Condensed Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Revenues:
Total revenues	$ 39	$ 29	$ 184	$ 54
Operating expenses:
Research and development (Includes $14, $34, $30 and $67 of net recoveries from a related party)	115	84	224	165
General and administrative	30	28	62	58
Impairment of long-lived assets	0	0	20	0
Total operating expenses	145	112	306	223
Loss from operations	(106)	(83)	(122)	(169)
Non-operating income (expense):
Interest and other income, net	13	9	26	18
Effective interest on liability for sale of future royalties	0	0	(1)	(1)
Total non-operating income, net	13	9	25	17
Loss before income taxes	(93)	(74)	(97)	(152)
Income tax expense	0	(1)	0	(3)
Net loss	$ (93)	$ (75)	$ (97)	$ (155)
Net loss per share, basic (in dollars per share)	$ (1.02)	$ (1.04)	$ (1.09)	$ (2.13)
Net loss per share, diluted (in dollars per share)	$ (1.02)	$ (1.04)	$ (1.09)	$ (2.13)
Shares used to compute loss per share, basic (in shares)	91.1	73.2	88.6	73.1
Shares used to compute loss per share, diluted (in shares)	91.1	73.2	88.6	73.1
License and Development Services Revenue
Revenues:
Total revenues	$ 28	$ 19	$ 163	$ 36
Other Collaboration Revenue
Revenues:
Total revenues	$ 11	$ 10	$ 21	$ 18