CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Cash flows from operating activities
Net loss	$ (8,297)	$ (11,580)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	87	137
Accretion related to marketable securities	55	95
Stock-based compensation	739	1,225
Loss from equity method investment	1,041	100
Changes in operating assets and liabilities:
Accounts receivable - related party	134
Prepaid and other current assets	304	237
Operating lease right-of-use asset	238	193
Other assets		(664)
Accounts payable	624	1,443
Accrued and other liabilities	(1,095)	287
Operating lease liability	(254)	(260)
Net cash used in operating activities	(6,424)	(8,787)
Cash flows from investing activities
Purchases of marketable securities	(26,384)	(3,321)
Maturities of marketable securities	810	8,167
Net cash provided by (used in) investing activities	(25,574)	4,846
Cash flows from financing activities
Proceeds from issuance of common stock, net (includes $4,850 in aggregate gross proceeds from related parties for the three months ended March 31, 2021)		31,989
Proceeds from issuance of common stock in connection with at-the-market offering, net		601
Net cash provided by financing activities		32,590
Net increase (decrease) in cash and cash equivalents	(31,998)	28,649
Cash and cash equivalents at beginning of the period	63,458	16,455
Cash and cash equivalents at end of the period	$ 31,460	$ 45,104