Condensed Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Revenue:
Total revenue	$ 5,208	$ 2,874	$ 9,590	$ 2,874
Operating expenses:
Research and development	24,356	17,002	47,964	30,429
General and administrative	4,994	3,685	8,902	7,382
Total operating expenses	29,350	20,687	56,866	37,811
Operating loss	(24,142)	(17,813)	(47,276)	(34,937)
Other income	947	467	2,036	778
Loss before benefit from income taxes	(23,195)	(17,346)	(45,240)	(34,159)
Benefit from income taxes	235	152	320	198
Net loss	$ (22,960)	$ (17,194)	$ (44,920)	$ (33,961)
Net loss per share:
Basic and Diluted	$ (0.58)	$ (0.52)	$ (1.13)	$ (1.03)
Weighted average shares:
Basic and Diluted	39,818,162	33,315,809	39,685,954	33,000,487
Other comprehensive income, net of tax of $0:
Change in unrealized gains (losses) on available-for- sale marketable securities	$ 92	$ 57	$ 279	$ 13
Total comprehensive loss	(22,868)	(17,137)	(44,641)	(33,948)
License and Milestone Fees [Member]
Revenue:
Total revenue	$ 5,208	$ 2,874	9,450	$ 2,874
Clinical Compound Revenue [Member]
Revenue:
Total revenue			$ 140