CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Revenue
License and collaboration revenues	$ 0	$ 577	$ 267	$ 1,821
Total revenue	0	577	267	1,821
Operating expenses
Research and development	65,083	38,324	136,791	72,564
General and administrative	19,779	9,894	37,825	19,656
Total operating expenses	84,862	48,218	174,616	92,220
Loss from operations	(84,862)	(47,641)	(174,349)	(90,399)
Other income, net	2,003	1,946	4,835	3,792
Net loss	(82,859)	(45,695)	(169,514)	(86,607)
Unrealized gain on available-for-sale investments	1,577	151	1,395	309
Comprehensive loss	$ (81,282)	$ (45,544)	$ (168,119)	$ (86,298)
Basic and diluted net loss per share (USD per share)	$ (1.89)	$ (1.26)	$ (3.91)	$ (2.43)
Weighted average number of shares used in computing net loss per share, basic and diluted (shares)	43,825,723	36,173,605	43,356,207	35,580,279