Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Income Statement [Abstract]
License revenue	$ 0	$ 0	$ 7,500	$ 0
Operating expenses:
Research and development	22,608	19,177	42,588	33,928
General and administrative	21,930	10,598	38,093	19,638
Total operating expenses	44,538	29,775	80,681	53,566
Operating loss	(44,538)	(29,775)	(73,181)	(53,566)
Other income, net	205	575	412	1,460
Net loss	(44,333)	(29,200)	(72,769)	(52,106)
Other comprehensive loss:
Net unrealized loss on marketable securities	(62)	194	(84)	140
Foreign currency translation adjustment	(39)	41	(72)	(13)
Comprehensive loss	$ (44,434)	$ (28,965)	$ (72,925)	$ (51,979)
Net loss per share — basic (in USD per share)	$ (0.45)	$ (0.36)	$ (0.74)	$ (0.68)
Net loss per share — diluted (in USD per share)	$ (0.45)	$ (0.36)	$ (0.74)	$ (0.68)
Weighted-average common shares used to compute net loss per share - basic (in shares)	98,018	80,229	97,885	77,010
Weighted-average common shares used to compute net loss per share - diluted (in shares)	98,018	80,229	97,885	77,010