Condensed consolidated statements of cash flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Operating activities
Net loss	$ (26,698)	$ (33,915)
Non-cash items:
Stock-based compensation (Note 6(c))	3,861	2,868
Unrealized foreign exchange loss and others	628	481
Changes in operating assets and liabilities:
Receivable, prepayments and deposits	720	(444)
Accounts payable and other liabilities	(313)	(2,103)
Cash used in operating activities	(21,802)	(33,113)
Investing activities
Purchase of investments		(5,995)
Proceeds from maturity of investments	56,000	54,000
Purchase of property and equipment	(49)	(478)
Cash provided by investing activities	55,951	47,527
Financing activities
Proceeds from exercise of stock options	602	380
Payment on capital lease obligations	(30)	(11)
Cash provided by financing activities	572	369
Effect of exchange rate changes on cash and cash equivalents	(22)	21
Net change in cash and cash equivalents during the period	34,699	14,804
Cash and cash equivalents, beginning of period	52,032	32,301
Cash and cash equivalents, end of period	86,731	47,105
Supplemental disclosure of cash flow information:
Interest received	$ 1,210	996
Non-cash investing and financing activities:
Accrued purchase of property & equipment		(77)
Accrued offering costs		$ (30)