Unaudited Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Cash flows used in operating activities:
Net loss	$ (10,755)	$ (13,465)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	1,879	2,740
Operating lease right-of-use asset	341	55
Depreciation	56	32
Amortization of premium on marketable debt securities	410	283
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(1,186)	(1,971)
Other assets	78	65
Accounts payable	(413)	938
Accrued expenses	(1,039)	(545)
Operating lease liabilities	(332)	(52)
Net cash used in operating activities	(10,961)	(11,920)
Cash flows from investing activities:
Purchase of marketable debt securities	(12,415)	(97,959)
Proceeds from maturity and redemption of marketable debt securities	13,171
Purchase of property and equipment	(11)	(290)
Net cash provided by/(used in) investing activities	745	(98,249)
Cash flows from financing activities:
Repurchase of shares in connection with settlement of RSUs	(72)	(228)
Net cash used in financing activities	(72)	(228)
Net decrease in cash and cash equivalents and restricted cash	(10,288)	(110,397)
Cash and cash equivalents and restricted cash - beginning of year	36,469	169,393
Cash and cash equivalents and restricted cash - end of period	26,181	58,996
Reconciliation of cash and cash equivalents and restricted cash to the condensed consolidated balance sheets:
Cash and cash equivalents	25,436	58,201
Restricted cash		50
Restricted cash, non-current	745	745
Cash and cash equivalents and restricted cash	$ 26,181	$ 58,996