Condensed Statements of Operations and Comprehensive Loss (Unaudited) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Operating expenses:
Research and development expenses	$ 2,523,796	$ 8,975,304	$ 15,265,881	$ 16,564,800
General and administrative expenses	3,335,039	4,173,384	8,016,555	8,375,226
Restructuring expenses	6,646,242	0	6,646,242	0
Impairment charges	0	0	2,672,581	0
Total operating expenses	12,505,077	13,148,688	32,601,259	24,940,026
Loss from operations	(12,505,077)	(13,148,688)	(32,601,259)	(24,940,026)
Other income (expense):
Interest income	262,140	168,974	508,779	265,233
Interest expense	(434,695)	(524,768)	(1,425,255)	(999,909)
Net loss	$ (12,677,632)	$ (13,504,482)	$ (33,517,735)	$ (25,674,702)
Loss per share basic and diluted (in dollars per share)	$ (0.41)	$ (0.44)	$ (1.08)	$ (0.86)
Weighted average common shares outstanding basic and diluted (in shares)	31,298,429	30,403,419	31,133,070	29,704,898