Unaudited Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Operating activities:
Net loss	$ (12,880)	$ (14,768)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	68	79
Stock-based compensation	2,010	1,520
Non-cash interest expense	122	62
Amortization of premiums/discounts on investments, net	1	170
Amortization of right-of-use asset	179	164
Gain from lease termination and asset sale	(508)
Changes in operating assets and liabilities
Prepaid expenses and other current assets	(1,034)	(410)
Accounts payable and accrued liabilities	(1,461)	1,189
Lease liability	(196)	(176)
Net cash used in operating activities	(13,699)	(12,170)
Investing activities:
Purchases of short-term investments	(12,676)	(12,784)
Sales and maturities of short-term investments	10,500	19,395
Net cash (used in) provided by investing activities	(2,176)	6,611
Financing activities:
Proceeds from exercise of common stock options		623
Net cash provided by financing activities		623
Net decrease in cash and cash equivalents	(15,875)	(4,936)
Cash and cash equivalents at beginning of period	48,910	24,393
Cash and cash equivalents at end of period	33,035	19,457
Supplemental disclosure of cash flow information:
Cash paid for interest	291	181
Receivable from asset sale	700
Supplemental non-cash investing and financing activities:
Vesting of common stock	$ 3	$ 8