Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Cash flows from operating activities:
Net loss	$ (9,705,000)	$ (7,722,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Share-based compensation	3,439,000	5,031,000
Depreciation and amortization expense	105,000	1,472,000
Change in fair value of warrant and private placement derivative liabilities	(15,126,000)	(46,130,000)
(Gain) loss on dispositions, net	478,000	(3,656,000)
Amortization of right-of-use assets	33,000	402,000
Accretion of lease liability	23,000	414,000
Impairment of property and equipment	0	1,265,000
Amortization of deferred issuance costs	0	550,000
Gain on debt extinguishment	0	(112,000)
Changes in operating assets and liabilities:
Accounts receivable, interest and other receivables	170,000	301,000
Prepaid expenses and other assets	(462,000)	563,000
Accounts payable	(801,000)	(1,917,000)
Accrued liabilities and other	(1,260,000)	(7,111,000)
Net cash used in operating activities	(23,106,000)	(56,650,000)
Cash flows from investing activities:
Proceeds from sale of property and equipment	900,000	14,705,000
Purchases of property and equipment	(7,000)	(625,000)
Cash provided by investing activities	893,000	14,080,000
Cash flows from financing activities:
Payment on debt	0	(37,155,000)
Proceeds from exercise of stock options	0	12,000
Proceeds from issuance of stock from employee stock purchase plan	0	78,000
Proceeds from issuance of pre-funded warrants, net	32,908,000	22,901,000
Payment on financing lease obligations	(35,000)	(74,000)
Net cash provided by (used in) financing activities	32,873,000	(14,238,000)
Effect of exchange rate changes on cash	1,000	(12,000)
Net change in cash, cash equivalents and restricted cash	10,661,000	(56,820,000)
Cash, cash equivalents and restricted cash at beginning of period	36,996,000	93,816,000
Cash, cash equivalents and restricted cash at end of period	47,657,000	36,996,000
Supplemental cash flow information:
Cash paid during the period for interest	0	2,340,000
Non-cash investing and financing activities:
Conversion of redeemable preferred stock into common stock	0	3,432,000
Reclassification of property and equipment, net to assets held for sale	0	2,300,000
Leasehold improvements paid by landlord	$ 0	$ 113,000