Consolidated Statements of Operations - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Licensing revenue	$ 500,000	$ 500,000
Operating expenses:
Research and development	14,623,068	14,659,941
General and administrative	6,526,752	6,686,852
Total operating expenses	21,149,820	21,346,793
Loss from operations	(20,649,820)	(20,846,793)
Other income (expense):
Gain (loss) from valuation of earn-out milestone liability	733,186	(257,702)
Loss from valuation of common stock warrant liability		(61,246)
Investment income, net	26,922	63,588
Interest expense	(722,993)	(1,357,182)
Other income (expense)	3,002	(1,749)
Total other expense	(1,403,906)	(1,614,291)
Net loss	$ (22,053,726)	$ (22,461,084)
Net loss per common share – basic and diluted (in dollars per share)	$ (0.85)	$ (1.03)
Weighted average common shares outstanding – basic and diluted (in shares)	25,956,751	21,813,228
In-Process Research and Development [Member]
Other income (expense):
Loss from impairment of in-process research and development	$ (1,444,023)