Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Cash flow from operating activities
Net loss	$ (283)	$ (307)	$ (267)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Stock-based compensation expense	76	73	65
Depreciation and amortization	10	8	6
Noncash lease expense	7	8	8
Impairment on right-of use assets	20	0	0
Amortization of discounts on marketable securities	(25)	(19)	0
Other items, net	3	2	3
Changes in operating assets and liabilities:
Receivable from collaboration partners ($14, $19 and $704 from a related party)	28	15	704
Other assets ($6, ($4) and ($2) from a related party)	22	(14)	2
Accounts payable	3	(1)	8
Deferred revenue (($56), ($77) and ($107) to a related party)	(56)	(68)	(112)
Other liabilities	25	(3)	21
Net cash provided by (used in) operating activities	(170)	(306)	438
Cash flow from investing activities
Purchases of marketable securities	(1,043)	(788)	(1,241)
Proceeds from maturities of marketable securities	929	982	694
Proceeds from sales of marketable securities	36	24	143
Purchases of property and equipment	(6)	(24)	(6)
Other items, net	0	0	(3)
Net cash provided by (used in) investing activities	(84)	194	(413)
Cash flow from financing activities
Proceeds from issuance of common stock ($228, $20 and $— from a related party), net	228	25	0
Proceeds from debt issuances, net	47	0	0
Proceeds from issuance of common stock pursuant to equity award plans	9	8	23
Payments of employee taxes related to net settlement of equity awards	(7)	0	0
Proceeds from sale of future royalties	0	0	10
Net cash provided by financing activities	277	33	33
Net increase (decrease) in cash, cash equivalents and restricted cash	23	(79)	58
Cash, cash equivalents and restricted cash at beginning of period	130	209	151
Cash, cash equivalents and restricted cash at end of period	153	130	209
Supplemental disclosure of cash flow information
Income taxes paid	0	5	3
Interest paid	1	0	0
Non-cash investing and financing activities:
Unpaid portion of property and equipment purchases included in Accounts payable and Other current liabilities	$ 0	$ 2	$ 3