STATEMENTS OF OPERATIONS - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenue:
Licensing revenue	$ 200,000	$ 100,000	$ 100,000
Expenses:
Research and development	35,930,212	43,395,574	36,677,706
General and administrative	15,990,789	19,664,904	12,845,231
Depreciation and amortization	536,631	317,649	182,927
Total expenses	52,457,632	63,378,127	49,705,864
Loss before other income (expense)	(52,257,632)	(63,278,127)	(49,605,864)
Other income (expense):
Interest income	255,123	233,958	305,331
Interest expense	(2,754,677)	0	0
Other income, net	159,148	20,151	132,114
Gain on warrant liabilities	3,827,617	4,437,628	19,051,239
Loss before provision for income taxes	(50,770,421)	(58,586,390)	(30,117,180)
Provision for income taxes	(800)	(800)	(800)
Net loss	$ (50,771,221)	$ (58,587,190)	$ (30,117,980)
Basic and diluted net loss per share (in dollars per share)	$ (0.63)	$ (0.97)	$ (0.55)
Basic and diluted weighted-average shares outstanding (in shares)	81,063,772	60,483,151	54,371,151