Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Operating activities
Net loss	$ (6,531,000)	$ (6,081,000)
Reconciliation of net loss to net cash used in operating activities:
Depreciation	174,000	32,000
Amortization of premium/discount on available-for-sale securities	(4,000)	3,000
Foreign currency remeasurement loss		(136,000)
Stock-based compensation	780,000	821,000
Changes in:
Prepaid expenses and other assets	349,000	121,000
Operating lease right-of-use asset	65,000
Interest receivable	(15,000)	4,000
Accounts payable and accrued expenses	155,000	(220,000)
Operating lease liability	(65,000)
Net cash used in operating activities	(5,092,000)	(5,456,000)
Investing activities
Proceeds from maturities of available-for-sale investments	2,500,000	7,515,000
Proceeds from sale of available-for-sale investments		1,999,000
Purchase of property and equipment	(16,000)	(9,000)
Net cash provided by investing activities	2,484,000	9,505,000
Effect of exchange rate changes on cash		137,000
Decrease in cash, cash equivalents and restricted cash	(2,608,000)	4,186,000
Cash, cash equivalents and restricted cash, beginning of period	19,393,000	21,192,000
Cash, cash equivalents and restricted cash, end of period	$ 16,785,000	$ 25,378,000