CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Operating activities
Net loss	$ (10,177)	$ (12,405)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	1,213	1,515
Depreciation and amortization	161	157
Accretion on marketable securities	(348)	197
Non-cash lease expense	316	291
Amortization of financing lease right-of-use assets	197	177
Realized gain on marketable securities		(15)
Loss on fixed asset disposition	105
Gain on fixed asset disposition	(9)
Changes in operating assets and liabilities:
Prepaid expenses	(1,580)	(2,007)
Other assets	(8)	175
Accounts payable and accrued liabilities	242	2,644
Compensation and employee benefits	(1,577)	(1,193)
Operating lease liabilities	(307)	(271)
Other liabilities	36	(15)
Net cash used in operating activities	(11,736)	(10,750)
Investing activities
Purchases of property and equipment	(151)	(19)
Purchases of short-term investments	(9,846)	(8,017)
Sales of short-term investments		12,365
Maturities of short-term investments	12,300	7,864
Proceeds from sale of property and equipment	9
Net cash provided by investing activities	2,312	12,193
Financing activities
Principle payments for financing leases	(186)	(133)
Proceeds from the exercise of common stock options		238
Payment of employee restricted stock tax withholdings	(76)
Employee stock purchase plan proceeds		14
Net cash (used in) provided by financing activities	(262)	119
Net (decrease) increase in cash and cash equivalents	(9,686)	1,562
Cash and cash equivalents at beginning of period	17,795	7,159
Cash and cash equivalents at end of period	8,109	8,721
Supplemental disclosure of noncash financing information:
Property and equipment additions included in accounts payable and accrued liabilities		11
Property and equipment disposals included in other assets	(120)
Issuance of equity in exchange for compensation included in compensation and employee benefits	302
Initial measurement of operating lease right-of-use assets	258	6,558
Initial measurement of operating lease liabilities	$ 258	5,580
Initial measurement of finance lease right-of-use assets		$ 411