Consolidated Statements of Operations (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Licensing revenue	$ 500,000	$ 500,000
Operating expenses:
Research and development	14,969,382	9,364,228	15,770,166
General and administrative	8,860,549	6,547,257	6,372,551
Acquisition costs	1,385,263
Total operating expenses	25,215,194	15,911,485	22,142,717
Loss from operations	(24,715,194)	(15,411,485)	(22,142,717)
Other income (expense):
Gain (loss) from valuation of common stock warrant liability	204,279	8,090,636	(4,117,534)
Gain from valuation of earn-out milestone liability	213,949
Investment income (loss), net	77,194	(12,744)	52,322
Interest expense	(1,326,438)	(915,235)	(359,413)
Other income (expense)	51,937	(2,530)	(1,040)
Total other (expense) income	(779,079)	7,160,127	(4,425,665)
Net loss	(25,494,273)	(8,251,358)	(26,568,382)
Non-cash deemed dividend from beneficial conversion feature on convertible preferred stock		(4,601,410)
Net loss attributable to common shareholders	$ (25,494,273)	$ (12,852,768)	$ (26,568,382)
Net loss per common share – basic and diluted (in Dollars per share)	$ (1.38)	$ (0.95)	$ (3.44)
Weighted average common shares outstanding – basic and diluted (in Shares)	18,472,399	13,540,566	7,730,904