Larimar Therapeutics (LRMR) 10-Q 14 May 15 2015 Q1 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	3 Months Ended
	Mar. 31, 2015	Apr. 30, 2015
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	FALSE
Document Period End Date	31-Mar-15
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q1
Trading Symbol	ZFGN
Entity Registrant Name	Zafgen, Inc.
Entity Central Index Key	1374690
Current Fiscal Year End Date	-19
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		26,894,157

Condensed_Consolidated_Balance

Condensed Consolidated Balance Sheets (Unaudited) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Current assets:
Cash and cash equivalents	$106,934	$58,103
Marketable Securities	127,267	57,359
Tax incentive receivable	391	391
Prepaid expenses and other current assets	1,734	1,345
Total current assets	236,326	117,198
Property and equipment, net	101	79
Tax incentive receivable	205
Other assets	89	242
Total assets	236,721	117,519
Current liabilities:
Accounts payable	3,404	2,348
Accrued expenses	4,034	3,172
Notes payable, current	2,093	1,381
Total current liabilities	9,531	6,901
Notes payable, net of discount, long-term	5,521	6,177
Total liabilities	15,052	13,078
Commitments and contingencies (Note 7)
Stockholders' equity
Preferred stock; $0.001 par value; 5,000,000 shares authorized at March 31, 2015 and December 31, 2014; no shares issued and outstanding at March 31, 2015 and December 31, 2014
Common stock, $0.001 par value; 115,000,000 shares authorized at March 31, 2015 and December 31, 2014; 26,856,329 and 22,879,160 shares issued and outstanding at March 31, 2015 and December 31, 2014, respectively	27	23
Additional paid-in capital	340,538	209,838
Accumulated deficit	-118,857	-105,385
Accumulated other comprehensive loss	-39	-35
Total stockholders' equity	221,669	104,441
Total liabilities and stockholders' equity	$236,721	$117,519

Condensed_Consolidated_Balance1

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) (USD $)	Mar. 31, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Preferred stock, par value	$0.00	$0.00
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	$0.00	$0.00
Common stock, shares authorized	115,000,000	115,000,000
Common stock, shares issued	26,856,329	22,879,160
Common stock, shares outstanding	26,856,329	22,879,160

Condensed_Consolidated_Stateme

Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) (USD $)	3 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Income Statement [Abstract]
Revenue	$0	$0
Operating expenses:
Research and development	10,215	3,275
General and administrative	3,025	1,246
Total operating expenses	13,240	4,521
Loss from operations	-13,240	-4,521
Other income (expense):
Interest income	39
Interest expense	-213	-2
Foreign currency transaction gains (losses), net	-58	65
Total other income (expense), net	-232	63
Net loss	-13,472	-4,458
Accretion of redeemable convertible preferred stock to redemption value		-49
Net loss attributable to common stockholders	-13,472	-4,507
Net loss per share attributable to common stockholders, basic and diluted	($0.53)	($6.18)
Weighted average common shares outstanding, basic and diluted	25,615,282	729,391
Comprehensive loss:
Net loss	-13,472	-4,458
Other comprehensive loss:
Unrealized loss on marketable securities	-4
Total other comprehensive loss	-4
Total comprehensive loss	($13,476)	($4,458)

Condensed_Consolidated_Stateme1

Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Cash flows from operating activities:
Net loss	($13,472)	($4,458)
Adjustments to reconcile net loss to net cash used in operating activities
Stock-based compensation expense	1,057	176
Non-cash interest expense	16
Depreciation expense	5	3
Unrealized foreign currency transaction (gains) losses	24	-42
Premium on purchases of marketable securities	-341
Amortization of premium on marketable securities	131
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	-389	-44
Tax incentive receivable	-229	506
Accounts payable	1,121	-511
Accrued expenses	990	350
Net cash used in operating activities	-11,087	-4,020
Cash flows from investing activities:
Purchase of marketable securities	-98,952
Proceeds from maturities of marketable securities	29,250
Purchases of property and equipment	-27	-5
Net cash used in investing activities	-69,729	-5
Cash flows from financing activities:
Proceeds from issuance of redeemable convertible preferred stock		442
Proceeds from issuance of notes payable, net of issuance costs		7,376
Proceeds from exercise of common stock options and issuance of common stock pursuant to employee stock purchase plan	76
Proceeds from public offering, net	129,571
Payments of deferred offering costs		-827
Net cash provided by financing activities	129,647	6,991
Net increase in cash and cash equivalents	48,831	2,966
Cash and cash equivalents at beginning of period	58,103	35,517
Cash and cash equivalents at end of period	106,934	38,483
Supplemental disclosure of non-cash investing and financing activities:
Accretion of redeemable convertible preferred stock to redemption values		49
Deferred offering costs included in accounts payable and accrued expenses		$362

Nature_of_the_Business_and_Bas

Nature of the Business and Basis of Presentation	3 Months Ended
	Mar. 31, 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. 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.
	The accompanying condensed consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”).
	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 and 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 $129,571 based upon the price of $35.00 per share after deducting underwriting discounts and commissions, and offering expenses of $473.
	Unaudited Interim Financial Information
	The condensed consolidated balance sheet at December 31, 2014 was derived from audited financial statements, but does not include all disclosures required by GAAP. The accompanying unaudited condensed consolidated financial statements as of March 31, 2015 and for the three months ended March 31, 2015 and 2014, have been prepared by the Company, pursuant to the rules and regulations of the 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 March 31, 2015 and condensed consolidated results of operations and cash flows for the three months ended March 31, 2015 and 2014 have been made. The results of operations for the three months ended March 31, 2015 are not necessarily indicative of the results of operations that may be expected for the year ending December 31, 2015.

Summary_of_Significant_Account

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 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 March 31, 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 March 31, 2015 and December 31, 2014:
		March 31, 2015
		Total			Quoted			Significant			Significant
					Prices in			Other			Unobservable
					Active			Observable			Inputs
					Markets			Inputs			(Level 3)
					(Level 1)			(Level 2)
	Cash equivalents:
	Money market funds	$	4,179		$	4,179		$	—		$	—
	U.S. government securities		4,700			—			4,700			—
	Corporate bonds		3,503			—			3,503			—
	Total cash equivalents		12,382			4,179			8,203			—
	Marketable securities:
	U.S. government securities		80,085			—			80,085			—
	Corporate bonds		40,187			—			40,187			—
	Commercial paper		6,995			—			6,995			—
	Total marketable securities		127,267			—			127,267			—
	Total cash equivalents and marketable securities	$	139,649		$	4,179		$	135,470		$	—
		December 31, 2014
		Total			Quoted			Significant			Significant
					Prices in			Other			Unobservable
					Active			Observable			Inputs
					Markets			Inputs			(Level 3)
					(Level 1)			(Level 2)
	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 months ended March 31, 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 table summarizes the Company’s marketable securities as of March 31, 2015 and December 31, 2014:
		March 31, 2015
	Assets:	Amortized			Gross			Gross			Fair Value
		Cost			Unrealized			Unrealized
					Gains			Losses
	U.S. government securities (due within 1 year)	$	80,098		$	—		$	(13	)	$	80,085
	Corporate bonds (due within 1 year)		37,752			—			(22	)		37,730
	Corporate bonds (due after 1 year through 2 years)		2,460			—			(3	)		2,457
	Commercial paper (due within 1 year)		6,996			—			(1	)		6,995
		$	127,306		$	—		$	(39	)	$	127,267
		December 31, 2014
	Assets:	Amortized			Gross			Gross			Fair Value
		Cost			Unrealized			Unrealized
					Gains			Losses
	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, 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 months ended March 31, 2015 and 2014.
Basic and diluted net loss per share attributable to common stockholders was calculated as follows:
	Three Months Ended March 31,
	2015			2014
Basic and diluted net loss per share attributable to common stockholders:
Numerator:
Net loss	$	(13,472	)	$	(4,458	)
Accretion of redeemable convertible preferred stock to redemption value		—			(49	)
Net loss attributable to common stockholders	$	(13,472	)	$	(4,507	)
Denominator:
Weighted average common shares outstanding, basic and diluted		25,615,282			729,391
Net loss per share attributable to common stockholders, basic and diluted	$	(0.53	)	$	(6.18	)
The following common stock equivalents outstanding (prior to consideration of the treasury stock method) as of March 31, 2015 and 2014, were excluded from the computation of diluted net loss per share for the three months ended March 31, 2015 and 2014, because they had an anti-dilutive impact:
	As of March 31,
	2015			2014
Options to purchase common stock		2,589,767			1,513,353
Unvested restricted common stock		3,870			—
		2,593,637			1,513,353
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 consolidated financial statements.

Accrued_Expenses

Accrued Expenses	3 Months Ended
	Mar. 31, 2015
Payables and Accruals [Abstract]
Accrued Expenses	3. Accrued Expenses
	Accrued expenses consisted of the following:
		March 31,		December 31,
		2015		2014
	Accrued payroll and related expenses	$	543	$	1,239
	Accrued research and development expenses		2,828		1,180
	Accrued professional fees		371		585
	Accrued other		292		168
		$	4,034	$	3,172

Notes_Payable

Notes Payable	3 Months Ended
	Mar. 31, 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 debt 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 March 31, 2015 and December 31, 2014, notes payable consist of the following:
		March 31,			December 31,
		2015			2014
	Notes payable	$	7,500		$	7,500
	Less: current portion		(2,093	)		(1,381	)
	Notes payable, net of current portion		5,407			6,119
	Debt discount, net of accretion		(67	)		(79	)
	Accretion related to final payment		181			137
	Notes payable, net of discount, long term	$	5,521		$	6,177
	As of March 31, 2015, estimated future principal payments due are as follows:
	Years Ending December 31,
	2015	$	1,381
	2016		2,936
	2017		3,183
		$	7,500
	During the three months ended March 31, 2015 and 2014, the Company recognized $213 and $2, 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	3 Months Ended
	Mar. 31, 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 504,200 shares related to the exercise of the over-allotment option by the underwriters. Net proceeds were $129,571 after deducting underwriting discounts and commissions, and offering expenses of $473.

StockBased_Awards

Stock-Based Awards	3 Months Ended
	Mar. 31, 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 March 31, 2015, 1,970,599 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 262,136 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 statements of operations:
		Three Months Ended March 31,
		2015		2014
	Research and development	$	404	$	69
	General and administrative		653		107
		$	1,057	$	176
	As of March 31, 2015, the Company had an aggregate of $26,317 of unrecognized stock-based compensation cost, which is expected to be recognized over a weighted average period of 3.7 years. As of March 31, 2015, there were outstanding unvested service-based stock options held by nonemployees for the purchase of 10,683 shares of common stock.

Commitments_and_Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 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.
	Future minimum lease payments for its operating lease as of March 31, 2015 are as follows:
	Years Ending December 31,
	2015	$	172
	2016		235
	2017		139
		$	546
	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. As a result payments under operating lease will increase by $70 in 2015, $100 in 2016 and $60 in 2017.
	During the three months ended March 31, 2015 and 2014, the Company recognized $58 and $25, 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 March 31, 2015, the Company is obligated to make milestone payments of up to $12,250 upon reaching certain pre-commercialization milestones, such as clinical trials and government approvals, 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 March 31, 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 March 31, 2015.

Retirement_Plan

Retirement Plan	3 Months Ended
	Mar. 31, 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 March 31, 2015 and 2014, the Company recognized $45 and $13, respectively, of expense related to its contributions to this plan.

Australia_Research_and_Develop

Australia Research and Development Tax Incentive	3 Months Ended
	Mar. 31, 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 March 31, 2015 and 2014, $229 and $26, 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 March 31, 2015 and 2014, the Company recorded in its condensed consolidated statements of operations unrealized foreign currency exchange gains (losses) of $(24) and $42, respectively, related to this tax incentive receivable. As of March 31, 2015 and December 31, 2014, the Company’s tax incentive receivable from the Australian government was $596 and $391, respectively.

Nature_of_the_Business_and_Bas1

Nature of the Business and Basis of Presentation (Policies)	3 Months Ended
	Mar. 31, 2015
Accounting Policies [Abstract]
Unaudited Interim Financial Information	Unaudited Interim Financial Information
	The condensed consolidated balance sheet at December 31, 2014 was derived from audited financial statements, but does not include all disclosures required by GAAP. The accompanying unaudited condensed consolidated financial statements as of March 31, 2015 and for the three months ended March 31, 2015 and 2014, have been prepared by the Company, pursuant to the rules and regulations of the 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 March 31, 2015 and condensed consolidated results of operations and cash flows for the three months ended March 31, 2015 and 2014 have been made. The results of operations for the three months ended March 31, 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 March 31, 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 March 31, 2015 and December 31, 2014:
		March 31, 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	$	4,179		$	4,179		$	—		$	—
	U.S. government securities		4,700			—			4,700			—
	Corporate bonds		3,503			—			3,503			—
	Total cash equivalents		12,382			4,179			8,203			—
	Marketable securities:
	U.S. government securities		80,085			—			80,085			—
	Corporate bonds		40,187			—			40,187			—
	Commercial paper		6,995			—			6,995			—
	Total marketable securities		127,267			—			127,267			—
	Total cash equivalents and marketable securities	$	139,649		$	4,179		$	135,470		$	—
		December 31, 2014
		Total			Quoted			Significant			Significant
					Prices in			Other			Unobservable
					Active			Observable			Inputs
					Markets			Inputs			(Level 3)
					(Level 1)			(Level 2)
	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 months ended March 31, 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	Marketable Securities
	The following table summarizes the Company’s marketable securities as of March 31, 2015 and December 31, 2014:
		March 31, 2015
		Amortized			Gross			Gross			Fair Value
		Cost			Unrealized			Unrealized
					Gains			Losses
	Assets:
	U.S. government securities (due within 1 year)	$	80,098		$	—		$	(13	)	$	80,085
	Corporate bonds (due within 1 year)		37,752			—			(22	)		37,730
	Corporate bonds (due after 1 year through 2 years)		2,460			—			(3	)		2,457
	Commercial paper (due within 1 year)		6,996			—			(1	)		6,995
		$	127,306		$	—		$	(39	)	$	127,267
		December 31, 2014
		Amortized			Gross			Gross			Fair Value
		Cost			Unrealized			Unrealized
					Gains			Losses
	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
Net Income (Loss) Per Share	Net 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, 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 months ended March 31, 2015 and 2014.
	Basic and diluted net loss per share attributable to common stockholders was calculated as follows:
		Three Months Ended March 31,
		2015			2014
	Basic and diluted net loss per share attributable to common stockholders:
	Numerator:
	Net loss	$	(13,472	)	$	(4,458	)
	Accretion of redeemable convertible preferred stock to redemption value		—			(49	)
	Net loss attributable to common stockholders	$	(13,472	)	$	(4,507	)
	Denominator:
	Weighted average common shares outstanding, basic and diluted		25,615,282			729,391
	Net loss per share attributable to common stockholders, basic and diluted	$	(0.53	)	$	(6.18	)
	The following common stock equivalents outstanding (prior to consideration of the treasury stock method) as of March 31, 2015 and 2014, were excluded from the computation of diluted net loss per share for the three months ended March 31, 2015 and 2014, because they had an anti-dilutive impact:
		As of March 31,
		2015			2014
	Options to purchase common stock		2,589,767			1,513,353
	Unvested restricted common stock		3,870			—
			2,593,637			1,513,353
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 consolidated financial statements.

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 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 March 31, 2015 and December 31, 2014:
		March 31, 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	$	4,179		$	4,179		$	—		$	—
	U.S. government securities		4,700			—			4,700			—
	Corporate bonds		3,503			—			3,503			—
	Total cash equivalents		12,382			4,179			8,203			—
	Marketable securities:
	U.S. government securities		80,085			—			80,085			—
	Corporate bonds		40,187			—			40,187			—
	Commercial paper		6,995			—			6,995			—
	Total marketable securities		127,267			—			127,267			—
	Total cash equivalents and marketable securities	$	139,649		$	4,179		$	135,470		$	—
		December 31, 2014
		Total			Quoted			Significant			Significant
					Prices in			Other			Unobservable
					Active			Observable			Inputs
					Markets			Inputs			(Level 3)
					(Level 1)			(Level 2)
	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 table summarizes the Company’s marketable securities as of March 31, 2015 and December 31, 2014:
		March 31, 2015
	Assets:	Amortized			Gross			Gross			Fair Value
		Cost			Unrealized			Unrealized
					Gains			Losses
	U.S. government securities (due within 1 year)	$	80,098		$	—		$	(13	)	$	80,085
	Corporate bonds (due within 1 year)		37,752			—			(22	)		37,730
	Corporate bonds (due after 1 year through 2 years)		2,460			—			(3	)		2,457
	Commercial paper (due within 1 year)		6,996			—			(1	)		6,995
		$	127,306		$	—		$	(39	)	$	127,267
		December 31, 2014
	Assets:	Amortized			Gross			Gross			Fair Value
		Cost			Unrealized			Unrealized
					Gains			Losses
	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:
		Three Months Ended March 31,
		2015			2014
	Basic and diluted net loss per share attributable to common stockholders:
	Numerator:
	Net loss	$	(13,472	)	$	(4,458	)
	Accretion of redeemable convertible preferred stock to redemption value		—			(49	)
	Net loss attributable to common stockholders	$	(13,472	)	$	(4,507	)
	Denominator:
	Weighted average common shares outstanding, basic and diluted		25,615,282			729,391
	Net loss per share attributable to common stockholders, basic and diluted	$	(0.53	)	$	(6.18	)
Summary of Common Stock Equivalents Outstanding	The following common stock equivalents outstanding (prior to consideration of the treasury stock method) as of March 31, 2015 and 2014, were excluded from the computation of diluted net loss per share for the three months ended March 31, 2015 and 2014, because they had an anti-dilutive impact:
		As of March 31,
		2015			2014
	Options to purchase common stock		2,589,767			1,513,353
	Unvested restricted common stock		3,870			—
			2,593,637			1,513,353

Accrued_Expenses_Tables

Accrued Expenses (Tables)	3 Months Ended
	Mar. 31, 2015
Payables and Accruals [Abstract]
Schedule of Accrued Expenses	Accrued expenses consisted of the following:
		March 31,		December 31,
		2015		2014
	Accrued payroll and related expenses	$	543	$	1,239
	Accrued research and development expenses		2,828		1,180
	Accrued professional fees		371		585
	Accrued other		292		168
		$	4,034	$	3,172

Notes_Payable_Tables

Notes Payable (Tables)	3 Months Ended
	Mar. 31, 2015
Debt Disclosure [Abstract]
Schedule of Notes Payable	As of March 31, 2015 and December 31, 2014, notes payable consist of the following:
		March 31,			December 31,
		2015			2014
	Notes payable	$	7,500		$	7,500
	Less: current portion		(2,093	)		(1,381	)
	Notes payable, net of current portion		5,407			6,119
	Debt discount, net of accretion		(67	)		(79	)
	Accretion related to final payment		181			137
	Notes payable, net of discount, long term	$	5,521		$	6,177
Schedule of Estimated Future Principal Payments	As of March 31, 2015, estimated future principal payments due are as follows:
	Years Ending December 31,
	2015	$	1,381
	2016		2,936
	2017		3,183
		$	7,500

StockBased_Awards_Tables

Stock-Based Awards (Tables)	3 Months Ended
	Mar. 31, 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 statements of operations:
		Three Months Ended March 31,
		2015		2014
	Research and development	$	404	$	69
	General and administrative		653		107
		$	1,057	$	176

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 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 March 31, 2015 are as follows:
	Years Ending December 31,
	2015	$	172
	2016		235
	2017		139
		$	546

Nature_of_the_Business_and_Bas2

Nature of the Business and Basis of Presentation - Additional Information (Detail) (USD $)	0 Months Ended	3 Months Ended		0 Months Ended	1 Months Ended
In Thousands, except Share data, unless otherwise specified	Jun. 24, 2014	Mar. 31, 2015	Mar. 31, 2014	Jan. 28, 2015	Jan. 31, 2015
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Entity incorporation date		22-Nov-05
Proceeds from offering, net of commissions and underwriting discounts	$102,672
Offering costs	2,508
Proceeds from offering, net of commissions and underwriting discounts		129,571
Underwriting discounts, commissions and offering expenses			827
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				129,571	129,571
Underwriting discounts, commissions and offering expenses				$473	$473

Summary_of_Significant_Account2

Summary of Significant Accounting Policies - Summary of Cash Equivalents and Marketable Securities (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Summary Of Significant Policies [Line Items]
Cash equivalents	$12,382	$42,509
Marketable Securities	127,267	57,359
Total cash equivalents and marketable securities	139,649	99,868
Money Market Funds [Member]
Summary Of Significant Policies [Line Items]
Cash equivalents	4,179	14,742
U.S. Government Securities [Member]
Summary Of Significant Policies [Line Items]
Cash equivalents	4,700	27,767
Marketable Securities	80,085	34,191
Corporate Bonds [Member]
Summary Of Significant Policies [Line Items]
Cash equivalents	3,503
Marketable Securities	40,187	22,168
Commercial Paper [Member]
Summary Of Significant Policies [Line Items]
Marketable Securities	6,995	1,000
Quoted Prices in Active Markets, (Level 1) [Member]
Summary Of Significant Policies [Line Items]
Cash equivalents	4,179	14,742
Total cash equivalents and marketable securities	4,179	14,742
Quoted Prices in Active Markets, (Level 1) [Member] | Money Market Funds [Member]
Summary Of Significant Policies [Line Items]
Cash equivalents	4,179	14,742
Significant Other Observable Inputs (Level 2) [Member]
Summary Of Significant Policies [Line Items]
Cash equivalents	8,203	27,767
Marketable Securities	127,267	57,359
Total cash equivalents and marketable securities	135,470	85,126
Significant Other Observable Inputs (Level 2) [Member] | U.S. Government Securities [Member]
Summary Of Significant Policies [Line Items]
Cash equivalents	4,700	27,767
Marketable Securities	80,085	34,191
Significant Other Observable Inputs (Level 2) [Member] | Corporate Bonds [Member]
Summary Of Significant Policies [Line Items]
Cash equivalents	3,503
Marketable Securities	40,187	22,168
Significant Other Observable Inputs (Level 2) [Member] | Commercial Paper [Member]
Summary Of Significant Policies [Line Items]
Marketable Securities	$6,995	$1,000

Summary_of_Significant_Account3

Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	Mar. 31, 2015
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_Account4

Summary of Significant Accounting Policies - Summary of Marketable Securities (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$127,306	$57,394
Gross Unrealized Gains	0	0
Gross Unrealized Losses	-39	-35
Fair Value	127,267	57,359
U.S. Government Securities (Due within 1 Year) [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	80,098	34,200
Gross Unrealized Gains	0	0
Gross Unrealized Losses	-13	-9
Fair Value	80,085	34,191
Corporate Bonds (Due within 1 Year) [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	37,752	18,716
Gross Unrealized Gains	0	0
Gross Unrealized Losses	-22	-18
Fair Value	37,730	18,698
Corporate Bonds (Due After 1 Year Through 2 Years) [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,460	3,478
Gross Unrealized Gains	0	0
Gross Unrealized Losses	-3	-8
Fair Value	2,457	3,470
Commercial Paper (Due within 1 Year) [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	6,996	1,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	-1
Fair Value	$6,995	$1,000

Summary_of_Significant_Account5

Summary of Significant Accounting Policies - Computation of Basic and Diluted Earnings Per Share (Detail) (USD $)	3 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Numerator:
Net loss	($13,472)	($4,458)
Accretion of redeemable convertible preferred stock to redemption value		-49
Net loss attributable to common stockholders	($13,472)	($4,507)
Denominator:
Weighted average common shares outstanding, basic and diluted	25,615,282	729,391
Net loss per share attributable to common stockholders, basic and diluted	($0.53)	($6.18)

Summary_of_Significant_Account6

Summary of Significant Accounting Policies - Summary of Common Stock Equivalents Outstanding (Detail)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from computation of earnings per share	2,593,637	1,513,353
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	2,589,767	1,513,353
Unvested Restricted Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from computation of earnings per share	3,870

Accrued_Expenses_Schedule_of_A

Accrued Expenses - Schedule of Accrued Expenses (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Payables and Accruals [Abstract]
Accrued payroll and related expenses	$543	$1,239
Accrued research and development expenses	2,828	1,180
Accrued professional fees	371	585
Accrued other	292	168
Accrued expenses	$4,034	$3,172

Notes_Payable_Schedule_of_Note

Notes Payable - Schedule of Notes Payable (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Equity Method Investments And Cost Method Investments [Abstract]
Notes payable	$7,500	$7,500
Less: current portion	-2,093	-1,381
Notes payable, net of current portion	5,407	6,119
Debt discount, net of accretion	-67	-79
Accretion related to final payment	181	137
Notes payable, net of discount, long term	$5,521	$6,177

Notes_Payable_Schedule_of_Esti

Notes Payable - Schedule of Estimated Future Principal Payments (Detail) (USD $)	Mar. 31, 2015
In Thousands, unless otherwise specified
Debt Instruments [Abstract]
2015	$1,381
2016	2,936
2017	3,183
Total	$7,500

Notes_Payable_Additional_Infor

Notes Payable - Additional Information (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Debt Instrument [Line Items]
Interest expense on credit facility	$213	$2
Credit Facility [Member]
Debt Instrument [Line Items]
Effective annual interest rate	14.00%

Stockholders_Equity_Additional

Stockholders' Equity - Additional Information (Detail) (USD $)	3 Months Ended		0 Months Ended	1 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Jan. 28, 2015	Jan. 31, 2015
Proceeds from offering, net of commissions and underwriting discounts	$129,571
Underwriting discounts, commissions and offering expenses		827
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				504,200
Proceeds from offering, net of commissions and underwriting discounts			129,571	129,571
Underwriting discounts, commissions and offering expenses			$473	$473

StockBased_Awards_Additional_I

Stock-Based Awards - Additional Information (Detail) (USD $)	3 Months Ended	0 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2015	Jan. 01, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock-based compensation cost	$26,317
Stock-based compensation recognized weighted average period	3 years 8 months 12 days
Nonemployee Service Based Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of outstanding unvested shares held by nonemployees	10,683
2014 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for grant	262,136
2014 Stock Option and Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for grant	1,970,599
Shares added to plan		915,166

StockBased_Awards_Summary_of_S

Stock-Based Awards - Summary of Stock-Based Compensation Expense Related to Stock Options and Restricted Common Stock (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$1,057	$176
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	404	69
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$653	$107

Commitments_and_Contingencies_1

Commitments and Contingencies - Additional Information (Detail) (USD $)	3 Months Ended		1 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2015
Commitment And Contingencies [Line Items]
Operating lease, rental expense	$58,000	$25,000
Subsequent Event [Member]
Commitment And Contingencies [Line Items]
Lease expiration date			31-Jul-17
Lease extension period			3 years
Subsequent Event [Member] | 2015 [Member]
Commitment And Contingencies [Line Items]
Increase in payments under operating lease			70,000
Subsequent Event [Member] | 2016 [Member]
Commitment And Contingencies [Line Items]
Increase in payments under operating lease			100,000
Subsequent Event [Member] | 2017 [Member]
Commitment And Contingencies [Line Items]
Increase in payments under operating lease			60,000
Pre Commercialization Milestones [Member]
Commitment And Contingencies [Line Items]
Milestone payments	12,250,000		12,250,000
Product Commercialization Milestones [Member]
Commitment And Contingencies [Line Items]
Milestone payments	12,500,000		12,500,000
Subsequent Licensed Product [Member]
Commitment And Contingencies [Line Items]
Licensing fees per product maximum	$1,250,000		1,250,000
Office Two [Member]
Commitment And Contingencies [Line Items]
Lease expiration date	31-Jul-17
Lease extension period	3 years

Commitments_and_Contingencies_2

Commitments and Contingencies - Schedule of Future Minimum Lease Payments for Operating Leases (Detail) (USD $)	Mar. 31, 2015
In Thousands, unless otherwise specified
Commitments and Contingencies Disclosure [Abstract]
2015	$172
2016	235
2017	139
Total	$546

Retirement_Plan_Additional_Inf

Retirement Plan - Additional Information (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Compensation and Retirement Disclosure [Abstract]
Percentage of employer's contribution on employee's base salary	2.00%
Contribution expense	$45	$13

Australia_Research_and_Develop1

Australia Research and Development Tax Incentive - Additional Information (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Operating Loss Carryforwards [Line Items]
Percentage of refundable tax incentive	45.00%
Reduction to research and development expenses	$229	$26
Unrealized foreign currency transaction gains (losses)	-24	42
Australia [Member]
Operating Loss Carryforwards [Line Items]
Percentage of reduction in research and development costs	45.00%
Tax incentive receivable	596		391
Capital Loss Carryforward [Member]
Operating Loss Carryforwards [Line Items]
Unrealized foreign currency transaction gains (losses)	($24)	$42