Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)	$ 528,584	$ (298,665)	$ (174,683)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	5,278	4,400	3,294
Amortization of intangible assets	533	1,042	1,223
Impairment of intangible assets		832
(Accretion of discounts) amortization of premiums on investments, net	(244)	1,548	(179)
Noncash lease expense	6,172	3,371
Change in fair value of equity investments	(138,049)
Change in estimated fair value of contingent consideration	91,848	38,394	8,330
Payment of contingent consideration in excess of acquisition date fair value	(8,140)	(15,752)
Initial fair value of derivative liability			13,599
Change in estimated fair value of derivative liability		16,796	(1,150)
Change in estimated fair value of convertible preferred stock warrant liability			2,049
Stock-based compensation	83,784	27,600	8,719
Change in deferred income taxes	15,186	(52)
Gain from a sublease termination	(4,844)
Common stock issued in connection with license agreement			617
Other	697	23	345
Changes in operating assets and liabilities:
Receivable from collaboration	(773,079)
Prepaid expenses and other current assets	(3,665)	(4,475)	(4,619)
Other assets	(1,483)	(1,100)	(1,881)
Accounts payable	(171)	(790)	964
Accrued liabilities and other long-term liabilities	58,498	46,614	10,211
Operating lease liabilities	(535)	(3,684)
Deferred revenue	92,041	(7,043)	3,529
Net cash used in operating activities	(47,589)	(190,941)	(129,632)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment	(21,817)	(6,549)	(8,940)
Purchases of investments	(420,240)	(403,841)	(643,898)
Maturities of investments	301,243	400,348	396,680
Proceeds from disposal of an asset held for sale		180
Net cash used in investing activities	(140,814)	(9,862)	(256,158)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common stock		323,214	126,411
Proceeds from issuance of common stock in connection with a collaboration agreement	85,213	206,699
Proceeds from issuance of convertible preferred stock, net of issuance cost			317,335
Proceeds received from financing lease obligation			1,202
Payment of contingent consideration		(4,248)
Payment of principal on financing lease obligations	(259)	(250)	(95)
Proceeds from repayment of promissory notes			3,265
Proceeds from exercise of stock options	13,077	4,059	1,129
Proceeds from issuance of common stock under the employee stock purchase plan	2,300
Cash paid in lieu of fractional shares related to reverse stock split			(3)
Net cash provided by financing activities	100,331	529,474	449,244
Net (decrease) increase in cash, cash equivalents and restricted cash and cash equivalents	(88,072)	328,671	63,454
Cash, cash equivalents and restricted cash and cash equivalents at beginning of period	451,487	122,816	59,362
Cash, cash equivalents and restricted cash and cash equivalents at end of period	363,415	451,487	122,816
NONCASH INVESTING AND FINANCING ACTIVITIES:
Property and equipment purchases included in accounts payable and accrued liabilities	8,731	382	892
Common stock issued for payment of contingent consideration	1,860
Conversion of preferred stock into common stock upon completion of initial public offering			636,612
Operating lease liabilities obtained in exchange of right-of-use asset	77,187	48,495
Advanced proceeds applied to convertible preferred stock issuance			10,140
Reclassification of derivative liability to additional paid-in capital		29,245
Reclassification of preferred stock warrant liability to additional paid-in capital			3,073
RECONCILIATION OF CASH, CASH EQUIVALENTS AND RESTRICTED CASH TO THE CONSOLIDATED BALANCE SHEETS:
Cash and cash equivalents	347,815	436,575	109,335
Restricted cash and cash equivalents, current	8,594	7,993	6,181
Restricted cash and cash equivalents, noncurrent	7,006	6,919	7,300
Total cash, cash equivalents and restricted cash	$ 363,415	$ 451,487	$ 122,816