Flexion Therapeutics (FLXN) 10-Q 14 Nov 14 2014 Q3 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	9 Months Ended
	Sep. 30, 2014	Nov. 07, 2014
Document And Entity Information [Abstract]	'	'
Document Type	'10-Q	'
Amendment Flag	'false	'
Document Period End Date	30-Sep-14	'
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus	'Q3	'
Trading Symbol	'FLXN	'
Entity Registrant Name	'Flexion Therapeutics Inc	'
Entity Central Index Key	'0001419600	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Smaller Reporting Company	'
Entity Common Stock, Shares Outstanding	'	15,627,288

Balance_Sheets_Unaudited

Balance Sheets (Unaudited) (USD $)	Sep. 30, 2014	Dec. 31, 2013
Current assets:	'	'
Cash and cash equivalents	$14,365,010	$16,188,254
Marketable securities	52,223,545	250,047
Prepaid expenses and other current assets	710,312	181,962
Total current assets	67,298,867	16,620,263
Property and equipment, net	681,866	375,239
Deferred offering costs	'	1,623,540
Other assets	16,501	28,875
Restricted cash	128,000	128,000
Total assets	68,125,234	18,775,917
Current liabilities:	'	'
Accounts payable	1,498,948	1,279,874
Accrued expenses and other current liabilities	2,696,380	2,256,680
Current portion of long-term debt	2,000,000	1,500,000
Total current liabilities	6,195,328	5,036,554
Long-term debt	2,081,667	3,546,667
Other long-term liabilities	56,804	90,373
Total liabilities	8,333,799	8,673,594
Commitments and contingencies	'	'
Preferred stock, value	0	0
Stockholders' equity (deficit):	'	'
Common stock, $0.001 par value; 100,000,000 and 94,000,000 shares authorized; 15,627,288 and 794,090 shares issued and outstanding, at September 30, 2014 and December 31, 2013, respectively	15,627	794
Additional paid-in capital	145,446,666	1,458,503
Accumulated other comprehensive income	754	-28
Accumulated deficit	-85,671,612	-66,163,159
Total stockholders' equity (deficit)	59,791,435	-64,703,890
Total liabilities, convertible preferred stock, and stockholders' equity (deficit)	68,125,234	18,775,917
Series A and B Convertible Preferred Stock [Member]	'	'
Current liabilities:	'	'
Preferred stock, value	'	$74,806,213

Balance_Sheets_Unaudited_Paren

Balance Sheets (Unaudited) (Parenthetical) (USD $)	Sep. 30, 2014	Dec. 31, 2013
Preferred stock, par value	$0.00	$0.00
Preferred stock, shares authorized	10,000,000	0
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$0.00	$0.00
Common stock, shares authorized	100,000,000	94,000,000
Common stock, shares issued	15,627,288	794,090
Common stock, shares outstanding	15,627,288	794,090
Series A and B Convertible Preferred Stock [Member]	'	'
Preferred stock, par value	$0.00	$0.00
Preferred stock, shares authorized	0	73,780,250
Preferred stock, shares issued	0	72,780,250
Preferred stock, shares outstanding	0	72,780,250
Preferred stock, aggregate liquidation preference	$0	$75,043,464

Statements_of_Operations_and_C

Statements of Operations and Comprehensive Loss (Unaudited) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Income Statement [Abstract]	'	'	'	'
Revenue	$0	$0	$0	$0
Operating expenses:	'	'	'	'
Research and development	4,658,293	2,569,931	12,423,733	8,824,622
General and administrative	2,304,026	2,420,267	6,822,171	5,363,291
Total operating expenses	6,962,319	4,990,198	19,245,904	14,187,913
Loss from operations	-6,962,319	-4,990,198	-19,245,904	-14,187,913
Other income (expense):	'	'	'	'
Interest income	153,122	38,777	318,524	218,762
Interest expense	-96,926	-113,889	-314,630	-335,000
Other income (expense), net	-129,484	-35,070	-266,443	-192,088
Total other income (expense)	-73,288	-110,182	-262,549	-308,326
Net loss	-7,035,607	-5,100,380	-19,508,453	-14,496,239
Net loss attributable to common stockholders	-7,035,607	-5,100,380	-19,508,453	-14,496,239
Net loss per share attributable to common stockholders, basic and diluted	($0.45)	($6.46)	($1.50)	($18.37)
Weighted average common shares outstanding, basic and diluted	15,624,963	789,222	13,007,892	789,222
Other comprehensive (loss) income:	'	'	'	'
Unrealized (losses) gains from available-for-sale securities, net of tax of $0	-2,468	315	782	-1,103
Total other comprehensive (loss) income	-2,468	315	782	-1,103
Comprehensive loss	($7,038,075)	($5,100,065)	($19,507,671)	($14,497,342)

Statements_of_Operations_and_C1

Statements of Operations and Comprehensive Loss (Unaudited) (Parenthetical) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Income Statement [Abstract]	'	'	'	'
Other comprehensive (loss) income, Tax	$0	$0	$0	$0

Statements_of_Changes_in_Conve

Statements of Changes in Convertible Preferred Stock and Stockholders' (Deficit) (Unaudited) (USD $)	Total	Series A and B Convertible Preferred Stock	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit [Member]
Balance (in shares) at Dec. 31, 2013	'	72,780,250	794,090	'	'	'
Balance at Dec. 31, 2013	($64,703,890)	$74,806,213	$794	$1,458,503	($28)	($66,163,159)
Conversion of Series A and Series B Convertible Preferred Stock	74,806,213	-74,806,213	8,952	74,797,261	'	'
Conversion of Series A and Series B Convertible Preferred Stock (in shares)	'	'	8,952,057	'	'	'
Conversion of Series A and Series B Convertible Preferred Stock (in shares)	'	-72,780,250	'	'	'	'
Issuance of Stock, net of issuance costs	67,162,004	'	5,750	67,156,254	'	'
Issuance of Stock, net of issuance costs (in shares)	'	'	5,750,000	'	'	'
Exercise of stock options	282,545	'	131	282,414	'	'
Exercise of stock options (in shares)	131,141	'	131,141	'	'	'
Stock-based compensation expense	1,752,234	'	'	1,752,234	'	'
Net loss	-19,508,453	'	'	'	'	-19,508,453
Other comprehensive loss	782	'	'	'	782	'
Balance (in shares) at Sep. 30, 2014	'	'	15,627,288	'	'	'
Balance at Sep. 30, 2014	$59,791,435	'	$15,627	$145,446,666	$754	($85,671,612)

Statements_of_Cash_Flows_Unaud

Statements of Cash Flows (Unaudited) (USD $)	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Cash flows from operating activities	'	'
Net loss	($19,508,453)	($14,496,239)
Adjustments to reconcile net loss to cash used in operating activities:	'	'
Depreciation	84,943	54,168
Stock-based compensation expense	1,752,234	773,023
Amortization of premium (discount) on marketable securities	226,834	144,832
Other non-cash charges	12,374	47,375
Changes in operating assets and liabilities:	'	'
Prepaid expenses and other current and long-term assets	-350,534	412,102
Accounts payable	296,331	341,131
Accrued expenses and other current and long-term liabilities	671,891	66,689
Net cash used in operating activities	-16,814,380	-12,656,919
Cash flows from investing activities	'	'
Purchases of property and equipment	-326,571	-385,823
Change in restricted cash	'	-98,000
Purchases of marketable securities	-72,359,552	-15,013,186
Redemption of marketable securities	20,160,000	23,885,000
Net cash (used in) provided by investing activities	-52,526,123	8,387,991
Cash flows from financing activities	'	'
Proceeds from borrowings under term loan	'	5,000,000
Payments of debt issuance costs	'	-40,715
Payment of initial public offering costs	-1,282,785	-54,347
Proceeds from the issuance of common stock	69,517,500	'
Proceeds from the exercise of stock options	282,545	'
Payments on debt	-1,000,001	'
Net cash provided by financing activities	67,517,259	4,904,938
Net increase (decrease) in cash and cash equivalents	-1,823,244	636,010
Cash and cash equivalents at beginning of period	16,188,254	12,835,330
Cash and cash equivalents at end of period	14,365,010	13,471,340
Supplemental disclosures of cash flow information:	'	'
Cash paid for interest	287,370	266,667
Supplemental disclosures of non-cash financing activities:	'	'
Conversion of convertible preferred stock into common stock	$74,806,213	'

Overview_and_Nature_of_the_Bus

Overview and Nature of the Business	9 Months Ended
	Sep. 30, 2014
Accounting Policies [Abstract]	'
Overview and Nature of the Business	'
	1	Overview and Nature of the Business
	Flexion Therapeutics, Inc. (“Flexion” or the “Company”) was incorporated under the laws of the state of Delaware on November 5, 2007. Flexion is a specialty pharmaceutical company focused on the development and commercialization of novel, injectable pain therapies. The Company is targeting anti-inflammatory and analgesic therapies for the treatment of patients with musculoskeletal conditions, beginning with osteoarthritis (“OA”), a type of degenerative arthritis and post-operative pain. Flexion’s broad and diversified portfolio of product candidates addresses the OA pain treatment spectrum, from moderate to severe pain, and provides the Company with multiple opportunities to achieve its goal of commercializing novel, patient-focused pain therapies.
	The Company is subject to risks and uncertainties common to early-stage companies in the biopharmaceutical industry, including, but not limited to, new technological innovations, dependence on key personnel, protection of proprietary technology, compliance with government regulations, and ability to secure additional capital to fund operations. The Company’s product candidates are all in the development stage and will require significant additional research and development efforts, including extensive preclinical 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. There can be no assurance that development efforts, including clinical trials, will be successful or that the Company will have the ability to continue into later stages of clinical trials. Even if the Company’s product development efforts are successful, it is uncertain when, if ever, the Company will realize significant revenue from product sales.
	On February 18, 2014, the Company completed an initial public offering (“IPO”) of its common stock, which resulted in the sale of 5,750,000 shares of common stock at a price to the public of $13.00 per share, including shares sold pursuant to the exercise in full of the underwriters’ option to purchase additional shares. The Company received net proceeds from the IPO of $67.2 million after deducting underwriting discounts, commissions, and offering costs paid by the Company. In preparation for the IPO, the Company’s Board of Directors and stockholders approved a 1-for-8.13 reverse stock split of the Company’s common stock and a proportional adjustment to the existing conversion ratios for each series of Convertible Preferred Stock, effective January 27, 2014. All share and per share amounts in the condensed financial statements and notes thereto have been retroactively adjusted, where necessary, to give effect to this reverse stock split. In connection with the closing of the IPO, all of the Company’s outstanding redeemable convertible preferred stock automatically converted to common stock as of February 18, 2014, resulting in an additional 8,952,057 shares of common stock of the Company becoming outstanding. Following these transactions, the Company’s total issued common stock as of September 30, 2014 was 15,627,288 shares. The significant increase in shares outstanding in February 2014 is expected to impact the year-over-year comparability of the Company’s (loss) earnings per share calculations in 2014.

Basis_of_Presentation

Basis of Presentation	9 Months Ended
	Sep. 30, 2014
Accounting Policies [Abstract]	'
Basis of Presentation	'
	2	Basis of Presentation
	The accompanying condensed financial statements as of September 30, 2014, and for the three and nine months ended September 30, 2014 and 2013, have been prepared in accordance with the rules and regulations of the Securities and Exchange Commission (the “SEC”) and Generally Accepted Accounting Principles (“GAAP”) for condensed financial information. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, these financial statements reflect all adjustments which are necessary for a fair statement of the Company’s financial position and results of its operations, as of and for the periods presented. These financial statements should be read in conjunction with the financial statements and notes thereto contained in the Company’s Annual Report on Form 10-K filed with the SEC on March 28, 2014.
	The information presented in the financial statements and related notes as of September 30, 2014, and for the three and nine months ended September 30, 2014 and 2013, is unaudited. The December 31, 2013 condensed balance sheet included herein was derived from the audited financial statements as of that date, but does not include all disclosures, including notes, required by GAAP for complete financial statements.
	Interim results for the three and nine months ended September 30, 2014 are not necessarily indicative of the results that may be expected for the fiscal year ending December 31, 2014, or any future period.
	The accompanying condensed financial statements have been prepared on a basis which assumes that the Company will continue as a going concern and which contemplates the realization of assets and satisfaction of liabilities and commitments in the normal course of business. The Company has incurred recurring losses and negative cash flows from operations. As of September 30, 2014 and December 31, 2013, the Company had cash, cash equivalents and marketable securities of $66,588,555 and $16,438,301, respectively. Management believes that current cash, cash equivalents and marketable securities on hand at September 30, 2014 should be sufficient to fund operations into late 2015. The future viability of the Company is dependent on its ability to raise additional capital to finance its operations and to fund increased research and development costs in order to seek approval for commercialization of its product candidates. The Company’s failure to raise capital as and when needed would have a negative impact on its financial condition and its ability to pursue its business strategies. This capital is necessary for the Company to perform the research and development activities required to develop the Company’s product candidates in order to generate future revenue streams.
	Use of Estimates
	GAAP requires the Company’s management to make estimates and judgments that may affect the reported amounts of assets, liabilities, revenues, expenses and related disclosures. The Company bases estimates and judgments on historical experience and on various other factors that it believes to be reasonable under the circumstances. The most significant estimates in these condensed financial statements include useful lives with respect to long-lived assets, accounting for stock-based compensation, and accrued expenses, including clinical research costs. The Company’s actual results may differ from these estimates under different assumptions or conditions. The Company evaluates its estimates on an ongoing basis. Changes in estimates are reflected in reported results in the period in which they become known by the Company’s management.
	Recent Accounting Pronouncements
	In June 2014, the Financial Accounting Standard Board, or FASB, issued amended accounting guidance for development stage entities. The amendment eliminates certain financial reporting requirements for development stage entities, specifically, the presentation of inception-to-date information, the development stage entity label on the financial statements, the description of the activities in which the entity is engaged, and disclosure in the first year that the entity is no longer a development stage entity that it had been in prior years. In addition, the amendment clarifies guidance regarding entities that have not commenced planned principal operations. The amendment is effective retrospectively for annual reporting periods beginning after December 15, 2014, and interim periods therein with early adoption permitted. The Company elected to early adopt this standard in the period ended June 30, 2014. Other than a change in presentation, the adoption of this guidance did not have an impact on the Company’s financial statements.
	In May 2014, the FASB issued guidance which supersedes all existing revenue recognition requirements, including most industry-specific guidance. The new standard requires a company to recognize revenue when it transfers goods or services to customers in an amount that reflects the consideration that the company expects to receive for those goods or services. This guidance will be effective prospectively for fiscal years, and interim periods within those years, beginning after December 15, 2016, and early adoption is not permitted. The Company is currently evaluating the potential impact that the adoption of this guidance and the related transition guidance may have on the Company’s financial statements.
	In August 2014, the FASB issued accounting guidance for the disclosure of uncertainties related to an entity’s ability to continue as a going concern. The new standard requires management to perform an assessment at interim and annual periods as to the entity’s ability to continue as a going concern and provides specific disclosure guidance. This guidance will be effective for fiscal years, and interim periods within those years, beginning after December 15, 2016 and early adoption is permitted. The Company is currently evaluating the potential impact that the adoption of this guidance may have on the Company’s financial statements.

Fair_Value_of_Financial_Assets

Fair Value of Financial Assets	9 Months Ended
	Sep. 30, 2014
Fair Value Disclosures [Abstract]	'
Fair Value of Financial Assets	'
	3	Fair Value of Financial Assets
	The following tables present information about the Company’s assets and liabilities that are measured at fair value on a recurring basis as of September 30, 2014 and December 31, 2013 and indicate the level of the fair value hierarchy utilized to determine such fair value:
			Fair Value Measurements as of September 30, 2014 Using:
			Level 1		Level 2		Level 3		Total
	Assets:
	Cash equivalents		$	—	$	13,443,515	$	—	$	13,443,515
	Marketable securities			—		52,223,545		—		52,223,545
			$	—	$	65,667,060	$	—	$	65,667,060
			Fair Value Measurements as of December 31, 2013 Using:
			Level 1		Level 2		Level 3		Total
	Assets:
	Cash equivalents		$	—	$	14,957,788	$	—	$	14,957,788
	Marketable securities			—		250,047		—		250,047
			$	—	$	15,207,835	$	—	$	15,207,835
	As of September 30, 2014 and December 31, 2013, the Company’s cash equivalents and marketable securities that are invested primarily in U.S. treasury bills, corporate bonds, money market funds, commercial paper and U.S. government agency holdings are valued based primarily on Level 2 inputs. The Company measures the fair value of marketable securities using Level 2 inputs and primarily relies on quoted prices in active markets for similar marketable securities. During the nine months ended September 30, 2014 and the year ended December 31, 2013, there were no transfers between Level 1, Level 2 and Level 3.
	As outlined in footnote ten, the Company has a term loan with MidCap Financial SBIC, LP (“MidCap”). The term loan outstanding under the Company’s credit and security agreement with MidCap is reported at its carrying value in the accompanying balance sheet. The Company determined the fair value of the term loan using an income approach, utilizing a discounted cash flow analysis based on current market interest rates for debt issuances with similar remaining years to maturity, adjusted for credit risk. The term loan was valued using Level 2 inputs as of September 30, 2014. The result of the calculation yielded a fair value that approximates carrying value.

Marketable_Securities

Marketable Securities	9 Months Ended
	Sep. 30, 2014
Investments, Debt and Equity Securities [Abstract]	'
Marketable Securities	'
	4	Marketable Securities
	As of September 30, 2014 and December 31, 2013, the fair value of available-for-sale marketable securities by type of security was as follows:
			September 30, 2014
			Amortized Cost		Gross Unrealized		Gross Unrealized			Fair Value
					Gains		Losses
	Commercial paper		$	8,994,407	$	5,223	$	—		$	8,999,630
	Corporate bonds and US Government Obligations		$	43,228,384	$	3,141	$	(7,610	)	$	43,223,915
			$	52,222,791	$	8,364	$	(7,610	)	$	52,223,545
			December 31, 2013
			Amortized Cost		Gross Unrealized		Gross Unrealized			Fair Value
					Gains		Losses
	Corporate bonds		$	250,075	$	—	$	(28	)	$	250,047
			$	250,075	$	—	$	(28	)	$	250,047
	At September 30, 2014 and December 31, 2013, marketable securities consisted of investments that mature within one year.

Property_and_Equipment_Net

Property and Equipment, Net	9 Months Ended
	Sep. 30, 2014
Property, Plant and Equipment [Abstract]	'
Property and Equipment, Net	'
	5	Property and Equipment, Net
	Property and equipment, net, as of September 30, 2014 and December 31, 2013 consisted of the following:
			September 30,			December 31,
			2014			2013
	Computer and office equipment		$	314,718		$	257,346
	Manufacturing equipment			153,140			99,684
	Furniture and fixtures			181,578			149,183
	Leasehold improvements			130,626			130,626
	Construction in Progress			248,346			—
				1,028,408			636,839
	Less: Accumulated depreciation			(346,542	)		(261,600	)
	Total property and equipment, net		$	681,866		$	375,239
	Depreciation expense for the nine months ended September 30, 2014 and the year ended December 31, 2013, was $84,943 and $79,808, respectively. During the nine months ended September 30, 2014 and the year ended December 31, 2013, $0 and $16,695 of property and equipment was disposed of, resulting in a loss of $0 and $14,111, respectively.

Accrued_Expenses_and_Other_Cur

Accrued Expenses and Other Current Liabilities	9 Months Ended
	Sep. 30, 2014
Payables and Accruals [Abstract]	'
Accrued Expenses and Other Current Liabilities	'
	6	Accrued Expenses and Other Current Liabilities
	Accrued expenses and other current liabilities consisted of the following:
			September 30,		December 31,
			2014		2013
	Clinical research		$	822,215	$	163,521
	Contract manufacturing services			485,000		529,287
	Payroll and other employee-related expenses			800,851		792,165
	Professional services fees			441,599		642,052
	Interest expense			26,667		34,445
	Other			120,048		95,210
	Total accrued expenses and other current liabilities		$	2,696,380	$	2,256,680

StockBased_Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 30, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
Stock-Based Compensation	'
	7	Stock-Based Compensation
	Stock Incentive Plan
	The Company grants stock-based awards pursuant to its 2013 Equity Incentive Plan (the “2013 Plan”). The maximum number of shares that may be issued under the 2013 Plan is 2,337,616, which is the sum of (i) 1,230,012 shares, plus (ii) the number of shares remaining available for grant under our previous stock incentive plan at the time the 2013 Plan became effective, plus (iii) any shares subject to outstanding stock options or other stock awards that would have otherwise returned to our previous stock incentive plan (such as upon the expiration or termination of a stock award prior to vesting), as such shares become available from time to time. The maximum number of shares that may be issued upon the exercise of incentive stock options (“ISOs”) under the 2013 Plan is 4,684,989. As of September 30, 2014, 967,502 shares were available for future issuance under the 2013 Plan.
	Stock Options
	During the nine months ended September 30, 2014 and 2013, the Company granted stock options for the purchase of 663,150 and 201,722 shares of common stock, respectively, to certain employees and directors. The vesting conditions for all of these awards are time-based, and the awards typically vest 25% after one year and monthly thereafter for the next 36 months, except for annual option grants to non-employee directors of the Company whose initial grants vest 25% after one year and monthly thereafter for the next 24 months and whose annual grants vest in equal monthly installments during the 12-month period following the grant date, pursuant to the Company’s Non-Employee Director Compensation Policy. Awards typically expire after 10 years.
	Stock Option Valuation
	The fair value of each stock option grant is estimated on the date of grant using the Black-Scholes option-pricing model. Prior to the IPO, the Company was a private company and therefore lacked company-specific historical and implied volatility information. Therefore, it estimates its expected stock volatility based on the historical volatility of its publicly-traded peer companies and expects to continue to do so until such time as it has adequate historical data regarding the volatility of its own traded stock price. The expected term of the Company’s stock options has been determined utilizing the “simplified” method for awards that qualify as “plain vanilla” options. The expected term of stock options granted to non-employees is equal to the contractual term of the option award. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. Expected dividend yield is based on the fact that the Company has never paid cash dividends and does not expect to pay any cash dividends in the foreseeable future. The relevant data used to determine the value of the stock option grants for the nine months ended September 30, 2014 and 2013 are as follows:
			2014		2013
	Risk-free interest rates		1.54-2.04%		1.00%
	Expected dividend yield		0.00%		0.00%
	Expected term (in years)		6		6
	Expected volatility		61.87-66.98%		71.19%
	The following table summarizes stock option activity for the nine months ended September 30, 2014:
			Shares			Weighted
			Issuable			Average
			Under			Exercise
			Options			Price
	Outstanding as of December 31, 2013			834,983		$	2.99
	Granted			663,150			16.66
	Exercised			(131,141	)		2.15
	Canceled			(128,019	)		8.81
	Outstanding as of September 30, 2014			1,238,973		$	9.78
	Options vested and expected to vest at September 30, 2014			1,057,498
	Options exercisable at September 30, 2014			420,974
	The aggregate intrinsic value of options is calculated as the difference between the exercise price of the options and the fair value of the Company’s common stock for those options that had exercise prices lower than the fair value of the Company’s common stock. A total of 131,141 options were exercised during the nine months ended September 30, 2014. The aggregate intrinsic value of stock options exercised during the nine months ended September 30, 2014 was $1,364,080.
	At September 30, 2014 and 2013 the Company had options for the purchase of 1,238,973 and 839,852 shares of common stock outstanding, respectively, with a weighted average remaining contractual term of 8.3 and 8.2 years, respectively, and with a weighted average exercise price of $9.78 and $2.99 per share, respectively.
	The weighted average grant date fair value of options granted during the nine months ended September 30, 2014 and 2013 was $10.15 and $4.88, respectively.
	Stock-based Compensation
	The Company recorded stock-based compensation expense related to stock options for the three and nine months ended September 30, 2014 and 2013 as follows:
			For the three months ended					For the nine months ended
			September 30,					September 30,
			2014			2013		2014		2013
	Research and development		$	170,668		$	232,681	$	466,465	$	274,131
	General and administrative			504,141			444,107		1,285,769		498,892
			$	674,809		$	676,788	$	1,752,234	$	773,023
	As of September 30, 2014, unrecognized stock-based compensation expense for stock options outstanding was $7,822,984 which is expected to be recognized over a weighted average period of 3.0 years. As of September 30, 2013, unrecognized stock-based compensation expense for stock options outstanding was $2,530,427, which is expected to be recognized over a weighted average period of 3.0 years.
	On March 31, 2014 the vesting of certain options granted to a terminated employee was accelerated. This change in vesting conditions was accounted for as a modification of these stock options and resulted in an aggregate increase in the fair value of the options of $70,494 and was recorded as stock-based compensation expense on the modification date, which was March 31, 2014.

Net_Loss_Per_Share

Net Loss Per Share	9 Months Ended
	Sep. 30, 2014
Earnings Per Share [Abstract]	'
Net Loss Per Share	'
	8	Net Loss Per Share
	Basic and diluted net loss per share attributable to common stockholders was calculated as follows for the three and nine months ended September 30, 2014 and 2013:
			For the three months ended						For the nine months ended
			September 30,						September 30,
			2014			2013			2014			2013
	Numerator:
	Net loss		$	(7,035,607	)	$	(5,100,380	)	$	(19,508,453	)	$	(14,496,239	)
	Net income attributable to participating securities			—			—			—			—
	Net loss attributable to common stockholders:		$	(7,035,607	)	$	(5,100,380	)	$	(19,508,453	)	$	(14,496,239	)
	Denominator:
	Weighted average common shares outstanding, basic and diluted			15,624,963			789,222			13,007,892			789,222
	Net loss per share attributable to common stockholders, basic and diluted		$	(0.45	)	$	(6.46	)	$	(1.50	)	$	(18.37	)
	Stock options for the purchase of 1,234,199 and 809,216 weighted average shares of common stock were excluded from the computation of diluted net loss per share attributable to common stockholders for the three months ended September 30, 2014 and 2013, respectively, and 1,130,000 and 584,970 weighted average shares of common stock were excluded from the computation of diluted net loss per share attributable to common stockholders for the nine months ended September 30, 2014 and 2013, respectively. These options were excluded from the computations because they had an anti-dilutive impact to diluted net loss attributable to common stockholders incurred for those periods.
	In February 2014, the Company issued an additional 5,750,000 shares of common stock in connection with its IPO and 8,952,057 shares of common stock in connection with the automatic conversion of its redeemable convertible preferred stock upon the closing of the IPO. The issuance of these shares resulted in a significant increase in the Company’s weighted average shares outstanding for the three and nine months ended September 30, 2014 when compared to the comparable prior year period and is expected to continue to impact the year-over-year comparability of the Company’s (loss) earnings per share calculations in 2014.

Related_Party_Transactions

Related Party Transactions	9 Months Ended
	Sep. 30, 2014
Related Party Transactions [Abstract]	'
Related Party Transactions	'
	9	Related Party Transactions
	The Company has retained, as external legal counsel, a firm that owns 3,075 shares of common stock of the Company. Legal fees of the firm incurred by the Company for the nine months ended September 30, 2014 and 2013 were $792,490 and $1,315,364 respectively. Legal fees of the firm paid by the Company during the nine months ended September 30, 2014 and 2013 were $995,262 and $310,792, respectively. Amounts payable to this firm as of September 30, 2014 and 2013 were $224,297 and $1,190,842, respectively.

Longterm_Debt

Long-term Debt	9 Months Ended
	Sep. 30, 2014
Debt Disclosure [Abstract]	'
Long-term Debt	'
	10	Long-term Debt
	On January 3, 2013, the Company entered into a credit and security agreement with MidCap Financial SBIC, LP (“MidCap”) under which it immediately borrowed $5,000,000 as a term loan. The term loan accrues interest monthly at an interest rate of 8.0% per annum and has a term of 45 months. As the term loan has a 15-month interest-only period, the term loan principal balance, along with any accrued interest, is to be paid in 30 equal monthly installments beginning April 1, 2014 and ending September 1, 2016. In addition to these principal payments, the Company is required to make a payment of $175,000 to the lender on September 1, 2016, which amount is being accreted to the carrying value of the debt using the effective interest rate method. As of September 30, 2014, the carrying value of the term loan was $4,082,000 of which $2,000,000 was classified as the current portion of long-term debt on the balance sheet. In connection with the credit and security agreement, the Company granted MidCap a security interest in all of the Company’s personal property now owned or hereafter acquired, excluding intellectual property but including the proceeds from the sale, if any, of intellectual property, and a negative pledge on intellectual property. The credit and security agreement also contains certain representations, warranties, and non-financial covenants of the Company. As of September 30, 2014, the Company was compliant with all covenants.

Income_Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2014
Income Tax Disclosure [Abstract]	'
Income Taxes	'
	11	Income Taxes
	Section 382 of the Internal Revenue Code of 1986, as amended (“Section 382”), contains rules that limit the ability of a company that undergoes an ownership change to utilize its net operating losses (“NOLs”) and tax credits existing as of the date of such ownership change. Under the rules, such an ownership change is generally any change in ownership of more than 50% of a company’s stock within a rolling three-year period. The rules generally operate by focusing on changes in ownership among stockholders considered by the rules as owning, directly or indirectly, 5% or more of the stock of a company and any change in ownership arising from new issuances of stock by the company. During the quarter ended June 30, 2014, the Company completed a Section 382 study through February 11, 2014. The results of this study showed that as of February 11, 2014, one historical ownership change within the meaning of Section 382 had occurred in 2009. As a result of this Section 382 limitation, approximately $0.3 million of NOLs will expire unutilized. Subsequent ownership changes as defined by Section 382 may potentially limit the amount of net operating loss carryforwards that could be utilized annually to offset future taxable income.
	The Company has generated losses since inception and therefore has recorded no income tax benefits for those losses due to its uncertainty of realizing a benefit from those losses.

Subsequent_Events

Subsequent Events	9 Months Ended
	Sep. 30, 2014
Subsequent Events [Abstract]	'
Subsequent Events	'
	12	Subsequent Events
	There were no subsequent events that require disclosure in the financial statements for the period ended September 30, 2014.

Basis_of_Presentation_Policies

Basis of Presentation (Policies)	9 Months Ended
	Sep. 30, 2014
Accounting Policies [Abstract]	'
Use of Estimates	'
	Use of Estimates
	GAAP requires the Company’s management to make estimates and judgments that may affect the reported amounts of assets, liabilities, revenues, expenses and related disclosures. The Company bases estimates and judgments on historical experience and on various other factors that it believes to be reasonable under the circumstances. The most significant estimates in these condensed financial statements include useful lives with respect to long-lived assets, accounting for stock-based compensation, and accrued expenses, including clinical research costs. The Company’s actual results may differ from these estimates under different assumptions or conditions. The Company evaluates its estimates on an ongoing basis. Changes in estimates are reflected in reported results in the period in which they become known by the Company’s management.
Recent Accounting Pronouncements	'
	Recent Accounting Pronouncements
	In June 2014, the Financial Accounting Standard Board, or FASB, issued amended accounting guidance for development stage entities. The amendment eliminates certain financial reporting requirements for development stage entities, specifically, the presentation of inception-to-date information, the development stage entity label on the financial statements, the description of the activities in which the entity is engaged, and disclosure in the first year that the entity is no longer a development stage entity that it had been in prior years. In addition, the amendment clarifies guidance regarding entities that have not commenced planned principal operations. The amendment is effective retrospectively for annual reporting periods beginning after December 15, 2014, and interim periods therein with early adoption permitted. The Company elected to early adopt this standard in the period ended June 30, 2014. Other than a change in presentation, the adoption of this guidance did not have an impact on the Company’s financial statements.
	In May 2014, the FASB issued guidance which supersedes all existing revenue recognition requirements, including most industry-specific guidance. The new standard requires a company to recognize revenue when it transfers goods or services to customers in an amount that reflects the consideration that the company expects to receive for those goods or services. This guidance will be effective prospectively for fiscal years, and interim periods within those years, beginning after December 15, 2016, and early adoption is not permitted. The Company is currently evaluating the potential impact that the adoption of this guidance and the related transition guidance may have on the Company’s financial statements.
	In August 2014, the FASB issued accounting guidance for the disclosure of uncertainties related to an entity’s ability to continue as a going concern. The new standard requires management to perform an assessment at interim and annual periods as to the entity’s ability to continue as a going concern and provides specific disclosure guidance. This guidance will be effective for fiscal years, and interim periods within those years, beginning after December 15, 2016 and early adoption is permitted. The Company is currently evaluating the potential impact that the adoption of this guidance may have on the Company’s financial statements.

Fair_Value_of_Financial_Assets1

Fair Value of Financial Assets (Tables)	9 Months Ended
	Sep. 30, 2014
Fair Value Disclosures [Abstract]	'
Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis	'
	The following tables present information about the Company’s assets and liabilities that are measured at fair value on a recurring basis as of September 30, 2014 and December 31, 2013 and indicate the level of the fair value hierarchy utilized to determine such fair value:
		Fair Value Measurements as of September 30, 2014 Using:
		Level 1		Level 2		Level 3		Total
	Assets:
	Cash equivalents	$	—	$	13,443,515	$	—	$	13,443,515
	Marketable securities		—		52,223,545		—		52,223,545
		$	—	$	65,667,060	$	—	$	65,667,060
		Fair Value Measurements as of December 31, 2013 Using:
		Level 1		Level 2		Level 3		Total
	Assets:
	Cash equivalents	$	—	$	14,957,788	$	—	$	14,957,788
	Marketable securities		—		250,047		—		250,047
		$	—	$	15,207,835	$	—	$	15,207,835

Marketable_Securities_Tables

Marketable Securities (Tables)	9 Months Ended
	Sep. 30, 2014
Investments, Debt and Equity Securities [Abstract]	'
Summary of Fair Value of Available-for-Sale Marketable Securities by Type of Security	'
	As of September 30, 2014 and December 31, 2013, the fair value of available-for-sale marketable securities by type of security was as follows:
		September 30, 2014
		Amortized Cost		Gross Unrealized		Gross Unrealized			Fair Value
				Gains		Losses
	Commercial paper	$	8,994,407	$	5,223	$	—		$	8,999,630
	Corporate bonds and US Government Obligations	$	43,228,384	$	3,141	$	(7,610	)	$	43,223,915
		$	52,222,791	$	8,364	$	(7,610	)	$	52,223,545
		December 31, 2013
		Amortized Cost		Gross Unrealized		Gross Unrealized			Fair Value
				Gains		Losses
	Corporate bonds	$	250,075	$	—	$	(28	)	$	250,047
		$	250,075	$	—	$	(28	)	$	250,047

Property_and_Equipment_Net_Tab

Property and Equipment, Net (Tables)	9 Months Ended
	Sep. 30, 2014
Property, Plant and Equipment [Abstract]	'
Components of Property and Equipment, Net	'
	Property and equipment, net, as of September 30, 2014 and December 31, 2013 consisted of the following:
		September 30,			December 31,
		2014			2013
	Computer and office equipment	$	314,718		$	257,346
	Manufacturing equipment		153,140			99,684
	Furniture and fixtures		181,578			149,183
	Leasehold improvements		130,626			130,626
	Construction in Progress		248,346			—
			1,028,408			636,839
	Less: Accumulated depreciation		(346,542	)		(261,600	)
	Total property and equipment, net	$	681,866		$	375,239

Accrued_Expenses_and_Other_Cur1

Accrued Expenses and Other Current Liabilities (Tables)	9 Months Ended
	Sep. 30, 2014
Payables and Accruals [Abstract]	'
Schedule of Accrued Expenses and Other Current Liabilities	'
	Accrued expenses and other current liabilities consisted of the following:
		September 30,		December 31,
		2014		2013
	Clinical research	$	822,215	$	163,521
	Contract manufacturing services		485,000		529,287
	Payroll and other employee-related expenses		800,851		792,165
	Professional services fees		441,599		642,052
	Interest expense		26,667		34,445
	Other		120,048		95,210
	Total accrued expenses and other current liabilities	$	2,696,380	$	2,256,680

StockBased_Compensation_Tables

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
Schedule of Relevant Data Used to Estimate Fair Value of Stock Option Grants	'
	The relevant data used to determine the value of the stock option grants for the nine months ended September 30, 2014 and 2013 are as follows:
		2014		2013
	Risk-free interest rates	1.54-2.04%		1.00%
	Expected dividend yield	0.00%		0.00%
	Expected term (in years)	6		6
	Expected volatility	61.87-66.98%		71.19%
Summary of Stock Option Activity	'
	The following table summarizes stock option activity for the nine months ended September 30, 2014:
		Shares			Weighted
		Issuable			Average
		Under			Exercise
		Options			Price
	Outstanding as of December 31, 2013		834,983		$	2.99
	Granted		663,150			16.66
	Exercised		(131,141	)		2.15
	Canceled		(128,019	)		8.81
	Outstanding as of September 30, 2014		1,238,973		$	9.78
	Options vested and expected to vest at September 30, 2014		1,057,498
	Options exercisable at September 30, 2014		420,974
Stock-Based Compensation Expense Related to Stock Options	'
	The Company recorded stock-based compensation expense related to stock options for the three and nine months ended September 30, 2014 and 2013 as follows:
		For the three months ended					For the nine months ended
		September 30,					September 30,
		2014			2013		2014		2013
	Research and development	$	170,668		$	232,681	$	466,465	$	274,131
	General and administrative		504,141			444,107		1,285,769		498,892
		$	674,809		$	676,788	$	1,752,234	$	773,023

Net_Loss_Per_Share_Tables

Net Loss Per Share (Tables)	9 Months Ended
	Sep. 30, 2014
Earnings Per Share [Abstract]	'
Schedule of Basic and Diluted Net Loss per Share Attributable to Common Stockholders	'
	Basic and diluted net loss per share attributable to common stockholders was calculated as follows for the three and nine months ended September 30, 2014 and 2013:
		For the three months ended						For the nine months ended
		September 30,						September 30,
		2014			2013			2014			2013
	Numerator:
	Net loss	$	(7,035,607	)	$	(5,100,380	)	$	(19,508,453	)	$	(14,496,239	)
	Net income attributable to participating securities		—			—			—			—
	Net loss attributable to common stockholders:	$	(7,035,607	)	$	(5,100,380	)	$	(19,508,453	)	$	(14,496,239	)
	Denominator:
	Weighted average common shares outstanding, basic and diluted		15,624,963			789,222			13,007,892			789,222
	Net loss per share attributable to common stockholders, basic and diluted	$	(0.45	)	$	(6.46	)	$	(1.50	)	$	(18.37	)

Overview_and_Nature_of_the_Bus1

Overview and Nature of the Business - Additional Information (Detail) (USD $)	0 Months Ended	9 Months Ended
In Millions, except Share data, unless otherwise specified	Feb. 18, 2014	Sep. 30, 2014	Dec. 31, 2013
Organization And Nature Of Business [Line Items]	'	'	'
Incorporation date	'	5-Nov-07	'
Net proceeds from initial public offering	$67.20	'	'
Reverse stock split conversion ratio	'	'1-for-8.13 reverse stock split	'
Common stock, shares outstanding	'	15,627,288	794,090
Redeemable Convertible Preferred Stock [Member]	'	'	'
Organization And Nature Of Business [Line Items]	'	'	'
Number of shares issued upon the conversion of preferred stock to common stock	8,952,057	'	'
IPO [Member]	'	'	'
Organization And Nature Of Business [Line Items]	'	'	'
Sale of common stock, shares	5,750,000	'	'

Basis_of_Presentation_Addition

Basis of Presentation - Additional Information (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013
Accounting Policies [Abstract]	'	'
Cash, cash equivalents and marketable securities	$66,588,555	$16,438,301

Fair_Value_of_Financial_Assets2

Fair Value of Financial Assets - Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Marketable securities	$52,223,545	$250,047
Fair Value Measurements, Recurring [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash equivalents	13,443,515	14,957,788
Marketable securities	52,223,545	250,047
Assets, Total	65,667,060	15,207,835
Level 2 [Member] | Fair Value Measurements, Recurring [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Cash equivalents	13,443,515	14,957,788
Marketable securities	52,223,545	250,047
Assets, Total	$65,667,060	$15,207,835

Fair_Value_of_Financial_Assets3

Fair Value of Financial Assets - Additional Information (Detail) (USD $)	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Fair Value Disclosures [Abstract]	'	'
Transfers between Level 1, Level 2 and Level 3	$0	$0

Marketable_Securities_Summary_

Marketable Securities - Summary of Fair Value of Available-for-Sale Marketable Securities by Type of Security (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	$52,222,791	$250,075
Gross Unrealized Gains	8,364	'
Gross Unrealized Losses	-7,610	-28
Fair Value	52,223,545	250,047
Commercial Paper [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	8,994,407	'
Gross Unrealized Gains	5,223	'
Fair Value	8,999,630	'
Corporate Bonds and US Government Obligations [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	43,228,384	'
Gross Unrealized Gains	3,141	'
Gross Unrealized Losses	-7,610	'
Fair Value	43,223,915	'
Corporate Bonds [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	'	250,075
Gross Unrealized Gains	'	'
Gross Unrealized Losses	'	-28
Fair Value	'	$250,047

Marketable_Securities_Addition

Marketable Securities - Additional Information (Detail)	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Investments, Debt and Equity Securities [Abstract]	'	'
Maturity period of investment	'1 year	'1 year

Property_and_Equipment_Net_Com

Property and Equipment, Net - Components of Property and Equipment, Net (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013
Property, Plant and Equipment [Line Items]	'	'
Property and equipment gross	$1,028,408	$636,839
Less: Accumulated depreciation	-346,542	-261,600
Total property and equipment, net	681,866	375,239
Computer and Office Equipment [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Property and equipment gross	314,718	257,346
Manufacturing Equipment [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Property and equipment gross	153,140	99,684
Furniture and Fixtures [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Property and equipment gross	181,578	149,183
Leasehold Improvements [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Property and equipment gross	130,626	130,626
Construction in Progress [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Property and equipment gross	$248,346	'

Property_and_Equipment_Net_Add

Property and Equipment, Net - Additional Information (Detail) (USD $)	9 Months Ended		12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Property, Plant and Equipment [Abstract]	'	'	'
Depreciation	$84,943	$54,168	$79,808
Property and equipment disposals	0	'	16,695
Gain (Loss) on sale of property and equipment	$0	'	$14,111

Accrued_Expenses_and_Other_Cur2

Accrued Expenses and Other Current Liabilities - Schedule of Accrued Expenses and Other Current Liabilities (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013
Payables and Accruals [Abstract]	'	'
Clinical research	$822,215	$163,521
Contract manufacturing services	485,000	529,287
Payroll and other employee-related expenses	800,851	792,165
Professional services fees	441,599	642,052
Interest expense	26,667	34,445
Other	120,048	95,210
Total accrued expenses and other current liabilities	$2,696,380	$2,256,680

StockBased_Compensation_Additi

Stock-Based Compensation - Additional Information (Detail) (USD $)	0 Months Ended	9 Months Ended
	Mar. 31, 2014	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Stock options granted	'	663,150	'	'
Number of options exercised	'	131,141	'	'
Aggregate intrinsic value of stock options exercised	'	$1,364,080	'	'
Options to purchase common stock, outstanding	'	1,238,973	839,852	834,983
Weighted average remaining contractual term	'	'8 years 3 months 18 days	'8 years 2 months 12 days	'
Weighted average exercise price	'	$9.78	$2.99	$2.99
Weighted average grant date fair value of options granted	'	$10.15	$4.88	'
Unrecognized stock-based compensation expense	'	7,822,984	2,530,427	'
Stock options recognized over weighted average period	'	'3 years	'3 years	'
Aggregate increase in the fair value of the options	$70,494	'	'	'
Stock-based compensation, modification date	31-Mar-14	'	'	'
Employee Stock Option [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Stock options granted	'	663,150	201,722	'
Percentage of share based award, vested	'	25.00%	'	'
Awards vesting right	'	'The vesting conditions for all of these awards are time-based, and the awards typically vest 25% after one year and monthly thereafter for the next 36 months	'	'
Share based award, expiration period	'	'10 years	'	'
Employee Stock Option [Member] | Non Employee Directors [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Awards vesting right	'	'Annual option grants to non-employee directors of the Company whose initial grants vest 25% after one year and monthly thereafter for the next 24 months	'	'
2013 Plan [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Number of shares available for future issuance	'	967,502	'	'
Share based compensation, shares issued in period	'	1,230,012	'	'
Maximum [Member] | 2013 Plan [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Share based compensation, authorized	'	2,337,616	'	'
Maximum [Member] | 2013 Plan [Member] | Incentive Stock Options [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Number of options exercised	'	4,684,989	'	'

StockBased_Compensation_Schedu

Stock-Based Compensation - Schedule of Relevant Data Used to Estimate Fair Value of Stock Option Grants (Detail)	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'	'
Risk-free interest rates	'	1.00%
Risk-free interest rates, minimum	1.54%	'
Risk-free interest rates, maximum	2.04%	'
Expected dividend yield	0.00%	0.00%
Expected term (in years)	'6 years	'6 years
Expected volatility	'	71.19%
Expected volatility, minimum	61.87%	'
Expected volatility, maximum	66.98%	'

StockBased_Compensation_Summar

Stock-Based Compensation - Summary of Stock Option Activity (Detail) (USD $)	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'	'
Shares Issuable Under Options, Beginning balance	834,983	839,852
Shares Issuable Under Options, Granted	663,150	'
Shares Issuable Under Options, Exercised	-131,141	'
Shares Issuable Under Options, Canceled	-128,019	'
Shares Issuable Under Options, Ending balance	1,238,973	839,852
Shares Issuable Under Options, Options vested and expected to vest at September 30, 2014	1,057,498	'
Shares Issuable Under Options, Options exercisable at September 30, 2014	420,974	'
Weighted Average Exercise Price, Beginning balance	$2.99	$2.99
Weighted Average Exercise Price, Granted	$16.66	'
Weighted Average Exercise Price, Exercised	$2.15	'
Weighted Average Exercise Price, Canceled	$8.81	'
Weighted Average Exercise Price, Ending balance	$9.78	$2.99
Weighted Average Exercise Price, Options vested and expected to vest at September 30, 2014	'	'
Weighted Average Exercise Price, Options exercisable at September 30, 2014	'	'

StockBased_Compensation_StockB

Stock-Based Compensation - Stock-Based Compensation Expense Related to Stock Options (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Stock-based compensation expense	$674,809	$676,788	$1,752,234	$773,023
Research and Development [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Stock-based compensation expense	170,668	232,681	466,465	274,131
General and Administrative [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Stock-based compensation expense	$504,141	$444,107	$1,285,769	$498,892

Net_Loss_Per_Share_Schedule_of

Net Loss Per Share - Schedule of Basic and Diluted Net Loss per Share Attributable to Common Stockholders (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Numerator:	'	'	'	'
Net loss	($7,035,607)	($5,100,380)	($19,508,453)	($14,496,239)
Net income attributable to participating securities	'	'	'	'
Net loss attributable to common stockholders	($7,035,607)	($5,100,380)	($19,508,453)	($14,496,239)
Denominator:	'	'	'	'
Weighted average common shares outstanding, basic and diluted	15,624,963	789,222	13,007,892	789,222
Net loss per share attributable to common stockholders, basic and diluted	($0.45)	($6.46)	($1.50)	($18.37)

Net_Loss_Per_Share_Additional_

Net Loss Per Share - Additional Information (Detail)	Feb. 18, 2014	Feb. 18, 2014	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
	Redeemable Convertible Preferred Stock [Member]	IPO [Member]	Stock Options [Member]	Stock Options [Member]	Stock Options [Member]	Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'	'	'	'
Anti-dilutive securities excluded from the computation of diluted net loss per share attributable to common stockholders	'	'	1,234,199	809,216	1,130,000	584,970
Additional shares issued under Initial Public Offering	'	5,750,000	'	'	'	'
Common stock issued upon conversion of redeemable preferred stock	8,952,057	'	'	'	'	'

Related_Party_Transactions_Add

Related Party Transactions - Additional Information (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2014	Sep. 30, 2013
			Legal Fees [Member]	Legal Fees [Member]
Related Party Transaction [Line Items]	'	'	'	'
Expenses incurred	'	'	$792,490	$1,315,364
Expenses paid	'	'	995,262	310,792
Amounts payable	'	'	$224,297	$1,190,842
Common stock, shares	15,627,288	794,090	3,075	'

LongTerm_Debt_Additional_Infor

Long-Term Debt - Additional Information (Detail) (USD $)	9 Months Ended
	Sep. 30, 2014	Dec. 31, 2013	Jan. 03, 2013
Debt Disclosure [Abstract]	'	'	'
Term loan, borrowings	'	'	$5,000,000
Interest on term loan	'	'	8.00%
Term loan, maturity period	'45 months	'	'
Term loan, payment description	'15-month interest-only period, the term loan principal balance, along with any accrued interest, is to be paid in 30 equal monthly installments	'	'
Term loan, first periodic payment date	1-Apr-14	'	'
Term loan, last periodic payment date	1-Sep-16	'	'
Additional principal payments made to lender	175,000	'	'
Carrying value of term loan	4,082,000	'	'
Current portion of long-term debt	$2,000,000	$1,500,000	'

Income_Taxes_Additional_Inform

Income Taxes - Additional Information (Detail) (USD $)	9 Months Ended
	Sep. 30, 2014
Income Tax Disclosure [Abstract]	'
Limit of utilization of net operating losses (NOLs) and tax credits description	'Under the rules, such an ownership change is generally any change in ownership of more than 50% of a company's stock within a rolling three-year period. The rules generally operate by focusing on changes in ownership among stockholders considered by the rules as owning, directly or indirectly, 5% or more of the stock of a company and any change in ownership arising from new issuances of stock by the company
Net operating losses (NOLs) expire unutilized	$300,000
Income Tax Benefits	$0