CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($)	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Cash flows from operating activities
Net loss	$ (7,731,000)	$ (7,102,000)
Adjustments to reconcile net loss to cash used in operating activities
Depreciation expense	9,000	8,000
Amortization expense - right-of-use leased assets - operating	93,000	98,000
Accretion expense	4,000	79,000
Stock-based compensation	636,000	521,000
Non-cash interest expense	114,000	127,000
Changes in operating assets and liabilities
Prepaid expenses and other assets	187,000	(119,000)
Accounts payable, accrued expenses and other liabilities	(681,000)	(2,227,000)
Net cash used in operating activities	(7,369,000)	(8,615,000)
Cash flows from investing activities
Purchases of property and equipment	(6,000)
Maturities of short-term investments		16,700,000
Purchases of short-term investments	(12,784,000)	(3,995,000)
Net cash provided by (used in) investing activities	(12,790,000)	12,705,000
Cash flows from financing activities
Principal payments on term loan	(2,500,000)
Proceeds from the exercise of vested stock options	21,000	9,000
Settlements of restricted stock units for tax withholding obligations		(81,000)
Net cash used in financing activities	(2,479,000)	(72,000)
Net increase (decrease) in cash, cash equivalents and restricted cash	(22,638,000)	4,018,000
Cash, cash equivalents and restricted cash at beginning of period	74,450,000	72,001,000
Cash, cash equivalents and restricted cash at end of period	51,812,000	76,019,000
Supplemental cash flow information
Interest paid	425,000	597,000
Taxes paid	$ 36,000	$ 42,000