Condensed Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenue:
Total revenue	$ 5,785	$ 5,062	$ 15,375	$ 7,936
Operating expenses:
Research and development	35,992	22,303	83,956	52,732
General and administrative	4,226	3,227	13,128	10,609
Total operating expenses	40,218	25,530	97,084	63,341
Operating loss	(34,433)	(20,468)	(81,709)	(55,405)
Other income	1,261	1,002	3,297	1,780
Loss before benefit from income taxes	(33,172)	(19,466)	(78,412)	(53,625)
Benefit from income taxes	330	66	650	264
Net loss	$ (32,842)	$ (19,400)	$ (77,762)	$ (53,361)
Net loss per share:
Basic and Diluted	$ (0.74)	$ (0.51)	$ (1.88)	$ (1.54)
Weighted average shares:
Basic and Diluted	44,517,134	38,034,216	41,314,044	34,696,835
Other comprehensive income, net of tax of $0:
Change in unrealized gains (losses) on available-for- sale marketable securities	$ (12)	$ 70	$ 267	$ 83
Total comprehensive loss	(32,854)	(19,330)	(77,495)	(53,278)
License and Milestone Fees [Member]
Revenue:
Total revenue	$ 5,785	5,029	15,235	7,903
Clinical Compound Revenue [Member]
Revenue:
Total revenue		$ 33	$ 140	$ 33