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	$ (21,965)	$ (18,676)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	1,459	1,258
Depreciation and amortization expense	133	106
Non-cash lease expense	366	314
Accretion of debt discount	198	178
Other	(120)	99
Changes in operating assets and liabilities:
Prepaid expenses, other current assets and research and development incentive receivable	1,633	(711)
Accounts payable	(713)	(23)
Accrued expenses	(984)	(786)
Lease liabilities	(236)	(160)
Operating lease right-of-use asset, net of non-cash portion	0	43
Net cash used in operating activities	(20,229)	(18,444)
Cash flows from investing activities:
Acquisition of property, equipment and intangible assets	(22)	(496)
Net cash used in investing activities	(22)	(496)
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	0	41
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	(114)	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	5,877	55,000
Net cash provided by financing activities	4,956	55,041
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(69)	(143)
Net (decrease) increase in cash, cash equivalents and restricted cash	(15,364)	35,958
Cash, cash equivalents and restricted cash at beginning of period	83,108	80,702
Cash, cash equivalents and restricted cash at end of period	67,744	116,660
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	17
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	$ 0	$ 3,485