Immunic (IMUX) 10-Q 13 Nov 14 2014 Q3 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	9 Months Ended
	Sep. 30, 2014	Nov. 07, 2014
Document And Entity Information [Abstract]	'	'
Document Type	'10-Q	'
Amendment Flag	'false	'
Document Period End Date	30-Sep-14	'
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus	'Q3	'
Trading Symbol	'VTL	'
Entity Registrant Name	'VITAL THERAPIES INC	'
Entity Central Index Key	'0001280776	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Non-accelerated Filer	'
Entity Common Stock, Shares Outstanding	'	23,845,220

Condensed_Consolidated_Balance

Condensed Consolidated Balance Sheets (Unaudited) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Current assets:	'	'
Cash and cash equivalents	$79,091	$38,186
Restricted cash	1,456	963
Deferred financing costs	429	3,506
Other current assets and prepaid expenses	1,607	1,200
Total current assets	82,583	43,855
Property and equipment, net	2,985	2,467
Other assets	263	263
Total assets	85,831	46,585
Current liabilities:	'	'
Accounts payable	696	1,224
Accrued expenses	7,530	3,253
Other current liabilities	272	369
Future purchase rights liabilities	'	2,600
Total current liabilities	8,498	7,446
Other long-term liabilities	283	321
Commitments and contingencies	'	'
Stockholders' equity (deficit):	'	'
Preferred stock, $0.0001 par value; 20,000,000 and 25,000,000 (4,498,599 undesignated) authorized at September 30, 2014 and December 31, 2013, respectively; no shares issued or outstanding at September 30, 2014 and December 31, 2013	'	'
Common stock, $0.0001 par value; 130,000,000 and 29,250,000 shares authorized at September 30, 2014 and December 31, 2013, respectively; 21,790,864 and 606,238 shares issued and outstanding at September 30, 2014 and December 31, 2013, respectively	2	'
Additional paid-in capital	213,831	58,413
Accumulated other comprehensive income	95	96
Accumulated deficit	-136,878	-103,166
Total stockholders' equity (deficit)	77,050	-44,657
Total liabilities, redeemable convertible preferred stock, and stockholders' equity (deficit)	85,831	46,585
Convertible Preferred Stock (Junior) [Member]	'	'
Current liabilities:	'	'
Convertible preferred stock	'	1,359
Redeemable Convertible Preferred Stock (Senior) [Member]	'	'
Current liabilities:	'	'
Convertible preferred stock	'	$82,116

Condensed_Consolidated_Balance1

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) (USD $)	Sep. 30, 2014	Dec. 31, 2013
Preferred stock, par value	$0.00	$0.00
Preferred stock, shares authorized	20,000,000	25,000,000
Preferred stock, shares authorized undesignated	'	4,498,599
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$0.00	$0.00
Common stock, shares authorized	130,000,000	29,250,000
Common stock, shares issued	21,790,864	606,238
Common stock, shares outstanding	21,790,864	606,238
Convertible Preferred Stock (Junior) [Member]	'	'
Convertible preferred stock, par value	$0.00	$0.00
Convertible preferred stock, shares designated	0	3,501,401
Convertible preferred stock, shares issued	0	3,501,400
Convertible preferred stock, shares outstanding	0	3,501,400
Redeemable Convertible Preferred Stock (Senior) [Member]	'	'
Convertible preferred stock, par value	$0.00	$0.00
Convertible preferred stock, shares designated	0	17,000,000
Convertible preferred stock, shares issued	0	10,212,007
Convertible preferred stock, shares outstanding	0	10,212,007

Condensed_Consolidated_Stateme

Condensed Consolidated Statements of Operations (Unaudited) (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Share data, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Operating expenses:	'	'	'	'
Research and development	$10,244	$6,163	$28,589	$14,133
General and administrative	2,566	3,002	7,736	7,021
Total operating expenses	12,810	9,165	36,325	21,154
Loss from operations	-12,810	-9,165	-36,325	-21,154
Other income (expense):	'	'	'	'
Interest income	5	1	13	4
Other income (expense), net	7	-5	'	-9
Revaluation of future purchase rights liabilities	'	2,192	2,600	-1,320
Total other income (expense)	12	2,188	2,613	-1,325
Net loss	-12,798	-6,977	-33,712	-22,479
Amortization of deemed dividend	'	-10	-4,744	-21
Accretion to redemption value of redeemable convertible preferred stock	'	-2,047	-4,410	-4,132
Net loss attributable to common stockholders	($12,798)	($9,034)	($42,866)	($26,632)
Net loss per share attributable to common stockholders, basic and diluted	($0.59)	($16.31)	($3.18)	($52.25)
Weighted-average common shares outstanding, basic and diluted	21,759,061	553,790	13,483,813	509,662

Condensed_Consolidated_Stateme1

Condensed Consolidated Statements of Comprehensive Loss (Unaudited) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Statement of Comprehensive Income [Abstract]	'	'	'	'
Net loss	($12,798)	($6,977)	($33,712)	($22,479)
Other comprehensive income:	'	'	'	'
Foreign currency translation	'	1	-1	7
Total comprehensive loss	($12,798)	($6,976)	($33,713)	($22,472)

Condensed_Consolidated_Stateme2

Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013
Cash flows from operating activities:	'	'
Net loss	($33,712)	($22,479)
Adjustments to reconcile net loss to net cash used in operating activities:	'	'
Depreciation and amortization	853	568
Stock-based compensation	1,765	591
Revaluation of future purchase rights liabilities	-2,600	1,320
Other	91	'
Changes in operating assets and liabilities:	'	'
Other current assets and prepaid expenses	-406	-1,001
Accounts payable	-142	249
Accrued expenses	3,719	2,239
Net cash used in operating activities	-30,432	-18,513
Cash flows from investing activities:	'	'
Purchases of short-term investments	'	-2,999
Sales of short-term investments	'	17,000
Increase in restricted cash	-492	-390
Purchases of property and equipment	-1,365	-1,177
Net cash (used in) provided by investing activities	-1,857	12,434
Cash flows from financing activities:	'	'
Deferred financing costs	-19	'
Proceeds from initial public offering, net of issuance costs	55,046	-1,702
Proceeds from issuance of preferred stock, net of issuance costs	18,167	34,097
Proceeds from exercise of stock options	1	109
Proceeds from early exercise of stock options	'	253
Net cash provided by financing activities	73,195	32,757
Effect of exchange rate changes on cash and cash equivalents	-1	3
Net change in cash and cash equivalents	40,905	26,681
Cash and cash equivalents, beginning of period	38,186	4,477
Cash and cash equivalents, end of period	79,091	31,158
Supplemental disclosure of noncash investing and financing activities:	'	'
Purchase of property and equipment included in liabilities	6	155
Deferred financing costs included in liabilities	410	648
Leasehold improvements paid for by landlord	'	478
Conversion of preferred stock to common stock	110,796	'
Release of stock option early exercise repurchase liability	78	'
Valuation of future purchase rights upon issuance	'	894
Beneficial conversion underlying the senior preferred stock	'	673
Accretion to redemption value of redeemable convertible preferred stock	$4,410	$4,132

Description_of_Business_and_Ba

Description of Business and Basis of Financial Statements	9 Months Ended
	Sep. 30, 2014
Accounting Policies [Abstract]	'
Description of Business and Basis of Financial Statements	'
	1. Description of Business and Basis of Financial Statements
	Description of Business
	We began operations as a California corporation on May 23, 2003 through the acquisition of the assets and business of VitaGen, Inc. and in June 2003 changed our name to Vital Therapies, Inc. In January 2004, we were re-incorporated in Delaware. We are a biotherapeutic company focused on developing a cell-based therapy targeting the treatment of acute liver failure. Our product candidate, currently in Phase 3 clinical trials, the ELAD® System or ELAD, is an extracorporeal human cell-based bio-artificial liver therapy designed to allow the patient’s own liver to regenerate to a healthy state, or to stabilize the patient until transplant. Since inception, we have devoted essentially all of our efforts to product development, clinical testing and pilot manufacturing and have not realized revenues from our planned principal operations. Our business, operating results, financial condition, and growth prospects are subject to significant risks and uncertainties, including failing to obtain regulatory approval to commercialize and failing to secure additional funding to complete development of and to commercialize our product. Our headquarters are located in San Diego, California.
	Unaudited Interim Financial Information
	The results for the three and nine months ended September 30, 2014 are not necessarily indicative of results to be expected for the year ending December 31, 2014, any other interim or any future year or period. These unaudited condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto for the year ended December 31, 2013, included in our final prospectus filed with the Securities and Exchange Commission, or the SEC, on April 17, 2014 relating to our Registration Statement on Form S-1 (File No. 333-191711) for our initial public offering, or IPO, and our final prospectus filed with the SEC on October 3, 2014, relating to our Registration Statement on Form S-1 (File No. 333-198863) for our follow-on public offering.
	Basis of Presentation and Consolidation
	The accompanying unaudited interim condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles, or GAAP, and the rules and regulations of the SEC related to a quarterly report on Form 10-Q. Certain information and note disclosures normally included in annual financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to those rules and regulations. The condensed consolidated balance sheet as of December 31, 2013 included in this report has been derived from the audited consolidated financial statements included in our final prospectus relating to our follow-on public offering. The unaudited interim condensed consolidated financial statements have been prepared on the same basis as the annual audited consolidated financial statements and, in the opinion of management, reflect all adjustments that are necessary for a fair statement of the financial position, results of operations and cash flows for the periods presented. All such adjustments are of a normal and recurring nature.
	The unaudited interim condensed consolidated financial statements include the accounts of Vital Therapies, Inc. and its wholly-owned subsidiaries located in the United Kingdom (currently inactive) and China. All intercompany accounts and transactions have been eliminated in consolidation. We manage our operations as a single segment for the purposes of assessing performance and making operating decisions.
	We previously were classified as a “development stage entity” under GAAP and, as such, were required to present inception-to-date information in our statements of operations, comprehensive loss, stockholders’ equity, and cash flows. In June 2014, the Financial Accounting Standards Board, or FASB, issued an accounting standards update that eliminates the concept of a development stage entity from GAAP and removes the related incremental reporting requirements, which we elected to early adopt. See Note 2 for additional information on this new standard. Accordingly, in contrast to our financial statements included in our final prospectus filed with the SEC for our IPO and our Quarterly Report on Form 10-Q for the quarterly period ended March 31, 2014, the condensed consolidated financial statements contained in this report do not include inception-to-date information.

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 preparation of financial statements in conformity with GAAP requires us to make certain estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Actual results could differ materially from those estimates and assumptions.
	Cash and Cash Equivalents
	Cash and cash equivalents consist of cash and highly-liquid investments with original maturities of three months or less when acquired and are stated at cost, which approximates market value.
	Restricted Cash
	Restricted cash relates to amounts reserved for various clinical trial obligations and a lease arrangement at September 30, 2014 and December 31, 2013, as well as for certain provisions of the junior preferred stock agreement at December 31, 2013.
	Fair Value of Financial Instruments
	Fair value is defined as the price that would be received to sell an asset or be paid to transfer a liability in an orderly transaction between market participants on the measurement date. Accounting guidance establishes a 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. The standard describes three levels of inputs that may be used to measure fair value:
	Level 1—Quoted prices in active markets for identical assets or liabilities. Our Level 1 assets consisted of money market funds for the periods presented. We had no Level 1 liabilities for any period presented.
	Level 2—Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities, quoted prices in markets with insufficient volume or infrequent transactions (less active markets), or model-derived valuations in which all significant inputs are observable or can be derived principally from or corroborated with observable market data for substantially the full term of the assets or liabilities. We had no Level 2 assets or liabilities for any period presented.
	Level 3—Unobservable inputs to the valuation methodology that are significant to the measurement of the fair value of assets or liabilities. Our Level 3 liabilities consisted of future purchase rights liabilities until the completion of our IPO in April 2014, when the future purchase rights liabilities terminated. See “Future Purchase Rights Liabilities” below. We had no Level 3 assets in any period presented.
	The carrying value of cash and cash equivalents, restricted cash, other current assets and prepaid expenses, accounts payable, and accrued expenses approximate fair value due to the short period of time to maturity.
	Deferred Financing Costs
	Deferred financing costs represent direct costs associated with the issuance of our corporate securities. Direct costs include, but are not limited to, the legal, accounting and printing costs. Indirect costs associated with the future issuance of corporate securities are expensed as incurred. Deferred financing costs as of December 31, 2013 were offset against the proceeds from our IPO in April 2014. Deferred financing costs as of September 30, 2014 represent direct costs associated with a follow-on public offering of our common stock, which was completed in October 2014 (see Note 9).
	Property and Equipment, Depreciation and Amortization
	Property and equipment are recorded at cost and depreciated using the straight-line method over the estimated useful lives of the assets (generally three to five years). Leasehold improvements are stated at cost and amortized on a straight-line basis over the lesser of the remaining term of the related lease or the estimated useful lives of the assets. Construction in progress is not depreciated until the underlying asset is available to be placed in service. Repairs and maintenance costs are charged to expense as incurred.
	Impairment of Long-lived Assets
	Long-lived assets consist primarily of property and equipment. An impairment loss is recorded if and when events and circumstances indicate that assets might be impaired and the undiscounted cash flows estimated to be generated by those assets are less than the carrying amount of those assets. We have not recognized any impairment losses through September 30, 2014.
	Convertible and Redeemable Convertible Preferred Stock
	Our junior convertible and senior redeemable convertible preferred stock were classified as mezzanine equity instead of a component of stockholders’ deficit in accordance with authoritative guidance for the classification and measurement of potentially redeemable securities, as the preferred stock was conditionally redeemable at the holder’s option or upon certain change in control events that are outside our control, including liquidation, sale, or transfer of control of the company. In conjunction with our IPO in April 2014, all shares of our junior convertible and senior redeemable convertible preferred stock were converted to common stock.
	Future Purchase Rights Liabilities
	Our future purchase rights liabilities were initially recorded at their estimated fair value on the date of issuance as a discount on the underlying preferred stock and were re-measured to reflect changes in the estimated fair value at each reporting date, with any decrease or increase in the estimated fair value being recorded as other income or expense, respectively. The fair value of these liabilities was estimated using a binomial lattice model that was based on the characteristics of the common and preferred stock on the valuation date, probabilities related to our operations and clinical development, as well as assumptions for volatility, remaining expected life, risk-free interest rate and, in some cases, credit spread. Changes in the fair value of the future purchase rights fluctuated in conjunction with increases or decreases in the implied fair value of our common stock, and the number of preferred and common shares and future purchase rights outstanding relative to our enterprise value at each reporting date. In April 2014, the remaining future purchase rights terminated upon the conversion of all senior preferred stock to common stock in conjunction with our IPO with the remaining balance of the future purchase rights liabilities recorded as other income in our statement of operations for the applicable period.
	Research and Development
	Research and development costs consist primarily of employee-related expenses, costs incurred for clinical trial sites, contractors and contract research organizations engaged in the development of the ELAD System, expenses associated with obtaining regulatory approvals, and the cost of acquiring and manufacturing clinical trial materials. All research and development costs are expensed as incurred.
	Stock-based Compensation
	We measure and recognize compensation expense for all stock-based payments made to employees and directors based on estimated fair value, net of an estimated forfeiture rate, and to consultants based on estimated fair value. Currently, our stock-based awards consist only of stock options; however, future grants under our equity compensation plans may consist of shares of restricted stock and restricted stock units. We estimate the fair value of stock options granted using the Black-Scholes-Merton, or BSM, option pricing model, which requires the use of estimates to value employee stock-based compensation at the date of grant.
	We recognize stock-based compensation cost for employees and directors on a straight-line basis over the requisite service period of the award. Stock-based compensation expense is recognized only for those awards that are ultimately expected to vest. We estimate forfeitures based on an analysis of our expected employee turnover and will continue to evaluate the appropriateness of the forfeiture rate based on actual forfeiture experience, analysis of employee turnover and other factors. We will revise the forfeiture estimate, if necessary, in subsequent periods if actual forfeitures differ from those estimates. Changes in forfeiture estimates, which have not been material to date, impact compensation cost in the period in which the change in estimate occurs.
	The fair value of options granted to consultants is estimated using the BSM option pricing model and is re-measured at each reporting date with changes in fair value recognized as expense in the consolidated statements of operations.
	The BSM option pricing model requires the input of highly subjective assumptions, including the risk-free interest rate, the expected dividend yield of our common stock, the expected volatility of the price of our common stock, and the expected term of the option. These estimates involve inherent uncertainties and the application of management’s judgment. If factors change and different assumptions are used, our stock-based compensation expense could be materially different in the future. These assumptions are estimated as follows:
	Risk-free Interest Rate
	We base the risk-free interest rate assumption on zero-coupon U.S. treasury instruments appropriate for the expected term of the stock option grants.
	Expected Dividend Yield
	We base the expected dividend yield assumption on the fact that we have never paid cash dividends and have no present intention to pay cash dividends. Consequently, we used an expected dividend yield of zero.
	Expected Volatility
	The expected stock price volatility for our common stock is estimated based on volatilities of a peer group of similar companies by taking the average historic price volatility for these peers for a period equivalent to the expected term of the stock option grants. The peer group was developed based on companies in the biotechnology industry whose shares are publicly-traded. We do not use our average historic price volatility as we have only been a publicly-traded company since April 2014.
	Expected Term
	The expected term represents the period of time that options are expected to be outstanding. As we do not have sufficient historical experience for determining the expected term of the stock option awards granted we determined the expected life assumption using either the simplified method, which is an average of the contractual term of the option and its ordinary vesting period, or the comparable average expected term utilizing those companies in the peer group noted above, as applicable.
	Common Stock Valuation
	Due to the absence of a public market trading our common stock prior to the completion of our IPO in April 2014, it was necessary to estimate the fair value of the common stock underlying our stock-based awards when performing fair value calculations using the BSM option pricing model. The fair value of the common stock underlying our stock-based awards was assessed by our board of directors. All options to purchase shares of our common stock have been granted with an exercise price per share no less than the estimated fair value per share of our common stock underlying those options on the date of grant.
	In the absence of a public trading market for our common stock, we determined the estimated fair value of our common stock using methodologies, approaches, and assumptions consistent with the American Institute of Certified Public Accountants, or AICPA, Audit and Accounting Practice Aid Series: Valuation of Privately Held Company Equity Securities Issued as Compensation, or the AICPA Practice Aid.
	Leases
	We lease all of our office space and enter into various other operating lease agreements in conducting our business. At the inception of each lease, we evaluate the lease agreement to determine whether the lease is an operating or capital lease. Some of our lease agreements may contain renewal options, tenant improvement allowances, rent holidays or rent escalation clauses. When such items are included in a lease agreement, we record a deferred rent asset or liability equal to the difference between the rent expense and future minimum lease payments due. The rent expense related to operating leases is recognized on a straight-line basis in the statements of operations over the terms of the leases. In cases where our lessor grants to us leasehold improvement allowances that reduce our rent expense, we capitalize the improvements as incurred and recognize deferred rent, which is amortized over the shorter of the lease term or the expected useful life of the improvements.
	Comprehensive Loss
	Comprehensive loss is defined as the change in equity during a period from transactions and other events and circumstances from non-owner sources and has been reflected as a separate component of stockholders’ equity (deficit) in the accompanying condensed consolidated balance sheets.
	Foreign Currency Translation and Transactions
	The functional currencies of our subsidiaries in the United Kingdom and China are the local currencies. Assets and liabilities of the subsidiaries are translated at the rate of exchange at the balance sheet date. Expenses are translated at the average rate of exchange rates in effect during the reporting period. Gains and losses resulting from foreign currency translation are included in accumulated other comprehensive income in the accompanying condensed consolidated balance sheets. Gains and losses resulting from foreign currency transactions are included in the results of operations, which to date, have not been significant.
	Income Taxes
	We account 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 consolidated 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.
	We recognize net deferred tax assets to the extent we believe 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 we would be able to realize our 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. As of September 30, 2014 and December 31, 2013, we maintained a full valuation allowance against our entire balance of deferred tax assets.
	We record uncertain tax positions in accordance with Accounting Standards Codification, or ASC, 740 on the basis of a two-step process whereby (1) management determines whether it is more likely than not that the tax positions will be sustained on the basis of the technical merits of the position and (2) for those tax positions that meet the more-likely-than-not recognition threshold, management recognizes the largest amount of tax benefit that is more than 50 percent likely to be realized upon ultimate settlement with the related tax authority. We recognize interest and penalties related to unrecognized tax benefits, if any, within income tax expense and any accrued interest and penalties are included within the related tax liability line.
	Net Loss Per Share
	Basic net loss per share attributable to common stockholders is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of common shares outstanding for the period, without consideration for common stock equivalents. Excluded from the weighted-average number of shares outstanding are shares that have been issued upon the early exercise of stock options and are subject to future vesting, which was a total of 29,622 and 50,336 shares as of September 30, 2014 and 2013, respectively. Diluted net loss per share attributable to common stockholders is computed by dividing the net loss attributable to common stockholders by the weighted-average number of common share equivalents outstanding for the period determined using the treasury-stock method. Common stock equivalents are comprised of convertible and redeemable convertible preferred stock, warrants for the purchase of common stock, and options outstanding under our stock option plan. For all periods presented, there is no difference in the number of shares used to calculate basic and diluted shares outstanding due to our net loss position.
	Potentially dilutive securities, which are not included in the calculation of diluted net loss per share attributable to common stockholders because to do so would be anti-dilutive, are as follows (in common stock equivalent shares):
		As of September 30,
		2014		2013
	Convertible preferred stock		—		11,313,370
	Options to purchase common stock		3,263,733		2,982,730
	Warrants to purchase common stock		250,646		250,646
	Recently Issued Accounting Standards
	In August 2014, the FASB issued Accounting Standards Update, or ASU, No. 2014-15, “Presentation of Financial Statements—Going Concern (Subtopic 205-40): Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern,” or ASU 2014-15. ASU 2014-15 will require management to assess, at each annual and interim reporting period, the entity’s ability to continue as a going concern. The amendments in ASU 2014-15 do not have any application to an entity’s financial statements, but only to disclosure in the related notes. ASU 2014-15 is effective for annual periods ending after December 15, 2016 and early application is permitted. We intend to apply ASU 2014-15 beginning with the first quarter of fiscal year 2016.
	In June 2014, the FASB issued ASU No. 2014-10, “Development Stage Entities (Topic 915)—Elimination of Certain Financial Reporting Requirements, Including an Amendment to Variable Interest Entities Guidance in Topic 810, Consolidation,” or ASU 2014-10, which eliminates the concept of a development stage entity in its entirety from current accounting guidance and provides for certain amendments to the consolidation guidance in ASC Topic 810. Prior to the issuance of this guidance, we were considered a development stage entity and as a result we included certain inception-to-date disclosures in our financial statements. The guidance related to the elimination of the concept of a development stage entity is effective for public companies for annual reporting periods beginning after December 15, 2014, and interim periods therein. The amendment of the consolidation guidance in Topic 810 is effective for public companies for annual reporting periods beginning after December 15, 2015. Early adoption of the new standard is permitted. We adopted ASU No. 2014-10 during the quarter ended June 30, 2014. As such, all inception-to-date disclosures have been removed from these condensed consolidated financial statements.

Other_Financial_Information

Other Financial Information	9 Months Ended
	Sep. 30, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]	'
Other Financial Information	'
	3. Other Financial Information
	Property and Equipment
	Property and equipment, leasehold improvements, and related accumulated depreciation and amortization were as follows (in thousands):
		September 30,			December 31,
		2014			2013
	Manufacturing and laboratory equipment	$	3,991		$	3,229
	Office furniture and equipment		113			112
	Clinical equipment		2,129			1,606
	Computer equipment and software		150			122
	Leasehold improvements		3,210			2,830
	Construction in progress		—			323
			9,593			8,222
	Less: accumulated depreciation and amortization		(6,608	)		(5,755	)
	Total	$	2,985		$	2,467
	Depreciation and amortization expense was $310,000 and $256,000 for the three months ended September 30, 2014 and 2013, respectively, and $853,000 and $593,000, for the nine months ended September 30, 2014 and 2013, respectively.
	Accrued Expenses
	Accrued expenses consist of (in thousands):
		September 30,			December 31,
		2014			2013
	Accrued clinical and related costs	$	5,216		$	2,067
	Accrued compensation and related taxes		1,684			512
	Accrued financing costs		408			496
	Accrued other		222			178
	Total	$	7,530		$	3,253

Commitments_and_Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2014
Commitments and Contingencies Disclosure [Abstract]	'
Commitments and Contingencies	'
	4. Commitments and Contingencies
	Operating Leases
	We lease office, manufacturing and research and development facilities, and equipment under various non-cancellable operating lease agreements through 2017. Facility leases generally provide for periodic rent increases and many contain escalation clauses and renewal options. Certain leases require us to pay property taxes and routine maintenance. Total rent expense under our operating leases was $203,000 and $169,000 for the three months ended September 30, 2014 and 2013, respectively, and $596,000 and $457,000 for the nine months ended September 30, 2014 and 2013, respectively.
	We recognize rent expense for our facility operating leases on a straight-line basis. We account for the difference between the minimum lease payments and the straight-line expense as deferred rent. Current and long-term deferred rent totaled $123,000 and $283,000 at September 30, 2014, and $142,000 and $321,000 at December 31, 2013, respectively.
	Legal Proceedings
	We are not currently a party to any litigation, nor are we aware of any pending or threatened litigation against us that we believe would materially affect our business, operating results, financial condition or cash flows. Our industry is characterized by frequent claims and litigation, including claims regarding patent and other intellectual property rights, as well as for product liability. As a result, in the future, we may be involved in various legal proceedings from time to time.

Fair_Value

Fair Value	9 Months Ended
	Sep. 30, 2014
Fair Value Disclosures [Abstract]	'
Fair Value	'
	5. Fair Value
	The following fair value hierarchy table presents information about each major category of our financial assets and liabilities measured at fair value on a recurring basis (in thousands):
		Fair Value Measurement at September 30, 2014
		Fair Value			Level 1		Level 2		Level 3
	Assets
	Cash equivalents:
	Money market funds	$	76,222		$	76,222	$	—	$	—
		Fair Value Measurement at December 31, 2013
		Fair Value			Level 1		Level 2		Level 3
	Assets
	Cash equivalents:
	Money market funds	$	37,158		$	37,158	$	—	$	—
	Liabilities
	Future purchase rights	$	2,600		$	—	$	—	$	2,600
	We report the change in fair value during each period as a nonoperating gain or loss. There were no transfers between Level 1, Level 2 or Level 3 for our assets or liabilities during the nine months ended September 30, 2014.
	The following table summarizes the changes in Level 3 future purchase rights liabilities measured at fair value on a recurring basis for the nine months ended September 30, 2014 (in thousands):
		Fair Value of
		Future Purchase
		Rights Liabilities
	Balance at January 1, 2014	$	2,600
	Re-measurement of future purchase rights		(2,600	)
	Balance at September 30, 2014	$	—
	We valued the future purchase rights liabilities as of December 31, 2013, using a binomial lattice option pricing model with the following assumptions:
		December 31,
		2013
	Common stock fair value	$	5.93
	Preferred stock price	$	8
	Volatility		85	%
	Risk-free interest rate		0.38	%
	Contractual life (years)		2.08
	Number of nodes		25
	Dividend yield		0	%

Convertible_and_Redeemable_Con

Convertible and Redeemable Convertible Preferred Stock	9 Months Ended
	Sep. 30, 2014
Equity [Abstract]	'
Convertible and Redeemable Convertible Preferred Stock	'
	6. Convertible and Redeemable Convertible Preferred Stock
	Junior Convertible Preferred Stock
	In February 2012, we entered into a securities purchase agreement for the sale of junior convertible preferred stock. The junior preferred stock financing totaled $1.5 million of convertible, but not redeemable, preferred stock at approximately $0.43 a share, for an aggregate of 3,501,400 shares, for which we received net proceeds of $1.3 million. In conjunction with the completion of our IPO in April 2014, all shares of our junior convertible preferred stock were converted into common stock on a one-to-one basis and the remaining unamortized issuance costs of $31,000 were recognized as accretion to the redemption value of the convertible preferred stock in the statements of operations.
	Senior Redeemable Convertible Preferred Stock
	In September 2012, we entered into a senior preferred stock purchase agreement (as amended in December 2013, the Senior Preferred Purchase Agreement) that authorized the multi-stage issuance of shares of our senior redeemable convertible preferred stock for $8.00 per share. As of December 31, 2013, we had issued 10,212,007 shares of senior redeemable convertible preferred stock under the Senior Preferred Purchase Agreement.
	Pursuant to the Senior Preferred Purchase Agreement, in January 2014 we sold an additional 555,000 shares of senior redeemable convertible preferred stock for proceeds of $4.3 million, net of issuance costs of $135,000. Also in January 2014, we completed the sale of 1.5 million shares of our senior redeemable convertible preferred stock at a price of $8.00 per share in a private placement to new investors for proceeds of $12.0 million, net of issuance costs of $31,000.
	In February 2014, we completed a pre-emptive rights offering, triggered by the private placement to new investors in January 2014, for 241,016 shares of our senior redeemable convertible preferred stock at a price of $8.00 per share for proceeds of $1.9 million, net of issuance costs of $35,000.
	In conjunction with the completion of our IPO on April 2014, all the outstanding shares of our senior redeemable convertible preferred stock were converted into common stock on a one-to-one basis and the remaining unamortized discounts of $3.8 million and issuance costs of $727,000 were recognized as a deemed dividend and accretion to redemption value of the redeemable convertible preferred stock, respectively, in the statement of operations.
	Future Purchase Rights/Beneficial Conversion Amounts
	Pursuant to the Senior Preferred Purchase Agreement, we granted the investors in the senior preferred stock financing the right, subject to the satisfaction of certain conditions, to purchase additional shares of senior redeemable convertible preferred stock for a purchase price of $8.00 per share at multiple subsequent closings in accordance with a schedule provided in the Senior Preferred Purchase Agreement. These future purchase rights were legally detachable from the underlying senior preferred stock and, as a result, were considered freestanding instruments accounted for separately from the senior preferred stock as a liability.
	In addition, as the fair value received for certain shares of senior preferred stock sold during the year ended December 31, 2013 was less than the fair of our common stock on the date of issuance, we recorded beneficial conversion amounts associated with the rights of the holders of such preferred stock to convert their preferred stock to common stock. These beneficial conversion amounts were recorded as an offset to additional paid-in capital and were being amortized as a deemed dividend over the redemption period using an effective interest rate method.
	All remaining future purchase rights associated with our preferred stock were terminated and the remaining unamortized beneficial conversion balance of $878,000 was recognized as a reduction to equity at the effective date of our IPO. We recognized no deemed dividend for the three months ended September 30, 2014, and $4.7 million for the nine months ended September 30, 2014, and $10,000 and $21,000 for the three and nine month periods ended September 30, 2013, respectively.
	Warrants
	Warrants outstanding and exercisable for 250,646 shares of common stock as of December 31, 2013 and September 30, 2014 have a weighted-average exercise price of $95.21 and expire between February 2016 and September 2019.

Common_Stock

Common Stock	9 Months Ended
	Sep. 30, 2014
Equity [Abstract]	'
Common Stock	'
	7. Common Stock
	In April 2014, we completed an IPO selling 4,500,000 shares of our common stock at $12.00 per share and received net proceeds of $50.2 million after underwriters’ discounts and commissions. In addition, we incurred $5.8 million in offering expenses, resulting in total costs of $9.6 million and net offering proceeds to us of $44.4 million. In May 2014, the underwriters exercised their option to purchase an additional 675,000 shares of our common stock at $12.00 per share in full. As a result, we received an additional $7.5 million in net proceeds after underwriters’ discounts and commissions of $567,000 for total net proceeds of $51.9 million from the IPO.
	In connection with our IPO, we filed an amended and restated certificate of incorporation to authorize 150,000,000 shares of capital stock, consisting of 20,000,000 shares of preferred stock and 130,000,000 shares of common stock.
	Stock Reserved for Future Issuance
	Shares reserved for future issuance at September 30, 2014 are as follows:
		Number of
		Shares
	Common stock warrants		250,646
	Common stock options outstanding		3,263,733
	Common stock options available for future grant		462,685
	Total common shares reserved for future issuance		3,977,064

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
	Equity Incentive Plans
	Our 2012 Stock Option Plan, or the 2012 Plan, provided for the grant of stock options, restricted stock, restricted stock units, stock purchase rights, and performance awards to employees, directors, and consultants. Option grants under the 2012 Plan generally have a ten-year term, vest over four years and are exercisable immediately, subject to a repurchase right that lapses as the option vests. Options to purchase 55,516 shares of our common stock had been exercised prior to vesting under the 2012 Plan, of which 29,622 shares were unvested and subject to repurchase as of September 30, 2014. We have not repurchased any shares related to these early exercises for which our repurchase liability was $149,000 as of September 30, 2014.
	Our 2014 Equity Incentive Plan, or the 2014 Plan, became effective on the close of the IPO and replaces the 2012 Plan with respect to future awards. The 2014 Plan provides for the grant of stock options, restricted stock, restricted stock units, stock appreciation rights, performance awards and performance units to employees, directors, and consultants. Option grants under the 2014 Plan generally have a ten-year term and vest over four years. Shares available for grant under the 2014 Plan include any shares remaining available or becoming available in the future under the 2012 Plan due to cancellation or forfeiture. In addition, the 2014 Plan provides for annual increases in the number of shares available for issuance thereunder beginning upon the effective date of our IPO, and on each annual anniversary of the effective date of the IPO, equal to the lower of:
		•		1,200,000 shares of our common stock;
		•		3% of the outstanding shares of our common stock on the second-to-the-last day prior to each anniversary date of the effectiveness of our IPO; or
		•		an amount as our board of directors may determine.
	As of September 30, 2014, the aggregate number of shares that may be issued under the 2012 and 2014 Plans is 3,726,418.
	The following table summarizes employee and nonemployee stock option activity:
			Options			Weighted-		Weighted-		Aggregate
						Average		Average		Intrinsic
						Exercise		Remaining		Value
						Price		Contractual
								Term (Years)
	Outstanding as of January 1, 2014			3,098,573		$	6.71
	Granted			211,245		$	15.89
	Exercised			(119	)	$	12.49
	Forfeited			(45,966	)	$	8.46
	Outstanding as of September 30, 2014			3,263,733		$	7.08		8.19	$	43,796,123
	Options vested and expected to vest as of September 30, 2014			3,258,131		$	7.08		8.19	$	43,722,647
	Options exercisable as of September 30, 2014			3,131,179		$	6.55		8.13	$	43,421,753
	Stock-based Compensation Expense
	The weighted-average grant date fair value of stock options granted during the nine months ended September 30, 2014 and 2013 was $11.08 and $5.67, respectively. The following are the ranges of underlying assumptions used in the BSM option pricing model to determine the fair value of stock options granted to employees and nonemployees:
			Nine Months Ended September 30,
			2014		2013
	Employees:
	Risk-free interest rate		1.60% - 1.88%		0.76% - 0.91%
	Expected dividend yield		0%		0%
	Expected volatility		81% - 85%		100%
	Expected term of options (years)		6		5
	Fair value of common stock		$7.55 - $24.04		$6.82 - $9.94
	Nonemployees:
	Risk-free interest rate		0.11% - 1.20%		0.15% - 0.67%
	Expected dividend yield		0%		0%
	Expected volatility		73% - 85%		100%
	Expected term of options (years)		4-Jan		4-Jan
	Fair value of common stock		$11.31 - $27.24		$6.82 - $9.94
	Valuation Analyses
	Due to our management’s and board of directors’ decision to pursue an IPO, coupled with our belief that we could reasonably estimate the form and timing of potential liquidity events, we utilized a Probability Weighted Expected Return Method, or PWERM, to determine the fair value of our common stock in 2013 and 2014 prior to the completion of our IPO in April 2014. Under this method, the implied fair value of our common stock is estimated based upon an analysis of future values assuming various outcomes. The value is based on the probability-weighted present value of expected future investment returns considering each of the possible outcomes available to us as well as the rights of each share class. The possible outcomes considered are based upon an analysis of future scenarios as described below:
		•		closing of an IPO;
		•		sale to a strategic acquirer;
		•		continuation as a private company with subsequent liquidation event; and
		•		dissolution.
	Critical assumptions required to perform the PWERM include the following:
		•		Scenarios: Expected future events were identified.
		•		Scenario probabilities: Estimates of the probability of occurrence of each event were identified.
		•		Valuation: Expected future values under each scenario were estimated.
		•		Timing: Expected timing to the event under each scenario were estimated.
		•		Risk adjusted discount rates: Risk-adjusted discount rates were selected for each equity class based on the rights and preferences of each equity class and market data.
		•		Discounts: Appropriate minority or marketability discounts, if any, required to estimate the per share value of the various equity classes were determined.
	In determining the implied fair value of our common stock in the IPO scenario, we assumed that the preferred stock then outstanding would be converted into common stock. In allocating value to our common stock in the merger or sale scenario, we first allocated to our outstanding shares of preferred stock the greater of the liquidation preference of the preferred stock and the amount that would have been payable had all such shares of preferred stock been converted to common stock.
	There is inherent uncertainty in these estimates and, if we had made different assumptions, the implied fair value of the underlying common stock and amount of our stock-based compensation expense, net loss and net loss per share amounts would have differed.
	February 12, 2014 Valuation Analysis
	Our analysis considered the following probability-weighted scenarios:
	Scenario		Weight
	IPO by May 15, 2014			25	%
	Sale by September 30, 2015			10	%
	Private company			50	%
	Dissolution			15	%
	A discount for lack of marketability was applied for common stockholders of 8%, 20% and 28% for the IPO, sale and private company scenarios, respectively, which resulted in an implied fair value of $7.55 per share. The increase in fair value of our common stock from December 31, 2013 of $5.93 per share was primarily related to the increase in likelihood of an IPO scenario based on progress toward a public offering, coupled with a slight decrease in discount for lack of marketability for the IPO and sale scenarios. These were partially offset by dilution from the issuance of additional shares of our senior redeemable convertible preferred stock in January 2014.
	March 31, 2014 Valuation Analysis
	Our analysis considered the following probability-weighted scenarios:
	Scenario		Weight
IPO by April 15, 2014			65	%
Sale by September 30, 2015			10	%
Private company			15	%
Dissolution			10	%
A discount for lack of marketability was applied for common stockholders of 2%, 17% and 27% for the IPO, sale and private company scenarios, respectively, which resulted in an implied fair value of $11.30 per share. The increase in fair value of our common stock from December 31, 2013 and February 12, 2014 was related to the increase in likelihood of an IPO scenario as significant progress had been completed toward a public offering and the decrease in discount for lack of marketability for the IPO scenario that reflected the proximity to the projected time to liquidity. These were slightly offset by dilution from the issuance of additional shares of our senior redeemable convertible preferred stock in January and February 2014, as applicable.
Total stock-based compensation expense for employee and nonemployee stock awards to employees and nonemployees recognized in our condensed consolidated statements of operations is as follows (in thousands):
		Three Months Ended					Nine Months Ended
		September 30,					September 30,
		2014			2013		2014		2013
Employees:
Research and development		$	194		$	84	$	517	$	141
General and administrative			238			134		642		300
Total		$	432		$	218	$	1,159	$	441
Nonemployees:
Research and development		$	211		$	51	$	572	$	122
General and administrative			14			22		34		28
Total		$	225		$	73	$	606	$	150
As of September 30, 2014, there was $5.5 million of total compensation cost related to unvested stock option awards not yet recognized, which is expected to be recognized over a remaining weighted-average vesting period of 2.3 years.

Subsequent_Event

Subsequent Event	9 Months Ended
	Sep. 30, 2014
Subsequent Events [Abstract]	'
Subsequent Event	'
	9. Subsequent Event
	In October 2014, we completed a follow-on public offering selling 2,000,000 shares of our common stock at $17.50 per share and received net proceeds of $32.6 million after underwriters’ discounts and commissions. In addition, we incurred $540,000 in estimated offering expenses, resulting in total estimated costs of $3.0 million and net estimated offering proceeds to us of approximately $32.0 million. In November 2014, the underwriters exercised a portion of their option and purchased an additional 50,000 shares of our common stock at $17.50 per share. As a result, we received an additional $0.8 million in net proceeds after underwriters’ discounts and commissions, for total net proceeds from the follow-on public offering of $32.8 million, net of discounts, commissions and estimated costs, from the offering.

Description_of_Business_and_Ba1

Description of Business and Basis of Financial Statements (Policies)	9 Months Ended
	Sep. 30, 2014
Accounting Policies [Abstract]	'
Unaudited Interim Financial Information	'
	Unaudited Interim Financial Information
	The results for the three and nine months ended September 30, 2014 are not necessarily indicative of results to be expected for the year ending December 31, 2014, any other interim or any future year or period. These unaudited condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto for the year ended December 31, 2013, included in our final prospectus filed with the Securities and Exchange Commission, or the SEC, on April 17, 2014 relating to our Registration Statement on Form S-1 (File No. 333-191711) for our initial public offering, or IPO, and our final prospectus filed with the SEC on October 3, 2014, relating to our Registration Statement on Form S-1 (File No. 333-198863) for our follow-on public offering.
Basis of Presentation and Consolidation	'
	Basis of Presentation and Consolidation
	The accompanying unaudited interim condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles, or GAAP, and the rules and regulations of the SEC related to a quarterly report on Form 10-Q. Certain information and note disclosures normally included in annual financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to those rules and regulations. The condensed consolidated balance sheet as of December 31, 2013 included in this report has been derived from the audited consolidated financial statements included in our final prospectus relating to our follow-on public offering. The unaudited interim condensed consolidated financial statements have been prepared on the same basis as the annual audited consolidated financial statements and, in the opinion of management, reflect all adjustments that are necessary for a fair statement of the financial position, results of operations and cash flows for the periods presented. All such adjustments are of a normal and recurring nature.
	The unaudited interim condensed consolidated financial statements include the accounts of Vital Therapies, Inc. and its wholly-owned subsidiaries located in the United Kingdom (currently inactive) and China. All intercompany accounts and transactions have been eliminated in consolidation. We manage our operations as a single segment for the purposes of assessing performance and making operating decisions.
	We previously were classified as a “development stage entity” under GAAP and, as such, were required to present inception-to-date information in our statements of operations, comprehensive loss, stockholders’ equity, and cash flows. In June 2014, the Financial Accounting Standards Board, or FASB, issued an accounting standards update that eliminates the concept of a development stage entity from GAAP and removes the related incremental reporting requirements, which we elected to early adopt. See Note 2 for additional information on this new standard. Accordingly, in contrast to our financial statements included in our final prospectus filed with the SEC for our IPO and our Quarterly Report on Form 10-Q for the quarterly period ended March 31, 2014, the condensed consolidated financial statements contained in this report do not include inception-to-date information.
Use of Estimates	'
	Use of Estimates
	The preparation of financial statements in conformity with GAAP requires us to make certain estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Actual results could differ materially from those estimates and assumptions.
Cash and Cash Equivalents	'
	Cash and Cash Equivalents
	Cash and cash equivalents consist of cash and highly-liquid investments with original maturities of three months or less when acquired and are stated at cost, which approximates market value.
Restricted Cash	'
	Restricted Cash
	Restricted cash relates to amounts reserved for various clinical trial obligations and a lease arrangement at September 30, 2014 and December 31, 2013, as well as for certain provisions of the junior preferred stock agreement at December 31, 2013.
Fair Value of Financial Instruments	'
	Fair Value of Financial Instruments
	Fair value is defined as the price that would be received to sell an asset or be paid to transfer a liability in an orderly transaction between market participants on the measurement date. Accounting guidance establishes a 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. The standard describes three levels of inputs that may be used to measure fair value:
	Level 1—Quoted prices in active markets for identical assets or liabilities. Our Level 1 assets consisted of money market funds for the periods presented. We had no Level 1 liabilities for any period presented.
	Level 2—Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities, quoted prices in markets with insufficient volume or infrequent transactions (less active markets), or model-derived valuations in which all significant inputs are observable or can be derived principally from or corroborated with observable market data for substantially the full term of the assets or liabilities. We had no Level 2 assets or liabilities for any period presented.
	Level 3—Unobservable inputs to the valuation methodology that are significant to the measurement of the fair value of assets or liabilities. Our Level 3 liabilities consisted of future purchase rights liabilities until the completion of our IPO in April 2014, when the future purchase rights liabilities terminated. See “Future Purchase Rights Liabilities” below. We had no Level 3 assets in any period presented.
	The carrying value of cash and cash equivalents, restricted cash, other current assets and prepaid expenses, accounts payable, and accrued expenses approximate fair value due to the short period of time to maturity.
Deferred Financing Costs	'
	Deferred Financing Costs
	Deferred financing costs represent direct costs associated with the issuance of our corporate securities. Direct costs include, but are not limited to, the legal, accounting and printing costs. Indirect costs associated with the future issuance of corporate securities are expensed as incurred. Deferred financing costs as of December 31, 2013 were offset against the proceeds from our IPO in April 2014. Deferred financing costs as of September 30, 2014 represent direct costs associated with a follow-on public offering of our common stock, which was completed in October 2014 (see Note 9).
Property and Equipment, Depreciation and Amortization	'
	Property and Equipment, Depreciation and Amortization
	Property and equipment are recorded at cost and depreciated using the straight-line method over the estimated useful lives of the assets (generally three to five years). Leasehold improvements are stated at cost and amortized on a straight-line basis over the lesser of the remaining term of the related lease or the estimated useful lives of the assets. Construction in progress is not depreciated until the underlying asset is available to be placed in service. Repairs and maintenance costs are charged to expense as incurred.
Impairment of Long-lived Assets	'
	Impairment of Long-lived Assets
	Long-lived assets consist primarily of property and equipment. An impairment loss is recorded if and when events and circumstances indicate that assets might be impaired and the undiscounted cash flows estimated to be generated by those assets are less than the carrying amount of those assets. We have not recognized any impairment losses through September 30, 2014.
Convertible and Redeemable Convertible Preferred Stock	'
	Convertible and Redeemable Convertible Preferred Stock
	Our junior convertible and senior redeemable convertible preferred stock were classified as mezzanine equity instead of a component of stockholders’ deficit in accordance with authoritative guidance for the classification and measurement of potentially redeemable securities, as the preferred stock was conditionally redeemable at the holder’s option or upon certain change in control events that are outside our control, including liquidation, sale, or transfer of control of the company. In conjunction with our IPO in April 2014, all shares of our junior convertible and senior redeemable convertible preferred stock were converted to common stock.
Future Purchase Rights Liabilities	'
	Future Purchase Rights Liabilities
	Our future purchase rights liabilities were initially recorded at their estimated fair value on the date of issuance as a discount on the underlying preferred stock and were re-measured to reflect changes in the estimated fair value at each reporting date, with any decrease or increase in the estimated fair value being recorded as other income or expense, respectively. The fair value of these liabilities was estimated using a binomial lattice model that was based on the characteristics of the common and preferred stock on the valuation date, probabilities related to our operations and clinical development, as well as assumptions for volatility, remaining expected life, risk-free interest rate and, in some cases, credit spread. Changes in the fair value of the future purchase rights fluctuated in conjunction with increases or decreases in the implied fair value of our common stock, and the number of preferred and common shares and future purchase rights outstanding relative to our enterprise value at each reporting date. In April 2014, the remaining future purchase rights terminated upon the conversion of all senior preferred stock to common stock in conjunction with our IPO with the remaining balance of the future purchase rights liabilities recorded as other income in our statement of operations for the applicable period.
Research and Development	'
	Research and Development
	Research and development costs consist primarily of employee-related expenses, costs incurred for clinical trial sites, contractors and contract research organizations engaged in the development of the ELAD System, expenses associated with obtaining regulatory approvals, and the cost of acquiring and manufacturing clinical trial materials. All research and development costs are expensed as incurred.
Stock-based Compensation	'
	Stock-based Compensation
	We measure and recognize compensation expense for all stock-based payments made to employees and directors based on estimated fair value, net of an estimated forfeiture rate, and to consultants based on estimated fair value. Currently, our stock-based awards consist only of stock options; however, future grants under our equity compensation plans may consist of shares of restricted stock and restricted stock units. We estimate the fair value of stock options granted using the Black-Scholes-Merton, or BSM, option pricing model, which requires the use of estimates to value employee stock-based compensation at the date of grant.
	We recognize stock-based compensation cost for employees and directors on a straight-line basis over the requisite service period of the award. Stock-based compensation expense is recognized only for those awards that are ultimately expected to vest. We estimate forfeitures based on an analysis of our expected employee turnover and will continue to evaluate the appropriateness of the forfeiture rate based on actual forfeiture experience, analysis of employee turnover and other factors. We will revise the forfeiture estimate, if necessary, in subsequent periods if actual forfeitures differ from those estimates. Changes in forfeiture estimates, which have not been material to date, impact compensation cost in the period in which the change in estimate occurs.
	The fair value of options granted to consultants is estimated using the BSM option pricing model and is re-measured at each reporting date with changes in fair value recognized as expense in the consolidated statements of operations.
	The BSM option pricing model requires the input of highly subjective assumptions, including the risk-free interest rate, the expected dividend yield of our common stock, the expected volatility of the price of our common stock, and the expected term of the option. These estimates involve inherent uncertainties and the application of management’s judgment. If factors change and different assumptions are used, our stock-based compensation expense could be materially different in the future. These assumptions are estimated as follows:
	Risk-free Interest Rate
	We base the risk-free interest rate assumption on zero-coupon U.S. treasury instruments appropriate for the expected term of the stock option grants.
	Expected Dividend Yield
	We base the expected dividend yield assumption on the fact that we have never paid cash dividends and have no present intention to pay cash dividends. Consequently, we used an expected dividend yield of zero.
	Expected Volatility
	The expected stock price volatility for our common stock is estimated based on volatilities of a peer group of similar companies by taking the average historic price volatility for these peers for a period equivalent to the expected term of the stock option grants. The peer group was developed based on companies in the biotechnology industry whose shares are publicly-traded. We do not use our average historic price volatility as we have only been a publicly-traded company since April 2014.
	Expected Term
	The expected term represents the period of time that options are expected to be outstanding. As we do not have sufficient historical experience for determining the expected term of the stock option awards granted we determined the expected life assumption using either the simplified method, which is an average of the contractual term of the option and its ordinary vesting period, or the comparable average expected term utilizing those companies in the peer group noted above, as applicable.
	Common Stock Valuation
	Due to the absence of a public market trading our common stock prior to the completion of our IPO in April 2014, it was necessary to estimate the fair value of the common stock underlying our stock-based awards when performing fair value calculations using the BSM option pricing model. The fair value of the common stock underlying our stock-based awards was assessed by our board of directors. All options to purchase shares of our common stock have been granted with an exercise price per share no less than the estimated fair value per share of our common stock underlying those options on the date of grant.
	In the absence of a public trading market for our common stock, we determined the estimated fair value of our common stock using methodologies, approaches, and assumptions consistent with the American Institute of Certified Public Accountants, or AICPA, Audit and Accounting Practice Aid Series: Valuation of Privately Held Company Equity Securities Issued as Compensation, or the AICPA Practice Aid.
Leases	'
	Leases
	We lease all of our office space and enter into various other operating lease agreements in conducting our business. At the inception of each lease, we evaluate the lease agreement to determine whether the lease is an operating or capital lease. Some of our lease agreements may contain renewal options, tenant improvement allowances, rent holidays or rent escalation clauses. When such items are included in a lease agreement, we record a deferred rent asset or liability equal to the difference between the rent expense and future minimum lease payments due. The rent expense related to operating leases is recognized on a straight-line basis in the statements of operations over the terms of the leases. In cases where our lessor grants to us leasehold improvement allowances that reduce our rent expense, we capitalize the improvements as incurred and recognize deferred rent, which is amortized over the shorter of the lease term or the expected useful life of the improvements.
Comprehensive Loss	'
	Comprehensive Loss
	Comprehensive loss is defined as the change in equity during a period from transactions and other events and circumstances from non-owner sources and has been reflected as a separate component of stockholders’ equity (deficit) in the accompanying condensed consolidated balance sheets.
Foreign Currency Translation and Transactions	'
	Foreign Currency Translation and Transactions
	The functional currencies of our subsidiaries in the United Kingdom and China are the local currencies. Assets and liabilities of the subsidiaries are translated at the rate of exchange at the balance sheet date. Expenses are translated at the average rate of exchange rates in effect during the reporting period. Gains and losses resulting from foreign currency translation are included in accumulated other comprehensive income in the accompanying condensed consolidated balance sheets. Gains and losses resulting from foreign currency transactions are included in the results of operations, which to date, have not been significant.
Income Taxes	'
	Income Taxes
	We account 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 consolidated 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.
	We recognize net deferred tax assets to the extent we believe 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 we would be able to realize our 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. As of September 30, 2014 and December 31, 2013, we maintained a full valuation allowance against our entire balance of deferred tax assets.
	We record uncertain tax positions in accordance with Accounting Standards Codification, or ASC, 740 on the basis of a two-step process whereby (1) management determines whether it is more likely than not that the tax positions will be sustained on the basis of the technical merits of the position and (2) for those tax positions that meet the more-likely-than-not recognition threshold, management recognizes the largest amount of tax benefit that is more than 50 percent likely to be realized upon ultimate settlement with the related tax authority. We recognize interest and penalties related to unrecognized tax benefits, if any, within income tax expense and any accrued interest and penalties are included within the related tax liability line.
Net Loss Per Share	'
	Net Loss Per Share
	Basic net loss per share attributable to common stockholders is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of common shares outstanding for the period, without consideration for common stock equivalents. Excluded from the weighted-average number of shares outstanding are shares that have been issued upon the early exercise of stock options and are subject to future vesting, which was a total of 29,622 and 50,336 shares as of September 30, 2014 and 2013, respectively. Diluted net loss per share attributable to common stockholders is computed by dividing the net loss attributable to common stockholders by the weighted-average number of common share equivalents outstanding for the period determined using the treasury-stock method. Common stock equivalents are comprised of convertible and redeemable convertible preferred stock, warrants for the purchase of common stock, and options outstanding under our stock option plan. For all periods presented, there is no difference in the number of shares used to calculate basic and diluted shares outstanding due to our net loss position.
	Potentially dilutive securities, which are not included in the calculation of diluted net loss per share attributable to common stockholders because to do so would be anti-dilutive, are as follows (in common stock equivalent shares):
		As of September 30,
		2014		2013
	Convertible preferred stock		—		11,313,370
	Options to purchase common stock		3,263,733		2,982,730
	Warrants to purchase common stock		250,646		250,646
Recently Issued Accounting Standards	'
	Recently Issued Accounting Standards
	In August 2014, the FASB issued Accounting Standards Update, or ASU, No. 2014-15, “Presentation of Financial Statements—Going Concern (Subtopic 205-40): Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern,” or ASU 2014-15. ASU 2014-15 will require management to assess, at each annual and interim reporting period, the entity’s ability to continue as a going concern. The amendments in ASU 2014-15 do not have any application to an entity’s financial statements, but only to disclosure in the related notes. ASU 2014-15 is effective for annual periods ending after December 15, 2016 and early application is permitted. We intend to apply ASU 2014-15 beginning with the first quarter of fiscal year 2016.
	In June 2014, the FASB issued ASU No. 2014-10, “Development Stage Entities (Topic 915)—Elimination of Certain Financial Reporting Requirements, Including an Amendment to Variable Interest Entities Guidance in Topic 810, Consolidation,” or ASU 2014-10, which eliminates the concept of a development stage entity in its entirety from current accounting guidance and provides for certain amendments to the consolidation guidance in ASC Topic 810. Prior to the issuance of this guidance, we were considered a development stage entity and as a result we included certain inception-to-date disclosures in our financial statements. The guidance related to the elimination of the concept of a development stage entity is effective for public companies for annual reporting periods beginning after December 15, 2014, and interim periods therein. The amendment of the consolidation guidance in Topic 810 is effective for public companies for annual reporting periods beginning after December 15, 2015. Early adoption of the new standard is permitted. We adopted ASU No. 2014-10 during the quarter ended June 30, 2014. As such, all inception-to-date disclosures have been removed from these condensed consolidated financial statements.

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2014
Accounting Policies [Abstract]	'
Schedule of Potentially Dilutive Securities Not Included in Calculation of Diluted Net Loss per Share	'
	Potentially dilutive securities, which are not included in the calculation of diluted net loss per share attributable to common stockholders because to do so would be anti-dilutive, are as follows (in common stock equivalent shares):
		As of September 30,
		2014		2013
	Convertible preferred stock		—		11,313,370
	Options to purchase common stock		3,263,733		2,982,730
	Warrants to purchase common stock		250,646		250,646

Other_Financial_Information_Ta

Other Financial Information (Tables)	9 Months Ended
	Sep. 30, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]	'
Schedule of Property and Equipment, Leasehold Improvements, and Related Accumulated Depreciation and Amortization	'
	Property and equipment, leasehold improvements, and related accumulated depreciation and amortization were as follows (in thousands):
		September 30,			December 31,
		2014			2013
	Manufacturing and laboratory equipment	$	3,991		$	3,229
	Office furniture and equipment		113			112
	Clinical equipment		2,129			1,606
	Computer equipment and software		150			122
	Leasehold improvements		3,210			2,830
	Construction in progress		—			323
			9,593			8,222
	Less: accumulated depreciation and amortization		(6,608	)		(5,755	)
	Total	$	2,985		$	2,467
Schedule of Accrued Expenses	'
	Accrued expenses consist of (in thousands):
		September 30,			December 31,
		2014			2013
	Accrued clinical and related costs	$	5,216		$	2,067
	Accrued compensation and related taxes		1,684			512
	Accrued financing costs		408			496
	Accrued other		222			178
	Total	$	7,530		$	3,253

Fair_Value_Tables

Fair Value (Tables)	9 Months Ended
	Sep. 30, 2014
Fair Value Disclosures [Abstract]	'
Schedule of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis	'
	The following fair value hierarchy table presents information about each major category of our financial assets and liabilities measured at fair value on a recurring basis (in thousands):
		Fair Value Measurement at September 30, 2014
		Fair Value			Level 1		Level 2		Level 3
	Assets
	Cash equivalents:
	Money market funds	$	76,222		$	76,222	$	—	$	—
		Fair Value Measurement at December 31, 2013
		Fair Value			Level 1		Level 2		Level 3
	Assets
	Cash equivalents:
	Money market funds	$	37,158		$	37,158	$	—	$	—
	Liabilities
	Future purchase rights	$	2,600		$	—	$	—	$	2,600
Schedule of Changes in Level 3 Future Purchase Rights Liabilities Measured at Fair Value on Recurring Basis	'
	The following table summarizes the changes in Level 3 future purchase rights liabilities measured at fair value on a recurring basis for the nine months ended September 30, 2014 (in thousands):
		Fair Value of
		Future Purchase
		Rights Liabilities
	Balance at January 1, 2014	$	2,600
	Re-measurement of future purchase rights		(2,600	)
	Balance at September 30, 2014	$	—
Schedule of Future Purchase Rights Liabilities Using Binomial Lattice Option Pricing Model	'
	We valued the future purchase rights liabilities as of December 31, 2013, using a binomial lattice option pricing model with the following assumptions:
		December 31,
		2013
	Common stock fair value	$	5.93
	Preferred stock price	$	8
	Volatility		85	%
	Risk-free interest rate		0.38	%
	Contractual life (years)		2.08
	Number of nodes		25
	Dividend yield		0	%

Common_Stock_Tables

Common Stock (Tables)	9 Months Ended
	Sep. 30, 2014
Equity [Abstract]	'
Shares Reserved for Future Issuance	'
	Shares reserved for future issuance at September 30, 2014 are as follows:
		Number of
		Shares
	Common stock warrants		250,646
	Common stock options outstanding		3,263,733
	Common stock options available for future grant		462,685
	Total common shares reserved for future issuance		3,977,064

Stock_Compensation_Plans_Table

Stock Compensation Plans (Tables)	9 Months Ended
	Sep. 30, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
Summary of Stock Option Activity	'
	The following table summarizes employee and nonemployee stock option activity:
		Options			Weighted-		Weighted-		Aggregate
					Average		Average		Intrinsic
					Exercise		Remaining		Value
					Price		Contractual
							Term (Years)
	Outstanding as of January 1, 2014		3,098,573		$	6.71
	Granted		211,245		$	15.89
	Exercised		(119	)	$	12.49
	Forfeited		(45,966	)	$	8.46
	Outstanding as of September 30, 2014		3,263,733		$	7.08		8.19	$	43,796,123
	Options vested and expected to vest as of September 30, 2014		3,258,131		$	7.08		8.19	$	43,722,647
	Options exercisable as of September 30, 2014		3,131,179		$	6.55		8.13	$	43,421,753
Ranges of Underlying Assumptions Used in BSM Option Pricing Model to Determine Fair Value of Stock Options Granted to Employees and Nonemployees	'
	The following are the ranges of underlying assumptions used in the BSM option pricing model to determine the fair value of stock options granted to employees and nonemployees:
		Nine Months Ended September 30,
		2014		2013
	Employees:
	Risk-free interest rate	1.60% - 1.88%		0.76% - 0.91%
	Expected dividend yield	0%		0%
	Expected volatility	81% - 85%		100%
	Expected term of options (years)	6		5
	Fair value of common stock	$7.55 - $24.04		$6.82 - $9.94
	Nonemployees:
	Risk-free interest rate	0.11% - 1.20%		0.15% - 0.67%
	Expected dividend yield	0%		0%
	Expected volatility	73% - 85%		100%
	Expected term of options (years)	4-Jan		4-Jan
	Fair value of common stock	$11.31 - $27.24		$6.82 - $9.94
Schedule of Stock-based Compensation Expense Valuation Analysis Probability-Weighted Scenarios	'
	February 12, 2014 Valuation Analysis
	Our analysis considered the following probability-weighted scenarios:
	Scenario	Weight
	IPO by May 15, 2014		25	%
	Sale by September 30, 2015		10	%
	Private company		50	%
	Dissolution		15	%
	March 31, 2014 Valuation Analysis
	Our analysis considered the following probability-weighted scenarios:
	Scenario	Weight
	IPO by April 15, 2014		65	%
	Sale by September 30, 2015		10	%
	Private company		15	%
	Dissolution		10	%
Schedule of Stock-based Compensation Expense for Stock Awards Recognized	'
	Total stock-based compensation expense for employee and nonemployee stock awards to employees and nonemployees recognized in our condensed consolidated statements of operations is as follows (in thousands):
		Three Months Ended					Nine Months Ended
		September 30,					September 30,
		2014			2013		2014		2013
	Employees:
	Research and development	$	194		$	84	$	517	$	141
	General and administrative		238			134		642		300
	Total	$	432		$	218	$	1,159	$	441
	Nonemployees:
	Research and development	$	211		$	51	$	572	$	122
	General and administrative		14			22		34		28
	Total	$	225		$	73	$	606	$	150

Summary_of_Significant_Account2

Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	9 Months Ended	12 Months Ended			9 Months Ended
	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2014
			Early Exercise of Stock Options [Member]	Early Exercise of Stock Options [Member]	Minimum [Member]	Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]	'	'	'	'	'	'
Property and equipment, estimated useful lives	'	'	'	'	'3 years	'5 years
Impairment losses	$0	'	'	'	'	'
Expected dividend yield	0.00%	0.00%	'	'	'	'
Shares issued upon early exercise of stock options and are subject to future vesting	'	'	29,622	50,336	'	'

Summary_of_Significant_Account3

Summary of Significant Accounting Policies - Schedule of Potentially Dilutive Securities Not Included in Calculation of Diluted Net Loss per Share (Detail)	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Convertible Preferred Stock (Junior) [Member]	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'
Potentially dilutive securities not included in the calculation of diluted net loss per share	'	11,313,370
Options to Purchase Common Stock [Member]	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'
Potentially dilutive securities not included in the calculation of diluted net loss per share	3,263,733	2,982,730
Warrants to Purchase Common Stock [Member]	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'
Potentially dilutive securities not included in the calculation of diluted net loss per share	250,646	250,646

Other_Financial_Information_Sc

Other Financial Information - Schedule of Property and Equipment, Leasehold Improvements, and Related Accumulated Depreciation and Amortization (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Property, Plant and Equipment [Line Items]	'	'
Property and equipment, gross	$9,593	$8,222
Less: accumulated depreciation and amortization	-6,608	-5,755
Property and equipment, net	2,985	2,467
Manufacturing and Laboratory Equipment [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Property and equipment, gross	3,991	3,229
Office Furniture and Equipment [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Property and equipment, gross	113	112
Clinical Equipment [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Property and equipment, gross	2,129	1,606
Computer Equipment and Software [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Property and equipment, gross	150	122
Leasehold Improvements [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Property and equipment, gross	3,210	2,830
Construction in Progress [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Property and equipment, gross	'	$323

Other_Financial_Information_Ad

Other Financial Information - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Property, Plant and Equipment [Abstract]	'	'	'	'
Depreciation and amortization expense	$310	$256	$853	$568

Other_Financial_Information_Sc1

Other Financial Information - Schedule of Accrued Expenses (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Payables and Accruals [Abstract]	'	'
Accrued clinical and related costs	$5,216	$2,067
Accrued compensation and related taxes	1,684	512
Accrued financing costs	408	496
Accrued other	222	178
Total	$7,530	$3,253

Commitments_and_Contingencies_

Commitments and Contingencies - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Commitments and Contingencies Disclosure [Abstract]	'	'	'	'	'
Non-cancellable operating lease agreements	'	'	'2017	'	'
Total rent expense under operating leases	$203,000	$169,000	$596,000	$457,000	'
Current deferred rent	123,000	'	123,000	'	142,000
Long-term deferred rent	$283,000	'	$283,000	'	$321,000

Fair_Value_Schedule_of_Financi

Fair Value - Schedule of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (Fair Value, Measurements, Recurring [Member], USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Level 1 [Member] | Cash Equivalents [Member] | Money Market Funds [Member]	'	'
Assets	'	'
Assets	$76,222	$37,158
Level 3 [Member] | Future Purchase Rights [Member]	'	'
Liabilities	'	'
Liabilities	'	2,600
Fair Value [Member] | Future Purchase Rights [Member]	'	'
Liabilities	'	'
Liabilities	'	2,600
Fair Value [Member] | Cash Equivalents [Member] | Money Market Funds [Member]	'	'
Assets	'	'
Assets	$76,222	$37,158

Fair_Value_Additional_Informat

Fair Value - Additional Information (Detail) (USD $)	9 Months Ended
	Sep. 30, 2014
Debt Instrument Fair Value Carrying Value [Abstract]	'
Fair value transfers of assets and liabilities between levels	$0

Fair_Value_Schedule_of_Changes

Fair Value - Schedule of Changes in Level 3 Future Purchase Rights Liabilities Measured at Fair Value on Recurring Basis (Detail) (Fair Value Of Future Purchase Rights Liabilities [Member], Level 3 [Member], USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014
Fair Value Of Future Purchase Rights Liabilities [Member] | Level 3 [Member]	'
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]	'
Balance at January 1, 2014	$2,600
Re-measurement of future purchase rights	-2,600
Balance at September 30, 2014	$0

Fair_Value_Schedule_of_Future_

Fair Value - Schedule of Future Purchase Rights Liabilities Using Binomial Lattice Option Pricing Model (Detail) (USD $)	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2013	Mar. 31, 2014	Feb. 12, 2014
		Nodes
Fair Value Disclosures [Abstract]	'	'	'	'
Common stock fair value	'	$5.93	$11.30	$7.55
Preferred stock price	'	$8	'	'
Volatility	'	85.00%	'	'
Risk-free interest rate	'	0.38%	'	'
Contractual life (years)	'	'2 years 29 days	'	'
Number of nodes	'	25	'	'
Dividend yield	0.00%	0.00%	'	'

Convertible_and_Redeemable_Con1

Convertible and Redeemable Convertible Preferred Stock - Additional Information (Detail) (USD $)

3 Months Ended

9 Months Ended

9 Months Ended

1 Months Ended

9 Months Ended

1 Months Ended

9 Months Ended

0 Months Ended

1 Months Ended

9 Months Ended

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Dec. 31, 2013

Sep. 30, 2014

Sep. 30, 2014

Feb. 28, 2014

Sep. 30, 2014

Jan. 31, 2014

Dec. 31, 2013

Jan. 31, 2014

Sep. 30, 2014

Feb. 29, 2012

Feb. 29, 2012

Apr. 30, 2014

Sep. 30, 2014

Minimum [Member]

Maximum [Member]

Redeemable Convertible Preferred Stock (Senior) [Member]

Redeemable Convertible Preferred Stock (Senior) [Member]

Redeemable Convertible Preferred Stock (Senior) [Member]

Redeemable Convertible Preferred Stock (Senior) [Member]

Redeemable Convertible Preferred Stock (Senior) [Member]

Redeemable Convertible Preferred Stock (Senior) [Member]

Nonredeemable Convertible Preferred Stock [Member]

Nonredeemable Convertible Preferred Stock [Member]

Convertible Preferred Stock (Junior) [Member]

Convertible Preferred Stock (Junior) [Member]

Preferred Stock Purchase Agreement [Member]

Preferred Stock Purchase Agreement [Member]

Preferred Stock Purchase Agreement [Member]

Future Purchase Rights [Member]

Private Placement [Member]

Class of Stock [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Net proceeds from issuance of preferred stock

'

'

'

'

'

'

'

'

'

'

'

'

'

$1,500,000

$1,300,000

'

'

Convertible preferred stock, price per share

'

'

'

'

'

'

'

'

'

'

'

$8

$8

$0.43

'

'

'

Convertible preferred stock, shares issued

'

'

'

'

'

'

'

241,016

'

555,000

10,212,007

1,500,000

'

3,501,400

'

'

'

Preferred stock converted into common stock

'

'

'

'

'

'

'

'

'All the outstanding shares of our senior redeemable convertible preferred stock were converted into common stock on a one-to-one basis

'

'

'

'

'

'

'

'One-to-one basis

Issuance costs

'

'

19,000

'

'

'

'

35,000

727,000

135,000

'

31,000

'

'

'

31,000

'

Proceeds from issuance of preferred stock

'

'

'

'

'

'

'

1,900,000

'

4,300,000

'

12,000,000

'

'

'

'

'

Discounts and commissions

'

'

'

'

'

'

'

'

3,800,000

'

'

'

'

'

'

'

'

Deemed dividend

0

10,000

4,700,000

21,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Aggregate conversion amount of preferred stock

'

'

$878,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Weighted-average exercise per share

$95.21

'

$95.21

'

$95.21

'

'

'

'

'

'

'

'

'

'

'

'

Common stock warrants outstanding and exercisable

250,646

'

250,646

'

250,646

'

'

'

'

'

'

'

'

'

'

'

'

Common stock warrants expiration period

'

'

'

'

'

29-Feb-16

30-Sep-19

'

'

'

'

'

'

'

'

'

'

Common_Stock_Additional_Inform

Common Stock - Additional Information (Detail) (USD $)	9 Months Ended		1 Months Ended
	Sep. 30, 2014	Dec. 31, 2013	Apr. 30, 2014	31-May-14	31-May-14
			IPO [Member]	Underwriters [Member]	Over-Allotment Option [Member]
Class of Stock [Line Items]	'	'	'	'	'
Common stock sold, shares	'	'	4,500,000	'	675,000
Common stock sold, per share	'	'	$12	$12	'
Net proceeds from IPO after underwriters' discounts and commissions	'	'	$50,200,000	$7,500,000	'
Estimated offering expenses	'	'	5,800,000	'	'
Total costs	19,000	'	9,600,000	'	'
Underwriting discounts and commission	'	'	'	567,000	'
Net estimated offering proceeds	'	'	$44,400,000	$51,900,000	'
Authorized shares of capital stock	'	'	150,000,000	'	'
Shares of preferred stock authorized	20,000,000	25,000,000	20,000,000	'	'
Shares of common stock authorized	130,000,000	29,250,000	130,000,000	'	'

Common_Stock_Shares_Reserved_f

Common Stock - Shares Reserved for Future Issuance (Detail)	Sep. 30, 2014	Dec. 31, 2013
Equity [Abstract]	'	'
Common stock warrants	250,646	250,646
Common stock options outstanding	3,263,733	3,098,573
Common stock options available for future grant	462,685	'
Total common shares reserved for future issuance	3,977,064	'

Stock_Compensation_Plans_Addit

Stock Compensation Plans - Additional Information (Detail) (USD $)

9 Months Ended

0 Months Ended

1 Months Ended

0 Months Ended

1 Months Ended

9 Months Ended

Sep. 30, 2014

Sep. 30, 2013

Mar. 31, 2014

Feb. 12, 2014

Dec. 31, 2013

Feb. 12, 2014

Feb. 12, 2014

Mar. 31, 2014

Feb. 12, 2014

Mar. 31, 2014

Mar. 31, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

IPO by May 15, 2014 [Member]

Sale [Member]

Sale [Member]

Private Company [Member]

Private Company [Member]

IPO by April 15, 2014 [Member]

Two Thousand Twelve Stock Option Plan [Member]

Two Thousand And Fourteen Equity Incentive Plan [Member]

2012 and 2014 Equity Incentive Plans [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Option grants under Equity Incentive Plans, term

'

'

'

'

'

'

'

'

'

'

'

'10 years

'10 years

'

Option vesting under Equity Incentive Plans, term

'

'

'

'

'

'

'

'

'

'

'

'4 years

'4 years

'

Common stock exercised

119

'

'

'

'

'

'

'

'

'

'

55,516

'

'

Unvested common stock option to repurchase

'

'

'

'

'

'

'

'

'

'

'

29,622

'

'

Stock option repurchase liability

'

'

'

'

'

'

'

'

'

'

'

$149,000

'

'

Shares of common stock for annual increase in shares available for issuance

'

'

'

'

'

'

'

'

'

'

'

'

1,200,000

'

Percentage of outstanding shares of common stock for annual increase in shares available for issuance

'

'

'

'

'

'

'

'

'

'

'

'

3.00%

'

Aggregate number of shares issued under the plan

'

'

'

'

'

'

'

'

'

'

'

'

'

3,726,418

Weighted-average grant date fair value of stock options granted

$11.08

$5.67

'

'

'

'

'

'

'

'

'

'

'

'

Discount for lack of marketability

'

'

'

'

'

8.00%

20.00%

17.00%

28.00%

27.00%

2.00%

'

'

'

Fair value of per share

'

'

$11.30

$7.55

$5.93

'

'

'

'

'

'

'

'

'

Compensation cost related to unvested stock option awards

$5,500,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Remaining weighted-average vesting period

'2 years 3 months 18 days

'

'

'

'

'

'

'

'

'

'

'

'

'

Stock_Compensation_Plans_Summa

Stock Compensation Plans - Summary of Stock Option Activity (Detail) (USD $)	9 Months Ended
	Sep. 30, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
Options, Outstanding, Beginning balance	3,098,573
Options, Granted	211,245
Options, Exercised	-119
Options, Forfeited	-45,966
Options, Outstanding, Ending balance	3,263,733
Options vested and expected to vest, Ending balance	3,258,131
Options exercisable, Ending balance	3,131,179
Outstanding, Weighted-Average Exercise Price, Beginning balance	$6.71
Granted, Weighted-Average Exercise Price	$15.89
Exercised, Weighted-Average Exercise Price	$12.49
Forfeited, Weighted-Average Exercise Price	$8.46
Outstanding, Weighted-Average Exercise Price, Ending balance	$7.08
Options vested and expected to vest, Weighted-Average Exercise Price, Ending balance	$7.08
Options exercisable, Weighted-Average Exercise Price, Ending balance	$6.55
Outstanding, Weighted-Average Remaining Contractual Term (Years), Ending balance	'8 years 2 months 9 days
Options vested and expected to vest , Weighted-Average Remaining Contractual Term (Years), Ending balance	'8 years 2 months 9 days
Options exercisable, Weighted-Average Remaining Contractual Term (Years), Ending balance	'8 years 1 month 17 days
Outstanding, Aggregate Intrinsic Value, Ending balance	$43,796,123
Options vested and expected to vest , Aggregate Intrinsic Value, Ending balance	43,722,647
Options exercisable, Aggregate Intrinsic Value, Ending balance	$43,421,753

Stock_Compensation_Plans_Range

Stock Compensation Plans - Ranges of Underlying Assumptions Used in BSM Option Pricing Model to Determine Fair Value of Stock Options Granted to Employees and Nonemployees (Detail) (USD $)

Mar. 31, 2014

Feb. 12, 2014

Dec. 31, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Employees [Member]

Employees [Member]

Employees [Member]

Employees [Member]

Employees [Member]

Employees [Member]

Nonemployees [Member]

Nonemployees [Member]

Nonemployees [Member]

Nonemployees [Member]

Nonemployees [Member]

Nonemployees [Member]

Minimum [Member]

Minimum [Member]

Maximum [Member]

Maximum [Member]

Minimum [Member]

Minimum [Member]

Maximum [Member]

Maximum [Member]

Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Method Used [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Risk-free interest rate, minimum

'

'

'

1.60%

0.76%

'

'

'

'

0.11%

0.15%

'

'

'

'

Risk-free interest rate, maximum

'

'

'

1.88%

0.91%

'

'

'

'

1.20%

0.67%

'

'

'

'

Expected dividend yield

'

'

'

0.00%

0.00%

'

'

'

'

0.00%

0.00%

'

'

'

'

Expected volatility, minimum

'

'

'

81.00%

'

'

'

'

'

73.00%

'

'

'

'

'

Expected volatility, maximum

'

'

'

85.00%

'

'

'

'

'

85.00%

'

'

'

'

'

Expected volatility

'

'

'

'

100.00%

'

'

'

'

'

100.00%

'

'

'

'

Expected term of options (years)

'

'

'

'6 years

'5 years

'

'

'

'

'

'

'1 year

'1 year

'4 years

'4 years

Fair value of common stock

$11.30

$7.55

$5.93

'

'

$7.55

$6.82

$24.04

$9.94

'

'

$11.31

$6.82

$27.24

$9.94

Stock_Compensation_Plans_Sched

Stock Compensation Plans - Schedule of Stock-based Compensation Expense Valuation Analysis Probability-Weighted Scenarios (Detail)	0 Months Ended	1 Months Ended
	Feb. 12, 2014	Mar. 31, 2014
IPO by May 15, 2014 [Member]	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Probability-weighted scenarios, percentage	25.00%	'
Sale by September 30, 2015 [Member]	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Probability-weighted scenarios, percentage	10.00%	10.00%
Private Company [Member]	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Probability-weighted scenarios, percentage	50.00%	15.00%
Dissolution [Member]	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Probability-weighted scenarios, percentage	15.00%	10.00%
IPO by April 15, 2014 [Member]	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Probability-weighted scenarios, percentage	'	65.00%

Stock_Compensation_Plans_Sched1

Stock Compensation Plans - Schedule of Stock-Based Compensation Expense for Stock Awards Recognized (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]	'	'	'	'
Stock-based compensation expense	'	'	$1,765	$591
Employees [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]	'	'	'	'
Stock-based compensation expense	432	218	1,159	441
Nonemployees [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]	'	'	'	'
Stock-based compensation expense	225	73	606	150
Research and Development [Member] | Employees [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]	'	'	'	'
Stock-based compensation expense	194	84	517	141
Research and Development [Member] | Nonemployees [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]	'	'	'	'
Stock-based compensation expense	211	51	572	122
General and Administrative [Member] | Employees [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]	'	'	'	'
Stock-based compensation expense	238	134	642	300
General and Administrative [Member] | Nonemployees [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]	'	'	'	'
Stock-based compensation expense	$14	$22	$34	$28

Subsequent_Event_Additional_In

Subsequent Event - Additional Information (Detail) (USD $)	9 Months Ended	1 Months Ended
	Sep. 30, 2014	Nov. 30, 2014	Oct. 31, 2014
		Scenario, Forecast [Member]	Subsequent Event [Member]
Subsequent Event [Line Items]	'	'	'
Common stock sold, shares	'	50,000	2,000,000
Common stock sold, per share	'	$17.50	$17.50
Net proceeds from public offering after underwriters' discounts and commissions	'	$800,000	$32,600,000
Estimated offering expenses	'	'	540,000
Total estimated costs	19,000	'	3,000,000
Net estimated offering proceeds	'	$32,800,000	$32,000,000