Condensed Consolidated Balance Sheets (unaudited) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 823,984	$ 848,537
Grants receivable	4,619	4,022
Research and development tax credits receivable	0	524
Refundable income taxes	0	7,544
Prepaid expenses and other current assets	12,057	14,086
Total current assets	840,660	874,713
Property and equipment, net	2,216	2,072
Research and development tax credits receivable, net of current portion	1,599	2,004
Restricted cash	296	298
Right of use assets	5,234	5,329
Other assets	316	296
Total assets	850,321	884,712
Current liabilities:
Accounts payable	10,603	5,145
Accrued expenses and other current liabilities	14,052	17,157
Income tax payable	20,107
Deferred income	1,002	827
Deferred revenue	127,703	280,225
Lease liabilities	786	770
Total current liabilities	174,253	304,124
Grants repayable	5,899	6,164
Lease liabilities, net of current portion	4,461	4,571
Unrecognized tax benefits	39,300	17,000
Other noncurrent liabilities	30	33
Total liabilities	223,943	331,892
Commitments and contingencies (Note 10)
Stockholders’ equity:
Preferred stock, $0.001 par value; 10,000,000 and zero shares authorized at March 31, 2022 and December 31, 2021, respectively, and zero shares issued or outstanding	0	0
Common stock, $0.001 par value: 150,000,000 shares authorized at March 31, 2022 and December 31, 2021 respectively; 35,516,912 and 35,466,001 shares issued and outstanding; respectively	36	35
Additional paid-in capital	417,705	413,180
Accumulated other comprehensive loss	(1,568)	(1,018)
Retained earnings	210,205	140,623
Total stockholders’ equity	626,378	552,820
Total liabilities and stockholders’ equity	$ 850,321	$ 884,712