STATEMENTS OF OPERATIONS - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue:
Licensing revenue	$ 100,000	$ 200,000	$ 100,000
Expenses:
Research and development	19,840,106	35,930,212	43,395,574
General and administrative	12,502,042	15,990,789	19,664,904
Depreciation and amortization	629,312	536,631	317,649
Total expenses	32,971,460	52,457,632	63,378,127
Loss before other income (expense)	(32,871,460)	(52,257,632)	(63,278,127)
Other income (expense):
Interest income	365,584	255,123	233,958
Interest expense	(3,831,211)	(2,754,677)	0
Other income (expense), net	(16,322)	159,148	20,151
Gain on warrant liabilities	1,367,777	3,827,617	4,437,628
Loss before provision for income taxes	(34,985,632)	(50,770,421)	(58,586,390)
Provision for income taxes	(800)	(800)	(800)
Net loss	$ (34,986,432)	$ (50,771,221)	$ (58,587,190)
Basic and diluted net loss per share (in dollars per share)	$ (1.46)	$ (3.78)	$ (5.82)
Basic and diluted weighted-average shares outstanding (in shares)	24,042,293	13,510,629	10,080,526