Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 123,665	$ 117,358
Marketable securities	203,235	188,451
Restricted cash - current		10
Receivable from collaboration partner and contract asset - related party	1,566	2,426
Research and development tax incentive receivable	2,792	1,084
Prepaid expenses and other current assets	9,478	6,277
Total current assets	340,736	315,606
Marketable securities - noncurrent		2,000
Property and equipment, net	1,798	1,462
Restricted cash - noncurrent	225	450
Operating lease right-of-use asset	4,936	4,950
Total assets	347,695	324,468
Current liabilities:
Accounts payable	1,600	3,075
Payable to collaboration partner - related party	899	2,732
Accrued expenses and other payables	37,716	18,498
Deferred revenue - related party	1,601	14,477
Operating lease liability - current	2,200	1,459
Total current liabilities	44,016	40,241
Operating lease liability - noncurrent	3,658	4,500
Other liabilities		121
Total liabilities	47,674	44,862
Commitments and contingencies
Stockholders' equity:
Preferred stock, $0.00001 par value, 10,000,000 shares authorized; no shares issued and outstanding
Common stock, $0.00001 par value, 90,000,000 shares authorized; 47,838,330 and 43,745,465 shares issued and outstanding as of December 31, 2021 and 2020, respectively
Additional paid-in capital	709,682	563,389
Accumulated other comprehensive (loss) gain	(299)	28
Accumulated deficit	(409,362)	(283,811)
Total stockholders' equity	300,021	279,606
Total liabilities and stockholders' equity	$ 347,695	$ 324,468