Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
OPERATING ACTIVITIES:
Net loss	$ (355,928)	$ (285,305)	$ (130,778)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	11,070	5,921	1,826
Deferred income tax			(7,547)
Stock-based compensation expense	22,362	5,828	1,497
Change in the estimated fair value of contingent consideration	31,842	52,793	17,860
Change in the estimated fair value of success payment liabilities	26,031	72,142	1,924
Non-cash expense in connection with license agreement and asset acquisition		1,530	17,685
Non-cash expense for operating lease right-of-use assets	6,844	4,250	2,095
Other non-cash items, net	(3,076)	(1,297)	(592)
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(861)	(1,436)	(4,300)
Operating lease right-of-use assets and liabilities	5,088	91	5,697
Accounts payable	(266)	1,982	(421)
Accrued expenses and other liabilities	5,840	5,519	9,536
Net cash used in operating activities	(251,054)	(137,982)	(85,518)
INVESTING ACTIVITIES:
Purchases of marketable securities	(491,387)	(387,432)	(141,519)
Proceeds from sales and maturities of marketable securities	280,025	158,741	82,977
Purchases of property and equipment	(29,862)	(23,872)	(26,124)
Acquisitions, net of cash acquired			(3,195)
Other investing activities	(4,574)
Net cash used in investing activities	(245,798)	(252,563)	(87,861)
FINANCING ACTIVITIES:
Proceeds from initial public offering, net of issuance costs	626,405
Proceeds from issuance of convertible preferred stock, net of issuance costs		435,538	223,739
Proceeds from employee stock purchase plan and exercise of stock options, net	5,346	149	1
Net cash provided by financing activities	631,751	435,687	223,740
Net increase in cash, cash equivalents, and restricted cash	134,899	45,142	50,361
Cash, cash equivalents, and restricted cash at beginning of period	126,949	81,807	31,446
Cash, cash equivalents, and restricted cash at end of period	261,848	126,949	81,807
SUPPLEMENTAL CASH FLOW INFORMATION:
Operating lease right-of-use assets obtained in exchange for lease obligations	39,996	26,521	48,863
Cash received for amounts related to tenant improvement allowances	5,445	91	5,697
Purchases of property and equipment included in accounts payable and accrued liabilities	$ 3,015	$ 3,140	2,495
Issuance of convertible preferred stock for acquisition			$ 135,971