CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 119,097	$ 70,436
Accounts receivable	2,803	1,706
Prepaid expenses and other current assets	5,773	3,579
Total current assets	127,673	75,721
Property and equipment, net	20,373	22,046
Operating lease right-of-use assets	3,861	3,934
Other non-current assets	3,123	3,309
Total assets	155,030	105,010
Current liabilities:
Accounts payable	2,310	1,787
Accrued expenses and other current liabilities	16,082	7,731
Deferred revenues, current portion	25,536	12,627
Total current liabilities	43,928	22,145
Deferred revenue, net of current portion	49,421	35,900
Operating lease liabilities	14,960	15,932
Other long-term liabilities	0	6
Total liabilities	108,309	73,983
Stockholders’ equity:
Preferred stock	0	0
Common stock	67	56
Additional paid-in capital	277,496	242,672
Accumulated other comprehensive loss	234	(295)
Accumulated deficit	(231,076)	(211,406)
Total stockholders’ equity	46,721	31,027
Total liabilities and stockholders’ equity	$ 155,030	$ 105,010