Condensed Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Revenues:
Total revenues	$ 145	$ 25
Operating expenses:
Research and development (Net of recoveries of $16 and $33 from a related party)	109	81
General and administrative	32	30
Impairment of long-lived assets	20	0
Total operating expenses	161	111
Loss from operations	(16)	(86)
Non-operating income (expense):
Interest and other income, net	13	9
Effective interest on liability for sale of future royalties	(1)	(1)
Total non-operating income, net	12	8
Loss before income taxes	(4)	(78)
Income tax expense	0	(2)
Net loss	$ (4)	$ (80)
Net loss per share, basic (in dollars per share)	$ (0.05)	$ (1.09)
Net loss per share, diluted (in dollars per share)	$ (0.05)	$ (1.09)
Shares used to compute loss per share, basic (in shares)	86.2	73.0
Shares used to compute loss per share, diluted (in shares)	86.2	73.0
License and Development Services Revenue
Revenues:
Total revenues	$ 135	$ 17
Other Collaboration Revenue
Revenues:
Total revenues	$ 10	$ 8