Condensed Consolidated Balance Sheets (unaudited) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 31,208	$ 47,076
Prepaid expenses and other current assets	3,326	3,126
Total current assets	34,534	50,202
Property and equipment, net	1,178	1,126
Restricted cash	210	263
Operating lease, right-of-use ("ROU") asset	4,630	0
Other assets	320	320
Total assets	40,872	51,911
Current liabilities:
Accounts payable	559	1,061
Accrued expenses	1,174	1,571
Operating lease obligations, current portion	1,049	0
Current portion of long-term debt	5,611	7,467
Total current liabilities	8,393	10,099
Long-term debt, net of current portion	0	1,867
Operating lease obligations, long-term portion	3,604	0
Total liabilities	11,997	11,966
Stockholders' equity:
Preferred stock, $0.0001 par value; 10,000 shares authorized and no shares issued and outstanding as of June 30, 2021 and December 31, 2020	0	0
Common stock, $0.0001 par value: 300,000 shares authorized; 62,323 and 52,117 shares issued at June 30, 2021 and December 31, 2020, respectively; 61,666 and 51,221 shares outstanding at June 30, 2021 and December 31, 2020, respectively	6	5
Additional paid-in-capital	243,503	191,348
Accumulated deficit	(214,634)	(151,408)
Total stockholders' equity	28,875	39,945
Total liabilities and stockholders' equity	$ 40,872	$ 51,911