Selected Quarterly Financial Data (Unaudited) (Details) - USD ($)		1 Months Ended	3 Months Ended								12 Months Ended
	Aug. 14, 2017	Aug. 31, 2017	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Data [Abstract]
License and other revenue	$ 25,000,000	$ 25,000,000	$ 0	$ 25,000,000	$ 0	$ 0					$ 25,000,000	$ 0	$ 0
Product revenue, net			1,911,000	0	0	0					1,910,403	0	0
Sales force revenue			278,000	0	0	0					278,165	0	0
Grant revenue			45,000	38,000	158,000	384,000					624,569	1,152,987	0
Cost of product sales			636,000	0	0	0					635,648	0	0
Research and development			1,961,000	965,000	494,000	953,000	$ 773,000	$ 4,582,000	$ 2,502,000	$ 2,293,000	4,372,578	10,149,879	6,587,183
General and administrative			3,021,000	2,152,000	1,439,000	1,330,000	1,095,000	1,703,000	1,636,000	2,649,000	7,941,584	7,083,155	4,422,764
Sales and marketing			973,000	0	0	0					973,345	0	0
Change in fair value of warrant liability, unit purchase option liability and investor rights obligation			(28,000)	0	2,000	(4,000)	130,000	(101,000)	91,000	(47,000)	(29,624)	72,625	1,313,049
Interest expense, net			31,000	29,000	(26,000)	(58,000)	(83,000)	(104,000)	(127,000)	(151,000)	(24,016)	(464,181)	(793,205)
Net income (loss)			$ (3,091,000)	$ 18,721,000	$ (1,799,000)	$ (1,961,000)	$ (1,639,000)	$ (6,169,000)	$ (3,524,000)	$ (5,140,000)	$ 11,869,823	$ (16,471,603)	$ (10,490,103)
Net income (loss) per share of common stock, basic (in dollars per share)			$ (0.11)	$ 0.52	$ (0.14)	$ (0.19)					$ 0.42	$ (1.87)	$ (4.71)
Net income (loss) per share of common stock, diluted (in dollars per share)			$ (0.11)	$ 0.52	$ (0.14)	$ (0.19)					$ 0.42	$ (1.87)	$ (4.71)
Net loss per share of common stock, basic and diluted (in dollars per share)							$ (0.18)	$ (0.70)	$ (0.41)	$ (0.59)