CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Statement [Abstract]
Related party revenue	$ 18,575	$ 23,482	$ 56,923	$ 67,601
Operating expenses:
Research and development	38,714	46,979	122,983	123,912
General and administrative	8,867	6,460	27,411	19,849
Total operating expenses	47,581	53,439	150,394	143,761
Loss from operations	(29,006)	(29,957)	(93,471)	(76,160)
Interest income, net	106	260	335	1,823
Other income (expense), net	35	(68)	35	(159)
Net loss	$ (28,865)	$ (29,765)	$ (93,101)	$ (74,496)
Net loss per share, basic (in dollars per share)	$ (0.37)	$ (0.43)	$ (1.21)	$ (1.09)
Net loss per share, diluted (in dollars per share)	$ (0.37)	$ (0.43)	$ (1.21)	$ (1.09)
Weighted average shares used to compute net loss per share, basic (in shares)	77,408,893	68,815,696	76,851,508	68,174,654
Weighted average shares used to compute net loss per share, diluted (in shares)	77,408,893	68,815,696	76,851,508	68,174,654