CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 40,219	$ 33,406
Prepaid expenses and other current assets	3,156	2,063
Total current assets	43,375	35,469
Property and equipment, net	71	106
Right-of-use lease asset	44	1,227
Non-current deposits	1,509	0
Total assets	44,999	36,802
Current liabilities:
Accounts payable	1,515	514
Accrued and other current liabilities	2,076	1,972
Total current liabilities	3,591	2,486
Lease liability	44	1,057
Total liabilities	3,635	3,543
Stockholders' equity:
Common stock, $0.001 par value; 100,000,000 shares authorized at December 31, 2020 and September 30, 2021; 6,246,896 and 9,797,735 shares issued and outstanding at December 31, 2020 and September 30, 2021.	10	6
Additional paid-in capital	421,771	400,071
Accumulated other comprehensive loss	(753)	(746)
Accumulated deficit	(379,664)	(366,072)
Total stockholders' equity	41,364	33,259
Total liabilities and stockholders' equity	44,999	36,802
6% Convertible Exchangeable Preferred Stock [Member]
Stockholders' equity:
Preferred stock, value	0	0
Series A Convertible Preferred Stock [Member]
Stockholders' equity:
Preferred stock, value	0	0
Series B Convertible Preferred Stock [Member]
Stockholders' equity:
Preferred stock, value	$ 0	$ 0