CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Statement [Abstract]
Net product revenue	$ 407,241	$ 586,134	$ 978,221	$ 698,819
Other revenue	6,360	12,940	13,450	12,940
Total revenue	413,601	599,074	991,671	711,759
Costs and expenses:
Cost of product revenue	148,756	221,090	373,187	529,041
Research and development	4,739,360	5,665,357	12,730,554	16,147,357
Selling, general and administrative	4,934,937	5,447,847	14,520,596	15,937,326
Total costs and expenses	9,823,053	11,334,294	27,624,337	32,613,724
Loss from operations	(9,409,452)	(10,735,220)	(26,632,666)	(31,901,965)
Interest income, net	77,339	97,726	227,535	308,877
Net loss	(9,332,113)	(10,637,494)	(26,405,131)	(31,593,088)
Net loss attributable to common stockholders	$ (9,332,113)	$ (10,637,494)	$ (26,405,131)	$ (31,593,088)
Net loss per share attributable to common stockholders - basic and diluted (in usd per share)	$ (0.54)	$ (0.65)	$ (1.54)	$ (1.96)
Weighted-average number of common shares outstanding — basic and diluted (in shares)	17,386,249	16,361,617	17,131,887	16,104,510