Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Operating activities:
Net loss	$ (11,998)	$ (10,366)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	37	8
Stock-based compensation expense	1,080	939
Amortization of right-of-use asset	243	76
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	1,807	(162)
Other assets	(1)	(59)
Accounts payable	1,329	398
Accrued expenses and other liabilities	(2,255)	(1,291)
Operating lease liabilities	(403)	(144)
Cash used in operating activities	(10,161)	(10,601)
Investing activities:
Purchase of property and equipment	(26)	(10)
Proceeds from sale of marketable securities	0	2,986
Cash (used in) provided by investing activities	(26)	2,976
Financing activities:
Repayment of debt	0	(45)
Payment of financing costs	(197)	(15)
Proceeds from the issuance of common stock, net of issuance costs	5,718	0
Proceeds from option and warrant exercises	78	0
Repayment of principal on finance lease	(10)	0
Cash provided by (used in) financing activities	5,589	(60)
Effect of foreign currency exchange rate changes on cash	(37)	(14)
Net decrease in cash, cash equivalents and restricted cash	(4,635)	(7,699)
Cash, cash equivalents and restricted cash at beginning of period	63,512	73,770
Cash, cash equivalents and restricted cash at end of period	58,877	66,071
Supplemental schedule of non-cash investing and financing activities:
Financing costs in accounts payable and accrued expenses	$ 68	$ 60