CONDENSED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Revenue:
Collaboration revenue	$ 32,500	$ 32,500	$ 57,500	$ 57,500
Total revenue	32,500	32,500	57,500	57,500
Operating expenses:
Research and development	4,089,677	5,985,230	20,739,170	19,304,124
General and administrative	3,011,176	2,987,168	10,061,722	14,201,399
Acquired in-process research and development	16,493,132		16,493,132
Total operating expenses	23,593,985	8,972,398	47,294,024	33,505,523
Loss from operations	(23,561,485)	(8,939,898)	(47,236,524)	(33,448,023)
Other income (expense), net:
Interest income, net	264,932	232,240	734,065	629,289
Other income (expense), net	29,735	262	2,328	(4,062)
Net loss	$ (23,266,818)	$ (8,707,396)	$ (46,500,131)	$ (32,822,796)
Net loss per share -basic and diluted (in dollars per share)	$ (0.55)	$ (0.21)	$ (1.09)	$ (0.78)
Items included in other comprehensive income (loss):
Unrealized gain (loss) on available-for-sale securities	$ 30,303	$ (64,606)	$ 36,636	$ 111,039
Other comprehensive income (loss)	30,303	(64,606)	36,636	111,039
Comprehensive loss	$ (23,236,515)	$ (8,772,002)	$ (46,463,495)	$ (32,711,757)
Weighted-average number of common shares used in net loss per share calculation - basic and diluted (in shares)	42,636,567	42,263,311	42,525,693	42,184,182