Statements of Operations and Comprehensive Loss (Unaudited) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Operating expenses:
Research and development expenses	$ 6,724,503	$ 6,507,972	$ 18,046,572	$ 12,574,455
General and administrative expenses	3,552,289	1,976,888	10,526,775	5,052,983
Total operating expenses	10,276,792	8,484,860	28,573,347	17,627,438
Loss from operations	(10,276,792)	(8,484,860)	(28,573,347)	(17,627,438)
Other income (expense):
Warrant remeasurement	0	(1,433,502)	0	(1,879,823)
Other expense	(163,463)	0	(163,463)	0
Interest income	56,082	1,333	148,272	2,810
Interest expense	(375,089)	(213,021)	(717,263)	(615,047)
Net loss	(10,759,262)	(10,130,050)	(29,305,801)	(20,119,498)
Comprehensive loss	(10,759,262)	(10,130,050)	(29,305,801)	(20,119,498)
Cumulative dividend on Series C , C-1 and C-2 convertible preferred stock	0	(1,827,568)	0	(4,257,083)
Net loss attributable to common stockholders	$ (10,759,262)	$ (11,957,618)	$ (29,305,801)	$ (24,376,581)
Loss per share attributable to common stockholders basic and diluted (in dollars per share)	$ (0.37)	$ (7.08)	$ (1.02)	$ (14.44)
Weighted average common shares outstanding basic and diluted (in shares)	28,896,941	1,688,475	28,848,842	1,688,475