Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Statement of Comprehensive Income [Abstract]
Revenue	$ 10,650	$ 7,756	$ 657
Operating expenses (income):
Research and development	138,693	182,243	63,595
General and administrative	89,057	46,881	39,151
Other operating income, net	(2,324)	(9,431)	0
Total operating expenses	225,426	219,693	102,746
Loss from operations	(214,776)	(211,937)	(102,089)
Interest income, net	1,165	5,939	8,121
Other (expense) income, net	(161)	1,526	(35,409)
Impairment of other investments	(36,447)	0	0
Total other (loss) income, net	(35,443)	7,465	(27,288)
Net loss	(250,219)	(204,472)	(129,377)
Other comprehensive (loss) gain:
Net unrealized (loss) gain on marketable securities	(1,879)	(198)	454
Comprehensive loss	(252,098)	(204,670)	(128,923)
Net loss attributed to common stockholders:
Net loss	(250,219)	(204,472)	(129,377)
Deemed dividends upon issuance or repurchase of convertible preferred stock	0	(3,582)	(1,144)
Net loss attributed to common stockholders	$ (250,219)	$ (208,054)	$ (130,521)
Net loss per common share, basic (in dollars per share)	$ (1.84)	$ (15.69)	$ (24.04)
Net loss per common share, diluted (in dollars per share)	$ (1.84)	$ (15.69)	$ (24.04)
Weighted-average shares used to compute net loss per common share, basic (in shares)	135,918	13,258	5,429
Weighted-average shares used to compute net loss per common share, diluted (in shares)	135,918	13,258	5,429