Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Cash flows from operating activities:
Net loss	$ (93,867)	$ (88,696)	$ (62,131)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	5,199	6,180	5,428
Depreciation and amortization expense	513	499	351
Goodwill impairment	0	9,758	0
Non-cash lease expense	1,481	1,393	879
Accretion of debt discount	918	756	532
Loss on extinguishment of debt	0	0	162
Change in fair value of warrant and derivative liability	2,881	366	437
Other	37	337	(413)
Changes in operating assets and liabilities:
Prepaid expenses, other current assets and research and development incentive receivable	(610)	(1,755)	(1,655)
Accounts payable	3,425	1,166	1,031
Accrued expenses	3,803	(152)	1,517
Operating lease liabilities	(882)	(698)	(1,067)
Operating lease right-of-use asset, net of non-cash portion	0	(59)	(3,889)
Net cash used in operating activities	(77,102)	(70,905)	(58,818)
Cash flows from investing activities:
Purchase of property, equipment and intangible assets	(103)	(615)	(1,362)
Net cash used in investing activities	(103)	(615)	(1,362)
Cash flows from financing activities:
Proceeds from exercise of stock options, warrants and pre-funded warrants and issuance of shares of common stock under employee stock purchase plans	208	260	561
Issuance costs related to sale of warrants for the purchase of common stock accounted for as a liability and amendments to loan and security agreement (Note 10)	(4,802)	0	0
Employee taxes paid related to net share settlement of vested restricted stock units	(12)	0	(278)
Proceeds from borrowings under loan and security agreements, net of issuance costs	0	0	12,388
Repayments of borrowings under loan and security agreement	(795)	0	0
Proceeds from sale of shares of common stock, redeemable common stock, warrants and pre-funded warrants, net of issuance costs	122,631	75,985	(277)
Payments for Repurchase of Common Stock	0	(2,000)	0
Net cash provided by financing activities	117,230	74,245	12,394
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(105)	(319)	402
Net increase (decrease) in cash, cash equivalents and restricted cash	39,920	2,406	(47,384)
Cash, cash equivalents and restricted cash at beginning of period	83,108	80,702	128,086
Cash, cash equivalents and restricted cash at end of period	123,028	83,108	80,702
Supplemental disclosure of cash flow information
Cash paid for interest	3,006	2,906	2,099
Supplemental disclosure of non-cash investing and financing activities:
Acquisition of property, equipment and right-of-use assets included in accounts payable	0	0	54
Lease Obligation Incurred	0	1,343	0
Issuance costs not yet paid	$ 661	$ 24	$ 0