UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Cash flows from operating activities:
Net loss	$ (6,230)	$ (11,620)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	597	922
Depreciation	15	21
Amortization of operating lease right-of-use asset	171	177
Amortization of debt discount	120	124
Change in fair value of derivative liabilities	13	270
Loss on extinguishment of debt	406	0
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(577)	(1,169)
Accounts payable	(586)	1,525
Accrued expenses	(569)	434
Operating lease liabilities	(174)	(175)
Net cash used in operating activities	(6,814)	(9,491)
Cash flows from investing activities:
Proceeds from sale of property and equipment	11	0
Purchases of property and equipment	0	(11)
Net cash (used in) provided by investing activities	11	(11)
Cash flows from financing activities:
Repayment of term loan principal	(7,500)	0
Proceeds from advances from collaboration partners	0	7,000
Net cash (used in) provided by financing activities	(7,500)	7,000
Decrease in cash, cash equivalents and restricted cash	(14,303)	(2,502)
Cash, cash equivalents and restricted cash at the beginning of the period	19,468	42,567
Cash, cash equivalents and restricted cash at the end of the period	5,165	40,065
Reconciliation of cash, cash equivalents and restricted cash to condensed consolidated balance sheets:
Cash and cash equivalents	4,904	39,768
Restricted cash	261	297
Total cash, cash equivalents and restricted cash	5,165	40,065
Supplemental disclosure of cash flow activities:
Cash paid for interest	$ 430	$ 297