Cymabay Therapeutics (CBAY) 10-K 23 Mar 15 2014 FY Annual report Financial data

Document_and_Entity_Informatio

Document and Entity Information (USD $)	12 Months Ended
	Dec. 31, 2014	Mar. 01, 2015	Jun. 30, 2014
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	FALSE
Document Period End Date	31-Dec-14
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY
Trading Symbol	CYMA
Entity Registrant Name	CymaBay Therapeutics, Inc.
Entity Central Index Key	1042074
Current Fiscal Year End Date	-19
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		15,240,300
Entity Public Float			$58,176,723

Balance_Sheets

Balance Sheets (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Current assets:
Cash and cash equivalents	$11,586	$24,401
Marketable securities	23,209	6,843
Contract receivables	211	110
Accrued interest receivable	136	68
Prepaid expenses	1,991	364
Other current assets	96	453
Total current assets	37,229	32,239
Property and equipment, net	86	3
Other assets	159	258
Total assets	37,474	32,500
Current liabilities:
Accounts payable	2,085	697
Accrued liabilities	3,388	2,251
Warrant liability	13,596	6,466
Facility loan	1,355	38
Accrued interest payable	35	36
Total current liabilities	20,459	9,488
Facility loan, less current portion	3,152	4,407
Other liabilities	13	9
Total liabilities	23,624	13,904
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;14,696,108 and 9,455,064 shares issued and outstanding as of December 31, 2014 and December 31, 2013, respectively	1	1
Additional paid-in capital	394,622	367,435
Accumulated other comprehensive (loss) income	-14	2
Accumulated deficit	-380,759	-348,842
Total stockholders' equity	13,850	18,596
Total liabilities and stockholders' equity	$37,474	$32,500

Balance_Sheets_Parenthetical

Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Statement of Financial Position [Abstract]
Preferred stock, par value	$0.00	$0.00
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	$0.00	$0.00
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	14,696,108	9,455,064
Common stock, shares outstanding	14,696,108	9,455,064

Statements_of_Operations_and_C

Statements of Operations and Comprehensive Loss (USD $)	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Operating expenses:
Research and development	$15,823	$4,525
General and administrative	8,185	4,871
Total operating expenses	24,008	9,396
Loss from operations	-24,008	-9,396
Other income (expense):
Interest income	74	10
Interest expense	-755	-822
Other income (expense), net	-7,228	135
Net loss	-31,917	-10,073
Net (loss) income attributable to common stockholders	-31,917	243,994
Net loss	-31,917	-10,073
Other comprehensive loss:
Unrealized (loss) gain on marketable securities	-16	2
Other comprehensive loss	-16	2
Comprehensive loss	($31,933)	($10,071)
Basic net (loss) income per common share	($2.65)	$103.52
Diluted net loss per common share	($2.65)	($3.54)
Weighted average common shares outstanding used to calculate basic net loss per common share	12,048,985	2,357,036
Weighted average common shares outstanding used to calculate diluted net loss per common share	12,048,985	2,845,609

Statements_of_Redeemable_Conve

Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) (USD $)	Total	Redeemable Convertible Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Deficit [Member]
In Thousands, except Share data
Balance at beginning of period at Dec. 31, 2012	($328,567)	$318,697		$913		($329,480)
Balance at beginning of period (in shares) at Dec. 31, 2012		661,059	5,792
Issuance of common stock upon exercise of options (in shares)			78
Non-employee stock-based compensation expense	17			17
Employee and director stock-based compensation expense	866			866
Accretion to redemption value of redeemable convertible preferred stock	-9,289	9,289				-9,289
Repurchase of convertible preferred stock, value	8,247	-8,250		8,247
Repurchase of convertible preferred stock, (in shares)		-39,606
Conversion of preferred stock to common stock, value	319,736	-319,736		319,736
Conversion of preferred stock to common stock, (in shares)		-621,453	2,793,281
Issuance of common stock, value	20,712		1	20,711
Issuance of common stock, (in shares)			6,030,969
Conversion of incentive award from liability to equity accounting	16,945			16,945
Extinguishment of debt through issuance of common stock, (in shares)			624,944
Net loss	-10,073					-10,073
Net unrealized gain on marketable securities	2				2
Balance at end of period at Dec. 31, 2013	18,596		1	367,435	2	-348,842
Balance at end 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		431
Non-employee stock-based compensation expense	8			8
Employee and director stock-based compensation expense	1,173			1,173
Issuance of common stock, value	25,286			25,286
Issuance of common stock, (in shares)			5,204,000
Conversion of incentive award from liability to equity accounting	121			121
Net loss	-31,917					-31,917
Net unrealized gain 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

Statements_of_Redeemable_Conve1

Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Statement of Stockholders' Equity [Abstract]
Stock issuance cost	$3,034	$5,356

Statements_of_Cash_Flows

Statements of Cash Flows (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Operating activities
Net loss	($31,917)	($10,073)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	18	55
Amortization of notes payable conversion option		10
Non-employee stock-based compensation expense	8	17
Employee and director stock-based compensation expense	1,284	875
Amortization of premium on marketable securities	453	48
Non-cash interest associated with debt discount accretion	198	47
Change in fair value of warrant liability	7,236	494
Loss (gain) on sale of property and equipment	2	-632
Changes in assets and liabilities:
Contract receivables	-101	-2
Accrued interest receivable	-68	-59
Prepaid expenses	-1,627	-217
Other assets	3	-216
Accounts payable	1,388	40
Accrued liabilities	1,889	499
Accrued interest payable	107	692
Other liabilities	13	-36
Net cash used in operating activities	-21,114	-8,458
Investing activities
Purchases of property and equipment	-103
Proceeds from sale of property and equipment		658
Purchases of marketable securities	-27,334	-6,933
Proceeds from sales and maturities of marketable securities	10,499	44
Net cash used in investing activities	-16,938	-6,231
Financing activities
Proceeds from facility loan		4,853
Repayment of facility loan principal	-244
Proceeds from issuance of common stock and warrants, net of issuance costs	25,430	26,514
Repurchase of preferred stock		-3
Proceeds from issuance of common stock upon exercise of warrants	46
Proceeds from issuance of common stock upon exercise of employee stock options	5
Net cash provided by financing activities	25,237	31,364
Net (decrease) increase in cash and cash equivalents	-12,815	16,675
Cash and cash equivalents at beginning of period	24,401	7,726
Cash and cash equivalents at end of period	11,586	24,401
Supplemental disclosure of cash flow information
Cash paid for interest	435	74
Financing costs in accrued expenses		309
Issuance of common stock warrants to lenders	443	479
Fair value of forward contract		453
Issuance of common stock warrants to common stockholders		5,493
Conversion of preferred shares into common stock		323,155
Issuance of common stock for debt extinguishment		16,945
Issuance of common stock upon warrant exercises	549
Noncash issuance costs incurred in common stock financing	453
Reclassification of incentive awards to equity	$121

Organization_and_Description_o

Organization and Description of Business	12 Months Ended
	Dec. 31, 2014
Accounting Policies [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. Arhalofenate, the Company’s lead product candidate, is being developed for the treatment of gout. Arhalofenate has successfully completed five Phase 2 clinical trials in patients with gout and consistently demonstrated the ability to reduce gout flares and reduce serum uric acid (sUA). Gout flares are recurring and painful episodes of joint inflammation that are triggered by the presence of monosodium urate crystals that form as a result of elevated sUA levels. The Company believes the potential for arhalofenate to prevent or reduce flares while also lowering sUA could differentiate it from currently available treatments for gout and classify it as the first potential drug in what the Company believes could be a new class of gout therapy referred to as Urate Lowering Anti-Flare Therapy (ULAFT). Arhalofenate has established a favorable safety profile in clinical trials involving over 1,000 patients exposed to date. The Company is currently planning to hold an end of phase 2 meeting with the FDA in the second half of 2015 to review the results of its completed studies and to discuss the design of a phase 3 program for arhalofenate. Our second product candidate, MBX-8025, demonstrated favorable effects on cholesterol, triglycerides and markers of liver health in a Phase 2 clinical trial in patients with mixed dyslipidemia. The Company is planning to purse development of MBX-8025 in a number of orphan diseases in which these attributes could be beneficial, such as homozygous familial hypercholestorolemia (HoFH), primary biliary cirrhosis (PBC) and severe hypertriglyceridemia (SHTG). The Company also believes that MBX-8025 could have utility in the treatment of the more prevalent, but high unmet need, indication of nonalcoholic steatohepatitis (NASH). The Company plans to initiate one or more pilot or proof-of-concept studies for MBX-8025, beginning with HoFH, in the first half of 2015.
	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 accompanying financial statements for the years ended December 31, 2014 and 2013, have been prepared on a going concern basis, which contemplates the realization of assets and the settlement of liabilities and commitments in the normal course of business for the foreseeable future. The Company has incurred net losses from operations since its inception and has an accumulated deficit of $380.8 million as of December 31, 2014. The Company recorded net losses of $31.9 million and $10.1 million for the years ended December 31, 2014 and 2013, respectively. The Company also recorded negative cash flows from operating activities during 2014 and 2013 of $21.1 million and $8.5 million, respectively. To date, none of the Company’s product candidates have been approved for marketing and sale, and the Company has not recorded any product sales. Management expects operating losses to continue for the next several years. Because of the numerous risks and uncertainties associated with developing drugs, we are unable to predict the extent of any future losses or whether or when we will become profitable, if at all. Our research and development expenditures and general and administrative expenses have exceeded our revenues for each year, and we expect to spend significant additional amounts to fund the continued development of our candidates. As a result, we expect to continue to incur substantial operating expenses, and, consequently, we will need to generate significant additional revenues to achieve future profitability.
	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.
	In 2013, in order to address immediate capital requirements, the Company entered into a series of financing transactions. Specifically, on September 30, 2013, all of the shares of the Company’s outstanding redeemable convertible preferred stock converted to common stock and the Company issued shares of common stock and warrants to purchase shares of common stock in a private placement for gross proceeds of $26.8 million. The Company raised an additional $5.0 million in venture debt financing pursuant to a $10.0 million loan agreement, resulting in aggregate net proceeds to CymaBay of $28.8 million after deducting placement agent fees and offering expenses. Also on September 30, 2013, the Company issued shares of common stock in cancellation of approximately $16.9 million of debt owed to the lender. On October 31, 2013, the Company sold additional shares of common stock and warrants to purchase shares of common stock, which sales are also part of the private placement, for net proceeds to CymaBay of $2.2 million after deducting placement agent fees and estimated offering expenses. Further, on November 22, 2013, the Company entered into an agreement with investors to purchase shares of common stock and warrants to purchase shares of common stock as part of the private placement for net proceeds of $2.7 million, which sales occurred shortly after the listing of the Company’s common stock on the over-the-counter market on January 24, 2014. Collectively, the private placement, the venture debt financing and the issuance of our common stock in cancellation of the $16.9 million of debt is referred to as the 2013 financing. Furthermore, on July 25, 2014, the Company completed a public offering of 4.6 million shares of our 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.
	The Company has incurred operating losses since its inception and had an accumulated deficit of $380.8 million at December 31, 2014. Management expects operating losses and negative cash flows to continue for the foreseeable future. As of December 31, 2014, the Company had $34.8 million in cash and cash equivalents and marketable securities, which is available to fund future operations. Taking into account the repayment of its outstanding debt classified within current liabilities on the Company’s Balance Sheet as of December 31, 2014, the Company anticipates that it will be required to seek additional equity or debt financing and/or non-dilutive funding from potential licensing deals to fund its operations through December 31, 2015. If the Company is unable to obtain additional funding during 2015, the Company will delay one or more of its planned development programs commencing early in the second half of 2015. Consistent with the actions the Company has taken in the past, it will prioritize necessary and appropriate steps to enable the continued operations of the business and preservation of the value of its assets beyond the next twelve months, including but not limited to actions such as reduced personnel-related costs, additional curtailment of the Company’s development activities and other discretionary expenditures that are within the Company’s control. These reductions in expenditures, if required, may have an adverse impact on the Company’s ability to achieve certain planned objectives during 2015. In addition to seeking equity or debt financing, the Company may seek to access additional capital to support future operations through licensing, partnering or other strategic collaborative arrangements. It is unclear if or when any such transactions will occur, on satisfactory terms or at all.

Summary_of_Significant_Account

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies
	Basis of Presentation and Use of Estimates
	The 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 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, short-term marketable securities, accounts payable, accrued expenses, warrant liabilities, and forward contracts. 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.
	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 unobservable for the asset or liability.
	The following table presents the fair value of the Company’s financial assets and liabilities using the above input categories (in thousands):
	(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
		As of December 31, 2013
	Description	Level 1			Level 2			Level 3		Fair Value
	Money market funds	$	21,097		$	—		$	—	$	21,097
	Corporate debt and asset backed securities		—			6,843			—		6,843
	Total assets measured at fair value	$	21,097		$	6,843		$	—	$	27,940
	Forward contract	$	—		$	—		$	453	$	453
	Warrant liability		—			—			6,466		6,466
	Total liabilities measured at fair value	$	—		$	—		$	6,919	$	6,919
	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, 2014 and 2013, the Company held a Level 3 liability associated with warrants, issued in connection with the Company’s equity offerings, completed in September and October 2013 as well as January 2014. The warrants are considered liabilities and are valued using a binomial option-pricing model, the significant unobservable inputs for which include exercise price of the warrants, market price of the underlying common shares, expected term, expected volatility based on a group of the Company’s peers and the risk-free rate corresponding to the expected term of the warrants. As of December 31, 2013, the Company also held a Level 3 liability associated with a forward contract which arose in connection with the Company’s November 22, 2013 execution of an equity purchase agreement with certain investors. The agreement required the Company to issue a fixed number of shares of common stock and warrants to purchase common stock at a predetermined price of $3.0 million provided the Company completes the listing of its common stock on a public stock exchange. The forward contract’s fair value was determined upon execution as the difference between the present value of the equity proceeds to be received under the agreement less the fair value of the underlying securities. The forward contract liability was recorded in the balance sheet as a component of accrued liabilities and was revalued at each reporting period until contract settlement, which occurred on January 29, 2014. The fair value of the underlying common stock and warrants were valued using an option-pricing model, the inputs of which are similar to those used in the valuation of the Company’s liability classified warrants. 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 and forward contract liabilities.
	The following table sets forth a summary of the changes in the fair value of our Level 3 financial instruments (in thousands):
		Warrant			Forward
		Liability			Contract
	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		$	—
	The gains and losses from remeasurement of Level 3 financial liabilities are recorded through other income (expense), net on the accompanying statements of operations and comprehensive loss.
	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 accompanying contractual maturities greater than one year from the balance sheet date are classified as short-term in the balance sheet.
	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, 2014 and 2013, cash restricted under these arrangements was $100,000 and $155,000, 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.
	Contract Receivables
	Contract receivables consist of amounts due from a collaboration partner for certain reimbursable patent costs. Such expense reimbursements are presented as a reduction to general and administrative expense in the Company’s Statements of Operations and Comprehensive Loss.
	Property and Equipment
	Property and equipment is stated 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, 2014 and 2013.
	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 to 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.
	Equity awards granted to non-employees are accounted for 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 the 2013 financing 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 being recognized as a component of other income (expense) in the accompanying statements of operations and comprehensive loss.
	Income Taxes
	The Company utilizes the liability method of accounting for income taxes. Under this method, deferred tax assets and liabilities are determined based on differences between the financial reporting and the tax bases of assets and liabilities and are measured using enacted tax rates and laws that will be in effect when the differences are expected to reverse. 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 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, 2014 and 2013.
	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 convertible preferred stock and stockholders’ deficit, and is stated net of related tax effects, if any.
Net Income (Loss) Per Common Share
Basic net income (loss) per share of common stock is based on the weighted average number of shares of common stock outstanding equivalents during the period. Prior to the 2013 financing, in addition to common stock, the Company had redeemable convertible preferred stock outstanding that contractually entitled the holder to participate in dividends and earnings of the Company. Accordingly, the Company applied the two-class method for calculating net income (loss) per share. Under this method, all undistributed earnings were allocated first to the preferred stockholders based on their contractual right to dividends. This right was calculated on a pro rated basis for the portion of the period the preferred shares were outstanding. In addition, in connection with the 2013 financing, during the year ended December 31, 2013, the Company converted all outstanding redeemable convertible preferred stock into common stock. The excess of the carrying amount of such redeemable convertible preferred stock over the fair value of the consideration paid to the holders was treated as an adjustment that reduced preferred stockholders’ dividend or distribution entitlement. The amount of earnings that resulted from adjusting net loss for the period as described above was allocated between weighted average number of participating preferred and common stock shares based on their entitlement to such distributions as if all of the earnings of the period had been distributed.
Diluted net loss per share of common stock is calculated using the more dilutive of the two approaches: one, “as-converted” method, under which the weighted average number of common stock shares outstanding during the period is adjusted to include the assumed conversion of redeemable convertible preferred stock at the beginning of the period, and the other, the “two-class” method as described above. Under either approach, the weighted average number of shares outstanding is also adjusted to include the assumed exercises of stock options and warrants, if dilutive. For periods in which the Company has basic net loss per share of common stock, such as for the year ended December 31, 2014, diluted net loss per share is the same as basic, as any adjustments would have been anti-dilutive. For the year ending December 31, 2013, the Company’s diluted net loss per common share was calculated using the “as-converted” method, as it resulted in a net loss per share of common stock and accordingly, was more dilutive than the “two-class” method.
In all periods presented, the Company’s outstanding stock options and warrants 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 income (loss) per share (in thousands, except share and per share amounts):
	Year Ended December 31,
	2014			2013
Basic:
Numerator:
Net loss	$	(31,917	)	$	(10,073	)
Accretion to redemption value of redeemable convertible preferred stock		—			(9,289	)
Reduction in redeemable convertible preferred stock distribution entitlement upon extinguishment		—			313,933
Amounts allocated to participating redeemable convertible preferred stock		—			(50,577	)
Net (loss) income allocated to common stock—basic	$	(31,917	)	$	243,994
Denominator:
Weighted average number of common stock shares outstanding—basic		12,048,985			2,357,036
Net (loss) income per share-basic:	$	(2.65	)	$	103.52
Diluted:
Numerator:
Net (loss) income allocated to common stock	$	(31,917	)	$	243,994
Adjustments from assumed conversion of redeemable convertible preferred stock		—			(254,067	)
Net loss allocated to common stock—diluted	$	(31,917	)	$	(10,073	)
Denominator:
Weighted average number of common stock shares outstanding		12,048,985			2,357,036
Weighted average number of preferred stock shares outstanding		—			488,573
Total common stock equivalent shares		12,048,985			2,845,609
Net loss per share—diluted	$	(2.65	)	$	(3.54	)
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
	December 31,
	2014			2013
Warrants for common stock		1,768			1,743
Common stock options		991			577
Incentive awards		247			—
		3,006			2,320

Marketable_Securities

Marketable Securities	12 Months Ended
	Dec. 31, 2014
Cash and Cash Equivalents [Abstract]
Marketable Securities	3. Marketable Securities
	Marketable available-for-sale securities as of December 31, 2014 and 2013 consist of the following (in thousands):
		Amortized		Gross		Gross			Estimated
		Cost		Unrealized		Unrealized			Fair Value
				Gains		Losses
	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
		Amortized		Gross		Gross			Estimated
		Cost		Unrealized		Unrealized			Fair Value
				Gains		Losses
	As of December 31, 2013:
	Corporate debt securities	$	6,355	$	3	$	(2	)	$	6,356
	Asset-backed securities		486		1		—			487
		$	6,841	$	4	$	(2	)	$	6,843
	As of December 31, 2014 and 2013, the Company’s 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, 2014 and 2013. None of these investments have been in a continuous unrealized loss position for more than 12 months as of December 31, 2014 and 2013.

Certain_Balance_Sheet_Items

Certain Balance Sheet Items	12 Months Ended
	Dec. 31, 2014
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,
		2014			2013
	Office and computer equipment	$	176		$	556
	Purchased software		46			166
	Furniture and fixtures		33			42
	Leasehold improvements		66			2,534
	Total		321			3,298
	Less accumulated depreciation and amortization		(235	)		(3,295	)
	Property and equipment, net	$	86		$	3
	Accrued liabilities consist of the following (in thousands):
		December 31,
		2014			2013
	Accrued compensation	$	1,504		$	518
	Accrued pre-clinical and clinical trial expenses		1,732			418
	Accrued professional fees		73			782
	Forward contract		—			453
	Other accruals		79			80
	Total accrued liabilities	$	3,388		$	2,251

Collaboration_and_License_Agre

Collaboration and License Agreements	12 Months Ended
	Dec. 31, 2014
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 PPARd compounds (the “PPARd Products”) with Janssen Pharmaceutical NV, with the right to grant sublicenses to third parties to make, use and sell such PPARd Products. Under the terms of the agreement, the Company has full control and responsibility over the research, development and registration of any PPARd Products and is required to use diligent efforts to conduct all such activities. Janssen has the sole responsibility for the preparation, filing, prosecution, maintenance of, and defense of the patents with respect to, the PPARd Products. Janssen has a right of first negotiation under the agreement to license a particular PPARd Product from the Company in the event that the Company elects to seek a third party corporate partner for the research, development, promotion, and/or commercialization of such PPARd Products. Under the terms of the agreement Janssen is entitled to receive up to an 8% royalty on net sales of PPARd Products. No payments were made and no royalties were received under this agreement during the years ended December 31, 2014 and 2013.
	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.
	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, 2014 and 2013 and no royalties have been paid to date.

Debt

Debt	12 Months Ended
	Dec. 31, 2014
Debt Disclosure [Abstract]
Debt	6. Debt
	JJDC Convertible Note
	On June 20, 2006 the Company entered into an equity and loan facility with the Johnson and Johnson Development Corporation (“JJDC”) pursuant to which the Company could draw down up to an aggregate of $30 million in loans in the form of convertible preferred stock promissory notes. In March and September 2008, the Company issued notes in the aggregate amount of $3.5 million and $10.5 million, respectively. The notes were due on March 17 and September 17, 2011, including interest that accrued at 7.57% per annum. In December 2010, the aggregate principal amount and all accrued interest under the notes issued in March and September 2008 were converted into the Company’s Series E-3 convertible preferred stock (Series E-3 Preferred) at 232.93 per share.
	In February and July 2009, the Company issued notes in the aggregate amount of $7.0 million and $6.7 million, respectively, in accordance with the terms of the equity and loan facility with JJDC. The notes were due in February 2012 and July 2012, including interest that accrued at 4.42% per annum and 4.960% per annum, respectively. In January 2012, the Company amended the maturity dates of the outstanding $7.0 million and $6.7 million convertible promissory notes to extend the maturity date to March 1, 2013, and interest rates were increased to 4.919% and 5.46% per annum, respectively. In addition, the conversion price of the notes to convert into shares of the Company’s Series C-1 Preferred Stock was decreased from $438.84 per share to $292.56 per share. All of these notes were further amended in March 2013, to extend the maturity date on the notes to August 1, 2013, and to make the notes subordinate to repayment of the Company’s severance obligations to all employees until January 1, 2014. On July 31, 2013, the maturity date was extended to December 31, 2013. For the year ended December 31, 2013, the Company recognized $0.6 million of interest expense related to the convertible promissory notes. On September 30, 2013, the outstanding principal and accrued interest of $16.9 million under the equity and loan facility with JJDC was extinguished in exchange for the issuance of 624,944 shares of common stock as an integral part of the 2013 finance restructuring.
	Facility Loan
	On September 30, 2013, the Company entered into a facility loan agreement with Silicon Valley Bank and Oxford Finance for a total loan amount of $10.0 million of which the first tranche of $5.0 million was drawn as part of the 2013 financing and bears interest at a rate equal 8.75% per annum. 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 (the second draw milestone) and shall remain available to the Company until June 30, 2015. Loans under the second tranche will bear 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.
	For each tranche borrowed, 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. After the 36-month amortization period of each tranche, the remaining balance of such tranche and a final payment equal to 6.50% of the original principal amount of the applicable tranche are payable on the maturity date of such tranche. The final payment equal to 6.50% of the original principal is being accreted over the life of the loan.
	Future principal payments due under the loan facility are as follows (in thousands):
		Principal
		Payments
	Year ending December 31:
	2015	$	1,546
	2016		1,687
	2017		1,522
	Total future principal payments due under loan agreement	$	4,755
	During the loan term, the term loan facility provides that the Company must maintain compliance with one of two financial covenants at all times: (1) maintain 1.3 times cash to outstanding debt or (2) maintain sufficient cash on hand to support eight months of operations based on a trailing average monthly cash burn. The term loan facility also contains a series of performance covenants however failure to comply with these performance covenants shall not be an event of default under the term loan facility so long as the Company deposits an amount equal to 100% of the aggregate outstanding term loans in a segregated, blocked deposit account at Silicon Valley Bank. As of December 31, 2014, the Company was in compliance with its loan covenants.
	The Company is permitted to make voluntary prepayments of the term loans with a prepayment fee equal to 3% of the 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 was required to pay a facility fee of 1.00% on the term loan facility commitment. In addition, at the time of the facility loan drawdown, 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. As a result of this a warrant liability of $0.5 million was recorded in the accompanying balance sheet as of September 30, 2013. The facility fee, the warrant value on its issuance date, and other debt issuance costs were reflected as a debt discount and are being amortized to interest expense over the term of the outstanding loan using the effective interest rate method. The liability classified warrants must be remeasured at fair value on each reporting date and changes in fair value are recorded as other income, net in the accompanying statement of operations and comprehensive loss.

Commitments_and_Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	7. Commitments and Contingencies
	Operating Lease Commitments
	For the year ended December 31, 2013, the Company leased office and laboratory space in a single building in Hayward, California. The facility lease, as amended on July 15, 2010, had a term of four years, unless terminated earlier by the Company, and expired on April 30, 2014. Rent expense was $0.4 million and $0.5 million for the years ended December 31, 2014 and 2013. On November 8, 2013, the Company entered into a new lease commencing January 16, 2014, and expiring on December 31, 2018, for 8,894 square feet of office space in Newark, California.
	Future minimum lease payments under operating lease commitments are as follows (in thousands):
		Lease
		Payments
	Year ending December 31:
	2015	$	209
	2016		216
	2017		222
	2018		228
	Total future minimum payments	$	875
	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, 2014 and 2013. 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.

Redeemable_Convertible_Preferr

Redeemable Convertible Preferred Stock	12 Months Ended
	Dec. 31, 2014
Equity [Abstract]
Redeemable Convertible Preferred Stock	8. Redeemable Convertible Preferred Stock
	Upon the closing of the 2013 financing on September 30, 2013, all the outstanding shares of the Company’s redeemable convertible preferred stock were converted into 2,793,281 shares of common stock, and the related carrying value of $320.0 million was reclassified to additional paid-in capital. As of December 31, 2014 and 2013, no shares of redeemable convertible preferred stock were issued or outstanding.
	Prior to the September 30, 2013 conversion, the Company had the following series of outstanding convertible preferred stock (collectively, the Preferred Stock): Series A-1 Preferred, Series B-1 Preferred, Series C-1 Preferred, Series D-1 Preferred, Series E-1 Preferred and Series E-3 Preferred. Series E-1 Preferred and Series E-3 Preferred are collectively referred to as the Series E Preferred. The Preferred Stock was initially recorded at its original purchase price, which represented fair value on the date of issuance, net of issuance costs, if any. The original purchase price per share of Series A-1 Preferred, Series B-1 Preferred, Series C-1 Preferred, Series D-1 Preferred, and Series E Preferred was equal to $232.93, $232.93, $365.70, $232.94, and $232.93 per share, respectively. The preferred stock balances were recorded at the original fair value and the accreted dividends based on the per share terms at issuance of Series A-1 Preferred, Series B-1 Preferred, Series C-1 Preferred, Series D-1 Preferred, and Series E Preferred, which were equal to $18.64, $18.64, $29.26, $18.64, and $18.64 per share per annum, respectively.
	The shares of Series B-1 Preferred, Series D-1 Preferred, and Series E Preferred were redeemable upon the request of the holders of at least 66 2/3% of outstanding shares of Series B-1 Preferred, voting as a separate class, and 51% of outstanding shares of Series D-1 Preferred and Series E Preferred, voting together as a separate class. In this event, the Company would have been required to redeem the shares in three equal annual installments, beginning in September 2021, at the applicable original purchase price per share. All shares of Preferred Stock were redeemable in the event of a change of control at their liquidation preferences.
	As all Preferred Stock was redeemable either at the option of the holder or upon an event outside the control of the Company (i.e., a change in control), the related amounts have been presented outside of stockholders’ equity (deficit). In August and December 2003, the Company completed two closings of a private placement of Series B-1 Preferred, in which the Company issued a total of 136,520 shares at a price of $232.93 per share for gross proceeds of $31.8 million. In November and December 2004, the Company completed two further closings of Series B-1 Preferred, in which the Company issued a total of 188,894 shares at a price of $232.93 per share for gross proceeds of $44.0 million. The Series B-1 Preferred investors in these two final closings also purchased warrants for 29,245 shares of common stock at an exercise price of $30.21 per share, with an exercise period of five years from the date of purchase, for $1.51 cents per share of common stock covered by the warrants. In November 2009, the exercise period of these warrants was extended to December 31, 2011. In December 2012, the Company’s Board of Directors reduced the number of shares exercisable under these warrant by 45% of the original shares and approved the extension of the exercise period until April 1, 2013. As of December 31, 2012, warrants to purchase 13,160 shares of common stock were outstanding. In April 2013, these warrants expired in accordance with their terms.
	In August 2006, the Company issued 27,345 shares of Series C-1 Preferred to JJDC at a price of $365.70 per share, for gross proceeds of $10.0 million.
	In April 2007, the Company issued 137,592 shares of Series D-1 Preferred at a price of $232.94 per share, for gross proceeds of $32.0 million. In connection with the issuance, the Series D-1 Preferred investors also purchased warrants for an aggregate of 20,639 shares of common stock at an exercise price of $22.13 per share, with an exercise period of five years from the date of purchase, for $0.79 cents per share of common stock covered by the warrants.
	In August 2008, the Company repurchased 646, 1,610 and 472 shares of Series A-1 Preferred, Series B-1 Preferred and Series D-1 Preferred, respectively, and a warrant for 71 shares of common stock, for an aggregate purchase price of $82,000. The Company allocated the purchase price among the preferred shares and warrant based upon their respective fair values.
	In November 2009, the Company issued 1,288 shares of Series E-1 Preferred upon the conversion of debt issued under a loan agreement. In June and December 2010, the Company issued 859 and 37,119 shares of Series E-1 Preferred, respectively, upon conversion of debt issued under a loan agreement.
	In December 2010, the Company issued 71,543 shares of Series E-3 Preferred upon conversion of the JJDC convertible notes that were due in 2011.
	The significant rights, privileges and preferences of the Preferred Stock were as follows:
	Election of Directors
	Prior to the September 30, 2013 conversion, the holders of Series B-1 Preferred were entitled to elect five members of the Company’s Board of Directors, the holders of Series D-1 Preferred were entitled to elect one member of the Company’s Board of Directors, and the holders of common stock were entitled to elect one member of the Company’s Board of Directors, subject to certain restrictions. All remaining members of the Company’s Board of Directors were elected by all of the stockholders voting on an as-if-converted basis.
	Voting Rights
	Prior to the September 30, 2013 conversion, the Preferred Stock carried voting rights equal to the number of shares of common stock into which it could be converted. Additionally, certain corporate actions could only be exercised upon the approval of holders of 66 2/3% of the outstanding shares of Series B-1 Preferred and Series C-1 Preferred, voting together as a single class, and 51% of the outstanding shares of Series D-1 Preferred and Series E Preferred, voting together as a single class.
	Dividends
	All dividends were payable when and if declared by the Company’s Board of Directors. The holders of Series E Preferred were entitled to cumulative dividends in preference to the holders of Series A-1 Preferred, Series B-1 Preferred, Series C-1 Preferred, Series D-1 Preferred, and common stock. The holders of Series D-1 Preferred were entitled to cumulative dividends in preference to the holders of Series A-1 Preferred, Series B-1 Preferred, Series C-1 Preferred, and common stock. The holders of Series B-1 Preferred and Series C-1 Preferred were entitled to cumulative dividends in preference to the holders of Series A-1 Preferred and common stock. The holders of Series A-1 Preferred were entitled to cumulative dividends in preference to the holders of common stock. The dividend rate was $18.64, $18.64, $29.26, $18.64, and $18.64 per annum for each outstanding share of Series E Preferred, Series D-1 Preferred, Series C-1 Preferred, Series B-1 Preferred, and Series A-1 Preferred, respectively. Additionally, if dividends were paid to any holder of common stock, the holders of Preferred Stock would receive a dividend of a per share amount (on an as-if-converted to common stock basis) equal to the amount paid to the holders of common stock.
	Prior to the conversion of the Preferred Stock in connection with the 2013 financing, no dividends were declared and the aggregate cumulative dividends as of September 30, 2013, were $3.4 million ($47.28 per share), $1.9 million ($48.14 per share), $15.9 million ($116.00 per share), $5.6 million ($201.83 per share), $63.1 million ($168.96 per share), and $2.3 million ($183.64 per share) for Series E-3 Preferred, Series E-1 Preferred, Series D-1 Preferred, Series C-1 Preferred, Series B-1 Preferred, and Series A-1 Preferred, respectively. The aggregate cumulative dividends as of December 31, 2012, were $2.7 million ($38.04 per share), 1.5 million ($38.90 per share), $14.6 million ($106.75 per share), $5.1 million ($187.32 per share), $59.6 million ($159.72 per share), and $2.2 million ($174.40 per share) for Series E-3 Preferred, Series E-1 Preferred, Series D-1 Preferred, Series C-1 Preferred, Series B-1 Preferred, and Series A-1 Preferred, respectively.
	Liquidation Preference
	While the Preferred Stock was outstanding, in the event of a liquidation, dissolution, winding up, or change in control of the Company, the liquidation preference of each stockholder class was to be paid in the following order, from available funds: first to the holders of Series E-1 Preferred and Series E-3 Preferred, second to the holders of Series D-1 Preferred, third to the holders of Series B-1 Preferred and Series C-1 Preferred, and fourth to the holders of Series A-1 Preferred. After payment of the Preferred Stock liquidation preferences, the remaining assets of the Company were to be distributed ratably to all holders of common stock and Preferred Stock on an as-if-converted basis. The liquidation preference of Series E-1 Preferred, Series E-3 Preferred, Series D-1 Preferred, Series C-1 Preferred, Series B-1 Preferred, and Series A-1 Preferred was equal to $465.87, $290.97, $232.93, $365.70, $232.93, and $232.93 per share, respectively, plus any cumulative unpaid dividends. If there were insufficient funds available to satisfy each liquidation preference in its entirety, the holders of Preferred Stock were to be paid a pro rata amount based on their liquidation preference.
	Conversion Rights
	Each share of Preferred Stock was convertible at any time, at the option of the holder, into shares of the Company’s common stock at then applicable conversion rate. The conversion rate for each of the series of Preferred Stock was 1:1, except for the Series D-1 Preferred, which had a conversion rate of 1.365:1. With respect to the Series E Preferred, Series D-1 Preferred, Series B-1 Preferred, and Series A-1 Preferred, if the Company issued common stock or securities convertible into or exercisable for shares of common stock at a price less than the respective original purchase price per share, the conversion rate of such stock was to be adjusted to the lowest price per share paid in such issuance. The conversion rate for Preferred Stock would not be adjusted for common stock issuances on the exercise of options or warrants issued to employees, directors, or consultants of the Company and in certain other circumstances.
	Each share of Preferred Stock automatically converted into common stock upon the approval of holders of 66 2/3% of the outstanding shares of Series B-1 Preferred, voting as a separate class, and 51% of the outstanding shares of Series D-1 Preferred and Series E Preferred, voting together as a separate class, or upon the closing of an underwritten public offering of the Company’s common stock pursuant to an effective registration statement under the Securities Act of 1933, as amended, at a per share price of at least $8.00, and raising aggregate gross proceeds of at least $30.0 million. In connection with the 2013 financing each holder of the Company’s preferred stock that participated in the 2013 financing for between 1% and up to 99% of such holders “Pro Rata Share” (as defined in the Company’s then effective certificate of incorporation) had each share of preferred stock represented by such participation amount converted into four shares of common stock and the balance of any shares of preferred stock converted at the then applicable conversion rate. Any holder that participated in the 2013 financing for between 100% and 300% of such holder’s Pro Rata Share (the “Participation Multiple”) had each share of preferred stock convert into shares of common stock by multiplying the product of (y) the aggregate number of shares of preferred stock held by such holder multiplied by the applicable Participation Multiple and (z) four (4).

Common_Stock

Common Stock	12 Months Ended
	Dec. 31, 2014
Equity [Abstract]
Common Stock	9. Common Stock
	The Company was authorized to issue 100,000,000 shares of common stock as of December 31, 2014 and 2013, respectively.
	Common Stock Issuances
	On September 30, 2013, all the outstanding shares of the Company’s redeemable convertible preferred stock were converted into 2,793,281 shares of common stock and the related carrying value of $320.0 million was reclassified to additional paid-in capital.
	Commencing on September 30, 2013, the Company entered into a series of financing transactions (collectively referred to as the 2013 financing) which resulted in the issuance of common stock and warrants to purchase shares of common stock. Specifically, on September 30, 2013, the Company sold 5,366,669 shares of common stock and 1,073,338 warrants to purchase shares of common stock in a private placement for net proceeds to CymaBay of $22.8 million after deducting placement agent fees and estimated offering expenses. Also on that date, the Company issued 624,944 shares of common stock in cancellation of approximately $16.9 million of debt owed to JJDC, the holder of that debt (Note 6).
	On October 31, 2013, the Company sold an additional 664,300 shares of common stock and warrants to purchase 132,860 shares of common stock, which sales were also part of the private placement, for net proceeds to CymaBay of $2.2 million after deducting placement agent fees and estimated offering expenses.
	On November 22, 2013, the Company entered into an agreement with investors to purchase 604,000 shares of common stock and 120,800 warrants to purchase shares of common stock as part of the private placement for net proceeds of $2.7 million, which sales were set to occur shortly after the listing of the Company’s common stock on the over-the-counter market. Cymabay began trading on the over-the-counter market on January 24, 2014 enabling this portion of the financing to be completed in late January 2014.
	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, we 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. As of December 31, 2014, no shares of common stock had been sold under this facility.
	Common Stock Warrants
	In connection with 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 five-year warrants to purchase 121,739 shares of CymaBay’s common stock to its lenders at an exercise price of $5.00 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 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 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, 2014 and 2013 using a binomial lattice model and the resulting increases in fair value of $7.2 million and $0.5 million were recorded as an increase to the warrant liability and as a loss in other income (expense), net in the Company’s Statement of Operations and Comprehensive Loss.
	In November 2009, the Company’s Board of Directors approved the extension of the time period in which the holders of warrants to purchase 29,245 shares of common stock are able to exercise their warrants that were issued in connection with the issuance of Series B-1 Preferred. The exercise periods of the warrants that originally ended in November 2009 were extended to December 31, 2010. In December 2010, the Company’s Board of Directors further modified these warrants. The number of common shares exercisable under the warrants was reduced by 50% to 14,623, and the exercise period was extended to December 31, 2012. In December 2012, the Company’s Board of Directors again modified these warrants to purchase common stock. The number of shares exercisable under the warrants issued with the issuance of the Series B-1 Preferred was reduced by 45% of the original shares to 13,163, and the exercise period was extended to April 1, 2013. The extension of the agreement did not cause a material change in value. In April 2013, these warrants expired.
	In December 2010, the Company’s Board of Directors modified the warrants to purchase common stock that were issued in connection with the issuance of Series D-1 Preferred. The exercise period of the warrants issued in connection with the Series D-1 Preferred issuance was extended to April 13, 2013. The charge related to the modifications to these warrants of $0.1 million was recorded to accumulated deficit and was determined using the Black-Scholes valuation model, with the following inputs used to determine the charge related to the modification: fair value of the Company’s common stock of $15.90 per share, expected life of the modified warrants of one to two years, risk-free interest rate of 0.50%, and expected common stock price volatility of 83%. In April 2013, these warrants expired.
	Shares of Common Stock Authorized for Issuance
	As of December 31, 2014 and December 31, 2013, the Company had reserved shares of authorized but unissued common stock as follows:
		December 31,		December 31,
		2014		2013
	Common stock warrants		1,768,347		1,742,727
	Equity incentive plans		1,549,616		577,294
	Total reserved shares of common stock		3,317,963		2,320,021

Stock_Plans_and_StockBased_Com

Stock Plans and Stock-Based Compensation	12 Months Ended
	Dec. 31, 2014
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 1st of each year, for a period of not more than ten years, in an amount equal to 5% of the total number of shares of capital stock outstanding on December 31st of the preceding calendar year, unless the Board determines otherwise prior to December 31st of such calendar year. In June 2014, the Company’s stockholders approved a proposal to increase the share reserve by an additional 500,000 shares.
	Stock Plan Activity
	In December 2013, the Company’s Board of Directors modified the terms of 60,847 stock options held by employees, directors, and scientific advisors. Specifically, the exercise price for such options was reduced to $5, the fair market value of the Company’s common stock on the date of modification, and the term of each option was extended to 10 years from the date of the modification. The Company accounted for this stock option modification by recognizing any unamortized expense related to the original unmodified options as of the modification date over the remaining vesting periods of those awards. The incremental expense resulting from this modification of $0.2 million was also recognized over the remaining vesting period. As substantially all of the modified awards were fully vested on the modification date, the Company recognized $0.2 million of noncash stock-based compensation expense related to this stock option modification in December 2013.
	As of December 31, 2014, there were 311,300 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 734,805 shares on January 1, 2015.
	The following table summarizes stock option activity:
		Shares			Weighted-			Weighted-		Aggregate
		Subject to			Average			Average		Intrinsic
		Outstanding			Exercise			Remaining		Value (in
		Options			Price of			Contractual		thousands)
					Options			Term
								(Years)
	Outstanding as of December 31, 2013		577,253		$	7			9.57	$	3
	Options granted		445,950			5.44
	Options exercised		(431	)		4.82
	Options forfeited		(13,264	)		4.99
	Options expired		(18,498	)		19.39
	Outstanding as of December 31, 2014		991,010		$	6.09			8.91	$	4,559
	Vested and expected to vest as of December 31, 2014		969,087		$	6.11			8.9	$	4,466
	Exercisable as of December 31, 2014		515,908		$	6.72			8.79	$	2,461
	The following table summarizes information about stock options outstanding as of December 31, 2014:
		Options Outstanding						Options Exercisable
	Exercise Price	Number			Weighted-			Number of Shares
		of			Average
		Shares			Remaining
					Contractual
					Term
					(Years)
	$4.77		10,983			7.07			9,538
	$5.00		867,782			8.94			499,625
	$5.23		10,000			9.65			—
	$6.85		12,000			9.73			—
	$7.00		77,000			9.28			—
	$7.99		6,500			9.36			—
	$30.21		3,290			0.02			3,290
	$238.50		3,455			1.73			3,455
			991,010			8.91			515,908
	Grant Date Fair Value
	The following table presents the weighted-average assumptions the Company used with 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,
		2014			2013
	Weighted-average assumptions:
	Expected term		6 yrs			6 yrs
	Expected volatility		90	%		92	%
	Risk-free interest rate		2.02	%		1.76	%
	Expected dividend yield		0	%		0	%
	Weighted-average grant date fair value per share	$	4.06		$	3.76
	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, 2014 and 2013, 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.
	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.
	Common Stock Fair Value
	Prior to the listing of the Company’s common stock on a public exchange in January 2014, the Company’s Board of Directors historically determined the fair value of the Company’s common stock for the purpose of pricing the Company’s equity awards to employees, directors, and consultants. The Company’s Board of Directors, in making such fair value determinations, considered a number of factors, including the price at which Preferred Stock was issued to outside investors in arm’s-length transactions, the rights, preferences, and privileges of the Preferred Stock relative to the common stock, important developments relating to advancement of the Company’s technology and clinical programs, the Company’s stage of development and business strategy, the likelihood of achieving a liquidity event for the shares of common stock, such as an initial public offering or sale of the Company, prevailing market conditions, and the market prices of various publicly held life sciences companies. Additionally, the Board of Directors considered contemporaneous valuations provided by third-party valuation specialists.
	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 material for the years ended December 31, 2014 and 2013.
	Vested and Unvested Awards
	The total fair value of options vested for the years ended December 31, 2014 and 2013, was $1.0 million and $0.9 million, respectively.
	As of December 31, 2014, and 2013 the total compensation expense related to unvested employee stock options to be recognized in future periods, excluding estimated forfeitures, was $1.9 million and $1.2 million, respectively. The weighted-average periods over which this compensation expense is expected to be recognized are 3.0 years and 3.9 years as of December 31, 2014 and 2013, 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 will vest 100% on the second anniversary of their grant date and have a term of 10 years, provided, 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.
As of December 31, 2013, the Company revalued its incentive awards using the Black-Scholes option pricing model and applicable valuation inputs on that date and amortized the resulting value over the initial two year vesting period resulting in $9,000 of stock based compensation expense in the year ended December 31, 2013. A corresponding incentive award liability was recorded in other liabilities in the accompanying balance sheet as of December 31, 2013. During 2014, the Company changed its incentive award accounting from the liability to the equity method and made certain adjustments as noted above. As a result, the Company recorded $285,000 of stock based compensation expense in the year ended December 31, 2014 pertaining to its incentive awards. A corresponding equity adjustment was recorded in additional paid in capital in the accompanying balance sheet as of December 31, 2014.
Stock-Based Compensation Expense
Employee and Director Expense
Employee and director stock-based compensation expense recorded was as follows (in thousands):
	Year Ended
	December 31,
	2014			2013
Research and development	$	332		$	184
General and administrative		952			691
Total	$	1,284		$	875
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 6,833 shares of common stock, in 2014 and 2013, respectively. As of December 31, 2014, options to purchase 13,416 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 1,752 shares remained unvested as of December 31, 2014. The Company recorded $8,000 and $17,000 of expense in the years ended December 31, 2014 and 2013, respectively, related to these options and awards.

401k_Plan

401(k) Plan	12 Months Ended
	Dec. 31, 2014
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, 2014 and 2013.

Income_Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2014
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
		2014			2013
	Deferred tax assets:
	Federal and state net operating loss carryforwards	$	71,153		$	60,569
	Capitalized research and development		22,314			22,349
	Federal and state tax credit carryforwards		7,083			6,600
	Other		1,470			1,313
	Total deferred tax assets		102,020			90,831
	Valuation allowance		(102,020	)		(90,831	)
	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 $11.2 million during the year ended December 31, 2014 and decreased $1.8 million during the year ended December 31, 2013.
	The following is a reconciliation of the expected statutory federal income tax provision to the actual income tax provision (in thousands):
		December 31
		2014			2013
	Expected income tax benefit at federal statutory tax rate	$	(10,851	)	$	(3,424	)
	Net operating loss adjustments		(1,703	)		4,441
	Change in valuation allowance		11,189			(1,757	)
	State income taxes, net of federal benefit		(783	)		583
	Permanent items		2,595			555
	Research credits		(446	)		(396	)
	Other, net		(1	)		(2	)
	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, 2014 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 2008-2014, 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, 2014, we had federal net operating loss carryforwards of $181.0 million and state net operating loss carryforwards of $164.6 million to offset future taxable income, if any. In addition, we had federal research and development tax credit carry forwards of $6.7 million and state research and development tax credit carryforwards of $3.2 million. If not utilized, the federal net operating loss and tax credit carryforwards will expire beginning in 2024 through 2034 and the state net operating loss carryforwards will expire beginning in 2015 through 2034. 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
	Balance as of December 31, 2012	$	1,747
	Increases related to prior year tax positions		65
	Increases related to 2013 tax positions		53
	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
	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 2014 remain open to examination by the major taxing authorities.

RelatedParty_Transactions

Related-Party Transactions	12 Months Ended
	Dec. 31, 2014
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 and $45,000 in the years ended December 31, 2014 and 2013, respectively, in monthly cash retainers.

Subsequent_Events

Subsequent Events	12 Months Ended
	Dec. 31, 2014
Subsequent Events [Abstract]
Subsequent Events	14. Subsequent Events
	In January and February 2015, the Company utilized its $25 million at-the-market facility to complete sales of its common stock for net proceeds of approximately $4.3 million.

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Basis of Presentation and Use of Estimates	Basis of Presentation and Use of Estimates
	The 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 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, short-term marketable securities, accounts payable, accrued expenses, warrant liabilities, and forward contracts. 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.
	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 unobservable for the asset or liability.
	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, 2014 and 2013, the Company held a Level 3 liability associated with warrants, issued in connection with the Company’s equity offerings, completed in September and October 2013 as well as January 2014. The warrants are considered liabilities and are valued using a binomial option-pricing model, the significant unobservable inputs for which include exercise price of the warrants, market price of the underlying common shares, expected term, expected volatility based on a group of the Company’s peers and the risk-free rate corresponding to the expected term of the warrants. As of December 31, 2013, the Company also held a Level 3 liability associated with a forward contract which arose in connection with the Company’s November 22, 2013 execution of an equity purchase agreement with certain investors. The agreement required the Company to issue a fixed number of shares of common stock and warrants to purchase common stock at a predetermined price of $3.0 million provided the Company completes the listing of its common stock on a public stock exchange. The forward contract’s fair value was determined upon execution as the difference between the present value of the equity proceeds to be received under the agreement less the fair value of the underlying securities. The forward contract liability was recorded in the balance sheet as a component of accrued liabilities and was revalued at each reporting period until contract settlement, which occurred on January 29, 2014. The fair value of the underlying common stock and warrants were valued using an option-pricing model, the inputs of which are similar to those used in the valuation of the Company’s liability classified warrants. 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 and forward contract liabilities.
	The gains and losses from remeasurement of Level 3 financial liabilities are recorded through other income (expense), net on the accompanying statements of operations and comprehensive loss.
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 accompanying contractual maturities greater than one year from the balance sheet date are classified as short-term in the balance sheet.
	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, 2014 and 2013, cash restricted under these arrangements was $100,000 and $155,000, 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.
Contract Receivables	Contract Receivables
	Contract receivables consist of amounts due from a collaboration partner for certain reimbursable patent costs. Such expense reimbursements are presented as a reduction to general and administrative expense in the Company’s Statements of Operations and Comprehensive Loss.
Property and Equipment	Property and Equipment
	Property and equipment is stated 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, 2014 and 2013.
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 to 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.
	Equity awards granted to non-employees are accounted for 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 the 2013 financing 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 being recognized as a component of other income (expense) in the accompanying statements of operations and comprehensive loss.
Income Taxes	Income Taxes
	The Company utilizes the liability method of accounting for income taxes. Under this method, deferred tax assets and liabilities are determined based on differences between the financial reporting and the tax bases of assets and liabilities and are measured using enacted tax rates and laws that will be in effect when the differences are expected to reverse. 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 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, 2014 and 2013.
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 convertible preferred stock and stockholders’ deficit, and is stated net of related tax effects, if any.
Net Income (Loss) Per Common Share	Net Income (Loss) Per Common Share
	Basic net income (loss) per share of common stock is based on the weighted average number of shares of common stock outstanding equivalents during the period. Prior to the 2013 financing, in addition to common stock, the Company had redeemable convertible preferred stock outstanding that contractually entitled the holder to participate in dividends and earnings of the Company. Accordingly, the Company applied the two-class method for calculating net income (loss) per share. Under this method, all undistributed earnings were allocated first to the preferred stockholders based on their contractual right to dividends. This right was calculated on a pro rated basis for the portion of the period the preferred shares were outstanding. In addition, in connection with the 2013 financing, during the year ended December 31, 2013, the Company converted all outstanding redeemable convertible preferred stock into common stock. The excess of the carrying amount of such redeemable convertible preferred stock over the fair value of the consideration paid to the holders was treated as an adjustment that reduced preferred stockholders’ dividend or distribution entitlement. The amount of earnings that resulted from adjusting net loss for the period as described above was allocated between weighted average number of participating preferred and common stock shares based on their entitlement to such distributions as if all of the earnings of the period had been distributed.
	Diluted net loss per share of common stock is calculated using the more dilutive of the two approaches: one, “as-converted” method, under which the weighted average number of common stock shares outstanding during the period is adjusted to include the assumed conversion of redeemable convertible preferred stock at the beginning of the period, and the other, the “two-class” method as described above. Under either approach, the weighted average number of shares outstanding is also adjusted to include the assumed exercises of stock options and warrants, if dilutive. For periods in which the Company has basic net loss per share of common stock, such as for the year ended December 31, 2014, diluted net loss per share is the same as basic, as any adjustments would have been anti-dilutive. For the year ending December 31, 2013, the Company’s diluted net loss per common share was calculated using the “as-converted” method, as it resulted in a net loss per share of common stock and accordingly, was more dilutive than the “two-class” method.
	In all periods presented, the Company’s outstanding stock options and warrants were excluded from the calculation of earnings (loss) per share because the effect would be antidilutive.

Summary_of_Significant_Account2

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Schedule of Fair Value Assets and Liabilities Measured on Recurring Basis	The following table presents the fair value of the Company’s financial assets and liabilities using the above input categories (in thousands):
	(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
		As of December 31, 2013
	Description	Level 1			Level 2			Level 3		Fair Value
	Money market funds	$	21,097		$	—		$	—	$	21,097
	Corporate debt and asset backed securities		—			6,843			—		6,843
	Total assets measured at fair value	$	21,097		$	6,843		$	—	$	27,940
	Forward contract	$	—		$	—		$	453	$	453
	Warrant liability		—			—			6,466		6,466
	Total liabilities measured at fair value	$	—		$	—		$	6,919	$	6,919
Schedule of Changes in Fair Value of Financial Instruments	The following table sets forth a summary of the changes in the fair value of our Level 3 financial instruments (in thousands):
		Warrant			Forward
		Liability			Contract
	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		$	—
Schedule of Basic and Diluted Net Income (Loss) per Share	The following table sets forth the computation of basic and diluted net income (loss) per share (in thousands, except share and per share amounts):
		Year Ended December 31,
		2014			2013
	Basic:
	Numerator:
	Net loss	$	(31,917	)	$	(10,073	)
	Accretion to redemption value of redeemable convertible preferred stock		—			(9,289	)
	Reduction in redeemable convertible preferred stock distribution entitlement upon extinguishment		—			313,933
	Amounts allocated to participating redeemable convertible preferred stock		—			(50,577	)
	Net (loss) income allocated to common stock—basic	$	(31,917	)	$	243,994
	Denominator:
	Weighted average number of common stock shares outstanding—basic		12,048,985			2,357,036
	Net (loss) income per share-basic:	$	(2.65	)	$	103.52
	Diluted:
	Numerator:
	Net (loss) income allocated to common stock	$	(31,917	)	$	243,994
	Adjustments from assumed conversion of redeemable convertible preferred stock		—			(254,067	)
	Net loss allocated to common stock—diluted	$	(31,917	)	$	(10,073	)
	Denominator:
	Weighted average number of common stock shares outstanding		12,048,985			2,357,036
	Weighted average number of preferred stock shares outstanding		—			488,573
	Total common stock equivalent shares		12,048,985			2,845,609
	Net loss per share—diluted	$	(2.65	)	$	(3.54	)
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
		December 31,
		2014			2013
	Warrants for common stock		1,768			1,743
	Common stock options		991			577
	Incentive awards		247			—
			3,006			2,320

Marketable_Securities_Tables

Marketable Securities (Tables)	12 Months Ended
	Dec. 31, 2014
Cash and Cash Equivalents [Abstract]
Marketable Available-for-Sale Securities	Marketable available-for-sale securities as of December 31, 2014 and 2013 consist of the following (in thousands):
		Amortized		Gross		Gross			Estimated
		Cost		Unrealized		Unrealized			Fair Value
				Gains		Losses
	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
		Amortized		Gross		Gross			Estimated
		Cost		Unrealized		Unrealized			Fair Value
				Gains		Losses
	As of December 31, 2013:
	Corporate debt securities	$	6,355	$	3	$	(2	)	$	6,356
	Asset-backed securities		486		1		—			487
		$	6,841	$	4	$	(2	)	$	6,843

Certain_Balance_Sheet_Items_Ta

Certain Balance Sheet Items (Tables)	12 Months Ended
	Dec. 31, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Property and Equipment	Property and equipment consist of the following (in thousands):
		December 31,
		2014			2013
	Office and computer equipment	$	176		$	556
	Purchased software		46			166
	Furniture and fixtures		33			42
	Leasehold improvements		66			2,534
	Total		321			3,298
	Less accumulated depreciation and amortization		(235	)		(3,295	)
	Property and equipment, net	$	86		$	3
Accrued Liabilities	Accrued liabilities consist of the following (in thousands):
		December 31,
		2014			2013
	Accrued compensation	$	1,504		$	518
	Accrued pre-clinical and clinical trial expenses		1,732			418
	Accrued professional fees		73			782
	Forward contract		—			453
	Other accruals		79			80
	Total accrued liabilities	$	3,388		$	2,251

Debt_Tables

Debt (Tables)	12 Months Ended
	Dec. 31, 2014
Debt Disclosure [Abstract]
Schedule of Future Principal Payments Due under Loan Facility	Future principal payments due under the loan facility are as follows (in thousands):
		Principal
		Payments
	Year ending December 31:
	2015	$	1,546
	2016		1,687
	2017		1,522
	Total future principal payments due under loan agreement	$	4,755

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
Future Minimum Lease Payments	Future minimum lease payments under operating lease commitments are as follows (in thousands):
		Lease
		Payments
	Year ending December 31:
	2015	$	209
	2016		216
	2017		222
	2018		228
	Total future minimum payments	$	875

Common_Stock_Tables

Common Stock (Tables)	12 Months Ended
	Dec. 31, 2014
Equity [Abstract]
Reserved Shares of Authorized but Unissued Common Stock	As of December 31, 2014 and December 31, 2013, the Company had reserved shares of authorized but unissued common stock as follows:
		December 31,		December 31,
		2014		2013
	Common stock warrants		1,768,347		1,742,727
	Equity incentive plans		1,549,616		577,294
	Total reserved shares of common stock		3,317,963		2,320,021

Stock_Plans_and_StockBased_Com1

Stock Plans and Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2014
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
		Subject to			Average			Average		Intrinsic
		Outstanding			Exercise			Remaining		Value (in
		Options			Price of			Contractual		thousands)
					Options			Term
								(Years)
	Outstanding as of December 31, 2013		577,253		$	7			9.57	$	3
	Options granted		445,950			5.44
	Options exercised		(431	)		4.82
	Options forfeited		(13,264	)		4.99
	Options expired		(18,498	)		19.39
	Outstanding as of December 31, 2014		991,010		$	6.09			8.91	$	4,559
	Vested and expected to vest as of December 31, 2014		969,087		$	6.11			8.9	$	4,466
	Exercisable as of December 31, 2014		515,908		$	6.72			8.79	$	2,461
Summary of Stock Options Outstanding	The following table summarizes information about stock options outstanding as of December 31, 2014:
		Options Outstanding						Options Exercisable
	Exercise Price	Number			Weighted-			Number of Shares
		of			Average
		Shares			Remaining
					Contractual
					Term
					(Years)
	$4.77		10,983			7.07			9,538
	$5.00		867,782			8.94			499,625
	$5.23		10,000			9.65			—
	$6.85		12,000			9.73			—
	$7.00		77,000			9.28			—
	$7.99		6,500			9.36			—
	$30.21		3,290			0.02			3,290
	$238.50		3,455			1.73			3,455
			991,010			8.91			515,908
Estimated Weighted-Average Grant Date Fair Value	The following table presents the weighted-average assumptions the Company used with 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,
		2014			2013
	Weighted-average assumptions:
	Expected term		6 yrs			6 yrs
	Expected volatility		90	%		92	%
	Risk-free interest rate		2.02	%		1.76	%
	Expected dividend yield		0	%		0	%
	Weighted-average grant date fair value per share	$	4.06		$	3.76
Summary of Stock-Based Compensation Expense	Employee and director stock-based compensation expense recorded was as follows (in thousands):
		Year Ended
		December 31,
		2014			2013
	Research and development	$	332		$	184
	General and administrative		952			691
	Total	$	1,284		$	875

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2014
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
		2014			2013
	Deferred tax assets:
	Federal and state net operating loss carryforwards	$	71,153		$	60,569
	Capitalized research and development		22,314			22,349
	Federal and state tax credit carryforwards		7,083			6,600
	Other		1,470			1,313
	Total deferred tax assets		102,020			90,831
	Valuation allowance		(102,020	)		(90,831	)
	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
		2014			2013
	Expected income tax benefit at federal statutory tax rate	$	(10,851	)	$	(3,424	)
	Net operating loss adjustments		(1,703	)		4,441
	Change in valuation allowance		11,189			(1,757	)
	State income taxes, net of federal benefit		(783	)		583
	Permanent items		2,595			555
	Research credits		(446	)		(396	)
	Other, net		(1	)		(2	)
	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
	Balance as of December 31, 2012	$	1,747
	Increases related to prior year tax positions		65
	Increases related to 2013 tax positions		53
	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

Organization_and_Description_o1

Organization and Description of Business - Additional Information (Detail) (USD $)	0 Months Ended				12 Months Ended
	Jul. 25, 2014	Nov. 22, 2013	Oct. 31, 2013	Sep. 30, 2013	Dec. 31, 2014	Dec. 31, 2013	Jul. 25, 2014	Sep. 30, 2013	Aug. 31, 2006	Jun. 20, 2006
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Net loss					($31,917,000)	($10,073,000)
Cash flows from operating activities					-21,114,000	-8,458,000
Accumulated deficit					-380,759,000	-348,842,000
Gross proceeds from issuance of common stock and warrants in a private placement		2,700,000		26,800,000
Additional proceeds from venture debt financing				5,000,000		4,853,000
Venture debt financing loan agreement amount								10,000,000		30,000,000
Net proceeds after deducting placement agent fees and estimated offering expenses				28,800,000
Net proceeds from issuance of private placement			2,200,000	22,800,000
Issued shares of common stock in cancellation of debt				16,900,000
Shares issued in public offering	4,600,000
Common stock offering price							$5.50		$365.70
Net proceeds from public offering	23,000,000
Cash and cash equivalents and marketable securities					$34,800,000

Summary_of_Significant_Account3

Summary of Significant Accounting Policies - Schedule of Fair Value Assets and Liabilities Measured on Recurring Basis (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	$33,150	$27,940
Total liabilities measured at fair value	13,596	6,919
Forward contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total liabilities measured at fair value		453
Warrant liability [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total liabilities measured at fair value	13,596	6,466
Money market funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	9,941	21,097
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	23,209	6,843
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	9,941	21,097
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	9,941	21,097
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	23,209	6,843
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	23,209	6,843
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total liabilities measured at fair value	13,596	6,919
Level 3 [Member] | Forward contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total liabilities measured at fair value		453
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	$13,596	$6,466

Summary_of_Significant_Account4

Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Product Information [Line Items]
Proceeds from sale of common stock	$25,430,000	$26,514,000
Cash and cash equivalents, maturity description	90 days or less
Short-term contractual maturities	1 year
Restricted cash	100,000	155,000
Impairment losses	0	0
Interest or penalties related to income taxes	0	0
Warrants, Exercise price of $5.75 per share [Member]
Product Information [Line Items]
Proceeds from sale of common stock	$3,000,000
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_Account5

Summary of Significant Accounting Policies - Schedule of Changes in Fair Value of Financial Instruments (Detail) (Level 3 [Member], USD $)	12 Months Ended
In Thousands, unless otherwise specified	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	$6,466
Issuance of financial instrument	443
Change in fair value	7,236
Settlement of financial instrument	-549
Balance as of December 31, 2014	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
Balance as of December 31, 2014	$0

Summary_of_Significant_Account6

Summary of Significant Accounting Policies - Schedule of Basic and Diluted Net Income (Loss) per Share (Detail) (USD $)	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Basic:
Net loss	($31,917)	($10,073)
Accretion to redemption value of redeemable convertible preferred stock		-9,289
Reduction in redeemable convertible preferred stock distribution entitlement upon extinguishment		313,933
Amounts allocated to participating redeemable convertible preferred stock		-50,577
Net (loss) income allocated to common stock-basic	-31,917	243,994
Weighted average number of common stock shares outstanding-basic	12,048,985	2,357,036
Net (loss) income per share-basic:	($2.65)	$103.52
Diluted:
Net (loss) income allocated to common stock	-31,917	243,994
Adjustments from assumed conversion of redeemable convertible preferred stock		-254,067
Net loss allocated to common stock-diluted	($31,917)	($10,073)
Total common stock equivalent shares	12,048,985	2,845,609
Net loss per share-diluted	($2.65)	($3.54)
Common Stock [Member]
Diluted:
Total common stock equivalent shares	12,048,985	2,357,036
Preferred Stock [Member]
Diluted:
Total common stock equivalent shares		488,573

Summary_of_Significant_Account7

Summary of Significant Accounting Policies - Anti-Dilutive Securities Excluded from the Computation of Diluted Net Loss per Share (Detail)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the computation of diluted loss per share	3,006	2,320
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	1,768	1,743
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	991	577
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	247

Marketable_Securities_Marketab

Marketable Securities - Marketable Available-for-Sale Securities (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$23,222	$6,841
Gross Unrealized Gains	1	4
Gross Unrealized Losses	-14	-2
Estimated Fair Value	23,209	6,843
Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	19,706	6,355
Gross Unrealized Gains	1	3
Gross Unrealized Losses	-14	-2
Estimated Fair Value	19,693	6,356
Asset-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,516	486
Gross Unrealized Gains		1
Estimated Fair Value	$3,516	$487

Marketable_Securities_Addition

Marketable Securities - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable securities contractual maturities	Less than one year
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable investments continuous unrealized loss position	0	$0
Asset-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable securities contractual maturities	Between 2-5 years

Certain_Balance_Sheet_Items_Pr

Certain Balance Sheet Items - Property and Equipment (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$321	$3,298
Less accumulated depreciation and amortization	-235	-3,295
Property and equipment, net	86	3
Office and computer equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	176	556
Purchased software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	46	166
Furniture and fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	33	42
Leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$66	$2,534

Certain_Balance_Sheet_Items_Ac

Certain Balance Sheet Items - Accrued Liabilities (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Statement of Financial Position [Abstract]
Accrued compensation	$1,504	$518
Accrued pre-clinical and clinical trial expenses	1,732	418
Accrued professional fees	73	782
Forward contract		453
Other accruals	79	80
Total accrued liabilities	$3,388	$2,251

Collaboration_and_License_Agre1

Collaboration and License Agreements - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Jun. 30, 1998
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
License agreement date	30-Jun-98
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]
Collaboration agreement date	30-Jun-06
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	30-Jun-10
Number of development and license agreements	2
Contingent payment eligible to receive on development and commercial events	$228,000,000

Debt_Additional_Information_De

Debt - Additional Information (Detail) (USD $)

0 Months Ended

12 Months Ended

1 Months Ended

12 Months Ended

Sep. 30, 2013

Dec. 31, 2013

Mar. 31, 2008

Sep. 30, 2008

Feb. 28, 2009

Jul. 31, 2013

Mar. 31, 2013

Jan. 31, 2012

Jul. 31, 2009

Dec. 31, 2014

Jun. 20, 2006

Dec. 31, 2010

Debt Instrument [Line Items]

Maximum borrowing capacity

$10,000,000

$30,000,000

Interest expense

600,000

Loan facility, outstanding principal and accrued interest settled

16,900,000

Loan facility extinguished in exchange of common stock

624,944

Facility loan, drawn

5,000,000

4,853,000

Facility fee

1.00%

Series E-1 Preferred [Member]

Debt Instrument [Line Items]

Conversion price

$232.93

Series C-1 Preferred [Member]

Debt Instrument [Line Items]

Conversion price

$438.84

$438.84

Series C-1 Preferred [Member] | As Amended [Member]

Debt Instrument [Line Items]

Conversion price

292.56

First Issuance [Member]

Debt Instrument [Line Items]

Notes issued

3,500,000

Maturity date of debt

17-Mar-11

Facility loan, fixed interest rate

7.57%

Second Issuance [Member]

Debt Instrument [Line Items]

Notes issued

10,500,000

Maturity date of debt

17-Sep-11

Facility loan, fixed interest rate

7.57%

Third Issuance [Member]

Debt Instrument [Line Items]

Notes issued

7,000,000

Maturity date of debt

28-Feb-12

Facility loan, fixed interest rate

4.42%

Third Issuance [Member] | As Amended [Member]

Debt Instrument [Line Items]

Maturity date of debt

31-Dec-13

1-Aug-13

1-Mar-13

Facility loan, fixed interest rate

4.92%

Fourth Issuance [Member]

Debt Instrument [Line Items]

Notes issued

6,700,000

Maturity date of debt

31-Jul-12

Facility loan, fixed interest rate

4.96%

Fourth Issuance [Member] | As Amended [Member]

Debt Instrument [Line Items]

Maturity date of debt

31-Dec-13

1-Aug-13

1-Mar-13

Facility loan, fixed interest rate

5.46%

Facility Loan Agreement [Member]

Debt Instrument [Line Items]

Maximum borrowing capacity

10,000,000

Facility loan, interest amortization period

36 months

Percentage of principal amount as final payment

6.50%

Facility loan, financial covenants

Company must maintain compliance with one of two financial covenants at all times (1) maintain 1.3 times cash to outstanding debt or (2) maintain sufficient cash on hand to support eight months of operations based on a trailing average monthly cash burn.

Aggregate outstanding term loans percentage

100.00%

Prepayment fee percentage

3.00%

Facility Loan Agreement [Member] | First Tranche [Member]

Debt Instrument [Line Items]

Facility loan, fixed interest rate

8.75%

Facility loan, drawn

5,000,000

Facility Loan Agreement [Member] | Second Tranche [Member]

Debt Instrument [Line Items]

Facility loan, drawn

5,000,000

Facility Loan Agreement [Member] | Scenario one, conversion basis [Member] | Second Tranche [Member]

Debt Instrument [Line Items]

Facility loan, fixed interest rate

8.75%

Facility Loan Agreement [Member] | Scenario two [Member] | Second Tranche [Member] | Wall Street Journal Prime Rate [Member]

Debt Instrument [Line Items]

Facility loan, prime rate plus

4.25%

Warrants, Exercise price of $5.00 per share [Member]

Debt Instrument [Line Items]

Warrants issued

121,739

Exercise price

$5

$5

Long term warrant liability

$500,000

Debt_Schedule_of_Future_Princi

Debt - Schedule of Future Principal Payments Due under Loan Facility (Detail) (USD $)	Dec. 31, 2014
In Thousands, unless otherwise specified
Maturities of Long-term Debt [Abstract]
2015	$1,546
2016	1,687
2017	1,522
Total future principal payments due under loan agreement	$4,755

Commitments_and_Contingencies_1

Commitments and Contingencies - Additional Information (Detail) (USD $)	12 Months Ended		0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Nov. 08, 2013
			sqft
Loss Contingencies [Line Items]
Rent expenses	$400,000	$500,000
Operating leases term		4 years
Lease expiration date		30-Apr-14
Accrued in the balance sheets related to indemnification obligations	0
Indemnification liabilities	$0	$0
New Lease Agreement [Member]
Loss Contingencies [Line Items]
Lease start date			16-Jan-14
Lease expiration date			31-Dec-18
Area of office space			8,894

Commitments_and_Contingencies_2

Commitments and Contingencies - Future Minimum Lease Payments (Detail) (USD $)	Dec. 31, 2014
In Thousands, unless otherwise specified
Commitments and Contingencies Disclosure [Abstract]
2015	$209
2016	216
2017	222
2018	228
Total future minimum payments	$875

Redeemable_Convertible_Preferr1

Redeemable Convertible Preferred Stock - Additional Information (Detail) (USD $)	0 Months Ended	1 Months Ended		12 Months Ended			1 Months Ended	2 Months Ended	4 Months Ended	9 Months Ended	12 Months Ended	1 Months Ended
	Sep. 30, 2013	Aug. 31, 2008	Aug. 31, 2006	Dec. 31, 2013	Dec. 31, 2010	Dec. 31, 2014	Nov. 30, 2009	Dec. 31, 2004	Dec. 31, 2003	Sep. 30, 2013	Dec. 31, 2012	Apr. 30, 2007	Dec. 31, 2010	Jun. 30, 2010	Jul. 25, 2014
Temporary Equity [Line Items]
Issuance of common stock upon conversion of redeemable convertible preferred stock	2,793,281
Conversion of preferred stock to common stock	$320,000,000			$323,155,000
Convertible preferred stock issued			27,345	0		0
Convertible preferred stock outstanding				0		0
Purchase price per share of preferred stock			$365.70												$5.50
Proceed from issuance of redeemable preferred stock			10,000,000
Percentage of reduction in number of shares exercisable					50.00%
Number of warrants outstanding					14,623								14,623
Repurchase of Stock, value		82,000		-8,247,000
Dividends declared	0									0
Next sale and issuance of capital stock of the Company [Member]
Temporary Equity [Line Items]
Participation right, description						Any holder that participated in the 2013 financing for between 100% and 300% of such holder's Pro Rata Share (the "Participation Multiple") had each share of preferred stock convert into shares of common stock by multiplying the product of (y) the aggregate number of shares of preferred stock held by such holder multiplied by the applicable Participation Multiple and (z) four (4).
Scenario two [Member] | Minimum [Member]
Temporary Equity [Line Items]
Per share price						8
Aggregate gross proceed						30,000,000
Scenario two [Member] | Next sale and issuance of capital stock of the Company [Member]
Temporary Equity [Line Items]
Conversion ratio						0.25
Scenario two [Member] | Next sale and issuance of capital stock of the Company [Member] | Minimum [Member]
Temporary Equity [Line Items]
Participation percentage in financing						1.00%
Scenario two [Member] | Next sale and issuance of capital stock of the Company [Member] | Maximum [Member]
Temporary Equity [Line Items]
Participation percentage in financing						99.00%
Series B-1 Preferred [Member]
Temporary Equity [Line Items]
Convertible preferred stock issued								188,894	136,520
Purchase price per share of preferred stock						232.93		$232.93	$232.93
Preferred stock balances, price per share						18.64
Proceed from issuance of redeemable preferred stock								44,000,000	31,800,000
Issued warrants to purchase common stock							29,245	29,245
Warrant issued, exercise price per share								$30.21
Common stock, price per share								$1.51
warrant issued, exercise period								5 years
Warrant, extended expiration date							31-Dec-11				1-Apr-13
Percentage of reduction in number of shares exercisable											45.00%
Number of warrants outstanding											13,160
Repurchase of Stock, shares		1,610
Aggregate cumulative dividend										63,100,000	59,600,000
Aggregate cumulative dividend, per share										$168.96	$159.72
Preferred stock liquidation preference						232.93
Series A-1 Preferred [Member]
Temporary Equity [Line Items]
Purchase price per share of preferred stock						232.93
Preferred stock balances, price per share						18.64
Repurchase of Stock, shares		646
Aggregate cumulative dividend										2,300,000	2,200,000
Aggregate cumulative dividend, per share										$183.64	$174.40
Preferred stock liquidation preference						232.93
Series C-1 Preferred [Member]
Temporary Equity [Line Items]
Purchase price per share of preferred stock						365.7
Preferred stock balances, price per share						29.26
Aggregate cumulative dividend										5,600,000	5,100,000
Aggregate cumulative dividend, per share										$201.83	$187.32
Preferred stock liquidation preference						365.7
Series D-1 Preferred [Member]
Temporary Equity [Line Items]
Convertible preferred stock issued												137,592
Purchase price per share of preferred stock						232.94						$232.94
Preferred stock balances, price per share						18.64
Proceed from issuance of redeemable preferred stock												32,000,000
Issued warrants to purchase common stock												20,639
Warrant issued, exercise price per share												$22.13
Common stock, price per share												$0.79
warrant issued, exercise period												5 years
Warrant, extended expiration date					13-Apr-13
Repurchase of Stock, shares		472
Aggregate cumulative dividend										15,900,000	14,600,000
Aggregate cumulative dividend, per share										$116	$106.75
Preferred stock liquidation preference						232.93
Series E-1 Preferred [Member]
Temporary Equity [Line Items]
Purchase price per share of preferred stock						232.93
Preferred stock balances, price per share						18.64
Shares issued upon conversion of debt							1,288						37,119	859
Aggregate cumulative dividend										1,900,000	1,500,000
Aggregate cumulative dividend, per share										$48.14	$38.90
Preferred stock liquidation preference						465.87
Warrants [Member]
Temporary Equity [Line Items]
Repurchase of Stock, shares		71
Series E-3 Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Shares issued upon conversion of debt					71,543
Aggregate cumulative dividend										$3,400,000	$2,700,000
Aggregate cumulative dividend, per share										$47.28	$38.04
Preferred stock liquidation preference						290.97
Series B-1 Preferred Stock [Member] | Scenario one, conversion basis [Member]
Temporary Equity [Line Items]
Conversion basis, Percentage of outstanding common stock						66.67%
Series D-1 and E Preferred Stock [Member] | Scenario one, conversion basis [Member]
Temporary Equity [Line Items]
Conversion basis, Percentage of outstanding common stock						51.00%

Common_Stock_Additional_Inform

Common Stock - Additional Information (Detail) (USD $)

0 Months Ended

12 Months Ended

1 Months Ended

12 Months Ended

Jul. 25, 2014

Nov. 22, 2013

Oct. 31, 2013

Sep. 30, 2013

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2010

Nov. 30, 2009

Dec. 31, 2012

Nov. 07, 2014

Aug. 31, 2006

Dec. 31, 2004

Dec. 31, 2003

Apr. 30, 2007

Class of Stock [Line Items]

Common stock, shares authorized

100,000,000

100,000,000

Issuance of common stock upon conversion of redeemable convertible preferred stock

2,793,281

Conversion of preferred stock to common stock

$320,000,000

$323,155,000

Common stock shares sold

604,000

664,300

5,366,669

14,696,108

9,455,064

Warrants to purchase shares of common stock in private placement

120,800

132,860

1,073,338

Net proceeds from issuance of private placement

2,200,000

22,800,000

Loan facility extinguished in exchange of common stock

624,944

Amount of debt cancelled upon issuance of common stock shares

16,900,000

Net proceeds from issuance of private placement

2,700,000

26,800,000

Common stock shares sold

4,600,000

Common stock offering price

$5.50

$365.70

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

Change in fair value of warrant liability

7,236,000

494,000

Percentage of reduction in number of shares exercisable

50.00%

Number of warrants outstanding

14,623

Warrants, Exercise price of $5.75 per share [Member]

Class of Stock [Line Items]

Issued warrants to purchase common stock

1,741,788

Exercise of 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 of price of common stock

$5

$5

Warrant term

5 years

At The Market Facility [Member]

Class of Stock [Line Items]

Common stock shares sold

0

Series B-1 Preferred [Member]

Class of Stock [Line Items]

Common stock offering price

$232.93

$232.93

$232.93

Issued warrants to purchase common stock

29,245

29,245

Exercise of price of common stock

$30.21

Warrant, extended expiration date

31-Dec-11

1-Apr-13

Percentage of reduction in number of shares exercisable

45.00%

Number of warrants outstanding

13,160

Share price per share

$1.51

Series B-1 Preferred [Member] | Period One [Member]

Class of Stock [Line Items]

Warrant, extended expiration date

31-Dec-10

Series B-1 Preferred [Member] | Scenario, Previously Reported [Member]

Class of Stock [Line Items]

Percentage of reduction in number of shares exercisable

45.00%

Number of warrants outstanding

13,163

Series D-1 Preferred [Member]

Class of Stock [Line Items]

Common stock offering price

$232.94

$232.94

Issued warrants to purchase common stock

20,639

Exercise of price of common stock

$22.13

Change in fair value of warrant liability

100,000

Warrant, extended expiration date

13-Apr-13

Share price per share

$0.79

Series D-1 Preferred [Member] | Warrants [Member]

Class of Stock [Line Items]

Share price per share

15.9

Risk-free interest rate

0.50%

Volatility price

83.00%

Series D-1 Preferred [Member] | Warrants [Member] | Minimum [Member]

Class of Stock [Line Items]

Expected life

1 year

Series D-1 Preferred [Member] | Warrants [Member] | Maximum [Member]

Class of Stock [Line Items]

Expected life

2 years

Common_Stock_Reserved_Shares_o

Common Stock - Reserved Shares of Authorized but Unissued Common Stock (Detail)	Dec. 31, 2014	Dec. 31, 2013
Class of Stock [Line Items]
Total reserved shares of common stock	3,317,963	2,320,021
Warrants for common stock [Member]
Class of Stock [Line Items]
Total reserved shares of common stock	1,768,347	1,742,727
Equity incentive plans [Member]
Class of Stock [Line Items]
Total reserved shares of common stock	1,549,616	577,294

Stock_Plans_and_StockBased_Com2

Stock Plans and Stock-Based Compensation - Additional Information (Detail) (USD $)	12 Months Ended		1 Months Ended			0 Months Ended	12 Months Ended	0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2013	Jun. 30, 2014	Sep. 30, 2013	Jan. 01, 2015	Dec. 31, 2007	Jun. 03, 2014	Dec. 31, 2010	Apr. 30, 2014	Jan. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares, Outstanding	991,010	577,253	577,253
Allocated share-based compensation expense	$1,284,000	$875,000
Expected dividend yield	0.00%	0.00%
Fair value of options vested	1,000,000	900,000
Share based compensation, stock option, unamortized expense	1,900,000	1,200,000	1,200,000
Share based compensation, stock option, unamortized expense vesting period	3 years	3 years 10 months 24 days
Share reserved for issue	3,317,963	2,320,021	2,320,021
Conversion of incentive award from liability to equity accounting	121,000	16,945,000
Options to purchase common stock, unvested									14,623
Stock Plan Activity [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
Number of shares, Outstanding		60,847	60,847
Change in exercise price			$5
Stock option, Incremental expense resulting from modification			200,000
Allocated share-based compensation expense			200,000
Scientific Advisors and Consultants [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation arrangement by share based payment award, expiration period	10 years
Share based compensation arrangement by share based payment award, award vesting period	60 months
Allocated share-based compensation expense	8,000	17,000
Options to purchase common stock	10,000	6,833	6,833
Options to purchase common stock, unvested	13,416
Incentive award issued		2,335
Incentive awards outstanding, Unvested		1,752	1,752
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	311,300
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						734,805
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	4 years							2 years
Allocated share-based compensation expense	285,000	9,000
Share reserved for issue		252,752	252,752							252,752	252,752
Exercisable weighted average price per share		$5.21	$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
Incentive Awards [Member] | Black-Scholes option pricing model [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation arrangement by share based payment award, award vesting period		2 years
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_StockBased_Com3

Stock Plans and Stock-Based Compensation - Summary of Stock Option Activity (Detail) (USD $)	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Shares Subject to Outstanding Options
Outstanding at the beginning of period	577,253
Options granted	445,950
Options exercised	-431
Options forfeited	-13,264
Options expired	-18,498
Outstanding as end of period	991,010	577,253
Vested and expected to vest	969,087
Exercisable	515,908
Weighted-Average Exercise Price of Options
Outstanding at the beginning of period	$7
Options granted	$5.44
Options exercised	$4.82
Options forfeited	$4.99
Options expired	$19.39
Outstanding as end of period	$6.09	$7
Vested and expected to vest	$6.11
Exercisable	$6.72
Weighted-Average Remaining Contractual Term (Years)
Outstanding	8 years 10 months 28 days	9 years 6 months 26 days
Vested and expected to vest	8 years 10 months 24 days
Exercisable	8 years 9 months 15 days
Aggregate Intrinsic Value (In Thousands)
Outstanding at the beginning of period	$3
Outstanding as end of period	4,559	3
Vested and expected	4,466
Exercisable	$2,461

Stock_Plans_and_StockBased_Com4

Stock Plans and Stock-Based Compensation - Summary of Stock Options Outstanding (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option Outstanding Number of Shares	991,010
Weighted-Average Remaining Contractual Term (Years)	8 years 10 months 28 days
Options Exercisable Number of Shares	515,908
$4.77 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Price	4.77
Option Outstanding Number of Shares	10,983
Weighted-Average Remaining Contractual Term (Years)	7 years 26 days
Options Exercisable Number of Shares	9,538
$5.00 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Price	5
Option Outstanding Number of Shares	867,782
Weighted-Average Remaining Contractual Term (Years)	8 years 11 months 9 days
Options Exercisable Number of Shares	499,625
$5.23 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Price	5.23
Option Outstanding Number of Shares	10,000
Weighted-Average Remaining Contractual Term (Years)	9 years 7 months 24 days
$6.85 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Price	6.85
Option Outstanding Number of Shares	12,000
Weighted-Average Remaining Contractual Term (Years)	9 years 8 months 23 days
$7.00 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Price	7
Option Outstanding Number of Shares	77,000
Weighted-Average Remaining Contractual Term (Years)	9 years 3 months 11 days
$7.99 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Price	7.99
Option Outstanding Number of Shares	6,500
Weighted-Average Remaining Contractual Term (Years)	9 years 4 months 10 days
$30.21 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Price	30.21
Option Outstanding Number of Shares	3,290
Weighted-Average Remaining Contractual Term (Years)	7 days
Options Exercisable Number of Shares	3,290
$238.50 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Price	238.5
Option Outstanding Number of Shares	3,455
Weighted-Average Remaining Contractual Term (Years)	1 year 8 months 23 days
Options Exercisable Number of Shares	3,455

Stock_Plans_and_StockBased_Com5

Stock Plans and Stock-Based Compensation - Estimated Weighted-Average Grant Date Fair Value (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Expected term	6 years	6 years
Expected volatility	90.00%	92.00%
Risk-free interest rate	2.02%	1.76%
Expected dividend yield	0.00%	0.00%
Weighted-average grant date fair value per share	$4.06	$3.76

Stock_Plans_and_StockBased_Com6

Stock Plans and Stock-Based Compensation - Summary of Stock-Based Compensation Expense (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$1,284,000	$875,000
Research and development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	332,000	184,000
General and administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$952,000	$691,000

Income_Taxes_Additional_Inform

Income Taxes - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Income Tax [Line Items]
Provision for income taxes	$0	$0
Net valuation allowance change	11,200,000	-1,800,000
Cumulative change in ownership	50.00%
Cumulative change in ownership period	3 years
Significant change to its unrecognized tax benefits over the next twelve months	0
Income tax examination years	The tax years 1998 through 2014 remain open to examination by the major taxing authorities.
Domestic Tax Authority [Member]
Income Tax [Line Items]
Net operating loss carryforward	181,000,000
Research and development tax credit carry forwards	6,700,000
Domestic Tax Authority [Member] | Minimum [Member]
Income Tax [Line Items]
NOL carry forward expiry date	2024
Domestic Tax Authority [Member] | Maximum [Member]
Income Tax [Line Items]
NOL carry forward expiry date	2034
State and Local Jurisdiction [Member]
Income Tax [Line Items]
Net operating loss carryforward	164,600,000
Research and development tax credit carry forwards	$3,200,000
State and Local Jurisdiction [Member] | Minimum [Member]
Income Tax [Line Items]
NOL carry forward expiry date	2015
State and Local Jurisdiction [Member] | Maximum [Member]
Income Tax [Line Items]
NOL carry forward expiry date	2034

Income_Taxes_Components_of_Def

Income Taxes - Components of Deferred Tax Assets (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Deferred tax assets:
Federal and state net operating loss carryforwards	$71,153	$60,569
Capitalized research and development	22,314	22,349
Federal and state tax credit carryforwards	7,083	6,600
Other	1,470	1,313
Total deferred tax assets	102,020	90,831
Valuation allowance	-102,020	-90,831
Net deferred tax assets	$0	$0

Income_Taxes_Summary_of_Reconc

Income Taxes - Summary of Reconciliation of Expected Statutory Federal Income Tax Provision to Actual Income Tax Provision (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Expected income tax benefit at federal statutory tax rate	($10,851)	($3,424)
Net operating loss adjustments	-1,703	4,441
Change in valuation allowance	11,189	-1,757
State income taxes, net of federal benefit	-783	583
Permanent items	2,595	555
Research credits	-446	-396
Other, net	-1	-2
Income tax (benefit) expense	$0	$0

Income_Taxes_Summary_of_Gross_

Income Taxes - Summary of Gross Unrecognized Tax Benefits (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Balance at beginning of period	$1,865	$1,747
Increases related to prior year tax positions		65
Increases related to tax positions	126	53
Balance at end of period	$1,991	$1,865

RelatedParty_Transactions_Addi

Related-Party Transactions - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Related Party Transactions [Abstract]
Advisory fee paid to related party	$60,000	$45,000

Subsequent_Events_Additional_I

Subsequent Events - Additional Information (Detail) (USD $)	12 Months Ended		2 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Feb. 28, 2015	Nov. 07, 2014
Subsequent Event [Line Items]
Registration statement, sale of common stock				$25,000,000
Net proceeds from sale of common stock	25,430,000	26,514,000
Subsequent Event [Member]
Subsequent Event [Line Items]
Registration statement, sale of common stock			25,000,000
Net proceeds from sale of common stock			$4,300,000