Condensed Consolidated Statements of Cash Flows (Unaudited) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2022 USD ($)	Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)
Cash flows from operating activities:
Consolidated net loss	$ (12,421)	$ (24,575)	$ (17,547)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization		144	244
Stock-based compensation	517	934	758
Amortization of premium of available-for-sale investment securities		434	106
Amortization of right-of-use assets		440	411
Gain on disposal of property and equipment		(89)
Changes in operating assets and liabilities:
Other receivables		9	1,949
Prepaid expenses and other assets		831	(405)
Accounts payable and accrued expenses		3,108	1,379
Operating lease liability		(472)	(414)
Net cash used in operating activities		(19,236)	(13,519)
Cash flows from investing activities:
Purchases of property and equipment		(96)	(113)
Purchases of available-for-sale investment securities		(11,176)	(40,024)
Maturities of available-for-sale investment securities		35,700	12,768
Proceeds from sale of property and equipment		169
Net cash provided by (used in) investing activities		24,597	(27,369)
Cash flows from financing activities:
Proceeds from issuance of common stock through option exercises		1	1
Proceeds from issuance of common stock through employee stock purchase plan		5	5
Proceeds from issuance of common stock from at-the-market offerings, net of offering costs		1,514	10,886
Proceeds from issuance of common stock from committed purchase agreement, net of offering costs			15,236
Net cash provided by financing activities		1,520	26,128
Net change in cash, cash equivalents and restricted cash		6,881	(14,760)
Cash, cash equivalents and restricted cash at beginning of period		2,336	16,952
Cash, cash equivalents and restricted cash at the end of period	9,217	9,217	2,192
Cash and cash equivalents at the end of period	8,484	8,484	2,192
Restricted cash at the end of period	733	733
Cash, cash equivalents and restricted cash at the end of period	$ 9,217	9,217	$ 2,192
Supplemental schedule of noncash investing and financing activities:
Purchases of property and equipment in accounts payable		143
Right-of-use assets obtained in exchange for lease obligation		$ 368