Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
OPERATING ACTIVITIES:
Net loss	$ (180,617)	$ (32,875)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	2,247	1,265
Stock-based compensation expense	4,158	755
Change in fair value of contingent consideration	11,393	362
Change in fair value of success payment liabilities	115,657	552
Non-cash expense in connection with license agreement		373
Non-cash expense for operating lease right-of-use assets	1,398	784
Other non-cash items, net	(1,013)	350
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(1,614)	(501)
Accounts payable	1,599	2,370
Accrued expenses and other liabilities	(3,121)	(2,982)
Net cash used in operating activities	(49,913)	(29,547)
INVESTING ACTIVITIES:
Purchases of marketable securities	(44,811)
Proceeds from sales and maturities of marketable securities	100,342	44,781
Purchases of property and equipment	(6,440)	(5,600)
Net cash provided by investing activities	49,091	39,181
FINANCING ACTIVITIES:
Proceeds from initial public offering of common stock, net of offering costs	626,405
Proceeds from exercise of stock options	298	2
Net cash provided by financing activities	626,703	2
Net increase in cash, cash equivalents, and restricted cash	625,881	9,636
Cash, cash equivalents, and restricted cash at beginning of period	126,949	81,807
Cash, cash equivalents, and restricted cash at end of period	752,830	91,443
SUPPLEMENTAL CASH FLOW DISCLOSURES:
Tenant improvement allowance included in operating lease liabilities	8,515	3,837
Purchases of property and equipment included in accounts payable and accrued liabilities	$ 3,157	644
Right-of-use assets obtained in exchange for operating lease liabilities		$ 14,271