Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Cash flows from operating activities
Net income	$ 96,652	$ 214,521
Adjustments to reconcile net income to net cash (used in) provided by operating activities:
Depreciation and amortization	803	603
Stock-based compensation	21,561	13,794
Amortization/accretion of available-for-sale debt securities	(1,728)	0
Change in operating lease right of use assets	10	12
Changes in operating assets and liabilities:
Grants receivable	2,751	(4,071)
Research and development tax credits receivable	1,237	727
Refundable income taxes	6,107	(7,544)
Prepaid expenses and other current assets	590	(11,789)
Accounts payable	2,761	2,280
Accrued expenses and other liabilities	3,096	9,959
Deferred income	397	(3,480)
Deferred revenue	(267,630)	281,128
Unrecognized tax benefits	22,200	17,000
Net cash (used in) provided by operating activities	(111,193)	513,140
Cash flows from investing activities
Purchases of investments	(445,004)
Purchase of property and equipment	(938)	(1,181)
Purchase of other assets	(120)	(61)
Net cash used in investing activities	(446,062)	(1,242)
Cash flows from financing activities
Proceeds from issuance of common stock upon exercise of options and ESPP purchase	925	2,943
Proceeds from grants repayable	1,059	716
Net cash provided by financing activities	1,984	3,659
Effects of exchange rate changes on cash, cash equivalents and restricted cash	(8,526)	(3,176)
Net (decrease) increase in cash, cash equivalents and restricted cash	(563,797)	512,381
Cash, cash equivalents and restricted cash at beginning of year	848,835	336,454
Cash, cash equivalents and restricted cash at end of year	285,038	848,835
Non-cash investing and financing activities
Capital expenditure included in accounts payable	94	175
Operating lease liabilities arising from obtaining right-of-use assets (non-cash)	350	5,877
Unrealized loss on available-for-sale securities	148
Supplemental disclosure of cash flows
Cash paid for taxes	$ 22,816	$ 32,019