Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Cash flows from operating activities:
Net loss	$ (25,565)	$ (14,782)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	2,512	1,793
Accretion of final payment fee	121
Amortization of premium on available-for-sale securities	118	229
Amortization of debt issuance costs	75	77
Depreciation	18	15
Changes in operating assets and liabilities:
Prepaid and other current assets	1,942	(2,726)
Other assets	72	72
Accounts payable	(2,422)	2,450
Accrued expenses	(1,215)	(2,110)
Net cash used in operating activities	(24,344)	(14,982)
Cash flows from investing activities:
Proceeds from maturities of available-for-sale securities	36,179	29,896
Purchases of available-for-sale securities	(9,401)	(45,302)
Purchases of property and equipment	(6)	(4)
Net cash provided by (used in) investing activities	26,772	(15,410)
Cash flows from financing activities:
Proceeds from issuance of common stock upon stock option exercises	29	216
Net cash provided by financing activities	29	216
Net change in cash and cash equivalents, and restricted cash	2,457	(30,176)
Cash and cash equivalents, and restricted cash at beginning of period	52,457	98,208
Cash and cash equivalents, and restricted cash at end of period	54,914	68,032
Components of cash and cash equivalents, and restricted cash:
Cash and cash equivalents	54,889	68,007
Restricted cash	25	25
Total cash and cash equivalents, and restricted cash	54,914	68,032
Supplemental disclosures of cash information:
Cash paid for interest	$ 169
Cash paid for income taxes		154
Supplemental disclosures of noncash information:
Purchases of property and equipment included in accounts payable and accrued expenses		$ 6