Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Cash flow from operating activities
Net loss	$ (67,993)	$ (72,593)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	16,541	12,761
Depreciation and amortization	1,457	800
Noncash lease expense	1,976	538
Amortization of premiums on investments	1,670	506
Acquired in-process research and development	2,500
Effective interest on liability for sale of future royalties	391
Changes in operating assets and liabilities:
Receivable from collaboration partners ($715,273 and ($3,981) from a related party)	715,176	(4,186)
Prepaid expenses and other current assets	(5,590)	(4,568)
Other long-term assets (($1,135) and $0 to a related party)	(1,727)	63
Accounts payable	8,138	7,722
Accrued research and development	5,567	4,716
Other accrued liabilities	(8,462)	(2,007)
Deferred revenue (($16,254) and $193,140 to a related party)	(18,005)	(9,461)
Operating lease liabilities	92	(605)
Other long-term liabilities	2,270	(2)
Net cash provided by (used in) operating activities	654,001	(66,316)
Cash flow from investing activities
Purchases of short-term and long-term investments	(377,573)	(192,398)
Proceeds from maturities of short-term and long-term investments	93,817	251,365
Sales of short-term and long-term investments	18,484	7,500
Purchases of property and equipment	(2,788)	(3,641)
Net cash provided by (used in) investing activities	(268,060)	62,826
Cash flow from financing activities
Proceeds from issuance of common stock ($0 and $220,235 from a related party)		220,235
Proceeds from sale of future royalties	5,000
Proceeds from issuance of common stock pursuant to equity award plans	9,928	1,885
Net cash provided by financing activities	14,928	222,120
Net increase in cash and cash equivalents	400,869	218,630
Cash, cash equivalents and restricted cash at beginning of period	150,919	173,618
Cash, cash equivalents and restricted cash at end of period	551,788	392,248
Non-cash investing and financing activities:
Unpaid acquisition of in-process research and development	2,500
Unpaid portion of property and equipment purchases included in accounts payable and accrued liabilities	691	2,784
Vesting of early exercised stock options and restricted stock	$ 52	$ 183