dilutive common stock warrants 16,740 — Weighted average number of common stock shares outstanding—diluted 18,917,213 12,048,985 Net loss per share—basic $ (0.82 ) $ (2.65 ) Net loss per share—diluted $ (0.83 ) $ (2.65 ) 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 2015 2014 Common stock warrants 1,553 1,768 Common stock options 1,804 991 Incentive awards 245 247 3,602 3,006 Recent Accounting Pronouncements 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 standard is effective for annual periods ending after December 15, 2016, and interim periods therein. The Company does not expect that the adoption of this standard will have a significant impact on its financial statements. 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. This ASU will be effective for the Company in fiscal year 2016. The Company does not expect that the adoption of this standard will have a significant impact on its financial statements. Accounting Standards Update 2015-17 In November 2015, the FASB issued ASU No. 2015-17, Income Taxes (Subtopic 740): Balance Sheet Classification of Deferred Taxes, The ASU requires entities to classify deferred tax liabilities and assets as noncurrent in a classified statement of financial position. The standard is effective for annual periods ending after December 15, 2016, and interim periods therein with early adoption permitted. The Company elected to early adopt this accounting standard for the year ended December 31, 2015 on a prospective basis and its adoption did not have a significant 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 ASU requires management to recognize lease assets and lease liabilities by lessees for all operating leases. The ASU is effective for periods ending on December 15, 2018 and interim periods therein on a modified retrospective basis. The Company is currently evaluating the impact this guidance will have on our financial statements.

Marketable Securities

Marketable Securities	12 Months Ended
	Dec. 31, 2015
Cash and Cash Equivalents [Abstract]
Marketable Securities	3. Marketable Securities Marketable available-for-sale securities as of December 31, 2015 and 2014 consist of the following (in thousands): Amortized Gross Gross Estimated As of December 31, 2015: Government debt securities $ 1,509 $ — $ (2 ) $ 1,507 Corporate debt securities 27,663 — $ (17 ) 27,646 Asset-backed securities 4,623 — (2 ) 4,621 $ 33,795 $ — $ (21 ) $ 33,774 Amortized Gross Gross Estimated As of December 31, 2014: Corporate debt securities $ 19,706 $ 1 $ (14 ) $ 19,693 Asset-backed securities 3,516 — — 3,516 $ 23,222 $ 1 $ (14 ) $ 23,209 As of December 31, 2015 and 2014, the Company’s government and corporate debt marketable securities had contractual maturities of less than one year and asset-backed securities had contractual maturities between 2-5 years. Realized gains and losses were immaterial for the years ended December 31, 2015 and 2014. None of these investments have been in a continuous unrealized loss position for more than 12 months as of December 31, 2015 and 2014.

Certain Balance Sheet Items

Certain Balance Sheet Items	12 Months Ended
	Dec. 31, 2015
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 $ 176 $ 176 Purchased software 46 46 Furniture and fixtures 33 33 Leasehold improvements 66 66 Total 321 321 Less accumulated depreciation and amortization (257 ) (235 ) Property and equipment, net $ 64 $ 86 Accrued liabilities consist of the following (in thousands): December 31, December 31, Accrued compensation $ 1,010 $ 1,504 Accrued pre-clinical and clinical trial expenses 2,015 1,732 Accrued professional fees 283 73 Other accruals 28 79 Total accrued liabilities $ 3,336 $ 3,388

Collaboration and License Agree

Collaboration and License Agreements	12 Months Ended
	Dec. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Collaboration and License Agreements	5. Collaboration and License Agreements In June 2006, the Company entered into an exclusive worldwide, royalty-bearing license to MBX-8025 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 is also eligible to receive up to $228 million in contingent payments if certain development and commercial events are achieved as well as royalties on worldwide net sales of products. No such payments have been made to date. Under the terms of the agreements, Janssen has full control and responsibility over the research, development and registration of any products developed and/or discovered from the metabolic disease targets and is required to use diligent efforts to conduct all such activities. The Company received a termination notice from Janssen, effectively ending these development and licensing agreements in early April 2015. In December 2015, CymaBay exercised an option pursuant to the terms of one of the original agreements to continue to work to research, develop and commercialize compounds with activity against an undisclosed metabolic disease target. Janssen granted CymaBay an exclusive, worldwide license (with rights to sublicense) under the Janssen know-how and patents to research, develop, make, have made, import, use, offer for sale and sell such compounds. CymaBay 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. 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. Pursuant to the license agreement, all of the Company’s patents and patent applications related to arhalofenate, its use, and production are jointly owned with DiaTex. DiaTex is entitled to up to $0.8 million for the future development of arhalofenate, as well as royalty payments on any sales of products containing arhalofenate. No development payments were made in the years ended December 31, 2015 and 2014 and no royalties have been paid to date.

Debt

Debt	12 Months Ended
	Dec. 31, 2015
Debt Disclosure [Abstract]
Debt	6. Debt 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. Loans under the second tranche incurred interest at a rate fixed at the time of borrowing equal to the greater of (i) 8.75% per annum and (ii) the sum of the Wall Street Journal prime rate plus 4.25% per annum. 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, will be 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. As of December 31, 2015, the Company has not drawn down on the second tranche. 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. If drawn, the second tranche will bear interest using the same rate formula as the first tranche and will amortize pursuant to a repayment schedule that is coterminous with the amortization period of the first tranche. Upon maturity of each tranche, the remaining balance of such tranche and a final payment equal to 6.50% of the original principal amount advanced of the applicable tranche are payable. The Company is permitted to make voluntary prepayments of the term loans with a prepayment fee equal to 3% of the principal amount of any term loans prepaid. The Company is required to make mandatory prepayments of the outstanding term loans upon the acceleration by the lenders of such loans following the occurrence of an event of default, along with a payment of the final payment, the prepayment fee and any all other obligations that are due and payable at the time of the prepayment. The Company’s obligations under the 2015 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 its intellectual property. The Company also entered into a negative pledge agreement with the lenders pursuant to which it has agreed not to encumber any of its intellectual property. The 2015 Term Loan Facility contains customary representations and warranties and customary affirmative and negative covenants applicable to the Company, including, among other things, restrictions on dispositions, changes in business, management, ownership or business locations, mergers or acquisitions, indebtedness, encumbrances, distributions, investments, transactions with affiliates and subordinated debt. The 2015 Term Loan Facility also includes customary events of default, including but not limited to the nonpayment of principal or interest, violations of covenants, material adverse change, attachment, levy, restraint on business, bankruptcy, material judgments and misrepresentations. Upon an event of default, the lenders may, among other things, accelerate the loans and foreclose on the collateral. As of December 31, 2015, the Company was in compliance with the terms of the term loan covenants and there were no identified events of default. 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 will be revalued at each balance sheet date until the warrants are exercised or expire. The term loan facility, debt discounts and final payment balances as of December 31, 2015 and 2014 are as follows: December 31, 2015 2014 Principal payments due under the loan facility $ 10,000 $ 4,755 Less: unamortized debt discount (929 ) (380 ) Plus: accreted value of final payment 237 132 Term loan facility, net $ 9,308 $ 4,507 Future principal payments due under the loan facility are as follows (in thousands): Principal Year ending December 31: 2016 $ 986 2017 3,137 2018 3,423 2019 2,454 Total future principal payments due under loan agreement $ 10,000

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	7. Commitments and Contingencies Operating Lease Commitments Rent expense was $0.3 million and $0.4 million for the years ended December 31, 2015 and 2014. 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: 2016 $ 216 2017 222 2018 228 Total future minimum payments $ 666 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, 2015 and 2014. 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.

Preferred Stock

Preferred Stock	12 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Preferred Stock	8. Preferred Stock The Company is authorized to issue 10,000,000 shares of preferred stock as of December 31, 2015 and 2014, respectively.

Common Stock

Common Stock	12 Months Ended
	Dec. 31, 2015
Text Block [Abstract]
Common Stock	9. Common Stock The Company is authorized to issue 100,000,000 shares of common stock as of December 31, 2015 and 2014, respectively. Common Stock Issuances On July 25, 2014, the Company completed a public offering of 4,600,000 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 8,188,000 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 CymaBay’s common stock at an exercise price of $5.75 per share which the Company refers to here as the 2013 financing warrants. The Company also issued seven-year warrants to purchase 121,739 shares of CymaBay’s common stock to its lenders at an exercise price of $5.00 per share in September 2013. In August 2015, the Company issued ten-year warrants to purchase 114,436 shares of CymaBay’s common stock to its lenders at an exercise price of $2.84 per share. The 2013 financing warrants contain provisions that are contingent on the occurrence of a change in control, which would conditionally obligate the Company to repurchase the warrants for cash in an amount equal to their fair value using the Black-Scholes Option Pricing Model (the “Black-Scholes Model”) on the date of such change in control. Due to these provisions, the Company is required to account for the 2013 financing warrants issued in September 2013, October 2013 and January 2014 and all the lender warrants as a liability 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, 2015 and 2014 using a binomial lattice model. The resulting decrease in fair value of $11.1 million for the year ended December 31, 2015 was recorded as a revaluation gain and the increase in fair value of $7.2 million for the year ended December 31, 2014 was recorded as a revaluation loss 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, 2015 and December 31, 2014, the Company had reserved shares of authorized but unissued common stock as follows: December 31, December 31, Common stock warrants 1,667,398 1,768,347 Equity incentive plans 2,284,421 1,549,616 Total reserved shares of common stock 3,951,819 3,317,963

Stock Plans and Stock-Based Com

Stock Plans and Stock-Based Compensation	12 Months Ended
	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock Plans and Stock-Based Compensation	10. 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 options, stock bonuses, and restricted stock awards by the Company. These awards may be granted to employees, members of the Board of Directors, and consultants to the Company. 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- or five-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, 2015, there were 235,367 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, 2016. The following table summarizes stock option activity: Shares Weighted- Weighted- Aggregate Outstanding as of December 31, 2014 991,010 $ 6.09 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 $ — Vested and expected to vest as of December 31, 2015 1,757,991 $ 7.38 8.22 $ — Exercisable as of December 31, 2015 783,856 $ 6.28 7.81 $ — The following table summarizes information about stock options outstanding as of December 31, 2015: Options Outstanding Options Exercisable Exercise Price Number of Shares Weighted- Number of Shares $1.98 – $4.77 108,483 8.95 65,800 $5.00 858,442 7.57 617,070 $5.23 10,000 8.65 3,333 $5.90 18,000 9.29 18,000 $6.85 12,000 8.73 4,500 $7.00 77,000 8.28 32,083 $7.99 6,500 8.36 2,594 $10.00 – $10.49 710,203 8.93 37,021 $238.50 3,455 0.73 3,455 1,804,083 8.24 783,856 Grant Date Fair Value The following table presents the weighted-average assumptions the Company used in the Black-Scholes valuation model to derive the grant date fair value-based measurements of employee and director stock options and the resulting estimated weighted-average grant date fair-value-based measurements per share: Year Ended December 31, 2015 2014 Weighted-average assumptions: Expected term 6.1 yrs 6.0 yrs Expected volatility 78 % 90 % Risk-free interest rate 1.65 % 2.02 % Expected dividend yield 0 % 0 % Weighted-average grant date fair value per share $ 6.13 $ 4.06 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, 2015 and 2014, 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, 2015 and 2014. Vested and Unvested Awards The total fair value of options vested for the years ended December 31, 2015 and 2014, was $2.2 million and $1.0 million, respectively. As of December 31, 2015, and 2014 the total compensation expense related to unvested employee stock options to be recognized in future periods, excluding estimated forfeitures, was $4.8 million and $1.9 million, respectively. The weighted-average periods over which this compensation expense is expected to be recognized are 2.6 years and 3.0 years as of December 31, 2015 and 2014, respectively. 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 incentive award is a stock based compensation arrangement. From the grant date of each award through June 3, 2014, the Company did not have sufficient shares available for issuance to settle the incentive awards in stock. Since during this period settlement in cash was deemed more likely, the Company accounted for these cash settled awards as a liability to be remeasured at fair value at each reporting date until settled. Through June 3, 2014, compensation expense and the related incentive award liability were recognized over the initial two year vesting period of the incentive awards. On June 3, 2014, once sufficient shares became available to settle the incentive awards in stock, this settlement method was deemed more likely and accordingly, the Company began to account for the incentives awards using the equity accounting method. Specifically, on June 3, 2014, the Company revalued the incentive award liability at fair value, adjusted the expense recognition period to reflect the modified vesting term, and reclassified the resulting $121,000 incentive award liability balance to additional paid in capital. Subsequent to June 3, 2014, the Company recognized the fixed equity value of each incentive award over the remainder of its four year vest period. The Company recorded $323,000 and $285,000 of stock based compensation expense in the years ended December 31, 2015 and 2014, respectively pertaining to its incentive awards. Stock-Based Compensation Expense Employee and Director Expense Employee and director stock-based compensation expense recorded was as follows (in thousands): Year Ended 2015 2014 Research and development $ 823 $ 332 General and administrative 1,643 952 Total $ 2,466 $ 1,284 Non-Employee Expense 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 10,000 and 10,000 shares of common stock, in 2015 and 2014, respectively. As of December 31, 2015, options to purchase 18,945 shares of common stock remained unvested, and compensation related to these stock options is subject to periodic adjustment as the shares vest. In 2013, the Company also issued an incentive award for 2,335 shares to a scientific advisor, of which 1,167 shares remained unvested as of December 31, 2015. The Company recorded $21,000 and $8,000 of expense in the years ended December 31, 2015 and 2014, respectively, related to these options and awards.

401(k) Plan

401(k) Plan	12 Months Ended
	Dec. 31, 2015
Postemployment Benefits [Abstract]
401(k) Plan	11. 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, 2015 and 2014.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income Taxes	12. Income Taxes No provision for U.S. income taxes exists due to tax losses incurred in all periods presented. Deferred income taxes reflect the tax effects of net operating loss and tax credit carryforwards and the net temporary differences between the carrying amounts of assets and liabilities for financial reporting and the amounts used for income tax purposes. Significant components of the Company’s deferred tax assets are as follows (in thousands): December 31 2015 2014 Deferred tax assets: Federal and state net operating loss carryforwards $ 79,966 $ 71,153 Capitalized research and development 22,287 22,314 Federal and state tax credit carryforwards 7,571 7,083 Other 2,012 1,470 Total deferred tax assets 111,836 102,020 Valuation allowance (111,836 ) (102,020 ) 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 $9.8 million during the year ended December 31, 2015 and increased $11.2 million during the year ended December 31, 2014. The following is a reconciliation of the expected statutory federal income tax provision to the actual income tax provision (in thousands): December 31 2015 2014 Expected income tax benefit at federal statutory tax rate $ (5,280 ) $ (10,851 ) Net operating loss adjustments 1 (1,703 ) Change in valuation allowance 9,815 11,189 State income taxes, net of federal benefit (618 ) (783 ) Permanent items (3,543 ) 2,595 Research credits (375 ) (446 ) Other, net — (1 ) 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, 2015 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 2008-2015, 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, 2015, we had federal net operating loss carryforwards of $205.7 million and state net operating loss carryforwards of $172.0 million to offset future taxable income, if any. In addition, we had federal research and development tax credit carry forwards of $7.2 million and state research and development tax credit carryforwards of $3.5 million. If not utilized, the federal net operating loss and tax credit carryforwards will expire beginning in 2024 through 2035 and the state net operating loss carryforwards will expire beginning in 2016 through 2035. 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, 2013 $ 1,865 Increases related to prior year tax positions — Increases related to 2014 tax positions 126 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 The unrecognized tax benefits, if recognized, would not have an impact on the Company’s effective tax rate. 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 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 2015 remain open to examination by the major taxing authorities.

Related-Party Transactions

Related-Party Transactions	12 Months Ended
	Dec. 31, 2015
Related Party Transactions [Abstract]
Related-Party Transactions	13. 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, 2015 and 2014 in monthly cash retainers.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2015
Subsequent Events [Abstract]
Subsequent Events	14. Subsequent Events On January 1, 2016, the share reserve of the Company’s 2013 Equity Incentive Plan, or 2013 Plan, automatically increased by 1,172,350 shares.

Organization and Description 22

Organization and Description of Business (Policies)	12 Months Ended
	Dec. 31, 2015
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, 2015, the Company incurred a net loss of $15.5 million and used $23.3 million of cash in operations. At December 31, 2015, the Company had an accumulated deficit of $396.3 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, 2015, the Company’s cash, cash equivalents and marketable securities totaled $41.5 million. These funds 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 timing of initiation of planned clinical trials, including phase 2 trials to study the therapeutic benefits of MBX-8025 on patients with certain orphan diseases as well as a phase 3 clinical trial to study the therapeutic benefits of arhalofenate on patients with gout. The Company will therefore continue to require additional financing to develop its products and fund future operating losses and will seek funds through equity financings, debt, collaborative or other arrangements with corporate sources, or through other sources of financing. It is unclear if or when any such financing 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 to close its business which could have an adverse impact on its ability to achieve its business objectives.
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 trial 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.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The Company’s financial instruments consist of cash and cash equivalents, marketable securities, accounts payable, accrued expenses 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 and therefore cannot be determined with precision. The carrying amounts of cash and cash equivalents, accounts payable and accrued expenses are generally considered to be representative of their respective fair values because of the short-term nature of those instruments. Based on prevailing borrowing rates available to the Company for loans with similar terms, the Company believes that the fair value of long-term debt 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 using the above input categories (in thousands): (In thousands) As of December 31, 2015 Description Level 1 Level 2 Level 3 Fair Value Money market funds $ 6,942 $ — $ — $ 6,942 Corporate debt and asset backed securities — 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 (In thousands) As of December 31, 2014 Description Level 1 Level 2 Level 3 Fair Value Money market funds $ 9,941 $ — $ — $ 9,941 Corporate debt and asset backed securities — 23,209 — 23,209 Total assets measured at fair value $ 9,941 $ 23,209 $ — $ 33,150 Warrant liability $ — $ — $ 13,596 $ 13,596 Total liabilities measured at fair value $ — $ — $ 13,596 $ 13,596 Marketable securities consist of available-for-sale securities that are reported at fair value, with the related unrealized gains and losses included in accumulated other comprehensive income (loss), a component of stockholders’ equity. The Company values cash equivalents and marketable securities using quoted market prices or alternative pricing sources and models utilizing observable market inputs and, as such, classifies cash equivalents and marketable securities within Level 1 or Level 2. As of December 31, 2015 and 2014, the Company held a Level 3 liability associated with warrants, issued in connection with the Company’s financings completed in September and October 2013, January 2014, and August 2015. The warrants are considered liabilities and are valued using a binomial 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, and the expected changes in stock price that follow announcements of the Company’s clinical trial results and other 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 Level 3 financial instruments (in thousands): Warrant Forward Balance as of December 31, 2013 $ 6,466 $ 453 Issuance of financial instrument 443 — Change in fair value 7,236 (10 ) Settlement of financial instrument (549 ) (443 ) Balance as of December 31, 2014 $ 13,596 $ — Warrant Forward Balance as of December 31, 2014 $ 13,596 $ — Issuance of financial instrument 258 — Change in fair value (11,121 ) — Settlement of financial instrument (1,513 ) — Balance as of December 31, 2015 $ 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 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 sheet. 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, 2015 and 2014, cash restricted under these arrangements was $170,000 and $100,000, respectively. 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.
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, 2015.
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.
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 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. Research and development expenses under collaboration agreements approximate the revenue recognized under such agreements. The expenses related to clinical trials are based upon estimates of the services received and efforts expended pursuant to contracts with research institutions and clinical research organizations (CROs) that conduct and manage clinical trials on behalf of the Company. The Company’s objective is to reflect the appropriate trial expenses in its financial statements by matching those expenses with the period in which services and efforts are incurred. Expenses related to clinical trials are accrued based upon the level of activity incurred under each contract as indicated by such factors as progress made against specified milestones or targets in each period, patient enrollment levels, and other trial activities as reported by CROs. Accordingly, the Company’s clinical trial accrual is dependent upon the timely and accurate reporting of expenses by clinical research organizations and other third-party vendors. Payments made to third parties under these clinical trial arrangements in advance of the receipt of the related services are recorded as prepaid assets, depending on the terms of the agreement, until the services are rendered. We base our estimates on the best information available at the time. However, additional information may become available to us which may allow us to make a more accurate estimate in future periods. In this event, we may be required to record adjustments to research and development expenses in future periods when the actual level of activity becomes more certain. Such increases or decreases in cost are generally considered to be changes in estimates and will be reflected in research and development expenses in the period first identified.
Stock-Based Compensation	Stock-Based Compensation Employee and director stock-based compensation is measured at the grant date, based on the fair-value-based measurements of the stock awards, and the portion that is ultimately expected to vest is recognized as an expense over the related vesting periods, net of estimated forfeitures. The Company calculates the fair-value-based measurements of options using the Black-Scholes valuation model and recognizes expense using the straight-line attribution method. The determination of fair value for stock-based awards on the date of grant using an option-pricing model requires management to make certain assumptions regarding subjective variables. Equity awards granted to non-employees are accounted for on the grant date using the Black-Scholes valuation model to determine the fair value-based measurements of such instruments. The fair value-based measurements of options and warrants granted to non-employees are re-measured over the related vesting period and amortized to expense as earned.
Common Stock Warrants	Common Stock Warrants 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 as they contain provisions that could require the Company to settle the warrants in cash. The warrants were recorded at fair value using either the Black-Scholes option pricing model, or a probability weighted expected return model or a binomial model, depending on the characteristics of the warrants. The fair value of these warrants is re-measured at each financial reporting period with any changes in fair value recognized as a component of other income (expense) in the accompanying statements of operations and comprehensive loss until such time as the warrants are no longer outstanding.
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 we establish or reduce the valuation allowance related to the deferred tax assets, our 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 taxes, if any, as interest, 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 taxes recorded during the years ended December 31, 2015 and 2014.
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 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 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 warrants for the period. Likewise, corresponding 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 earnings (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, 2015 2014 Numerator: Net loss allocated to common stock—basic $ (15,529 ) $ (31,917 ) Adjustment for revaluation of warrants (94 ) — Net loss allocated to common stock—diluted $ (15,623 ) $ (31,917 ) Denominator: Weighted average number of common stock shares outstanding—basic 18,900,473 12,048,985 Dilutive common stock warrants 16,740 — Weighted average number of common stock shares outstanding—diluted 18,917,213 12,048,985 Net loss per share—basic $ (0.82 ) $ (2.65 ) Net loss per share—diluted $ (0.83 ) $ (2.65 ) 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 2015 2014 Common stock warrants 1,553 1,768 Common stock options 1,804 991 Incentive awards 245 247 3,602 3,006
Recent Accounting Pronouncements	Recent Accounting Pronouncements 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 standard is effective for annual periods ending after December 15, 2016, and interim periods therein. The Company does not expect that the adoption of this standard will have a significant impact on its financial statements. 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. This ASU will be effective for the Company in fiscal year 2016. The Company does not expect that the adoption of this standard will have a significant impact on its financial statements. Accounting Standards Update 2015-17 In November 2015, the FASB issued ASU No. 2015-17, Income Taxes (Subtopic 740): Balance Sheet Classification of Deferred Taxes, The ASU requires entities to classify deferred tax liabilities and assets as noncurrent in a classified statement of financial position. The standard is effective for annual periods ending after December 15, 2016, and interim periods therein with early adoption permitted. The Company elected to early adopt this accounting standard for the year ended December 31, 2015 on a prospective basis and its adoption did not have a significant 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 ASU requires management to recognize lease assets and lease liabilities by lessees for all operating leases. The ASU is effective for periods ending on December 15, 2018 and interim periods therein on a modified retrospective basis. The Company is currently evaluating the impact this guidance will have on our financial statements.

Summary of Significant Accoun23

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Schedule of Fair Value Assets and Liabilities Measured on Recurring Basis	The following tables present the fair value of the Company’s financial assets and liabilities using the above input categories (in thousands): (In thousands) As of December 31, 2015 Description Level 1 Level 2 Level 3 Fair Value Money market funds $ 6,942 $ — $ — $ 6,942 Corporate debt and asset backed securities — 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 (In thousands) As of December 31, 2014 Description Level 1 Level 2 Level 3 Fair Value Money market funds $ 9,941 $ — $ — $ 9,941 Corporate debt and asset backed securities — 23,209 — 23,209 Total assets measured at fair value $ 9,941 $ 23,209 $ — $ 33,150 Warrant liability $ — $ — $ 13,596 $ 13,596 Total liabilities measured at fair value $ — $ — $ 13,596 $ 13,596
Schedule of Changes in Fair Value of Financial Instruments	The following tables set forth a summary of the changes in the fair value of our Level 3 financial instruments (in thousands): Warrant Forward Balance as of December 31, 2013 $ 6,466 $ 453 Issuance of financial instrument 443 — Change in fair value 7,236 (10 ) Settlement of financial instrument (549 ) (443 ) Balance as of December 31, 2014 $ 13,596 $ — Warrant Forward Balance as of December 31, 2014 $ 13,596 $ — Issuance of financial instrument 258 — Change in fair value (11,121 ) — Settlement of financial instrument (1,513 ) — Balance as of December 31, 2015 $ 1,220 $ —
Schedule 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, 2015 2014 Numerator: Net loss allocated to common stock—basic $ (15,529 ) $ (31,917 ) Adjustment for revaluation of warrants (94 ) — Net loss allocated to common stock—diluted $ (15,623 ) $ (31,917 ) Denominator: Weighted average number of common stock shares outstanding—basic 18,900,473 12,048,985 Dilutive common stock warrants 16,740 — Weighted average number of common stock shares outstanding—diluted 18,917,213 12,048,985 Net loss per share—basic $ (0.82 ) $ (2.65 ) Net loss per share—diluted $ (0.83 ) $ (2.65 )
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 2015 2014 Common stock warrants 1,553 1,768 Common stock options 1,804 991 Incentive awards 245 247 3,602 3,006

Marketable Securities (Tables)

Marketable Securities (Tables)	12 Months Ended
	Dec. 31, 2015
Cash and Cash Equivalents [Abstract]
Marketable Available-for-Sale Securities	Marketable available-for-sale securities as of December 31, 2015 and 2014 consist of the following (in thousands): Amortized Gross Gross Estimated As of December 31, 2015: Government debt securities $ 1,509 $ — $ (2 ) $ 1,507 Corporate debt securities 27,663 — $ (17 ) 27,646 Asset-backed securities 4,623 — (2 ) 4,621 $ 33,795 $ — $ (21 ) $ 33,774 Amortized Gross Gross Estimated As of December 31, 2014: Corporate debt securities $ 19,706 $ 1 $ (14 ) $ 19,693 Asset-backed securities 3,516 — — 3,516 $ 23,222 $ 1 $ (14 ) $ 23,209

Certain Balance Sheet Items (Ta

Certain Balance Sheet Items (Tables)	12 Months Ended
	Dec. 31, 2015
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 $ 176 $ 176 Purchased software 46 46 Furniture and fixtures 33 33 Leasehold improvements 66 66 Total 321 321 Less accumulated depreciation and amortization (257 ) (235 ) Property and equipment, net $ 64 $ 86
Accrued Liabilities	Accrued liabilities consist of the following (in thousands): December 31, December 31, Accrued compensation $ 1,010 $ 1,504 Accrued pre-clinical and clinical trial expenses 2,015 1,732 Accrued professional fees 283 73 Other accruals 28 79 Total accrued liabilities $ 3,336 $ 3,388

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2015
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, 2015 and 2014 are as follows: December 31, 2015 2014 Principal payments due under the loan facility $ 10,000 $ 4,755 Less: unamortized debt discount (929 ) (380 ) Plus: accreted value of final payment 237 132 Term loan facility, net $ 9,308 $ 4,507
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: 2016 $ 986 2017 3,137 2018 3,423 2019 2,454 Total future principal payments due under loan agreement $ 10,000

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2015
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: 2016 $ 216 2017 222 2018 228 Total future minimum payments $ 666

Common Stock (Tables)

Common Stock (Tables)	12 Months Ended
	Dec. 31, 2015
Text Block [Abstract]
Reserved Shares of Authorized but Unissued Common Stock	As of December 31, 2015 and December 31, 2014, the Company had reserved shares of authorized but unissued common stock as follows: December 31, December 31, Common stock warrants 1,667,398 1,768,347 Equity incentive plans 2,284,421 1,549,616 Total reserved shares of common stock 3,951,819 3,317,963

Stock Plans and Stock-Based C29

Stock Plans and Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
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 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 $ — Vested and expected to vest as of December 31, 2015 1,757,991 $ 7.38 8.22 $ — Exercisable as of December 31, 2015 783,856 $ 6.28 7.81 $ —
Summary of Stock Options Outstanding	The following table summarizes information about stock options outstanding as of December 31, 2015: Options Outstanding Options Exercisable Exercise Price Number of Shares Weighted- Number of Shares $1.98 – $4.77 108,483 8.95 65,800 $5.00 858,442 7.57 617,070 $5.23 10,000 8.65 3,333 $5.90 18,000 9.29 18,000 $6.85 12,000 8.73 4,500 $7.00 77,000 8.28 32,083 $7.99 6,500 8.36 2,594 $10.00 – $10.49 710,203 8.93 37,021 $238.50 3,455 0.73 3,455 1,804,083 8.24 783,856
Estimated Weighted-Average Grant Date Fair Value	The following table presents the weighted-average assumptions the Company used in the Black-Scholes valuation model to derive the grant date fair value-based measurements of employee and director stock options and the resulting estimated weighted-average grant date fair-value-based measurements per share: Year Ended December 31, 2015 2014 Weighted-average assumptions: Expected term 6.1 yrs 6.0 yrs Expected volatility 78 % 90 % Risk-free interest rate 1.65 % 2.02 % Expected dividend yield 0 % 0 % Weighted-average grant date fair value per share $ 6.13 $ 4.06
Summary of Stock-Based Compensation Expense	Employee and director stock-based compensation expense recorded was as follows (in thousands): Year Ended 2015 2014 Research and development $ 823 $ 332 General and administrative 1,643 952 Total $ 2,466 $ 1,284

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2015
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 2015 2014 Deferred tax assets: Federal and state net operating loss carryforwards $ 79,966 $ 71,153 Capitalized research and development 22,287 22,314 Federal and state tax credit carryforwards 7,571 7,083 Other 2,012 1,470 Total deferred tax assets 111,836 102,020 Valuation allowance (111,836 ) (102,020 ) 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 2015 2014 Expected income tax benefit at federal statutory tax rate $ (5,280 ) $ (10,851 ) Net operating loss adjustments 1 (1,703 ) Change in valuation allowance 9,815 11,189 State income taxes, net of federal benefit (618 ) (783 ) Permanent items (3,543 ) 2,595 Research credits (375 ) (446 ) Other, net — (1 ) 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, 2013 $ 1,865 Increases related to prior year tax positions — Increases related to 2014 tax positions 126 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

Organization and Description 31

Organization and Description of Business - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Net loss	$ (15,529)	$ (31,917)
Cash flows from operating activities	(23,324)	(21,114)
Accumulated deficit	(396,288)	$ (380,759)
Cash and cash equivalents and marketable securities	$ 41,500

Summary of Significant Accoun32

Summary of Significant Accounting Policies - Schedule of Fair Value Assets and Liabilities Measured on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	$ 40,716	$ 33,150
Total liabilities measured at fair value	1,220	13,596
Warrant Liability [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total liabilities measured at fair value	1,220	13,596
Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	6,942	9,941
Corporate Debt and Asset Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	33,774	23,209
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	6,942	9,941
Level 1 [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	6,942	9,941
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	33,774	23,209
Level 2 [Member] | Corporate Debt and Asset Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	33,774	23,209
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total liabilities measured at fair value	1,220	13,596
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	$ 1,220	$ 13,596

Summary of Significant Accoun33

Summary of Significant Accounting Policies - Schedule of Changes in Fair Value of Financial Instruments (Detail) - Level 3 [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Warrants [Member]
Fair Value, Instruments Classified in Shareholders' Equity Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance as of December 31, 2013	$ 13,596	$ 6,466
Issuance of financial instrument	258	443
Change in fair value	(11,121)	7,236
Settlement of financial instrument	(1,513)	(549)
Balance as of December 31, 2014	$ 1,220	13,596
Forward contract [Member]
Fair Value, Instruments Classified in Shareholders' Equity Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance as of December 31, 2013		453
Change in fair value		(10)
Settlement of financial instrument		$ (443)

Summary of Significant Accoun34

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Product Information [Line Items]
Cash and cash equivalents, maturity description	90 days or less
Short-term contractual maturities	1 year
Restricted cash	$ 170,000	$ 100,000
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 Accoun35

Summary of Significant Accounting Policies - Schedule of Basic and Diluted Net Loss per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Numerator:
Net loss allocated to common stock-basic	$ (15,529)	$ (31,917)
Adjustment for revaluation of warrants	(94)
Net loss allocated to common stock-diluted	$ (15,623)	$ (31,917)
Denominator:
Weighted average number of common stock shares outstanding-basic	18,900,473	12,048,985
Dilutive common stock warrants	16,740
Weighted average number of common stock shares outstanding-diluted	18,917,213	12,048,985
Net loss per share - basic:	$ (0.82)	$ (2.65)
Net loss per share - diluted:	$ (0.83)	$ (2.65)

Summary of Significant Accoun36

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, 2015	Dec. 31, 2014
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the computation of diluted loss per share	3,602	3,006
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	1,553	1,768
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	1,804	991
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	245	247

Marketable Securities - Marketa

Marketable Securities - Marketable Available-for-Sale Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 33,795	$ 23,222
Gross Unrealized Gains		1
Gross Unrealized Losses	(21)	(14)
Estimated Fair Value	33,774	23,209
Government Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,509
Gross Unrealized Losses	(2)
Estimated Fair Value	1,507
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	27,663	19,706
Gross Unrealized Gains		1
Gross Unrealized Losses	(17)	(14)
Estimated Fair Value	27,646	19,693
Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	4,623	3,516
Gross Unrealized Losses	(2)
Estimated Fair Value	$ 4,621	$ 3,516

Marketable Securities - Additio

Marketable Securities - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Government Debt Securities [Member] | Maximum [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	1 year
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable investments continuous unrealized loss position	$ 0	$ 0
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, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 321	$ 321
Less accumulated depreciation and amortization	(257)	(235)
Property and equipment, net	64	86
Office and Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	176	176
Purchased Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	46	46
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	33	33
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 66	$ 66

Certain Balance Sheet Items - A

Certain Balance Sheet Items - Accrued Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Accrued compensation	$ 1,010	$ 1,504
Accrued pre-clinical and clinical trial expenses	2,015	1,732
Accrued professional fees	283	73
Other accruals	28	79
Total accrued liabilities	$ 3,336	$ 3,388

Collaboration and License Agr41

Collaboration and License Agreements - Additional Information (Detail)	1 Months Ended	12 Months Ended
	Jun. 30, 1998USD ($)	Dec. 31, 2015USD ($)Agreement	Dec. 31, 2014USD ($)
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
Janssen Pharmaceutical NV [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Payments made under agreement		0	0
Royalties received		$ 0	$ 0
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
Contingent payment eligible to receive on development and commercial events		$ 228,000,000

Debt - Additional Information (

Debt - Additional Information (Detail) - USD ($)	Aug. 07, 2015	Sep. 30, 2013	Dec. 31, 2015	Dec. 31, 2013
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
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, fixed interest rate			8.75%
Facility loan available for draw down		$ 5,000,000
2013 Term Loan Facility [Member] | Second Tranche [Member] | Wall Street Journal Prime Rate [Member]
Debt Instrument [Line Items]
Facility loan, prime rate plus			4.25%
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%
Prepayment fee percentage	3.00%
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, drawn	$ 0
Facility loan available for draw down	$ 5,000,000

Debt - Schedule of Term Loan Fa

Debt - Schedule of Term Loan Facility, Debt Discounts and Final Payment (Detail) - 2015 Term Loan Facility [Member] - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Line of Credit Facility [Line Items]
Principal payments due under the loan facility	$ 10,000	$ 4,755
Less: unamortized debt discount	(929)	(380)
Plus: accreted value of final payment	237	132
Term loan facility, net	$ 9,308	$ 4,507

Debt - Schedule of Future Princ

Debt - Schedule of Future Principal Payments Due under Loan Facility (Detail) $ in Thousands	Dec. 31, 2014USD ($)
Maturities of Long-term Debt [Abstract]
2,016	$ 986
2,017	3,137
2,018	3,423
2,019	2,454
Total future principal payments due under loan agreement	$ 10,000

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail)	Nov. 08, 2013ft²	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)
Loss Contingencies [Line Items]
Rent expenses		$ 300,000	$ 400,000
Accrued in the balance sheets related to indemnification obligations		0
Indemnification liabilities		$ 0	$ 0
Lease Facility [Member]
Loss Contingencies [Line Items]
Lease start date	Jan. 16, 2014
Lease expiration date	Dec. 31, 2018
Area of office space | ft²	8,894

Commitments and Contingencies46

Commitments and Contingencies - Future Minimum Lease Payments (Detail) $ in Thousands	Dec. 31, 2015USD ($)
Commitments and Contingencies Disclosure [Abstract]
2,016	$ 216
2,017	222
2,018	228
Total future minimum payments	$ 666

Preferred Stock - Additional In

Preferred Stock - Additional Information (Detail) - shares	Dec. 31, 2015	Dec. 31, 2014
Equity [Abstract]
Preferred stock, shares authorized	10,000,000	10,000,000

Common Stock - Additional Infor

Common Stock - Additional Information (Detail) - USD ($)	Jul. 27, 2015	Jul. 25, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Aug. 31, 2015	Nov. 07, 2014	Sep. 30, 2013
Class of Stock [Line Items]
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
Proceeds from sale of common stock	$ 21,100,000		$ 4,300,000
Common stock, shares issued	8,188,000		23,447,003	14,696,108
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			$ (11,121,000)	$ 7,236,000
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]
Common stock, shares issued						114,436
Exercise price of common stock						$ 2.84
At the Market Facility [Member]
Class of Stock [Line Items]
Common stock shares sold			0

Common Stock - Reserved Shares

Common Stock - Reserved Shares of Authorized but Unissued Common Stock (Detail) - shares	Dec. 31, 2015	Dec. 31, 2014
Class of Stock [Line Items]
Total reserved shares of common stock	3,951,819	3,317,963
Common Stock Warrants [Member]
Class of Stock [Line Items]
Total reserved shares of common stock	1,667,398	1,768,347
Equity Incentive Plans [Member]
Class of Stock [Line Items]
Total reserved shares of common stock	2,284,421	1,549,616

Stock Plans and Stock-Based C50

Stock Plans and Stock-Based Compensation - Additional Information (Detail) - USD ($)	Jan. 01, 2016	Jun. 03, 2014	Jun. 30, 2014	Sep. 30, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2007	Apr. 30, 2014	Jan. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividend yield					0.00%	0.00%	0.00%
Fair value of options vested					$ 2,200,000	$ 1,000,000
Share based compensation, stock option, unamortized expense					$ 4,800,000	$ 1,900,000
Share based compensation, stock option, unamortized expense vesting period					2 years 7 months 6 days	3 years
Share reserved for issue					3,951,819	3,317,963
Conversion of incentive award from liability to equity accounting						$ 121,000
Allocated share-based compensation expense					$ 2,466,000	1,284,000
Options to purchase common stock					114,436
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					$ 21,000	$ 8,000
Options to purchase common stock					10,000	10,000
Options to purchase common stock, unvested					18,945
Incentive award issued					2,335
Incentive awards outstanding, Unvested					1,167
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%
Number of additional shares authorized			500,000
Shares available for grant					235,367
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%
2013 Equity Incentive Plan [Member] | Restricted Stock [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation arrangement by share based payment award, award vesting period				4 years
2013 Equity Incentive Plan [Member] | Restricted Stock [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation arrangement by share based payment award, award vesting period				5 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 based compensation arrangement by share based payment award, award vesting period		2 years			4 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.
Conversion of incentive award from liability to equity accounting		$ 121,000,000
Allocated share-based compensation expense					$ 323,000	$ 285,000
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 C51

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, 2015	Dec. 31, 2014
Shares Subject to Outstanding Options
Outstanding at the beginning of period	991,010
Options granted	845,703
Options exercised	0
Options forfeited	(15,631)
Options expired	(16,999)
Outstanding as end of period	1,804,083	991,010
Vested and expected to vest	1,757,991
Exercisable	783,856
Weighted-Average Exercise Price of Options
Outstanding at the beginning of period	$ 6.09
Options granted	9
Options exercised	0
Options forfeited	4.75
Options expired	12.31
Outstanding as end of period	7.41	$ 6.09
Vested and expected to vest	7.38
Exercisable	$ 6.28
Weighted-Average Remaining Contractual Term (Years)
Outstanding	8 years 2 months 27 days	0 years
Vested and expected to vest	8 years 2 months 19 days
Exercisable	7 years 9 months 22 days
Aggregate Intrinsic Value (In Thousands)
Outstanding at the beginning of period		$ 0
Outstanding as end of period	$ 0
Vested and expected	0
Exercisable	$ 0

Stock Plans and Stock-Based C52

Stock Plans and Stock-Based Compensation - Summary of Stock Options Outstanding (Detail)	12 Months Ended
	Dec. 31, 2015$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option Outstanding Number of Shares	1,804,083
Weighted-Average Remaining Contractual Term (Years)	8 years 2 months 27 days
Options Exercisable Number of Shares	783,856
$1.98 - $4.77 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option Outstanding Number of Shares	108,483
Weighted-Average Remaining Contractual Term (Years)	8 years 11 months 12 days
Options Exercisable Number of Shares	65,800
$1.98 - $4.77 [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Price | $ / shares	$ 1.98
$1.98 - $4.77 [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Price | $ / shares	4.77
$5.00 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Price | $ / shares	$ 5
Option Outstanding Number of Shares	858,442
Weighted-Average Remaining Contractual Term (Years)	7 years 6 months 26 days
Options Exercisable Number of Shares	617,070
$5.23 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Price | $ / shares	$ 5.23
Option Outstanding Number of Shares	10,000
Weighted-Average Remaining Contractual Term (Years)	8 years 7 months 24 days
Options Exercisable Number of Shares	3,333
$5.90 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Price | $ / shares	$ 5.90
Option Outstanding Number of Shares	18,000
Weighted-Average Remaining Contractual Term (Years)	9 years 3 months 15 days
Options Exercisable Number of Shares	18,000
$6.85 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Price | $ / shares	$ 6.85
Option Outstanding Number of Shares	12,000
Weighted-Average Remaining Contractual Term (Years)	8 years 8 months 23 days
Options Exercisable Number of Shares	4,500
$7.00 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Price | $ / shares	$ 7
Option Outstanding Number of Shares	77,000
Weighted-Average Remaining Contractual Term (Years)	8 years 3 months 11 days
Options Exercisable Number of Shares	32,083
$7.99 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Price | $ / shares	$ 7.99
Option Outstanding Number of Shares	6,500
Weighted-Average Remaining Contractual Term (Years)	8 years 4 months 10 days
Options Exercisable Number of Shares	2,594
$10.00 - $10.49 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option Outstanding Number of Shares	710,203
Weighted-Average Remaining Contractual Term (Years)	8 years 11 months 5 days
Options Exercisable Number of Shares	37,021
$10.00 - $10.49 [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Price | $ / shares	$ 10
$10.00 - $10.49 [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Price | $ / shares	10.49
$238.50 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Price | $ / shares	$ 238.50
Option Outstanding Number of Shares	3,455
Weighted-Average Remaining Contractual Term (Years)	8 months 23 days
Options Exercisable Number of Shares	3,455

Stock Plans and Stock-Based C53

Stock Plans and Stock-Based Compensation - Estimated Weighted-Average Grant Date Fair Value (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Expected term	6 years 1 month 6 days	6 years
Expected volatility	78.00%	90.00%
Risk-free interest rate	1.65%	2.02%
Expected dividend yield	0.00%	0.00%	0.00%
Weighted-average grant date fair value per share	$ 6.13	$ 4.06

Stock Plans and Stock-Based C54

Stock Plans and Stock-Based Compensation - Summary of Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 2,466	$ 1,284
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	823	332
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 1,643	$ 952

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Income Tax [Line Items]
Provision for income taxes	$ 0	$ 0
Net valuation allowance change	$ 9,800,000	$ 11,200,000
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 2015 remain open to examination by the major taxing authorities.
Domestic Tax Authority [Member]
Income Tax [Line Items]
Net operating loss carryforward	$ 205,700,000
Research and development tax credit carry forwards	$ 7,200,000
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	2,035
State and Local Jurisdiction [Member]
Income Tax [Line Items]
Net operating loss carryforward	$ 172,000,000
Research and development tax credit carry forwards	$ 3,500,000
State and Local Jurisdiction [Member] | Minimum [Member]
Income Tax [Line Items]
NOL carry forward expiry date	2,016
State and Local Jurisdiction [Member] | Maximum [Member]
Income Tax [Line Items]
NOL carry forward expiry date	2,035

Income Taxes - Components of De

Income Taxes - Components of Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets:
Federal and state net operating loss carryforwards	$ 79,966	$ 71,153
Capitalized research and development	22,287	22,314
Federal and state tax credit carryforwards	7,571	7,083
Other	2,012	1,470
Total deferred tax assets	111,836	102,020
Valuation allowance	(111,836)	(102,020)
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, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Expected income tax benefit at federal statutory tax rate	$ (5,280)	$ (10,851)
Net operating loss adjustments	1	(1,703)
Change in valuation allowance	9,815	11,189
State income taxes, net of federal benefit	(618)	(783)
Permanent items	(3,543)	2,595
Research credits	(375)	(446)
Other, net		(1)
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, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Balance at beginning of period	$ 1,991	$ 1,865
Increases related to prior year tax positions	0	0
Increases related to tax positions	136	126
Balance at end of period	$ 2,127	$ 1,991

Related-Party Transactions - Ad

Related-Party Transactions - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
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)	Jan. 01, 2016shares
Subsequent Event [Member] | 2013 Equity Incentive Plan [Member]
Subsequent Event [Line Items]
Number of shares automatically increased in share reserves	1,172,350