CONDENSED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 18,317	$ 39,058
Restricted cash	0	13,938
Receivables	4	4
Prepaid expenses and other current assets	457	799
Total current assets	18,778	53,799
Property and equipment, net	7,214	8,460
Right of use assets	1,434	2,136
Deposits	1	42
Other assets, non-current	500	500
Total assets	27,927	64,937
Current liabilities:
Accounts payable	1,479	1,389
Long-term debt, current	0	16,765
Accrued expenses	3,234	5,454
Lease liabilities, current	339	558
Total current liabilities	5,052	24,166
Lease liabilities, non-current	1,225	2,188
Other liabilities, non-current	0	28
Total liabilities	6,277	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 June 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	920,857	918,942
Accumulated deficit	(899,448)	(880,627)
Total stockholders' equity	21,650	38,555
Total liabilities and stockholders' equity	$ 27,927	$ 64,937