Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($)	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Operating activities
Net loss	$ (11,846,000)	$ (10,960,000)
Reconciliation of net loss to net cash used in operating activities:
Depreciation	196,000	61,000
Amortization of discount on available-for-sale securities	(4,000)	(14,000)
Foreign currency remeasurement loss	(1,000)	(25,000)
Stock-based compensation	881,000	1,743,000
Changes in:
Prepaid expenses and other assets	750,000	396,000
Operating lease right-of-use asset	132,000
Interest receivable	5,000	4,000
Accounts payable and accrued expenses	(1,023,000)	(7,009,000)
Operating lease liability	(132,000)
Net cash used in operating activities	(11,042,000)	(15,804,000)
Investing activities
Purchases of available-for-sale investments		(10,957,000)
Proceeds from maturities of available-for-sale investments	2,500,000	15,990,000
Proceeds from sale of available-for-sale investments		1,999,000
Purchase of property and equipment	(16,000)	(21,000)
Net cash provided by investing activities	2,484,000	7,011,000
Financing activities
Proceeds from issuance of common stock under ESPP		84,000
Net cash provided by financing activities		84,000
Effect of exchange rate changes on cash		24,000
Decrease in cash, cash equivalents and restricted cash	(8,558,000)	(8,685,000)
Cash, cash equivalents and restricted cash, beginning of period	19,393,000	21,192,000
Cash, cash equivalents and restricted cash, end of period	$ 10,835,000	$ 12,507,000