Condensed consolidated statements of cash flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Operating activities
Net loss	$ (14,623)	$ (8,316)
Non-cash items:
Stock-based compensation (Note 5(c))	1,312	631
Unrealized foreign exchange loss and others	132	146
Changes in operating assets and liabilities:
Receivable, prepayments and deposits	(779)	(426)
Accounts payable and other liabilities	(1,631)	(3,315)
Cash used in operating activities	(15,589)	(11,280)
Investing activities
Proceeds from maturity of investments	30,000
Purchase of property and equipment	(40)	(108)
Cash provided by (used in) investing activities	29,960	(108)
Financing activities
Proceeds from exercise of stock options	203
Payment on capital lease obligations	(4)	(4)
Cash provided by (used in) financing activities	199	(4)
Effect of exchange rate changes on cash and cash equivalents	8	7
Net change in cash and cash equivalents during the period	14,578	(11,385)
Cash and cash equivalents, beginning of period	52,032	32,301
Cash and cash equivalents, end of period	66,610	20,916
Supplemental disclosure of cash flow information:
Interest received	$ 296	329
Non-cash investing and financing activities:
Accrued purchase of property & equipment		$ (24)