Condensed Consolidated Statements of Operations - USD ($) shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Revenues:
Total revenues	$ 32,000,000	$ 33,000,000	$ 86,000,000	$ 78,000,000
Operating expenses:
Research and development (Net of recoveries of $22, $27, $89 and $93 from a related party)	82,000,000	77,000,000	247,000,000	208,000,000
General and administrative	30,000,000	26,000,000	88,000,000	76,000,000
Total operating expenses	112,000,000	103,000,000	335,000,000	284,000,000
Loss from operations	(80,000,000)	(70,000,000)	(249,000,000)	(206,000,000)
Non-operating income (expense):
Interest and other income, net	12,000,000	5,000,000	30,000,000	8,000,000
Effective interest on liability for sale of future royalties	(1,000,000)	0	(2,000,000)	(1,000,000)
Total non-operating income, net	11,000,000	5,000,000	28,000,000	7,000,000
Loss before income taxes	(69,000,000)	(65,000,000)	(221,000,000)	(199,000,000)
Income tax expense	(2,000,000)	0	(5,000,000)	(1,000,000)
Net loss	$ (71,000,000)	$ (65,000,000)	$ (226,000,000)	$ (200,000,000)
Net loss per share, basic (in dollars per share)	$ (0.94)	$ (0.90)	$ (3.07)	$ (2.78)
Net loss per share, diluted (in dollars per share)	$ (0.94)	$ (0.90)	$ (3.07)	$ (2.78)
Shares used to compute net loss per share, basic (in shares)	74.6	72.2	73.6	71.8
Shares used to compute net loss per share, diluted (in shares)	74.6	72.2	73.6	71.8
License and Development Services Revenue
Revenues:
Total revenues	$ 22,000,000	$ 23,000,000	$ 58,000,000	$ 48,000,000
Other Collaboration Revenue
Revenues:
Total revenues	$ 10,000,000	$ 10,000,000	$ 28,000,000	$ 30,000,000