Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (168,911)	$ (77,240)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,269	1,000
Amortization of intangible assets	133	306
Amortization of premiums on investments, net	409	562
Noncash lease expense	1,484	816
Change in estimated fair value of contingent consideration	44,462	7,165
Change in estimated fair value of derivative liability		16,796
Stock-based compensation	15,471	2,967
Other	19	5
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	943	549
Other assets	(63)	(125)
Accounts payable	(1,317)	12,944
Accrued liabilities and other long-term liabilities	(18,827)	(10,204)
Operating lease liabilities	4	(761)
Deferred revenue	35,395	(3,189)
Net cash used in operating activities	(89,529)	(48,409)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment	(667)	(1,302)
Purchases of investments	(5,000)	(40,472)
Maturities of investments	93,201	145,813
Proceeds from disposal of an asset held for sale		180
Net cash provided by investing activities	87,534	104,219
CASH FLOWS FROM FINANCING ACTIVITIES:
Payment of principal on financing lease obligation	(62)	(58)
Proceeds from exercise of stock options	2,352	143
Net cash provided by financing activities	87,503	85
Net increase in cash, cash equivalents and restricted cash and cash equivalents	85,508	55,895
Cash, cash equivalents and restricted cash and cash equivalents at beginning of period	451,487	122,816
Cash, cash equivalents and restricted cash and cash equivalents at end of period	536,995	178,711
NONCASH INVESTING AND FINANCING ACTIVITIES:
Property and equipment purchases included in accounts payable and accrued liabilities	378	521
Reclassification of derivative liability to additional paid-in capital		29,245
RECONCILIATION OF CASH, CASH EQUIVALENTS AND RESTRICTED CASH TO THE CONDENSED CONSOLIDATED BALANCE SHEETS:
Cash and cash equivalents	521,396	168,418
Restricted cash and cash equivalents, current	8,601	9,101
Restricted cash and cash equivalents, noncurrent	6,998	1,192
Cash, cash equivalents and restricted cash and cash equivalents at end of period	536,995	$ 178,711
Collaboration Agreement
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common stock	$ 85,213