CONDENSED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 27,993	$ 32,545
Prepaid expenses and other current assets	1,369	1,493
Total current assets	29,362	34,038
Property and equipment, net	18	22
Operating lease right-of-use assets	683	734
Other assets	70	70
Total assets	30,133	34,864
Current liabilities:
Accounts payable	240	565
Accrued expenses	3,342	4,088
Operating lease liability	214	209
Total current liabilities	3,796	4,862
Operating lease liability, net of current portion	494	549
Total liabilities	4,290	5,411
Commitments and contingencies (Note 12)
Stockholders' equity (deficit):
Common stock, $0.001 par value, Authorized - 140,000 shares; Issued and outstanding - 52,924 and 52,818 at March 31, 2022 and December 31, 2021, respectively	53	53
Additional paid-in capital	765,429	764,861
Accumulated deficit	(739,639)	(735,461)
Total stockholders' equity (deficit)	25,843	29,453
Total liabilities and stockholders' equity (deficit)	30,133	34,864
Series A Preferred Stock [Member]
Stockholders' equity (deficit):
Preferred stock