Condensed Consolidated Balance Sheets (unaudited) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 6,589	$ 29,988
Prepaid expenses and other current assets	9,897	3,018
Total current assets	16,486	33,006
Property and equipment, net	930	1,173
Operating lease assets	272	455
Other assets	123	123
Total assets	17,811	34,757
Current liabilities:
Accounts payable	2,271	1,030
Loan payable, net of discount	4,904	9,852
Accrued expenses and other current liabilities	2,870	4,480
Operating lease liabilities, net of discount	380	317
Total current liabilities	10,425	15,679
Warrant liability	3,645
Operating lease liabilities, net of current portion and discount		210
Total liabilities	14,070	15,889
Commitments and contingencies (Note 6)
Stockholders’ equity:
Undesignated preferred stock, $0.001 par value; 5,000,000 shares authorized; 2,872 shares issued and no shares outstanding at June 30, 2022; no shares issued and outstanding at December 31, 2021
Common stock, $0.001 par value; 200,000,000 shares authorized; 107,725,169 and 82,969,421 shares issued and outstanding at June 30, 2022 and December 31, 2021, respectively	108	83
Additional paid-in capital	270,333	265,237
Accumulated deficit	(266,700)	(246,452)
Total stockholders’ equity	3,741	18,868
Total liabilities and stockholders’ equity	$ 17,811	$ 34,757