Condensed Balance Sheets (USD $)	Jun. 30, 2014	Dec. 31, 2013
Current assets:
Cash and cash equivalents	$ 95,394,102	$ 21,215,228
Investments	28,851,842	11,341,241
Accounts receivable	113,953	135,339
Prepaid expenses and other current assets	1,691,312	739,235
Total current assets	126,051,209	33,431,043
Property and equipment, net	181,029	30,366
Deferred offering costs		1,078,138
Other assets	125,345	125,345
Total assets	126,357,583	34,664,892
Current liabilities:
Accounts payable	1,488,184	714,137
Accrued expenses	3,277,593	3,183,761
Current portion of capital lease obligation	3,939	3,912
Total current liabilities	4,769,716	3,901,810
Capital lease obligation, net of current portion	6,369	8,004
Other liabilities	29,532
Total liabilities	4,805,617	3,909,814
Redeemable convertible preferred stock; $0.00001 par value; 0 and 5,500,636 shares authorized at June 30, 2014 and December 31, 2013, respectively:
Redeemable convertible preferred stock		157,827,135
Stockholders' equity (deficit):
Common stock; $0.00001 par value; 175,000,000 and 14,700,000 authorized at June 30, 2014 and December 31, 2013, respectively; 20,262,978 and 1,383,345 shares issued and outstanding at June 30, 2014 and December 31, 2013, respectively	202	14
Additional paid-in capital	202,535,864
Treasury Stock, at cost, 775 shares	(21,362)
Accumulated other comprehensive loss	(8,216)
Accumulated deficit	(80,954,522)	(127,072,071)
Total stockholders' equity (deficit)	121,551,966	(127,072,057)
Total liabilities, redeemable convertible preferred stock and stockholders' equity (deficit)	126,357,583	34,664,892
Series A redeemable convertible preferred stock [Member]
Redeemable convertible preferred stock; $0.00001 par value; 0 and 5,500,636 shares authorized at June 30, 2014 and December 31, 2013, respectively:
Redeemable convertible preferred stock		39,367,094
Series B redeemable convertible preferred stock [Member]
Redeemable convertible preferred stock; $0.00001 par value; 0 and 5,500,636 shares authorized at June 30, 2014 and December 31, 2013, respectively:
Redeemable convertible preferred stock		21,257,044
Series C redeemable convertible preferred stock [Member]
Redeemable convertible preferred stock; $0.00001 par value; 0 and 5,500,636 shares authorized at June 30, 2014 and December 31, 2013, respectively:
Redeemable convertible preferred stock		$ 97,202,997