Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 22,431	$ 66,923
Marketable securities	17,961
Inventories	785	2,352
Prepaid expenses and other current assets	1,363	1,448
Total current assets	42,540	70,723
Restricted cash	2,557	1,311
Property and equipment, net	1,570	1,841
Right-of-use lease asset	4,352	4,706
Other assets		1,543
Total assets	51,019	80,124
Current liabilities:
Accounts payable, net	1,416	4,547
Accrued expenses and other current liabilities	6,794	3,847
Current portion of loans payable, net	174
Lease liability	873	792
Total current liabilities	9,257	9,186
Loans payable, net	13,359
Leases, net of current portion	5,672	6,309
Warrant liability	868
Total liabilities	29,156	15,495
Commitments and contingencies (Note 9)
Stockholders' equity:
Preferred stock-$0.001 par value; 5,000,000 shares authorized, none issued or outstanding at September 30, 2022 and December 31, 2021
Common stock-$0.001 par value; 200,000,000 shares authorized at September 30, 2022 and December 31, 2021; 173,686,168 and 165,520,007 shares issued and outstanding at September 30, 2022 and December 31, 2021, respectively	173	165
Additional paid-in capital	562,485	558,566
Accumulated deficit	(540,767)	(494,102)
Accumulated other comprehensive loss	(28)
Total stockholders' equity	21,863	64,629
Total liabilities and stockholders' equity	$ 51,019	$ 80,124