Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
CASH FLOWS FROM OPERATING ACTIVITIES
Net loss	$ (30,094,000)	$ (26,960,000)
Adjustments to reconcile net loss to net cash used in operating activities
Stock-based compensation	4,621,000	6,788,000
Impairment charge on investment in equity securities	2,990,000	0
Depreciation	23,000	8,000
Disposal of assets	0	3,000
Changes in operating assets and liabilities:
Prepaid materials	2,544,000	(2,953,000)
Research and development tax rebate receivable	743,000	329,000
Prepaid expenses and other current assets	261,000	180,000
Other assets	(1,697,000)	(597,000)
Accounts payable	(2,159,000)	1,248,000
Accrued expenses	(86,000)	855,000
Payroll liabilities	129,000	341,000
Other current liabilities	1,784,000	(2,000)
Net cash used in operating activities	(20,941,000)	(20,760,000)
CASH FLOWS FROM INVESTING ACTIVITIES
Purchase of investment in equity securities	0	(4,700,000)
Purchase of property and equipment	(14,000)	(27,000)
Net cash used in investing activities	(14,000)	(4,727,000)
CASH FLOWS FROM FINANCING ACTIVITIES
Common stock repurchased	(1,475,000)	0
Net cash used in financing activities	(1,475,000)	0
NET DECREASE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	(22,430,000)	(25,487,000)
CASH, CASH EQUIVALENTS AND RESTRICTED CASH, BEGINNING BALANCE	111,000,000	136,487,000
CASH, CASH EQUIVALENTS AND RESTRICTED CASH, ENDING BALANCE	88,570,000	111,000,000
RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH
Cash and cash equivalents	88,460,000	110,890,000
Restricted cash	110,000	110,000
Total cash, cash equivalents and restricted cash	$ 88,570,000	$ 111,000,000