Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash flows from operating activities:
Net loss	$ (7,422)	$ (6,402)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	157	463
Gain on disposal of equipment	(44)
Noncash interest expense	15	26
Share-based compensation	948	247
Change in fair value of derivative liability		320
ROU asset amortization	256
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	1,173	(24)
Other long-term assets		(34)
Accounts payable		(285)
Accrued expenses	(442)	(2,072)
Operating lease liability	(246)
Net cash used in operating activities	(5,605)	(7,761)
Cash flows from investing activities:
Purchases of property and equipment	(128)	(12)
Proceeds from sale of equipment	115
Net cash used in investing activities	(13)	(12)
Cash flows from financing activities:
Repayment of borrowings under loan	(1,875)
Net cash used in financing activities	(1,875)
Net change in cash, cash equivalents and restricted cash	(7,493)	(7,773)
Cash, cash equivalents and restricted cash at beginning of period	47,339	25,566
Cash, cash equivalents and restricted cash at end of period	39,846	17,793
Supplemental disclosure of cash flow information
Cash paid for interest	137	256
Supplemental disclosure of financing activities
Acquisition of equipment included in accrued expenses	161	15
Deferred offering costs included in accrued expenses		$ 64
ROU asset acquired through operating leases	$ 5,148