CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Cash flows from operating activities:
Net loss	$ (43,177)	$ (38,314)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	2,981	3,055
Depreciation and amortization expense	265	235
Non-cash lease expense	734	672
Accretion of debt discount	397	364
Other	(294)	19
Changes in operating assets and liabilities:
Prepaid expenses, other current assets and research and development incentive receivable	821	(1,888)
Accounts payable	(605)	(592)
Accrued expenses	651	(853)
Lease liabilities	(476)	(280)
Operating lease right-of-use asset, net of non-cash portion	0	59
Net cash used in operating activities	(38,703)	(37,641)
Cash flows from investing activities:
Acquisition of property, equipment and intangible assets	(60)	(582)
Net cash used in investing activities	(60)	(582)
Cash flows from financing activities:
Proceeds from exercise of stock options and pre-funded warrants and issuance of shares of common stock under employee stock purchase plan	70	157
Employee taxes paid related to net share settlement of vested restricted stock units	(12)	0
Proceeds from borrowings under loan and security agreements, net of issuance costs	(439)	0
Repayments of Secured Debt	(795)	0
Proceeds from sale of shares of common stock, redeemable common stock and pre-funded warrants, net of issuance costs	5,785	53,960
Net cash provided by financing activities	4,609	54,117
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(271)	(103)
Net (decrease) increase in cash, cash equivalents and restricted cash	(34,425)	15,791
Cash, cash equivalents and restricted cash at beginning of period	83,108	80,702
Cash, cash equivalents and restricted cash at end of period	48,683	96,493
Supplemental disclosure of non-cash investing and financing activities:
Acquisition of property, equipment and right-of-use assets included in accounts payable and accrued expenses	0	0
Acquisition of right-of-use asset financed by lease liabilities	0	1,343
Issuance costs not yet paid related to sale of shares of common stock, redeemable common stock and pre-funded warrants	$ 101	$ 2,442