Larimar Therapeutics (LRMR) 10-Q 13 Nov 15 2015 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2015	Oct. 30, 2015
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	Q3
Trading Symbol	ZFGN
Entity Registrant Name	Zafgen, Inc.
Entity Central Index Key	1,374,690
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		27,234,542

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 38,763	$ 58,103
Marketable securities	165,191	57,359
Tax incentive receivable	334	391
Prepaid expenses and other current assets	1,802	1,345
Total current assets	206,090	117,198
Property and equipment, net	303	79
Tax incentive receivable	975
Other assets	79	242
Total assets	207,447	117,519
Current liabilities:
Accounts payable	4,151	2,348
Accrued expenses	6,556	3,172
Notes payable, current	2,877	1,381
Total current liabilities	13,584	6,901
Notes payable, net of discount, long-term	4,162	6,177
Total liabilities	$ 17,746	$ 13,078
Commitments and contingencies (Note 7)
Stockholders' equity:
Preferred stock; $0.001 par value; 5,000,000 shares authorized at September 30, 2015 and December 31, 2014; no shares issued and outstanding at September 30, 2015 and December 31, 2014
Common stock, $0.001 par value; 115,000,000 shares authorized at September 30, 2015 and December 31, 2014; 27,233,574 and 22,879,160 shares issued and outstanding at September 30, 2015 and December 31, 2014, respectively	$ 27	$ 23
Additional paid-in capital	346,203	209,838
Accumulated deficit	(156,497)	(105,385)
Accumulated other comprehensive loss	(32)	(35)
Total stockholders' equity	189,701	104,441
Total liabilities and stockholders' equity	$ 207,447	$ 117,519

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Sep. 30, 2015	Dec. 31, 2014
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	$ 0.001	$ 0.001
Common stock, shares authorized	115,000,000	115,000,000
Common stock, shares issued	27,233,574	22,879,160
Common stock, shares outstanding	27,233,574	22,879,160

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Income Statement [Abstract]
Revenue	$ 0	$ 0	$ 0	$ 0
Operating expenses:
Research and development	14,171	12,076	36,912	20,046
General and administrative	5,546	2,285	13,655	4,822
Total operating expenses	19,717	14,361	50,567	24,868
Loss from operations	(19,717)	(14,361)	(50,567)	(24,868)
Other income (expense):
Interest income	143	1	245	2
Interest expense	(200)	(213)	(626)	(658)
Foreign currency transaction gains (losses), net	(110)	(116)	(164)	(23)
Total other income (expense), net	(167)	(328)	(545)	(679)
Net loss	(19,884)	(14,689)	(51,112)	(25,547)
Accretion of redeemable convertible preferred stock to redemption value				(92)
Net loss attributable to common stockholders	$ (19,884)	$ (14,689)	$ (51,112)	$ (25,639)
Net loss per share attributable to common stockholders, basic and diluted	$ (0.73)	$ (0.65)	$ (1.92)	$ (2.97)
Weighted average common shares outstanding, basic and diluted	27,138,667	22,707,012	26,593,646	8,618,793
Comprehensive loss:
Net loss	$ (19,884)	$ (14,689)	$ (51,112)	$ (25,547)
Other comprehensive gain (loss):
Unrealized gain (loss) on marketable securities	29		4
Total other comprehensive gain (loss)	29		4
Total comprehensive loss	$ (19,855)	$ (14,689)	$ (51,108)	$ (25,547)

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Cash flows from operating activities:
Net loss	$ (51,112)	$ (25,547)
Adjustments to reconcile net loss to net cash used in operating activities
Stock-based compensation expense	5,837	910
Non-cash interest expense	48	36
Depreciation expense	27	10
Unrealized foreign currency transaction losses (gains)	145	31
Premium on purchases of marketable securities, net	(1,142)
Amortization of premium on marketable securities	756
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(546)	(997)
Tax incentive receivable	(1,063)	368
Accounts payable	1,841	(416)
Accrued expenses	3,599	9,078
Net cash used in operating activities	(41,610)	(16,527)
Cash flows from investing activities:
Proceeds from maturities of marketable securities	139,417
Purchases of marketable securities	(246,771)
Purchases of property and equipment	(224)	(42)
Deposits for leased property		(57)
Net cash used in investing activities	(107,578)	(99)
Cash flows from financing activities:
Proceeds from issuance of redeemable convertible preferred stock, net of issuance costs		442
Proceeds from issuance of notes payable, net of issuance costs		7,386
Payments of debt offering costs		(49)
Repayments of notes payable	(684)
Proceeds from public offerings, net of commissions and underwriting discounts	129,571	102,672
Payments of public offering costs		(2,312)
Proceeds from exercise of common stock options and employee stock purchase plan	961
Net cash provided by financing activities	129,848	108,139
Net (decrease) increase in cash and cash equivalents	(19,340)	91,513
Cash and cash equivalents at beginning of period	58,103	35,517
Cash and cash equivalents at end of period	38,763	127,030
Supplemental disclosure of non-cash investing and financing activities:
Accretion of redeemable convertible preferred stock to redemption values		92
Property and equipment included in accounts payable	27
Conversion of redeemable preferred stock to common stock		104,331
Supplemental disclosure of cash flow information:
Cash paid for interest	$ 447	$ 480

Nature of the Business and Basi

Nature of the Business and Basis of Presentation	9 Months Ended
	Sep. 30, 2015
Accounting Policies [Abstract]
Nature of the Business and Basis of Presentation	1. Nature of the Business and Basis of Presentation Zafgen, Inc. (the “Company”) was incorporated on November 22, 2005 under the laws of the State of Delaware. The Company is a biopharmaceutical company dedicated to significantly improving the health and well-being of patients affected by obesity and complex metabolic disorders. Zafgen is focused on developing novel therapeutics that treat the underlying biological mechanisms through the methionine aminopeptidase 2 (“MetAP2”) pathway. Beloranib, the Company’s lead product candidate, is a novel, first-in-class, twice-weekly subcutaneous injection being developed for the treatment of multiple indications, including severe obesity in two rare diseases, Prader-Willi syndrome and obesity caused by hypothalamic injury, including craniopharyngioma-associated obesity; and severe obesity in the general population. Zafgen is also developing ZGN-839, a liver-targeted MetAP2 inhibitor, for the treatment of nonalcoholic steatohepatitis (“NASH”) and abdominal obesity, as well as other second-generation MetAP2 inhibitors. Since its inception, the Company has devoted substantially all of its efforts to research and development, recruiting management, acquiring operating assets and raising capital. The Company is subject to risks common to companies in the biotechnology industry including, but not limited to, new technological innovations, protection of proprietary technology, dependence on key personnel, compliance with government regulations and the need to obtain additional financing. Product candidates currently under development will require significant additional research and development efforts, including extensive pre-clinical and clinical testing and regulatory approval, prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel infrastructure, and extensive compliance-reporting capabilities. The Company’s product candidates are all in the development stage. There can be no assurance that the Company’s research and development will be successfully completed, that adequate protection for the Company’s intellectual property will be obtained, that any products developed will obtain necessary government regulatory approval or that any approved products will be commercially viable. Even if the Company’s product development efforts are successful, it is uncertain when, if ever, the Company will generate significant revenue from product sales. The Company operates in an environment of rapid change in technology and substantial competition from pharmaceutical and biotechnology companies. In addition, the Company is dependent upon the services of its employees and consultants. The consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries Zafgen Securities Corporation, Zafgen Australia Pty Limited, and Zafgen Animal Health, LLC. All significant intercompany balances and transactions have been eliminated. On June 24, 2014, the Company completed an initial public offering (“IPO”) of its common stock, which resulted in the sale of 6,900,000 shares at a price of $16.00 per share. The Company received net proceeds from the IPO of approximately $102,672 based upon the price of $16.00 per share after deducting underwriting discounts and commissions paid by the Company. The Company also incurred offering costs of $2,508 related to the IPO. On January 28, 2015, the Company completed a follow-on offering of its common stock, which resulted in the sale of 3,942,200 shares at a price of $35.00 per share. The Company received net proceeds from the follow-on offering of $130,044 based upon the price of $35.00 per share after deducting underwriting discounts and commissions. The Company also incurred offering costs of $473 related to the follow-on offering. Unaudited Interim Financial Information The condensed consolidated balance sheet at December 31, 2014 was derived from the Company’s audited financial statements, but does not include all disclosures required by generally accepted accounting principles, or GAAP. The accompanying unaudited condensed consolidated financial statements as of September 30, 2015 and for the three and nine months ended September 30, 2015 and 2014, have been prepared by the Company, pursuant to the rules and regulations of the Securities and Exchange Commission, or SEC for interim financial statements. Certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. However, the Company believes that the disclosures are adequate to make the information presented not misleading. These condensed consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements and the notes thereto for the year ended December 31, 2014, included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2014, on file with the SEC. In the opinion of management, all adjustments, consisting only of normal recurring adjustments necessary for a fair presentation of the Company’s condensed consolidated financial position as of September 30, 2015 and condensed consolidated results of operations and cash flows for the three and nine months ended September 30, 2015 and 2014 have been made. The results of operations for the three and nine months ended September 30, 2015 are not necessarily indicative of the results of operations that may be expected for the year ending December 31, 2015.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2015
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates, assumptions and judgments that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the consolidated financial statements, and the reported amounts of expenses during the reporting periods. Significant estimates, assumptions and judgments reflected in these condensed consolidated financial statements include, but are not limited to, the accrual of research and development expenses, the valuation of common stock prior to the IPO and the valuation of stock-based awards. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. Actual results could differ from the Company’s estimates. Fair Value Measurements The following tables present information about the Company’s financial assets that have been measured at fair value at September 30, 2015 and December 31, 2014, and indicate the fair value of the hierarchy of the valuation inputs utilized to determine such fair value. In general, fair values determined by Level 1 inputs utilize quoted prices (unadjusted) in active markets for identical assets or liabilities. Fair value determined by Level 2 inputs utilize observable inputs other than Level 1 prices, such as quoted prices, for similar assets or liabilities, quoted market prices in markets that are not active or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the related assets or liabilities. Fair values determined by Level 3 inputs are unobservable data points for the asset or liability, and includes situations where there is little, if any, market activity for the asset or liability. The following tables summarize the Company’s cash equivalents and marketable securities as of September 30, 2015 and December 31, 2014: September 30, 2015 Quoted Significant Prices in Other Significant Active Observable Unobservable Markets Inputs Inputs Total (Level 1) (Level 2) (Level 3) Cash equivalents: Money market funds $ 21,812 $ 21,812 $ — $ — Commercial paper 6,499 — 6,499 — Corporate bonds 1,254 — 1,254 — Total cash equivalents 29,565 21,812 7,753 — Marketable securities: Corporate bonds 121,220 — 121,220 — Commercial paper 32,968 — 32,968 U.S. government securities 11,003 — 11,003 — Total marketable securities 165,191 — 165,191 — Total cash equivalents and marketable securities $ 194,756 $ 21,812 $ 172,944 $ — December 31, 2014 Quoted Significant Prices in Other Significant Active Observable Unobservable Markets Inputs Inputs Total (Level 1) (Level 2) (Level 3) Cash equivalents: Money market funds $ 14,742 $ 14,742 $ — $ — U.S. government securities 27,767 — 27,767 — Total cash equivalents 42,509 14,742 27,767 — Marketable securities: U.S. government securities 34,191 — 34,191 — Corporate bonds 22,168 — 22,168 — Commercial paper 1,000 — 1,000 — Total marketable securities 57,359 — 57,359 — Total cash equivalents and marketable securities $ 99,868 $ 14,742 $ 85,126 $ — During the three and nine months ended September 30, 2015, there were no transfers between Level 1 and Level 2 financial assets. The carrying amounts reflected in the condensed consolidated balance sheets for tax incentive receivable, accounts payable, and accrued expenses approximate fair value due to their short-term maturities. The carrying value of the Company’s outstanding notes payable approximates fair value (a Level 2 fair value measurement), reflecting discount rates currently available to the Company. Marketable Securities The following tables summarize the Company’s marketable securities as of September 30, 2015 and December 31, 2014: September 30, 2015 Gross Gross Amortized Unrealized Unrealized Cost Gains Losses Fair Value Assets: Corporate bonds (due within 1 year) $ 107,034 $ — $ (36 ) $ 106,998 Corporate bonds (due after 1 year through 2 years) 14,216 6 — 14,222 Commercial paper (due within 1 year) 32,970 — (2 ) 32,968 U.S. government securities (due within 1 year) 11,003 — — 11,003 $ 165,223 $ 6 $ (38 ) $ 165,191 December 31, 2014 Gross Gross Amortized Unrealized Unrealized Cost Gains Losses Fair Value Assets: U.S. government securities (due within 1 year) $ 34,200 $ — $ (9 ) $ 34,191 Corporate bonds (due within 1 year) 18,716 — (18 ) 18,698 Corporate bonds (due after 1 year through 2 years) 3,478 — (8 ) 3,470 Commercial paper (due within 1 year) 1,000 — — 1,000 $ 57,394 $ — $ (35 ) $ 57,359 Income (Loss) Per Share Upon the closing of the Company’s IPO in June 2014, all of the Company’s outstanding redeemable convertible preferred shares were converted into shares of common stock. Prior to this conversion, the Company followed the two-class method when computing net income (loss) per share as the Company had issued shares that meet the definition of participating securities. The two-class method determines net income (loss) per share for each class of common and participating securities according to dividends declared or accumulated and participation rights in undistributed earnings. The two-class method requires income available to common stockholders for the period to be allocated between common and participating securities based upon their respective rights to receive dividends as if all income for the period had been distributed. The Company’s redeemable convertible preferred shares contractually entitled the holders of such shares to participate in dividends, but did not contractually require the holders of such shares to participate in losses of the Company. Accordingly, the two-class method did not apply for periods in which the Company reported a net loss or a net loss attributable to common stockholders resulting from dividends or accretion related to its redeemable convertible preferred shares. Basic net income (loss) per share attributable to common stockholders is computed by dividing the net income (loss) attributable to common stockholders by the weighted average number of common shares outstanding for the period. Diluted net income (loss) per share attributable to common stockholders is computed by dividing the diluted net income (loss) attributable to common stockholders by the weighted average number of common shares outstanding, including potential dilutive common shares assuming the dilutive effect of outstanding stock options and unvested restricted common shares, as determined using the treasury stock method. For periods in which the Company has reported net losses, diluted net loss per common share attributable to common stockholders is the same as basic net loss per common share attributable to common stockholders, since dilutive common shares are not assumed to have been issued if their effect is antidilutive. The Company reported a net loss attributable to common stockholders for the three and nine months ended September 30, 2015 and 2014. Basic and diluted net loss per share attributable to common stockholders was calculated as follows: For the three months ended For the nine months ended 2015 2014 2015 2014 Basic and diluted net loss per share attributable to common stockholders: Numerator: Net loss $ (19,884 ) $ (14,689 ) $ (51,112 ) $ (25,547 ) Accretion of redeemable convertible preferred stock to redemption value — — — (92 ) Net loss attributable to common stockholders $ (19,884 ) $ (14,689 ) $ (51,112 ) $ (25,639 ) Denominator: Weighted average of common shares outstanding, basic and diluted 27,138,667 22,707,012 26,593,646 8,618,793 Net loss per share attributable to common stockholders, basic and diluted $ (0.73 ) $ (0.65 ) $ (1.92 ) $ (2.97 ) The following common stock equivalents outstanding (prior to consideration of the treasury stock method) as of September 30, 2015 and 2014, were excluded from the computation of diluted net loss per share for the three and nine months ended September 30, 2015 and 2014, because they had an anti-dilutive impact: As of September 30, 2015 2014 Options to purchase common stock` 2,574,132 1,839,895 Unvested restricted stock 1,935 — 2,576,067 1,839,895 Recently Issued and Adopted Accounting Pronouncements In August 2014, the Financial Accounting Standards Board issued Accounting Standards Update No. 2014-15, Presentation of Financial Statements — Going Concern (Subtopic 205-40). The new guidance addresses 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. Management’s evaluation should be based on relevant conditions and events that are known and reasonably knowable at the date that the financial statements are issued. The standard will be effective for the first interim period within annual reporting periods beginning after December 15, 2016. Early adoption is permitted. The Company is evaluating the effect that this guidance will have on its condensed consolidated financial statements.

Accrued Expenses

Accrued Expenses	9 Months Ended
	Sep. 30, 2015
Payables and Accruals [Abstract]
Accrued Expenses	3. Accrued Expenses Accrued expenses consisted of the following: September 30, December 31, 2015 2014 Accrued research and development expenses $ 3,808 $ 1,180 Accrued payroll and related expenses 1,924 1,239 Accrued professional fees 705 585 Accrued other 119 168 $ 6,556 $ 3,172

Notes Payable

Notes Payable	9 Months Ended
	Sep. 30, 2015
Debt Disclosure [Abstract]
Notes Payable	4. Notes Payable The Company has outstanding amounts due under a loan and security agreement with Oxford Finance LLC and Midcap Financial (the “Credit Facility”) entered into in March 2014. All promissory notes issued under the Credit Facility are collateralized by substantially all of the Company’s personal property, other than intellectual property. There are no financial covenants associated with the Credit Facility; however, there are negative covenants restricting the Company’s activities, including limitations on dispositions, mergers or acquisitions; encumbering or granting a security interest in the Company’s intellectual property; incurring indebtedness or liens; paying dividends; making certain investments; and certain other business transactions. As of September 30, 2015 and December 31, 2014, notes payable consist of the following: September 30, December 31, 2015 2014 Notes payable $ 6,816 $ 7,500 Less: current portion (2,877 ) (1,381 ) Notes payable, net of current portion 3,939 6,119 Debt discount, net of accretion (46 ) (79 ) Accretion related to final payment 269 137 Notes payable, net of discount, long term $ 4,162 $ 6,177 As of September 30, 2015, estimated future principal payments due are as follows: Years Ending December 31, 2015 $ 697 2016 2,936 2017 3,183 $ 6,816 During the three months ended September 30, 2015 and 2014, the Company recognized $200 and $213, respectively, of interest expense related to the Credit Facility. During the nine months ended September 30, 2015 and 2014, the Company recognized $626 and $658, respectively, of interest expense related to the Credit Facility. The effective annual interest rate of the outstanding debt under the Credit Facility is approximately 14%.

Stockholders' Equity

Stockholders' Equity	9 Months Ended
	Sep. 30, 2015
Equity [Abstract]
Stockholders' Equity	5. Stockholders’ Equity In January 2015, the Company completed a follow-on offering resulting in the sale of 3,942,200 common shares at $35.00 per share, including 514,200 shares related to the exercise of the over-allotment option by the underwriters. The Company received net proceeds from the follow-on offering of $130,044 based upon the price of $35.00 per share after deducting underwriting discounts and commissions. The Company also incurred offering costs of $473 related to the follow-on offering.

Stock-Based Awards

Stock-Based Awards	9 Months Ended
	Sep. 30, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Awards	6. Stock-Based Awards The Company grants equity awards under its 2014 Stock Option and Incentive Plan and is authorized to issue common stock under its 2014 Employee Stock Purchase Plan. The Company also has outstanding stock-based awards under its Amended and Restated 2006 Stock Option Plan but is no longer granting awards under this plan. As of September 30, 2015, 1,615,599 shares are available for grant under the 2014 Stock Option and Incentive Plan, including 915,166 shares automatically added to the 2014 Stock Option and Incentive Plan on January 1, 2015 as a result of a provision in the plan, and 257,460 shares are available for issuance to participating employees under the 2014 Employee Stock Purchase Plan. The Company recorded stock-based compensation expense related to stock options and restricted common stock in the following expense categories of its condensed consolidated statements of operations: Three Months Ended Nine Months Ended September 30, September 30, 2015 2014 2015 2014 Research and development $ 895 $ 91 $ 2,037 $ 259 General and administrative 1,946 375 3,800 651 $ 2,841 $ 466 $ 5,837 $ 910 For the nine months ended September 30, 2015, the Company granted 968,298 stock options; 964,298 stock options to employees and directors and 4,000 stock options to a consultant. As of September 30, 2015, the Company had an aggregate of $31,069 of unrecognized stock-based compensation cost, which is expected to be recognized over a weighted average period of 3.1 years. As of September 30, 2015, there were outstanding unvested service-based stock options held by nonemployees for the purchase of 11,458 shares of common stock.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	7. Commitments and Contingencies Leases The Company has a lease for office space in Boston, Massachusetts, effective as of July 28, 2014, with a term expiring July 31, 2017 and an option to extend the lease for three additional years. In March 2015, the Company entered into an operating lease for additional office space in Boston, Massachusetts, effective as of April 15, 2015, with a term expiring on July 31, 2017, and two options to extend the lease for three additional years each. Future minimum lease payments for its operating lease as of September 30, 2015 are as follows: Years Ending December 31, 2015 $ 107 2016 335 2017 199 $ 641 During the three months ended September 30, 2015 and 2014, the Company recognized $83 and $52, respectively, of rental expense related to office space. During the nine months ended September 30, 2015 and 2014, the Company recognized $220 and $104, respectively, of rental expense related to office space. Intellectual Property Licenses The Company has acquired exclusive rights to develop patented compounds and related know-how for beloranib under licensing agreements with two third parties in the course of its research and development activities. The licensing rights obligate the Company to make payments to the licensors for license fees, milestones, license maintenance fees and royalties. The Company is also responsible for patent prosecution costs. As of September 30, 2015, the Company is obligated to make milestone payments of up to $12,250 upon reaching certain pre-commercialization milestones, such government approvals (including the U.S. Food and Drug Administration, or FDA, approval of a New Drug Application, or NDA), and up to $12,500 upon reaching certain product commercialization milestones. Under one of the license agreements, the Company is also obligated to pay up to $1,250 with respect to each subsequent licensed product, if any, that is a new chemical entity. In addition, the Company will owe single-digit royalties on sales of commercial products developed using these licensed technologies, if any. The Company is also obligated to pay to the licensors a percentage of fees received if and when the Company sublicenses the technology. As of September 30, 2015, the Company has not yet developed a commercial product using the licensed technologies and it has not entered into any sublicense agreements for the technologies. Indemnification Agreements In the ordinary course of business, the Company may provide indemnification of varying scope and terms to vendors, lessors, business partners, and other parties with respect to certain matters including, but not limited to, losses arising out of breach of such agreements or from intellectual property infringement claims made by third parties. In addition, the Company has entered into indemnification agreements with members of its board of directors that will require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors or officers. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is, in many cases, unlimited. To date, the Company has not incurred any material costs as a result of such indemnifications. The Company does not believe that the outcome of any claims under indemnification arrangements will have a material effect on its financial position, results of operations or cash flows, and it has not accrued any liabilities related to such obligations in its condensed consolidated financial statements as of September 30, 2015.

Retirement Plan

Retirement Plan	9 Months Ended
	Sep. 30, 2015
Compensation and Retirement Disclosure [Abstract]
Retirement Plan	8. Retirement Plan The Company has a Savings Incentive Match Plan for employees. Under the terms of the plan, the Company contributes 2% of an employee’s annual base salary, up to a maximum of the annual Internal Revenue Service compensation limits, for all full-time employees. During the three months ended September 30, 2015 and 2014, the Company recognized $32 and $17, respectively, of expense related to its contributions to this plan. During the nine months ended September 30, 2015 and 2014, the Company recognized $111 and $43, respectively, of expense related to its contributions to this plan.

Australia Research and Developm

Australia Research and Development Tax Incentive	9 Months Ended
	Sep. 30, 2015
Research and Development [Abstract]
Australia Research and Development Tax Incentive	9. Australia Research and Development Tax Incentive The Company’s wholly owned subsidiary, Zafgen Australia Pty Limited, which conducts core research and development activities on behalf of the Company is eligible to receive a 45% refundable tax incentive for qualified research and development activities. For the three months ended September 30, 2015 and 2014, $376 and $91, respectively, was recorded as a reduction to research and development expenses in the condensed consolidated statements of operations. For the nine months ended September 30, 2015 and 2014, $1,063 and $164, respectively, was recorded as a reduction to research and development expenses in the condensed consolidated statements of operations. These amounts represented 45% of the Company’s qualified research and development spending in Australia. The refund is denominated in Australian dollars and, therefore, the receivable is re-measured into U.S. dollars as of each reporting date. For the three months ended September 30, 2015 and 2014, the Company recorded in its condensed consolidated statements of operations unrealized foreign currency exchange gains (losses) of $(107) and $(95), respectively, related to this tax incentive receivable. For the nine months ended September 30, 2015 and 2014, the Company recorded in its condensed consolidated statements of operations unrealized foreign currency exchange gains (losses) of $(145) and $(31), respectively, related to this tax incentive receivable. As of September 30, 2015 and December 31, 2014, the Company’s tax incentive receivable from the Australian government was $1,309 and $391, respectively.

Subsequent Event

Subsequent Event	9 Months Ended
	Sep. 30, 2015
Subsequent Events [Abstract]
Subsequent Event	10. Subsequent Event On October 21, 2015, a purported stockholder of the Company filed a putative class action lawsuit in the U.S. District Court for the District of Massachusetts, against the Company and Thomas E. Hughes, entitled Aviad Bessler v. Zafgen, Inc. and Thomas E. Hughes,

Nature of the Business and Ba16

Nature of the Business and Basis of Presentation (Policies)	9 Months Ended
	Sep. 30, 2015
Accounting Policies [Abstract]
Unaudited Interim Financial Information	Unaudited Interim Financial Information The condensed consolidated balance sheet at December 31, 2014 was derived from the Company’s audited financial statements, but does not include all disclosures required by generally accepted accounting principles, or GAAP. The accompanying unaudited condensed consolidated financial statements as of September 30, 2015 and for the three and nine months ended September 30, 2015 and 2014, have been prepared by the Company, pursuant to the rules and regulations of the Securities and Exchange Commission, or SEC for interim financial statements. Certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. However, the Company believes that the disclosures are adequate to make the information presented not misleading. These condensed consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements and the notes thereto for the year ended December 31, 2014, included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2014, on file with the SEC. In the opinion of management, all adjustments, consisting only of normal recurring adjustments necessary for a fair presentation of the Company’s condensed consolidated financial position as of September 30, 2015 and condensed consolidated results of operations and cash flows for the three and nine months ended September 30, 2015 and 2014 have been made. The results of operations for the three and nine months ended September 30, 2015 are not necessarily indicative of the results of operations that may be expected for the year ending December 31, 2015.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates, assumptions and judgments that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the consolidated financial statements, and the reported amounts of expenses during the reporting periods. Significant estimates, assumptions and judgments reflected in these condensed consolidated financial statements include, but are not limited to, the accrual of research and development expenses, the valuation of common stock prior to the IPO and the valuation of stock-based awards. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. Actual results could differ from the Company’s estimates.
Fair Value Measurements	Fair Value Measurements The following tables present information about the Company’s financial assets that have been measured at fair value at September 30, 2015 and December 31, 2014, and indicate the fair value of the hierarchy of the valuation inputs utilized to determine such fair value. In general, fair values determined by Level 1 inputs utilize quoted prices (unadjusted) in active markets for identical assets or liabilities. Fair value determined by Level 2 inputs utilize observable inputs other than Level 1 prices, such as quoted prices, for similar assets or liabilities, quoted market prices in markets that are not active or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the related assets or liabilities. Fair values determined by Level 3 inputs are unobservable data points for the asset or liability, and includes situations where there is little, if any, market activity for the asset or liability. The following tables summarize the Company’s cash equivalents and marketable securities as of September 30, 2015 and December 31, 2014: September 30, 2015 Quoted Significant Prices in Other Significant Active Observable Unobservable Markets Inputs Inputs Total (Level 1) (Level 2) (Level 3) Cash equivalents: Money market funds $ 21,812 $ 21,812 $ — $ — Commercial paper 6,499 — 6,499 — Corporate bonds 1,254 — 1,254 — Total cash equivalents 29,565 21,812 7,753 — Marketable securities: Corporate bonds 121,220 — 121,220 — Commercial paper 32,968 — 32,968 U.S. government securities 11,003 — 11,003 — Total marketable securities 165,191 — 165,191 — Total cash equivalents and marketable securities $ 194,756 $ 21,812 $ 172,944 $ — December 31, 2014 Quoted Significant Prices in Other Significant Active Observable Unobservable Markets Inputs Inputs Total (Level 1) (Level 2) (Level 3) Cash equivalents: Money market funds $ 14,742 $ 14,742 $ — $ — U.S. government securities 27,767 — 27,767 — Total cash equivalents 42,509 14,742 27,767 — Marketable securities: U.S. government securities 34,191 — 34,191 — Corporate bonds 22,168 — 22,168 — Commercial paper 1,000 — 1,000 — Total marketable securities 57,359 — 57,359 — Total cash equivalents and marketable securities $ 99,868 $ 14,742 $ 85,126 $ —
Marketable Securities	Marketable Securities The following tables summarize the Company’s marketable securities as of September 30, 2015 and December 31, 2014: September 30, 2015 Gross Gross Amortized Unrealized Unrealized Cost Gains Losses Fair Value Assets: Corporate bonds (due within 1 year) $ 107,034 $ — $ (36 ) $ 106,998 Corporate bonds (due after 1 year through 2 years) 14,216 6 — 14,222 Commercial paper (due within 1 year) 32,970 — (2 ) 32,968 U.S. government securities (due within 1 year) 11,003 — — 11,003 $ 165,223 $ 6 $ (38 ) $ 165,191 December 31, 2014 Gross Gross Amortized Unrealized Unrealized Cost Gains Losses Fair Value Assets: U.S. government securities (due within 1 year) $ 34,200 $ — $ (9 ) $ 34,191 Corporate bonds (due within 1 year) 18,716 — (18 ) 18,698 Corporate bonds (due after 1 year through 2 years) 3,478 — (8 ) 3,470 Commercial paper (due within 1 year) 1,000 — — 1,000 $ 57,394 $ — $ (35 ) $ 57,359
Income (Loss) Per Share	Income (Loss) Per Share Upon the closing of the Company’s IPO in June 2014, all of the Company’s outstanding redeemable convertible preferred shares were converted into shares of common stock. Prior to this conversion, the Company followed the two-class method when computing net income (loss) per share as the Company had issued shares that meet the definition of participating securities. The two-class method determines net income (loss) per share for each class of common and participating securities according to dividends declared or accumulated and participation rights in undistributed earnings. The two-class method requires income available to common stockholders for the period to be allocated between common and participating securities based upon their respective rights to receive dividends as if all income for the period had been distributed. The Company’s redeemable convertible preferred shares contractually entitled the holders of such shares to participate in dividends, but did not contractually require the holders of such shares to participate in losses of the Company. Accordingly, the two-class method did not apply for periods in which the Company reported a net loss or a net loss attributable to common stockholders resulting from dividends or accretion related to its redeemable convertible preferred shares. Basic net income (loss) per share attributable to common stockholders is computed by dividing the net income (loss) attributable to common stockholders by the weighted average number of common shares outstanding for the period. Diluted net income (loss) per share attributable to common stockholders is computed by dividing the diluted net income (loss) attributable to common stockholders by the weighted average number of common shares outstanding, including potential dilutive common shares assuming the dilutive effect of outstanding stock options and unvested restricted common shares, as determined using the treasury stock method. For periods in which the Company has reported net losses, diluted net loss per common share attributable to common stockholders is the same as basic net loss per common share attributable to common stockholders, since dilutive common shares are not assumed to have been issued if their effect is antidilutive. The Company reported a net loss attributable to common stockholders for the three and nine months ended September 30, 2015 and 2014. Basic and diluted net loss per share attributable to common stockholders was calculated as follows: For the three months ended For the nine months ended 2015 2014 2015 2014 Basic and diluted net loss per share attributable to common stockholders: Numerator: Net loss $ (19,884 ) $ (14,689 ) $ (51,112 ) $ (25,547 ) Accretion of redeemable convertible preferred stock to redemption value — — — (92 ) Net loss attributable to common stockholders $ (19,884 ) $ (14,689 ) $ (51,112 ) $ (25,639 ) Denominator: Weighted average of common shares outstanding, basic and diluted 27,138,667 22,707,012 26,593,646 8,618,793 Net loss per share attributable to common stockholders, basic and diluted $ (0.73 ) $ (0.65 ) $ (1.92 ) $ (2.97 ) The following common stock equivalents outstanding (prior to consideration of the treasury stock method) as of September 30, 2015 and 2014, were excluded from the computation of diluted net loss per share for the three and nine months ended September 30, 2015 and 2014, because they had an anti-dilutive impact: As of September 30, 2015 2014 Options to purchase common stock 2,574,132 1,839,895 Unvested restricted stock 1,935 — 2,576,067 1,839,895
Recently Issued and Adopted Accounting Pronouncements	Recently Issued and Adopted Accounting Pronouncements In August 2014, the Financial Accounting Standards Board issued Accounting Standards Update No. 2014-15, Presentation of Financial Statements — Going Concern (Subtopic 205-40). The new guidance addresses 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. Management’s evaluation should be based on relevant conditions and events that are known and reasonably knowable at the date that the financial statements are issued. The standard will be effective for the first interim period within annual reporting periods beginning after December 15, 2016. Early adoption is permitted. The Company is evaluating the effect that this guidance will have on its condensed consolidated financial statements.

Summary of Significant Accoun17

Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2015
Accounting Policies [Abstract]
Summary of Cash Equivalents and Marketable Securities	The following tables summarize the Company’s cash equivalents and marketable securities as of September 30, 2015 and December 31, 2014: September 30, 2015 Quoted Significant Prices in Other Significant Active Observable Unobservable Markets Inputs Inputs Total (Level 1) (Level 2) (Level 3) Cash equivalents: Money market funds $ 21,812 $ 21,812 $ — $ — Commercial paper 6,499 — 6,499 — Corporate bonds 1,254 — 1,254 — Total cash equivalents 29,565 21,812 7,753 — Marketable securities: Corporate bonds 121,220 — 121,220 — Commercial paper 32,968 — 32,968 U.S. government securities 11,003 — 11,003 — Total marketable securities 165,191 — 165,191 — Total cash equivalents and marketable securities $ 194,756 $ 21,812 $ 172,944 $ — December 31, 2014 Quoted Significant Prices in Other Significant Active Observable Unobservable Markets Inputs Inputs Total (Level 1) (Level 2) (Level 3) Cash equivalents: Money market funds $ 14,742 $ 14,742 $ — $ — U.S. government securities 27,767 — 27,767 — Total cash equivalents 42,509 14,742 27,767 — Marketable securities: U.S. government securities 34,191 — 34,191 — Corporate bonds 22,168 — 22,168 — Commercial paper 1,000 — 1,000 — Total marketable securities 57,359 — 57,359 — Total cash equivalents and marketable securities $ 99,868 $ 14,742 $ 85,126 $ —
Summary of Marketable Securities	The following tables summarize the Company’s marketable securities as of September 30, 2015 and December 31, 2014: September 30, 2015 Gross Gross Amortized Unrealized Unrealized Cost Gains Losses Fair Value Assets: Corporate bonds (due within 1 year) $ 107,034 $ — $ (36 ) $ 106,998 Corporate bonds (due after 1 year through 2 years) 14,216 6 — 14,222 Commercial paper (due within 1 year) 32,970 — (2 ) 32,968 U.S. government securities (due within 1 year) 11,003 — — 11,003 $ 165,223 $ 6 $ (38 ) $ 165,191 December 31, 2014 Gross Gross Amortized Unrealized Unrealized Cost Gains Losses Fair Value Assets: U.S. government securities (due within 1 year) $ 34,200 $ — $ (9 ) $ 34,191 Corporate bonds (due within 1 year) 18,716 — (18 ) 18,698 Corporate bonds (due after 1 year through 2 years) 3,478 — (8 ) 3,470 Commercial paper (due within 1 year) 1,000 — — 1,000 $ 57,394 $ — $ (35 ) $ 57,359
Computation of Basic and Diluted Earnings Per Share	Basic and diluted net loss per share attributable to common stockholders was calculated as follows: For the three months ended For the nine months ended 2015 2014 2015 2014 Basic and diluted net loss per share attributable to common stockholders: Numerator: Net loss $ (19,884 ) $ (14,689 ) $ (51,112 ) $ (25,547 ) Accretion of redeemable convertible preferred stock to redemption value — — — (92 ) Net loss attributable to common stockholders $ (19,884 ) $ (14,689 ) $ (51,112 ) $ (25,639 ) Denominator: Weighted average of common shares outstanding, basic and diluted 27,138,667 22,707,012 26,593,646 8,618,793 Net loss per share attributable to common stockholders, basic and diluted $ (0.73 ) $ (0.65 ) $ (1.92 ) $ (2.97 )
Summary of Common Stock Equivalents Outstanding	The following common stock equivalents outstanding (prior to consideration of the treasury stock method) as of September 30, 2015 and 2014, were excluded from the computation of diluted net loss per share for the three and nine months ended September 30, 2015 and 2014, because they had an anti-dilutive impact: As of September 30, 2015 2014 Options to purchase common stock 2,574,132 1,839,895 Unvested restricted stock 1,935 — 2,576,067 1,839,895

Accrued Expenses (Tables)

Accrued Expenses (Tables)	9 Months Ended
	Sep. 30, 2015
Payables and Accruals [Abstract]
Schedule of Accrued Expenses	Accrued expenses consisted of the following: September 30, December 31, 2015 2014 Accrued research and development expenses $ 3,808 $ 1,180 Accrued payroll and related expenses 1,924 1,239 Accrued professional fees 705 585 Accrued other 119 168 $ 6,556 $ 3,172

Notes Payable (Tables)

Notes Payable (Tables)	9 Months Ended
	Sep. 30, 2015
Debt Disclosure [Abstract]
Schedule of Estimated Future Principal Payments	As of September 30, 2015, estimated future principal payments due are as follows: Years Ending December 31, 2015 $ 697 2016 2,936 2017 3,183 $ 6,816
Schedule of Notes Payable	As of September 30, 2015 and December 31, 2014, notes payable consist of the following: September 30, December 31, 2015 2014 Notes payable $ 6,816 $ 7,500 Less: current portion (2,877 ) (1,381 ) Notes payable, net of current portion 3,939 6,119 Debt discount, net of accretion (46 ) (79 ) Accretion related to final payment 269 137 Notes payable, net of discount, long term $ 4,162 $ 6,177

Stock-Based Awards (Tables)

Stock-Based Awards (Tables)	9 Months Ended
	Sep. 30, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Summary of Stock-Based Compensation Expense Related to Stock Options and Restricted Common Stock	The Company recorded stock-based compensation expense related to stock options and restricted common stock in the following expense categories of its condensed consolidated statements of operations: Three Months Ended Nine Months Ended September 30, September 30, 2015 2014 2015 2014 Research and development $ 895 $ 91 $ 2,037 $ 259 General and administrative 1,946 375 3,800 651 $ 2,841 $ 466 $ 5,837 $ 910

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2015
Commitments and Contingencies Disclosure [Abstract]
Schedule of Future Minimum Lease Payments for Operating Leases	Future minimum lease payments for its operating lease as of September 30, 2015 are as follows: Years Ending December 31, 2015 $ 107 2016 335 2017 199 $ 641

Nature of the Business and Ba22

Nature of the Business and Basis of Presentation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	Jan. 28, 2015	Jun. 24, 2014	Jan. 31, 2015	Sep. 30, 2015	Sep. 30, 2014
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Entity incorporation date				Nov. 22, 2005
Proceeds from public offerings, net of commissions and underwriting discounts		$ 102,672		$ 129,571	$ 102,672
Offering costs		$ 2,508
Underwriting discounts, commissions and offering costs incurred					$ 2,312
IPO [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Common stock issued		6,900,000
Common stock issued price per share		$ 16
Follow-on Offering [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Common stock issued	3,942,200		3,942,200
Common stock issued price per share	$ 35		$ 35
Proceeds from offering, net of commissions and underwriting discounts	$ 130,044		$ 130,044
Underwriting discounts, commissions and offering costs incurred	$ 473		$ 473

Summary of Significant Accoun23

Summary of Significant Accounting Policies - Summary of Cash Equivalents and Marketable Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	$ 29,565	$ 42,509
Marketable securities	165,191	57,359
Total cash equivalents and marketable securities	194,756	99,868
Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	21,812	14,742
U.S. Government Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		27,767
Marketable securities	11,003	34,191
Corporate Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	1,254
Marketable securities	121,220	22,168
Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	6,499
Marketable securities	32,968	1,000
Quoted Prices in Active Markets, (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	21,812	14,742
Total cash equivalents and marketable securities	21,812	14,742
Quoted Prices in Active Markets, (Level 1) [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	21,812	14,742
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	7,753	27,767
Marketable securities	165,191	57,359
Total cash equivalents and marketable securities	172,944	85,126
Significant Other Observable Inputs (Level 2) [Member] | U.S. Government Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		27,767
Marketable securities	11,003	34,191
Significant Other Observable Inputs (Level 2) [Member] | Corporate Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	1,254
Marketable securities	121,220	22,168
Significant Other Observable Inputs (Level 2) [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	6,499
Marketable securities	$ 32,968	$ 1,000

Summary of Significant Accoun24

Summary of Significant Accounting Policies - Additional Information (Detail)	Sep. 30, 2015USD ($)
Accounting Policies [Abstract]
Transfer from level 1 to level 2, financial assets	$ 0
Transfer from level 2 to level 1, financial assets	$ 0

Summary of Significant Accoun25

Summary of Significant Accounting Policies - Summary of Marketable Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 165,223	$ 57,394
Gross Unrealized Gains	6
Gross Unrealized Losses	(38)	(35)
Fair Value	165,191	57,359
U.S. Government Securities (Due within 1 Year) [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	11,003	34,200
Gross Unrealized Losses		(9)
Fair Value	11,003	34,191
Corporate Bonds (Due within 1 Year) [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	107,034	18,716
Gross Unrealized Losses	(36)	(18)
Fair Value	106,998	18,698
Corporate Bonds (Due After 1 Year Through 2 Years) [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	14,216	3,478
Gross Unrealized Gains	6
Gross Unrealized Losses		(8)
Fair Value	14,222	3,470
Commercial Paper (Due within 1 Year) [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	32,970	1,000
Gross Unrealized Losses	(2)
Fair Value	$ 32,968	$ 1,000

Summary of Significant Accoun26

Summary of Significant Accounting Policies - Computation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Numerator:
Net loss	$ (19,884)	$ (14,689)	$ (51,112)	$ (25,547)
Accretion of redeemable convertible preferred stock to redemption value				(92)
Net loss attributable to common stockholders	$ (19,884)	$ (14,689)	$ (51,112)	$ (25,639)
Denominator:
Weighted average of common shares outstanding, basic and diluted	27,138,667	22,707,012	26,593,646	8,618,793
Net loss per share attributable to common stockholders, basic and diluted	$ (0.73)	$ (0.65)	$ (1.92)	$ (2.97)

Summary of Significant Accoun27

Summary of Significant Accounting Policies - Summary of Common Stock Equivalents Outstanding (Detail) - shares	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from computation of earnings per share	2,576,067	1,839,895
Options to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from computation of earnings per share	2,574,132	1,839,895
Unvested Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from computation of earnings per share	1,935

Accrued Expenses - Schedule of

Accrued Expenses - Schedule of Accrued Expenses (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Payables and Accruals [Abstract]
Accrued research and development expenses	$ 3,808	$ 1,180
Accrued payroll and related expenses	1,924	1,239
Accrued professional fees	705	585
Accrued other	119	168
Accrued expenses	$ 6,556	$ 3,172

Notes Payable - Schedule of Not

Notes Payable - Schedule of Notes Payable (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Notes payable	$ 6,816	$ 7,500
Less: current portion	(2,877)	(1,381)
Notes payable, net of current portion	3,939	6,119
Notes payable, net of current portion	3,939	6,119
Notes payable, net of discount, long term	4,162	6,177
Secured Debt [Member] | Credit Facility [Member]
Debt Instrument [Line Items]
Debt discount, net of accretion	(46)	(79)
Accretion related to final payment	$ 269	$ 137

Notes Payable - Additional Info

Notes Payable - Additional Information (Detail) - Credit Facility [Member] - Secured Debt [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Debt Instrument [Line Items]
Interest expense on credit facility	$ 200	$ 213	$ 626	$ 658
Effective annual interest rate	14.00%		14.00%

Notes Payable - Schedule of Est

Notes Payable - Schedule of Estimated Future Principal Payments (Detail) $ in Thousands	Sep. 30, 2015USD ($)
Debt Instruments [Abstract]
2,015	$ 697
2,016	2,936
2,017	3,183
Total	$ 6,816

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	Jan. 28, 2015	Jan. 31, 2015	Sep. 30, 2014
Underwriting discounts, commissions and offering costs incurred			$ 2,312
Follow-on Offering [Member]
Common stock issued	3,942,200	3,942,200
Common stock issued price per share	$ 35	$ 35
Shares issued related to the exercise of over allotment option by underwriters		514,200
Proceeds from offering, net of commissions and underwriting discounts	$ 130,044	$ 130,044
Underwriting discounts, commissions and offering costs incurred	$ 473	$ 473

Stock-Based Awards - Additional

Stock-Based Awards - Additional Information (Detail) - USD ($) $ in Thousands	Jan. 01, 2015	Sep. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for grant		968,298
Unrecognized stock-based compensation cost		$ 31,069
Stock-based compensation recognized weighted average period		3 years 1 month 6 days
Employees and Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for grant		964,298
Consultant [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for grant		4,000
Nonemployee Service Based Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of outstanding unvested shares held by nonemployees		11,458
2014 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for grant		257,460
2014 Stock Option and Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for grant		1,615,599
Shares added to plan	915,166

Stock-Based Awards - Summary of

Stock-Based Awards - Summary of Stock-Based Compensation Expense Related to Stock Options and Restricted Common Stock (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 2,841	$ 466	$ 5,837	$ 910
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	895	91	2,037	259
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 1,946	$ 375	$ 3,800	$ 651

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail)	1 Months Ended	3 Months Ended		9 Months Ended
	Mar. 31, 2015Option	Sep. 30, 2015USD ($)	Sep. 30, 2014USD ($)	Sep. 30, 2015USD ($)	Sep. 30, 2014USD ($)
Commitment And Contingencies [Line Items]
Operating lease, rental expense		$ 83,000	$ 52,000	$ 220,000	$ 104,000
Subsequent Licensed Product [Member]
Commitment And Contingencies [Line Items]
Licensing fees per product maximum		1,250,000		$ 1,250,000
Office Space [Member]
Commitment And Contingencies [Line Items]
Lease expiration date				Jul. 31, 2017
Lease extension period				3 years
Additional Office Space [Member]
Commitment And Contingencies [Line Items]
Lease expiration date	Jul. 31, 2017
Lease extension period	3 years
Number of options to extend lease | Option	2
Maximum [Member] | Pre Commercialization Milestones [Member]
Commitment And Contingencies [Line Items]
Milestone payments		12,250,000		$ 12,250,000
Maximum [Member] | Product Commercialization Milestones [Member]
Commitment And Contingencies [Line Items]
Milestone payments		$ 12,500,000		$ 12,500,000

Commitments and Contingencies36

Commitments and Contingencies - Schedule of Future Minimum Lease Payments for Operating Leases (Detail) $ in Thousands	Sep. 30, 2015USD ($)
Commitments and Contingencies Disclosure [Abstract]
2,015	$ 107
2,016	335
2,017	199
Total	$ 641

Retirement Plan - Additional In

Retirement Plan - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Compensation and Retirement Disclosure [Abstract]
Percentage of employer's contribution on employee's base salary			2.00%
Contribution expense	$ 32	$ 17	$ 111	$ 43

Australia Research and Develo38

Australia Research and Development Tax Incentive - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Operating Loss Carryforwards [Line Items]
Unrealized foreign currency transaction gains (losses)			$ (145)	$ (31)
Research Tax Credit Carryforward [Member]
Operating Loss Carryforwards [Line Items]
Percentage of refundable tax incentive			45.00%
Reduction to research and development expenses	$ 376	$ 91	$ 1,063	164
Unrealized foreign currency transaction gains (losses)	(107)	$ (95)	$ (145)	$ (31)
Australia [Member] | Research Tax Credit Carryforward [Member]
Operating Loss Carryforwards [Line Items]
Percentage of reduction in research and development costs			45.00%
Tax incentive receivable	$ 1,309		$ 1,309		$ 391