Statements of Operations and Comprehensive Loss (Unaudited) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Operating expenses:
Research and development expenses	$ 5,975,306	$ 3,195,244	$ 11,322,069	$ 6,066,483
General and administrative expenses	3,288,889	1,765,065	6,974,486	3,076,095
Total operating expenses	9,264,195	4,960,309	18,296,555	9,142,578
Loss from operations	(9,264,195)	(4,960,309)	(18,296,555)	(9,142,578)
Other income (expense):
Warrant remeasurement	0	(350,129)	0	(446,321)
Interest income	49,376	1,338	92,190	1,477
Interest expense	(161,310)	(211,863)	(342,174)	(402,026)
Net loss	(9,376,129)	(5,520,963)	(18,546,539)	(9,989,448)
Comprehensive loss	(9,376,129)	(5,520,963)
Cumulative dividend on Series C , C-1 and C-2 convertible preferred stock	0	(1,746,334)	0	(2,429,515)
Net loss attributable to common stockholders	$ (9,376,129)	$ (7,267,297)	$ (18,546,539)	$ (12,418,963)
Loss per share attributable to common stockholders basic and diluted (in dollars per share)	$ (0.33)	$ (4.30)	$ (0.64)	$ (7.36)
Weighted average common shares outstanding basic and diluted (in shares)	28,828,449	1,688,475	28,820,678	1,688,475