Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Cash flow from operating activities
Net income (loss)	$ (267)	$ 53	$ (123)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	65	55	22
Depreciation and amortization	6	4	3
Noncash lease expense	8	3	1
Amortization of premiums on marketable securities		5
Other items, net	3
Changes in operating assets and liabilities:
Receivable from collaboration partners ($706, ($17) and ($1) from a related party)	704	(17)	(1)
Other assets (($2), $ - and $ - from a related party)	2	(3)	(6)
Accounts payable	8	(5)	9
Deferred revenue (($107), ($361) and $195 to a related party)	(112)	(368)	188
Other liabilities	21	17	18
Net cash provided by (used in) operating activities	438	(256)	111
Cash flow from investing activities
Purchases of marketable securities	(1,241)	(719)	(740)
Proceeds from maturities of marketable securities	694	690	308
Proceeds from sales of marketable securities	143	51	1
Purchases of property and equipment	(6)	(26)	(3)
Purchases of in-process research and development	(6)
Collaboration reimbursements of in-process research and development from a related party	3
Net cash used in investing activities	(413)	(4)	(434)
Cash flow from financing activities
Proceeds from issuance of common stock and rights to purchase additional shares ($ -, $220 and $164 from a related party)		220	434
Proceeds from sale of future royalties	10	5
Proceeds from issuance of common stock pursuant to equity award plans	23	12	5
Net cash provided by financing activities	33	237	439
Net increase (decrease) in cash, cash equivalents and restricted cash	58	(23)	116
Cash, cash equivalents and restricted cash at beginning of period	151	174	58
Cash, cash equivalents and restricted cash at end of period	209	151	174
Supplemental disclosure of cash flow information
Income taxes paid	3
Non-cash investing and financing activities:
Unpaid portion of property and equipment purchases included in accounts payable and accrued liabilities	$ 3	1	2
Unpaid portion of other assets included in accrued research and development		1
Vesting of early exercised stock options and restricted stock		$ 1	$ 1