Consolidated Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Income Statement [Abstract]
License and collaboration revenue	$ 63,573	$ 20,340	$ 0
Operating expenses:
Research and development	272,533	282,001	244,650
General and administrative	71,553	78,801	64,402
Total operating expenses	344,086	360,802	309,052
Loss from operations	(280,513)	(340,462)	(309,052)
Other income (expense), net:
Gain on sale of ATOM Facility	50,237	0	0
Interest and other income, net	1,986	367	2,447
Total other income (expense), net, Total	52,223	367	2,447
Loss before provision for income taxes	(228,290)	(340,095)	(306,605)
Provision for income taxes	12	46	15
Net loss	(228,302)	(340,141)	(306,620)
Other comprehensive (loss) gain:
Unrealized (loss) gain on available-for-sale securities	(1,699)	(664)	76
Comprehensive loss	$ (230,001)	$ (340,805)	$ (306,544)
Net loss per common share:
Basic net loss per common share	$ (2.24)	$ (3.63)	$ (4.15)
Diluted net loss per common share	$ (2.24)	$ (3.63)	$ (4.15)
Basic weighted-average shares outstanding	101,990	93,670	73,973
Diluted weighted-average shares outstanding	101,990	93,670	73,973