Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands		6 Months Ended
		Jun. 30, 2022	Jun. 30, 2021
Cash flows from operating activities:
Net loss		$ (17,464)	$ (21,158)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization		16	94
Amortization of right-of-use assets		66	116
Foreign currency (gain) loss		(29)	15
Amortization of debt issuance costs		198	277
Amortization on premium to short-term investments		371	668
Stock-based compensation		1,030	1,717
Changes in operating assets and liabilities:
Prepaid expenses and other current assets		1,337	(170)
Non-current assets		(803)	(890)
Accounts payable and accrued expenses and other current liabilities		(2,463)	(2,413)
Long-term liabilities			(47)
Net cash used in operating activities		(17,741)	(21,791)
Cash flows from investing activities:
Purchase of property and equipment		(5)	(6)
Purchase of available-for-sale securities, net		(16,004)	(114,445)
Maturities of available-for-sale securities		83,593	33,280
Sale of available-for-sale securities, net		11,276
Net cash provided by (used in) investing activities		78,860	(81,171)
Cash flows from financing activities:
Repurchase of outstanding pre-funded warrants			(3,909)
Repayment of long-term debt		(26,350)
Proceeds from long-term debt, net	[1]	26,438
Issuance of common stock and pre-funded warrants in public offering, net of offering costs			122,148
Proceeds from exercise of stock options			5
Issuance of common stock upon exercise of warrants, net			2,546
Repurchase of shares for minimum tax withholdings		(1)
Net cash provided by financing activities		87	120,790
Effect of exchange rate changes on cash and cash equivalents		(65)	(55)
Increase in cash and cash equivalents		61,141	17,773
Cash and cash equivalents beginning of period		34,012	22,880
Cash and cash equivalents end of period		95,153	40,653
Supplemental disclosure of cash flow information:
Cash paid for interest		$ 857	$ 974

[1] As discussed in Note 6. Long-term Debt, the Amended Loan Agreement (as defined herein) was accounted for as a modification. The Company used the proceeds from the Amended Loan Agreement to repay the outstanding amounts under the Loan Agreement from Silicon Valley Bank.