Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
CASH FLOWS FROM OPERATING ACTIVITIES
Net loss	$ (342,994)	$ (234,632)	$ (183,118)
Adjustments to reconcile net loss to net cash used in operating activities:
Acquired IPR&D expense	87,184	0	0
Impairment of long-lived assets	51,297	0	0
Stock-based compensation expense	33,144	47,084	81,924
Depreciation and amortization expense	19,631	20,250	18,020
Net amortization and accretion on marketable securities	(14,681)	(9,596)	(930)
Impairment of other investments	13,001	12,923	5,000
Change in fair value of contingent consideration payable	(3,804)	0	0
Non-cash lease income	(2,198)	(1,873)	(1,553)
Loss on property and equipment disposals, net	1,341	1,509	103
Change in fair value of success payment liabilities	(1,165)	(2,780)	(5,130)
Gain on marketable equity security	(30)	0	0
Change in fair value of equity warrant	0	0	1,067
Gain on other investments	0	0	(2,923)
Changes in operating assets and liabilities:
Prepaid expenses, other current assets and other assets	1,775	3,125	(1,968)
Accounts payable	(3,234)	1,464	667
Accrued liabilities and other current liabilities	(1,250)	(719)	(463)
Deferred revenue	0	0	(84,653)
Operating lease liabilities, non-current	0	0	4,855
Other non-current liabilities	(411)	(449)	(453)
Net cash used in operating activities	(162,394)	(163,694)	(169,555)
CASH FLOWS FROM INVESTING ACTIVITIES
Purchases of property and equipment	(464)	(2,686)	(24,276)
Purchases of marketable securities	(394,707)	(476,880)	(406,316)
Maturities of marketable securities	548,941	663,614	419,052
Acquisition of assets, net of cash acquired	(31,346)	0	0
Net cash provided by (used in) investing activities	122,424	184,048	(11,540)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from exercise of stock options	154	306	9,577
Proceeds from employee stock purchase plan	1,248	1,894	1,519
Taxes paid related to net share settlement of equity awards	(76)	(457)	(461)
Net cash provided by financing activities	1,326	1,743	10,635
Net (decrease) increase in cash, cash equivalents and restricted cash	(38,644)	22,097	(170,460)
Cash, cash equivalents and restricted cash at beginning of period	145,931	123,834	294,294
Cash, cash equivalents and restricted cash at end of period	107,287	145,931	123,834
Represented by:
Cash and cash equivalents	105,597	145,647	123,554
Restricted cash	1,690	284	280
Total	107,287	145,931	123,834
SUPPLEMENTAL CASH FLOW INFORMATION
Cash paid for amounts included in the measurement of lease liabilities	11,467	10,845	10,870
Cash received for amounts related to tenant improvement allowances	0	0	4,761
Non-cash investing and financing activities:
Issuance of common stock related to the purchase of the IPR&D asset on Closing Date (Note 3)	36,011	0	0
Contingent consideration payable	11,404	0	0
Purchases of property and equipment included in accounts payable and accrued liabilities	144	29	1,325
Acquisition of PACT Series D convertible preferred shares	0	0	2,923
Remeasurement of operating lease right-of-use asset for lease modification	$ 0	$ 0	$ 31