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	$ (8,961)	$ (6,534)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	45	42
Amortization of debt discount		3
Stock-based compensation	2,443	1,689
Non-cash lease expense	170	177
Non-cash expense related to equity consideration for a service agreement	494
Unrealized gain on foreign exchange rate changes	(109)
Changes in:
Prepaid expenses and other current assets	337	(16)
Accounts payable	(222)	(307)
Collaboration and device development payable		(108)
Accrued expenses	(69)	(238)
Operating lease liabilities	(176)	(190)
Net cash used in operating activities	(6,048)	(5,482)
Cash flows from financing activities:
Proceeds from issuance of common stock and warrants, net of issuance costs	27,390
Proceeds from the ATM Program, net of expenses	570
Principal payments on loans payable	(352)	(199)
Net cash provided by (used in) financing activities	27,608	(199)
Effect of exchange rate changes on cash and cash equivalents		(98)
Net increase (decrease) in cash, cash equivalents, and restricted cash	21,560	(5,779)
Cash, cash equivalents, and restricted cash - beginning of period	17,084	22,732
Cash, cash equivalents, and restricted cash - end of period	38,644	16,953
Operating lease liabilities arising from obtaining right-of-use assets	$ 2,000