Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024
Cash flow from operating activities
Net loss	$ (247)	$ (189)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	45	59
Depreciation and amortization	7	7
Noncash lease expense	5	5
Impairment of long-lived assets	0	20
Amortization of discounts on marketable securities	(10)	(19)
Other items, net	2	2
Changes in operating assets and liabilities:
Receivable from collaboration partners ($6 and $18 from a related party)	9	32
Other assets ($— and $6 from a related party)	5	16
Accounts payable ($29 and $— to a related party)	24	(2)
Deferred revenue (($214) and ($20) to a related party)	(214)	(14)
Other liabilities	12	13
Net cash used in operating activities	(362)	(70)
Cash flow from investing activities
Purchases of marketable securities	(679)	(871)
Proceeds from maturities of marketable securities	858	726
Proceeds from sales of marketable securities	70	15
Purchases of property and equipment	(1)	(5)
Net cash provided by (used in) investing activities	248	(135)
Cash flow from financing activities
Proceeds from issuance of common stock ($14 and $228 from a related party)	150	228
Proceeds from debt issuances, net	49	47
Proceeds from issuance of common stock pursuant to equity award plans	3	6
Payments of employee taxes related to net settlement of equity awards	0	(2)
Net cash provided by financing activities	202	279
Net increase in cash, cash equivalents and restricted cash	88	74
Cash, cash equivalents and restricted cash at beginning of period	153	130
Cash, cash equivalents and restricted cash at end of period	$ 241	$ 204