Condensed Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Revenues:
Total revenues	$ 48	$ 32	$ 232	$ 86
Operating expenses:
Research and development (Includes $2, $22, $32 and $89 of net recoveries from a related party)	123	82	347	247
General and administrative	30	30	92	88
Impairment of long-lived assets	0	0	20	0
Total operating expenses	153	112	459	335
Loss from operations	(105)	(80)	(227)	(249)
Non-operating income (expense):
Interest and other income, net	14	12	40	30
Interest expense	(1)	(1)	(2)	(2)
Total non-operating income, net	13	11	38	28
Loss before income taxes	(92)	(69)	(189)	(221)
Income tax expense	0	(2)	0	(5)
Net loss	$ (92)	$ (71)	$ (189)	$ (226)
Net loss per share, basic (in dollars per share)	$ (1.00)	$ (0.94)	$ (2.11)	$ (3.07)
Net loss per share, diluted (in dollars per share)	$ (1.00)	$ (0.94)	$ (2.11)	$ (3.07)
Shares used to compute loss per share, basic (in shares)	91.4	74.6	89.6	73.6
Shares used to compute loss per share, diluted (in shares)	91.4	74.6	89.6	73.6
License and Development Services Revenue
Revenues:
Total revenues	$ 41	$ 22	$ 204	$ 58
Other Collaboration Revenue
Revenues:
Total revenues	$ 7	$ 10	$ 28	$ 28