CONDENSED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Revenue:
Collaboration revenue	$ 12,500	$ 12,500
Total revenue	12,500	12,500
Operating expenses:
Research and development	7,994,472	6,531,553
General and administrative	3,745,262	3,819,758
Total operating expenses	11,739,734	10,351,311
Loss from operations	(11,727,234)	(10,338,811)
Other income (expense), net:
Interest income, net	235,451	189,535
Other income (expense), net	3,198	(3,464)
Net loss	$ (11,488,585)	$ (10,152,740)
Net loss per share -basic and diluted (in dollars per share)	$ (0.27)	$ (0.24)
Items included in other comprehensive income (loss):
Unrealized gain (loss) and amounts reclassified to net loss on available-for-sale securities	$ (12,681)	$ 110,136
Other comprehensive income (loss)	(12,681)	110,136
Comprehensive loss	$ (11,501,266)	$ (10,042,604)
Weighted-average number of common shares used in net loss per share calculation - basic and diluted (in shares)	42,434,709	42,109,828