Sierra Oncology (SRRA) 10-Q 21 Aug 15 2015 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2015	Aug. 20, 2015
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	Q2
Trading Symbol	DNAI
Entity Registrant Name	ProNAi Therapeutics Inc
Entity Central Index Key	1,290,149
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		30,058,105

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
CURRENT ASSETS:
Cash and cash equivalents (Note 5)	$ 15,800	$ 29,154
Short-term investments (Note 4)	10,028	10,010
Prepaid expenses and other current assets (Note 5)	782	561
Total current assets	26,610	39,725
Property and equipment, net (Note 5)	397	214
Other assets (Note 5)	3,256	626
TOTAL ASSETS	30,263	40,565
CURRENT LIABILITIES:
Accrued liabilities (Note 5)	2,304	1,473
Accounts payable	1,925	622
Total current liabilities	4,229	2,095
Preferred stock warrant liabilities (Note 9)	10,641	1,810
Other liabilities	113	100
TOTAL LIABILITIES	$ 14,983	$ 4,005
Commitments and Contingencies (Note 6)
Preferred stock value	$ 297,652	$ 144,375
STOCKHOLDERS' DEFICIT:
Common stock, $0.001 par value; 180,000,000 shares authorized as of June 30, 2015 and December 31, 2014 and 1,616,514 and 1,588,701 shares issued and outstanding as of June 30, 2015 and December 31, 2014	2	2
Additional paid-in capital	0	0
Accumulated other comprehensive loss		(10)
Accumulated deficit	(282,374)	(107,807)
TOTAL STOCKHOLDERS' DEFICIT	(282,372)	(107,815)
TOTAL LIABILITIES, CONVERTIBLE AND REDEEMABLE CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' DEFICIT	30,263	40,565
Convertible Preferred Stock [Member]
CURRENT LIABILITIES:
Preferred stock value	2,543	2,543
Redeemable Convertible Preferred Stock [Member]
CURRENT LIABILITIES:
Preferred stock value	$ 295,109	$ 141,832

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Preferred stock, shares authorized	136,074,466	135,913,741
Preferred stock, shares issued	17,357,903	17,266,628
Preferred stock, shares outstanding	17,357,903	17,266,628
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	180,000,000	180,000,000
Common stock, shares issued	1,616,514	1,588,701
Common stock, shares outstanding	1,616,514	1,588,701
Convertible Preferred Stock [Member]
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	1,843,894	1,843,894
Preferred stock, shares issued	224,564	224,564
Preferred stock, shares outstanding	224,564	224,564
Preferred stock, aggregate liquidation preference	$ 2.5	$ 2.5
Redeemable Convertible Preferred Stock [Member]
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	134,230,572	134,069,847
Preferred stock, shares issued	17,133,339	17,042,064
Preferred stock, shares outstanding	17,133,339	17,042,064
Preferred stock, aggregate liquidation preference	$ 107.9	$ 103.5

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Operating expenses:
Research and development	$ 4,738	$ 12,717	$ 10,034	$ 14,544
General and administrative	1,874	791	3,315	1,284
Total operating expenses	6,612	13,508	13,349	15,828
Loss from operations	(6,612)	(13,508)	(13,349)	(15,828)
Other income (expense), net:
Change in fair value of preferred stock warrants	(8,630)	(347)	(9,956)	(496)
Other income (expense)	(6)	31	19	33
Total other income (expense), net	(8,636)	(316)	(9,937)	(463)
Loss before provision for income taxes	(15,248)	(13,824)	(23,286)	(16,291)
Provision for income tax	1		11
Net loss	(15,249)	(13,824)	(23,297)	(16,291)
Adjustment to redemption value on redeemable convertible preferred stock	(140,880)	(36,833)	(151,885)	(39,275)
Net loss attributable to common stockholders	$ (156,129)	$ (50,657)	$ (175,182)	$ (55,566)
Net loss per share attributable to common stockholders, basic and diluted (Note 3)	$ (104.10)	$ (55.04)	$ (117.35)	$ (62.72)
Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted (Note 3)	1,499,840	920,441	1,492,764	885,872

Condensed Consolidated Stateme5

Condensed Consolidated Statement of Convertible and Redeemable Convertible Preferred Stock and Stockholders' Deficit - 6 months ended Jun. 30, 2015 - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Other Comprehensive Loss [Member]	Accumulated Deficit [Member]	Convertible Preferred Stock [Member]	Redeemable Convertible Preferred Stock [Member]
Stockholders Equity, Beginning Balance at Dec. 31, 2014	$ (107,815)	$ 2		$ (10)	$ (107,807)
Stockholders Equity, Beginning Balance, Shares at Dec. 31, 2014	1,588,701	1,588,701
Temporary Equity, Beginning Balance at Dec. 31, 2014	$ 144,375					$ 2,543	$ 141,832
Temporary Equity, Beginning Balance, Shares at Dec. 31, 2014	17,266,628					224,564	17,042,064
Issuance of common stock for exercise of stock options	$ 15		$ 15
Issuance of common stock for exercise of stock options, Shares		27,813
Stock-based compensation	600		600
Issuance of redeemable convertible preferred stock upon exercise of redeemable convertible preferred stock warrants for cash							$ 1,392
Issuance of redeemable convertible preferred stock upon exercise of redeemable convertible preferred stock warrants for cash, Shares							91,275
Adjustment to redemption value on redeemable convertible preferred stock	(151,885)		$ (615)		(151,270)		$ 151,885
Reclassification of other-than-temporary losses on short-term investments to net loss	10			$ 10
Net loss	(23,297)				(23,297)
Stockholders Equity, Ending Balance at Jun. 30, 2015	$ (282,372)	$ 2			$ (282,374)
Stockholders Equity, Ending Balance, Shares at Jun. 30, 2015	1,616,514	1,616,514
Temporary Equity, Ending Balance at Jun. 30, 2015	$ 297,652					$ 2,543	$ 295,109
Temporary Equity, Ending Balance, Shares at Jun. 30, 2015	17,357,903					224,564	17,133,339

Condensed Consolidated Stateme6

Condensed Consolidated Statements of Cash Flows - USD ($)	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (23,297,000)	$ (16,291,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Change in fair value of preferred stock warrant liabilities	9,956,000	496,000
Stock-based compensation	600,000	81,000
Depreciation and amortization	39,000	1,000
Impairment on short-term investments	10,000
Deferred income taxes	(1,000)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(196,000)	(33,000)
Accrued liabilities	216,000	3,000
Accounts payable	438,000	811,000
Net cash used in operating activities	(12,235,000)	(14,932,000)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of short-term investments	(18,000)
Change in restricted cash	(150,000)
Purchase of property and equipment	(254,000)	(12,000)
Net cash used in investing activities	(422,000)	(12,000)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of redeemable convertible preferred stock, net of issuance costs		57,545,000
Repayment of stock subscription receivable		1,159,000
Proceeds from exercise of redeemable convertible preferred stock warrants	267,000
Proceeds from exercise of common stock options	15,000	39,000
Proceeds from early exercise of stock options	13,000
Payment of deferred offering costs	(992,000)	(148,000)
Net cash provided by (used in) financing activities	(697,000)	58,595,000
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	(13,354,000)	43,651,000
CASH AND CASH EQUIVALENTS - Beginning of period	29,154,000	2,429,000
CASH AND CASH EQUIVALENTS - End of period	15,800,000	46,080,000
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:
Cash paid for income taxes	3,000
Cash paid for interest	0	0
SUPPLEMENTAL DISCLOSURES OF NON-CASH INVESTING AND FINANCING INFORMATION:
Change in redemption value of redeemable convertible preferred stock	(151,885,000)	(39,275,000)
Issuance of redeemable convertible preferred stock on exercise of warrants	1,125,000
Deferred offering costs included in accounts payable and accrued liabilities	1,744,000	37,000
Property and equipment purchases included in accounts payable	$ 7,000	7,000
Series C Redeemable Convertible Preferred Stock [Member]
SUPPLEMENTAL DISCLOSURES OF NON-CASH INVESTING AND FINANCING INFORMATION:
Conversion of long-term note payable and accrued interest into Series C redeemable convertible preferred stock		$ 433,000

The Company and Basis of Presen

The Company and Basis of Presentation	6 Months Ended
	Jun. 30, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
The Company and Basis of Presentation	1. The Company and Basis of Presentation Organization and Description of Business ProNAi Therapeutics, Inc. (together with its subsidiaries, collectively referred to as the “Company”), a Delaware corporation, is a clinical-stage oncology company pioneering a novel class of therapeutics based on its proprietary DNAi technology platform. The core of the Company’s scientific expertise is its understanding of DNAi oligonucleotides, which are rationally designed DNA sequences that modulate the transcription of oncogenes known to be involved in cancer cell survival and proliferation. The Company’s lead DNAi product candidate, PNT2258, targets BCL2, a widely overexpressed oncogene that is an important gatekeeper of the programmed cell death pathway known as apoptosis and has been linked to many forms of cancer. The Company’s primary activities since inception have been conducting research and development activities, conducting preclinical and clinical testing, recruiting personnel, performing business and financial planning, and raising capital to support development activities. The Company has not generated any product revenue related to its primary business purpose to date, nor has it generated any income, and is subject to a number of risks and uncertainties, which include dependence on key individuals, the need for development of commercially viable products, the need to obtain regulatory approval for its products and commercialize them and the need to obtain adequate additional financing to fund the development of its product candidates. Initial Public Offering On July 15, 2015, the Company’s Registration Statement on Form S-1 (File No. 333-204921) relating to the initial public offering (IPO) of its common stock was declared effective by the Securities and Exchange Commission (SEC). Pursuant to such Registration Statement, the Company sold an aggregate of 9,315,000 shares of its common stock at a price of $17.00 per share for aggregate cash proceeds of approximately $143.6, net of underwriting discounts and commissions and offering costs. On July 21, 2015, immediately prior to the closing of the IPO, all outstanding shares of convertible and redeemable convertible preferred stock converted into 17,971,273 shares of common stock. The IPO closed on July 21, 2015. Reverse Stock Split On June 29, 2015, the Company’s board of directors approved an amendment to the Company’s amended and restated certificate of incorporation to effect a reverse split of the Company’s common stock, convertible preferred stock and redeemable convertible preferred stock at a 7.45-to-1 ratio (the “Reverse Stock Split”). The Reverse Stock Split became effective on July 2, 2015, upon the filing of the amendment to the Company’s amended and restated certificate of incorporation. The authorized shares and par value of the common, convertible preferred and redeemable convertible preferred stock were not adjusted as a result of the Reverse Stock Split. All issued and outstanding common stock, convertible preferred stock, redeemable convertible preferred stock, warrants for preferred stock, options for common stock and per share amounts contained in the condensed consolidated financial statements have been retroactively adjusted to reflect this Reverse Stock Split for all periods presented.

Summary Of Significant Accounti

Summary Of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2015
Accounting Policies [Abstract]
Summary Of Significant Accounting Policies	2. Summary Of Significant Accounting Policies Basis of Presentation The condensed consolidated balance sheet as of June 30, 2015, the condensed consolidated statements of operations and comprehensive loss for the three and six months ended June 30, 2015 and 2014 and the condensed consolidated statements of cash flows for the six months ended June 30, 2015 and 2014 and the condensed consolidated statements of convertible and redeemable convertible preferred stock and stockholders’ deficit for the six months ended June 30, 2015 are unaudited. The unaudited condensed consolidated financial statements have been prepared on the same basis as the annual consolidated financial statements and reflect, in the opinion of management, all adjustments of a normal and recurring nature that are necessary for the fair presentation of the Company’s condensed consolidated financial statements included in this report. The condensed consolidated financial data disclosed in these notes to the condensed consolidated financial statements related to the three and six month periods are also unaudited. The condensed consolidated results of operations for the three and six months ended June 30, 2015 are not necessarily indicative of the results to be expected for the year ending December 31, 2015, or for any other future annual or interim period. The consolidated balance sheet as of December 31, 2014 included herein was derived from the audited consolidated financial statements as of that date. These condensed consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements included in the prospectus dated July 15, 2015, filed with the SEC pursuant to Rule 424 promulgated under the Securities Act of 1933, as amended. Use of Estimates The preparation of the condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements and the reported amounts of expense during the reporting period. Significant estimates and assumptions made in the accompanying condensed consolidated financial statements include, but are not limited to the fair value of common stock, the fair value of preferred stock, the fair value of preferred stock warrant liabilities, the fair value of stock options, recoverability of the Company’s net deferred tax assets, and related valuation allowance and certain accruals. The Company evaluates its estimates and assumptions on an ongoing basis using historical experience and other factors and adjusts those estimates and assumptions when facts and circumstances dictate. Actual results could materially differ from those estimates. Foreign Currency The functional currency of the Company’s foreign subsidiary is the U.S. Dollar. Transactions denominated in currencies other than the functional currency are remeasured to the functional currency at the average exchange rate in effect during the period. At the end of each reporting period, monetary assets and liabilities are remeasured to the functional currency using exchange rates in effect at the balance sheet date. Non-monetary assets and liabilities are remeasured at historical exchange rates. Gains and losses related to remeasurement are recorded in other income (expense) in the condensed consolidated statements of operations. Cash and Cash Equivalents The Company considers all highly liquid investments with an original maturity of three months or less from the date or purchase to be cash equivalents. Cash and cash equivalents consist primarily of funds invested in readily available checking and savings accounts and highly liquid investments in money market funds. Restricted Cash Restricted cash represents collateral for a corporate credit card facility and a security deposit required for a facility lease. Restricted cash consists of funds invested in a money market fund. As of June 30, 2015, the current portion of restricted cash of $25,000 is included in prepaid expenses and other current assets and the long-term portion of restricted cash of $0.2 million is included in other assets in the accompanying condensed consolidated balance sheets. Investments The Company determines the appropriate designation of its investments as “trading,” “available-for-sale” or “held-to-maturity” based on management’s intent at the time of purchase and reevaluates such designation at each reporting date. As of June 30, 2015 and December 31, 2014, all of the Company’s short-term investments were designated as available-for-sale. Unrealized gains and losses, if any, are reported as a separate component of stockholders’ deficit, except for unrealized losses determined to be other-than-temporary which are recorded in other income (expense) in the accompanying condensed consolidated statements of operations. The Company determines any realized gains or losses on the sale of any investments on a specific identification method and records such gains and losses as a component of other income (expense) in the accompanying condensed consolidated statements of operations. The Company evaluates its short-term investments periodically for possible other-than-temporary impairment. A decline in fair value below the amortized cost of the investment is considered other-than-temporary impairment if the Company has the intent to sell the investment or it is more likely than not that the Company will be required to sell the investment before recovery of the entire amortized cost basis. In those instances, an impairment charge equal to the difference between the fair value and the amortized cost basis is recognized in other income (expense). Regardless of the Company’s intent or requirement to sell an investment, impairment is considered other-than-temporary if the Company does not expect to recover the entire amortized cost basis. Investments with original maturities beyond three months at the date of purchase and which mature at, or less than twelve months from, the balance sheet date are classified as current. Investments with a maturity beyond twelve months from the condensed consolidated balance sheet date are classified as long-term. As of June 30, 2015, the Company’s short-term investments were classified as current assets. Concentrations of Credit Risk Financial instruments that subject the Company to significant concentrations of credit risk consist of cash, cash equivalents, restricted cash and short-term investments. All of the Company’s cash, cash equivalents, restricted cash and short-term investments are held at financial institutions in the United States and Canada that management believes to be of high credit quality. Deposits held in the United States with these financial institutions exceed federally insured limits. The primary focus of the Company’s investment strategy is to preserve capital and meet liquidity requirements. The Company’s investment policy addresses the level of credit exposure by limiting the concentration in any one corporate issuer or sector and establishing a minimum allowable credit rating. Comprehensive Income (Loss) The Company had no components of comprehensive income (loss) other than net loss for all periods presented. Fair Value of Financial Instruments The Company’s cash and cash equivalents, restricted cash, short-term investments, other current assets, accounts payable, and accrued liabilities approximate their fair value at June 30, 2015 and December 31, 2014, due to their short duration. The short-term investment maintains observable inputs, thus the carrying value of this instrument is carried at fair value and unrealized gains and losses, if any, are reported as a separate component of stockholders’ deficit. The Company’s preferred stock warrant liabilities contain unobservable inputs that reflect the Company’s own assumptions in which there is little, if any, market activity at the measurement date, thus the Company’s warrant liabilities are measured at fair value on a recurring basis using unobservable inputs. The Company utilizes valuation techniques that maximize the use of observable inputs and minimize the use of unobservable inputs to the extent possible. The Company determines the fair value of its financial instruments based on assumptions that market participants would use in pricing an asset or liability in the principal or most advantageous market. When considering market participant assumptions in fair value measurements, the following fair value hierarchy distinguishes between observable and unobservable inputs, which are categorized in one of the following levels: Level 1 Level 2 Level 3 Property and Equipment, Net Property and equipment, net are stated at cost, less accumulated depreciation and amortization. Depreciation and amortization on property and equipment, excluding leasehold improvements, is computed using the straight-line Leasehold improvements are amortized on a straight-line basis over the shorter of the estimated useful lives of the assets or the remaining lease term. Amortization on leasehold improvements are amortized over the term of the related property lease, for a period of three years. Deferred Offering Costs Deferred offering costs, consisting of legal, accounting and filing fees relating to an IPO, have been capitalized. The deferred offering costs will be offset against offering proceeds upon the completion of the offering. As of June 30, 2015 and December 31, 2014, $3.1 million and $0.5 million of deferred offering costs have been capitalized, which is included in other long-term assets in the condensed consolidated balance sheets. Preferred Stock Warrant Liabilities The Company accounts for its warrants issued in connection with its various financing transactions based upon the characteristics and provisions of the instrument. Warrants classified as derivative liabilities are recorded on the Company’s condensed consolidated balance sheets at their fair value on the date of issuance and remeasured to fair value on each subsequent reporting period, with the changes in fair value recognized as a component of other income (expense), net in the accompanying condensed consolidated statements of operations. The Company will continue to adjust the liability for changes in the fair value of these warrants until the earlier of the exercise of the warrants, the expiration of the warrants, or until such time as the warrants are no longer to be considered derivative instruments. On the completion of an IPO (which occurred on July 21, 2015, as discussed in Note 1), the liability on the preferred stock warrants will be reclassified to additional paid-in capital in stockholders’ deficit. The Company estimates the fair value of these liabilities using an Option Pricing Model (OPM) or a Probability Weighted Expected Return Method (PWERM) and using assumptions that are based on the individual characteristics of the warrants or instruments on the valuation date, as well as assumptions for expected term, expected volatility and risk-free interest rate. Research and Development Costs Research and development costs are expensed as incurred. The Company accounts for nonrefundable advance payments for goods and services that will be used in future research and development activities as expenses when the goods have been received or when the service has been performed rather than when the payment is made. Depending on the timing of payments to service providers of research and development costs, the Company recognizes prepaid expenses or accrued expenses related to these costs. These prepaid or accrued expenses are based on management’s estimates of the work performed under service agreements and milestones achieved. Research and development costs include fees incurred in connection with license agreements, compensation and other related costs for employees engaged in research and development, costs associated with preclinical studies and trials, regulatory activities, manufacturing activities to support clinical activities, license fees, fees paid to external service providers that conduct certain research and development, clinical, and manufacturing activities on behalf of the Company and an allocation of overhead expenses. Stock-Based Compensation The Company accounts for share-based payments at fair value, which is measured using the Black-Scholes option-pricing model. For share-based awards that vest subject to the satisfaction of a service requirement, the fair value measurement date for employee stock-based compensation awards is the date of grant and the expense is recognized on a straight line basis, over the vesting period. For share-based awards that vest subject to the satisfaction of a service requirement and a performance component, the fair value measurement date is the date of grant and is recognized over the requisite service period as achievement of the performance objective becomes probable. No expense has been recorded to date relating to this grant as the performance condition hasn’t been achieved. Stock-based compensation arrangements with nonemployees are recognized at the grant date and remeasured to fair value at each reporting period. The expense is recognized over the vesting period which is generally the service period. Income Taxes The Company uses the asset and liability method of accounting for income taxes. Under this method, deferred tax assets and liabilities are determined based on the differences between the financial reporting and the tax bases of assets and liabilities and are measured using the enacted tax rates and laws that will be in effect when the differences are expected to reverse. Management makes an assessment of the likelihood that the resulting deferred tax assets will be realized. A valuation allowance is provided when it is more likely than not that some portion or all of a deferred tax asset will not be realized. Due to the Company’s historical operating performance and the recorded cumulative net losses in prior fiscal periods, the net deferred tax assets have been fully offset by a valuation allowance. The Company recognizes uncertain income tax positions at the largest amount that is more likely than not to be sustained upon audit by the relevant taxing authority. An uncertain income tax position will not be recognized if it has less than a 50% likelihood of being sustained. Changes in recognition or measurement are reflected in the period in which judgment occurs. The Company’s policy is to recognize interest and penalties related to the underpayment of income taxes as a component of provision for income taxes. Segment Information Operating segments are components of an enterprise for which separate financial information is available and is evaluated regularly by the Company’s chief operating decision maker in deciding how to allocate resources and assessing performance. The Company’s chief operating decision maker is its Chief Executive Officer. The Company’s Chief Executive Officer views the Company’s operations and manages its business in one operating segment, which is the business of researching, developing, and commercializing therapies for the treatment of patients with cancer. Accordingly, the Company has a single reporting segment.

Net Loss Per Share

Net Loss Per Share	6 Months Ended
	Jun. 30, 2015
Earnings Per Share [Abstract]
Net Loss Per Share	3. Net Loss Per Share Basic net loss per share is calculated by dividing net loss attributable to common stockholders by the weighted-average number of common shares outstanding during the period, less common stock issued that is subject to repurchase, without consideration for common stock equivalents. Diluted net loss per share is computed by dividing net loss by the weighted-average number of common share equivalents outstanding for the period determined using the treasury-stock method. For purposes of this calculation, convertible and redeemable convertible preferred stock and warrants for preferred stock, stock options and common stock subject to repurchase are considered to be common stock equivalents and are only included in the calculation of diluted net loss per share when their effect is dilutive. The following outstanding shares of common stock equivalents were excluded from the calculation of diluted net loss per share attributable to common stockholders for the periods presented because including them would have been antidilutive: As of June 30, 2015 2014 Options to purchase common stock 3,294,849 966,778 Common stock subject to repurchase 116,674 — Convertible preferred stock 252,817 252,818 Redeemable convertible preferred stock 17,328,059 17,236,784 Warrants for preferred stock 885,201 984,529 Total potential dilutive shares 21,877,600 19,440,909 In future periods, if the Company were to generate net income, it would allocate participating securities a proportional share of the net income, determined by dividing total weighted average participating securities by the sum of the total weighted average common shares and participating securities (the two-class method). The Company’s redeemable convertible preferred stock participate in any dividends declared by the Company and are therefore considered to be participating securities. Participating securities have the effect of diluting both basic and diluted earnings per share during periods of income. To date, the Company has only incurred net losses and has not allocated any loss to participating securities because the preferred stockholders have no contractual obligation to share in the losses of the Company. The Company computes diluted loss per common share after giving consideration to the dilutive effect of stock options, warrants and non-vested stock that are outstanding during the period, except where such non-participating securities would be anti-dilutive.

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2015
Fair Value Disclosures [Abstract]
Fair Value Measurements	4. Fair Value Measurements The Company measures and reports its cash equivalents, restricted cash, short-term investments and preferred stock warrant liabilities at fair value. The following table sets forth the fair value of the Company’s financial assets and liabilities measured on a recurring basis by level within the fair value hierarchy: June 30, 2015 Level 1 Level 2 Level 3 Total (in thousands) Financial Assets Money market funds $ 15,213 $ — $ — $ 15,213 Restricted money market funds 225 — — 225 Short-term investments — 10,028 — 10,028 Total financial assets $ 15,438 $ 10,028 $ — $ 25,466 Financial Liabilities Preferred stock warrant liabilities $ — $ — $ 10,641 $ 10,641 December 31, 2014 Level 1 Level 2 Level 3 Total (in thousands) Financial Assets Money market funds $ 27,847 $ — $ — $ 27,847 Restricted money market funds 75 — — 75 Short-term investments — 10,010 — 10,010 Total financial assets $ 27,922 $ 10,010 $ — $ 37,932 Financial Liabilities Preferred stock warrant liabilities $ — $ — $ 1,810 $ 1,810 Money market funds are measured at fair value on a recurring basis using quoted prices and are classified as a Level 1 input. The short-term investments contain observable inputs. Accordingly, the carrying value of this instrument approximates its fair value and is classified as Level 2 inputs. The Company’s preferred stock warrant liabilities contain unobservable inputs that reflect the Company’s own assumptions in which there is little, if any, market activity for at the measurement date. Accordingly, the Company’s warrant liabilities are measured at fair value on a recurring basis using unobservable inputs and are classified as Level 3 inputs. Refer to Note 9 for the valuation technique and assumptions used in estimating the fair value of the warrants. There were no transfers between Levels 1, 2 or 3 for any of the periods presented. For the three and six months ended June 30, 2015, the Company realized a $0 and $10,000 other-than-temporary impairment loss on its short-term investments through other income (expense) in the accompanying condensed consolidated statements of operations. The Company’s Level 3 liabilities consist of a preferred stock warrant liability (see Note 9). The following table provides a roll-forward of the Company’s warrant liabilities measured at fair value on a recurring basis using unobservable inputs (in thousands): Balance as of December 31, 2014 $ 1,810 Fair value of preferred stock warrants exercised (1,125 ) Change in fair value of preferred stock warrants 9,956 Balance as of June 30, 2015 $ 10,641 The preferred stock warrant liabilities will increase or decrease each period based on fluctuations of the fair value of the underlying preferred stock. The change in the fair value of preferred stock warrants for each period is recognized as a gain or loss in the condensed consolidated statements of operations.

Balance Sheet Components

Balance Sheet Components	6 Months Ended
	Jun. 30, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Balance Sheet Components	5. Balance Sheet Components Cash and Cash Equivalents Cash and cash equivalents consist of the following: June 30, 2015 December 31, 2014 (in thousands) Cash $ 587 $ 1,307 Cash equivalents: Money market accounts 15,213 27,847 Total cash and cash equivalents $ 15,800 $ 29,154 Prepaid Expenses and Other Current Assets Prepaid expenses and other current assets consist of the following: June 30, 2015 December 31, 2014 (in thousands) Prepaid research and development project costs $ 414 $ 515 Other 368 46 Total prepaid expenses and other current assets $ 782 $ 561 Property and Equipment, net Property and equipment, net consists of the following: June 30, 2015 December 31, 2014 (in thousands) Computer equipment $ 140 $ 56 Software 11 9 Lab equipment 224 163 Leasehold improvements 75 — Property and equipment, gross 450 228 Less: accumulated depreciation (53 ) (14 ) Total property and equipment, net $ 397 $ 214 Depreciation and amortization related to the Company’s property and equipment was $26,000 and $39,000 for the three and six months ended June 30, 2015 and was insignificant and $1,000 for the three and six months ended June 30, 2014. Other Assets Other assets consist of the following: June 30, 2015 December 31, 2014 (in thousands) Deferred offering costs $ 3,053 $ 549 Restricted cash 200 75 Deferred tax assets 3 2 Total other assets $ 3,256 $ 626 Accrued Liabilities Accrued liabilities consist of the following: June 30, 2015 December 31, 2014 (in thousands) Accrued offering costs $ 615 $ — Accrued employee related costs 572 759 Accrued research and development costs 686 526 Accrued professional fees 408 140 Other 23 48 Total accrued liabilities $ 2,304 $ 1,473

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	6. Commitments and Contingencies License Agreements In March 2007, the Company entered into an exclusive license agreement with Novosom AG (Novosom) to use certain patented LNP delivery technology for any of its DNAi drug candidates that target a region of the BCL2 gene (the Novosom License Agreement). In July 2010, the Novosom License Agreement was acquired by Marina Biotech, Inc. (Marina), but Novosom retained the right to receive all payments due from the Company under the Novosom License Agreement. In March 2012, the Company and Marina entered into another exclusive license agreement (the Marina License Agreement) for the use of certain of Marina’s patented delivery technology, including LNP technology, for any of the Company’s current or future DNAi product candidates that target any gene. In exchange for this exclusive right, the Company paid Marina an upfront payment of $0.3 million in 2012 to be applied to the first DNAi product candidate under this agreement. The Company will be required to pay Marina milestone payments of up to an aggregate of $14.5 million for each DNAi product candidate, other than PNT2258, upon successful completion of certain clinical and regulatory milestone events relating to each DNAi product candidate identified in the Marina License Agreement. In addition, for DNAi product candidates other than PNT2258, the Company is required to pay Marina a low single-digit royalty on net sales. In May 2013, the Company issued Novosom 2,108,870 shares of common stock with a fair market value of $0.1 million in settlement of the first milestone payment. Pursuant to the terms of the Novosom License Agreement, additional shares may have been issued if certain dilution events occurred through December 31, 2014. The Company evaluated the need to accrue an expense related to the future potential issuance of shares at December 31, 2013 and 2014, but determined that each of the terms requiring additional issuances was not likely to occur and thus the expense was not recorded. The dilution provisions expired on December 31, 2014. In April 2014, the Company entered into a Second License Amendment and Consent to Termination Agreement with Marina pursuant to which the Novosom License Agreement (which had been transferred to Marina by Novosom in July 2010) was terminated and the obligations previously set forth in the Novosom License Agreement were restated in the Marina License Agreement. In connection therewith, in April 2014, the Company also entered into a License Payment Agreement with Novosom under which the Company agreed to pay Novosom $11.0 million in cash upon the closing of a minimum $35.0 million financing. Also, the Company agreed to pay Novosom a $3.0 million milestone payment within 30 days of regulatory authority approval of PNT2258. Upon Novosom’s receipt of the cash payment of $11.0 million, all financial obligations of the Company to Novosom were terminated, other than the aforementioned milestone payment, historic manufacturing costs and a low-single digit royalty payment on net sales of PNT2258. The Company made the $11.0 million payment to Novosom in April 2014, upon the closing of the Series D redeemable convertible preferred stock financing and a payment of $0.1 million in July 2014 settling the obligation for the historic manufacturing costs. The April 2014 Second License Amendment and Consent to Termination Agreement serves as the second amendment to the Marina License Agreement. As of June 30, 2015, the Company has not accrued the $3.0 million milestone payment to Novosom as regulatory authority approval is not probable of occurring. As of June 30, 2015, the Company has not identified any product candidates that would pertain to the Marina License Agreement. Therefore, there is currently no potential expense or payment due under the Marina License Agreement. Lease Agreements The Company leases its Michigan facility under a short-term operating lease with a term of less than a year that provides for a fixed monthly rent for the term of the lease and also provides for certain rent adjustments covering the expenses and taxes of the facility. In February 2015, the Company entered into an operating lease agreement to sublease office space in Vancouver, Canada. The operating lease agreement expires on February 27, 2018. Under the terms of the agreement, the Company issued a Canadian Dollar $50,000 letter of credit to the sublessor on closing, which is collateralized by a restricted deposit of $50,000. As of June 30, 2015, the aggregate future non-cancelable minimum lease payments associated with this operating lease (based on the daily average exchange rate on June 30, 2015 quoted by the Bank of Canada) are as follows: Years Ending December 31: Operating Leases (in thousands) 2015 (remainder) $ 133 2016 319 2017 319 2018 53 Total $ 824 The total rent expense for all operating leases was $0.1 million for the three and six months ended June 30, 2015 and was $14,000 and $22,000 for the three and six months ended June 30, 2014. Contract Research Organization Obligations As of June 30, 2015, the aggregate future minimum payments associated with agreements the Company entered into with contract research organizations are as follows: Years Ending December 31: Contract Research (in thousands) 2015 (remainder) $ 2,025 2016 5,303 2017 4,914 2018 255 Total $ 12,497 For the three and six months ended June 30, 2015, total payments made to the contract research organization related to these obligations were $0.6 million and $1.6 million. Cumulative Dividends Holders of the Series B, B-1, C and D redeemable convertible preferred stock are entitled to receive cumulative accruing dividends at a rate of 8.0% per year of the original issuance price of the redeemable convertible preferred stock. The accruing dividends shall accrue from day to day, whether or not declared, and shall be cumulative. The accruing dividends shall be deemed declared annually and payable upon the earliest to occur of (i) the date determined by the Board of Directors, (ii) the liquidation of the Company (including a Deemed Liquidation Event) and (iii) the conversion or redemption of at least a majority of the outstanding shares of the Series B, B-1, C and D redeemable convertible preferred stock. Since the dividends are payable upon a contingent event, the Company has not recorded them as a liability in the accompanying condensed consolidated financial statements for any of the periods presented. At June 30, 2015, cumulative unpaid accruing dividends in arrears totaled $18.5 million and consisted of $9.3 million for the Series B, $1.7 million for the Series B-1, $1.6 million for the Series C and $5.9 million for the Series D redeemable convertible preferred stock. At December 31, 2014, cumulative unpaid accruing dividends in arrears totaled $14.4 million and consisted of $8.4 million for the Series-B, $1.5 million for the Series B-1, $1.1 for the Series C and $3.4 million for the Series D redeemable convertible preferred stock. As discussed in Note 8, the dividend rights for the Series C and Series D redeemable convertible preferred stock were amended in June 2015.

Common Stock Reserved for Issua

Common Stock Reserved for Issuance	6 Months Ended
	Jun. 30, 2015
Equity [Abstract]
Common Stock Reserved for Issuance	7. Common Stock Reserved for Issuance The Company is required to reserve and keep available out of its authorized but unissued shares of common stock a number of shares sufficient to effect the conversion of all outstanding shares of preferred stock (and preferred stock warrants), plus options granted and available for grant under the incentive plans. June 30, 2015 December 31, Conversion of outstanding Series A convertible preferred stock 252,817 252,817 Conversion of outstanding Series B redeemable convertible preferred stock 1,947,354 1,947,354 Conversion of outstanding Series B-1 redeemable convertible preferred stock 1,478,328 1,392,300 Conversion of outstanding Series C redeemable convertible preferred stock 2,493,017 2,487,770 Conversion of outstanding Series D redeemable convertible preferred stock 11,409,360 11,409,360 Outstanding preferred stock warrants 885,201 976,492 Outstanding and issued stock options 3,294,849 2,138,096 Shares reserved for future option grants 365,535 1,550,101 Total common stock reserved for issuance 22,126,461 22,154,290

Convertible and Redeemable Conv

Convertible and Redeemable Convertible Preferred Stock	6 Months Ended
	Jun. 30, 2015
Text Block [Abstract]
Convertible and Redeemable Convertible Preferred Stock	8. Convertible and Redeemable Convertible Preferred Stock During the six months ended June 30, 2015, the Company issued 86,028 shares of Series B-1 redeemable convertible preferred stock and 5,247 shares of Series C redeemable convertible preferred stock upon the exercise of the Company’s Series B-1 and Series C preferred stock warrants. The convertible and redeemable convertible preferred stock consists of the following: June 30, 2015 Shares Shares Issued and Outstanding Net Carrying Liquidation Price Per Aggregate Redemption (in thousands, except share and per share data) Convertible Preferred Stock: Series A 1,843,894 224,564 $ 2,543 $ 11.324 $ 2,543 $ — Redeemable Convertible Preferred Stock: Series B 13,134,880 1,752,634 42,688 12.755 22,355 42,688 Series B-1 16,283,343 1,478,328 24,596 3.742 5,532 24,596 Series C 19,812,349 2,493,017 41,493 5.865 14,621 41,493 Series D 85,000,000 11,409,360 186,332 5.728 65,359 186,332 Total redeemable convertible preferred stock 134,230,572 17,133,339 $ 295,109 $ 107,867 $ 295,109 Total preferred stock 136,074,466 17,357,903 $ 297,652 $ 110,410 $ 295,109 December 31, 2014 Shares Shares Issued and Outstanding Net Carrying Liquidation Price Per Aggregate Redemption (in thousands, except share and per share data) Convertible Preferred Stock: Series A 1,843,894 224,564 $ 2,543 $ 11.324 $ 2,543 $ — Redeemable Convertible Preferred Stock: Series B 13,134,880 1,752,634 19,504 12.268 21,502 19,504 Series B-1 16,122,618 1,392,300 6,979 3.656 5,091 6,979 Series C 19,812,349 2,487,770 21,052 5.642 14,035 21,052 Series D 85,000,000 11,409,360 94,297 5.510 62,865 94,297 Total redeemable convertible preferred stock 134,069,847 17,042,064 $ 141,832 $ 103,493 $ 141,832 Total preferred stock 135,913,741 17,266,628 $ 144,375 $ 106,036 $ 141,832 On issuance, the Company’s convertible and redeemable convertible preferred stock is recorded at fair value or the amount of allocated proceeds, net of issuance costs. The Company’s Series A convertible preferred stock (the “convertible preferred stock”) is classified outside of stockholders’ deficit because, in the event of certain “liquidation events” that are not solely within the Company’s control (including merger, acquisition, or sale of all or substantially all of the Company’s assets), the shares would become redeemable at the option of the holders. As of June 30, 2015 and December 31, 2014, the carrying value of the convertible preferred stock was the liquidation value. The Company’s Series B, B-1, C and D redeemable convertible preferred stock (collectively, the “redeemable convertible preferred stock”) is classified outside of stockholders’ deficit because the stocks contain redemption features that commence at any time on or after December 31, 2018 at the election of the Series B, B-1, C and D redeemable convertible preferred stockholders. The Company adjusts the carrying amount of the redeemable convertible preferred stock to equal the redemption value at the end of each reporting period. Due to the absence of retained earnings, adjustments to redemption value are recorded against additional paid-in capital, if any, and then to accumulated deficit. The following table sets forth the total adjustment to redemption value of each series of redeemable convertible preferred stock recognized during the following period: Six Months Redeemable Convertible Preferred Stock Series B $ 23,184 Series B-1 16,307 Series C 20,359 Series D 92,035 Total adjustment to redemption value on redeemable convertible preferred stock $ 151,885 As the redemption value for the redeemable convertible preferred stock may at times be based on fair market value at each reporting date, the Company determines the fair value of the redeemable convertible preferred stock using a combination of the OPM and/or the PWERM models and as of June 30, 2015, the IPO price of the Company’s common stock. The following assumptions were used in the OPM: As of June 30, As of December 31, Expected term (in years) 0.9 1.2 – 2.5 Expected volatility 66 % 69 – 86% Risk-free interest rate 0.2 % 0.3 – 0.6% Expected dividend rate — % — % Amendment to Dividend Rights On June 11, 2015, the Company’s stockholders approved an amendment to the Company’s certificate of incorporation to modify the terms of the cumulative accruing dividends on the outstanding shares of the Company’s Series C and Series D redeemable convertible preferred stock. Under the terms of the amended certificate of incorporation, upon conversion of the Company’s redeemable convertible preferred stock into common stock in connection with an IPO, the Company shall pay 50% of the then accrued but unpaid accruing dividends on shares of the Series C and Series D redeemable convertible preferred stock in shares of the Company’s common stock instead of payment in cash and the remaining 50% of the then accrued but unpaid accruing dividends shall be forfeited. The settlement of the accrued but unpaid accruing dividends in shares of common stock will be at the original issue price of the Series C and Series D redeemable convertible preferred stock of $5.215 per share. The terms of the dividends payable on the Series B and Series B-1 preferred stock were not modified. Cumulative Dividends As of June 30, 2015, cumulative unpaid accruing dividends in arrears totaled $18.5 million and consisted of $9.3 million for the Series B, $1.7 million for the Series B-1, $1.6 million for the Series C and $5.9 million for the Series D redeemable convertible preferred stock. If an IPO had occurred as of June 30, 2015, the Company would have paid accruing dividends in the aggregate amount of $5.5 million to the Series B and B-1 redeemable convertible preferred stockholders, consisting of $4.6 million for the Series B and $0.9 million for the Series B-1 redeemable convertible preferred stockholders, and would have issued an aggregate of 716,958 shares of common stock to the Series C and D redeemable convertible preferred stockholders, consisting of 155,273 shares to the Series C and 561,685 to the Series D redeemable convertible preferred stockholders, under the terms of the June 11, 2015 amended certificate of incorporation. Amendment to Redemption Rights On June 11, 2015, the Company and the Michigan Strategic Fund (MSF) and the Michigan Economic Development Corporation (MEDC) entered into an amendment to equity conversion agreements previously entered into by the parties. The amendment modified the terms of the equity conversion agreements that permit the MSF and MEDC to require the Company to repurchase shares of their preferred stock in certain circumstances, referred to as “put options.” The modification to the put options (i) suspended the exercisability of the put options during the period prior to and through the completion of the IPO and (ii) further provided that the put options would expire upon the completion of the IPO. However, in the event the IPO had not been completed by December 31, 2015 or was abandoned by the Company prior to that date, the MSF and MEDC would have the right to exercise the put options for a period of 120 days following the earlier to occur of such dates.

Preferred Stock Warrants

Preferred Stock Warrants	6 Months Ended
	Jun. 30, 2015
Text Block [Abstract]
Preferred Stock Warrants	9. Preferred Stock Warrants The Company classifies its preferred stock warrants as liabilities on the accompanying condensed consolidated balance sheets. As of June 30, 2015 and December 31, 2014, the preferred stock warrant liabilities were $10.6 million and $1.8 million. The key terms of the redeemable convertible preferred stock warrants are summarized in the following table: Warrants Outstanding Warrants Outstanding 2015 Warrants Exercise Price Expiration Series B preferred stock warrants 10,414 10,414 $ 7.45 July 31, 2018 Series B-1 preferred stock warrants 43,969 47,060 7.45 June 30, 2018 Series B-1 preferred stock warrants 663,343 746,295 2.6075 Various dates in 2016 – 2021 Series C preferred stock warrants 166,318 171,566 5.215 Various dates in 2022 – 2023 Total preferred stock warrants 884,044 975,335 The warrants are immediately exercisable in whole or in part over the term of the warrants. In the event of an IPO, all of the Company’s outstanding preferred stock warrants expire unless the warrant holders elect to exercise them prior to the IPO. During the year ended December 31, 2014, no warrants were exercised. During the three and six months ended June 30, 2015, 3,079 of the Series B-1 warrants were exercised at an exercise price of $7.45 per share, 82,949 of the Series B-1 warrants were exercised at an exercise price of $2.6075 per share and 5,247 of the Series C warrants were exercised at an exercise price of $5.215 per share, resulting in total aggregate cash proceeds to the Company of $0.3 million. Upon exercise of warrants, the fair value of the warrant liability of $1.1 million was reclassified to redeemable convertible preferred stock. Determination of Fair Value At each reporting date, the Company remeasures the preferred stock warrants to fair value using the OPM and/or the PWERM models with the following assumptions used in the OPM: As of June 30, As of December 31, Expected term (in years) 0.9 1.2 – 2.5 Expected volatility 66 % 69 – 86% Risk-free interest rate 0.2 % 0.3 – 0.6% Expected dividend rate — % — % Discount for lack of marketability 11.3 % 19.5 – 24.3% The assumptions used in calculating the estimated fair market value at each reporting period represent the Company’s best estimate, however inherent uncertainties are involved. As a result, if factors or assumptions change the warrant liability, the estimated fair value could be materially different. The Company estimates the volatility of its stock based on comparable peer public companies historical volatility. The risk-free interest rate is based on the U.S. Treasury zero-coupon bond. The expected term applied in the OPM considers both the probabilities of failure and success of the Company. Cumulative dividends associated with preferred stock are calculated as of the accrual start date of each security to the OPM maturity date.

Stock-Based Compensation

Stock-Based Compensation	6 Months Ended
	Jun. 30, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	10. Stock-Based Compensation In the accompanying condensed consolidated statement of operations, the Company recognized stock-based compensation expense for its employees and non-employees as follows: Three Months Ended June 30, Six Months Ended June 30, 2015 2014 2015 2014 (in thousands) Research and development $ 225 $ 9 $ 299 $ 18 General and administrative 195 50 301 63 Total stock-based compensation $ 420 $ 59 $ 600 $ 81 Determination of Fair Value The estimated grant-date fair value of all the Company’s stock-based awards was calculated using the Black-Scholes option pricing model, based on assumptions as follows: Three Months Ended June 30, Six Months Ended June 30, 2015 2014 2015 2014 Expected term (in years) 5.2 – 10.0 5.7 6.0 – 10.0 5.0 – 5.7 Expected volatility 75 – 79% 83 % 75 – 81% 81 – 83% Risk-free interest rate 1.7% 1.6 % 1.5 – 1.7% 1.5 – 1.7% Expected dividend rate — % — % — % — % Equity Incentive Plans 2008 Plan On June 24, 2008, the Company’s board of directors approved the 2008 Stock Plan (the “2008 Plan”) for issuance of up to 308,725 shares of common stock to be administered by the board of directors or a committee appointed by them. Amendments to the plan were approved by the board of directors to increase the authorized shares to 1,580,537 at December 31, 2013 and 4,802,013 shares as of December 31, 2014. The 2008 Plan allows for the granting of Incentive Stock Options (ISO), nonqualified stock options and stock purchase rights. The term of the plan is for the later of 10 years from the effective date of the 2008 Plan or the earlier of the most recent board or stockholder approval of an increase in the number of shares reserved for issuance under the 2008 Plan. 2005 Stock Plan As of June 30, 2015, there were 940 awards issued and outstanding under the Company’s 2005 Plan (the “2005 Plan”). The terms of the 2005 Plan are similar to those of the 2008 Plan. On August 20, 2008, the board of directors canceled all shares available under the 2005 Plan with the intention to not issue any more shares under the plan. A summary of activity under the 2005 Plan and 2008 Plan and related information is as follows: Options Outstanding Shares Available for Grant Number of Shares Weighted- Weighted- Aggregate Intrinsic (in thousands) Outstanding — December 31, 2014 1,550,101 2,138,096 $ 0.91 9.29 $ 3,153 Awards authorized — — Options granted (1,184,566 ) 1,184,566 5.62 Options exercised — (27,813 ) 1.00 Options cancelled — — — Outstanding — June 30, 2015 365,535 3,294,849 $ 2.60 9.19 $ 40,849 Exercisable — June 30, 2015 2,115,209 $ 0.92 8.81 $ 29,783 Vested and expected to vest — June 30, 2015 2,983,562 $ 2.71 9.20 $ 36,665 The weighted-average grant date fair values of options granted during the three and six months ended June 30, 2015 was $12.03 and $4.35 per share and during the three and six months ended June 30, 2014 was $0.41 per share. The aggregate intrinsic value of options exercised was $0 and $0.4 million for the three and six months ended June 30, 2015 and $16,000 and $0.1 million for the three and six months ended June 30, 2014. The total grant date fair value of options vested for the three and six months ended June 30, 2015 was $0.1 million and $0.2 million and during the three and six months ended June 30, 2014 was $0.1 million. As of June 30, 2015, total unrecognized stock-based compensation related to unvested stock options was $12.8 million, net of estimated forfeitures, which the Company expects to recognize over a remaining weighted-average period of 1.92 years. Certain stock options are subject to occurrence of a performance condition. Performance-Based Stock Option Grant During the year ended December 31, 2014, the Company granted options to purchase 217,305 shares of common stock to an executive officer which contains both performance-based and service-based vesting criteria. Stock-based compensation associated with these performance-based stock options is recognized if the performance condition is achieved. On January 24, 2015, the Company amended the terms of the performance-based stock options to extend the date of the performance-based milestone. As of June 30, 2015, management had concluded that the performance-based milestone was not probable of achievement. As such, no stock-based compensation was recorded during the three and six months ended June 30, 2015 related to these options. If the performance condition had been achieved as of June 30, 2015, the Company would have recorded $0.1 million in additional stock-based compensation related to these stock options. Liability for Early Exercise of Stock Options The 2008 Plan allows for the granting of options that may be exercised before the options have vested. In December 2014, an executive officer early exercised 103,252 stock options. In February 2015, an executive officer early exercised 13,422 stock options. On early exercise, the awards became subject to a restricted stock agreement. The shares of restricted stock granted upon early exercise of the options are subject to the same vesting provisions as the original stock option awards. Shares issued as a result of early exercise that have not vested are subject to repurchase by the Company upon termination of the purchaser’s employment or services, at the price paid by the purchaser, and are not deemed to be issued for accounting purposes until those related shares vest. Accordingly, the Company has recorded the exercise proceeds of $0.1 million from the early exercise as a long-term liability in the accompanying condensed consolidated balance sheet as of June 30, 2015 and December 31, 2014. The long-term liability will be reclassified into common stock and additional paid-in capital as the shares vest and the repurchase right has lapses. As of June 30, 2015 and December 31, 2014, 116,674 and 103,252 shares held by the employee remain unvested and subject to repurchase with an aggregate price of $0.1 million.

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2015
Income Tax Disclosure [Abstract]
Income Taxes	11. Income Taxes The Company did not record a provision for federal income taxes for the three and six months ended June 30, 2015 because it expects to generate a loss for the year ended December 31, 2015. The income tax expense of $1,000 and $11,000 for the three and six months ended June 30, 2015 represents foreign taxes. The Company’s deferred tax assets continue to be offset by a valuation allowance.

Subsequent Events

Subsequent Events	6 Months Ended
	Jun. 30, 2015
Subsequent Events [Abstract]
Subsequent Events	12. Subsequent Events Exercise of Preferred Stock Warrants From July 1 to July 10, 2015, 28,699 of the Company’s Series B-1 warrants were exercised at an exercise price of $7.45 per share, 329,559 of the Series B-1 warrants were exercised at an exercise price of $2.6075 per share and 32,138 of the Series C warrants were exercised at an exercise price of $5.215 per share, resulting in total aggregate cash proceeds to the Company of $1.2 million. See Note 9. Initial Public Offering In connection with the IPO discussed in Note 1, the following events occurred: • The Company is obligated to pay $5.5 million in cumulative accrued dividends in cash to the Company’s Series B and Series B-1 redeemable convertible preferred stockholders. See Note 8. • An aggregate of 750,946 shares of common stock were issued to the Company’s Series C and Series D redeemable convertible preferred stockholders, in payment of $3.9 million of cumulative accrued dividends. See Note 8. • An aggregate of 390,680 shares of common stock were issued on the net exercise of 493,648 preferred stock warrants at the IPO price of $17 per share. See Note 9. • The 2015 Plan and the 2015 Employee Stock Purchase Plan, as described below, were adopted. • An aggregate of 365,535 shares of common stock reserved but not issued under the 2008 Plan became available for grant under the 2015 Plan. • The Company recorded $0.1 million in additional stock-based compensation related to the achievement of a performance-based stock option grant to an executive officer. See Note 10. • The Company filed its amended and restated certificate of incorporation on July 21, 2015, authorizing 500,000,000 shares of common stock and 10,000,000 shares of preferred stock. Adoption of 2015 Equity Incentive Plan On July 14, 2015, the 2015 Equity Incentive Plan (the “2015 Plan”) became effective. The 2015 Plan will serve as a successor to the Company’s 2008 Stock Plan. The 2015 Plan permits the award of stock options, restricted stock awards, stock appreciation rights, restricted stock units, performance awards, cash awards and stock bonuses. The Company reserved 3,400,000 shares of common stock for issuance under the 2015 Plan, plus the remaining reserved and unissued shares under the 2008 plan on the effective date of the 2015 Plan. Adoption of 2015 Employee Stock Purchase Plan On July 15, 2015, the 2015 Employee Stock Purchase Plan was adopted in order to enable eligible employees to purchase shares of the Company’s common stock at a discount. Purchases will be accomplished through participation in discrete offering periods. The 2015 Employee Stock Purchase Plan will not become effective until such time as the Compensation Committee determines in the future. The Company initially reserved 700,000 shares of common stock for issuance under the 2015 Employee Stock Purchase Plan. The aggregate number of shares issued over the term of the 2015 Employee Stock Purchase Plan will not exceed 3,400,000 shares of common stock.

Summary Of Significant Accoun19

Summary Of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2015
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The condensed consolidated balance sheet as of June 30, 2015, the condensed consolidated statements of operations and comprehensive loss for the three and six months ended June 30, 2015 and 2014 and the condensed consolidated statements of cash flows for the six months ended June 30, 2015 and 2014 and the condensed consolidated statements of convertible and redeemable convertible preferred stock and stockholders’ deficit for the six months ended June 30, 2015 are unaudited. The unaudited condensed consolidated financial statements have been prepared on the same basis as the annual consolidated financial statements and reflect, in the opinion of management, all adjustments of a normal and recurring nature that are necessary for the fair presentation of the Company’s condensed consolidated financial statements included in this report. The condensed consolidated financial data disclosed in these notes to the condensed consolidated financial statements related to the three and six month periods are also unaudited. The condensed consolidated results of operations for the three and six months ended June 30, 2015 are not necessarily indicative of the results to be expected for the year ending December 31, 2015, or for any other future annual or interim period. The consolidated balance sheet as of December 31, 2014 included herein was derived from the audited consolidated financial statements as of that date. These condensed consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements included in the prospectus dated July 15, 2015, filed with the SEC pursuant to Rule 424 promulgated under the Securities Act of 1933, as amended.
Use of Estimates	Use of Estimates The preparation of the condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements and the reported amounts of expense during the reporting period. Significant estimates and assumptions made in the accompanying condensed consolidated financial statements include, but are not limited to the fair value of common stock, the fair value of preferred stock, the fair value of preferred stock warrant liabilities, the fair value of stock options, recoverability of the Company’s net deferred tax assets, and related valuation allowance and certain accruals. The Company evaluates its estimates and assumptions on an ongoing basis using historical experience and other factors and adjusts those estimates and assumptions when facts and circumstances dictate. Actual results could materially differ from those estimates.
Foreign Currency	Foreign Currency The functional currency of the Company’s foreign subsidiary is the U.S. Dollar. Transactions denominated in currencies other than the functional currency are remeasured to the functional currency at the average exchange rate in effect during the period. At the end of each reporting period, monetary assets and liabilities are remeasured to the functional currency using exchange rates in effect at the balance sheet date. Non-monetary assets and liabilities are remeasured at historical exchange rates. Gains and losses related to remeasurement are recorded in other income (expense) in the condensed consolidated statements of operations.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments with an original maturity of three months or less from the date or purchase to be cash equivalents. Cash and cash equivalents consist primarily of funds invested in readily available checking and savings accounts and highly liquid investments in money market funds.
Restricted Cash	Restricted Cash Restricted cash represents collateral for a corporate credit card facility and a security deposit required for a facility lease. Restricted cash consists of funds invested in a money market fund. As of June 30, 2015, the current portion of restricted cash of $25,000 is included in prepaid expenses and other current assets and the long-term portion of restricted cash of $0.2 million is included in other assets in the accompanying condensed consolidated balance sheets.
Investments	Investments The Company determines the appropriate designation of its investments as “trading,” “available-for-sale” or “held-to-maturity” based on management’s intent at the time of purchase and reevaluates such designation at each reporting date. As of June 30, 2015 and December 31, 2014, all of the Company’s short-term investments were designated as available-for-sale. Unrealized gains and losses, if any, are reported as a separate component of stockholders’ deficit, except for unrealized losses determined to be other-than-temporary which are recorded in other income (expense) in the accompanying condensed consolidated statements of operations. The Company determines any realized gains or losses on the sale of any investments on a specific identification method and records such gains and losses as a component of other income (expense) in the accompanying condensed consolidated statements of operations. The Company evaluates its short-term investments periodically for possible other-than-temporary impairment. A decline in fair value below the amortized cost of the investment is considered other-than-temporary impairment if the Company has the intent to sell the investment or it is more likely than not that the Company will be required to sell the investment before recovery of the entire amortized cost basis. In those instances, an impairment charge equal to the difference between the fair value and the amortized cost basis is recognized in other income (expense). Regardless of the Company’s intent or requirement to sell an investment, impairment is considered other-than-temporary if the Company does not expect to recover the entire amortized cost basis. Investments with original maturities beyond three months at the date of purchase and which mature at, or less than twelve months from, the balance sheet date are classified as current. Investments with a maturity beyond twelve months from the condensed consolidated balance sheet date are classified as long-term. As of June 30, 2015, the Company’s short-term investments were classified as current assets.
Concentrations of Credit Risk	Concentrations of Credit Risk Financial instruments that subject the Company to significant concentrations of credit risk consist of cash, cash equivalents, restricted cash and short-term investments. All of the Company’s cash, cash equivalents, restricted cash and short-term investments are held at financial institutions in the United States and Canada that management believes to be of high credit quality. Deposits held in the United States with these financial institutions exceed federally insured limits. The primary focus of the Company’s investment strategy is to preserve capital and meet liquidity requirements. The Company’s investment policy addresses the level of credit exposure by limiting the concentration in any one corporate issuer or sector and establishing a minimum allowable credit rating.
Comprehensive Income (Loss)	Comprehensive Income (Loss) The Company had no components of comprehensive income (loss) other than net loss for all periods presented.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The Company’s cash and cash equivalents, restricted cash, short-term investments, other current assets, accounts payable, and accrued liabilities approximate their fair value at June 30, 2015 and December 31, 2014, due to their short duration. The short-term investment maintains observable inputs, thus the carrying value of this instrument is carried at fair value and unrealized gains and losses, if any, are reported as a separate component of stockholders’ deficit. The Company’s preferred stock warrant liabilities contain unobservable inputs that reflect the Company’s own assumptions in which there is little, if any, market activity at the measurement date, thus the Company’s warrant liabilities are measured at fair value on a recurring basis using unobservable inputs. The Company utilizes valuation techniques that maximize the use of observable inputs and minimize the use of unobservable inputs to the extent possible. The Company determines the fair value of its financial instruments based on assumptions that market participants would use in pricing an asset or liability in the principal or most advantageous market. When considering market participant assumptions in fair value measurements, the following fair value hierarchy distinguishes between observable and unobservable inputs, which are categorized in one of the following levels: Level 1 Level 2 Level 3
Property and Equipment, Net	Property and Equipment, Net Property and equipment, net are stated at cost, less accumulated depreciation and amortization. Depreciation and amortization on property and equipment, excluding leasehold improvements, is computed using the straight-line Leasehold improvements are amortized on a straight-line basis over the shorter of the estimated useful lives of the assets or the remaining lease term. Amortization on leasehold improvements are amortized over the term of the related property lease, for a period of three years.
Deferred Offering Costs	Deferred Offering Costs Deferred offering costs, consisting of legal, accounting and filing fees relating to an IPO, have been capitalized. The deferred offering costs will be offset against offering proceeds upon the completion of the offering. As of June 30, 2015 and December 31, 2014, $3.1 million and $0.5 million of deferred offering costs have been capitalized, which is included in other long-term assets in the condensed consolidated balance sheets.
Preferred Stock Warrant Liabilities	Preferred Stock Warrant Liabilities The Company accounts for its warrants issued in connection with its various financing transactions based upon the characteristics and provisions of the instrument. Warrants classified as derivative liabilities are recorded on the Company’s condensed consolidated balance sheets at their fair value on the date of issuance and remeasured to fair value on each subsequent reporting period, with the changes in fair value recognized as a component of other income (expense), net in the accompanying condensed consolidated statements of operations. The Company will continue to adjust the liability for changes in the fair value of these warrants until the earlier of the exercise of the warrants, the expiration of the warrants, or until such time as the warrants are no longer to be considered derivative instruments. On the completion of an IPO (which occurred on July 21, 2015, as discussed in Note 1), the liability on the preferred stock warrants will be reclassified to additional paid-in capital in stockholders’ deficit. The Company estimates the fair value of these liabilities using an Option Pricing Model (OPM) or a Probability Weighted Expected Return Method (PWERM) and using assumptions that are based on the individual characteristics of the warrants or instruments on the valuation date, as well as assumptions for expected term, expected volatility and risk-free interest rate.
Research and Development Costs	Research and Development Costs Research and development costs are expensed as incurred. The Company accounts for nonrefundable advance payments for goods and services that will be used in future research and development activities as expenses when the goods have been received or when the service has been performed rather than when the payment is made. Depending on the timing of payments to service providers of research and development costs, the Company recognizes prepaid expenses or accrued expenses related to these costs. These prepaid or accrued expenses are based on management’s estimates of the work performed under service agreements and milestones achieved. Research and development costs include fees incurred in connection with license agreements, compensation and other related costs for employees engaged in research and development, costs associated with preclinical studies and trials, regulatory activities, manufacturing activities to support clinical activities, license fees, fees paid to external service providers that conduct certain research and development, clinical, and manufacturing activities on behalf of the Company and an allocation of overhead expenses.
Stock-Based Compensation	Stock-Based Compensation The Company accounts for share-based payments at fair value, which is measured using the Black-Scholes option-pricing model. For share-based awards that vest subject to the satisfaction of a service requirement, the fair value measurement date for employee stock-based compensation awards is the date of grant and the expense is recognized on a straight line basis, over the vesting period. For share-based awards that vest subject to the satisfaction of a service requirement and a performance component, the fair value measurement date is the date of grant and is recognized over the requisite service period as achievement of the performance objective becomes probable. No expense has been recorded to date relating to this grant as the performance condition hasn’t been achieved. Stock-based compensation arrangements with nonemployees are recognized at the grant date and remeasured to fair value at each reporting period. The expense is recognized over the vesting period which is generally the service period.
Income Taxes	Income Taxes The Company uses the asset and liability method of accounting for income taxes. Under this method, deferred tax assets and liabilities are determined based on the differences between the financial reporting and the tax bases of assets and liabilities and are measured using the enacted tax rates and laws that will be in effect when the differences are expected to reverse. Management makes an assessment of the likelihood that the resulting deferred tax assets will be realized. A valuation allowance is provided when it is more likely than not that some portion or all of a deferred tax asset will not be realized. Due to the Company’s historical operating performance and the recorded cumulative net losses in prior fiscal periods, the net deferred tax assets have been fully offset by a valuation allowance. The Company recognizes uncertain income tax positions at the largest amount that is more likely than not to be sustained upon audit by the relevant taxing authority. An uncertain income tax position will not be recognized if it has less than a 50% likelihood of being sustained. Changes in recognition or measurement are reflected in the period in which judgment occurs. The Company’s policy is to recognize interest and penalties related to the underpayment of income taxes as a component of provision for income taxes.
Segment Information	Segment Information Operating segments are components of an enterprise for which separate financial information is available and is evaluated regularly by the Company’s chief operating decision maker in deciding how to allocate resources and assessing performance. The Company’s chief operating decision maker is its Chief Executive Officer. The Company’s Chief Executive Officer views the Company’s operations and manages its business in one operating segment, which is the business of researching, developing, and commercializing therapies for the treatment of patients with cancer. Accordingly, the Company has a single reporting segment.

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	6 Months Ended
	Jun. 30, 2015
Earnings Per Share [Abstract]
Schedule of Outstanding Shares of Common Stock Equivalents Excluded from Calculation of Diluted Net Loss Per Share Attributable to Common Stockholders	The following outstanding shares of common stock equivalents were excluded from the calculation of diluted net loss per share attributable to common stockholders for the periods presented because including them would have been antidilutive: As of June 30, 2015 2014 Options to purchase common stock 3,294,849 966,778 Common stock subject to repurchase 116,674 — Convertible preferred stock 252,817 252,818 Redeemable convertible preferred stock 17,328,059 17,236,784 Warrants for preferred stock 885,201 984,529 Total potential dilutive shares 21,877,600 19,440,909

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2015
Fair Value Disclosures [Abstract]
Schedule of Fair Value Financial Assets and Liabilities Measured on Recurring Basis	The following table sets forth the fair value of the Company’s financial assets and liabilities measured on a recurring basis by level within the fair value hierarchy: June 30, 2015 Level 1 Level 2 Level 3 Total (in thousands) Financial Assets Money market funds $ 15,213 $ — $ — $ 15,213 Restricted money market funds 225 — — 225 Short-term investments — 10,028 — 10,028 Total financial assets $ 15,438 $ 10,028 $ — $ 25,466 Financial Liabilities Preferred stock warrant liabilities $ — $ — $ 10,641 $ 10,641 December 31, 2014 Level 1 Level 2 Level 3 Total (in thousands) Financial Assets Money market funds $ 27,847 $ — $ — $ 27,847 Restricted money market funds 75 — — 75 Short-term investments — 10,010 — 10,010 Total financial assets $ 27,922 $ 10,010 $ — $ 37,932 Financial Liabilities Preferred stock warrant liabilities $ — $ — $ 1,810 $ 1,810
Summary of Warrant Liabilities Measured at Fair Value on Recurring Basis Using Unobservable Inputs	The following table provides a roll-forward of the Company’s warrant liabilities measured at fair value on a recurring basis using unobservable inputs (in thousands): Balance as of December 31, 2014 $ 1,810 Fair value of preferred stock warrants exercised (1,125 ) Change in fair value of preferred stock warrants 9,956 Balance as of June 30, 2015 $ 10,641

Balance Sheet Components (Table

Balance Sheet Components (Tables)	6 Months Ended
	Jun. 30, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Summary of Cash and Cash Equivalents	Cash and cash equivalents consist of the following: June 30, 2015 December 31, 2014 (in thousands) Cash $ 587 $ 1,307 Cash equivalents: Money market accounts 15,213 27,847 Total cash and cash equivalents $ 15,800 $ 29,154
Summary of Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets consist of the following: June 30, 2015 December 31, 2014 (in thousands) Prepaid research and development project costs $ 414 $ 515 Other 368 46 Total prepaid expenses and other current assets $ 782 $ 561
Summary of Property and Equipment, Net	Property and equipment, net consists of the following: June 30, 2015 December 31, 2014 (in thousands) Computer equipment $ 140 $ 56 Software 11 9 Lab equipment 224 163 Leasehold improvements 75 — Property and equipment, gross 450 228 Less: accumulated depreciation (53 ) (14 ) Total property and equipment, net $ 397 $ 214
Schedule of Other Assets	Other assets consist of the following: June 30, 2015 December 31, 2014 (in thousands) Deferred offering costs $ 3,053 $ 549 Restricted cash 200 75 Deferred tax assets 3 2 Total other assets $ 3,256 $ 626
Summary of Accrued Liabilities	Accrued liabilities consist of the following: June 30, 2015 December 31, 2014 (in thousands) Accrued offering costs $ 615 $ — Accrued employee related costs 572 759 Accrued research and development costs 686 526 Accrued professional fees 408 140 Other 23 48 Total accrued liabilities $ 2,304 $ 1,473

Commitments and Contingencies (

Commitments and Contingencies (Tables)	6 Months Ended
	Jun. 30, 2015
Commitments and Contingencies Disclosure [Abstract]
Schedule of Aggregate Future Non-Cancelable Minimum Lease Payments	As of June 30, 2015, the aggregate future non-cancelable minimum lease payments associated with this operating lease (based on the daily average exchange rate on June 30, 2015 quoted by the Bank of Canada) are as follows: Years Ending December 31: Operating Leases (in thousands) 2015 (remainder) $ 133 2016 319 2017 319 2018 53 Total $ 824
Summary of Aggregate Future Minimum Payments	As of June 30, 2015, the aggregate future minimum payments associated with agreements the Company entered into with contract research organizations are as follows: Years Ending December 31: Contract Research (in thousands) 2015 (remainder) $ 2,025 2016 5,303 2017 4,914 2018 255 Total $ 12,497

Common Stock Reserved for Iss24

Common Stock Reserved for Issuance (Tables)	6 Months Ended
	Jun. 30, 2015
Equity [Abstract]
Schedule of Common Stock Reserved for Issuance	The Company is required to reserve and keep available out of its authorized but unissued shares of common stock a number of shares sufficient to effect the conversion of all outstanding shares of preferred stock (and preferred stock warrants), plus options granted and available for grant under the incentive plans. June 30, 2015 December 31, Conversion of outstanding Series A convertible preferred stock 252,817 252,817 Conversion of outstanding Series B redeemable convertible preferred stock 1,947,354 1,947,354 Conversion of outstanding Series B-1 redeemable convertible preferred stock 1,478,328 1,392,300 Conversion of outstanding Series C redeemable convertible preferred stock 2,493,017 2,487,770 Conversion of outstanding Series D redeemable convertible preferred stock 11,409,360 11,409,360 Outstanding preferred stock warrants 885,201 976,492 Outstanding and issued stock options 3,294,849 2,138,096 Shares reserved for future option grants 365,535 1,550,101 Total common stock reserved for issuance 22,126,461 22,154,290

Convertible and Redeemable Co25

Convertible and Redeemable Convertible Preferred Stock (Tables)	6 Months Ended
	Jun. 30, 2015
Text Block [Abstract]
Components of Convertible and Redeemable Convertible Preferred Stock	The convertible and redeemable convertible preferred stock consists of the following: June 30, 2015 Shares Shares Issued and Outstanding Net Carrying Liquidation Price Per Aggregate Redemption (in thousands, except share and per share data) Convertible Preferred Stock: Series A 1,843,894 224,564 $ 2,543 $ 11.324 $ 2,543 $ — Redeemable Convertible Preferred Stock: Series B 13,134,880 1,752,634 42,688 12.755 22,355 42,688 Series B-1 16,283,343 1,478,328 24,596 3.742 5,532 24,596 Series C 19,812,349 2,493,017 41,493 5.865 14,621 41,493 Series D 85,000,000 11,409,360 186,332 5.728 65,359 186,332 Total redeemable convertible preferred stock 134,230,572 17,133,339 $ 295,109 $ 107,867 $ 295,109 Total preferred stock 136,074,466 17,357,903 $ 297,652 $ 110,410 $ 295,109 December 31, 2014 Shares Shares Issued and Outstanding Net Carrying Liquidation Price Per Aggregate Redemption (in thousands, except share and per share data) Convertible Preferred Stock: Series A 1,843,894 224,564 $ 2,543 $ 11.324 $ 2,543 $ — Redeemable Convertible Preferred Stock: Series B 13,134,880 1,752,634 19,504 12.268 21,502 19,504 Series B-1 16,122,618 1,392,300 6,979 3.656 5,091 6,979 Series C 19,812,349 2,487,770 21,052 5.642 14,035 21,052 Series D 85,000,000 11,409,360 94,297 5.510 62,865 94,297 Total redeemable convertible preferred stock 134,069,847 17,042,064 $ 141,832 $ 103,493 $ 141,832 Total preferred stock 135,913,741 17,266,628 $ 144,375 $ 106,036 $ 141,832
Adjustment to Redemption Value of each Series of Redeemable Convertible Preferred Stock Recognized	The following table sets forth the total adjustment to redemption value of each series of redeemable convertible preferred stock recognized during the following period: Six Months Redeemable Convertible Preferred Stock Series B $ 23,184 Series B-1 16,307 Series C 20,359 Series D 92,035 Total adjustment to redemption value on redeemable convertible preferred stock $ 151,885
Summary of Assumptions used to Determine Fair Value of Temporary Equity	As the redemption value for the redeemable convertible preferred stock may at times be based on fair market value at each reporting date, the Company determines the fair value of the redeemable convertible preferred stock using a combination of the OPM and/or the PWERM models and as of June 30, 2015, the IPO price of the Company’s common stock. The following assumptions were used in the OPM: As of June 30, As of December 31, Expected term (in years) 0.9 1.2 – 2.5 Expected volatility 66 % 69 – 86% Risk-free interest rate 0.2 % 0.3 – 0.6% Expected dividend rate — % — %

Preferred Stock Warrants (Table

Preferred Stock Warrants (Tables)	6 Months Ended
	Jun. 30, 2015
Text Block [Abstract]
Summary of Redeemable Convertible Preferred Stock Warrants	The key terms of the redeemable convertible preferred stock warrants are summarized in the following table: Warrants Outstanding Warrants Outstanding 2015 Warrants Exercise Price Expiration Series B preferred stock warrants 10,414 10,414 $ 7.45 July 31, 2018 Series B-1 preferred stock warrants 43,969 47,060 7.45 June 30, 2018 Series B-1 preferred stock warrants 663,343 746,295 2.6075 Various dates in 2016 – 2021 Series C preferred stock warrants 166,318 171,566 5.215 Various dates in 2022 – 2023 Total preferred stock warrants 884,044 975,335
Schedule of Remeasuring Preferred Stock Warrants to Fair Value Using OPM and/or PWERM Models	At each reporting date, the Company remeasures the preferred stock warrants to fair value using the OPM and/or the PWERM models with the following assumptions used in the OPM: As of June 30, As of December 31, Expected term (in years) 0.9 1.2 – 2.5 Expected volatility 66 % 69 – 86% Risk-free interest rate 0.2 % 0.3 – 0.6% Expected dividend rate — % — % Discount for lack of marketability 11.3 % 19.5 – 24.3%

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	6 Months Ended
	Jun. 30, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Stock-based Compensation Expense for Employees and Non-employees	In the accompanying condensed consolidated statement of operations, the Company recognized stock-based compensation expense for its employees and non-employees as follows: Three Months Ended June 30, Six Months Ended June 30, 2015 2014 2015 2014 (in thousands) Research and development $ 225 $ 9 $ 299 $ 18 General and administrative 195 50 301 63 Total stock-based compensation $ 420 $ 59 $ 600 $ 81
Schedule of Estimated Grant-date Fair Value of Stock-based Awards Using Black-Scholes Option Pricing Model Assumptions	The estimated grant-date fair value of all the Company’s stock-based awards was calculated using the Black-Scholes option pricing model, based on assumptions as follows: Three Months Ended June 30, Six Months Ended June 30, 2015 2014 2015 2014 Expected term (in years) 5.2 – 10.0 5.7 6.0 – 10.0 5.0 – 5.7 Expected volatility 75 – 79% 83 % 75 – 81% 81 – 83% Risk-free interest rate 1.7% 1.6 % 1.5 – 1.7% 1.5 – 1.7% Expected dividend rate — % — % — % — %
Summary of Stock Options Activity	A summary of activity under the 2005 Plan and 2008 Plan and related information is as follows: Options Outstanding Shares Available for Grant Number of Shares Weighted- Weighted- Aggregate Intrinsic (in thousands) Outstanding — December 31, 2014 1,550,101 2,138,096 $ 0.91 9.29 $ 3,153 Awards authorized — — Options granted (1,184,566 ) 1,184,566 5.62 Options exercised — (27,813 ) 1.00 Options cancelled — — — Outstanding — June 30, 2015 365,535 3,294,849 $ 2.60 9.19 $ 40,849 Exercisable — June 30, 2015 2,115,209 $ 0.92 8.81 $ 29,783 Vested and expected to vest — June 30, 2015 2,983,562 $ 2.71 9.20 $ 36,665

The Company and Basis of Pres28

The Company and Basis of Presentation - Additional Information (Detail) $ / shares in Units, $ in Millions	Jul. 15, 2015USD ($)$ / sharesshares	Jun. 29, 2015	Jun. 30, 2015	Jul. 21, 2015$ / sharesshares
Class of Stock [Line Items]
Convertible preferred stock, conversion basis			On July 21, 2015, immediately prior to the closing of the IPO, all outstanding shares of convertible and redeemable convertible preferred stock converted into 17,971,273 shares of common stock. The IPO closed on July 21, 2015.
Reverse stock split, description			7.45-to-1
Reverse Stock Split, Conversion Ratio		7.45
Reverse stock split, effective date			Jul. 2, 2015
Subsequent Event [Member]
Class of Stock [Line Items]
Common stock issued and sold, price per share				$ 17
Redeemable convertible preferred stock converted into common stock | shares				17,971,273
Initial Public Offering [Member] | Subsequent Event [Member]
Class of Stock [Line Items]
Common stock issued and sold | shares	9,315,000
Common stock issued and sold, price per share	$ 17
Proceeds from issuance of common stock, net | $	$ 143.6

Summary of Significant Accoun29

Summary of Significant Accounting Policies - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2015USD ($)Segment	Dec. 31, 2014USD ($)
Summary Of Significant Accounting Policy [Line Items]
Deferred offering costs	$ 3,053,000	$ 549,000
Number of operating segment | Segment	1
Leasehold Improvements [Member]
Summary Of Significant Accounting Policy [Line Items]
Estimated useful lives of assets	3 years
Minimum [Member]
Summary Of Significant Accounting Policy [Line Items]
Estimated useful lives of assets	3 years
Maximum [Member]
Summary Of Significant Accounting Policy [Line Items]
Estimated useful lives of assets	5 years
Other Noncurrent Assets [Member]
Summary Of Significant Accounting Policy [Line Items]
Long-term portion of restricted cash	$ 200,000
Prepaid Expenses and Other Current Assets [Member]
Summary Of Significant Accounting Policy [Line Items]
Current portion of restricted cash	$ 25,000

Net Loss Per Share - Schedule o

Net Loss Per Share - Schedule of Outstanding Shares of Common Stock Equivalents Excluded from Calculation of Diluted Net Loss Per Share Attributable to Common Stockholders (Detail) - shares	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total potential dilutive shares	21,877,600	19,440,909
Options to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total potential dilutive shares	3,294,849	966,778
Common Stock Subject to Repurchase [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total potential dilutive shares	116,674
Convertible Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total potential dilutive shares	252,817	252,818
Redeemable Convertible Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total potential dilutive shares	17,328,059	17,236,784
Warrants for Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total potential dilutive shares	885,201	984,529

Net Loss Per Share - Additional

Net Loss Per Share - Additional Information (Detail)	Jun. 30, 2015USD ($)
Earnings Per Share [Abstract]
Contractual obligation to preferred stockholders	$ 0

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Fair Value Financial Assets and Liabilities Measured on Recurring Basis (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Financial Assets
Total financial assets	$ 25,466	$ 37,932
Preferred Stock Warrant Liabilities [Member]
Financial Liabilities
Total financial Liabilities	10,641	1,810
Money Market Funds [Member]
Financial Assets
Total financial assets	15,213	27,847
Restricted Money Market Funds [Member]
Financial Assets
Total financial assets	225	75
Short-Term Investments [Member]
Financial Assets
Total financial assets	10,028	10,010
Level 1 [Member]
Financial Assets
Total financial assets	15,438	27,922
Level 1 [Member] | Money Market Funds [Member]
Financial Assets
Total financial assets	15,213	27,847
Level 1 [Member] | Restricted Money Market Funds [Member]
Financial Assets
Total financial assets	225	75
Level 2 [Member]
Financial Assets
Total financial assets	10,028	10,010
Level 2 [Member] | Short-Term Investments [Member]
Financial Assets
Total financial assets	10,028	10,010
Level 3 [Member] | Preferred Stock Warrant Liabilities [Member]
Financial Liabilities
Total financial Liabilities	$ 10,641	$ 1,810

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - Jun. 30, 2015 - USD ($)	Total	Total
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Transfer of assets from level 1 to 2	$ 0	$ 0
Transfer of assets from level 2 to 1	0	0
Transfer of liabilities from level 1 to 2	0	0
Transfer of liabilities from level 2 to 1	0	0
Transfer of assets into level 3		0
Transfer of assets out of level 3		0
Transfer of liabilities into level 3		0
Transfer of liabilities out of level 3		0
Other Income (Expense) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recognized other-than-temporary impairment loss	$ 0	$ 10,000

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Warrant Liabilities Measured at Fair Value on a Recurring Basis Using Unobservable Inputs (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value of preferred stock warrants exercised			$ 1,100
Change in fair value of preferred stock warrants	$ 8,630	$ 347	9,956	$ 496
Level 3 [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance as of December 31, 2014			1,810
Fair value of preferred stock warrants exercised			(1,125)
Change in fair value of preferred stock warrants			9,956
Balance as of June 30, 2015	$ 10,641		$ 10,641

Balance Sheet Components - Summ

Balance Sheet Components - Summary of Cash and Cash Equivalents (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014	Dec. 31, 2013
Cash and Cash Equivalents [Abstract]
Cash	$ 587	$ 1,307
Cash equivalents:
Money market accounts	15,213	27,847
Total cash and cash equivalents	$ 15,800	$ 29,154	$ 46,080	$ 2,429

Balance Sheet Components - Su36

Balance Sheet Components - Summary of Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid research and development project costs	$ 414	$ 515
Other	368	46
Total prepaid expenses and other current assets	$ 782	$ 561

Balance Sheet Components - Su37

Balance Sheet Components - Summary of Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 450	$ 228
Less: accumulated depreciation	(53)	(14)
Total property and equipment, net	397	214
Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	140	56
Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	11	9
Lab Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	224	$ 163
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 75

Balance Sheet Components - Addi

Balance Sheet Components - Additional Information (Detail) - USD ($)	3 Months Ended	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2015	Jun. 30, 2014
Property, Plant and Equipment [Abstract]
Depreciation and amortization related to property and equipment	$ 26,000	$ 39,000	$ 1,000

Balance Sheet Components - Sche

Balance Sheet Components - Schedule of Other Assets (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Deferred offering costs	$ 3,053	$ 549
Restricted cash	200	75
Deferred tax assets	3	2
Total other assets	$ 3,256	$ 626

Balance Sheet Components - Su40

Balance Sheet Components - Summary of Accrued Liabilities (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Payables and Accruals [Abstract]
Accrued offering costs	$ 615
Accrued employee related costs	572	$ 759
Accrued research and development costs	686	526
Accrued professional fees	408	140
Other	23	48
Total accrued liabilities	$ 2,304	$ 1,473

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail)	Jun. 30, 2015USD ($)	Apr. 30, 2014USD ($)	May. 31, 2013USD ($)shares	Jun. 30, 2015USD ($)	Jun. 30, 2014USD ($)	Jun. 30, 2015USD ($)	Jun. 30, 2014USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2012USD ($)	Feb. 28, 2015USD ($)	Feb. 28, 2015CAD	Jul. 31, 2014USD ($)
Loss Contingencies [Line Items]
Upfront payment paid									$ 300,000
Payment in cash upon closing of financing		$ 11,000,000
Milestone payment upon regulatory authority approval		3,000,000
Manufacturing costs obligation												$ 100,000
Milestone payment not accrued	$ 3,000,000			$ 3,000,000		$ 3,000,000
Payments to contract research organization				600,000		1,600,000
Cumulative unpaid accruing dividends in arrears	18,500,000					$ 18,500,000		$ 14,400,000
Novosom License Agreement [Member]
Loss Contingencies [Line Items]
Shares of common stock issued in settlement of first milestone payment | shares			2,108,870
Fair marker value of common stock issued			$ 100,000
Maximum [Member]
Loss Contingencies [Line Items]
Aggregate milestone payment									$ 14,500,000
Minimum [Member]
Loss Contingencies [Line Items]
Payment for financing		$ 35,000,000
Vancouver Facility [Member]
Loss Contingencies [Line Items]
Operating lease agreement expiration date						Feb. 27, 2018
Letter of credit issued | CAD											CAD 50,000
Collateralized restricted deposit										$ 50,000
Total rent expense for operating leases				$ 100,000	$ 14,000	$ 100,000	$ 22,000
Series B Redeemable Convertible Preferred Stock [Member]
Loss Contingencies [Line Items]
Preferred stock, cumulative dividend percentage rate						8.00%
Cumulative unpaid accruing dividends in arrears	9,300,000					$ 9,300,000		8,400,000
Series B-1 Redeemable Convertible Preferred Stock [Member]
Loss Contingencies [Line Items]
Preferred stock, cumulative dividend percentage rate						8.00%
Cumulative unpaid accruing dividends in arrears	1,700,000					$ 1,700,000		1,500,000
Series C Redeemable Convertible Preferred Stock [Member]
Loss Contingencies [Line Items]
Preferred stock, cumulative dividend percentage rate						8.00%
Cumulative unpaid accruing dividends in arrears	1,600,000					$ 1,600,000		1,100,000
Series D Redeemable Convertible Preferred Stock [Member]
Loss Contingencies [Line Items]
Preferred stock, cumulative dividend percentage rate						8.00%
Cumulative unpaid accruing dividends in arrears	$ 5,900,000					$ 5,900,000		$ 3,400,000

Commitments and Contingencies42

Commitments and Contingencies - Schedule of Aggregate Future Non-Cancelable Minimum Lease Payments (Detail) $ in Thousands	Jun. 30, 2015USD ($)
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2015 (remainder)	$ 133
2,016	319
2,017	319
2,018	53
Total	$ 824

Commitments and Contingencies43

Commitments and Contingencies - Summary of Aggregate Future Minimum Payments (Detail) $ in Thousands	Jun. 30, 2015USD ($)
Commitments and Contingencies Disclosure [Abstract]
Contract Research Organization Obligations, 2015 (remainder)	$ 2,025
Contract Research Organization Obligations, 2016	5,303
Contract Research Organization Obligations, 2017	4,914
Contract Research Organization Obligations, 2018	255
Contract Research Organization Obligations, Total	$ 12,497

Common Stock Reserved for Iss44

Common Stock Reserved for Issuance - Schedule of Common Stock Reserved for Issuance (Detail) - shares	Jun. 30, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total common stock reserved for future issuance	22,126,461	22,154,290
Outstanding Preferred Stock Warrants [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total common stock reserved for future issuance	885,201	976,492
Series A Convertible Preferred Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total common stock reserved for future issuance	252,817	252,817
Series B Redeemable Convertible Preferred Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total common stock reserved for future issuance	1,947,354	1,947,354
Series B-1 Redeemable Convertible Preferred Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total common stock reserved for future issuance	1,478,328	1,392,300
Series C Redeemable Convertible Preferred Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total common stock reserved for future issuance	2,493,017	2,487,770
Series D Redeemable Convertible Preferred Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total common stock reserved for future issuance	11,409,360	11,409,360
Outstanding And Issued Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total common stock reserved for future issuance	3,294,849	2,138,096
Shares Reserved For Future Option Grants [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total common stock reserved for future issuance	365,535	1,550,101

Convertible and Redeemable Co45

Convertible and Redeemable Convertible Preferred Stock - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	Jun. 30, 2015	Jun. 11, 2015	Jun. 30, 2015	Dec. 31, 2014
Temporary Equity [Line Items]
Percentage of accrued but unpaid dividends paid in shares		50.00%
Percentage of accrued but unpaid dividends forfeited		50.00%
Share price, accrued dividend in shares		$ 5.215
Cumulative unpaid accruing dividends in arrears	$ 18.5		$ 18.5	$ 14.4
Exercise put options period		120 days
Series B-1 Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Number of shares issued upon exercise of stock warrants	86,028		86,028
Cumulative unpaid accruing dividends in arrears	$ 1.7		$ 1.7	1.5
Accruing dividends	$ 0.9		$ 0.9
Series C Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Number of shares issued upon exercise of stock warrants	5,247		5,247
Cumulative unpaid accruing dividends in arrears	$ 1.6		$ 1.6	1.1
Issuable common stock to redeemable convertible preferred stockholders	155,273		155,273
Series D Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Cumulative unpaid accruing dividends in arrears	$ 5.9		$ 5.9	3.4
Issuable common stock to redeemable convertible preferred stockholders	561,685		561,685
Series B and B-1 Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Accruing dividends	$ 5.5		$ 5.5
Series B Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Cumulative unpaid accruing dividends in arrears	9.3		9.3	$ 8.4
Accruing dividends	$ 4.6		$ 4.6
Series C and D Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Issuable common stock to redeemable convertible preferred stockholders	716,958		716,958

Convertible and Redeemable Co46

Convertible and Redeemable Convertible Preferred Stock - Components of Convertible and Redeemable Convertible Preferred Stock (Detail) - USD ($) $ / shares in Units, $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Temporary Equity [Line Items]
Shares Authorized	136,074,466	135,913,741
Shares Issued	17,357,903	17,266,628
Net Carrying Value	$ 297,652	$ 144,375
Aggregate Liquidation Preference	110,410	106,036
Redemption Value	$ 295,109	$ 141,832
Shares Outstanding	17,357,903	17,266,628
Series A Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Shares Authorized	1,843,894	1,843,894
Shares Issued	224,564	224,564
Net Carrying Value	$ 2,543	$ 2,543
Liquidation Price Per Share	$ 11.324	$ 11.324
Aggregate Liquidation Preference	$ 2,543	$ 2,543
Shares Outstanding	224,564	224,564
Series B Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Shares Authorized	13,134,880	13,134,880
Shares Issued	1,752,634	1,752,634
Net Carrying Value	$ 42,688	$ 19,504
Liquidation Price Per Share	$ 12.755	$ 12.268
Aggregate Liquidation Preference	$ 22,355	$ 21,502
Redemption Value	$ 42,688	$ 19,504
Shares Outstanding	1,752,634	1,752,634
Series B-1 Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Shares Authorized	16,283,343	16,122,618
Shares Issued	1,478,328	1,392,300
Net Carrying Value	$ 24,596	$ 6,979
Liquidation Price Per Share	$ 3.742	$ 3.656
Aggregate Liquidation Preference	$ 5,532	$ 5,091
Redemption Value	$ 24,596	$ 6,979
Shares Outstanding	1,478,328	1,392,300
Series C Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Shares Authorized	19,812,349	19,812,349
Shares Issued	2,493,017	2,487,770
Net Carrying Value	$ 41,493	$ 21,052
Liquidation Price Per Share	$ 5.865	$ 5.642
Aggregate Liquidation Preference	$ 14,621	$ 14,035
Redemption Value	$ 41,493	$ 21,052
Shares Outstanding	2,493,017	2,487,770
Series D Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Shares Authorized	85,000,000	85,000,000
Shares Issued	11,409,360	11,409,360
Net Carrying Value	$ 186,332	$ 94,297
Liquidation Price Per Share	$ 5.728	$ 5.510
Aggregate Liquidation Preference	$ 65,359	$ 62,865
Redemption Value	$ 186,332	$ 94,297
Shares Outstanding	11,409,360	11,409,360
Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Shares Authorized	134,230,572	134,069,847
Shares Issued	17,133,339	17,042,064
Net Carrying Value	$ 295,109	$ 141,832
Aggregate Liquidation Preference	107,867	103,493
Redemption Value	$ 295,109	$ 141,832
Shares Outstanding	17,133,339	17,042,064

Convertible and Redeemable Co47

Convertible and Redeemable Convertible Preferred Stock - Adjustment to Redemption Value of each Series of Redeemable Convertible Preferred Stock Recognized (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Temporary Equity [Line Items]
Adjustment to redemption value	$ (140,880)	$ (36,833)	$ (151,885)	$ (39,275)
Series B Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Adjustment to redemption value			23,184
Series B-1 Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Adjustment to redemption value			16,307
Series C Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Adjustment to redemption value			20,359
Series D Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Adjustment to redemption value			92,035
Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Adjustment to redemption value			$ 151,885

Convertible and Redeemable Co48

Convertible and Redeemable Convertible Preferred Stock - Summary of Assumptions used to Determine Fair Value of Temporary Equity (Detail)	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
Temporary Equity [Line Items]
Expected term (in years)	10 months 24 days
Expected volatility	66.00%
Risk-free interest rate	0.20%
Expected dividend rate	0.00%	0.00%
Minimum [Member]
Temporary Equity [Line Items]
Expected term (in years)		1 year 2 months 12 days
Expected volatility		69.00%
Risk-free interest rate		0.30%
Maximum [Member]
Temporary Equity [Line Items]
Expected term (in years)		2 years 6 months
Expected volatility		86.00%
Risk-free interest rate		0.60%

Preferred Stock Warrants - Addi

Preferred Stock Warrants - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Jun. 30, 2015	Dec. 31, 2014
Class of Warrant or Right [Line Items]
Preferred stock warrant liabilities	$ 10,641	$ 10,641	$ 1,810
Warrants exercised			0
Cash proceeds from warrants exercised		300
Fair value of warrant liability reclassified to redeemable convertible preferred stock		$ 1,100
Series B-1 Preferred Stock Warrants, Expiration June 30, 2018 [Member]
Class of Warrant or Right [Line Items]
Warrants exercised	3,079	3,079
Warrants exercise price	$ 7.4500	$ 7.4500
Series B-1 Preferred Stock Warrants, Expiration Various Dates In 2016 - 2021 [Member]
Class of Warrant or Right [Line Items]
Warrants exercised	82,949	82,949
Warrants exercise price	$ 2.6075	$ 2.6075
Series C Preferred Stock Warrants [Member]
Class of Warrant or Right [Line Items]
Warrants exercised	5,247	5,247
Warrants exercise price	$ 5.2150	$ 5.2150

Preferred Stock Warrants - Summ

Preferred Stock Warrants - Summary of Redeemable Convertible Preferred Stock Warrants (Detail) - $ / shares	6 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
Class of Warrant or Right [Line Items]
Warrants Outstanding	884,044	975,335
Series B Preferred Stock Warrants [Member]
Class of Warrant or Right [Line Items]
Warrants Outstanding	10,414	10,414
Warrants Outstanding, Exercise Price	$ 7.4500
Warrants Outstanding, Expiration Description	July 31, 2018
Series B-1 Preferred Stock Warrants, Expiration June 30, 2018 [Member]
Class of Warrant or Right [Line Items]
Warrants Outstanding	43,969	47,060
Warrants Outstanding, Exercise Price	$ 7.4500
Warrants Outstanding, Expiration Description	June 30, 2018
Series B-1 Preferred Stock Warrants, Expiration Various Dates In 2016 - 2021 [Member]
Class of Warrant or Right [Line Items]
Warrants Outstanding	663,343	746,295
Warrants Outstanding, Exercise Price	$ 2.6075
Warrants Outstanding, Expiration Description	Various dates in 2016 - 2021
Series C Preferred Stock Warrants [Member]
Class of Warrant or Right [Line Items]
Warrants Outstanding	166,318	171,566
Warrants Outstanding, Exercise Price	$ 5.2150
Warrants Outstanding, Expiration Description	Various dates in 2022 - 2023

Preferred Stock Warrants - Sche

Preferred Stock Warrants - Schedule of Remeasuring Preferred Stock Warrants to Fair Value Using OPM and/or PWERM Models (Detail)	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2015	Dec. 31, 2014
Class of Stock [Line Items]
Expected term (in years)			10 months 24 days
Expected volatility			66.00%
Risk-free interest rate			0.20%
Expected dividend rate			0.00%	0.00%
Outstanding Preferred Stock Warrants [Member]
Class of Stock [Line Items]
Expected term (in years)	10 months 24 days
Expected volatility	66.00%
Risk-free interest rate	0.20%
Expected dividend rate	0.00%	0.00%
Discount for lack of marketability	11.30%
Minimum [Member]
Class of Stock [Line Items]
Expected term (in years)				1 year 2 months 12 days
Expected volatility				69.00%
Risk-free interest rate				0.30%
Minimum [Member] | Outstanding Preferred Stock Warrants [Member]
Class of Stock [Line Items]
Expected term (in years)		1 year 2 months 12 days
Expected volatility		69.00%
Risk-free interest rate		0.30%
Expected dividend rate		0.00%
Discount for lack of marketability		19.50%
Maximum [Member]
Class of Stock [Line Items]
Expected term (in years)				2 years 6 months
Expected volatility				86.00%
Risk-free interest rate				0.60%
Maximum [Member] | Outstanding Preferred Stock Warrants [Member]
Class of Stock [Line Items]
Expected term (in years)		2 years 6 months
Expected volatility		86.00%
Risk-free interest rate		0.60%
Expected dividend rate		0.00%
Discount for lack of marketability		24.30%

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Stock-based Compensation Expense for Employees and Non-employees (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	$ 420	$ 59	$ 600	$ 81
Research and development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	225	9	299	18
General and administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	$ 195	$ 50	$ 301	$ 63

Stock-Based Compensation - Sc53

Stock-Based Compensation - Schedule of Estimated Grant-date Fair Value of Stock-based Awards Using Black-Scholes Option Pricing Model Assumptions (Detail)	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)		5 years 8 months 12 days
Expected volatility, Minimum	75.00%		75.00%	81.00%
Expected volatility, Maximum	79.00%		81.00%	83.00%
Expected volatility		83.00%
Risk-free interest rate	1.70%	1.60%
Risk-free interest rate, Minimum			1.50%	1.50%
Risk-free interest rate, Maximum			1.70%	1.70%
Expected dividend rate	0.00%	0.00%	0.00%	0.00%
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	5 years 2 months 12 days		6 years	5 years
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	10 years		10 years	5 years 8 months 12 days

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - USD ($)	Jun. 30, 2015	Dec. 31, 2014	Dec. 31, 2013	Feb. 28, 2015	Dec. 31, 2014	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014	Jun. 24, 2008
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation						$ 420,000	$ 59,000	$ 600,000	$ 81,000
Proceeds from early exercise of stock options								13,000
Performance-Based Stock Option Grant [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation						$ 0		0
Additional stock-based compensation related to stock options								$ 100,000
Performance-Based Stock Option Grant [Member] | Executive officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted options to purchase shares of common stock										217,305
2008 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Approved for issuance of common stock											308,725
Authorized shares increase		4,802,013	1,580,537
Term of plan								10 years
Number of shares held by employees subject to repurchase	116,674	103,252			103,252	116,674		116,674		103,252
Aggregate price of shares subject to repurchase	$ 100,000	$ 100,000			$ 100,000	$ 100,000		$ 100,000		$ 100,000
2008 Plan [Member] | Executive officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options early exercised				13,422	103,252
Proceeds from early exercise of stock options	$ 100,000	$ 100,000
2005 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards issued	940
Awards outstanding	940					940		940
Weighted-average grant date fair values of options granted						$ 12.03	$ 0.41	$ 4.35	$ 0.41
Aggregate intrinsic value of options exercised						$ 0	$ 16,000	$ 400,000	$ 100,000
Total grant date fair value of options vested						$ 100,000	$ 100,000	$ 200,000	$ 100,000
Total unrecognized stock-based compensation related to unvested stock options	$ 12,800,000					$ 12,800,000		$ 12,800,000
Weighted-average period								1 year 11 months 1 day

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock Options Activity (Detail) - 2005 Plan and 2008 Plan [Member] - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Available for Grant, Beginning balance	1,550,101
Shares Available for Grant, Awards authorized	0
Shares Available for Grant, Granted	(1,184,566)
Shares Available for Grant, Exercised	0
Shares Available for Grant, Cancelled	0
Shares Available for Grant, Ending balance	365,535	1,550,101
Number of Shares Outstanding, Beginning balance	2,138,096
Number of Shares Outstanding, Options granted	1,184,566
Number of Shares Outstanding, Options exercised	(27,813)
Number of Shares Outstanding, Options cancelled	0
Number of Shares Outstanding, Ending balance	3,294,849	2,138,096
Number of Shares Outstanding, Exercisable	2,115,209
Number of Shares Outstanding, Vested and expected to vest	2,983,562
Weighted-Average Exercise Price Per Share, Beginning balance	$ 0.91
Weighted-Average Exercise Price Per Share, Options granted	5.62
Weighted-Average Exercise Price Per Share, Options exercised	1
Weighted-Average Exercise Price Per Share, Options cancelled	0
Weighted-Average Exercise Price Per Share, Ending balance	2.60	$ 0.91
Weighted-Average Exercise Price Per Share, Exercisable	0.92
Weighted-Average Exercise Price Per Share, Vested and expected to vest	$ 2.71
Weighted-Average Remaining Contractual Term (Years)	9 years 2 months 9 days	9 years 3 months 15 days
Weighted-Average Remaining Contractual Term (Year), Exercisable	8 years 9 months 22 days
Weighted-Average Remaining Contractual Term (Year), Vested and expected to vest	9 years 2 months 12 days
Aggregate Intrinsic Value of Outstanding Options	$ 40,849	$ 3,153
Aggregate Intrinsic Value of Outstanding Options, Exercisable	29,783
Aggregate Intrinsic Value of Outstanding Options, Vested and expected to vest	$ 36,665

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - Jun. 30, 2015 - USD ($)	Total	Total
Income Tax Disclosure [Abstract]
Provision for federal income taxes	$ 0	$ 0
Income tax expense for foreign taxes	$ 1,000	$ 11,000

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	Jul. 21, 2015	Jul. 10, 2015	Jun. 30, 2015	Jun. 30, 2015	Dec. 31, 2014	Jul. 15, 2015	Jul. 14, 2015	Jun. 24, 2008
Subsequent Event [Line Items]
Preferred stock warrants exercised					0
Cash proceeds from warrants exercised				$ 0.3
Number of common stock shares reserved for issuance			22,126,461	22,126,461	22,154,290
Amended and restated common stock authorized			180,000,000	180,000,000	180,000,000
Amended and restated preferred stock authorized			136,074,466	136,074,466	135,913,741
Performance-Based Stock Option Grant [Member]
Subsequent Event [Line Items]
Additional stock-based compensation related to stock options				$ 0.1
2008 Plan [Member]
Subsequent Event [Line Items]
Maximum number of common stock shares allowed to issue under employee stock purchase plan								308,725
Series B and B-1 Redeemable Convertible Preferred Stock [Member]
Subsequent Event [Line Items]
Accruing dividends			$ 5.5	$ 5.5
Subsequent Event [Member]
Subsequent Event [Line Items]
Preferred stock warrants exercised	493,648
Cash proceeds from warrants exercised		$ 1.2
Number of common stock shares issued upon exercise of preferred stock warrants	390,680
IPO price per share	$ 17
Amended and restated common stock authorized	500,000,000
Amended and restated preferred stock authorized	10,000,000
Subsequent Event [Member] | Executive officer [Member] | Performance-Based Stock Option Grant [Member]
Subsequent Event [Line Items]
Additional stock-based compensation related to stock options	$ 0.1
Subsequent Event [Member] | 2008 Plan [Member]
Subsequent Event [Line Items]
Number of common stock shares reserved for issuance	365,535
Subsequent Event [Member] | 2015 Equity Incentive Plan [Member]
Subsequent Event [Line Items]
Number of common stock shares reserved for issuance							3,400,000
Subsequent Event [Member] | 2015 Employee Stock Purchase Plan [Member]
Subsequent Event [Line Items]
Number of common stock shares reserved for issuance						700,000
Maximum number of common stock shares allowed to issue under employee stock purchase plan						3,400,000
Subsequent Event [Member] | Series B and B-1 Redeemable Convertible Preferred Stock [Member]
Subsequent Event [Line Items]
Accruing dividends	$ 5.5
Subsequent Event [Member] | Series C and D Redeemable Convertible Preferred Stock [Member]
Subsequent Event [Line Items]
Accruing dividends	$ 3.9
Number of common stock shares issued to preferred stockholders in payment of cumulative accrued dividends	750,946
Series B-1 Preferred Stock Warrants, Expiration June 30, 2018 [Member]
Subsequent Event [Line Items]
Preferred stock warrants exercised			3,079	3,079
Warrants exercise price			$ 7.4500	$ 7.4500
Series B-1 Preferred Stock Warrants, Expiration June 30, 2018 [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Preferred stock warrants exercised		28,699
Warrants exercise price		$ 7.4500
Series B-1 Preferred Stock Warrants, Expiration Various Dates In 2016 - 2021 [Member]
Subsequent Event [Line Items]
Preferred stock warrants exercised			82,949	82,949
Warrants exercise price			$ 2.6075	$ 2.6075
Series B-1 Preferred Stock Warrants, Expiration Various Dates In 2016 - 2021 [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Preferred stock warrants exercised		329,559
Warrants exercise price		$ 2.6075
Series C Preferred Stock Warrants [Member]
Subsequent Event [Line Items]
Preferred stock warrants exercised			5,247	5,247
Warrants exercise price			$ 5.2150	$ 5.2150
Series C Preferred Stock Warrants [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Preferred stock warrants exercised		32,138
Warrants exercise price		$ 5.2150