Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 25,512	$ 88,539
Marketable securities	42,447	12,108
Other receivables	608	1,028
Prepaid expenses and other current assets	5,012	2,277
Total current assets	73,579	103,952
Property and equipment, net	347	455
Facility and equipment under lease	1,703	2,505
Other assets	3,800	4,636
Total assets	79,429	111,548
Current liabilities:
Accounts payable and other accrued liabilities	33,123	41,258
Accrued payroll and benefits	7,918	11,971
Total current liabilities	41,041	53,229
Other long-term liabilities	4,946	10,766
Total liabilities	45,987	63,995
Commitments and contingencies (Note 6)
Stockholders’ equity:
Preferred stock, $0.001 par value; 5,000,000 shares authorized; no shares issued and outstanding	0	0
Common stock, $0.001 par value; 300,000,000 shares authorized; 184,870,273 and 164,502,013 issued and outstanding at June 30, 2022 and December 31, 2021, respectively	185	165
Additional paid-in capital	1,124,625	1,094,353
Accumulated other comprehensive loss	(2,955)	(3,042)
Accumulated deficit	(1,088,413)	(1,043,923)
Total stockholders’ equity	33,442	47,553
Total liabilities and stockholders’ equity	$ 79,429	$ 111,548