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	$ (16,024)	$ (12,994)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	417	372
Stock-based compensation	3,104	1,928
Amortization of premiums and discounts on marketable securities	339	514
Amortization of debt discount and issuance costs and other non-cash interest	53	0
Changes in operating assets and liabilities
Prepaid expenses, other current assets and other long-term assets	(86)	980
Accounts payable, accrued and other current liabilities	(834)	1,088
Operating lease liabilities	(283)	(245)
Net cash used in operating activities	(13,314)	(8,357)
Cash flows from investing activities:
Purchases of property and equipment	(450)	0
Purchases of marketable securities	(74,522)	(26,187)
Maturities of marketable securities	15,439	25,500
Net cash provided by (used in) investing activities	(59,533)	(687)
Cash flows from financing activities:
Proceeds from issuance of common stock and warrants, net of issuance costs	48,642	10,673
Proceeds from issuance of common stock under employee stock incentive plans	206	62
Net cash provided by financing activities	48,848	10,735
Effect of exchange rate changes on cash and cash equivalents	25	(11)
Net increase (decrease) in cash and cash equivalents	(23,974)	1,680
Cash and cash equivalents at the beginning of period	62,882	21,228
Cash and cash equivalents at the end of period	38,908	22,908
Supplemental disclosures of noncash investing and financing information:
Reclassification of employee stock liability to equity upon vesting	0	7
Unpaid offering costs in accrued liabilities	0	25
Supplemental Cash Flow Information [Abstract]
Cash paid for interest	$ 201	$ 0