Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Statement of Comprehensive Income [Abstract]
Revenue	$ 13	$ 27	$ 16	$ 92
Operating expenses:
Research and development	40,261	47,471	83,435	92,101
General and administrative	12,256	19,030	25,750	38,309
Other operating income, net	(976)	(569)	(2,066)	(1,857)
Total operating expenses	51,541	65,932	107,119	128,553
Loss from operations	(51,528)	(65,905)	(107,103)	(128,461)
Interest income, net	6,364	5,264	13,183	9,761
Other (expense) income, net	(645)	(326)	445	774
Impairment of other investments	0	(2,923)	(13,001)	(12,923)
Total other income (loss), net	5,719	2,015	627	(2,388)
Net loss	(45,809)	(63,890)	(106,476)	(130,849)
Other comprehensive loss:
Net unrealized gain (loss) on marketable securities	7	1,500	(303)	5,220
Comprehensive loss	$ (45,802)	$ (62,390)	$ (106,779)	$ (125,629)
Net loss per common share, basic (in dollars per share)	$ (0.18)	$ (0.26)	$ (0.42)	$ (0.52)
Net loss per common share, diluted (in dollars per share)	$ (0.18)	$ (0.26)	$ (0.42)	$ (0.52)
Weighted-average shares used to compute net loss per common share, basic (in shares)	255,398	250,204	254,825	249,899
Weighted-average shares used to compute net loss per common share, diluted (in shares)	255,398	250,204	254,825	249,899