Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Cash flows from operating activities:
Net loss	$ (7,562)	$ (11,267)
Adjustments to reconcile net loss to net cash used in operating activities:
Share-based compensation	599	903
Depreciation and amortization expense	5	47
Change in fair value of warrant derivative and private placement option liabilities	1,637	2,337
Amortization of right-of-use assets	0	33
Accretion of lease liability	0	31
Loss on dispositions, net	0	464
Changes in operating assets and liabilities:
Accounts receivable, interest and other receivables	(2)	0
Prepaid expenses and other assets	(674)	(679)
Accounts payable	122	(222)
Accrued liabilities and other	(502)	60
Net cash used in operating activities	(6,377)	(8,293)
Cash flows from investing activities:
Proceeds from sale of property and equipment	0	900
Purchases of property and equipment	(7)	0
Net cash (used in) provided by investing activities	(7)	900
Cash flows from financing activities:
Payment on financing lease obligations	0	(20)
Net cash used in financing activities	0	(20)
Effect of exchange rate changes on cash	(3)	0
Net change in cash, cash equivalents, and restricted cash	(6,387)	(7,413)
Cash, cash equivalents and restricted cash at beginning of period	47,657	36,996
Cash, cash equivalents and restricted cash at end of period	$ 41,270	$ 29,583