Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Operating activities
Net loss	$ (6,498)	$ (6,552)
Reconciliation of net loss to net cash used in operating activities:
Depreciation	40	24
Amortization of premium/discount on available-for-sale securities	4	36
Unrealized gain on forward foreign currency contracts included in net income		(178)
Foreign currency remeasurement loss	(59)	(28)
Stock-based compensation	845	866
Changes in:
Prepaid expenses and other assets	293	331
Interest receivable	(15)	(26)
Accounts payable, accrued expenses and other current liabilities	(2,056)	(367)
Net cash used in operating activities	(7,446)	(5,894)
Investing activities
Purchases of available-for-sale investments		(23,721)
Proceeds from maturities of available-for-sale investments	4,920	13,614
Purchase of property and equipment	(6)	(8)
Net cash provided by (used in) investing activities	4,914	(10,115)
Financing activities
Exercise of stock options	108	12
Proceeds from issuance of common stock, net of issuance costs	105
Net cash provided by financing activities	213	12
Effect of exchange rate changes on cash	59	28
Decrease in cash and cash equivalents	(2,260)	(15,969)
Cash and cash equivalents, beginning of period	36,392	40,031
Cash and cash equivalents, end of period	$ 34,132	$ 24,062