Condensed Consolidated Balance Sheets (unaudited) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 39,695	$ 47,076
Prepaid expenses and other current assets	1,952	3,126
Total current assets	41,647	50,202
Property and equipment, net	1,188	1,126
Restricted cash	151	263
Operating lease, right-of-use asset	4,892
Other assets	320	320
Total assets	48,198	51,911
Current liabilities:
Accounts payable	1,061	1,061
Accrued expenses	1,290	1,571
Operating lease obligations, current portion	1,025
Current portion of long-term debt	7,474	7,467
Total current liabilities	10,850	10,099
Long-term debt, net of current portion		1,867
Operating lease obligations, long-term portion	3,877
Total liabilities	14,727	11,966
Commitments and contingencies (Note 11)
Stockholders' equity:
Preferred stock, $0.0001 par value; 10,000 shares authorized and no shares issued and outstanding as of March 31, 2021 and December 31, 2020
Common stock, $0.0001 par value: 300,000 shares authorized; 52,081 and 52,117 shares issued at March 31, 2021 and December 31, 2020, respectively; 51,313 and 51,221 shares outstanding at March 31, 2021 and December 31, 2020, respectively	5	5
Additional paid-in-capital	192,296	191,348
Accumulated deficit	(158,830)	(151,408)
Total stockholders' equity	33,471	39,945
Total liabilities and stockholders' equity	$ 48,198	$ 51,911