Otonomy (OTIC) S-1/A 21 Jan 15 IPO registration (amended) Financial data

Document_and_Entity_Informatio

Document and Entity Information	9 Months Ended
	Sep. 30, 2014
Document And Entity Information [Abstract]
Document Type	S-1/A
Amendment Flag	FALSE
Document Period End Date	30-Sep-14
Trading Symbol	OTIC
Entity Registrant Name	Otonomy, Inc.
Entity Central Index Key	1493566
Entity Filer Category	Non-accelerated Filer

Condensed_Balance_Sheets

Condensed Balance Sheets (USD $)	Sep. 30, 2014	Dec. 31, 2013		Dec. 31, 2012
In Thousands, unless otherwise specified
Current assets:
Cash	$165,155	$37,284		$4,663
Restricted cash		75		50
Prepaid and other current assets	2,177	1,654		697
Total current assets	167,332	39,013		5,410
Property and equipment, net	952	683		439
Other long-term assets	41	61		55
Total assets	168,325	39,757		5,904
Current liabilities:
Accounts payable	1,748	2,014		1,134
Accrued expenses	2,486	384		315
Accrued compensation	1,254	244		184
Current portion of deferred rent	83	73		51
Total current liabilities	5,571	2,715		1,684
Convertible preferred stock warrant liability		646	[1]	2,909	[2]
Convertible notes payable and accrued interest, net of debt discount				7,065
Deferred rent, net of current portion	156	220		266
Total liabilities	5,727	3,581		11,924
Commitments and Contingencies
Stockholders' (deficit) equity:
Preferred stock, $0.001 par value, no shares authorized at December 31, 2012 and December 31, 2013; 10,000,000 shares authorized at September 30, 2014 (unaudited); no shares issued or outstanding at December 31, 2012, December 31, 2013 and September 30, 2014 (unaudited)
Common stock, $0.001 par value; 4,707,053 shares authorized at December 31, 2012; 11,851,717 shares authorized at December 31, 2013 and 200,000,000 shares authorized at September 30, 2014 (unaudited); 73,697 shares issued and outstanding at December 31, 2012; 75,325 shares issued and outstanding as of December 31, 2013 and 21,172,221 shares issued and outstanding at September 30, 2014 (unaudited)	21
Additional paid-in capital	255,252	580		392
Accumulated deficit	-92,675	-59,557		-39,459
Total stockholders' (deficit) equity	162,598	-58,977		-39,067
Total liabilities, convertible preferred stock, and stockholders' (deficit) equity	168,325	39,757		5,904
Series A Convertible Preferred Stock [Member]
Convertible preferred stock
Convertible preferred stock		10,561		10,559
Series B Convertible Preferred Stock [Member]
Convertible preferred stock
Convertible preferred stock		23,007		22,488
Series C Convertible Preferred Stock [Member]
Convertible preferred stock
Convertible preferred stock		$61,585
[1]	Convertible preferred stock warrant liabilities to purchase Series A and Series C convertible preferred stock at December 31, 2013 are classified as Level 3 and are measured using a hybrid of the option pricing model and the PWERM on each reporting date.
[2]	Convertible preferred stock warrant liabilities to purchase Series A and Series C convertible preferred stock at December 31, 2012 are classified as Level 3 and were measured at fair value using the Black-Scholes-Merton option pricing model.

Condensed_Balance_Sheets_Paren

Condensed Balance Sheets (Parenthetical) (USD $)	Sep. 30, 2014	Dec. 31, 2013	Dec. 31, 2012
In Thousands, except Share data, unless otherwise specified
Preferred stock, par value	$0.00	$0.00	$0.00
Preferred stock, authorized	0	9,519,809	3,575,085
Preferred stock, shares issued		9,087,965	2,047,939
Preferred stock, shares outstanding		9,087,965	2,047,939
Preferred stock, liquidation preference		$110,824	$49,531
Preferred stock, par value	$0.00	$0.00	$0.00
Preferred stock, shares authorized	10,000,000	0	0
Preferred stock, shares issued	0	0	0
Preferred stock, shares outstanding	0	0	0
Common stock, par value	$0.00	$0.00	$0.00
Common stock, shares authorized	200,000,000	11,851,717	4,707,053
Common stock, shares Issued	21,172,221	75,325	73,697
Common stock, Shares outstanding	21,172,221	75,325	73,697
Series A Convertible Preferred Stock [Member]
Preferred stock, authorized	0	404,671	406,712
Preferred stock, shares issued	0	339,863	339,863
Preferred stock, shares outstanding	0	339,863	339,863
Preferred stock, liquidation preference	0	2,987	13,209
Series B Convertible Preferred Stock [Member]
Preferred stock, authorized	0	1,708,076	3,168,373
Preferred stock, shares issued	0	1,708,076	1,708,076
Preferred stock, shares outstanding	0	1,708,076	1,708,076
Preferred stock, liquidation preference	0	15,014	36,322
Series C Convertible Preferred Stock [Member]
Preferred stock, authorized	0	7,407,062	0
Preferred stock, shares issued	0	7,040,026
Preferred stock, shares outstanding	0	7,040,026
Preferred stock, liquidation preference	$0	$92,823

Condensed_Statements_of_Operat

Condensed Statements of Operations and Comprehensive Loss (USD $)	9 Months Ended		12 Months Ended
In Thousands, except Share data, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Dec. 31, 2012
Operating expenses:
Research and development	$24,616	$9,698	$16,336	$8,523
General and administrative	5,169	2,284	3,514	2,408
Total operating expenses	29,785	11,982	19,850	10,931
Loss from operations	-29,785	-11,982	-19,850	-10,931
Other income (expense):
Interest expense	-39	-2,524	-2,528	-444
Change in fair value of convertible preferred stock warrant liability	-3,300	2,713	2,833	100
Change in fair value of convertible preferred stock purchase right				3,707
Other income (expense), net	41	-9	-14	-1
Total other income (expense)	-3,298	180	291	3,362
Net loss and comprehensive loss	-33,083	-11,802	-19,559	-7,569
Accretion to redemption value of convertible preferred stock	-35	-526	-539	-801
Net loss attributable to common stockholders	($33,118)	($12,328)	($20,098)	($8,370)
Net loss per share attributable to common stockholders, basic and diluted	($9.83)	($165.29)	($268.79)	($118.99)
Weighted-average shares used to compute net loss per share attributable to common stockholders, basic and diluted	3,369,437	74,585	74,772	70,343

Statement_of_Shareholders_Equi

Statement of Shareholders' Equity (USD $)	Total	IPO [Member]	Series A Convertible Preferred Stock [Member]	Series B Convertible Preferred Stock [Member]	Series C Convertible Preferred Stock [Member]	Series D Convertible Preferred Stock [Member]	Common stock [Member]	Common stock [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]
In Thousands, except Share data								IPO [Member]		IPO [Member]
Beginning balance at Dec. 31, 2011			$10,556	$21,690
Beginning balance at Dec. 31, 2011	-30,891								198		-31,089
Beginning balance, shares at Dec. 31, 2011							72,631
Beginning balance, shares at Dec. 31, 2011			339,863	1,708,076
Issuance of common stock upon exercise of stock options	3								3
Issuance of common stock upon exercise of stock options, shares							1,066
Stock-based compensation expense	191								191
Accretion to redemption value of convertible preferred stock	-801		3	798							-801
Net loss	-7,569										-7,569
Ending balance at Dec. 31, 2012			10,559	22,488
Ending balance at Dec. 31, 2012	-39,067								392		-39,459
Ending balance, shares at Dec. 31, 2012							73,697
Ending balance, shares at Dec. 31, 2012	2,047,939		339,863	1,708,076
Issuance of stock, net of issuance costs					61,567
Issuance of stock, shares					7,040,026
Issuance of common stock upon exercise of stock options	5								5
Issuance of common stock upon exercise of stock options, shares	2,000						1,628
Stock-based compensation expense	183								183
Accretion to redemption value of convertible preferred stock	-539		2	519	18						-539
Net loss	-19,559										-19,559
Ending balance at Dec. 31, 2013			10,561	23,007	61,585
Ending balance at Dec. 31, 2013	-58,977								580		-59,557
Ending balance, shares at Dec. 31, 2013							75,325
Ending balance, shares at Dec. 31, 2013	9,087,965		339,863	1,708,076	7,040,026
Issuance of stock, net of issuance costs		104,126				49,239		7		104,119
Issuance of stock, shares						4,126,080		7,187,500
Issuance of common stock upon exercise of stock options	98								98
Issuance of common stock upon exercise of stock options, shares	61,000						60,925
Issuance of common stock upon exercise of warrants	1,201								1,201
Issuance of common stock upon exercise of warrants, shares							228,902
Conversion of convertible preferred stock into common stock	144,427		-10,561	-23,007	-61,616	-49,243	14		144,413
Conversion of convertible preferred stock into common stock, shares			-339,863	-1,708,076	-7,040,026	-4,126,080	13,619,569
Reclassification of convertible preferred stock warrant liability to additional paid-in capital (unaudited)	3,946								3,946
Stock-based compensation expense	895								895
Accretion to redemption value of convertible preferred stock	-35				31	4					-35
Net loss	-33,083										-33,083
Ending balance at Sep. 30, 2014	$162,598						$21		$255,252		($92,675)
Ending balance, shares at Sep. 30, 2014							21,172,221

Statement_of_Shareholders_Equi1

Statement of Shareholders' Equity (Parenthetical) (USD $)	12 Months Ended	9 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Sep. 30, 2014
Series C Convertible Preferred Stock [Member]
Issuance cost	$315
Series D Convertible Preferred Stock [Member]
Issuance cost		$86

Condensed_Statements_of_Cash_F

Condensed Statements of Cash Flows (USD $)	9 Months Ended		12 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Dec. 31, 2012
Cash flows from operating activities:
Net loss	($33,083)	($11,802)	($19,559)	($7,569)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	152	194	257	192
Stock-based compensation	895	125	183	191
Non-cash interest expense	39	2,524	2,528	444
Change in fair value of convertible preferred stock warrant liability	3,300	-2,713	-2,833	-100
Change in fair value of convertible preferred stock purchase right				-3,707
Deferred rent	-54	-9	-24	317
Changes in operating assets and liabilities:
Prepaid and other assets	-542	-74	-1,013	-530
Accounts payable	-814	-249	874	641
Accrued expenses	2,076	450	60	-472
Accrued compensation	1,010	413	60	-235
Net cash used in operating activities	-27,021	-11,141	-19,467	-10,828
Cash flows from investing activities:
(Increase) decrease in restricted cash	75		-25
Purchases of property and equipment	-402	-445	-486	-185
Net cash used in investing activities	-327	-445	-511	-185
Cash flows from financing activities:
Proceeds from convertible notes payable		7,009	7,009	8,011
Proceeds from issuance of convertible preferred stock, net of issuance costs	49,239	22,641	45,585
Proceeds from issuance of common stock in initial public offering, net of fees	104,681
Proceeds from issuance of restricted common stock and exercise of stock options, net of early exercise liability	98	5	5	3
Proceeds from exercise of preferred stock warrants	1,201
Net cash provided by financing activities	155,219	29,655	52,599	8,014
Net change in cash	127,871	18,069	32,621	-2,999
Cash at beginning of period	37,284	4,663	4,663	7,662
Cash at end of period	165,155	22,732	37,284	4,663
Supplemental disclosure of non-cash investing and financing activities:
Purchase of property and equipment in accounts payable and accrued expenses	19	7	15
Conversion of convertible notes payable and accrued interest into convertible preferred stock		15,982	15,982
Initial public offering costs in accounts payable and accrued expenses	$555

Description_of_Business_and_Ba

Description of Business and Basis of Presentation	9 Months Ended
	Sep. 30, 2014
Accounting Policies [Abstract]
Description of Business and Basis of Presentation	1. Description of Business and Basis of Presentation
	Description of Business
	Otonomy, Inc. (the Company) was incorporated in the state of Delaware on May 6, 2008. The Company is a clinical-stage biopharmaceutical company focused on the development and commercialization of innovative therapeutics for the treatment of diseases and disorders of the ear. The Company’s proprietary technology is designed to deliver drug that is retained in the ear for an extended period of time following a single local administration. Utilizing this technology, the Company has advanced three product candidates into development. AuriProTM is a sustained-exposure formulation of the antibiotic ciprofloxacin for which the Company has completed two Phase 3 clinical trials in pediatric patients with middle ear effusion at the time of tympanostomy tube placement surgery. OTO-104 is a sustained-exposure formulation of the steroid dexamethasone that is in a Phase 2b clinical trial for the treatment of patients with Ménière’s disease. OTO-311 is a sustained-exposure formulation of the N-methyl-D-aspartate (NMDA) receptor antagonist gacyclidine in preclinical development as a potential treatment for tinnitus.
	Initial Public Offering
	In August 2014, the Company completed its initial public offering (the IPO) of 7,187,500 shares of common stock, which includes the exercise in full by the underwriters of their option to purchase up to 937,500 shares of common stock, at an offering price of $16.00 per share. Proceeds from the IPO were approximately $104.1 million, net of underwriting discounts and commissions and offering-related transaction costs incurred. In connection with the IPO: (i) the Company’s outstanding shares of convertible preferred stock were automatically converted into 13,619,569 shares of common stock, (ii) the warrants exercisable for Series A convertible preferred stock were automatically converted into warrants exercisable for 142,113 shares of common stock and (iii) the warrants exercisable for Series C convertible preferred stock were exercised and such shares were automatically converted into 228,902 shares of common stock.
	Basis of Presentation
	As of December 31, 2013 and September 30, 2014, the Company has devoted substantially all of its efforts to product development, raising capital, and building infrastructure and has not realized revenues from its planned principal operations. The accompanying financial statements have been prepared assuming the Company will continue as a going concern, which contemplates the realization of assets and the satisfaction of liabilities in the normal course of business. The Company has incurred operating losses and negative cash flows from operating activities since inception. As of December 31, 2013, the Company had working capital of $36.3 million and an accumulated deficit of $59.6 million. As of September 30, 2014, the Company had working capital of $161.8 million and an accumulated deficit of $92.7 million. The Company anticipates that it will continue to incur net losses into the foreseeable future as it: (i) continues the development and begins commercialization of its product candidates AuriPro, OTO-104 and OTO-311; (ii) works to develop additional product candidates through research and development programs; and (iii) expands its corporate infrastructure. The Company plans to continue to fund its losses from operations and capital funding needs through future debt and/or equity financings or other sources, such as potential collaboration agreements. If the Company is not able to secure adequate additional funding, the Company may be forced to make reductions in spending, extend payment terms with suppliers, liquidate assets where possible, and/or suspend or curtail planned programs. Any of these actions could materially harm the Company’s business, results of operations, and future prospects.
	Recently Issued Accounting Standards
	In June 2014, new guidance was issued that eliminates the financial reporting distinction between development stage entities and other reporting entities under accounting principles generally accepted in the United States of America (GAAP), thereby eliminating the requirements to present inception-to-date information in the statements of operations, stockholders’ (deficit) equity and cash flows or label the financial statements as those of a development stage entity. The Company has early adopted, as permitted, the new guidance as of June 30, 2014, and therefore has not labeled its financial statements as those of a development stage entity or included any inception-to-date information. The new standards are to be applied retrospectively and impact the presentation of the financial statements, but do not impact the Company’s financial position or results of operations.
	Unaudited Interim Financial Information
	The accompanying interim balance sheet as of September 30, 2014, statements of operations, and cash flows for the nine months ended September 30, 2013 and 2014, the statements of convertible preferred stock and stockholders’ (deficit) equity for the nine months ended September 30, 2014 and the related footnote disclosures are unaudited. These unaudited interim financial statements have been prepared on the same basis as the annual audited financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments necessary for the fair statement of the Company’s financial position as of September 30, 2014, and the results of its operations and cash flows for the nine months ended September 30, 2013 and 2014. The results for the nine months ended September 30, 2014 are not necessarily indicative of results to be expected for the year ending December 31, 2014, or any other interim or future year or period.

Summary_of_Significant_Account

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2014
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies
	Use of Estimates
	The accompanying financial statements have been prepared in accordance with GAAP. The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expense during the reporting period. The most significant estimates in the Company’s financial statements relate to equity awards, clinical trial accruals and the valuation of convertible preferred stock warrants. Although these estimates are based on the Company’s knowledge of current events and actions it may undertake in the future, actual results may ultimately materially differ from these estimates and assumptions.
	Segment Reporting
	Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. The Company views its operations and manages its business in one operating segment.
	Concentrations of Credit Risk
	Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash. Deposits in the Company’s checking account are maintained in federally insured financial institutions in excess of federally insured limits. The Company has not experienced any losses in such accounts and believes it is not exposed to significant risk on its cash balances due to the financial position of the depository institution in which those deposits are held. Additionally, the Company established guidelines regarding approved investments and maturities of investments, which are designed to maintain safety and liquidity.
	Cash
	Cash consists of cash and highly liquid investments with original maturities of three months or less at the date of purchase. Cash is readily available in checking and savings accounts.
	Restricted Cash
	Restricted cash is comprised of cash held by a bank to securitize the Company’s corporate credit card.
	Fair Value of Financial Instruments
	The carrying value of the Company’s cash, restricted cash, prepaid expenses and other current assets, other assets, accounts payable, accrued liabilities, and accrued compensation approximate fair value due to the short-term nature of these items. The convertible preferred stock warrant liability is carried at fair value (see Note 6).
	Property and Equipment
	Property and equipment generally consist of manufacturing equipment, furniture and fixtures, computers, and scientific and office equipment and are recorded at cost and depreciated using the straight-line method over the estimated useful lives of the assets (generally three to ten years). Leasehold improvements are stated at cost and are depreciated on a straight-line basis over the lesser of the remaining term of the related lease or the estimated useful lives of the assets. Repairs and maintenance costs are charged to expense as incurred.
	Impairment of Long-Lived Assets
	The Company assesses the value of its long-lived assets, which consist of property and equipment, for impairment on an annual basis and whenever events or changes in circumstances and the undiscounted cash flows generated by those assets indicate that the carrying amount of such assets may not be recoverable. While the Company’s current and historical operating losses and negative cash flows are indicators of impairment, management believes that future cash flows to be received support the carrying value of its long-lived assets and, accordingly, has not recognized any impairment losses through September 30, 2014.
	Clinical Trial Expense Accruals
	As part of the process of preparing the Company’s financial statements, the Company is required to estimate expenses resulting from the Company’s obligations under contracts with vendors, clinical research organizations and consultants and under clinical site agreements in connection with conducting clinical trials. The financial terms of these contracts are subject to negotiations, which vary from contract to contract and may result in payment flows that do not match the periods over which materials or services are provided under such contracts.
	The Company’s objective is to reflect the appropriate clinical trial expenses in its financial statements by recording those expenses in the period in which services are performed and efforts are expended. The Company accounts for these expenses according to the progress of the trial as measured by patient progression and the timing of various aspects of the trial. The Company determines accrual estimates through financial models taking into account discussion with applicable personnel and outside service providers as to the progress or state of its trials. During the course of a clinical trial, the Company adjusts its clinical expense if actual results differ from its estimates. The Company makes estimates of accrued expenses as of each balance sheet date based on the facts and circumstances known at that time. Accordingly, the Company’s clinical trial accruals are dependent upon accurate reporting by contract research organizations and other third-party vendors. Although the Company does not expect its estimates to be materially different from amounts actually incurred, the Company’s understanding of the status and timing of services performed relative to the actual status and timing of services performed may vary and may result in reporting amounts that are too high or too low for any particular period. For the years ended December 31, 2012 and 2013, and the nine months ended September 30, 2014, there were no material adjustments to prior period estimates of accrued expenses for clinical trials.
	Research and Development
	Research and development expenses include the costs associated with the Company’s research and development activities, including salaries, benefits and occupancy costs. Also included in research and development expenses are third-party costs incurred in conjunction with contract manufacturing for the Company’s research and development programs and clinical trials, including the cost of clinical trial drug supply, costs incurred by contract research organizations and regulatory expenses. Research and development costs are expensed as incurred.
	Patent Expenses
	The Company expenses all costs as incurred in connection with patent applications (including direct application fees, and the legal and consulting expenses related to making such applications) and such costs are included in general and administrative expenses in the accompanying statements of operations.
	Convertible Preferred Stock
	Prior to the Company’s IPO, the Company’s outstanding convertible preferred stock was classified as temporary equity instead of stockholders’ deficit in accordance with authoritative guidance for the classification and measurement of potentially redeemable securities, as the stock was conditionally redeemable at the holder’s option and upon certain change in control events that are outside the Company’s control, including the liquidation, sale, or transfer of control of the Company. Upon such change in control events, holders of the convertible preferred stock could cause its redemption.
	In connection with the IPO, all of the Company’s outstanding shares of convertible preferred stock were automatically converted into shares of common stock.
	Convertible Preferred Stock Warrants
	Prior to the Company’s IPO, warrants exercisable for shares of the Company’s Series A and Series C convertible preferred stock were classified as liabilities in the accompanying balance sheets based upon the characteristics and provisions of each instrument. Convertible preferred stock warrants were classified as derivative liabilities and were recorded at their fair value on the date of issuance. At each reporting date the convertible preferred stock warrants were revalued, with fair value changes recognized as increases in or decreases to the change in fair value of convertible preferred stock warrant liability in the accompanying statements of operations.
	In connection with the IPO, all of the Company’s outstanding warrants to purchase convertible preferred stock were either (i) exercised and the underlying shares of preferred stock were automatically converted into shares of common stock or (ii) converted into warrants to purchase common stock. Prior to the exercise and conversion of the warrants to purchase convertible preferred stock, the Company performed the final revaluation of the warrant liability upon the closing of the IPO in August 2014 and recorded the $2.6 million increase in fair value to change in fair value of convertible preferred stock warrant liability in the accompanying statements of operations. The warrant liability was then reclassified to additional paid-in capital on the accompanying balance sheets.
	Convertible Preferred Stock Purchase Right
	The Company determined that its obligation to issue, and the investors’ obligation to purchase, additional shares of the Company’s Series B convertible preferred stock represented a freestanding financial instrument and required liability accounting. This freestanding convertible preferred stock purchase right liability was initially recorded at fair value, with fair value changes recognized as increases in or decreases to the change in fair value of convertible preferred stock purchase right in the accompanying statements of operations. In June 2012, the convertible preferred stock purchase right expired and its fair value was recognized in change in fair value of convertible preferred stock purchase right in the accompanying statements of operations.
	Stock-Based Compensation
	The Company accounts for stock-based compensation expense related to stock options and employee stock purchase plan (ESPP) rights by estimating the fair value on the date of grant using the Black-Scholes-Merton option pricing model net of estimated forfeitures. For awards subject to time-based vesting conditions, stock-based compensation expense is recognized using the straight-line method.
	The Company accounts for stock options granted to non-employees, including members of the scientific advisory board, using the fair value approach. Stock options granted to non-employees are subject to periodic revaluation over their vesting terms with the related expense being recognized as research and development and/or general and administrative expense in the accompanying statements of operations.
	Income Taxes
	The Company accounts for income taxes under the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements. Under this method, deferred tax assets and liabilities are determined on the basis of the differences between the financial statements and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date.
	The Company recognizes net deferred tax assets to the extent that the Company believes these assets are more likely than not to be realized. In making such a determination, management considers all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, tax-planning strategies, and results of recent operations. If management determines that the Company would be able to realize its deferred tax assets in the future in excess of their net recorded amount, management would make an adjustment to the deferred tax asset valuation allowance, which would reduce the provision for income taxes.
	The Company uses a two-step approach to recognizing and measuring uncertain tax positions. The first step is to evaluate tax positions taken or expected to be taken in a tax return by assessing whether they are more likely than not sustainable, based solely on their technical merits, upon examination and including resolution of any related appeals or litigation process. The second step is to measure the associated tax benefit of each position as the largest amount that the Company believes is more likely than not realizable. Differences between the amount of tax benefits taken or expected to be taken in the Company’s income tax returns and the amount of tax benefits recognized in its financial statements, represent its unrecognized income tax benefits, which the Company either records as a liability or as a reduction of deferred tax assets.
	Comprehensive Loss
	Comprehensive loss is defined as the change in equity during a period from transactions and other events and/or circumstances from non-owner sources. For all periods presented, comprehensive loss is equal to net loss.
	Net Loss Per Share
	Basic net loss per common share is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of common shares outstanding during the period, without consideration for potentially dilutive securities. Diluted net loss per share is computed by dividing the net loss attributable to common stockholders by the weighted-average number of common shares and potentially dilutive securities outstanding for the period determined using the treasury-stock and if-converted methods. For purposes of the diluted net loss per share calculation, potentially dilutive securities are excluded from the calculation of diluted net loss per share because their effect would be anti-dilutive and therefore, basic and diluted net loss per share were the same for all periods presented.
	Potentially dilutive securities excluded from the calculation of diluted net loss per share attributable to common stockholders are as follows (in common stock equivalent shares):
		As of December 31,				As of September 30,
		2012		2013		2013		2014
						(unaudited)
	Convertible preferred stock		2,453,463		9,493,489		6,882,572		—
	Convertible notes payable		580,580		—		—		—
	Warrants to purchase convertible preferred stock		255,013		483,517		483,517		—
	Warrants to purchase common stock		—		—		—		142,113
	Unvested restricted common stock subject to repurchase		859		—		—		16,294
	Options to purchase common stock		382,663		1,235,705		373,375		2,058,910
			3,672,578		11,212,711		7,739,464		2,217,317

Balance_Sheet_Details

Balance Sheet Details	9 Months Ended
	Sep. 30, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Balance Sheet Details	3. Balance Sheet Details
	Prepaid and Other Current Assets
	Prepaid and other current assets are comprised of the following (in thousands):
		December 31,						September 30,
		2012			2013			2014
								(unaudited)
	Prepaid clinical trial costs	$	500		$	1,478		$	1,054
	Other		197			176			1,123
	Total	$	697		$	1,654		$	2,177
	Property and Equipment, Net
	Property and equipment, net consists of the following (in thousands):
		December 31,						September 30,
		2012			2013			2014
								(unaudited)
	Laboratory equipment	$	827		$	908		$	1,088
	Manufacturing equipment		—			392			607
	Computer equipment and software		102			93			114
	Leasehold improvements		138			67			67
	Office furniture		15			17			17
			1,082			1,477			1,893
	Less: accumulated depreciation and amortization		(643	)		(794	)		(941	)
	Total	$	439		$	683		$	952
	Depreciation expense was $0.2 million and $0.3 million for the years ended December 31, 2012 and 2013, respectively. Depreciation expense was $0.2 million for each of the nine month periods ended September 30, 2013 and 2014.
	Accrued Expenses
	Accrued expenses consist of the following (in thousands):
		December 31,						September 30,
		2012			2013			2014
								(unaudited)
	Accrued clinical trial costs	$	197		$	196		$	1,892
	Accrued other		118			188			594
	Total	$	315		$	384		$	2,486

Notes_Payable_and_Convertible_

Notes Payable and Convertible Preferred Stock Warrants	9 Months Ended
	Sep. 30, 2014
Text Block [Abstract]
Notes Payable and Convertible Preferred Stock Warrants	4. Notes Payable and Convertible Preferred Stock Warrants
	2012 Notes Payable
	In August 2012 and October 2012, the Company entered into a note and warrant purchase agreement (the 2012 Convertible Note Agreement) under which the Company issued $8.0 million in secured convertible promissory notes (the 2012 Notes). The 2012 Notes had an interest rate of 8% per annum and were secured by all of the Company’s assets. The 2012 Notes were convertible into shares of the Company’s equity securities sold at the next financing yielding gross proceeds to the Company of at least $10.0 million.
	In connection with the issuance of the 2012 Notes, the Company issued warrants for the purchase of 182,082 shares of the Company’s Series C convertible preferred stock with an exercise price of $8.79 per share. The estimated fair value of the warrants issued with the 2012 Notes at issuance was $1.4 million (the 2012 Warrant Liability). The Company estimated the fair value of the 2012 Warrant Liability at issuance utilizing the Black-Scholes-Merton option-pricing model. The 2012 Warrant Liability was revalued at each reporting date with changes in fair value being recognized in change in fair value of convertible preferred stock warrant liability in the accompanying statements of operations (see Note 6). The debt discount was amortized using the effective interest rate method over the term of the convertible notes to interest expense in the accompanying statements of operations.
	2013 Notes Payable
	In January 2013, the Company issued an additional $7.0 million in secured convertible promissory notes in a subsequent closing under the 2012 Convertible Note Agreement with several investors and the Company’s chief executive officer (the 2013 Notes).
	In connection with the issuance of the 2013 Notes, the Company issued warrants which were convertible into either Series B convertible preferred stock or the next series of preferred stock issued. Thus the number of shares was not determinable at the date of issuance. The estimated fair value of the warrants issued with the 2013 Notes was $0.6 million at issuance (the 2013 Warrant Liability). The 2013 Warrant Liability was revalued at each reporting date with changes in fair value being recognized in change in fair value of convertible preferred stock warrant liability in the accompanying statements of operations (see Note 6). The debt discount was amortized using the effective interest rate method over the term of the convertible notes to interest expense in the accompanying statements of operations.
	In August 2013, the 2012 Notes and the 2013 Notes in the amount of approximately $16.0 million, including interest, converted into 1,818,191 shares of Series C convertible preferred stock. Concurrent with the closing of the Series C convertible preferred stock, the warrants issued in conjunction with the 2012 Notes and the 2013 Notes converted into warrants for the purchase of an aggregate of 341,404 shares of Series C convertible preferred stock with an exercise price of $8.79 per share.
	Warrants
	As of December 31, 2012 and 2013, the Company’s outstanding convertible preferred stock warrants, issued in connection with its convertible notes payable, consisted of the following:
	Issue Date	Series		Exercise		Number of Shares		Expiration Date
				Price		Outstanding
						Underlying
						Warrant
	11/4/2008		Series A	$	31.092		14,106	11/4/18
	12/8/2008		Series A	$	31.092		14,106	12/8/18
	1/14/2009		Series A	$	31.092		14,106	1/14/19
	4/13/2009		Series A	$	31.092		14,106	4/13/19
	7/1/2009		Series A	$	31.092		14,106	7/1/19
	10/8/09		Series A	$	31.092		14,106	10/8/19
	12/15/09		Series A	$	31.092		14,106	12/15/19
	1/22/10		Series A	$	31.092		14,106	1/22/20
	3/15/10		Series A	$	31.092		703	3/15/20
	4/1/10		Series A	$	31.092		14,106	4/1/20
	5/28/10		Series A	$	31.092		14,456	5/28/20
	8/23/12		Series C	$	8.79		182,022	8/23/22
	10/24/12		Series C	$	8.79		60	10/24/22
	Total outstanding at December 31, 2012						324,195
	1/22/13		Series C	$	8.79		159,322	1/22/23
	Total outstanding at December 31, 2013						483,517
	The aggregate fair value of the Series A and Series C convertible preferred stock warrants as of December 31, 2012 was approximately $1.6 million and $1.3 million, respectively. The aggregate fair value of the Series A and Series C convertible preferred stock warrants as of December 31, 2013 was approximately $46,000 and $0.6 million, respectively.
	In connection with the closing of the IPO, (i) the Series A convertible preferred stock warrants automatically converted into warrants to purchase 142,113 shares of common stock at an exercise price of $14.1765 per share, which warrants remained outstanding as of September 30, 2014, and (ii) of the 341,404 Series C convertible preferred stock warrants, 204,773 warrants were net exercised for 92,271 shares of Series C convertible preferred stock, the remaining warrants for the purchase of 136,631 shares of Series C convertible preferred stock were cash exercised for proceeds to the Company of $1.2 million, and all of the shares of Series C convertible preferred stock were automatically converted to shares of common stock.
	Credit Facility
	In July 2013, the Company entered into a loan and security agreement (the Credit Facility) with a bank for working capital in an aggregate principal amount of $7.0 million. In connection with the Credit Facility, the Company granted a security interest in all its assets, except intellectual property. The Company issued a warrant for its Series C convertible preferred stock that would become exercisable for 3% of the amount of the debt actually drawn at an exercise price of $0.25 per share. The Credit Facility and related warrant expired on July 31, 2014. No amounts were drawn under the Credit Facility and there was no debt issued or warrants exercisable.
	Non-Cash Interest Expense
	The following table summarizes interest expense recognized under the Company’s convertible notes payable and convertible preferred stock warrants (in thousands):
		Years Ended				Nine Months
		December 31,				Ended September 30,
		2012		2013		2013		2014
						(unaudited)
	Stated interest on convertible notes payable	$	228	$	749	$	749	$	—
	Amortization of deferred financing costs associated with the convertible preferred stock warrants		216		1,779		1,775		39
	Total interest expense	$	444	$	2,528	$	2,524	$	39

Commitments_and_Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2014
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	5. Commitments and Contingencies
	Operating Leases
	In December 2010, the Company signed a sublease agreement with a related party for a one-year term through December 31, 2011. In December 2011, the Company extended the term of the sublease through December 2012 on a month-to-month basis. In June 2012, the Company vacated the premises and fulfilled its obligations under the sublease (see Note 9).
	In September 2011, the Company entered into a lease agreement with a third party on a new facility for a five-year term commencing in February 2012.
	Rent expense for each of the years ended December 31, 2012 and 2013, was $0.4 million. Rent expense was $0.3 million for each of the nine months ended September 30, 2013 and 2014. For financial reporting purposes, rent expense is recognized on a straight-line basis over the term of the lease. Accordingly, rent expense recognized in excess of rent paid is accounted for as deferred rent in the accompanying balance sheets.
	As of December 31, 2013, future minimum annual obligations under all non-cancellable operating lease commitments, including the facility lease described above are as follows (in thousands):
	2014	$	471
	2015		473
	2016		487
	2017		82
	Total	$	1,513
	Litigation
	From time to time, the Company may be involved in various lawsuits, legal proceedings, or claims that arise in the ordinary course of business. Management believes there are no claims or actions pending against the Company as of December 31, 2013 or September 30, 2014 which will have, individually or in the aggregate, a material adverse effect on its business, liquidity, financial position, or results of operations. Litigation, however, is subject to inherent uncertainties, and an adverse result in these or other matters may arise from time to time that may harm the Company’s business.
	License Agreements
	The following table summarizes costs recognized, in research and development, under the Company’s license agreements and other non-cancellable royalty and milestone obligations (in thousands):
		Years Ended				Nine Months Ended
		December 31,				September 30,
		2012		2013		2013		2014
						(unaudited)
	License and other fees	$	25	$	250	$	44	$	19
	Milestone fees		—		1,100		100		—
	Total license and related fees	$	25	$	1,350	$	144	$	19
	Intellectual Property Licenses
	The Company has acquired exclusive rights to develop patented rights, information rights and related know-how for the Company’s AuriPro, OTO-104 and OTO-311 product candidates and potential future product candidates under licensing agreements with third parties in the course of its research and development activities. The licensing rights obligate the Company to make payments to the licensors for license fees, milestones, license maintenance fees and royalties. Annual license and maintenance fees related to these agreements is $25,000. The license and maintenance fees will continue until the first commercial sale of a product. In addition, the Company issued 710 shares of common stock as compensation for one of the licenses. The Company is also responsible for patent prosecution costs.
	Under one of these agreements, the Company has achieved five development milestones, totaling $1.2 million, related to its clinical trials for both AuriPro and OTO-104. The Company may be obligated to make additional milestone payments under these agreements as follows (in thousands, except share data):
		Shares of		Cash
		Common Stock		Payments
	Development		1,066	$	3,235
	Regulatory		1,066		12,670
	Commercialization		—		1,000
	Total		2,132	$	16,905
	In addition, the Company may owe royalties of less than five percent on sales of commercial products, if any, developed using these licensed technologies. The Company may also be obligated to pay to the licensors a percentage of fees received if and when the Company sublicenses the technology. As of December 31, 2013 and September 30, 2014, the Company has not yet developed a commercial product using the licensed technologies and it has not entered into any sublicense agreements for the technologies.
	Other Royalty Arrangements
	The Company entered into an agreement related to three provisional patents for AuriPro under which the Company may be obligated to pay a one-time milestone payment of $0.5 million upon the first commercial sale of an approved product and to pay royalties of less than one percent on product sales. The royalties are payable until the later of: (i) the expiration of the last to expire patent owned by the Company in such country covering AuriPro; or (ii) 10 years after the first commercial sale of AuriPro after receipt of regulatory approval for AuriPro in such country.

Fair_Value

Fair Value	9 Months Ended
	Sep. 30, 2014
Fair Value Disclosures [Abstract]
Fair Value	6. Fair Value
	The accounting guidance defines fair value, establishes a consistency framework for measuring fair value and expands disclosure for each major asset and liability category measured at fair value on either a recurring basis or nonrecurring basis. Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants on the measurement date. Accounting guidance establishes a three-tier fair value hierarchy that requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. These tiers are based on the source of the inputs and are as follows:
	Level 1:		Observable inputs such as quoted prices in active markets for identical assets or liabilities.
	Level 2:		Inputs other than quoted prices in active markets that are observable either directly or indirectly.
	Level 3:		Unobservable inputs in which there is little or no market data, which require the reporting entity to develop its own assumptions.
	At December 31, 2012 and 2013, Level 3 liabilities consisted of convertible preferred stock warrant liabilities. The Company held no financial assets or liabilities measured at fair value on a recurring basis as of September 30, 2014. The following fair value hierarchy tables present information about each major category of the Company’s financial liabilities measured at fair value on a recurring basis as of December 31, 2012 and 2013 (in thousands):
			Fair Value Measurement at December 31, 2012
			Fair Value			Level 1			Level 2		Level 3
	Liabilities:
	Convertible preferred stock warrants(1)		$	2,909		$	—		$	—	$	2,909
	Total liabilities		$	2,909		$	—		$	—	$	2,909
	-1	Convertible preferred stock warrant liabilities to purchase Series A and Series C convertible preferred stock at December 31, 2012 are classified as Level 3 and were measured at fair value using the Black-Scholes-Merton option pricing model. The Company developed its estimates based on publicly available historical data and all available information as of the valuation date. Inputs used in the pricing model include estimates of the Company’s risk-free interest rate, expected dividend yield, expected volatility and expected term. As of December 31, 2012, the warrants were revalued using the Black-Scholes-Merton option pricing model based on the following inputs:
			Series A			Series C
	Risk-free interest rate			1.2	%		1.8	%
	Expected dividend yield			0	%		0	%
	Expected volatility			92.2	%		88.2	%
	Expected term (in years)			6.6			9.7
			Fair Value Measurement at December 31, 2013
			Fair Value			Level 1			Level 2		Level 3
	Liabilities:
	Convertible preferred stock warrants(2)		$	646		$	—		$	—	$	646
	Total liabilities		$	646		$	—		$	—	$	646
	-2	Convertible preferred stock warrant liabilities to purchase Series A and Series C convertible preferred stock at December 31, 2013 are classified as Level 3 and are measured using a hybrid of the option pricing model and the PWERM on each reporting date. The key inputs into the models include the probability and timing of expected liquidity events, discount rates and the selection of appropriate market-comparable transactions and multiples to apply to the Company’s various historical and forecasted operational metrics.
	The following table provides a reconciliation of all liabilities measured at fair value using Level 3 significant unobservable inputs (in thousands):
			Convertible			Convertible
			Preferred Stock			Preferred Stock
			Warrant Liability(1)			Purchase Right(2)
	Balance at December 31, 2011		$	1,632		$	3,707
	Expiration of convertible preferred stock purchase right			—			(3,707	)
	Issuance of convertible preferred stock warrants			1,377			—
	Change in fair value			(100	)		—
	Balance at December 31, 2012			2,909			—
	Issuance of convertible preferred stock warrants			570			—
	Change in fair value			(2,833	)		—
	Balance at December 31, 2013			646			—
	Change in fair value (unaudited)			3,300			—
	Reclassification to additional paid-in capital upon closing of IPO (unaudited)			(3,946	)		—
	Balance at September 30, 2014 (unaudited)		$	—		$	—
	-1	Changes in the fair value of the convertible preferred stock warrant liability were recognized in change in fair value of convertible preferred stock warrant liability in the accompanying statements of operations.
	-2	The change in the fair value of the convertible preferred stock purchase right was recognized in change in fair value of convertible preferred stock purchase right in the accompanying statements of operations.
	Convertible Preferred Stock Purchase Right
	The convertible preferred stock purchase right (the Purchase Right) was recorded as a liability in accordance with the accounting guidance at its estimated fair value on the date of issuance of $3.8 million, and was revalued at each reporting date for any changes in the estimated fair value.
	The estimated fair value of the Purchase Right was determined using a valuation model that considers the probability of achieving a milestone, the entity’s cost of capital, the estimated time period the Purchase Right will be outstanding, consideration received for the instrument with the Purchase Right, the number of shares to be issued and specific share pricing to satisfy the Purchase Right, and any changes in the fair value of the underlying instrument to the Purchase Right. The second closing of the Series B convertible preferred stock financing was completed on May 18, 2011, at which time 996,382 shares of Series B convertible preferred stock were purchased and the related portion of the fair value of the Purchase Right of $1.2 million was reclassified to Series B convertible preferred stock in the accompanying balance sheets. The Purchase Right related to the third tranche expired in June 2012, at which time the carrying value of the liability of $3.7 million was recognized in change in fair value of convertible preferred purchase right in the accompanying statements of operations.

Convertible_Preferred_Stock_an

Convertible Preferred Stock and Stockholders' (Deficit) Equity	9 Months Ended
	Sep. 30, 2014
Equity [Abstract]
Convertible Preferred Stock and Stockholders' (Deficit) Equity	7. Convertible Preferred Stock and Stockholders’ (Deficit) Equity
	Convertible Preferred Stock
	Series A Convertible Preferred Stock
	In May 2010, the Company entered into an agreement with two investors for the purchase of Series A convertible preferred stock at $31.092 per share. The Company issued 339,863 shares of Series A convertible preferred stock upon the conversion of the Notes and related accrued interest totaling $10.6 million (see Note 4).
	Series B Convertible Preferred Stock
	In August 2010, the Company entered into an agreement with several investors for the purchase of 1,708,076 shares of the Company’s Series B convertible preferred stock to be completed in three closings. The Company issued 708,030 shares of Series B convertible preferred stock at $14.1766 per share for $10.0 million in cash. The Company evaluated the purchase right associated with the second and third tranche closings of the Series B convertible preferred stock and determined that since the purchase right was separately transferrable, the purchase right was therefore a freestanding financial instrument which required separate accounting treatment (see Note 6).
	In February 2011, the Company completed a special closing of the Series B convertible preferred stock through the sale of 3,664 shares of Series B convertible preferred stock at $14.1766 per share for net proceeds of approximately $0.1 million in cash.
	In May 2011, the Company completed a scheduled second closing of its Series B convertible preferred stock through the sale of 996,382 shares Series B convertible preferred stock at $14.1766 per share for net proceeds of $14.1 million in cash.
	Series C Convertible Preferred Stock
	In August 2013, the Company entered into a stock purchase agreement with investors for the purchase of 7,040,026 shares of Series C convertible preferred stock at $8.79 per share, to be completed in two closings. The Company issued 4,420,577 shares in the first closing for net proceeds of $22.6 million in cash, plus the conversion of secured convertible promissory notes totaling approximately $16.0 million, including principal and accrued interest. The Company evaluated the purchase right associated with the second tranche of the Series C convertible preferred stock and determined that it was an embedded derivative which did not require separate accounting treatment as the purchase right was not separately transferable.
	In September 2013, the Company completed a special closing of its Series C convertible preferred stock through the sale of 8,532 shares of Series C convertible preferred stock at $8.79 per share for net proceeds of $0.1 million.
	In December 2013, the Company completed a second closing of its Series C convertible preferred stock through the sale of 2,610,917 shares of Series C convertible preferred stock at $8.79 per share for net proceeds of $22.9 million.
	Series D Convertible Preferred Stock
	On April 23, 2014, the Company completed the sale of 4,126,080 shares of Series D convertible preferred stock to new and existing investors at $11.96 per share for net cash proceeds of $49.2 million (see Note 11).
	The designated, issued and outstanding shares of convertible preferred stock by series as of December 31, 2012 are as follows (liquidation preference in thousands):
		Shares		Shares		Common		Liquidation
		Designated		Outstanding		Stock		Preference
						Equivalents
	Series A		406,712		339,863		745,387	$	13,209
	Series B		3,168,373		1,708,076		1,708,076		36,322
			3,575,085		2,047,939		2,453,463	$	49,531
	The designated, issued and outstanding shares of convertible preferred stock by series as of December 31, 2013 are as follows (liquidation preference in thousands):
		Shares		Shares		Common		Liquidation
		Designated		Outstanding		Stock		Preference
						Equivalents
	Series A		404,671		339,863		745,387	$	2,987
	Series B		1,708,076		1,708,076		1,708,076		15,014
	Series C		7,407,062		7,040,026		7,040,026		92,823
			9,519,809		9,087,965		9,493,489	$	110,824
	In connection with the IPO, all of the Company’s outstanding shares of convertible preferred stock were automatically converted into shares of common stock. No preferred stock dividends were ever paid or declared by the Company.
	Dividends
	The holders of the Series C convertible preferred stock are entitled to receive annual noncumulative dividends at a rate of 8% of the original Series C issuance price per annum. The Series C convertible preferred stock dividends are payable when and if declared by the Company’s Board of Directors and are payable in preference and in priority to any dividends on the Series B convertible preferred stock, Series A convertible preferred stock and common stock. The holders of the Series B convertible preferred stock are entitled to receive annual noncumulative dividends at a rate of 8% of the original Series B issuance price per annum. The Series B convertible preferred stock dividends are payable when and if declared by the Company’s Board of Directors and are payable in preference and in priority to any dividends on the Series A convertible preferred stock and common stock. The holders of the Series A convertible preferred stock are entitled to receive annual noncumulative dividends at a rate of 8% of the original Series A issuance price per annum. The Series A convertible preferred stock dividends are payable when and if declared by the Company’s Board of Directors. The Series A convertible preferred stock dividends are payable in preference and in priority to any dividends on common stock (see Note 11).
	Liquidation Preferences
	In August 2013, in connection with the Company’s Series C convertible preferred stock financing, the Company amended its certificate of incorporation. Prior to the issuance of the Series C convertible preferred stock, the liquidation preferences on the Series A convertible preferred stock and the Series B convertible preferred stock were approximately $38.8659 and $21.2648 per share, respectively. Subsequent to the Series C convertible preferred stock financing, the liquidation preferences are described below.
	Prior to any payment to the holders of the Series B convertible preferred stock, Series A convertible preferred stock and common stock, the holders of the Series C convertible preferred stock are entitled to receive a liquidation preference equal to $13.185 per share, subject to certain anti-dilution adjustments, plus all declared but unpaid dividends on the Series C convertible preferred stock. Prior to any payment to the holders of the Series A convertible preferred stock and common stock, the holders of the Series B convertible preferred stock are entitled to receive a liquidation preference equal to $8.79 per share, subject to certain anti-dilution adjustments, plus all declared but unpaid dividends on the Series B convertible preferred stock. The holders of the Series A convertible preferred stock are entitled to receive a liquidation preference equal to $8.79 per share, subject to certain anti-dilution adjustments, plus all declared but unpaid dividends on the Series A convertible preferred stock. Liquidation payments to the holders of Series A convertible preferred stock have priority and are made in preference to any payments to the holders of common stock. After payment of the full liquidation preferences of the convertible preferred stock, the remaining assets, if any, will be distributed to the holders of the common stock and preferred stock (on an as-if-converted to common stock basis); provided, however that the aggregate amount per share which a holder of a share of convertible preferred stock shall receive shall not exceed $26.37 per share (see Note 11).
	Conversion
	The shares of Series A convertible preferred stock are convertible into shares of common stock at a ratio of 1:2.193204365 at the option of the holder, subject to certain anti-dilution and other adjustments. The shares of Series B convertible preferred stock and Series C convertible preferred stock are convertible into shares of common stock at a ratio of 1:1 at the option of the holder, subject to certain anti-dilution and other adjustments. Each share of convertible preferred stock is automatically converted into common stock immediately upon: (i) the Company’s sale of its common stock in a firm commitment underwritten public offering pursuant to a registration statement under the Securities Act of 1933, as amended, in which the per share price is at least $43.95 (as adjusted) and the net cash proceeds are at least $75,000,000 or (ii) upon the written consent of the holders of at least 64% of the then outstanding Series C convertible preferred stock (the Requisite Holders) (see Note 11).
	Redemption
	At any time following the sixth anniversary of the date the first share of Series C convertible preferred stock was issued (see Note 11), if requested in writing by the Requisite Holders, the Company shall, to the extent it may lawfully do so, redeem all of the outstanding Series A convertible preferred stock, Series B convertible preferred stock and Series C convertible preferred stock in two equal annual installments to be made on both the date that is 60 days following the date of the Requisite Holders’ written request and on the one-year anniversary following the date of the Requisite Holders’ written request.
	The Company is accreting the issuance costs of the convertible preferred stock and the convertible preferred stock purchase right up to the redemption amount using the effective interest rate method. The Company does not have any redemption requirements until 2019. The aggregate amount of redemption requirements for all series of convertible preferred stock outstanding, excluding warrants, that are potentially redeemable assuming exercise of redemption rights at the earliest possible date, is $79.8 million of which $39.9 million is redeemable in each of the years ending December 31, 2019 and 2020 (see Note 11).
	Voting Rights
	The preferred stockholders have voting rights equal to the number of common shares they would own upon conversion of their shares of convertible preferred stock, which is currently at a ratio of 2.193204365 shares of common stock to one share of Series A convertible preferred stock for the Series A preferred stockholders and at a one for one ratio into common stock for the Series B and Series C preferred stockholders (see Note 11).
	Common Stock Subject to Repurchase
	During 2009, the Company sold 11,621 shares of restricted common stock to consultants and employees for $0.001 per share. The common shares generally vest 25% after one year and then monthly over the following three years. As of December 31, 2012, 10,828 of these shares were vested. As of December 31, 2013 and September 30, 2014, all of these shares were vested.
	The Company’s 2010 Equity Incentive Plan (the 2010 Plan), allows for early exercise of certain option awards issued under the plan. As of December 31, 2012 and 2013, no options had been early exercised. As of September 30, 2014, options had been exercised for the purchase of 16,294 shares of common stock, which were unvested and subject to repurchase. Under the authoritative guidance, early exercise is not considered an exercise for accounting purposes and, therefore, any payment for unvested shares is recognized as a liability at the original exercise price. As of September 30, 2014, the Company has recorded an early exercise liability of $54,000 and no shares have been repurchased by the Company.
	Common Stock Reserved for Future Issuance
	Common stock reserved for future issuance is as follows in common equivalent shares:
		December 31, 2013		September 30, 2014
	Conversion of convertible preferred stock		9,493,489		—
	Warrants for the purchase of convertible preferred stock		483,517		—
	Warrants for the purchase of common stock		—		142,113
	Common stock options issued and outstanding		1,235,705		2,058,910
	Common stock options available for future grant		537,993		2,602,675
	Common stock reserved for issuance under ESPP		—		380,000
	Total common stock reserved for future issuance		11,750,704		5,183,698

Stock_Compensation_Plans

Stock Compensation Plans	9 Months Ended
	Sep. 30, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock Compensation Plans	8. Stock Compensation Plans
	2010 Equity Incentive Plan
	The Company granted awards under the 2010 Plan until June 2014. The terms of the 2010 Plan provide for the grant of incentive stock options to the Company’s employees and any parent and subsidiary corporations’ employees, and for the grant of nonstatutory stock options, restricted stock, restricted stock units and stock appreciation rights to the Company’s employees, directors and consultants, and the Company’s parent and subsidiary corporations’ employees and consultants. The compensation committee of the board of directors had the authority to approve the employees and other service providers to whom equity awards were granted and had the authority to determine the terms of each award, subject to the terms of the 2010 Plan, including (i) the number of shares of common stock subject to the award; (ii) when the award becomes exercisable; (iii) the option or stock appreciation right exercise price, which must be at least 100% of the fair market value of the common stock as of the date of grant; and (iv) the duration of the option or stock appreciation right (which may not exceed 10 years). Options granted under the 2010 Plan generally are scheduled to vest over four years, subject to continued service, and subject to certain acceleration of vesting provisions, and expire no later than 10 years from the date of grant. In connection with the adoption of the 2014 Equity Incentive Plan, the Company terminated the 2010 Plan for future use and provided that no further equity awards are to be granted under the 2010 Plan. All outstanding awards under the 2010 Plan will continue to be governed by their existing terms.
	2014 Equity Incentive Plan
	In July 2014, the Company’s board of directors adopted and the Company’s stockholders approved a 2014 Equity Incentive Plan (the 2014 Plan), and the 2014 Plan became effective August 11, 2014. The 2014 Plan permits the grant of incentive stock options to the Company’s employees and any parent and subsidiary corporations’ employees, and for the grant of nonstatutory stock options, restricted stock, restricted stock units, stock appreciation rights, performance units and performance shares to the Company’s employees, directors and consultants and the Company’s parent and subsidiary corporations’ employees and consultants.
	Upon adoption of the 2014 Plan, a total of 2,606,875 shares of common stock were reserved for issuance, including 386,875 shares of common stock previously available for issuance under the 2010 Plan. In addition, the shares to be reserved for issuance under the 2014 Plan will also include shares subject to stock options or similar awards granted under the 2010 Plan that expire or terminate without having been exercised in full and shares issued pursuant to awards granted under the Company’s 2010 Plan that are forfeited to or repurchased by the Company.
	The number of shares available for issuance under the 2014 Plan will also include an annual increase on the first day of each fiscal year beginning in 2015, equal to the least of (i) 2,500,000 shares; (ii) 5% of the outstanding shares of common stock as of the last day of the immediately preceding fiscal year; or (iii) such other amount as the Company’s board of directors may determine.
	The compensation committee of the board of directors has the authority to approve the employees and other service providers to whom equity awards are granted and to determine the terms of each award, subject to the terms of the 2014 Plan. The compensation committee may determine the number of shares subject to an award, except that the 2014 Plan provides certain limits on the number of awards that may be granted to non-employee members of the board of directors under the 2014 Plan in any fiscal year. Options and stock appreciation rights granted under the 2014 Plan must have a per share exercise price equal to at least 100% of the fair market value of a shares of the common stock as of the date of grant and may not expire later than 10 years from the date of grant.
	As of December 31, 2013, 537,993 options were available for grant under the 2010 Plan. As of September 30, 2014, 2,602,675 options were available for grant under the 2014 Plan. The following table summarizes stock option activity for the year ended December 31, 2013 and for the nine months ended September 30, 2014 (in thousands except per share amounts and years):
			Options			Weighted-			Weighted-		Aggregate
						Average			Average		Intrinsic
						Exercise			Remaining		Value
						Price			Contractual
									Term (In Years)
	Outstanding as of December 31, 2012			383		$	2.75
	Granted			862		$	1.76
	Exercised			(2	)	$	3.17
	Forfeited			(7	)	$	2.71
	Outstanding as of December 31, 2013			1,236		$	2.06			9.2	$	47
	Granted			884		$	5.47
	Exercised			(61	)	$	2.51
	Outstanding as of September 30, 2014			2,059		$	3.51			8.9	$	42,189
	Options vested and expected to vest as of December 31, 2013			1,207		$	2.06			9.2	$	47
	Options exercisable as of December 31, 2013			505		$	2.46			8.4	$	15
	Options vested and expected to vest as of September 30, 2014			2,028		$	3.46			9	$	41,659
	Options exercisable as of September 30, 2014			910		$	3.38			7.4	$	18,761
	The following table summarizes certain information regarding stock options (in thousands, except per share data):
			Years Ended						Nine Months Ended
			December 31,						September 30,
			2012			2013			2013		2014
									(unaudited)
	Weighted-average grant date fair value per share of options granted during the period		$	0.79		$	1.28		$	—	$	3.85
	Fair value of options vested during the period			194			206			137		502
	Cash received from options exercised during the period(1)			3			5			5		153
	Intrinsic value of options exercised during the period			—			—			—		111
	-1	For the nine months ended September 30, 2014, cash received from options exercised during the period includes cash proceeds of $54,000 for shares which were early exercised and subject to repurchase as of September 30, 2014. The Company has reflected the early exercise liability within accrued expenses in the accompanying balance sheets.
	2014 Employee Stock Purchase Plan
	In July 2014, the Company’s board of directors adopted and the stockholders approved the Company’s 2014 Employee Stock Purchase Plan (the ESPP), which became effective upon adoption by the Company’s board of directors. The ESPP allows eligible employees to purchase shares of the Company’s common stock at a discount through payroll deductions of up to 15% of their eligible compensation, subject to any plan limitations. The offering periods generally start on the first trading day on or after June 1 and December 1 of each year and end on the first trading day on or before June 1 and December 1 approximately twenty-four months later, and will include six-month purchase periods. The administrator may, in its discretion, modify the terms of future offering periods. Due to the timing of our initial public offering, the first offering period started on August 12, 2014 and will end on June 1, 2016.
	The ESPP initially authorized the issuance of 380,000 shares of the Company’s common stock pursuant to rights granted to employees for their payroll deductions. The number of shares available for issuance under the ESPP will also include an annual increase on the first day of each fiscal year beginning in 2015, equal to the least of (i) 800,000 shares; (ii) 1.5% of the outstanding shares of common stock as of the last day of the immediately preceding fiscal year; or (iii) such other amount as the Company’s board of directors may determine.
	Through September 30, 2014, no shares of common stock have been issued pursuant to ESPP purchases.
	Stock-Based Compensation Expense
	The following are the weighted-average underlying assumptions used to determine the fair value of stock options granted to employees and non-employees using the Black-Scholes-Merton option pricing model:
			Years Ended						Nine Months
			December 31,						Ended
									September 30,
			2012			2013			2013(1)		2014
									(unaudited)
	Risk-free interest rate			1	%		2	%		—		1.9	%
	Expected dividend yield			0	%		0	%		—		0	%
	Expected volatility			92.2	%		85.5	%		—		82.3	%
	Expected term (in years)			6.1			6.1			—		6.1
	-1	The Company did not issue any stock options during the nine months ended September 30, 2013.
	Risk-Free Interest Rate. The Company bases the risk-free interest rate assumption on observed interest rates appropriate for the expected term of the stock option grants.
	Expected Dividend Yield. The Company bases the expected dividend yield assumption on the fact that it has never paid cash dividends and has no present intention to pay cash dividends.
	Expected Volatility. The expected volatility assumption is based on volatilities of a peer group of similar companies whose share prices are publicly available. The peer group was developed based on companies in the biopharmaceutical industry.
	Expected Term. The expected term represents the period of time that options are expected to be outstanding. Because the Company does not have historical exercise behavior, it determines the expected life assumption using the simplified method, which is an average of the contractual term of the option and its ordinary vesting period.
	Forfeitures. The Company reduces stock-based compensation expense for estimated forfeitures. Forfeitures are estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from those estimates.
	Total non-cash stock-based compensation expense recognized in the accompanying statements of operations is as follows (in thousands):
			Years Ended						Nine Months Ended
			December 31,						September 30,
			2012			2013			2013		2014
									(unaudited)
	Research and development		$	78		$	62		$	40	$	407
	General and administrative			113			121			85		488
Total stock-based compensation		$	191		$	183		$	125	$	895
As of December 31, 2013, total compensation costs related to non-vested stock options not yet recognized is $1.3 million which is expected to be recognized over a remaining weighted-average vesting period of 3.3 years.
As of September 30, 2014, total compensation costs related to non-vested stock options not yet recognized is $3.9 million which is expected to be recognized over a remaining weighted-average vesting period of 3.5 years.

Related_Party_Transactions

Related Party Transactions	9 Months Ended
	Sep. 30, 2014
Related Party Transactions [Abstract]
Related Party Transactions	9. Related Party Transactions
	The Company has entered into various services agreements with affiliates of a principal stockholder. Under the terms of the agreements, the affiliated companies shared common services, such as accounting and finance support, through December 2013, and shared facilities through June 2012.
	The following table summarizes related party receivables, payables, payments made and expenses related to affiliated companies under these agreements (in thousands):
		Years Ended				Nine Months Ended
		December 31,				September 30,
		2012		2013		2013		2014
						(unaudited)
	Receivable	$	17	$	9	$	12	$	—
	Payable		6		10		5		—
	Payments		79		28		14		10
	Expenses		60		32		15		—

Income_Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2014
Income Tax Disclosure [Abstract]
Income Taxes	10. Income Taxes
	Pursuant to Internal Revenue Code (IRC) Sections 382 and 383, annual use of the Company’s net operating loss and research and development credit carryforwards may be limited in the event that a cumulative change in ownership of more than 50% occurs within a three-year period. The Company has completed an IRC Section 382/383 analysis, regarding the limitation of net operating loss and research and development credit carryforwards as of December 31, 2013. As a result of the analysis, two ownership changes were determined to have occurred. Based on these changes, the deferred tax assets for net operating losses and federal research and development credits of $3.2 million and $0.3 million, respectively, have been removed from the deferred tax asset schedule and the Company has recorded a corresponding decrease in the valuation allowance. The California research and development credits were not limited as these credits carry forward indefinitely. The Company will continue to consider changes in ownership that may cause losses of tax attributes in the future.
	Significant components of the Company’s deferred tax assets are as follows (in thousands):
		December 31,
		2012			2013
	Deferred tax assets:
	Net operating loss carryforwards	$	11,252		$	18,620
	Research and development credits		621			1,363
	Depreciation and amortization		433			906
	Accrued expenses		75			76
	Deferred rent		126			116
	Other, net		27			31
	Total deferred tax assets		12,534			21,112
	Less: valuation allowance		(12,534	)		(21,112	)
	Total	$	—		$	—
	Due to the Company’s history of losses and uncertainty regarding future earnings, a full valuation allowance has been recorded against the Company’s deferred tax assets, as it is more likely than not that such assets will not be realized. A valuation allowance of approximately $12.5 million and $21.1 million has been established as of December 31, 2012 and 2013, respectively.
	At December 31, 2013, the Company had federal and California net operating loss carryforwards of approximately $46.8 million and $46.6 million, respectively, net of IRC Section 382 limitations. The federal and California net operating loss carryforwards will begin to expire in 2030, unless previously utilized. At December 31, 2013, the Company also had federal and California research and development credit carryforwards of approximately $1.6 million net of IRC Section 383 limitations and $1.1 million, respectively. The federal research and development credit carryforwards will begin expiring in 2030 unless previously utilized. The California research credit will carry forward indefinitely.
	The following is a reconciliation of the expected recovery of income taxes between those that are based on enacted tax rates and laws, to those currently reported for the years ended December 31 (in thousands):
		2012			2013
	Federal statutory rate	$	(2,573	)	$	(6,650	)
	State tax (net of federal benefit)		(628	)		(1,148	)
	Permanent items, other		56			65
	Change in fair value of convertible preferred stock warrant liability		(1,260	)		(963	)
	Change in fair value of convertible preferred stock purchase right		(34	)		—
	Non-deductible interest		150			855
	Other adjustments		10			91
	Research and development credits		(160	)		(1,236	)
	Uncertain tax positions		60			409
	Change in valuation allowance		4,380			8,578
	Provision for income taxes	$	1		$	1
	The following table summarizes the activity related to our gross unrecognized tax benefits (in thousands):
		December 31,
		2012			2013
	Balance at the beginning of the year	$	422		$	515
	Adjustments related to prior year tax positions		(4	)		136
	Increases related to current year tax positions		97			406
	Decreases due to statute of limitations expiration		—			—
	Decreases due to IRC Section 382/383 limitation		—			—
		$	515		$	1,057
	The Company’s policy is to include interest and penalties related to unrecognized income tax benefits as a component of income tax expense. The Company has no accruals for interest or penalties in the accompanying balance sheets as of December 31, 2012 and 2013 and has not recognized interest or penalties in the accompanying statements of operations for the years ended December 31, 2012 and 2013.
	Due to the valuation allowance recorded against the Company’s deferred tax assets, future changes in unrecognized tax benefits will not impact the Company’s effective tax rate. The Company does not expect its unrecognized tax benefits to change significantly in the next 12 months.
	The Company is subject to taxation in the United States and California. Due to the net operating loss carryforwards, the U.S. federal and state returns are open to examination by the IRS and California for all years since inception. The Company has not been, nor is it currently, under examination by the federal or any state tax authority.

Subsequent_Events

Subsequent Events	9 Months Ended
	Sep. 30, 2014
Subsequent Events [Abstract]
Subsequent Events	11. Subsequent Events
	The Company evaluated all events or transactions that occurred after the balance sheet date of December 31, 2013 through June 5, 2014, the date on which these financial statements were available to be issued.
	Series D Convertible Preferred Stock
	On April 23, 2014, the Company completed the sale of 4,126,080 shares of Series D convertible preferred stock to new and existing investors at $11.96 per share for net cash proceeds of $49.2 million.
	Amended Certificate of Incorporation in Connection with the Issuance of the Series D Convertible Preferred Stock
	The certificate of incorporation as amended immediately prior to the issuance of the Series D convertible preferred stock is described below.
	The holders of the Series C and Series D convertible preferred stock on a pari passu basis and in priority have preference to the holders of the Series B and Series A convertible preferred stock and the holders of common stock. The holders of the Series B convertible preferred stock have priority over the holders of Series A convertible preferred stock and the holders of common stock.
	After payment of the liquidation preferences, the remaining assets, if any, will be distributed to the holders of the common stock and the Series B, Series C and Series D convertible preferred stock on a pro rata basis. Each share of convertible preferred stock is automatically converted into common stock immediately upon (i) the Company’s sale of its common stock in a firm commitment underwritten public offering pursuant to a registration statement under the Securities Act of 1933, as amended, in which the per share price is at least $35.87 (as adjusted) and the net cash proceeds are at least $70,000,000 or (ii) upon the written consent of 75% of the then outstanding Preferred Stock on an as-converted basis (the Preferred Stockholders).
	The following table summarizes the preferred stock preferences in connection with the issuance of the Series D convertible preferred stock:
		Dividend Rate			Conversion Rate	Liquidation
						Preference Per Share
	Series D		8	%	1:01	$	11.96
	Series C		8	%	1:01		8.79
	Series B		8	%	1:01		8.79
	Series A		8	%	0102.2		31.092
	At any time following the sixth anniversary of the date the first share of Series D convertible preferred stock was issued, if requested in writing by the Preferred Stockholders, the Company shall, to the extent it may lawfully do so, redeem all of the outstanding Series A convertible preferred stock, Series B convertible preferred stock, Series C convertible preferred stock and Series D convertible preferred stock in two equal annual installments to be made on both the date that is 60 days following the date of the Preferred Stockholders written request and on the one-year anniversary following the date of the Preferred Stockholders written request.
	The Company is accreting the issuance costs of the convertible preferred stock and the convertible preferred stock purchase right up to the redemption amount using the effective interest rate method. The Company does not have any redemption requirements until 2020. The aggregate amount of redemption requirements for all series of convertible preferred stock outstanding, excluding warrants that are potentially redeemable assuming exercise of redemption rights at the earliest possible date is $136.8 million, of which $68.4 million is redeemable in each of the years ending December 31, 2020 and 2021.
	The preferred stockholders have voting rights equal to the number of common shares they would own upon conversion of their shares of convertible preferred stock, which is currently at a ratio of 2.193204365 shares of common stock to one share of Series A convertible preferred stock for the Series A preferred stockholders and at a one-for-one ratio into common stock for the Series B, Series C and Series D preferred stockholders.
	Reverse Stock Split
	On July 31, 2014, the Company filed an amendment to its amended and restated certificate of incorporation, affecting a one-for-35.16 reverse stock split of its outstanding common and convertible preferred stock, which was approved by the Company’s board of directors on July 29, 2014. The accompanying financial statements and notes to the financial statements give retroactive effect to the reverse split for all periods presented.

Description_of_Business_and_Ba1

Description of Business and Basis of Presentation (Policies)	9 Months Ended
	Sep. 30, 2014
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation
	As of December 31, 2013 and September 30, 2014, the Company has devoted substantially all of its efforts to product development, raising capital, and building infrastructure and has not realized revenues from its planned principal operations. The accompanying financial statements have been prepared assuming the Company will continue as a going concern, which contemplates the realization of assets and the satisfaction of liabilities in the normal course of business. The Company has incurred operating losses and negative cash flows from operating activities since inception. As of December 31, 2013, the Company had working capital of $36.3 million and an accumulated deficit of $59.6 million. As of September 30, 2014, the Company had working capital of $161.8 million and an accumulated deficit of $92.7 million. The Company anticipates that it will continue to incur net losses into the foreseeable future as it: (i) continues the development and begins commercialization of its product candidates AuriPro, OTO-104 and OTO-311; (ii) works to develop additional product candidates through research and development programs; and (iii) expands its corporate infrastructure. The Company plans to continue to fund its losses from operations and capital funding needs through future debt and/or equity financings or other sources, such as potential collaboration agreements. If the Company is not able to secure adequate additional funding, the Company may be forced to make reductions in spending, extend payment terms with suppliers, liquidate assets where possible, and/or suspend or curtail planned programs. Any of these actions could materially harm the Company’s business, results of operations, and future prospects.
Recently Issued Accounting Standards	Recently Issued Accounting Standards
	In June 2014, new guidance was issued that eliminates the financial reporting distinction between development stage entities and other reporting entities under accounting principles generally accepted in the United States of America (GAAP), thereby eliminating the requirements to present inception-to-date information in the statements of operations, stockholders’ (deficit) equity and cash flows or label the financial statements as those of a development stage entity. The Company has early adopted, as permitted, the new guidance as of June 30, 2014, and therefore has not labeled its financial statements as those of a development stage entity or included any inception-to-date information. The new standards are to be applied retrospectively and impact the presentation of the financial statements, but do not impact the Company’s financial position or results of operations.
Unaudited Interim Financial Information	Unaudited Interim Financial Information
	The accompanying interim balance sheet as of September 30, 2014, statements of operations, and cash flows for the nine months ended September 30, 2013 and 2014, the statements of convertible preferred stock and stockholders’ (deficit) equity for the nine months ended September 30, 2014 and the related footnote disclosures are unaudited. These unaudited interim financial statements have been prepared on the same basis as the annual audited financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments necessary for the fair statement of the Company’s financial position as of September 30, 2014, and the results of its operations and cash flows for the nine months ended September 30, 2013 and 2014. The results for the nine months ended September 30, 2014 are not necessarily indicative of results to be expected for the year ending December 31, 2014, or any other interim or future year or period.
Use of Estimates	Use of Estimates
	The accompanying financial statements have been prepared in accordance with GAAP. The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expense during the reporting period. The most significant estimates in the Company’s financial statements relate to equity awards, clinical trial accruals and the valuation of convertible preferred stock warrants. Although these estimates are based on the Company’s knowledge of current events and actions it may undertake in the future, actual results may ultimately materially differ from these estimates and assumptions.
Segment Reporting	Segment Reporting
	Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. The Company views its operations and manages its business in one operating segment.
Concentrations of Credit Risk	Concentrations of Credit Risk
	Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash. Deposits in the Company’s checking account are maintained in federally insured financial institutions in excess of federally insured limits. The Company has not experienced any losses in such accounts and believes it is not exposed to significant risk on its cash balances due to the financial position of the depository institution in which those deposits are held. Additionally, the Company established guidelines regarding approved investments and maturities of investments, which are designed to maintain safety and liquidity.
Cash	Cash
	Cash consists of cash and highly liquid investments with original maturities of three months or less at the date of purchase. Cash is readily available in checking and savings accounts.
Restricted Cash	Restricted Cash
	Restricted cash is comprised of cash held by a bank to securitize the Company’s corporate credit card.
Fair Value of Financial Instruments	Fair Value of Financial Instruments
	The carrying value of the Company’s cash, restricted cash, prepaid expenses and other current assets, other assets, accounts payable, accrued liabilities, and accrued compensation approximate fair value due to the short-term nature of these items. The convertible preferred stock warrant liability is carried at fair value (see Note 6).
Property and Equipment	Property and Equipment
	Property and equipment generally consist of manufacturing equipment, furniture and fixtures, computers, and scientific and office equipment and are recorded at cost and depreciated using the straight-line method over the estimated useful lives of the assets (generally three to ten years). Leasehold improvements are stated at cost and are depreciated on a straight-line basis over the lesser of the remaining term of the related lease or the estimated useful lives of the assets. Repairs and maintenance costs are charged to expense as incurred.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets
	The Company assesses the value of its long-lived assets, which consist of property and equipment, for impairment on an annual basis and whenever events or changes in circumstances and the undiscounted cash flows generated by those assets indicate that the carrying amount of such assets may not be recoverable. While the Company’s current and historical operating losses and negative cash flows are indicators of impairment, management believes that future cash flows to be received support the carrying value of its long-lived assets and, accordingly, has not recognized any impairment losses through September 30, 2014.
Clinical Trial Expense Accruals	Clinical Trial Expense Accruals
	As part of the process of preparing the Company’s financial statements, the Company is required to estimate expenses resulting from the Company’s obligations under contracts with vendors, clinical research organizations and consultants and under clinical site agreements in connection with conducting clinical trials. The financial terms of these contracts are subject to negotiations, which vary from contract to contract and may result in payment flows that do not match the periods over which materials or services are provided under such contracts.
	The Company’s objective is to reflect the appropriate clinical trial expenses in its financial statements by recording those expenses in the period in which services are performed and efforts are expended. The Company accounts for these expenses according to the progress of the trial as measured by patient progression and the timing of various aspects of the trial. The Company determines accrual estimates through financial models taking into account discussion with applicable personnel and outside service providers as to the progress or state of its trials. During the course of a clinical trial, the Company adjusts its clinical expense if actual results differ from its estimates. The Company makes estimates of accrued expenses as of each balance sheet date based on the facts and circumstances known at that time. Accordingly, the Company’s clinical trial accruals are dependent upon accurate reporting by contract research organizations and other third-party vendors. Although the Company does not expect its estimates to be materially different from amounts actually incurred, the Company’s understanding of the status and timing of services performed relative to the actual status and timing of services performed may vary and may result in reporting amounts that are too high or too low for any particular period. For the years ended December 31, 2012 and 2013, and the nine months ended September 30, 2014, there were no material adjustments to prior period estimates of accrued expenses for clinical trials.
Research and Development	Research and Development
	Research and development expenses include the costs associated with the Company’s research and development activities, including salaries, benefits and occupancy costs. Also included in research and development expenses are third-party costs incurred in conjunction with contract manufacturing for the Company’s research and development programs and clinical trials, including the cost of clinical trial drug supply, costs incurred by contract research organizations and regulatory expenses. Research and development costs are expensed as incurred.
Patent Expenses	Patent Expenses
	The Company expenses all costs as incurred in connection with patent applications (including direct application fees, and the legal and consulting expenses related to making such applications) and such costs are included in general and administrative expenses in the accompanying statements of operations.
Convertible Preferred Stock	Convertible Preferred Stock
	Prior to the Company’s IPO, the Company’s outstanding convertible preferred stock was classified as temporary equity instead of stockholders’ deficit in accordance with authoritative guidance for the classification and measurement of potentially redeemable securities, as the stock was conditionally redeemable at the holder’s option and upon certain change in control events that are outside the Company’s control, including the liquidation, sale, or transfer of control of the Company. Upon such change in control events, holders of the convertible preferred stock could cause its redemption.
	In connection with the IPO, all of the Company’s outstanding shares of convertible preferred stock were automatically converted into shares of common stock.
Convertible Preferred Stock Warrants	Convertible Preferred Stock Warrants
	Prior to the Company’s IPO, warrants exercisable for shares of the Company’s Series A and Series C convertible preferred stock were classified as liabilities in the accompanying balance sheets based upon the characteristics and provisions of each instrument. Convertible preferred stock warrants were classified as derivative liabilities and were recorded at their fair value on the date of issuance. At each reporting date the convertible preferred stock warrants were revalued, with fair value changes recognized as increases in or decreases to the change in fair value of convertible preferred stock warrant liability in the accompanying statements of operations.
	In connection with the IPO, all of the Company’s outstanding warrants to purchase convertible preferred stock were either (i) exercised and the underlying shares of preferred stock were automatically converted into shares of common stock or (ii) converted into warrants to purchase common stock. Prior to the exercise and conversion of the warrants to purchase convertible preferred stock, the Company performed the final revaluation of the warrant liability upon the closing of the IPO in August 2014 and recorded the $2.6 million increase in fair value to change in fair value of convertible preferred stock warrant liability in the accompanying statements of operations. The warrant liability was then reclassified to additional paid-in capital on the accompanying balance sheets.
Converible Preferred Stock Purchase Right	Convertible Preferred Stock Purchase Right
	The Company determined that its obligation to issue, and the investors’ obligation to purchase, additional shares of the Company’s Series B convertible preferred stock represented a freestanding financial instrument and required liability accounting. This freestanding convertible preferred stock purchase right liability was initially recorded at fair value, with fair value changes recognized as increases in or decreases to the change in fair value of convertible preferred stock purchase right in the accompanying statements of operations. In June 2012, the convertible preferred stock purchase right expired and its fair value was recognized in change in fair value of convertible preferred stock purchase right in the accompanying statements of operations.
Stock-Based Compensation	Stock-Based Compensation
	The Company accounts for stock-based compensation expense related to stock options and employee stock purchase plan (ESPP) rights by estimating the fair value on the date of grant using the Black-Scholes-Merton option pricing model net of estimated forfeitures. For awards subject to time-based vesting conditions, stock-based compensation expense is recognized using the straight-line method.
	The Company accounts for stock options granted to non-employees, including members of the scientific advisory board, using the fair value approach. Stock options granted to non-employees are subject to periodic revaluation over their vesting terms with the related expense being recognized as research and development and/or general and administrative expense in the accompanying statements of operations.
Income Taxes	Income Taxes
	The Company accounts for income taxes under the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements. Under this method, deferred tax assets and liabilities are determined on the basis of the differences between the financial statements and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date.
	The Company recognizes net deferred tax assets to the extent that the Company believes these assets are more likely than not to be realized. In making such a determination, management considers all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, tax-planning strategies, and results of recent operations. If management determines that the Company would be able to realize its deferred tax assets in the future in excess of their net recorded amount, management would make an adjustment to the deferred tax asset valuation allowance, which would reduce the provision for income taxes.
	The Company uses a two-step approach to recognizing and measuring uncertain tax positions. The first step is to evaluate tax positions taken or expected to be taken in a tax return by assessing whether they are more likely than not sustainable, based solely on their technical merits, upon examination and including resolution of any related appeals or litigation process. The second step is to measure the associated tax benefit of each position as the largest amount that the Company believes is more likely than not realizable. Differences between the amount of tax benefits taken or expected to be taken in the Company’s income tax returns and the amount of tax benefits recognized in its financial statements, represent its unrecognized income tax benefits, which the Company either records as a liability or as a reduction of deferred tax assets.
Comprehensive Loss	Comprehensive Loss
	Comprehensive loss is defined as the change in equity during a period from transactions and other events and/or circumstances from non-owner sources. For all periods presented, comprehensive loss is equal to net loss.
Net Loss Per Share	Net Loss Per Share
	Basic net loss per common share is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of common shares outstanding during the period, without consideration for potentially dilutive securities. Diluted net loss per share is computed by dividing the net loss attributable to common stockholders by the weighted-average number of common shares and potentially dilutive securities outstanding for the period determined using the treasury-stock and if-converted methods. For purposes of the diluted net loss per share calculation, potentially dilutive securities are excluded from the calculation of diluted net loss per share because their effect would be anti-dilutive and therefore, basic and diluted net loss per share were the same for all periods presented.

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2014
Accounting Policies [Abstract]
Potentially Dilutive Securities Excluded from Calculation of Diluted Net Loss Per Share Attributable to Common Stockholders	Potentially dilutive securities excluded from the calculation of diluted net loss per share attributable to common stockholders are as follows (in common stock equivalent shares):
		As of December 31,				As of September 30,
		2012		2013		2013		2014
						(unaudited)
	Convertible preferred stock		2,453,463		9,493,489		6,882,572		—
	Convertible notes payable		580,580		—		—		—
	Warrants to purchase convertible preferred stock		255,013		483,517		483,517		—
	Warrants to purchase common stock		—		—		—		142,113
	Unvested restricted common stock subject to repurchase		859		—		—		16,294
	Options to purchase common stock		382,663		1,235,705		373,375		2,058,910
			3,672,578		11,212,711		7,739,464		2,217,317

Balance_Sheet_Details_Tables

Balance Sheet Details (Tables)	9 Months Ended
	Sep. 30, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Prepaid and Other Current Assets	Prepaid and other current assets are comprised of the following (in thousands):
		December 31,						September 30,
		2012			2013			2014
								(unaudited)
	Prepaid clinical trial costs	$	500		$	1,478		$	1,054
	Other		197			176			1,123
	Total	$	697		$	1,654		$	2,177
Property and Equipment, Net	Property and equipment, net consists of the following (in thousands):
		December 31,						September 30,
		2012			2013			2014
								(unaudited)
	Laboratory equipment	$	827		$	908		$	1,088
	Manufacturing equipment		—			392			607
	Computer equipment and software		102			93			114
	Leasehold improvements		138			67			67
	Office furniture		15			17			17
			1,082			1,477			1,893
	Less: accumulated depreciation and amortization		(643	)		(794	)		(941	)
	Total	$	439		$	683		$	952
Accrued Expenses	Accrued expenses consist of the following (in thousands):
		December 31,						September 30,
		2012			2013			2014
								(unaudited)
	Accrued clinical trial costs	$	197		$	196		$	1,892
	Accrued other		118			188			594
	Total	$	315		$	384		$	2,486

Notes_Payable_and_Convertible_1

Notes Payable and Convertible Preferred Stock Warrants (Tables)	9 Months Ended
	Sep. 30, 2014
Text Block [Abstract]
Outstanding Convertible Preferred Stock Warrants	As of December 31, 2012 and 2013, the Company’s outstanding convertible preferred stock warrants, issued in connection with its convertible notes payable, consisted of the following:
	Issue Date	Series		Exercise		Number of Shares		Expiration Date
				Price		Outstanding
						Underlying
						Warrant
	11/4/2008		Series A	$	31.092		14,106	11/4/18
	12/8/2008		Series A	$	31.092		14,106	12/8/18
	1/14/2009		Series A	$	31.092		14,106	1/14/19
	4/13/2009		Series A	$	31.092		14,106	4/13/19
	7/1/2009		Series A	$	31.092		14,106	7/1/19
	10/8/09		Series A	$	31.092		14,106	10/8/19
	12/15/09		Series A	$	31.092		14,106	12/15/19
	1/22/10		Series A	$	31.092		14,106	1/22/20
	3/15/10		Series A	$	31.092		703	3/15/20
	4/1/10		Series A	$	31.092		14,106	4/1/20
	5/28/10		Series A	$	31.092		14,456	5/28/20
	8/23/12		Series C	$	8.79		182,022	8/23/22
	10/24/12		Series C	$	8.79		60	10/24/22
	Total outstanding at December 31, 2012						324,195
	1/22/13		Series C	$	8.79		159,322	1/22/23
	Total outstanding at December 31, 2013						483,517
Summarizes Interest Expense Recognized Under Company's Convertible Notes Payable and Convertible Preferred Stock Warrants	The following table summarizes interest expense recognized under the Company’s convertible notes payable and convertible preferred stock warrants (in thousands):
		Years Ended				Nine Months
		December 31,				Ended September 30,
		2012		2013		2013		2014
						(unaudited)
	Stated interest on convertible notes payable	$	228	$	749	$	749	$	—
	Amortization of deferred financing costs associated with the convertible preferred stock warrants		216		1,779		1,775		39
	Total interest expense	$	444	$	2,528	$	2,524	$	39

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2014
Commitments and Contingencies Disclosure [Abstract]
Future Minimum Annual Obligations Under Operating Lease Commitments	As of December 31, 2013, future minimum annual obligations under all non-cancellable operating lease commitments, including the facility lease described above are as follows (in thousands):
	2014	$	471
	2015		473
	2016		487
	2017		82
	Total	$	1,513
Summary of Costs Recognized Under License Agreements and Other Non-Cancellable Royalty and Milestone Obligations	The following table summarizes costs recognized, in research and development, under the Company’s license agreements and other non-cancellable royalty and milestone obligations (in thousands):
		Years Ended				Nine Months Ended
		December 31,				September 30,
		2012		2013		2013		2014
						(unaudited)
	License and other fees	$	25	$	250	$	44	$	19
	Milestone fees		—		1,100		100		—
	Total license and related fees	$	25	$	1,350	$	144	$	19
Schedule of Additional Milestone Payments	The Company may be obligated to make additional milestone payments under these agreements as follows (in thousands, except share data):
		Shares of		Cash
		Common Stock		Payments
	Development		1,066	$	3,235
	Regulatory		1,066		12,670
	Commercialization		—		1,000
	Total		2,132	$	16,905

Fair_Value_Tables

Fair Value (Tables)	9 Months Ended
	Sep. 30, 2014
Fair Value Disclosures [Abstract]
Fair Value Assets and Liabilities Measured on a Recurring Basis	At December 31, 2012 and 2013, Level 3 liabilities consisted of convertible preferred stock warrant liabilities. The Company held no financial assets or liabilities measured at fair value on a recurring basis as of September 30, 2014. The following fair value hierarchy tables present information about each major category of the Company’s financial liabilities measured at fair value on a recurring basis as of December 31, 2012 and 2013 (in thousands):
			Fair Value Measurement at December 31, 2012
			Fair Value			Level 1			Level 2		Level 3
	Liabilities:
	Convertible preferred stock warrants(1)		$	2,909		$	—		$	—	$	2,909
	Total liabilities		$	2,909		$	—		$	—	$	2,909
	-1	Convertible preferred stock warrant liabilities to purchase Series A and Series C convertible preferred stock at December 31, 2012 are classified as Level 3 and were measured at fair value using the Black-Scholes-Merton option pricing model. The Company developed its estimates based on publicly available historical data and all available information as of the valuation date. Inputs used in the pricing model include estimates of the Company’s risk-free interest rate, expected dividend yield, expected volatility and expected term. As of December 31, 2012, the warrants were revalued using the Black-Scholes-Merton option pricing model based on the following inputs:
	Fair Value Measurement at December 31, 2013
			Fair Value			Level 1			Level 2		Level 3
	Liabilities:
	Convertible preferred stock warrants(2)		$	646		$	—		$	—	$	646
	Total liabilities		$	646		$	—		$	—	$	646
	-2	Convertible preferred stock warrant liabilities to purchase Series A and Series C convertible preferred stock at December 31, 2013 are classified as Level 3 and are measured using a hybrid of the option pricing model and the PWERM on each reporting date. The key inputs into the models include the probability and timing of expected liquidity events, discount rates and the selection of appropriate market-comparable transactions and multiples to apply to the Company’s various historical and forecasted operational metrics.
Warrants Revalued Using the Black-Scholes-Merton Option Pricing Model	-1	Convertible preferred stock warrant liabilities to purchase Series A and Series C convertible preferred stock at December 31, 2012 are classified as Level 3 and were measured at fair value using the Black-Scholes-Merton option pricing model. The Company developed its estimates based on publicly available historical data and all available information as of the valuation date. Inputs used in the pricing model include estimates of the Company’s risk-free interest rate, expected dividend yield, expected volatility and expected term. As of December 31, 2012, the warrants were revalued using the Black-Scholes-Merton option pricing model based on the following inputs:
			Series A			Series C
	Risk-free interest rate			1.2	%		1.8	%
	Expected dividend yield			0	%		0	%
	Expected volatility			92.2	%		88.2	%
	Expected term (in years)			6.6			9.7
Reconciliation of All Lliabilities Measured at Fair Value Using Level 3 Significant Unobservable Inputs	The following table provides a reconciliation of all liabilities measured at fair value using Level 3 significant unobservable inputs (in thousands):
			Convertible			Convertible
			Preferred Stock			Preferred Stock
			Warrant Liability(1)			Purchase Right(2)
	Balance at December 31, 2011		$	1,632		$	3,707
	Expiration of convertible preferred stock purchase right			—			(3,707	)
	Issuance of convertible preferred stock warrants			1,377			—
	Change in fair value			(100	)		—
	Balance at December 31, 2012			2,909			—
	Issuance of convertible preferred stock warrants			570			—
	Change in fair value			(2,833	)		—
	Balance at December 31, 2013			646			—
	Change in fair value (unaudited)			3,300			—
	Reclassification to additional paid-in capital upon closing of IPO (unaudited)			(3,946	)		—
	Balance at September 30, 2014 (unaudited)		$	—		$	—
	-1	Changes in the fair value of the convertible preferred stock warrant liability were recognized in change in fair value of convertible preferred stock warrant liability in the accompanying statements of operations.
	-2	The change in the fair value of the convertible preferred stock purchase right was recognized in change in fair value of convertible preferred stock purchase right in the accompanying statements of operations.

Convertible_Preferred_Stock_an1

Convertible Preferred Stock and Stockholders' (Deficit) Equity (Tables)	9 Months Ended
	Sep. 30, 2014
Equity [Abstract]
Designated, Issued and OutstandingShares of Convertible Preferred Stock by Series	The designated, issued and outstanding shares of convertible preferred stock by series as of December 31, 2012 are as follows (liquidation preference in thousands):
		Shares		Shares		Common		Liquidation
		Designated		Outstanding		Stock		Preference
						Equivalents
	Series A		406,712		339,863		745,387	$	13,209
	Series B		3,168,373		1,708,076		1,708,076		36,322
			3,575,085		2,047,939		2,453,463	$	49,531
	The designated, issued and outstanding shares of convertible preferred stock by series as of December 31, 2013 are as follows (liquidation preference in thousands):
		Shares		Shares		Common		Liquidation
		Designated		Outstanding		Stock		Preference
						Equivalents
	Series A		404,671		339,863		745,387	$	2,987
	Series B		1,708,076		1,708,076		1,708,076		15,014
	Series C		7,407,062		7,040,026		7,040,026		92,823
			9,519,809		9,087,965		9,493,489	$	110,824
Schedule of Common Stock Reserved for Future Issuance	Common stock reserved for future issuance is as follows in common equivalent shares:
		December 31, 2013		September 30, 2014
	Conversion of convertible preferred stock		9,493,489		—
	Warrants for the purchase of convertible preferred stock		483,517		—
	Warrants for the purchase of common stock		—		142,113
	Common stock options issued and outstanding		1,235,705		2,058,910
	Common stock options available for future grant		537,993		2,602,675
	Common stock reserved for issuance under ESPP		—		380,000
	Total common stock reserved for future issuance		11,750,704		5,183,698

Stock_Compensation_Plans_Table

Stock Compensation Plans (Tables)	9 Months Ended
	Sep. 30, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock Option Activity	The following table summarizes stock option activity for the year ended December 31, 2013 and for the nine months ended September 30, 2014 (in thousands except per share amounts and years):
			Options			Weighted-			Weighted-		Aggregate
						Average			Average		Intrinsic
						Exercise			Remaining		Value
						Price			Contractual
									Term (In Years)
	Outstanding as of December 31, 2012			383		$	2.75
	Granted			862		$	1.76
	Exercised			(2	)	$	3.17
	Forfeited			(7	)	$	2.71
	Outstanding as of December 31, 2013			1,236		$	2.06			9.2	$	47
	Granted			884		$	5.47
	Exercised			(61	)	$	2.51
	Outstanding as of September 30, 2014			2,059		$	3.51			8.9	$	42,189
	Options vested and expected to vest as of December 31, 2013			1,207		$	2.06			9.2	$	47
	Options exercisable as of December 31, 2013			505		$	2.46			8.4	$	15
	Options vested and expected to vest as of September 30, 2014			2,028		$	3.46			9	$	41,659
	Options exercisable as of September 30, 2014			910		$	3.38			7.4	$	18,761
	The following table summarizes certain information regarding stock options (in thousands, except per share data):
			Years Ended						Nine Months Ended
			December 31,						September 30,
			2012			2013			2013		2014
									(unaudited)
	Weighted-average grant date fair value per share of options granted during the period		$	0.79		$	1.28		$	—	$	3.85
	Fair value of options vested during the period			194			206			137		502
	Cash received from options exercised during the period(1)			3			5			5		153
	Intrinsic value of options exercised during the period			—			—			—		111
	-1	For the nine months ended September 30, 2014, cash received from options exercised during the period includes cash proceeds of $54,000 for shares which were early exercised and subject to repurchase as of September 30, 2014. The Company has reflected the early exercise liability within accrued expenses in the accompanying balance sheets.
Weighted-Average Underlying Assumptions Used to Determine Fair Value of Stock Options Granted	The following are the weighted-average underlying assumptions used to determine the fair value of stock options granted to employees and non-employees using the Black-Scholes-Merton option pricing model:
			Years Ended						Nine Months
			December 31,						Ended
									September 30,
			2012			2013			2013(1)		2014
									(unaudited)
	Risk-free interest rate			1	%		2	%		—		1.9	%
	Expected dividend yield			0	%		0	%		—		0	%
	Expected volatility			92.2	%		85.5	%		—		82.3	%
	Expected term (in years)			6.1			6.1			—		6.1
	-1	The Company did not issue any stock options during the nine months ended September 30, 2013.
Summary of Non-cash Stock Based Compensation Expense	Total non-cash stock-based compensation expense recognized in the accompanying statements of operations is as follows (in thousands):
			Years Ended						Nine Months Ended
			December 31,						September 30,
			2012			2013			2013		2014
									(unaudited)
	Research and development		$	78		$	62		$	40	$	407
	General and administrative			113			121			85		488
	Total stock-based compensation		$	191		$	183		$	125	$	895

Related_Party_Transactions_Tab

Related Party Transactions (Tables)	9 Months Ended
	Sep. 30, 2014
Related Party Transactions [Abstract]
Summary of Related Party Receivables, Payables, Payments Made and Expenses Related to Affiliated Companies	The following table summarizes related party receivables, payables, payments made and expenses related to affiliated companies under these agreements (in thousands):
		Years Ended				Nine Months Ended
		December 31,				September 30,
		2012		2013		2013		2014
						(unaudited)
	Receivable	$	17	$	9	$	12	$	—
	Payable		6		10		5		—
	Payments		79		28		14		10
	Expenses		60		32		15		—

Income_Taxes_Tables

Income Taxes (Tables)	9 Months Ended
	Sep. 30, 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,
		2012			2013
	Deferred tax assets:
	Net operating loss carryforwards	$	11,252		$	18,620
	Research and development credits		621			1,363
	Depreciation and amortization		433			906
	Accrued expenses		75			76
	Deferred rent		126			116
	Other, net		27			31
	Total deferred tax assets		12,534			21,112
	Less: valuation allowance		(12,534	)		(21,112	)
	Total	$	—		$	—
Reconciliation of Expected Recovery of Income Taxes	The following is a reconciliation of the expected recovery of income taxes between those that are based on enacted tax rates and laws, to those currently reported for the years ended December 31 (in thousands):
		2012			2013
	Federal statutory rate	$	(2,573	)	$	(6,650	)
	State tax (net of federal benefit)		(628	)		(1,148	)
	Permanent items, other		56			65
	Change in fair value of convertible preferred stock warrant liability		(1,260	)		(963	)
	Change in fair value of convertible preferred stock purchase right		(34	)		—
	Non-deductible interest		150			855
	Other adjustments		10			91
	Research and development credits		(160	)		(1,236	)
	Uncertain tax positions		60			409
	Change in valuation allowance		4,380			8,578
	Provision for income taxes	$	1		$	1
Unrecognized Tax Benefit	The following table summarizes the activity related to our gross unrecognized tax benefits (in thousands):
		December 31,
		2012			2013
	Balance at the beginning of the year	$	422		$	515
	Adjustments related to prior year tax positions		(4	)		136
	Increases related to current year tax positions		97			406
	Decreases due to statute of limitations expiration		—			—
	Decreases due to IRC Section 382/383 limitation		—			—
		$	515		$	1,057

Subsequent_Events_Tables

Subsequent Events (Tables)	9 Months Ended
	Sep. 30, 2014
Subsequent Events [Abstract]
Summary of Preferred Stock Preferences in Connection with Issuance of Series D Convertible Preferred Stock	The following table summarizes the preferred stock preferences in connection with the issuance of the Series D convertible preferred stock:
		Dividend Rate			Conversion Rate	Liquidation
						Preference Per Share
	Series D		8	%	1:01	$	11.96
	Series C		8	%	1:01		8.79
	Series B		8	%	1:01		8.79
	Series A		8	%	0102.2		31.092

Description_of_Business_and_Ba2

Description of Business and Basis of Presentation - Additional Information (Detail) (USD $)	1 Months Ended			9 Months Ended	1 Months Ended
	Aug. 31, 2013	Dec. 31, 2011	31-May-11	Sep. 30, 2014	Aug. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Description Of Business And Basis Of Presentation [Line Items]
Working capital				161,800,000		$36,300,000
Accumulated deficit				92,675,000		59,557,000	39,459,000
Series C Convertible Preferred Stock Warrants [Member]
Description Of Business And Basis Of Presentation [Line Items]
Number of warrants	341,404
Series C Convertible Preferred Stock [Member]
Description Of Business And Basis Of Presentation [Line Items]
Number of shares issued	4,420,577	2,610,917	8,532
IPO [Member] | Series A Preferred Stock Warrants [Member]
Description Of Business And Basis Of Presentation [Line Items]
Number of warrants				142,113
IPO [Member] | Series C Convertible Preferred Stock Warrants [Member]
Description Of Business And Basis Of Presentation [Line Items]
Number of warrants				341,404
IPO [Member] | Series C Convertible Preferred Stock [Member] | Series C Convertible Preferred Stock Warrants [Member]
Description Of Business And Basis Of Presentation [Line Items]
Shares issued upon conversion of convertible preferred stock				92,271
Common stock [Member] | IPO [Member]
Description Of Business And Basis Of Presentation [Line Items]
Number of shares issued					7,187,500
Price per share					$16
Net proceeds from initial public offering					$104,100,000
Common stock [Member] | IPO [Member] | Convertible preferred stock [Member]
Description Of Business And Basis Of Presentation [Line Items]
Shares issued upon conversion of convertible preferred stock					13,619,569
Common stock [Member] | IPO [Member] | Series C Convertible Preferred Stock [Member] | Series C Convertible Preferred Stock Warrants [Member]
Description Of Business And Basis Of Presentation [Line Items]
Shares issued upon conversion of convertible preferred stock					228,902
Common stock [Member] | Over-Allotment Option [Member]
Description Of Business And Basis Of Presentation [Line Items]
Number of shares issued					937,500
Warrants to purchase common stock [Member] | IPO [Member] | Series A Preferred Stock Warrants [Member]
Description Of Business And Basis Of Presentation [Line Items]
Number of warrants					142,113

Summary_of_Significant_Account2

Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	1 Months Ended	9 Months Ended		12 Months Ended
	Aug. 31, 2014	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Dec. 31, 2012
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Impairment loss		$0
Material adjustments to prior period estimates		0		0	0
Change in fair value of convertible preferred stock warrant liability	$2,600,000	$3,300,000	($2,713,000)	($2,833,000)	($100,000)

Summary_of_Significant_Account3

Summary of Significant Accounting Policies - Potentially Dilutive Securities Excluded from Calculation of Diluted Net Loss Per Share Attributable to Common Stockholders (Detail)	9 Months Ended		12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Dec. 31, 2012
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities excluded from the calculation of diluted net loss per share	2,217,317	7,739,464	11,212,711	3,672,578
Convertible preferred stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities excluded from the calculation of diluted net loss per share		6,882,572	9,493,489	2,453,463
Convertible Notes Payable [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities excluded from the calculation of diluted net loss per share				580,580
Convertible Preferred Stock Warrants [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities excluded from the calculation of diluted net loss per share		483,517	483,517	255,013
Warrants to purchase common stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities excluded from the calculation of diluted net loss per share	142,113
Unvested restricted common stock subject to repurchase [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities excluded from the calculation of diluted net loss per share	16,294			859
Options to purchase common stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities excluded from the calculation of diluted net loss per share	2,058,910	373,375	1,235,705	382,663

Balance_Sheet_Details_Prepaid_

Balance Sheet Details - Prepaid and Other Current Assets (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid clinical trial costs	$1,054	$1,478	$500
Other	1,123	176	197
Total	$2,177	$1,654	$697

Balance_Sheet_Details_Property

Balance Sheet Details - Property and Equipment, Net (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$1,893	$1,477	$1,082
Less: accumulated depreciation and amortization	-941	-794	-643
Total	952	683	439
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	1,088	908	827
Manufacturing Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	607	392
Computer Equipment and Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	114	93	102
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	67	67	138
Office Furniture [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$17	$17	$15

Balance_Sheet_Details_Addition

Balance Sheet Details - Additional Information (Detail) (USD $)	9 Months Ended		12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment [Abstract]
Depreciation expense	$0.20	$0.20	$0.30	$0.20

Balance_Sheet_Details_Accrued_

Balance Sheet Details - Accrued Expenses (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Payables and Accruals [Abstract]
Accrued clinical trial costs	$1,892	$196	$197
Accrued other	594	188	118
Total	$2,486	$384	$315

Notes_Payable_and_Convertible_2

Notes Payable and Convertible Preferred Stock Warrants - Additional Information (Detail) (USD $)	1 Months Ended		9 Months Ended		12 Months Ended		3 Months Ended	1 Months Ended
	Aug. 31, 2014	Jul. 31, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Dec. 31, 2012	Oct. 31, 2012	Jan. 31, 2013	Aug. 31, 2013	31-May-10
Debt Instrument [Line Items]
Proceeds from convertible notes payable				$7,009,000	$7,009,000	$8,011,000
Aggregate fair value of convertible preferred stock warrants	2,600,000		3,300,000	-2,713,000	-2,833,000	-100,000
Proceeds from exercise of warrants			1,201,000
Working capital aggregate principal amount		7,000,000
Warrant, exercise price description		The Company issued a warrant for its Series C convertible preferred stock that would become exercisable for 3% of the amount of the debt actually drawn at an exercise price of $0.25 per share.
2012 Notes Payable [Member]
Debt Instrument [Line Items]
Proceeds from convertible notes payable							8,000,000
Debt conversion, converted instrument, minimum gross proceeds					10,000,000
Interest rate of notes							8.00%
Aggregate fair value of convertible preferred stock warrants					1,400,000
2013 Notes Payable [Member]
Debt Instrument [Line Items]
Proceeds from convertible notes payable								7,000,000
Aggregate fair value of convertible preferred stock warrants					600,000
Series C Convertible Preferred Stock [Member]
Debt Instrument [Line Items]
Exercise price of warrants					$8.79
Aggregate fair value of convertible preferred stock warrants					600,000	1,300,000
Amount of debt converted									16,000,000
Shares issued upon conversion of debt									1,818,191
Series C Convertible Preferred Stock [Member] | 2012 Notes Payable [Member]
Debt Instrument [Line Items]
Issued warrants for the purchase					182,082
Exercise price of warrants					$8.79
Series A Convertible Preferred Stock [Member]
Debt Instrument [Line Items]
Aggregate fair value of convertible preferred stock warrants					46,000	1,600,000
Shares issued upon conversion of debt										339,863
Series C Convertible Preferred Stock Warrants [Member]
Debt Instrument [Line Items]
Issued warrants for the purchase									341,404
Exercise price of warrants									$8.79
Series C Convertible Preferred Stock Warrants [Member] | IPO [Member]
Debt Instrument [Line Items]
Issued warrants for the purchase			341,404
Proceeds from exercise of warrants			$1,200,000
Shares converted upon conversion of convertible preferred stock			204,773
Series C Convertible Preferred Stock Warrants [Member] | IPO [Member] | Series C Convertible Preferred Stock [Member]
Debt Instrument [Line Items]
Shares issued upon conversion of convertible preferred stock			92,271
Shares issued upon conversion of convertible preferred stock			136,631
Series A Preferred Stock Warrants [Member] | IPO [Member]
Debt Instrument [Line Items]
Issued warrants for the purchase			142,113
Exercise price of warrants			$14.18

Outstanding_Convertible_Prefer

Outstanding Convertible Preferred Stock Warrants (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2013
Class of Warrant or Right [Line Items]
Warrants Outstanding	324,195	483,517
Series A Convertible Preferred Stock [Member] | Range One [Member]
Class of Warrant or Right [Line Items]
Issue Date	4-Nov-08
Exercise Price	$31.09
Warrants Outstanding	14,106
Expiration Date	4-Nov-18
Series A Convertible Preferred Stock [Member] | Range Two [Member]
Class of Warrant or Right [Line Items]
Issue Date	8-Dec-08
Exercise Price	$31.09
Warrants Outstanding	14,106
Expiration Date	8-Dec-18
Series A Convertible Preferred Stock [Member] | Range Three [Member]
Class of Warrant or Right [Line Items]
Issue Date	14-Jan-09
Exercise Price	$31.09
Warrants Outstanding	14,106
Expiration Date	14-Jan-19
Series A Convertible Preferred Stock [Member] | Range Four [Member]
Class of Warrant or Right [Line Items]
Issue Date	13-Apr-09
Exercise Price	$31.09
Warrants Outstanding	14,106
Expiration Date	13-Apr-19
Series A Convertible Preferred Stock [Member] | Range Five [Member]
Class of Warrant or Right [Line Items]
Issue Date	1-Jul-09
Exercise Price	$31.09
Warrants Outstanding	14,106
Expiration Date	1-Jul-19
Series A Convertible Preferred Stock [Member] | Range Six [Member]
Class of Warrant or Right [Line Items]
Issue Date	8-Oct-09
Exercise Price	$31.09
Warrants Outstanding	14,106
Expiration Date	8-Oct-19
Series A Convertible Preferred Stock [Member] | Range Seven [Member]
Class of Warrant or Right [Line Items]
Issue Date	15-Dec-09
Exercise Price	$31.09
Warrants Outstanding	14,106
Expiration Date	15-Dec-19
Series A Convertible Preferred Stock [Member] | Range Eight [Member]
Class of Warrant or Right [Line Items]
Issue Date	22-Jan-10
Exercise Price	$31.09
Warrants Outstanding	14,106
Expiration Date	22-Jan-20
Series A Convertible Preferred Stock [Member] | Range Nine [Member]
Class of Warrant or Right [Line Items]
Issue Date	15-Mar-10
Exercise Price	$31.09
Warrants Outstanding	703
Expiration Date	15-Mar-20
Series A Convertible Preferred Stock [Member] | Range Ten [Member]
Class of Warrant or Right [Line Items]
Issue Date	1-Apr-10
Exercise Price	$31.09
Warrants Outstanding	14,106
Expiration Date	1-Apr-20
Series A Convertible Preferred Stock [Member] | Range Eleven [Member]
Class of Warrant or Right [Line Items]
Issue Date	28-May-10
Exercise Price	$31.09
Warrants Outstanding	14,456
Expiration Date	28-May-20
Series C Convertible Preferred Stock [Member]
Class of Warrant or Right [Line Items]
Issue Date		22-Jan-13
Exercise Price		$8.79
Warrants Outstanding		159,322
Expiration Date		22-Jan-23
Series C Convertible Preferred Stock [Member] | Range Twelve [Member]
Class of Warrant or Right [Line Items]
Issue Date	23-Aug-12
Exercise Price	$8.79
Warrants Outstanding	182,022
Expiration Date	23-Aug-22
Series C Convertible Preferred Stock [Member] | Range Thirteen [Member]
Class of Warrant or Right [Line Items]
Issue Date	24-Oct-12
Exercise Price	$8.79
Warrants Outstanding	60
Expiration Date	24-Oct-22

Non_cash_Interest_Expense_Deta

Non cash Interest Expense (Detail) (USD $)	9 Months Ended		12 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Dec. 31, 2012
Debt Disclosure [Abstract]
Stated interest on convertible notes payable		$749	$749	$228
Amortization of deferred financing costs associated with the convertible preferred stock warrants	39	1,775	1,779	216
Total interest expense	$39	$2,524	$2,528	$444

Commitments_and_Contingencies_1

Commitments and Contingencies - Additional Information (Detail) (USD $)	9 Months Ended		12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Dec. 31, 2012
Other Commitments [Line Items]
Rent expense	$300,000	$300,000	$400,000	$400,000
Intellectual Property [Member]
Other Commitments [Line Items]
Annual license and maintenance fees	25,000
Common stock, shares issued as compensation for license	710
Number of milestones achieved	5
Milestone fees	1,200,000
Maximum percentage of royalties on sales	5.00%
Royalty Agreements [Member]
Other Commitments [Line Items]
Milestone fees	$500,000
Maximum percentage of royalties on sales	1.00%
Number of provisional patents	3
Royalty period	10 years

Operating_Lease_Obligations_De

Operating Lease Obligations (Detail) (USD $)	Dec. 31, 2013
In Thousands, unless otherwise specified
Commitments and Contingencies Disclosure [Abstract]
2014	$471
2015	473
2016	487
2017	82
Total	$1,513

Commitments_and_Contingencies_2

Commitments and Contingencies - Summary of Costs Recognized Under License Agreements and Other Non-Cancellable Royalty and Milestone Obligations (Detail) (License Agreements [Member], USD $)	9 Months Ended		12 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Dec. 31, 2012
License Agreements [Member]
Other Commitments [Line Items]
License and other fees	$19	$44	$250	$25
Milestone fees		100	1,100
Total license and related fees	$19	$144	$1,350	$25

Commitments_and_Contingencies_3

Commitments and Contingencies - Schedule of Additional Milestone Payments (Detail) (USD $)	9 Months Ended
In Thousands, except Share data, unless otherwise specified	Sep. 30, 2014
Other Commitments [Line Items]
Shares of Common Stock	2,132
Cash Payments	$16,905
Development [Member]
Other Commitments [Line Items]
Shares of Common Stock	1,066
Cash Payments	3,235
Regulatory [Member]
Other Commitments [Line Items]
Shares of Common Stock	1,066
Cash Payments	12,670
Commercialization [Member]
Other Commitments [Line Items]
Cash Payments	$1,000

Fair_Value_Fair_Value_Assets_a

Fair Value - Fair Value Assets and Liabilities Measured on a Recurring Basis (Detail) (USD $)	Dec. 31, 2013		Dec. 31, 2012
In Thousands, unless otherwise specified
Liabilities:
Convertible preferred stock warrants	$646	[1]	$2,909	[2]
Total liabilities	646		2,909
Level 3 [Member]
Liabilities:
Convertible preferred stock warrants	646	[1]	2,909	[2]
Total liabilities	$646		$2,909
[1]	Convertible preferred stock warrant liabilities to purchase Series A and Series C convertible preferred stock at December 31, 2013 are classified as Level 3 and are measured using a hybrid of the option pricing model and the PWERM on each reporting date.
[2]	Convertible preferred stock warrant liabilities to purchase Series A and Series C convertible preferred stock at December 31, 2012 are classified as Level 3 and were measured at fair value using the Black-Scholes-Merton option pricing model.

Warrant_revalued_Pricing_Model

Warrant revalued Pricing Model Inputs (Detail)	12 Months Ended
	Dec. 31, 2013
Series A Convertible Preferred Stock Warrants [Member]
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Risk-free interest rate	1.20%
Expected dividend yield	0.00%
Expected volatility	92.20%
Expected term (in years)	6 years 7 months 6 days
Series C Convertible Preferred Stock Warrants [Member]
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Risk-free interest rate	1.80%
Expected dividend yield	0.00%
Expected volatility	88.20%
Expected term (in years)	9 years 8 months 12 days

Fair_Value_Reconciliation_of_t

Fair Value - Reconciliation of the Convertible Preferred Stock Warrant Liabilities Measured at Fair Value, Unobservable Inputs (Detail) (USD $)	9 Months Ended		12 Months Ended				1 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014		Dec. 31, 2013		Dec. 31, 2012		Jun. 30, 2012
Convertible Preferred Stock Warrant Liability [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	$646	[1]	$2,909	[1]	$1,632	[1]
Issuance of convertible preferred stock warrants			570	[1]	1,377	[1]
Change in fair value	3,300	[1]	-2,833	[1]	-100	[1]
Reclassification to additional paid-in capital upon closing of IPO	-3,946	[1]
Ending balance			646	[1]	2,909	[1]
Convertible Preferred Stock Purchase Right [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance					3,707	[2]
Expiration of convertible preferred stock purchase right					($3,707)	[2]	$3,700
[1]	Changes in the fair value of the convertible preferred stock warrant liability were recognized in change in fair value of convertible preferred stock warrant liability in the accompanying statements of operations.
[2]	The change in the fair value of the convertible preferred stock purchase right was recognized in change in fair value of convertible preferred stock purchase right in the accompanying statements of operations.

Fair_Value_Additional_informat

Fair Value - Additional information (Detail) (USD $)	0 Months Ended	1 Months Ended				12 Months Ended
	18-May-11	31-May-11	Feb. 28, 2011	Aug. 31, 2010	Jun. 30, 2012	Dec. 31, 2013	Dec. 31, 2012
Series B Convertible Preferred Stock [Member]
Assets And Liabilities Carrying Value And Fair Value [Line Items]
Stock issued during period shares new issues	996,382	996,382	3,664	708,030
Stock issued during period value new issues	$1,200,000
Convertible Preferred Stock Purchase Right [Member]
Assets And Liabilities Carrying Value And Fair Value [Line Items]
Fair value of convertible preferred stock purchase right upon issuance						3,800,000
Change in fair value of convertible preferred purchase right					$3,700,000		($3,707,000)	[1]
[1]	The change in the fair value of the convertible preferred stock purchase right was recognized in change in fair value of convertible preferred stock purchase right in the accompanying statements of operations.

Convertible_Preferred_Stock_an2

Convertible Preferred Stock and Stockholders' Equity (Deficit) - Additional Information (Detail) (USD $)	1 Months Ended		9 Months Ended		12 Months Ended					0 Months Ended	1 Months Ended				0 Months Ended
	Aug. 31, 2013	31-May-10	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2012	Dec. 31, 2009	18-May-11	31-May-11	Feb. 28, 2011	Aug. 31, 2010	Dec. 31, 2011	Apr. 23, 2014
Class of Stock [Line Items]
Debt instrument, amount converted	$16,000,000	$10,600,000
Shares authorized to be issued			0		9,519,809			3,575,085
Proceed from issuance of convertible preferred stock			49,239,000	22,641,000	45,585,000
Aggregate amount of redemption requirement			79,800,000
Scenario, Forecast [Member]
Class of Stock [Line Items]
Amount redeemable in each of the years ending						39,900,000	39,900,000
Unvested restricted common stock subject to repurchase [Member]
Class of Stock [Line Items]
Share price per share									$0.00
Shares of restricted common stock sold									11,621
Vesting description									25% after one year and then monthly over the following three years
Shares vested								10,828
Common Stock Subject to Repurchase [Member]
Class of Stock [Line Items]
Early exercised option awards			16,294		0
Early exercised option awards liability			54,000
Shares repurchased			0
Series A Convertible Preferred Stock [Member]
Class of Stock [Line Items]
Share price per share		$31.09
Shares issued upon conversion of debt		339,863
Shares authorized to be issued			0		404,671			406,712
Preferred stock, dividend rate			8.00%
Preferred stock, liquidation preference	$38.87		$31.09
Preferred stock conversion ratio			2.193204365
Series B Convertible Preferred Stock [Member]
Class of Stock [Line Items]
Share price per share											$14.18	$14.18	$14.18
Shares authorized to be issued			0		1,708,076			3,168,373					1,708,076
Shares issued										996,382	996,382	3,664	708,030
Proceed from issuance of convertible preferred stock											14,100,000	100,000	10,000,000
Preferred stock, dividend rate			8.00%
Preferred stock, liquidation preference	$21.26		$8.79
Preferred stock conversion ratio			1
Series C Convertible Preferred Stock [Member]
Class of Stock [Line Items]
Share price per share	$8.79										$8.79			$8.79
Shares issued upon conversion of debt	1,818,191
Shares authorized to be issued	7,040,026		0		7,407,062			0
Shares issued	4,420,577										8,532			2,610,917
Proceed from issuance of convertible preferred stock	22,600,000										100,000			22,900,000
Preferred stock, dividend rate			8.00%
Preferred stock, liquidation preference			$8.79
Preferred stock conversion ratio			1
Convertible preferred stock [Member]
Class of Stock [Line Items]
Preferred stock dividends			0
Preferred stock, dividend per share			$26.37
Convertible preferred stock, conversion description			Each share of convertible preferred stock is automatically converted into common stock immediately upon: (i)B the Companybs sale of its common stock in a firm commitment underwritten public offering pursuant to a registration statement under the Securities Act of 1933, as amended, in which the per share price is at least $43.95 (as adjusted) and the net cash proceeds are at least $75,000,000 or (ii)B upon the written consent of the holders of at least 64% of the then outstanding Series C convertible preferred stock (the Requisite Holders)
Sale of common stock per share			$43.95
Proceeds from issuance of common stock			75,000,000
Preferred stock, written consent for conversion percent			64.00%
Series D Convertible Preferred Stock [Member]
Class of Stock [Line Items]
Share price per share															$11.96
Shares issued															4,126,080
Proceed from issuance of convertible preferred stock															$49,200,000
Series C Convertible Preferred Stock [Member]
Class of Stock [Line Items]
Shares issued					7,040,026
Preferred stock, liquidation preference			$13.19
Series B Convertible Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock, liquidation preference			$8.79
Series A Convertible Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock, liquidation preference			$8.79
Series D Convertible Preferred Stock [Member]
Class of Stock [Line Items]
Shares issued			4,126,080
Preferred stock, dividend rate			8.00%
Preferred stock, liquidation preference			$11.96
Preferred stock conversion ratio			1

Convertible_Preferred_Stock_an3

Convertible Preferred Stock and Stockholders' Equity (Deficit) - Designated, Issued and Outstanding Shares of Convertible Preferred Stock by Series (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013	Dec. 31, 2012	Aug. 31, 2010	Aug. 31, 2013
In Thousands, except Share data, unless otherwise specified
Temporary Equity [Line Items]
Shares Designated	0	9,519,809	3,575,085
Shares Outstanding		9,087,965	2,047,939
Shares Issued		9,087,965	2,047,939
Common Stock Equivalents		9,493,489	2,453,463
Liquidation Preference		$110,824	$49,531
Series A Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Shares Designated	0	404,671	406,712
Shares Outstanding	0	339,863	339,863
Shares Issued	0	339,863	339,863
Common Stock Equivalents		745,387	745,387
Liquidation Preference	0	2,987	13,209
Series B Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Shares Designated	0	1,708,076	3,168,373	1,708,076
Shares Outstanding	0	1,708,076	1,708,076
Shares Issued	0	1,708,076	1,708,076
Common Stock Equivalents		1,708,076	1,708,076
Liquidation Preference	0	15,014	36,322
Series C Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Shares Designated	0	7,407,062	0		7,040,026
Shares Outstanding	0	7,040,026
Shares Issued	0	7,040,026
Common Stock Equivalents		7,040,026
Liquidation Preference	0	$92,823

Convertible_Preferred_Stock_an4

Convertible Preferred Stock and Stockholders' Equity (Deficit) - Schedule of Common Stock Reserved for Future Issuance (Detail)	Sep. 30, 2014	Dec. 31, 2013
Class of Stock [Line Items]
Total common stock reserved for future issuance	5,183,698	11,750,704
Convertible preferred stock [Member]
Class of Stock [Line Items]
Total common stock reserved for future issuance		9,493,489
Convertible Preferred Stock Warrants [Member]
Class of Stock [Line Items]
Total common stock reserved for future issuance		483,517
Warrants to purchase common stock [Member]
Class of Stock [Line Items]
Total common stock reserved for future issuance	142,113
Common stock options issued and outstanding [Member]
Class of Stock [Line Items]
Total common stock reserved for future issuance	2,058,910	1,235,705
Common stock options available for future grant [Member]
Class of Stock [Line Items]
Total common stock reserved for future issuance	2,602,675	537,993
2014 Employee Stock Purchase Plan [Member]
Class of Stock [Line Items]
Total common stock reserved for future issuance	380,000

Stock_Compensation_Plans_Addit

Stock Compensation Plans - Additional Information (Detail) (USD $)	3 Months Ended	9 Months Ended	12 Months Ended
In Millions, except Share data, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2014	Dec. 31, 2013	Jul. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common shares reserved for issuance	5,183,698	5,183,698	11,750,704
Number of common stock issued pursuant to ESPP purchases	0	0
Unrecognized compensation cost related to stock options	$3.90	$3.90	$1.30
Remaining weighted-average vesting period		3 years 6 months	3 years 3 months 18 days
Equity Incentive Plan 2010 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Description of stock option plan		Plan, including (i) the number of shares of common stock subject to the award; (ii) when the award becomes exercisable; (iii) the option or stock appreciation right exercise price, which must be at least 100% of the fair market value of the common stock as of the date of grant; and (iv) the duration of the option or stock appreciation right (which may not exceed 10 years).
Stock option plan, vesting period		4 years
Options available for grant			537,993
Equity Incentive Plan 2010 [Member] | Option or stock appreciation Right [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price, percentage of fair market value		100.00%
Options granted rights		Options granted under the 2010 Plan generally are scheduled to vest over four years, subject to continued service, and subject to certain acceleration of vesting provisions, and expire no later than 10 years from the date of grant.
Contractual term of options		10 years
Equity Incentive Plan 2014 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common shares reserved for issuance				2,606,875
Annual increase in common shares reserved for issuance		2,500,000
Annual increase in common shares reserved for issuance, percentage of total shares of common stock		5.00%
Changes in share issuance, description		The number of shares available for issuance under the 2014 Plan will also include an annual increase on the first day of each fiscal year beginning in 2015, equal to the least of (i) 2,500,000 shares; (ii) 5% of the outstanding shares of common stock as of the last day of the immediately preceding fiscal year; or (iii) such other amount as the Company's board of directors may determine.
Options available for grant	2,602,675	2,602,675
Equity Incentive Plan 2014 [Member] | Portion of Common Shares Reserved for Future Issuance From Predecessor Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common shares reserved for issuance				386,875
Equity Incentive Plan 2014 [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Contractual term of options		10 years
Equity Incentive Plan 2014 [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price, percentage of fair market value		100.00%
2014 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common shares reserved for issuance	380,000	380,000
Annual increase in common shares reserved for issuance		800,000
Annual increase in common shares reserved for issuance, percentage of total shares of common stock		1.50%
Changes in share issuance, description		Issuance under the ESPP will also include an annual increase on the first day of each fiscal year beginning in 2015, equal to the least of (i) 800,000 shares; (ii) 1.5% of the outstanding shares of common stock as of the last day of the immediately preceding fiscal year; or (iii) such other amount as the Company's board of directors may determine.
Offering periods under plan		24 months
Offering period description		The offering periods generally start on the first trading day on or after June 1 and December 1 of each year and end on the first trading day on or before June 1 and December 1 approximately twenty-four months later, and will include six-month purchase periods.
2014 Employee Stock Purchase Plan [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Eligible compensation contribution		15.00%

Stock_Compensation_Plans_Stock

Stock Compensation Plans - Stock Option Activity (Detail) (USD $)	9 Months Ended	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Options
Outstanding as of beginning of period	1,236	383
Granted	884	862
Exercised	-61	-2
Forfeited		-7
Outstanding as of end of period	2,059	1,236
Options vested and expected to vest	2,028	1,207
Options exercisable	910	505
Weighted- Average Exercise Price
Outstanding as of beginning of period	$2.06	$2.75
Granted	$5.47	$1.76
Exercised	$2.51	$3.17
Forfeited		$2.71
Outstanding as of end of period	$3.51	$2.06
Options vested and expected to vest	$3.46	$2.06
Options exercisable	$3.38	$2.46
Weighted-Average Remaining Contractual Term (In Years)
Outstanding	8 years 10 months 24 days	9 years 2 months 12 days
Options vested and expected to vest	9 years	9 years 2 months 12 days
Options exercisable	7 years 4 months 24 days	8 years 4 months 24 days
Aggregate Intrinsic Value
Outstanding	$42,189	$47
Options vested and expected to vest	41,659	47
Options exercisable	$18,761	$15

Stock_Compensation_Plans_Infor

Stock Compensation Plans - Information Regarding Stock Options (Detail) (USD $)	9 Months Ended				12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2014		Sep. 30, 2013		Dec. 31, 2013		Dec. 31, 2012
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Weighted-average grant date fair value per share of options granted during the period	$3.85				$1.28		$0.79
Fair value of options vested during the period	$502		$137		$206		$194
Cash received from options exercised during the period	153	[1]	5	[1]	5	[1]	3	[1]
Intrinsic value of options exercised during the period	$111
[1]	For the nine months ended September 30, 2014, cash received from options exercised during the period includes cash proceeds of $54,000 for shares which were early exercised and subject to repurchase as of September 30, 2014. The Company has reflected the early exercise liability within accrued expenses in the accompanying balance sheets.

Stock_Compensation_Plans_Infor1

Stock Compensation Plans - Information Regarding Stock Options (Parenthetical) (Detail) (USD $)	9 Months Ended				12 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014		Sep. 30, 2013		Dec. 31, 2013		Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cash received from options exercised during the period	$153	[1]	$5	[1]	$5	[1]	$3	[1]
Early Exercised Options Subject To Repurchase [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cash received from options exercised during the period	$54
[1]	For the nine months ended September 30, 2014, cash received from options exercised during the period includes cash proceeds of $54,000 for shares which were early exercised and subject to repurchase as of September 30, 2014. The Company has reflected the early exercise liability within accrued expenses in the accompanying balance sheets.

Stock_Compensation_Plans_Weigh

Stock Compensation Plans - Weighted-Average Underlying Assumptions Used to Determine Fair Value of Stock Options Granted (Detail)	9 Months Ended			12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013		Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Risk-free interest rate	1.90%		[1]	2.00%	1.00%
Expected dividend yield	0.00%		[1]	0.00%	0.00%
Expected volatility	82.30%		[1]	85.50%	92.20%
Expected term (in years)	6 years 1 month 6 days			6 years 1 month 6 days	6 years 1 month 6 days
[1]	The Company did not issue any stock options during the nine months ended September 30, 2013.

Stock_Compensation_Plans_Summa

Stock Compensation Plans - Summary of Non-cash Stock Based Compensation Expense (Detail) (USD $)	9 Months Ended		12 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation	$895	$125	$183	$191
Research and development [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation	407	40	62	78
General and administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation	$488	$85	$121	$113

Summary_of_Related_Party_Recei

Summary of Related Party Receivables, Payables, Payments Made and Expenses Related to Affiliated Companies (Detail) (USD $)	9 Months Ended		12 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Dec. 31, 2012
Commitment, Contingency And Related Party Transactions [Abstract]
Receivable		$12	$9	$17
Payable		5	10	6
Payments	10	14	28	79
Expenses		$15	$32	$60

Income_Taxes_Additional_Inform

Income Taxes - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Income Taxes [Line Items]
Deferred tax assets, operating loss carryforwards	$18,620,000	$11,252,000
Deferred tax assets, research and development	1,363,000	621,000
Valuation allowance	21,112,000	12,534,000
Domestic Tax Authority [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	46,800,000
Net operating loss carryforwards, expiration	Will begin to expire in 2030
Tax credit carryforwards	1,600,000
Tax credit carryforwards, expiration	Will begin expiring in 2030
CALIFORNIA
Income Taxes [Line Items]
Net operating loss carryforwards	46,600,000
Net operating loss carryforwards, expiration	Will begin to expire in 2030
Tax credit carryforwards	1,100,000
Tax credit carryforwards, expiration	Will begin expiring in 2030
Change in Ownership [Member]
Income Taxes [Line Items]
Deferred tax assets, operating loss carryforwards	3,200,000
Change in Ownership [Member] | Domestic Tax Authority [Member]
Income Taxes [Line Items]
Deferred tax assets, research and development	$300,000

Components_of_Deferred_Tax_Ass

Components of Deferred Tax Assets (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Deferred tax assets:
Net operating loss carryforwards	$18,620	$11,252
Research and development credits	1,363	621
Depreciation and amortization	906	433
Accrued expenses	76	75
Deferred rent	116	126
Other, net	31	27
Total deferred tax assets	21,112	12,534
Less: valuation allowance	-21,112	-12,534
Total	$0	$0

Income_Taxes_Reconciliation_of

Income Taxes - Reconciliation of Expected Recovery of Income Taxes (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Federal statutory rate	($6,650)	($2,573)
State tax (net of federal benefit)	-1,148	-628
Permanent items, other	65	56
Change in fair value of convertible preferred stock warrant liability	-963	-1,260
Change in fair value of convertible preferred stock purchase right		-34
Non-deductible interest	855	150
Other adjustments	91	10
Research and development credits	-1,236	-160
Uncertain tax positions	409	60
Change in valuation allowance	8,578	4,380
Provision for income taxes	$1	$1

Income_Taxes_Activity_Related_

Income Taxes - Activity Related to Gross Unrecognized Tax Benefits (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Balance at the beginning of the year	$515	$422
Adjustments related to prior year tax positions	136	-4
Increases related to current year tax positions	406	97
Decreases due to statute of limitations expiration	0	0
Decreases due to IRC Section 382/383 limitation	0	0
Unrecognized Tax Benefits	$1,057	$515

Subsequent_Events_Additional_I

Subsequent Events - Additional Information (Detail) (USD $)

9 Months Ended

12 Months Ended

0 Months Ended

1 Months Ended

12 Months Ended

Sep. 30, 2014

Sep. 30, 2013

Dec. 31, 2013

Dec. 31, 2020

Dec. 31, 2019

Apr. 23, 2014

18-May-11

31-May-11

Feb. 28, 2011

Aug. 31, 2010

Aug. 31, 2013

Dec. 31, 2011

Dec. 31, 2021

31-May-10

Subsequent Events [Line Items]

Proceed from issuance of convertible preferred stock

$49,239,000

$22,641,000

$45,585,000

Aggregate amount of redemption requirement

79,800,000

Reverse stock split description

On July 31, 2014, the Company filed an amendment to its amended and restated certificate of incorporation, affecting a one-for-35.16 reverse stock split of its outstanding common and convertible preferred stock, which was approved by the Company's board of directors on July 29, 2014.

Reverse stock split conversion ratio

0.0284414

Scenario, Forecast [Member]

Subsequent Events [Line Items]

Amount redeemable in each of the years ending

39,900,000

39,900,000

Series D Convertible Preferred Stock [Member]

Subsequent Events [Line Items]

Shares issued

4,126,080

Share price per share

$11.96

Proceed from issuance of convertible preferred stock

49,200,000

Series A Convertible Preferred Stock [Member]

Subsequent Events [Line Items]

Share price per share

$31.09

Preferred stock conversion ratio

2.193204365

Series B Convertible Preferred Stock [Member]

Subsequent Events [Line Items]

Shares issued

996,382

996,382

3,664

708,030

Share price per share

$14.18

$14.18

$14.18

Proceed from issuance of convertible preferred stock

14,100,000

100,000

10,000,000

Preferred stock conversion ratio

1

Series C Convertible Preferred Stock [Member]

Subsequent Events [Line Items]

Shares issued

8,532

4,420,577

2,610,917

Share price per share

$8.79

$8.79

$8.79

Proceed from issuance of convertible preferred stock

100,000

22,600,000

22,900,000

Preferred stock conversion ratio

1

Series D Convertible Preferred Stock [Member]

Subsequent Events [Line Items]

Shares issued

4,126,080

Preferred stock conversion ratio

1

Convertible preferred stock [Member]

Subsequent Events [Line Items]

Convertible preferred stock, conversion description

Each share of convertible preferred stock is automatically converted into common stock immediately upon: (i)B the Companybs sale of its common stock in a firm commitment underwritten public offering pursuant to a registration statement under the Securities Act of 1933, as amended, in which the per share price is at least $43.95 (as adjusted) and the net cash proceeds are at least $75,000,000 or (ii)B upon the written consent of the holders of at least 64% of the then outstanding Series C convertible preferred stock (the Requisite Holders)

Sale of common stock per share

$43.95

Proceeds from issuance of common stock

75,000,000

Preferred stock, written consent for conversion percent

64.00%

Subsequent Event [Member]

Subsequent Events [Line Items]

Aggregate amount of redemption requirement

136,800,000

Subsequent Event [Member] | Scenario, Forecast [Member]

Subsequent Events [Line Items]

Amount redeemable in each of the years ending

68,400,000

68,400,000

Subsequent Event [Member] | Series D Convertible Preferred Stock [Member]

Subsequent Events [Line Items]

Shares issued

4,126,080

Share price per share

$11.96

Proceed from issuance of convertible preferred stock

49,200,000

Subsequent Event [Member] | Convertible preferred stock [Member]

Subsequent Events [Line Items]

Convertible preferred stock, conversion description

Each share of convertible preferred stock is automatically converted into common stock immediately upon: (i) the Companybs sale of its common stock in a firm commitment underwritten public offering pursuant to a registration statement under the Securities Act of 1933, as amended, in which the per share price is at least $35.87 (as adjusted) and the net cash proceeds are at least $70,000,000 or (ii) upon the written consent of the holders of at least 75% of the then outstanding preferred stock on an as converted basis (the Preferred Stockholders)

Sale of common stock per share

$35.87

Proceeds from issuance of common stock

$70,000,000

Preferred stock, written consent for conversion percent

75.00%

Summary_of_Preferred_Stock_Pre

Summary of Preferred Stock Preferences in Connection with Issuance of Series D Convertible Preferred Stock (Detail) (USD $)	9 Months Ended
	Sep. 30, 2014	Aug. 31, 2013
Series D Convertible Preferred Stock [Member]
Convertible Preferred Stock [Line Items]
Dividend Rate	8.00%
Preferred stock conversion ratio	1
Liquidation Preference Per Share	$11.96
Series C Convertible Preferred Stock [Member]
Convertible Preferred Stock [Line Items]
Dividend Rate	8.00%
Preferred stock conversion ratio	1
Liquidation Preference Per Share	$8.79
Series B Convertible Preferred Stock [Member]
Convertible Preferred Stock [Line Items]
Dividend Rate	8.00%
Preferred stock conversion ratio	1
Liquidation Preference Per Share	$8.79	$21.26
Series A Convertible Preferred Stock [Member]
Convertible Preferred Stock [Line Items]
Dividend Rate	8.00%
Preferred stock conversion ratio	2.193204365
Liquidation Preference Per Share	$31.09	$38.87