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	$ (14,498)	$ (13,275)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	42	23
Net accretion of discounts/premiums on debt securities	36	0
Stock-based compensation	2,054	522
Loss on investment in joint venture	390	482
Changes in operating assets and liabilities:
Prepaid expenses, right-of-use assets and other assets	(794)	61
Accounts payable	447	1,430
Accrued expenses and operating lease liability	(1,408)	(1,172)
Net cash used in operating activities	(13,731)	(11,929)
Cash Flows used in Investing Activities:
Purchases of marketable securities	80,142	0
Purchase of property and equipment	(36)	(62)
Investment in joint venture	0	(500)
Net cash used in investing activities	(80,178)	(562)
Cash Flows from Financing Activities:
Net cash provided by financing activities	0	0
Net decrease in cash and cash equivalents	(93,909)	(12,491)
Cash and cash equivalents - beginning of period	175,334	140,233
Cash and cash equivalents - end of period	81,425	127,742
Supplemental Disclosures of Noncash Investing and Financing Activities:
Property and equipment in accounts payable	$ 8	$ 0