Rocket Pharmaceuticals (RCKT) 10-Q 9 Nov 16 2016 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2016	Nov. 08, 2016
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2016
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	Q3
Trading Symbol	ITEK
Entity Registrant Name	Inotek Pharmaceuticals Corporation
Entity Central Index Key	1,281,895
Current Fiscal Year End Date	--12-31
Entity Filer Category	Smaller Reporting Company
Entity Common Stock, Shares Outstanding		26,930,730

Consolidated Balance Sheets (Un

Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 83,004	$ 80,042
Short-term investments	54,579	31,238
Prepaid expenses and other current assets	1,341	1,086
Total current assets	138,924	112,366
Property and equipment, net	1,045	812
Other assets	170	143
Total assets	140,139	113,321
Current liabilities:
Accounts payable	1,777	1,633
Accrued expenses and other current liabilities	3,716	2,508
Accrued interest	451
Total current liabilities	5,944	4,141
Other long-term liabilities	321	367
Total liabilities	55,085	4,508
Commitments and Contingencies (Note 7)
Stockholders’ equity:
Preferred Stock, $0.001 par value: 5,000,000 shares authorized and no shares issued or outstanding
Common stock, $0.01 par value: 120,000,000 shares authorized at September 30, 2016 and December 31, 2015; 26,930,730 shares and 26,423,394 shares issued and outstanding at September 30, 2016 and December 31, 2015, respectively	269	264
Additional paid-in capital	310,686	304,583
Accumulated deficit	(225,903)	(196,023)
Accumulated other comprehensive income (loss)	2	(11)
Total stockholders’ equity	85,054	108,813
Total liabilities and stockholders’ equity	140,139	$ 113,321
2021 Convertible Notes [Member]
Current liabilities:
2021 Convertible Notes, net of issuance costs	$ 48,820

Consolidated Balance Sheets (U3

Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Sep. 30, 2016	Dec. 31, 2015
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	120,000,000	120,000,000
Common stock, shares issued	26,930,730	26,423,394
Common stock, shares outstanding	26,930,730	26,423,394

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Operating expenses:
Research and development	$ (8,412)	$ (3,612)	$ (22,492)	$ (6,635)
General and administrative	(2,311)	(1,825)	(7,148)	(5,533)
Loss from operations	(10,723)	(5,437)	(29,640)	(12,168)
Interest expense	(525)	(192)	(525)	(1,230)
Interest income	120	33	285	33
Loss on extinguishment of debt		(3,716)		(4,399)
Change in fair value of warrant liabilities				267
Change in fair value of Convertible Bridge Notes redemption rights derivative				480
Change in fair value of 2020 Convertible Notes derivative liability		(46,649)		(42,793)
Net loss	$ (11,128)	$ (55,961)	$ (29,880)	$ (59,810)
Net loss per share attributable to common stockholders—basic and diluted	$ (0.41)	$ (2.48)	$ (1.12)	$ (3.85)
Weighted-average number of shares outstanding—basic and diluted	26,930,730	22,573,195	26,660,126	15,580,487

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (11,128)	$ (55,961)	$ (29,880)	$ (59,810)
Other comprehensive income:
Net unrealized income (loss) on marketable securities	(15)		13
Total comprehensive loss	$ (11,143)	$ (55,961)	$ (29,867)	$ (59,810)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Cash flows from operating activities:
Net loss	$ (29,880)	$ (59,810)
Adjustments to reconcile net loss to cash used in operating activities:
Noncash interest expense	82	1,132
Noncash rent expense	(46)	(5)
Loss on extinguishment of debt		4,239
Amortization of premium on marketable securities	164
Depreciation	111	7
Change in fair value of warrant liabilities		(267)
Change in fair value of Convertible Bridge Notes redemption rights derivative		(480)
Change in fair value of 2020 Convertible Notes derivative liability		42,793
Stock-based compensation	1,978	1,932
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(340)	(968)
Accounts payable	144	563
Accrued expenses and other current liabilities	1,659	487
Net cash used in operating activities	(26,128)	(10,377)
Cash flows from investing activities:
Purchases of short-term investments	(69,070)	(29,117)
Proceeds from the maturities of short-term investments	45,636
Purchases of property and equipment	(344)	(318)
Net cash used in investing activities	(23,778)	(29,435)
Cash flows from financing activities:
Net proceeds from issuance of common stock in initial public offering		38,085
Proceeds from issuance of 2020 Convertible Notes in initial public offering		21,000
Net proceeds from issuance of common stock	3,997	73,955
Principal payments on notes payable		(5,800)
Net cash provided by financing activities	52,868	125,442
Net change in cash and cash equivalents	2,962	85,630
Cash and cash equivalents, beginning of period	80,042	3,618
Cash and cash equivalents, end of period	83,004	89,248
Supplemental disclosure of cash flow information:
Cash paid for interest		89
Supplemental disclosure of noncash investing and financing activities:
Acquisition of leasehold improvements		445
Conversion of Notes into common stock		66,375
2021 Convertible Notes [Member]
Cash flows from financing activities:
Proceeds from issuance of 2021 Convertible Notes	52,000
Payments of Notes issuance costs	(3,262)
2020 Convertible Notes [Member]
Adjustments to reconcile net loss to cash used in operating activities:
Loss on extinguishment of debt		3,716
Cash flows from financing activities:
Payments of Notes issuance costs		(1,841)
Stock Option Plans [Member]
Cash flows from financing activities:
Proceeds from issuance of common stock	88	43
Employee Stock Purchase Plan [Member]
Cash flows from financing activities:
Proceeds from issuance of common stock	45
IPO [Member]
Supplemental disclosure of noncash investing and financing activities:
Conversion of Notes into common stock		2,028
Reclassification of fair value of warrant liability to equity upon initial public offering		215
Reclassification of deferred public offering costs to stockholders' equity		1,590
Reclassification of deferred public offering costs to other assets		256
Net unrealized gain on marketable securities	$ 13
Series AA Redeemable Convertible Preferred Stock [Member]
Supplemental disclosure of noncash investing and financing activities:
Accretion of Series AA preferred stock to redemption value		130
Series AA Redeemable Convertible Preferred Stock [Member] | IPO [Member]
Supplemental disclosure of noncash investing and financing activities:
Conversion of preferred stock into common stock upon initial public offering		46,383
Series X Redeemable Convertible Preferred Stock [Member] | IPO [Member]
Supplemental disclosure of noncash investing and financing activities:
Conversion of preferred stock into common stock upon initial public offering		$ 548

Organization and Operations

Organization and Operations	9 Months Ended
	Sep. 30, 2016
Accounting Policies [Abstract]
Organization and Operations	1. Organization and Operations Inotek Pharmaceuticals Corporation (the “Company”) is a clinical-stage biopharmaceutical company advancing molecules with novel mechanisms of action to address significant diseases of the eye. The Company’s business strategy is to develop and progress its product candidates through human clinical trials and commercialize such products if successfully developed. The Company’s headquarters are located in Lexington, Massachusetts. The Company has devoted substantially all of its efforts to research and development, including clinical trials of its product candidates. The Company has not completed the development of any product candidates. The Company has no current source of revenue to sustain present activities and does not expect to generate revenue until and unless the Company receives regulatory approval of and successfully commercializes its product candidates. The Company is subject to a number of risks and uncertainties similar to those of other life science companies developing new products, including, among others, the risks related to the necessity to obtain adequate additional financing, to successfully develop product candidates, to obtain regulatory approval of products candidates, to comply with government regulations, to successfully commercialize its potential products, to protect proprietary technology and to the dependence on key individuals. In August 2016, the Company closed an underwritten public offering of $52,000 aggregate principal amount of 5.75% Convertible Senior Notes due 2021, including $2,000 from an exercise of the underwriters’ overallotment option, (the “2021 Convertible Notes”), and received net proceeds of $48,738 after deducting underwriting discounts and offering-related costs (see Note 5). In April 2016, the Company filed a registration statement on Form S-3 containing two prospectuses: (i) a base prospectus which covers the offering, issuance and sale of up to $200,000 in the aggregate of an indeterminate number of shares of common stock and preferred stock, such indeterminate principal amount of debt securities and such indeterminate number of warrants and units; and (ii) a sales agreement prospectus covering the offering, issuance and sale of up to a maximum aggregate offering price of $50,000 of the Company’s common stock that may be issued and sold under an at-the-market sales agreement with Cowen and Company, LLC (the “ATM”). The $50,000 of common stock that may be issued and sold under the ATM reduces the available balance under the base prospectus by the amount issued. The Company did not sell any shares of common stock pursuant to the ATM during the three months ended September 30, 2016. During the nine months ended September 30, 2016, the Company sold 482,689 shares of common stock and received net proceeds of $3,997, pursuant to the ATM. At September 30, 2016, $45,599 was available for sale of common stock under the ATM. In the first quarter of 2015, the Company completed its initial public offering (the “IPO”) of (i) 6,966,333 shares of common stock, including 299,333 shares from an exercise of the underwriters’ overallotment option at a price of $6.00 per share and (ii) $21,000 aggregate principal amount of 5.0% Convertible Senior Notes due 2020 (the “2020 Convertible Notes”), including $1,000 from an exercise of the underwriters’ overallotment option. Existing stockholders and their affiliated entities purchased approximately 3,005,000 shares of common stock issued in the IPO at the same terms. The Company received net proceeds of $36,495, after deducting underwriting discounts and offering-related costs, from its equity issuances and $18,903 in net proceeds, after deducting underwriting discounts and offering-related costs, from its debt issuances. In July and August 2015, holders of $21,000 principal amount of the 2020 Convertible Notes elected to convert the principal into 3,333,319 shares of common stock. In addition, the Interest Make-Whole Payment (see Note 5) was settled with shares of common stock, at the election of the Company, resulting in the issuance of 530,072 additional shares of common stock. In August 2015, the Company completed an underwritten public offering of its common stock (the “Follow-on Offering”). The Company issued 6,210,000 shares of its common stock at a price of $12.75 per share, including 810,000 shares from the underwriters’ full exercise of their overallotment option, and received net proceeds of $73,955, after deducting underwriting discounts and offering-related costs. As of September 30, 2016, the Company had an accumulated deficit of $225,903 and $137,583 of cash and cash equivalents and short-term investments. The Company will need to expend substantial resources for research and development, including costs associated with the clinical testing of its product candidates and will need to obtain additional financing to fund its operations and to conduct trials for its product candidates. If such products were to receive regulatory approval, the Company would need to prepare for the potential commercialization of its product candidates and fund the commercial launch and continued marketing of its products. The Company expects operating expenses will substantially increase in the future related to additional clinical testing and to support an increased infrastructure to support expanded operations and being a public company. The Company will require additional funding in the future and may not be able to raise such additional funds. The Company expects losses will continue as it conducts research and development activities. The Company will seek to finance future cash needs through public or private equity offerings, license agreements, debt financings, collaborations, strategic alliances, or any combination thereof. The incurrence of indebtedness would result in increased fixed payment obligations and could also result in restrictive covenants, such as limitations on the Company’s ability to incur additional debt, limitations on the Company’s ability to acquire, sell or license intellectual property rights and other operating restrictions that could adversely impact the ability of the Company to conduct its business. If adequate funds are not available, the Company would delay, reduce or eliminate research and development programs and reduce administrative expenses. The Company may seek to access the public or private capital markets whenever conditions are favorable, even if it does not have an immediate need for additional capital at that time. In addition, if the Company raises additional funds through collaborations, strategic alliances or licensing arrangements with third parties, it may have to relinquish valuable rights to its technologies, future revenue streams or product candidates or to grant licenses on terms that may not be favorable to it. If the Company is unable to raise sufficient funding, it may be unable to continue to operate. There is no assurance that the Company will be successful in obtaining sufficient financing on acceptable terms and conditions to fund continuing operations, if at all. The failure of the Company to obtain sufficient funds on acceptable terms when needed could have a material adverse effect on the Company’s business, results of operations and financial condition.

Significant Accounting Policies

Significant Accounting Policies	9 Months Ended
	Sep. 30, 2016
Accounting Policies [Abstract]
Significant Accounting Policies	2. Significant Accounting Policies Basis of Presentation —The Company’s interim financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). In the opinion of management, the Company has made all necessary adjustments, which include normal recurring adjustments necessary for a fair statement of the Company’s financial position and results of operations for the interim periods presented. Certain information and disclosures normally included in the annual financial statements prepared in accordance with GAAP have been condensed or omitted. These interim financial statements should be read in conjunction with the audited financial statements and accompanying notes for the year ended December 31, 2015 included in the Company’s Annual Report on Form 10-K. The results for the three and nine month periods ended September 30, 2016 are not necessarily indicative of the results to be expected for a full year, any other interim periods or any future year or period. The accompanying consolidated financial statements include our accounts and those of our wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. Segment Reporting —Operating segments are defined as components of an enterprise about which separate discrete information is available for evaluation by the chief operating decision maker, or decision-making group, in deciding how to allocate resources and in assessing performance. The Company views its operations and manages its business in one operating segment. Use of Estimates —The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting period. Actual results could differ from these estimates. Significant items subject to such estimates and assumptions include the valuation of stock options used for the calculation of stock-based compensation, fair value of warrant liabilities and other derivative financial instruments, and calculation of accruals related to research and clinical development. Comprehensive income (loss)— Comprehensive income (loss) is defined as the change in equity of a business enterprise during a period from transactions, and other events and circumstances from non-owner sources, and currently consists of net loss and changes in unrealized gains and losses on short-term investments. Accumulated other comprehensive income (loss) consists entirely of unrealized gains and losses from short-term investments as of September 30, 2016 and December 31, 2015. Cash and Cash Equivalents —Cash and cash equivalents consist of bank deposits, certificates of deposit and money market accounts. Cash equivalents are carried at cost which approximates fair value due to their short-term nature and which the Company believes do not have a material exposure to credit risk. The Company considers all highly liquid investments with maturities of three months or less from the date of purchase to be cash equivalents. The Company maintains its cash and cash equivalent balances in the form of money market, savings or operating accounts with financial institutions that management believes are creditworthy. The Company’s cash and cash equivalent accounts, at times, may exceed federally insured limits. The Company has not experienced any losses in such accounts. The Company believes it is not exposed to any significant credit risk on cash and cash equivalents. Short-term Investments —Short-term investments consist of investments in certificates of deposit, agency bonds and United States Treasury securities. Management determines the appropriate classification of these securities at the time they are acquired and evaluates the appropriateness of such classifications at each balance sheet date. The Company classifies its short-term investments as available-for-sale pursuant to Financial Accounting Standards Board (“FASB”) Accounting Standard Codification (“ASC”) 320, Investments—Debt and Equity Securities . Short-term investments are recorded at fair value, with unrealized gains and losses included as a component of accumulated other comprehensive income (loss) in stockholders’ equity and a component of total comprehensive loss in the consolidated statements of comprehensive loss, until realized. Realized gains and losses are included in investment income on a specific-identification basis. There were no realized gains or losses on short-term investments for the three and nine months ended September 30, 2016 and 2015. There was $15 of net unrealized losses and $13 of net unrealized gains on short-term investments for the three and nine months ended September 30, 2016, respectively. There were no net unrealized gains or losses on short-term investments for the three and nine months ended September 30, 2015. The Company reviews short-term investments for other-than-temporary impairment whenever the fair value of a short-term investment is less than the amortized cost and evidence indicates that a short-term investment’s carrying amount is not recoverable within a reasonable period of time. Other-than-temporary impairments of investments are recognized in the consolidated statements of operations if the Company has experienced a credit loss, has the intent to sell the short-term investment, or if it is more likely than not that the Company will be required to sell the short-term investment before recovery of the amortized cost basis. Evidence considered in this assessment includes reasons for the impairment, compliance with the Company’s investment policy, the severity and the duration of the impairment and changes in value subsequent to the end of the period. Short-term investments at September 30, 2016 consist of the following: Cost Basis Unrealized Gains Unrealized Losses Fair Value Current: Certificates of deposit $ 11,899 $ — $ — $ 11,899 United States Treasury securities 42,679 8 (7 ) 42,680 $ 54,578 $ 8 $ (7 ) $ 54,579 Short-term investments at December 31, 2015 consist of the following: Cost Basis Unrealized Gains Unrealized Losses Fair Value Current: Certificates of deposit $ 16,160 $ — $ — $ 16,160 Agency bonds 10,036 — (5 ) 10,031 United States Treasury securities 5,053 — (6 ) 5,047 $ 31,249 $ — $ (11 ) $ 31,238 At September 30, 2016 and December 31, 2015, all short-term investments held by the Company had contractual maturities of less than one year. The Company evaluated its securities for other-than-temporary impairment and determined that no such impairment existed at September 30, 2016 and December 31, 2015. Property and Equipment —Property and equipment are stated at cost. Expenditures for repairs and maintenance are charged to expense as incurred. Upon retirement or sale, the cost of the assets disposed of and the related accumulated depreciation are eliminated from the accounts and any resulting gain or loss is reflected in the consolidated statement of operations. Depreciation and amortization is provided using the straight-line method over the estimated useful lives of the assets. Debt Issuance Costs— Debt issuance costs consist of underwriting discounts and offering-related costs incurred by the Company in connection with the closing of the 2021 Convertible Notes and are included as a direct deduction from the carrying amount of the 2021 Convertible Notes on the Company’s consolidated balance sheets. The Company amortizes debt issuance costs to interest expense over the life of the 2021 Convertible Notes using the effective interest method. (See Note 5). Amortization of debt issuance costs was $82 in the three and nine months ended September 30, 2016. Debt issuance costs incurred in connection with the Company’s notes payable, Convertible Bridge Notes and 2020 Convertible Notes were capitalized at the inception of the notes and amortized over the term of the respective notes using the effective interest rate method. At September 30, 2016 and December 31, 2015, the Company no longer carried the notes payable, Convertible Bridge Notes or 2020 Convertible Notes on its consolidated balance sheet (see Note 5). Amortization of deferred issuance costs was $15 and $107 in the three and nine months ended September 30, 2015, and recorded as a component of interest expense in the accompanying consolidated statements of operations. Research and Development Costs —Research and development costs are charged to expense as incurred and include, but are not limited to: • employee-related expenses including salaries, benefits, travel and stock-based compensation expense for research and development personnel; • expenses incurred under agreements with contract research organizations that conduct clinical and preclinical studies, contract manufacturing organizations and consultants; • costs associated with preclinical and development activities; and • costs associated with regulatory operations. Costs for certain development activities, such as clinical studies, are recognized based on an evaluation of the progress to completion of specific tasks using data such as patient enrollment, clinical site activations, and information provided to the Company by its vendors on their actual costs incurred. Payments for these activities are based on the terms of the individual arrangements, which may differ from the patterns of costs incurred, and are reflected in the financial statements as accrued expenses, or prepaid expenses and other current assets, if the related services have not been provided. Stock-Based Compensation —The Company measures the cost of employee services received in exchange for an award of equity instruments based on the fair value of the award on the grant date. That cost is recognized on a straight-line basis over the period during which the employee is required to provide service in exchange for the award. The fair value of options on the date of grant is calculated using the Black-Scholes option pricing model based on key assumptions such as stock price, expected volatility and expected term. The Company’s estimates of these assumptions are primarily based on third-party valuations, historical data, peer company data and judgment regarding future trends and factors. Compensation cost for stock purchase rights under the employee stock purchase plan is measured and recognized on the date the Company becomes obligated to issue shares of our common stock and is based on the difference between the fair value of the Company’s common stock and the purchase price on such date. The Company accounts for stock options issued to non-employees in accordance with the provisions of the FASB ASC 505-50, Equity-Based Payments to Non-employees Fair Value Measurements —The Company is required to disclose information on all assets and liabilities reported at fair value that enables an assessment of the inputs used in determining the reported fair values. FASB ASC 820, Fair Value Measurements and Disclosures (“ASC 820”), establishes a hierarchy of inputs used when available. Observable inputs are inputs that market participants would use in pricing the asset or liability based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the inputs that market participants would use in pricing the asset or liability, and are developed based on the best information available in the circumstances. The fair value hierarchy applies only to the valuation inputs used in determining the reported fair value of the investments and is not a measure of the investment credit quality. The three levels of the fair value hierarchy are described below: Level 1—Valuations based on unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date. Level 2—Valuations based on quoted prices for similar assets or liabilities in markets that are not active or for which all significant inputs are observable, either directly or indirectly. Level 3—Valuations that require inputs that reflect the Company’s own assumptions that are both significant to the fair value measurement and unobservable. To the extent that valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. The fair value of the Company’s financial instruments, including cash and cash equivalents, prepaid expenses and other current assets, accounts payable and accrued expenses approximate their respective carrying values due to the short-term nature of these instruments. The Company’s assets and liabilities measured at fair value on a recurring basis include its short-term investments, convertible notes redemption rights derivative, 2020 Convertible Notes derivative liability (see Note 8) and 2021 Convertible Notes (see Note 5). Derivative Financial Instruments —All derivatives are recorded as assets or liabilities at fair value, and the changes in fair value are immediately included in earnings, as the derivatives had not been formally designated as hedges for accounting purposes. The Company’s derivative financial instruments include bifurcated embedded derivatives that were identified within the 2020 Convertible Notes and the Convertible Bridge Notes (see Notes 8 and 9). Net Loss Per Share —The Company calculates net loss per share in accordance with FASB ASC 260, Earnings per Share . Basic earnings (loss) per share (“EPS”) is calculated by dividing the net income or loss applicable to common stockholders by the weighted average number of common shares outstanding for the period, without consideration of unissued common stock equivalents. The net loss applicable to common stockholders is determined by the reported net loss for the period and deducting dividends accrued and accretion of preferred stock. Diluted EPS is calculated by adjusting the weighted average common shares outstanding for the dilutive effect of common stock options, warrants, and convertible preferred stock and accrued but unpaid convertible preferred stock dividends. In periods where a net loss is recorded, no effect is given to potentially dilutive securities, as their effect would be anti-dilutive. The following table sets forth the computation of basic and diluted earnings (loss) per share attributable to the Company’s common stockholders: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2016 2015 2016 2015 Numerator: Net loss $ (11,128 ) $ (55,961 ) $ (29,880 ) $ (59,810 ) Accretion and dividends on convertible preferred stock — — — (130 ) Net loss applicable to common stockholders (11,128 ) (55,961 ) (29,880 ) (59,940 ) Denominator: Weighted average common shares outstanding - basic and diluted 26,930,730 22,573,195 26,660,126 15,580,487 Net loss per share applicable to common stockholders - basic and diluted $ (0.41 ) $ (2.48 ) $ (1.12 ) $ (3.85 ) The following common stock equivalents were excluded from the calculation of diluted net loss per share for the periods indicated as including them would have an anti-dilutive effect: Three Months Ended September 30, Nine Months Ended September 30, 2016 2015 2016 2015 Shares issuable upon conversion of the 2021 Convertible Notes 6,483,791 — 6,483,791 — Warrants exerciseable for common stock 56,408 56,408 56,408 56,408 Stock options 2,706,029 1,540,218 2,706,029 1,540,218 Total 9,246,228 1,596,626 9,246,228 1,596,626 Subsequent Events —The Company considers events or transactions that occur after the balance sheet date but prior to the issuance of the financial statements to provide additional evidence relative to certain estimates or to identify matters that require additional disclosure. The Company has completed an evaluation of all subsequent events through the date the financial statements were issued (see Note 10). Recent Accounting Pronouncements —In August 2014, the FASB issued Accounting Standards Update (“ASU”) 2014-15, Presentation of Financial Statements – Going Concern , which provides guidance about management’s responsibility to evaluate whether there is substantial doubt about an entity’s ability to continue as a going concern and to provide related footnote disclosures. The new standard is effective for the Company for the annual period ending after December 15, 2016, and for annual and interim periods thereafter, with early adoption permitted. The Company is currently evaluating the impact of this accounting standard update on the Company’s consolidated financial statements. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) In March 2016, the FASB issued ASU 2016-09, Improvements to Employee Share-Based Payment Accounting, Compensation – Stock Compensation

Property and Equipment

Property and Equipment	9 Months Ended
	Sep. 30, 2016
Property Plant And Equipment [Abstract]
Property and Equipment	3. Property and Equipment At September 30, 2016 and December 31, 2015, the Company’s property and equipment consisted of the following: Useful lives September 30, 2016 December 31, 2015 Office equipment 5 years $ 397 $ 334 Computer hardware and software 3 - 7 years 263 252 Laboratory equipment 5 years 313 43 Leasehold improvements 7 years 445 445 1,418 1,074 Less: accumulated depreciation (373 ) (262 ) Property and equipment, net $ 1,045 $ 812 During the three and nine months ended September 30, 2016, the Company recognized $39 and $111 of depreciation expense, respectively. During the three and nine months ended September 30, 2015, the Company recognized $6 and $7 of depreciation expense, respectively.

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	9 Months Ended
	Sep. 30, 2016
Payables And Accruals [Abstract]
Accrued Expenses and Other Current Liabilities	4. Accrued Expenses and Other Current Liabilities Accrued expenses and other current liabilities at September 30, 2016 and December 31, 2015 consisted of the following: September 30, 2016 December 31, 2015 Compensation and benefits $ 1,326 $ 999 Research and development 1,199 375 Government payable 471 450 Professional fees 397 347 Other 323 337 Total $ 3,716 $ 2,508

Debt

Debt	9 Months Ended
	Sep. 30, 2016
Debt Disclosure [Abstract]
Debt	5. Debt 2021 Convertible Notes On August 5, 2016, the Company issued an aggregate of $50,000 of the 2021 Convertible Notes. On August 30, 2016, the Company issued an additional $2,000 of 2021 Convertible Notes pursuant to the exercise of the underwriters’ overallotment option. The 2021 Convertible Notes have a maturity date of August 1, 2021 (“Maturity Date”), are unsecured and accrue interest at a rate of 5.75% per annum, payable semi-annually on February 1 and August 1 of each year, beginning February 1, 2017. In connection with the issuance of the 2021 Convertible Notes, the Company incurred $3,262 of debt issuance costs which were recorded as a discount on the 2021 Convertible Notes. Each holder of a 2021 Convertible Note (the “Holder”) has the option until the close of business on the second business day immediately preceding the Maturity Date to convert all, or any portion, of the 2021 Convertible Notes held by it at an initial conversion rate of 124.7505 shares of the Company’s common stock per $1 principal amount of 2021 Convertible Notes (the “Conversion Rate”). The Conversion Rate is subject to adjustment from time to time upon the occurrence of certain events, including the issuance of stock dividends and payment of cash dividends. In addition, in certain circumstances, the Conversion Rate will be increased in respect of a Holder’s conversion of 2021 Convertible Notes in connection with the occurrence of one or more corporate events specified in the indenture (as supplemented, the “Indenture”) governing the 2021 Convertible Notes (each such specified corporate event, a “Make-Whole Fundamental Change”) that occurs prior to the Maturity Date (a “Make-Whole Fundamental Change Conversion”) or in respect of a Holder’s voluntary conversion of 2021 Convertible Notes other than in connection with a Make-Whole Fundamental Change (a “Voluntary Conversion”). In connection with a Make-Whole Fundamental Change Conversion or a Voluntary Conversion, the Company will increase the Conversion Rate for the 2021 Convertible Notes surrendered for conversion by a number of additional shares of the Company’s common stock set forth in the Additional Shares Make-Whole Table in the Indenture, based on the applicable Stock Price (as defined in the Indenture) and Effective Date (as defined in the Indenture) for such conversion. The additional shares potentially issuable in connection with a Make-Whole Fundamental Change Conversion or a Voluntary Conversion range from 0 to 24.95 per $1 principal amount of 2021 Convertible Notes, subject to adjustment. If the Stock Price applicable to any conversion is greater than $40.00 per share, the Conversion Rate will not be increased. If the Stock Price applicable to any conversion is less than $6.68 per share, the Conversion Rate in connection with a Make-Whole Fundamental Change Conversion will not be increased but it will be increased by 24.95 shares in connection with a Voluntary Conversion. Upon conversion, Holders of the 2021 Convertible Notes will receive shares of the Company’s common stock and cash in lieu of fractional shares. Upon the occurrence of a Fundamental Change (as defined in the Indenture), each Holder may require the Company to repurchase for cash all or any portion of the 2021 Convertible Notes held by such Holder at a repurchase price equal to 100% of the principal amount thereof, plus accrued and unpaid interest thereon. The Company, at its option, may redeem for cash all or any portion of the 2021 Convertible Notes if the last reported sale price of a share of the Company’s common stock is equal to or greater than 200% of the conversion price for the 2021 Convertible Notes then in effect for at least 20 trading days (whether or not consecutive) during any 30 consecutive trading day period (including the last trading day of such period) ending within the five trading days immediately preceding the date on which the Company provides notice of redemption, at a redemption price equal to 100% of the principal amount of the 2021 Convertible Notes to be redeemed, plus accrued and unpaid interest to, but excluding, the redemption date. If an Event of Default (as defined in the Indenture), other than certain events of bankruptcy, insolvency or reorganization involving the Company, occurs and is continuing, the trustee under the Indenture (the “Trustee”) or the Holders of at least 25% in principal amount of the outstanding 2021 Convertible Notes may declare 100% of the principal of and accrued and unpaid interest, if any, on all of the 2021 Convertible Notes to be due and payable immediately. Upon the occurrence of an Event of Default relating to bankruptcy, insolvency or reorganization involving the Company, 100% of the principal of and accrued and unpaid interest, if any, on all of the 2021 Convertible Notes would become due and payable automatically. Notwithstanding the foregoing, the Indenture provides that, to the extent the Company elects, the sole remedy for an Event of Default relating to certain failures by the Company to comply with certain reporting covenants in the Indenture, will (i) for the first 90 days after the occurrence of such an Event of Default, consist exclusively of the right to receive additional interest on the 2021 Convertible Notes at a rate equal to 0.25% per annum of the principal amount of the 2021 Convertible Notes outstanding for each day during such 90-day period on which such an Event of Default is continuing and (ii) for the period from, and including, the 91st day after the occurrence of such an Event of Default to, and including, the 180th day after the occurrence of such an Event of Default, consist exclusively of the right to receive additional interest on the 2021 Convertible Notes at a rate equal to 0.50% per annum of the principal amount of the 2021 Convertible Notes outstanding for each day during such additional 90-day period on which such an Event of Default is continuing (such additional interest, “Additional Interest”). After 180 days, if such Event of Default is not cured or waived, the 2021 Convertible Notes would be subject to acceleration in accordance with the Indenture. The 2021 Convertible Notes are considered a hybrid financial instrument consisting of a fixed interest rate “host” and various embedded features that required evaluation as potential embedded derivatives under FASB ASC 815, Derivatives and Hedging The issuance costs which were recorded as a discount on the debt are being amortized to interest expense over the life of the 2021 Convertible Notes using the effective interest method. Interest expense related to the 2021 Convertible Notes for the three and nine months ended September 30, 2016, was $533, including $82 related to amortization of the debt discount. The table below summarizes the carrying value of the 2021 Convertible Notes as of September 30, 2016: September 30, 2016 Gross proceeds $ 52,000 Initial value of issuance costs recorded as debt discount (3,262 ) Amortization of debt discount 82 Carrying value $ 48,820 2020 Convertible Notes On February 23, 2015, the Company issued an aggregate of $20,000 of the 2020 Convertible Notes pursuant to its IPO. On March 24, 2015, the Company issued an additional $1,000 of 2020 Convertible Notes pursuant to the exercise of the underwriters’ overallotment option. The 2020 Convertible Notes had a maturity date of February 15, 2020, were unsecured and accrued interest at a rate of 5.0% per annum, payable semi-annually on February 15 and August 15 of each year. In connection with the issuance of the 2020 Convertible Notes, the Company incurred $2,097 of financing costs which were recorded in other assets on the balance sheet. Each holder of a 2020 Convertible Note, had the option to convert all or any portion of such note at an initial conversion rate of 158.7302 shares of the Company’s common stock per $1 principal amount of 2020 Convertible Notes. The conversion rate was subject to adjustment from time to time upon the occurrence of certain events, including the issuance of stock dividends and payment of cash dividends. For any conversion that occurred on or after July 23, 2015, the Company would, in addition to the other consideration payable, make an interest make-whole payment to such converting holder equal to the sum of the present values of the scheduled payments of interest that would have been made on the 2020 Convertible Notes to be converted had such notes remained outstanding from the date of the conversion through the earlier of (i) the date that is three years after the conversion date and (ii) the maturity date, if the 2020 Convertible Notes had not been so converted or otherwise repurchased. Present values for the interest make-whole payment would be calculated using a discount rate equal to 2%. The Company could satisfy its obligation to pay any interest make-whole payment, at its election, in cash, shares of common stock or a combination thereof. The 2020 Convertible Notes were convertible, at the holder’s option, upon a fundamental change, as defined in the indenture. If a holder elected to convert its notes upon a fundamental change, the Company would increase the conversion rate for the 2020 convertible notes so surrendered for conversion by a number of additional shares of common stock by which the conversion rate would have increased per $1 principal amount of notes for each stock price and make-whole fundamental change effective date as set forth in the indenture. The additional shares ranged from 7.9364 to 0. Upon a fundamental change, each holder would have the right to require the Company to repurchase for cash all of such holder’s notes, or any portion thereof that is equal to $1 or an integral multiple of $1. The repurchase price of the 2020 Convertible Notes would equal 100% of the principal amount thereof, plus accrued and unpaid interest thereon. However, if the repurchase occurred after a regular record date for an interest payment, but before the distribution date of that interest payment, the holder would receive the regular interest payment and the repurchase price would equal 100% of the principal amount of the 2020 Convertible Notes to be repurchased. The 2020 Convertible Notes were redeemable at the holder’s option upon an event of default. If an event of default (other than certain events of bankruptcy, insolvency or reorganization involving the Company) occurred and was continuing, the trustee by notice to the Company, or the holders of at least 25% in principal amount of the outstanding notes by written notice to the Company and the trustee, could declare 100% of the principal and accrued and unpaid interest, if any, on all of the 2020 Convertible Notes to be due and payable immediately. Upon the occurrence of certain events of default relating to bankruptcy, insolvency or reorganization involving the Company, 100% of the principal and accrued and unpaid interest, if any, on all of the 2020 Convertible Notes would become due and payable automatically. The indenture provided that, to the extent the Company elected and for up to 180 days, the sole remedy for an event of default relating to certain failures by the Company to comply with certain reporting covenants in the indenture, consisted exclusively of the right to receive additional interest on the 2020 Convertible Notes. The additional interest consisted of interest at an additional rate of 0.25% per annum for the first 90 days after the event of default. For the 91st to 180th day after the event of default, the additional interest would consist of interest at an additional rate of 0.50% per annum. After 180 days, if the event of default was not cured or waived, the 2020 Convertible Notes were subject to acceleration as provided in Section 6.02 of the indenture. The Company determined that the conversion option, interest make-whole payments and the additional interest were embedded derivatives that required bifurcation and separate accounting under FASB ASC 815, Derivatives and Hedging The Company estimated the fair value of the additional interest using an income approach, specifically, the risk-neutral debt valuation method that is used to derive the value of a debt instrument using the expected cash flows and the risk-free rate. The significant assumptions used in estimating the expected cash flows were: the market yield used to determine the risk-neutral probability of default and the expected recovery rate upon default. The Company recorded $11,850 as the fair value of the combined embedded derivative liability on February 23, 2015, with a corresponding amount recorded as a discount to the 2020 Convertible Notes, related to the initial issuance of the 2020 Convertible Notes. The Company recorded approximately $573 of additional derivative liability and discount to the 2020 Convertible Notes as the fair value of the combined embedded derivative on March 24, 2015, upon the issuance of additional 2020 Convertible Notes for the exercise of the underwriters’ overallotment option. The deferred financing costs and the debt discount were recorded in other assets and were being amortized to interest expense over the life of the 2020 Convertible Notes using the effective interest method. Changes in the fair value of the combined embedded derivative liability were recorded in earnings in the period in which the changes occurred. In July and August 2015, holders of all $21,000 principal amount of the 2020 Convertible Notes elected to convert the principal into 3,333,319 shares of common stock in accordance with the terms of the 2020 Convertible Notes. In addition, the interest make-whole payment was settled with shares of common stock, at the election of the Company, resulting in the issuance of 530,072 additional shares of common stock. As of the conversion dates, the fair value of the combined embedded derivative liability was determined to be $55,216. The change in the estimated fair value of the combined embedded derivative liability from June 30, 2015, to the conversion dates and for the three months ended September 30, 2015, was $46,649, and for the nine months ended September 30, 2015, was $42,793. In addition, the Company recorded a charge of $3,716 in the three and nine months ended September 30, 2015, related to the extinguishment of the 2020 Convertible Notes. As of September 30, 2015, all $21,000 of the 2020 Convertible Notes were extinguished. Interest expense related to the 2020 Convertible Notes for the three months ended September 30, 2015, was $189, including $15 related to amortization of the issuance costs and $90 related to amortization of the debt discount. Interest expense related to the 2020 Convertible Notes for the nine months ended September 30, 2015, was $963, including $74 related to amortization of the issuance costs and $440 related to amortization of the debt discount. Convertible Bridge Notes In December 2014, the Company sold an aggregate of $2,000 of subordinated convertible promissory notes to existing stockholders (the “Convertible Bridge Notes”). The Convertible Bridge Notes were scheduled to mature on June 30, 2015 and accrued interest at the rate of 8% per annum and were subordinate to all other senior indebtedness of the Company. Upon the closing of an initial public offering of common stock of at least $40,000 in gross proceeds, all outstanding principal and accrued interest thereon would automatically convert into common stock at the initial public offering price. Pursuant to the IPO in February 2015, the Convertible Bridge Notes were converted into 337,932 shares of common stock based upon the IPO common share offering price of $6.00 per share. During the nine months ended September 30, 2015, the Company reflected as interest expense related to the Convertible Bridge Notes (i) $23 related to the 8% coupon rate and (ii) $128 of amortization of the initial fair value of the redemption rights derivative and issuance costs. In connection with the conversion of the Convertible Bridge Notes into common stock, the Company recorded a (i) a $480 gain in change in fair value of the of the Convertible Bridge Notes redemption rights derivative from the write off of the derivative and (ii) a loss on extinguishment of debt of $360 from the acceleration of the unamortized balance of the debt discount and issuance costs. Notes Payable On June 28, 2013, the Company entered into two Loan and Security Agreements (the “Loan Agreements” or “Loans”) with two financial entities (the “Lenders”) pursuant to which the Company issued Loans for $3,500 to each lender and received proceeds of $6,915 net of costs and fees payable to the lenders. The Loans bore interest at a rate per annum of 11.0%. The Loans would mature on October 1, 2016 and required interest-only payments for the initial 12 months and thereafter required repayment of the principal balance with interest in 27 monthly installments. Also, upon full repayment or maturity of the Loans, the Lenders would be due a termination payment of 3.0% of the initial principal amount of the Loans, or $210 (the “Loan Termination Payment”). In connection with the Loan Agreements, the Company issued to the Lenders fully-vested warrants to purchase either, at the election of the warrant holder, (i) 228,906 shares of the Company’s Series AA preferred stock at an exercise price of $1.529 per share, or (ii) $350 of stock in the next round stock, as defined in the Loan Agreements, at a price that is the lowest effective price per share that is offered in the next round. The warrants expire on the earlier of (i) ten years after the date of grant, or (ii) immediately prior to an acquisition transaction, as defined in the warrants. The Company determined that the warrants should initially be classified as a liability based upon the nature of the underlying Series AA preferred stock. In connection with the Company’s IPO in February 2015, the Company exercised its right to terminate the Loan Agreements by paying the $5,347 principal balance due, the $210 Loan Termination Payment, a $160 prepayment fee calculated as 3% of the principal balance due at the time of the termination, plus $23 of interest accrued from February 1, 2015 through the payoff date. The Company made a scheduled principal payment of $243 in January 2015. For the nine months ended September 30, 2015, interest expense related to the Loan Agreements was $115, including $26 related to accretion of the debt discount and termination payment. Additionally, in the nine months ended September 30, 2015, the Company recorded a charge for loss on extinguishment of debt of $322 related to the write-off of the unamortized debt discount. Subsequent to the Company’s IPO, the warrants issued to the lenders became exercisable for 56,408 shares of common stock at $6.204 per share. The Company calculated the fair value of the warrants at the IPO date using a Black Scholes model using the following assumptions: a fair value of $6.00 per share (the IPO price of the Company’s common stock), 8.4 years to maturity, 1.70% risk-free rate, and 60% volatility. The Company determined the fair value of the warrant liability at the IPO date to be $215 and recorded a gain on change in fair value of warrant liabilities of $267 in the statement of operations for the nine months ended September 30, 2015. The Company determined that subsequent to this change, the warrants were exercisable at a fixed number of shares of common stock and qualified for equity classification under the accounting guidance, and the fair value of the $215 was reclassified to additional paid-in capital as of the IPO date.

Equity

Equity	9 Months Ended
	Sep. 30, 2016
Equity [Abstract]
Equity	6. Equity Authorized Shares As of September 30, 2016, the Company’s authorized capital stock consisted of 120,000,000 shares of common stock, par value $0.01 per share, and 5,000,000 shares of undesignated preferred stock, par value $0.001 per share. Preferred Stock During 2014, the Company modified the terms of 558,862 shares of Series X preferred stock such that the Company’s repurchase right relative to those shares expired upon consummation of the IPO. The Company estimated the fair value of the modified award at the modification date to be $950 and recognized this amount as stock-based compensation expense upon completion of the IPO in the nine months ended September 30, 2015. Common Stock All preferences, voting powers, relative, participating, optional, or other specific rights and privileges, limitations, or restrictions of the common stock are expressly subject to those that may be fixed with respect to any shares of preferred stock. Common stockholders are entitled to one vote per share, and to receive dividends, when and if declared by the Company’s board of directors. There were no shares sold pursuant to the ATM during the three months ended September 30, 2016. During the nine months ended September 30, 2016, the Company sold 482,689 shares of common stock and received gross and net proceeds of $4,401 and $3,997, respectively, pursuant to the ATM. At September 30, 2016, $45,599 was available for sale of common stock under the ATM. At September 30, 2016 and December 31, 2015, there were 26,930,730 and 26,423,394 shares of common stock outstanding respectively. 2014 Stock Option and Incentive Plan In August 2014, the Company’s board of directors adopted the 2014 Stock Option and Incentive Plan (the “2014 Plan”) for the issuance of incentive and non-qualified stock options, restricted stock, and other equity awards, all for common stock, as determined by the board of directors to employees, officers, directors, consultants, and advisors of the Company and its subsidiaries. Pursuant to the provisions of the 2014 Plan and approval by the board of directors, on January 1, 2016 an additional 1,056,936 shares were added to the 2014 Plan representing 4% of total common shares issued and outstanding at December 31, 2015. There were 508,034 shares available for issuance under the 2014 Plan as of September 30, 2016. The 2014 Plan expires in August 2024. In the three months ended September 30, 2016, the Company recorded aggregate stock-based compensation expense of $783 for stock options under the 2014 Plan: $438 in general and administrative expense and $345 in research and development expense. In the three months ended September 30, 2015, the Company recorded an aggregate stock-based compensation expense of $374 for stock options under the 2014 Plan: $228 in general and administrative expense and $146 in research and development expense. In the nine months ended September 30, 2016, the Company recorded aggregate stock-based compensation expense of $1,935 for stock options under the 2014 Plan: $1,077 in general and administrative expense and $858 in research and development expense. In the nine months ended September 30, 2015, the Company recorded an aggregate stock-based compensation expense of $982 for stock options under the 2014 Plan: $544 in general and administrative expense and $438 in research and development expense. During the nine months ended September 30, 2016, the board of directors granted a total of 1,121,500 ten-year term stock options to employees and directors of the Company. The fair value of each stock option granted was estimated on the grant date using a Black-Scholes stock option pricing model based on the following assumptions: an expected term of 5.31 to 6.08 years; expected stock price volatility of 76.9% to 79.2%, a risk free rate of 1.20% to 1.90%, and a dividend yield of 0%. The Company will recognize $5,790 of stock-based compensation expense for these stock options on a straight-line basis commencing upon the grant dates through the final vesting dates. The following table summarizes activity for the nine months ended September 30, 2016 under the 2014 Plan: Number of Shares Weighted Average Exercise Price Per Share Aggregate Intrinsic Value Options outstanding at December 31, 2015 1,620,760 $ 4.95 $ 10,339 Granted 1,121,500 $ 7.81 Exercised (18,857 ) $ 4.67 Cancelled (28,000 ) $ 6.79 Options outstanding at September 30, 2016 2,695,403 $ 6.12 $ 9,169 Options exercisable at September 30, 2016 753,207 $ 4.72 $ 3,588 Weighted-average years remaining on contractual life 8.82 Unrecognized compensation cost related to non-vested stock options $ 8,440 The weighted-average fair value of all stock options granted for the three and nine months ended September 30, 2016 was $5.27 per share and $5.25 per share, respectively. Aggregate intrinsic value at September 30, 2016, is based on $9.48 per share, the closing price of common stock on September 30, 2016. Aggregate intrinsic value at December 31, 2015, is based on $11.33 per share, the closing price of common stock on December 31, 2015. 2004 Stock Option and Incentive Plan The Company has outstanding stock options pursuant to its 2004 Stock Option and Incentive Plan (the “2004 Plan”). The 2004 Plan has expired but remains effective for all outstanding options under the 2004 Plan. The following table summarizes activity for the nine months ended September 30, 2016 under the 2004 Plan: Number of Shares Weighted Average Exercise Price Per Share Aggregate Intrinsic Value Options outstanding at December 31, 2015 10,917 $ 40.58 $ — Exercised — $ — $ — Expired — $ — $ — Cancelled (291 ) $ 40.58 $ — Options outstanding at September 30, 2016 10,626 $ 40.58 $ — Options exercisable at September 30, 2016 10,626 $ 40.58 $ — Weighted-average years remaining on contractual life 1.49 Unrecognized compensation cost related to non-vested stock options $ — The exercise prices exceed the $9.48 per share closing price of common stock on September 30, 2016, therefore there is no intrinsic value of the outstanding 2004 Plan stock options. Employee Stock Purchase Plan In November 2014, the Company’s board of directors adopted and the stockholders approved the 2014 Employee Stock Purchase Plan (“ESPP”). The ESPP provides that the number of shares reserved and available for issuance under the ESPP shall be cumulatively increased each January 1, beginning on January 1, 2016, by the lesser of (i) 600,000 shares of common stock or (ii) the number of shares necessary to set the number of shares of Common Stock under the Plan at 1% percent of the outstanding number of shares as of January 1 of the applicable year. However, the board of directors reserves the right to determine that there will be no increase for any year or that any increase will be for a lesser number of shares. As of January 1, 2016, 117,100 shares were added to the ESPP. As of September 30, 2016, there were 258,443 shares available for issuance under the ESPP. On May 31, 2016, 5,790 shares of common stock were purchased pursuant to the ESPP, resulting in proceeds to the Company of $45. The Company recorded $23 and $43 of stock-based compensation expense pursuant to the ESPP during the three and nine months ended September 30, 2016, respectively.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2016
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	7. Commitments and Contingencies Operating leases In May 2015, the Company entered into a lease agreement (the “Office Lease”) for its headquarters in Lexington, Massachusetts. The Company occupied this space in September 2015, at which time its rental obligations commenced. The Company recorded $445 as leasehold improvements for costs incurred to build out the space, and is amortizing those costs to facilities expense over the term of the lease. Rent expense is recognized on a straight-line basis at the average monthly rent over the term of the lease. Deferred rent is included in other current and long-term liabilities on the Company’s consolidated balance sheets. In February 2016, the Company signed an amendment to the Office Lease, whereby it agreed to rent additional space (the “Lease Amendment”). The Company occupied the additional space on July 1, 2016. The terms of the Lease Amendment follow the terms of the Office Lease. Rent expense was $66 and $190 for the three and nine months ended September 30, 2016, respectively. Rent expense was $43 and $78 for the three and nine months ended September 30, 2015, respectively. As of September 30, 2016, the aggregate annual commitments pursuant to the Office Lease and the Lease Amendment are as follows: Year Amount 2016 $ 52 2017 402 2018 411 2019 421 2020 430 Thereafter 959 Total $ 2,675 Indemnification Arrangements As permitted under Delaware law, the Company’s bylaws provide that the Company will indemnify any director, officer, employee or agent of the Company or anyone serving in these capacities. The maximum potential amount of future payments the Company could be required to pay is unlimited. The Company has insurance that reduces its monetary exposure and would enable it to recover a portion of any future amounts paid. As a result, the Company believes that the estimated fair value of these indemnification commitments is minimal. Throughout the normal course of business, the Company has agreements with vendors that provide goods and services required by the Company to run its business. In some instances, vendor agreements include language that requires the Company to indemnify the vendor from certain damages caused by the Company’s use of the vendor’s goods and/or services. The Company has insurance that would allow it to recover a portion of any future amounts that could arise from these indemnifications. As a result, the Company believes that the estimated fair value of these indemnification commitments is minimal.

Fair Value of Financial Measure

Fair Value of Financial Measurements	9 Months Ended
	Sep. 30, 2016
Fair Value Disclosures [Abstract]
Fair Value of Financial Measurements	8. Fair Value of Financial Measurements Items measured at fair value on a recurring basis are short-term investments, convertible preferred stock warrant liabilities, the Convertible Bridge Notes redemption rights derivative and the 2020 Convertible Notes derivative liability. The following table sets forth the Company’s financial instruments that were measured at fair value on a recurring basis by level within the fair value hierarchy: Fair Value Measurements at September 30, 2016 Total Level 1 Level 2 Level 3 Assets: Certificates of deposit $ 11,899 $ — $ 11,899 $ — United States Treasury securities 42,680 42,680 — — Short-term investments $ 54,579 $ 42,680 $ 11,899 $ — Fair Value Measurements at December 31, 2015 Total Level 1 Level 2 Level 3 Assets: Certificates of deposit $ 16,160 $ — $ 16,160 $ — Agency bonds 10,031 — 10,031 — United States Treasury securities 5,047 5,047 — — Short-term investments $ 31,238 $ 5,047 $ 26,191 $ — Short-term investments The Company classifies its United States Treasury securities as Level 1 assets under the fair value hierarchy as these assets have been valued using quoted market prices in active markets without any valuation adjustment. The Company classifies its certificates of deposit as Level 2 assets under the fair value hierarchy, as there are no quoted market prices in active markets, and its agency bonds as Level 2 assets under the fair value hierarchy, as these assets are not always valued daily using quoted market prices in active markets. Convertible debt redemption rights derivative In December 2014, the Company issued the Convertible Bridge Notes which contained a redemption rights derivative required separate accounting and was valued using a single income valuation approach. As of December 31, 2014, the fair value of the embedded derivative was $480. Pursuant to the IPO, the Convertible Bridge Notes were converted into 337,932 shares of common stock and the $480 fair value of the embedded derivative was written off and reflected a gain on the change in fair value of Convertible Bridge Notes redemption rights derivative in the nine months ended September 30, 2015. 2020 Convertible Notes derivative liability The fair value methodologies related to the 2020 Convertible Notes derivative liability are discussed in Note 5.

Derivative Financial Instrument

Derivative Financial Instruments	9 Months Ended
	Sep. 30, 2016
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Derivative Financial Instruments	9. Derivative Financial Instruments The Company determined that certain embedded features related to the 2020 Convertible Notes and the Convertible Bridge Notes are derivative financial instruments. The effect of derivative instruments not designated as hedging instruments on the statement of operations for the three and nine months ended September 30, 2015 consist of the following: Location of gain or loss Amount of gain or (loss) recognized in income on derivative financial instrument Derivative financial instruments not designated as hedging instruments recognized in income on derivative financial instrument For the Three Months Ended September 30, 2015 For the Nine Months Ended September 30, 2015 2020 Convertible Notes derivative liability Change in fair value of 2020 Convertible Notes derivative liability $ (46,649 ) $ (42,793 ) Convertible Bridge Notes Change in fair value of Convertible Bridge Notes redemption rights derivative $ — $ 480 See Notes 5 and 8 for additional discussion regarding the accounting for and valuation of these derivative financial instruments.

Subsequent Event

Subsequent Event	9 Months Ended
	Sep. 30, 2016
Subsequent Events [Abstract]
Subsequent Event	10. Subsequent Event In October 2016, the Company entered into a Transition Agreement with its former Chief Scientific Officer, William K. McVicar, Ph.D. (the “Transition Agreement”). Pursuant to the terms of the Transition Agreement, Dr. McVicar will remain an employee of the Company as a Senior Advisor for a six-month period ending April 4, 2017 and for twelve months thereafter will receive his salary and medical benefits at the same rate in effect as of the date of the Transition Agreement. The Company expects to pay an aggregate of approximately $750 related to the Transition Agreement, including Dr. McVicar’s bonus through his termination date.

Significant Accounting Polici17

Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2016
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation —The Company’s interim financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). In the opinion of management, the Company has made all necessary adjustments, which include normal recurring adjustments necessary for a fair statement of the Company’s financial position and results of operations for the interim periods presented. Certain information and disclosures normally included in the annual financial statements prepared in accordance with GAAP have been condensed or omitted. These interim financial statements should be read in conjunction with the audited financial statements and accompanying notes for the year ended December 31, 2015 included in the Company’s Annual Report on Form 10-K. The results for the three and nine month periods ended September 30, 2016 are not necessarily indicative of the results to be expected for a full year, any other interim periods or any future year or period. The accompanying consolidated financial statements include our accounts and those of our wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation.
Segment Reporting	Segment Reporting —Operating segments are defined as components of an enterprise about which separate discrete information is available for evaluation by the chief operating decision maker, or decision-making group, in deciding how to allocate resources and in assessing performance. The Company views its operations and manages its business in one operating segment.
Use of Estimates	Use of Estimates —The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting period. Actual results could differ from these estimates. Significant items subject to such estimates and assumptions include the valuation of stock options used for the calculation of stock-based compensation, fair value of warrant liabilities and other derivative financial instruments, and calculation of accruals related to research and clinical development.
Comprehensive income (loss)	Comprehensive income (loss)— Comprehensive income (loss) is defined as the change in equity of a business enterprise during a period from transactions, and other events and circumstances from non-owner sources, and currently consists of net loss and changes in unrealized gains and losses on short-term investments. Accumulated other comprehensive income (loss) consists entirely of unrealized gains and losses from short-term investments as of September 30, 2016 and December 31, 2015.
Cash and Cash Equivalents	Cash and Cash Equivalents —Cash and cash equivalents consist of bank deposits, certificates of deposit and money market accounts. Cash equivalents are carried at cost which approximates fair value due to their short-term nature and which the Company believes do not have a material exposure to credit risk. The Company considers all highly liquid investments with maturities of three months or less from the date of purchase to be cash equivalents. The Company maintains its cash and cash equivalent balances in the form of money market, savings or operating accounts with financial institutions that management believes are creditworthy. The Company’s cash and cash equivalent accounts, at times, may exceed federally insured limits. The Company has not experienced any losses in such accounts. The Company believes it is not exposed to any significant credit risk on cash and cash equivalents.
Short-term Investments	Short-term Investments —Short-term investments consist of investments in certificates of deposit, agency bonds and United States Treasury securities. Management determines the appropriate classification of these securities at the time they are acquired and evaluates the appropriateness of such classifications at each balance sheet date. The Company classifies its short-term investments as available-for-sale pursuant to Financial Accounting Standards Board (“FASB”) Accounting Standard Codification (“ASC”) 320, Investments—Debt and Equity Securities . Short-term investments are recorded at fair value, with unrealized gains and losses included as a component of accumulated other comprehensive income (loss) in stockholders’ equity and a component of total comprehensive loss in the consolidated statements of comprehensive loss, until realized. Realized gains and losses are included in investment income on a specific-identification basis. There were no realized gains or losses on short-term investments for the three and nine months ended September 30, 2016 and 2015. There was $15 of net unrealized losses and $13 of net unrealized gains on short-term investments for the three and nine months ended September 30, 2016, respectively. There were no net unrealized gains or losses on short-term investments for the three and nine months ended September 30, 2015. The Company reviews short-term investments for other-than-temporary impairment whenever the fair value of a short-term investment is less than the amortized cost and evidence indicates that a short-term investment’s carrying amount is not recoverable within a reasonable period of time. Other-than-temporary impairments of investments are recognized in the consolidated statements of operations if the Company has experienced a credit loss, has the intent to sell the short-term investment, or if it is more likely than not that the Company will be required to sell the short-term investment before recovery of the amortized cost basis. Evidence considered in this assessment includes reasons for the impairment, compliance with the Company’s investment policy, the severity and the duration of the impairment and changes in value subsequent to the end of the period. Short-term investments at September 30, 2016 consist of the following: Cost Basis Unrealized Gains Unrealized Losses Fair Value Current: Certificates of deposit $ 11,899 $ — $ — $ 11,899 United States Treasury securities 42,679 8 (7 ) 42,680 $ 54,578 $ 8 $ (7 ) $ 54,579 Short-term investments at December 31, 2015 consist of the following: Cost Basis Unrealized Gains Unrealized Losses Fair Value Current: Certificates of deposit $ 16,160 $ — $ — $ 16,160 Agency bonds 10,036 — (5 ) 10,031 United States Treasury securities 5,053 — (6 ) 5,047 $ 31,249 $ — $ (11 ) $ 31,238 At September 30, 2016 and December 31, 2015, all short-term investments held by the Company had contractual maturities of less than one year. The Company evaluated its securities for other-than-temporary impairment and determined that no such impairment existed at September 30, 2016 and December 31, 2015.
Property and Equipment	Property and Equipment —Property and equipment are stated at cost. Expenditures for repairs and maintenance are charged to expense as incurred. Upon retirement or sale, the cost of the assets disposed of and the related accumulated depreciation are eliminated from the accounts and any resulting gain or loss is reflected in the consolidated statement of operations. Depreciation and amortization is provided using the straight-line method over the estimated useful lives of the assets.
Debt Issuance Costs	Debt Issuance Costs— Debt issuance costs consist of underwriting discounts and offering-related costs incurred by the Company in connection with the closing of the 2021 Convertible Notes and are included as a direct deduction from the carrying amount of the 2021 Convertible Notes on the Company’s consolidated balance sheets. The Company amortizes debt issuance costs to interest expense over the life of the 2021 Convertible Notes using the effective interest method. (See Note 5). Amortization of debt issuance costs was $82 in the three and nine months ended September 30, 2016. Debt issuance costs incurred in connection with the Company’s notes payable, Convertible Bridge Notes and 2020 Convertible Notes were capitalized at the inception of the notes and amortized over the term of the respective notes using the effective interest rate method. At September 30, 2016 and December 31, 2015, the Company no longer carried the notes payable, Convertible Bridge Notes or 2020 Convertible Notes on its consolidated balance sheet (see Note 5). Amortization of deferred issuance costs was $15 and $107 in the three and nine months ended September 30, 2015, and recorded as a component of interest expense in the accompanying consolidated statements of operations.
Research and Development Costs	Research and Development Costs —Research and development costs are charged to expense as incurred and include, but are not limited to: • employee-related expenses including salaries, benefits, travel and stock-based compensation expense for research and development personnel; • expenses incurred under agreements with contract research organizations that conduct clinical and preclinical studies, contract manufacturing organizations and consultants; • costs associated with preclinical and development activities; and • costs associated with regulatory operations. Costs for certain development activities, such as clinical studies, are recognized based on an evaluation of the progress to completion of specific tasks using data such as patient enrollment, clinical site activations, and information provided to the Company by its vendors on their actual costs incurred. Payments for these activities are based on the terms of the individual arrangements, which may differ from the patterns of costs incurred, and are reflected in the financial statements as accrued expenses, or prepaid expenses and other current assets, if the related services have not been provided.
Stock-Based Compensation	Stock-Based Compensation —The Company measures the cost of employee services received in exchange for an award of equity instruments based on the fair value of the award on the grant date. That cost is recognized on a straight-line basis over the period during which the employee is required to provide service in exchange for the award. The fair value of options on the date of grant is calculated using the Black-Scholes option pricing model based on key assumptions such as stock price, expected volatility and expected term. The Company’s estimates of these assumptions are primarily based on third-party valuations, historical data, peer company data and judgment regarding future trends and factors. Compensation cost for stock purchase rights under the employee stock purchase plan is measured and recognized on the date the Company becomes obligated to issue shares of our common stock and is based on the difference between the fair value of the Company’s common stock and the purchase price on such date. The Company accounts for stock options issued to non-employees in accordance with the provisions of the FASB ASC 505-50, Equity-Based Payments to Non-employees
Fair Value Measurements	Fair Value Measurements —The Company is required to disclose information on all assets and liabilities reported at fair value that enables an assessment of the inputs used in determining the reported fair values. FASB ASC 820, Fair Value Measurements and Disclosures (“ASC 820”), establishes a hierarchy of inputs used when available. Observable inputs are inputs that market participants would use in pricing the asset or liability based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the inputs that market participants would use in pricing the asset or liability, and are developed based on the best information available in the circumstances. The fair value hierarchy applies only to the valuation inputs used in determining the reported fair value of the investments and is not a measure of the investment credit quality. The three levels of the fair value hierarchy are described below: Level 1—Valuations based on unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date. Level 2—Valuations based on quoted prices for similar assets or liabilities in markets that are not active or for which all significant inputs are observable, either directly or indirectly. Level 3—Valuations that require inputs that reflect the Company’s own assumptions that are both significant to the fair value measurement and unobservable. To the extent that valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. The fair value of the Company’s financial instruments, including cash and cash equivalents, prepaid expenses and other current assets, accounts payable and accrued expenses approximate their respective carrying values due to the short-term nature of these instruments. The Company’s assets and liabilities measured at fair value on a recurring basis include its short-term investments, convertible notes redemption rights derivative, 2020 Convertible Notes derivative liability (see Note 8) and 2021 Convertible Notes (see Note 5).
Derivative Financial Instruments	Derivative Financial Instruments —All derivatives are recorded as assets or liabilities at fair value, and the changes in fair value are immediately included in earnings, as the derivatives had not been formally designated as hedges for accounting purposes. The Company’s derivative financial instruments include bifurcated embedded derivatives that were identified within the 2020 Convertible Notes and the Convertible Bridge Notes (see Notes 8 and 9).
Net Loss Per Share	Net Loss Per Share —The Company calculates net loss per share in accordance with FASB ASC 260, Earnings per Share . Basic earnings (loss) per share (“EPS”) is calculated by dividing the net income or loss applicable to common stockholders by the weighted average number of common shares outstanding for the period, without consideration of unissued common stock equivalents. The net loss applicable to common stockholders is determined by the reported net loss for the period and deducting dividends accrued and accretion of preferred stock. Diluted EPS is calculated by adjusting the weighted average common shares outstanding for the dilutive effect of common stock options, warrants, and convertible preferred stock and accrued but unpaid convertible preferred stock dividends. In periods where a net loss is recorded, no effect is given to potentially dilutive securities, as their effect would be anti-dilutive. The following table sets forth the computation of basic and diluted earnings (loss) per share attributable to the Company’s common stockholders: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2016 2015 2016 2015 Numerator: Net loss $ (11,128 ) $ (55,961 ) $ (29,880 ) $ (59,810 ) Accretion and dividends on convertible preferred stock — — — (130 ) Net loss applicable to common stockholders (11,128 ) (55,961 ) (29,880 ) (59,940 ) Denominator: Weighted average common shares outstanding - basic and diluted 26,930,730 22,573,195 26,660,126 15,580,487 Net loss per share applicable to common stockholders - basic and diluted $ (0.41 ) $ (2.48 ) $ (1.12 ) $ (3.85 ) The following common stock equivalents were excluded from the calculation of diluted net loss per share for the periods indicated as including them would have an anti-dilutive effect: Three Months Ended September 30, Nine Months Ended September 30, 2016 2015 2016 2015 Shares issuable upon conversion of the 2021 Convertible Notes 6,483,791 — 6,483,791 — Warrants exerciseable for common stock 56,408 56,408 56,408 56,408 Stock options 2,706,029 1,540,218 2,706,029 1,540,218 Total 9,246,228 1,596,626 9,246,228 1,596,626
Subsequent Events	Subsequent Events —The Company considers events or transactions that occur after the balance sheet date but prior to the issuance of the financial statements to provide additional evidence relative to certain estimates or to identify matters that require additional disclosure. The Company has completed an evaluation of all subsequent events through the date the financial statements were issued (see Note 10).
Recent Accounting Pronouncements	Recent Accounting Pronouncements —In August 2014, the FASB issued Accounting Standards Update (“ASU”) 2014-15, Presentation of Financial Statements – Going Concern , which provides guidance about management’s responsibility to evaluate whether there is substantial doubt about an entity’s ability to continue as a going concern and to provide related footnote disclosures. The new standard is effective for the Company for the annual period ending after December 15, 2016, and for annual and interim periods thereafter, with early adoption permitted. The Company is currently evaluating the impact of this accounting standard update on the Company’s consolidated financial statements. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) In March 2016, the FASB issued ASU 2016-09, Improvements to Employee Share-Based Payment Accounting, Compensation – Stock Compensation

Significant Accounting Polici18

Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2016
Accounting Policies [Abstract]
Schedule of Short-term Investment	Short-term investments at September 30, 2016 consist of the following: Cost Basis Unrealized Gains Unrealized Losses Fair Value Current: Certificates of deposit $ 11,899 $ — $ — $ 11,899 United States Treasury securities 42,679 8 (7 ) 42,680 $ 54,578 $ 8 $ (7 ) $ 54,579 Short-term investments at December 31, 2015 consist of the following: Cost Basis Unrealized Gains Unrealized Losses Fair Value Current: Certificates of deposit $ 16,160 $ — $ — $ 16,160 Agency bonds 10,036 — (5 ) 10,031 United States Treasury securities 5,053 — (6 ) 5,047 $ 31,249 $ — $ (11 ) $ 31,238
Schedule of Computation of Basic and Diluted Earnings (Loss) Per Share	The following table sets forth the computation of basic and diluted earnings (loss) per share attributable to the Company’s common stockholders: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2016 2015 2016 2015 Numerator: Net loss $ (11,128 ) $ (55,961 ) $ (29,880 ) $ (59,810 ) Accretion and dividends on convertible preferred stock — — — (130 ) Net loss applicable to common stockholders (11,128 ) (55,961 ) (29,880 ) (59,940 ) Denominator: Weighted average common shares outstanding - basic and diluted 26,930,730 22,573,195 26,660,126 15,580,487 Net loss per share applicable to common stockholders - basic and diluted $ (0.41 ) $ (2.48 ) $ (1.12 ) $ (3.85 )
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	The following common stock equivalents were excluded from the calculation of diluted net loss per share for the periods indicated as including them would have an anti-dilutive effect: Three Months Ended September 30, Nine Months Ended September 30, 2016 2015 2016 2015 Shares issuable upon conversion of the 2021 Convertible Notes 6,483,791 — 6,483,791 — Warrants exerciseable for common stock 56,408 56,408 56,408 56,408 Stock options 2,706,029 1,540,218 2,706,029 1,540,218 Total 9,246,228 1,596,626 9,246,228 1,596,626

Property and Equipment (Tables)

Property and Equipment (Tables)	9 Months Ended
	Sep. 30, 2016
Property Plant And Equipment [Abstract]
Schedule of Property and Equipment	At September 30, 2016 and December 31, 2015, the Company’s property and equipment consisted of the following: Useful lives September 30, 2016 December 31, 2015 Office equipment 5 years $ 397 $ 334 Computer hardware and software 3 - 7 years 263 252 Laboratory equipment 5 years 313 43 Leasehold improvements 7 years 445 445 1,418 1,074 Less: accumulated depreciation (373 ) (262 ) Property and equipment, net $ 1,045 $ 812

Accrued Expenses and Other Cu20

Accrued Expenses and Other Current Liabilities (Tables)	9 Months Ended
	Sep. 30, 2016
Payables And Accruals [Abstract]
Schedule of Accrued Expenses and Other Current Liabilities	Accrued expenses and other current liabilities at September 30, 2016 and December 31, 2015 consisted of the following: September 30, 2016 December 31, 2015 Compensation and benefits $ 1,326 $ 999 Research and development 1,199 375 Government payable 471 450 Professional fees 397 347 Other 323 337 Total $ 3,716 $ 2,508

Debt (Tables)

Debt (Tables)	9 Months Ended
	Sep. 30, 2016
Debt Disclosure [Abstract]
Summary of Carrying Value of Convertible Notes	The table below summarizes the carrying value of the 2021 Convertible Notes as of September 30, 2016: September 30, 2016 Gross proceeds $ 52,000 Initial value of issuance costs recorded as debt discount (3,262 ) Amortization of debt discount 82 Carrying value $ 48,820

Equity (Tables)

Equity (Tables)	9 Months Ended
	Sep. 30, 2016
Equity [Abstract]
Summary of Stock Option Activity	The following table summarizes activity for the nine months ended September 30, 2016 under the 2014 Plan: Number of Shares Weighted Average Exercise Price Per Share Aggregate Intrinsic Value Options outstanding at December 31, 2015 1,620,760 $ 4.95 $ 10,339 Granted 1,121,500 $ 7.81 Exercised (18,857 ) $ 4.67 Cancelled (28,000 ) $ 6.79 Options outstanding at September 30, 2016 2,695,403 $ 6.12 $ 9,169 Options exercisable at September 30, 2016 753,207 $ 4.72 $ 3,588 Weighted-average years remaining on contractual life 8.82 Unrecognized compensation cost related to non-vested stock options $ 8,440 Aggregate intrinsic value at September 30, 2016, is based on $9.48 per share, the closing price of common stock on September 30, 2016. Aggregate intrinsic value at December 31, 2015, is based on $11.33 per share, the closing price of common stock on December 31, 2015. The following table summarizes activity for the nine months ended September 30, 2016 under the 2004 Plan: Number of Shares Weighted Average Exercise Price Per Share Aggregate Intrinsic Value Options outstanding at December 31, 2015 10,917 $ 40.58 $ — Exercised — $ — $ — Expired — $ — $ — Cancelled (291 ) $ 40.58 $ — Options outstanding at September 30, 2016 10,626 $ 40.58 $ — Options exercisable at September 30, 2016 10,626 $ 40.58 $ — Weighted-average years remaining on contractual life 1.49 Unrecognized compensation cost related to non-vested stock options $ —

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2016
Commitments And Contingencies Disclosure [Abstract]
Schedule of Aggregate Annual Commitments Pursuant to Office Lease and Lease Amendment	As of September 30, 2016, the aggregate annual commitments pursuant to the Office Lease and the Lease Amendment are as follows: Year Amount 2016 $ 52 2017 402 2018 411 2019 421 2020 430 Thereafter 959 Total $ 2,675

Fair Value of Financial Measu24

Fair Value of Financial Measurements (Tables)	9 Months Ended
	Sep. 30, 2016
Fair Value Disclosures [Abstract]
Fair Value of Assets and Liabilities Measured on Recurring Basis	The following table sets forth the Company’s financial instruments that were measured at fair value on a recurring basis by level within the fair value hierarchy: Fair Value Measurements at September 30, 2016 Total Level 1 Level 2 Level 3 Assets: Certificates of deposit $ 11,899 $ — $ 11,899 $ — United States Treasury securities 42,680 42,680 — — Short-term investments $ 54,579 $ 42,680 $ 11,899 $ — Fair Value Measurements at December 31, 2015 Total Level 1 Level 2 Level 3 Assets: Certificates of deposit $ 16,160 $ — $ 16,160 $ — Agency bonds 10,031 — 10,031 — United States Treasury securities 5,047 5,047 — — Short-term investments $ 31,238 $ 5,047 $ 26,191 $ —

Derivative Financial Instrume25

Derivative Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2016
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Effect of Derivative Instrument Not Designated as Hedging Instruments on Statement of Operations	The effect of derivative instruments not designated as hedging instruments on the statement of operations for the three and nine months ended September 30, 2015 consist of the following: Location of gain or loss Amount of gain or (loss) recognized in income on derivative financial instrument Derivative financial instruments not designated as hedging instruments recognized in income on derivative financial instrument For the Three Months Ended September 30, 2015 For the Nine Months Ended September 30, 2015 2020 Convertible Notes derivative liability Change in fair value of 2020 Convertible Notes derivative liability $ (46,649 ) $ (42,793 ) Convertible Bridge Notes Change in fair value of Convertible Bridge Notes redemption rights derivative $ — $ 480

Organization and Operations - A

Organization and Operations - Additional Information (Detail) - USD ($)	1 Months Ended			3 Months Ended		9 Months Ended
	Aug. 31, 2016	Aug. 31, 2015	Jul. 31, 2015	Sep. 30, 2016	Mar. 31, 2015	Sep. 30, 2016	Sep. 30, 2015	Aug. 30, 2016	Aug. 05, 2016	Apr. 30, 2016	Dec. 31, 2015	Mar. 24, 2015	Feb. 23, 2015	Jun. 28, 2013
Schedule Of Description Of Business [Line Items]
Net proceeds from issuance of equity		$ 73,955,000			$ 36,495,000	$ 3,997,000	$ 73,955,000
Net proceeds from issuance of debts					18,903,000
Accumulated deficit				$ (225,903,000)		(225,903,000)					$ (196,023,000)
Aggregate cash and cash equivalents and marketable securities				$ 137,583,000		137,583,000
Cowen and Company, LLC [Member]
Schedule Of Description Of Business [Line Items]
Net proceeds from issuance of equity						$ 3,997,000
Number of shares of common stock sold				0		482,689
Available for sale of common stock				$ 45,599,000		$ 45,599,000
Maximum [Member] | Cowen and Company, LLC [Member]
Schedule Of Description Of Business [Line Items]
Amount of stock transactions										$ 200,000,000
Amount of common stock transactions										$ 50,000,000
Over-Allotment Option [Member]
Schedule Of Description Of Business [Line Items]
Aggregate principal amount	$ 2,000,000				$ 1,000,000
Initial public offering common stock, shares		810,000			299,333
Initial public offering common stock, per shares					$ 6
IPO [Member]
Schedule Of Description Of Business [Line Items]
Initial public offering common stock, shares					6,966,333
IPO [Member] | Affiliated Entity [Member]
Schedule Of Description Of Business [Line Items]
Initial public offering common stock, shares					3,005,000
Secondary Public Offering [Member]
Schedule Of Description Of Business [Line Items]
Initial public offering common stock, shares		6,210,000
Initial public offering common stock, per shares		$ 12.75
2020 Convertible Notes [Member]
Schedule Of Description Of Business [Line Items]
Aggregate principal amount		$ 21,000,000	$ 21,000,000									$ 1,000,000	$ 20,000,000
Convertible senior notes, interest rate, stated percentage				5.00%		5.00%
Convertible Notes converted into shares		3,333,319	3,333,319
Additional shares of common stock		530,072	530,072
Senior Notes [Member] | 2021 Convertible Notes [Member]
Schedule Of Description Of Business [Line Items]
Aggregate principal amount	$ 52,000,000								$ 50,000,000
Convertible senior notes, interest rate, stated percentage	5.75%			5.75%		5.75%
Net proceeds from issuance of equity	$ 48,738,000
Senior Notes [Member] | 2021 Convertible Notes [Member] | Over-Allotment Option [Member]
Schedule Of Description Of Business [Line Items]
Aggregate principal amount								$ 2,000,000
Senior Notes [Member] | 2020 Convertible Notes [Member]
Schedule Of Description Of Business [Line Items]
Aggregate principal amount					$ 21,000,000
Convertible senior notes, interest rate, stated percentage					5.00%
Notes Payable [Member]
Schedule Of Description Of Business [Line Items]
Aggregate principal amount		$ 21,000,000	$ 21,000,000											$ 3,500,000
Convertible Notes converted into shares		3,333,319	3,333,319
Additional shares of common stock		530,072	530,072

Significant Accounting Polici27

Significant Accounting Policies - Additional Information (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2016USD ($)	Sep. 30, 2015USD ($)	Sep. 30, 2016USD ($)Segment	Sep. 30, 2015USD ($)	Dec. 31, 2015USD ($)
Summary of Significant Accounting Policy [Line Items]
Number of operating segments | Segment			1
Realized gains or losses on short-term investment	$ 0	$ 0	$ 0	$ 0
Unrealized gains (losses) on short-term investment	(15,000)	0	13,000	0
Other than temporary impairment evaluated	0		0		$ 0
Amortization of deferred financing costs		$ 15,000		$ 107,000
2021 Convertible Notes [Member] | Senior Notes [Member]
Summary of Significant Accounting Policy [Line Items]
Amortization of debt issuance costs	$ 82,000		$ 82,000

Significant Accounting Polici28

Significant Accounting Policies - Schedule of Short-term Investment (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Cost Basis	$ 54,578	$ 31,249
Available-for-sale securities, Unrealized Gains	8
Available-for-sale securities, Unrealized Losses	(7)	(11)
Available-for-sale securities, Fair Value	54,579	31,238
Certificates of Deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Cost Basis	11,899	16,160
Available-for-sale securities, Fair Value	11,899	16,160
Agency Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Cost Basis		10,036
Available-for-sale securities, Unrealized Losses		(5)
Available-for-sale securities, Fair Value		10,031
United States Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Cost Basis	42,679	5,053
Available-for-sale securities, Unrealized Gains	8
Available-for-sale securities, Unrealized Losses	(7)	(6)
Available-for-sale securities, Fair Value	$ 42,680	$ 5,047

Significant Accounting Polici29

Significant Accounting Policies - Schedule of Computation of Basic and Diluted Earnings (Loss) Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Numerator:
Net loss	$ (11,128)	$ (55,961)	$ (29,880)	$ (59,810)
Accretion and dividends on convertible preferred stock				(130)
Net loss applicable to common stockholders	$ (11,128)	$ (55,961)	$ (29,880)	$ (59,940)
Denominator:
Weighted average common shares outstanding - basic and diluted	26,930,730	22,573,195	26,660,126	15,580,487
Net loss per share applicable to common stockholders - basic and diluted	$ (0.41)	$ (2.48)	$ (1.12)	$ (3.85)

Significant Accounting Polici30

Significant Accounting Policies - Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share (Detail) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	9,246,228	1,596,626	9,246,228	1,596,626
Shares Issuable Upon Conversion of the 2021 Convertible Notes [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	6,483,791		6,483,791
Warrants Exerciseable for Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	56,408	56,408	56,408	56,408
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	2,706,029	1,540,218	2,706,029	1,540,218

Property and Equipment - Schedu

Property and Equipment - Schedule of Property and Equipment (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Property and equipment, Gross	$ 1,418	$ 1,074
Less: accumulated depreciation	(373)	(262)
Property and equipment, net	$ 1,045	812
Office Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Useful lives	5 years
Property and equipment, Gross	$ 397	334
Computer Hardware and Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Gross	$ 263	252
Computer Hardware and Software [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Useful lives	3 years
Computer Hardware and Software [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Useful lives	7 years
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Useful lives	5 years
Property and equipment, Gross	$ 313	43
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Useful lives	7 years
Property and equipment, Gross	$ 445	$ 445

Property and Equipment - Additi

Property and Equipment - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Property Plant And Equipment Net [Abstract]
Depreciation expense	$ 39	$ 6	$ 111	$ 7

Accrued Expenses and Other Cu33

Accrued Expenses and Other Current Liabilities - Schedule of Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Payables And Accruals [Abstract]
Compensation and benefits	$ 1,326	$ 999
Research and development	1,199	375
Government payable	471	450
Professional fees	397	347
Other	323	337
Total	$ 3,716	$ 2,508

Debt - 2021 Convertible Notes -

Debt - 2021 Convertible Notes - Additional Information (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2016USD ($)$ / shares	Sep. 30, 2015USD ($)	Sep. 30, 2016USD ($)d$ / shares	Sep. 30, 2015USD ($)	Aug. 31, 2016USD ($)	Aug. 30, 2016USD ($)	Aug. 05, 2016USD ($)	Mar. 31, 2015USD ($)
Debt Instrument [Line Items]
Interest expense	$ 525,000	$ 192,000	$ 525,000	$ 1,230,000
Over-Allotment Option [Member]
Debt Instrument [Line Items]
Debt instrument principal amount					$ 2,000,000			$ 1,000,000
2021 Convertible Notes [Member]
Debt Instrument [Line Items]
Debt issuance costs incurred			$ 3,262,000
2021 Convertible Notes [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Debt instrument principal amount					$ 52,000,000		$ 50,000,000
Debt instrument maturity date			Aug. 1, 2021
Debt instrument payment terms			Semi-annually
Convertible senior notes, interest rate, stated percentage	5.75%		5.75%		5.75%
Debt instrument payment start date			Feb. 1, 2017
Debt issuance costs incurred			$ 3,262,000
Number of shares, note gets converted into			124.7505
Principal amount	$ 1		$ 1
Debt instrument redemption description			The Company, at its option, may redeem for cash all or any portion of the 2021 Convertible Notes if the last reported sale price of a share of the Company’s common stock is equal to or greater than 200% of the conversion price for the 2021 Convertible Notes then in effect for at least 20 trading days (whether or not consecutive) during any 30 consecutive trading day period (including the last trading day of such period) ending within the five trading days immediately preceding the date on which the Company provides notice of redemption, at a redemption price equal to 100% of the principal amount of the 2021 Convertible Notes to be redeemed, plus accrued and unpaid interest to, but excluding, the redemption date.
Percentage of common stock conversion price			200.00%
Number of minimum trading days | d			20
Number of consecutive trading days			30 days
Holdings in debt outstanding			25.00%
Number of days after default			180 days
Interest expense	533,000		$ 533,000
Amortization of debt discount	$ 82,000		$ 82,000
2021 Convertible Notes [Member] | Senior Notes [Member] | First 90 Days [Member]
Debt Instrument [Line Items]
Additional interest rate	0.25%		0.25%
2021 Convertible Notes [Member] | Senior Notes [Member] | 91 to 180 Days [Member]
Debt Instrument [Line Items]
Additional interest rate	0.50%		0.50%
2021 Convertible Notes [Member] | Senior Notes [Member] | Over-Allotment Option [Member]
Debt Instrument [Line Items]
Debt instrument principal amount						$ 2,000,000
2021 Convertible Notes [Member] | Fundamental Change [Member]
Debt Instrument [Line Items]
Principal amount	$ 1		$ 1
Conversion of stock, description			If the Stock Price applicable to any conversion is greater than $40.00 per share, the Conversion Rate will not be increased. If the Stock Price applicable to any conversion is less than $6.68 per share, the Conversion Rate in connection with a Make-Whole Fundamental Change Conversion will not be increased but it will be increased by 24.95 shares in connection with a Voluntary Conversion.
Debt instrument repurchase description			Upon the occurrence of a Fundamental Change (as defined in the Indenture), each Holder may require the Company to repurchase for cash all or any portion of the 2021 Convertible Notes held by such Holder at a repurchase price equal to 100% of the principal amount thereof, plus accrued and unpaid interest thereon.
Percentage of principal amount of notes to be purchased			100.00%
2021 Convertible Notes [Member] | Fundamental Change [Member] | Minimum [Member]
Debt Instrument [Line Items]
Number of shares, note gets converted into			0
Debt Instrument, conversion rate | $ / shares	$ 40		$ 40
2021 Convertible Notes [Member] | Fundamental Change [Member] | Maximum [Member]
Debt Instrument [Line Items]
Number of shares, note gets converted into			24.95
Debt Instrument, conversion rate | $ / shares	$ 6.68		$ 6.68

Debt - Summary of Carrying Valu

Debt - Summary of Carrying Value of Convertible Notes (Detail) - 2021 Convertible Notes [Member] $ in Thousands	Sep. 30, 2016USD ($)
Debt Instrument [Line Items]
Carrying value	$ 48,820
Senior Notes [Member]
Debt Instrument [Line Items]
Gross proceeds	52,000
Initial value of issuance costs recorded as debt discount	(3,262)
Amortization of debt discount	82
Carrying value	$ 48,820

Debt - 2020 Convertible Notes -

Debt - 2020 Convertible Notes - Additional Information (Detail)	1 Months Ended		3 Months Ended		9 Months Ended
	Aug. 31, 2015USD ($)shares	Jul. 31, 2015USD ($)shares	Sep. 30, 2016USD ($)	Sep. 30, 2015USD ($)	Sep. 30, 2016USD ($)$ / shares	Sep. 30, 2015USD ($)	Mar. 24, 2015USD ($)	Feb. 23, 2015USD ($)
Debt Instrument [Line Items]
Loss on extinguishment of debt						$ 4,239,000
Interest expense			$ 525,000	$ 192,000	$ 525,000	1,230,000
2020 Convertible Notes [Member]
Debt Instrument [Line Items]
Debt instrument principal amount	$ 21,000,000	$ 21,000,000					$ 1,000,000	$ 20,000,000
Debt instrument maturity date					Feb. 15, 2020
Convertible notes, interest rate, stated percentage			5.00%		5.00%
Financing costs incurred by the company					$ 2,097,000
Number of shares, note gets converted into					158.7302
Principal amount			$ 1		$ 1
Discount rate					2.00%
Holdings in debt outstanding					25.00%
Number of days after default					180 days
Fair value of combined embedded derivative liability			$ 55,216,000		$ 55,216,000			$ 11,850,000
Derivative liabilities and discount recorded							$ 573,000
Convertible Notes converted into shares | shares	3,333,319	3,333,319
Additional shares of common stock | shares	530,072	530,072
Change in estimated fair value of combined embedded derivative liability				46,649,000		42,793,000
Loss on extinguishment of debt				3,716,000		3,716,000
Extinguishment of debt						21,000,000
Interest expense				189,000		963,000
Amortization of financing costs and discounts				15,000		74,000
Amortization of debt discount				$ 90,000		$ 440,000
2020 Convertible Notes [Member] | First 90 Days [Member]
Debt Instrument [Line Items]
Additional interest rate			0.25%		0.25%
2020 Convertible Notes [Member] | 91 to 180 Days [Member]
Debt Instrument [Line Items]
Additional interest rate			0.50%		0.50%
2020 Convertible Notes [Member] | Fundamental Change [Member]
Debt Instrument [Line Items]
Percentage of principal amount of notes to be purchased					100.00%
Repurchase price description					Upon a fundamental change, each holder would have the right to require the Company to repurchase for cash all of such holder’s notes, or any portion thereof that is equal to $1 or an integral multiple of $1.
Repurchase price | $ / shares					$ 1
2020 Convertible Notes [Member] | Fundamental Change [Member] | Minimum [Member]
Debt Instrument [Line Items]
Number of shares, note gets converted into					7.9364
2020 Convertible Notes [Member] | Fundamental Change [Member] | Maximum [Member]
Debt Instrument [Line Items]
Number of shares, note gets converted into					0

Debt - Convertible Bridge Notes

Debt - Convertible Bridge Notes - Additional Information (Detail) - USD ($)	1 Months Ended		3 Months Ended	9 Months Ended
	Feb. 28, 2015	Dec. 31, 2014	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Debt Instrument [Line Items]
Amortization of financing costs			$ 15,000		$ 107,000
Loss on extinguishment of debt					$ 4,239,000
2014 Convertible Bridge Notes [Member]
Debt Instrument [Line Items]
Debt instrument, face amount		$ 2,000,000
Debt instrument maturity date				Jun. 30, 2015
Debt instrument annual interest rate		8.00%	8.00%		8.00%
Debt converted into shares of common stock	337,932
Share offering price	$ 6
Debt instrument, interest expense to coupon rate					$ 23,000
Amortization of financing costs					128,000
Gain in change in fair value					480,000
Loss on extinguishment of debt					$ 360,000
2014 Convertible Bridge Notes [Member] | Minimum [Member]
Debt Instrument [Line Items]
Gross proceeds		$ 40,000,000

Debt - Notes Payable - Addition

Debt - Notes Payable - Additional Information (Detail)	Jun. 28, 2013USD ($)AgreementEntity	Feb. 28, 2015USD ($)	Sep. 30, 2016USD ($)Installment$ / sharesshares	Sep. 30, 2015USD ($)	Aug. 31, 2015USD ($)	Jul. 31, 2015USD ($)	Jan. 31, 2015USD ($)
Debt Instrument [Line Items]
Loss on extinguishment of debt				$ 4,239,000
Change in fair value of warrant liabilities				(267,000)
Notes Payable [Member]
Debt Instrument [Line Items]
Number of loan and security agreements | Agreement	2
Number of financial entities | Entity	2
Debt instrument principal balance	$ 3,500,000				$ 21,000,000	$ 21,000,000
Proceeds from loans issued	$ 6,915,000
Interest rate			11.00%
Loan maturity date			Oct. 1, 2016
Interest only payments for initial			12 months
Number of installments | Installment			27
Termination payment percentage		3.00%	3.00%
Loan termination payment		$ 210,000	$ 210,000
Warrant or right securities called by warrants, amount			$ 350,000
Warrant expiration date			The warrants expire on the earlier of (i) ten years after the date of grant, or (ii) immediately prior to an acquisition transaction, as defined in the warrants.
Repaying principal amount		5,347,000
Prepayment fee		160,000
Interest accrued		$ 23,000
Debt instrument, principal payments							$ 243,000
Interest expense related to loan agreements				115,000
Accretion of debt discounts and loan termination payment				26,000
Loss on extinguishment of debt				322,000
Warrants issued to lenders exercisable to common shares | shares			56,408
Warrants issued to lenders exercisable to common shares, price per share | $ / shares			$ 6.204
Change in fair value of warrant liabilities				$ 267,000
Reclassification of fair value of warrant liability to equity upon initial public offering			$ 215,000
Notes Payable [Member] | Warrants Exercisable for Common Stock [Member]
Debt Instrument [Line Items]
IPO price of the Company's common stock | $ / shares			$ 6
Fair value assumptions, expected term			8 years 4 months 24 days
Fair value assumptions, risk free interest rate			1.70%
Fair value assumptions, expected volatility rate			60.00%
Fair value of the warrant liability			$ 215,000
Notes Payable [Member] | Series AA Preferred Stock [Member]
Debt Instrument [Line Items]
Preferred stock issued to lenders | shares			228,906
Preferred stock issued to lenders, price per share | $ / shares			$ 1.529

Equity - Additional Information

Equity - Additional Information (Detail) - USD ($)	May 31, 2016	Aug. 31, 2015	Sep. 30, 2016	Sep. 30, 2015	Mar. 31, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015	Dec. 31, 2014	Jan. 01, 2016
Stockholders Equity [Line Items]
Common stock, shares authorized			120,000,000			120,000,000		120,000,000
Common stock, par value			$ 0.01			$ 0.01		$ 0.01
Preferred stock, shares authorized			5,000,000			5,000,000		5,000,000
Preferred stock, par value			$ 0.001			$ 0.001		$ 0.001
Stock-based compensation expense							$ 950,000
Common stock voting rights description						one vote per share
Net proceeds from issuance of equity		$ 73,955,000			$ 36,495,000	$ 3,997,000	73,955,000
Common stock, shares outstanding			26,930,730			26,930,730		26,423,394
2014 Stock Option and Incentive Plan [Member]
Stockholders Equity [Line Items]
Stock-based compensation expense			$ 783,000	$ 374,000		$ 1,935,000	982,000
Number of shares reserved for future issuance			508,034			508,034				1,056,936
Percentage of outstanding common stock increased to shares available for grant								4.00%
Stock options granted						1,121,500
Expiration period of stock options						10 years
Stock options, dividend yield						0.00%
Weighted-average fair value of stock options granted			$ 5.27			$ 5.25
Closing price of common stock			$ 9.48			$ 9.48		$ 11.33
Stock options, intrinsic value			$ 9,169,000			$ 9,169,000		$ 10,339,000
2014 Stock Option and Incentive Plan [Member] | Share-based Compensation Award, Tranche One [Member]
Stockholders Equity [Line Items]
Stock-based compensation expense						$ 5,790,000
2014 Stock Option and Incentive Plan [Member] | Minimum [Member]
Stockholders Equity [Line Items]
Stock options, expected term						5 years 3 months 22 days
Stock options, expected stock price volatility						76.90%
Stock options, risk free rate						1.20%
2014 Stock Option and Incentive Plan [Member] | Maximum [Member]
Stockholders Equity [Line Items]
Stock options, expected term						6 years 29 days
Stock options, expected stock price volatility						79.20%
Stock options, risk free rate						1.90%
2014 Stock Option and Incentive Plan [Member] | General and Administrative Expense [Member]
Stockholders Equity [Line Items]
Stock-based compensation expense			438,000	228,000		$ 1,077,000	544,000
2014 Stock Option and Incentive Plan [Member] | Research and Development Expense [Member]
Stockholders Equity [Line Items]
Stock-based compensation expense			$ 345,000	$ 146,000		$ 858,000	$ 438,000
2004 Stock Option Plan [Member]
Stockholders Equity [Line Items]
Closing price of common stock			$ 9.48			$ 9.48
Stock options, intrinsic value			$ 0			$ 0
Employee Stock Purchase Plan [Member]
Stockholders Equity [Line Items]
Stock-based compensation expense			$ 23,000			43,000
Gross proceeds from issuance of common stock	$ 45,000					$ 45,000
Number of shares reserved for future issuance			600,000			600,000				117,100
Percentage of outstanding common stock increased to shares available for grant						1.00%
Number of shares available for issuance			258,443			258,443
Stock purchased under ESPP	5,790
Cowen and Company, LLC [Member]
Stockholders Equity [Line Items]
Number of common stock sold			0			482,689
Gross proceeds from issuance of common stock						$ 4,401,000
Net proceeds from issuance of equity						3,997,000
Available for sale of common stock			$ 45,599,000			$ 45,599,000
Series X Redeemable Convertible Preferred Stock [Member]
Stockholders Equity [Line Items]
Preferred stock shares vested									558,862

Equity - Summary of Stock Optio

Equity - Summary of Stock Option Activity (Detail)	9 Months Ended
	Sep. 30, 2016USD ($)$ / sharesshares
2014 Stock Option and Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares Outstanding, Beginning Balance | shares	1,620,760
Stock options granted | shares	1,121,500
Number of Shares , Exercised | shares	(18,857)
Number of Shares , Cancelled | shares	(28,000)
Number of Shares Outstanding, Ending Balance | shares	2,695,403
Number of Shares, Options Exercisable | shares	753,207
Weighted-average years remaining on contractual life	8 years 9 months 26 days
Unrecognized compensation cost related to non-vested stock options | $	$ 8,440,000
Weighted Average Exercise Price Per Share, Beginning Balance | $ / shares	$ 4.95
Weighted Average Exercise Price Per Share, Granted | $ / shares	7.81
Weighted Average Exercise Price Per Share, Exercised | $ / shares	4.67
Weighted Average Exercise Price Per Share, Cancelled | $ / shares	6.79
Weighted Average Exercise Price Per Share, Ending Balance | $ / shares	6.12
Weighted Average Exercise Price Per Share, Options Exercisable | $ / shares	$ 4.72
Aggregate Intrinsic Value, Outstanding Beginning Balance | $	$ 10,339,000
Aggregate Intrinsic Value, Outstanding Ending Balance | $	9,169,000
Aggregate Intrinsic Value, Options Exercisable | $	$ 3,588,000
2004 Stock Option Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares Outstanding, Beginning Balance | shares	10,917
Number of Shares , Cancelled | shares	(291)
Number of Shares Outstanding, Ending Balance | shares	10,626
Number of Shares, Options Exercisable | shares	10,626
Weighted-average years remaining on contractual life	1 year 5 months 27 days
Weighted Average Exercise Price Per Share, Beginning Balance | $ / shares	$ 40.58
Weighted Average Exercise Price Per Share, Cancelled | $ / shares	40.58
Weighted Average Exercise Price Per Share, Ending Balance | $ / shares	40.58
Weighted Average Exercise Price Per Share, Options Exercisable | $ / shares	$ 40.58
Aggregate Intrinsic Value, Outstanding Ending Balance | $	$ 0

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	May 31, 2015	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Commitments And Contingencies Disclosure [Abstract]
Commencement date of lease	2015-09
Acquisition of leasehold improvements	$ 445				$ 445
Operating leases, rent expenses		$ 66	$ 43	$ 190	$ 78

Commitments and Contingencies42

Commitments and Contingencies - Schedule of Aggregate Annual Commitments Pursuant to Office Lease and Lease Amendment (Detail) $ in Thousands	Sep. 30, 2016USD ($)
Commitments And Contingencies Disclosure [Abstract]
2,016	$ 52
2,017	402
2,018	411
2,019	421
2,020	430
Thereafter	959
Total	$ 2,675

Fair Value of Financial Measu43

Fair Value of Financial Measurements - Fair Value of Assets and Liabilities Measured on Recurring Basis (Detail) - Fair Value Measurements, Recurring [Member] - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Certificates of Deposit [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Short-term investments fair value disclosure	$ 11,899	$ 16,160
Agency Bonds [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Short-term investments fair value disclosure		10,031
United States Treasury Securities [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Short-term investments fair value disclosure	42,680	5,047
Short-term Investments [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Short-term investments fair value disclosure	54,579	31,238
Level 1 [Member] | United States Treasury Securities [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Short-term investments fair value disclosure	42,680	5,047
Level 1 [Member] | Short-term Investments [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Short-term investments fair value disclosure	42,680	5,047
Level 2 [Member] | Certificates of Deposit [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Short-term investments fair value disclosure	11,899	16,160
Level 2 [Member] | Agency Bonds [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Short-term investments fair value disclosure		10,031
Level 2 [Member] | Short-term Investments [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Short-term investments fair value disclosure	$ 11,899	$ 26,191

Fair Value of Financial Measu44

Fair Value of Financial Measurements - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2015	Dec. 31, 2014
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Derivative, Gain (Loss) on Derivative, Net	$ (46,649)	$ (42,793)
Convertible Notes Redemption Rights Derivative [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair value of embedded derivative			$ 480
Notes converted in to shares			337,932
Derivative, Gain (Loss) on Derivative, Net		$ 480

Derivative Financial Instrume45

Derivative Financial Instruments - Effect of Derivative Instrument Not Designated as Hedging Instruments on Statement of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2015
Change in Fair Value of 2020 Convertible Notes Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain or (loss) recognized in income on derivative financial instrument	$ (46,649)	$ (42,793)
Change in Fair Value of Convertible Bridge Notes Redemption Rights Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain or (loss) recognized in income on derivative financial instrument		$ 480

Subsequent Event - Additional I

Subsequent Event - Additional Information (Detail) - Transition Agreement [Member] - USD ($) $ in Thousands	1 Months Ended	9 Months Ended
	Oct. 31, 2016	Sep. 30, 2016
Subsequent Event [Line Items]
Description of Transition Agreement		Pursuant to the terms of the Transition Agreement, Dr. McVicar will remain an employee of the Company as a Senior Advisor for a six-month period ending April 4, 2017 and for twelve months thereafter will receive his salary and medical benefits at the same rate in effect as of the date of the Transition Agreement.
Subsequent Event [Member]
Subsequent Event [Line Items]
Expected payment related to transition agreement	$ 750