CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Revenue
License and collaboration revenues	$ 0	$ 0	$ 0	$ 267
Total revenue	0	0	0	267
Expenses
Research and development	134,575	65,083	238,646	136,791
General and administrative	29,611	19,779	57,961	37,825
Total operating expenses	164,186	84,862	296,607	174,616
Loss from operations	(164,186)	(84,862)	(296,607)	(174,349)
Other (expense) income, net	(2,244)	2,003	(5,503)	4,835
Net loss	(166,430)	(82,859)	(302,110)	(169,514)
Unrealized gain (loss) on available-for-sale investments	145	1,577	(158)	1,395
Comprehensive loss	$ (166,285)	$ (81,282)	$ (302,268)	$ (168,119)
Basic net loss per share (USD per share)	$ (3.23)	$ (1.89)	$ (5.91)	$ (3.91)
Diluted net loss per share (USD per share)	$ (3.23)	$ (1.89)	$ (5.91)	$ (3.91)
Weighted average number of shares used in computing net loss per share, basic (shares)	51,472,901	43,825,723	51,128,048	43,356,207
Weighted average number of shares used in computing net loss per share, diluted (shares)	51,472,901	43,825,723	51,128,048	43,356,207