CONDENSED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 11,944	$ 39,058
Restricted cash	0	13,938
Receivables	0	4
Prepaid expenses and other current assets	925	799
Total current assets	12,869	53,799
Property and equipment, net	5,532	8,460
Right of use assets	1,039	2,136
Deposits	0	42
Other non-current assets	0	500
Total assets	19,440	64,937
Current liabilities:
Accounts payable	1,298	1,389
Current portion of long-term debt	0	16,765
Accrued expenses	3,071	5,454
Lease liabilities, current	307	558
Total current liabilities	4,676	24,166
Lease liabilities, non-current	864	2,188
Other non-current liabilities	0	28
Total liabilities	5,540	26,382
Commitments and contingencies (Note 9)
Stockholders' equity
Common stock $0.001 par value; 520,000,000 shares authorized, 240,627,055 shares issued and outstanding at September 30, 2023 and 420,000,000 shares authorized, 240,410,761 shares issued and outstanding at December 31, 2022	241	240
Additional paid-in capital	921,583	918,942
Accumulated deficit	(907,924)	(880,627)
Total stockholders' equity	13,900	38,555
Total liabilities and stockholders' equity	$ 19,440	$ 64,937