Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities:
Net loss	$ (88,696)	$ (62,131)	$ (52,807)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	6,180	5,428	2,050
Depreciation and amortization expense	499	351	103
Goodwill impairment	9,758	0	0
Loss on transfer of nonfinancial assets	0	0	3,900
Non-cash lease expense	1,393	879	569
Accretion of debt discount	756	532	695
Loss on extinguishment of debt	0	162	566
Change in fair value of preferred stock warrant and derivative liability	366	437	105
Other	337	(413)	0
Changes in operating assets and liabilities:
Prepaid expenses, other current assets and research and development incentive receivable	(1,755)	(1,655)	109
Accounts payable	1,166	1,031	(2,752)
Accrued expenses	(152)	1,517	160
Lease liabilities	(698)	(1,067)	(753)
Operating lease right-of-use asset, net of non-cash portion	(59)	(3,889)	0
Net cash used in operating activities	(70,905)	(58,818)	(48,055)
Cash flows from investing activities:
Cash, cash equivalents and restricted cash acquired in connection with the Merger	0	0	26,406
Proceeds from transfer of non-financial assets	0	0	1,000
Purchase of property, equipment and intangible assets	(615)	(1,362)	(174)
Net cash provided by (used in) investing activities	(615)	(1,362)	27,232
Cash flows from financing activities:
Proceeds from exercise of stock options, warrants and pre-funded warrants an issuance of shares of common stock under employee stock purchase plans	260	561	792
Employee taxes paid related to net share settlement of vested restricted stock units	0	(278)	0
Proceeds from borrowings under loan and security agreements, net of issuance costs	0	12,388	9,849
Repayments of borrowings under loan and security agreement	0	0	(9,368)
Proceeds from sale of shares of common stock, redeemable common stock, warrants and pre-funded warrants, net of issuance costs	75,985	(277)	139,388
Payments for Repurchase of Common Stock	(2,000)	0	0
Net cash provided by financing activities	74,245	12,394	140,661
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(319)	402	(250)
Net (decrease) increase in cash, cash equivalents and restricted cash	2,406	(47,384)	119,588
Cash, cash equivalents and restricted cash at beginning of period	80,702	128,086	8,498
Cash, cash equivalents and restricted cash at end of period	83,108	80,702	128,086
Supplemental disclosure of cash flow information
Cash paid for interest	2,906	2,099	1,284
Supplemental disclosure of non-cash investing and financing activities:
Acquisition of property, equipment and right-of-use assets included in accounts payable	0	54	40
Lease Obligation Incurred	1,343	0	0
Issuance costs not yet paid	24	0	775
Conversion of convertible preferred stock into common stock	0	0	64,675
Conversion of redeemable common stock into common stock	0	0	734
Conversion of convertible preferred stock warrants into common stock warrants	0	0	5,235
Fair value of net assets acquired in the Merger in exchange for common shares, excluding cash acquired	$ 0	$ 0	$ 19,952