Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 78,679	$ 88,539
Marketable securities	10,535	12,108
Other receivables	639	1,028
Prepaid expenses and other current assets	3,328	2,277
Total current assets	93,181	103,952
Property and equipment, net	418	455
Facility and equipment under lease	2,107	2,505
Other assets	4,348	4,636
Total assets	100,054	111,548
Current liabilities:
Accounts payable and other accrued liabilities	32,575	41,258
Accrued payroll and benefits	6,633	11,971
Total current liabilities	39,208	53,229
Other long-term liabilities	5,590	10,766
Total liabilities	44,798	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; 178,827,485 and 164,502,013 issued and outstanding at March 31, 2022 and December 31, 2021, respectively	179	165
Additional paid-in capital	1,117,350	1,094,353
Accumulated other comprehensive loss	(2,908)	(3,042)
Accumulated deficit	(1,059,365)	(1,043,923)
Total stockholders’ equity	55,256	47,553
Total liabilities and stockholders’ equity	$ 100,054	$ 111,548