Condensed Statements of Operations and Comprehensive Loss - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Revenues:
Collaboration revenue	$ 10,008,431	$ 0	$ 17,006,507	$ 0
Total revenues	10,008,431	0	17,006,507	0
Operating expenses:
Research and development	13,217,925	4,246,488	21,143,636	8,944,950
General and administrative	2,194,184	2,238,134	4,957,209	4,814,261
Total operating expenses	15,412,109	6,484,622	26,100,845	13,759,211
Loss from operations	(5,403,678)	(6,484,622)	(9,094,338)	(13,759,211)
Other income (expense):
Interest income	218,639	34,377	389,480	61,355
Interest expense	(186,986)	(17,500)	(284,313)	(35,000)
Other expense	(44,862)	(3,400)	(50,461)	(10,173)
Total other (expense) income	(13,209)	13,477	54,706	16,182
Net loss	(5,416,887)	(6,471,145)	(9,039,632)	(13,743,029)
Other comprehensive income (loss):
Net unrealized (losses) gains on marketable securities	(3,476)	13,241	(16,493)	22,884
Comprehensive loss	$ (5,420,363)	$ (6,457,904)	$ (9,056,125)	$ (13,720,145)
Net loss per share, basic and diluted	$ (0.19)	$ (0.30)	$ (0.33)	$ (0.65)
Weighted average shares outstanding used in computing net loss per share, basic and diluted	28,103,393	21,542,188	27,138,536	21,085,610