CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Current assets
Cash and cash equivalents	$ 51,174	$ 45,627
Marketable securities - short-term	71,826	101,000
Accounts receivable from collaborations	524	336
Prepaid expenses and other current assets	7,253	7,241
Total current assets	130,777	154,204
Marketable securities - long-term	23,459	27,972
Property and equipment, net	1,019	1,139
Operating lease right-of-use (ROU) assets	5,300	6,042
Other assets	2,175	1,703
Total assets	162,730	191,060
Current liabilities
Accounts payable	1,407	2,659
Accrued research and development expenses	3,596	3,400
Other accrued expenses	2,499	6,863
Operating lease liabilities - short-term	3,207	3,151
Total current liabilities	10,709	16,073
Deferred revenue	2,733	2,733
Operating lease liabilities - long-term	2,497	3,325
Total liabilities	15,939	22,131
Commitments and contingencies
Stockholders' equity
Preferred stock, $0.001 par value; 5,000,000 shares authorized; no shares issued or outstanding
Common stock, $0.001 par value; 100,000,000 shares authorized as of March 31, 2022 and December 31, 2021; 48,132,937 and 48,120,437 shares issued and outstanding as of March 31, 2022 and December 31, 2021, respectively	48	48
Additional paid-in capital	802,170	800,728
Accumulated other comprehensive loss	(908)	(419)
Accumulated deficit	(654,519)	(631,428)
Total stockholders' equity	146,791	168,929
Total liabilities and stockholders' equity	$ 162,730	$ 191,060