Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Cash flows from operating activities:
Net loss	$ (20,875)	$ (25,507)
Adjustment to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	2,671	3,375
Depreciation expense	122	125
Amortization of premium on investments	109	232
Noncash rent expense	690	686
Loss on sale of property and equipment	37	0
Changes in current assets and liabilities:
Prepaid expenses and other current assets	383	(2,648)
Other non-current assets	0	6
Accounts payable	1,169	(2,224)
Accrued expenses and other current liabilities	(3,583)	(1,958)
Non-current operating lease liabilities	(754)	(687)
Net cash used in operating activities	(20,031)	(28,600)
Cash flows from investing activities:
Purchases of equipment	0	(7)
Proceeds from sales and maturities of investments	24,806	37,240
Purchases of investments	0	(20,504)
Net cash provided by investing activities	24,806	16,729
Cash flows from financing activities:
Proceeds from exercise of common stock options and ESPP	51	153
Net cash provided by financing activities	51	153
Net increase (decrease) in cash and cash equivalents	4,826	(11,718)
Cash, cash equivalents and restricted cash, beginning of period	35,483	67,022
Cash, cash equivalents and restricted cash, end of period	40,309	55,304
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents
Cash and cash equivalents, end of period	39,141	54,081
Restricted cash	1,168	1,223
Cash, cash equivalents and restricted cash, end of period	40,309	55,304
Supplemental disclosure of non-cash investing and financing activities:
Sale of equipment included in prepaid expenses and other current assets	95	0
Right-of-use assets obtained in exchange for operating lease obligation	$ 0	$ 115