Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Revenues:
Total revenues	$ 247	$ 258	$ 117
Operating expenses:
Research and development (Includes $25, ($39) and ($110) payments to/(from) a related party)	523	448	340
General and administrative (Includes $5, $2 and $— payments to a related party)	110	120	117
Impairment of long-lived assets (see Note 14, Leases)	0	20	0
Total operating expenses	633	588	457
Loss from operations	(386)	(330)	(340)
Non-operating income (expense):
Interest and other income, net	41	52	41
Interest expense	(8)	(4)	(2)
Total non-operating income, net	33	48	39
Loss before income taxes	(353)	(282)	(301)
Income tax expense	0	(1)	(6)
Net loss	$ (353)	$ (283)	$ (307)
Net loss per share, basic (in dollars per share)	$ (3.29)	$ (3.14)	$ (4.15)
Net loss per share, diluted (in dollars per share)	$ (3.29)	$ (3.14)	$ (4.15)
Shares used to compute net loss per share, basic (in shares)	107.4	90.1	74.0
Shares used to compute net loss per share, diluted (in shares)	107.4	90.1	74.0
License and development services
Revenues:
Total revenues	$ 221	$ 222	$ 80
Other Collaboration Revenue
Revenues:
Total revenues	$ 26	$ 36	$ 37