CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 145,101	$ 138,509
Short-term investments		1,474
Accounts receivable	2,473	1,646
Contract asset	1,059
Prepaid expenses and other current assets	4,858	4,638
Total current assets	153,491	146,267
Property and equipment, net	2,650	1,945
Other assets	2,732	2,250
Total assets	158,873	150,462
Current liabilities:
Accounts payable	693	2,211
Refund liability	21,828
Accrued expenses	15,155	8,518
Total current liabilities	37,676	10,729
Notes payable, net of deferred financing costs	40,579
Other long-term liabilities	2,124	2,534
Total liabilities	80,379	13,263
Stockholders' equity:
Series A convertible preferred stock, $0.001 par value; 25,000,000 shares authorized, 4,575 shares issued and outstanding at September 30, 2021 and 4,753 issued and outstanding at December 31, 2020	4,302	4,469
Common stock, $0.001 par value; 150,000,000 shares authorized, 36,758,508 issued and 36,751,201 outstanding at September 30, 2021 and 36,585,767 issued and 36,578,460 outstanding at December 31, 2020	37	37
Additional paid-in capital	456,555	444,622
Treasury stock at cost, 7,307 shares at September 30, 2021 and December 31, 2020
Accumulated deficit	(382,400)	(311,929)
Total stockholders' equity	78,494	137,199
Total liabilities and stockholders' equity	$ 158,873	$ 150,462