Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Condensed Consolidated Statements of Operations
Collaboration and other research and development revenues	$ 10,749	$ 2,330	$ 16,472	$ 4,399
Revenue type	us-gaap:ServiceMember	us-gaap:ServiceMember	us-gaap:ServiceMember	us-gaap:ServiceMember
Operating expenses:
Research and development	$ 28,007	$ 23,565	$ 62,576	$ 39,408
General and administrative	14,081	14,414	31,852	31,903
Total operating expenses	42,088	37,979	94,428	71,311
Operating loss	(31,339)	(35,649)	(77,956)	(66,912)
Other income, net:
Other income (expense), net	7,175	(68)	14,509	(111)
Interest income, net	592	1,931	2,151	3,988
Total other income, net	7,767	1,863	16,660	3,877
Net loss	$ (23,572)	$ (33,786)	$ (61,296)	$ (63,035)
Net loss per share basic and diluted	$ (0.43)	$ (0.69)	$ (1.12)	$ (1.29)
Weighted-average common shares outstanding, basic and diluted	55,346,052	49,070,574	54,968,123	48,955,043