CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenue
License and collaboration revenues	$ 11,424	$ 988	$ 11,690	$ 2,809
Total revenue	11,424	988	11,690	2,809
Operating expenses
Research and development	79,853	47,362	216,644	119,925
General and administrative	20,249	10,685	58,074	30,340
Total operating expenses	100,102	58,047	274,718	150,265
Loss from operations	(88,678)	(57,059)	(263,028)	(147,456)
Other income, net	1,342	2,786	6,178	6,576
Net loss	(87,336)	(54,273)	(256,850)	(140,880)
Unrealized (loss) gain on available-for-sale investments	(827)	103	568	412
Comprehensive loss	$ (88,163)	$ (54,170)	$ (256,282)	$ (140,468)
Basic and diluted net loss per share (USD per share)	$ (1.96)	$ (1.38)	$ (5.87)	$ (3.83)
Weighted average number of shares used in computing net loss per share, basic and diluted (shares)	44,614,226	39,197,213	43,778,607	36,799,173