Statements of Operations and Comprehensive Loss - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Operating expenses:
Research and development expenses	$ 16,068,769	$ 34,311,650
General and administrative expenses	14,291,008	17,654,970
Restructuring expenses	9,914,209	0
Impairment charges	2,822,581	0
Total operating expenses	43,096,567	51,966,620
Loss from operations	(43,096,567)	(51,966,620)
Other income (expense):
Interest income	871,879	700,903
Interest expense	(1,425,255)	(2,180,143)
Loss before income taxes	(43,649,943)	(53,445,860)
Benefit for income taxes	2,781,937	2,586,057
Net loss	(40,868,006)	(50,859,803)
Comprehensive loss	$ (40,868,006)	$ (50,859,803)
Loss per share attributable to common stockholders basic and diluted (in dollars per share)	$ (1.31)	$ (1.67)
Weighted average common shares outstanding basic and diluted (in shares)	31,242,176	30,393,952