Condensed consolidated statements of cash flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Operating activities
Net loss	$ (33,915)	$ (25,758)
Non-cash items:
Change in fair value of derivative liability (Note 6)		(81)
Stock-based compensation (Note 5(c))	2,868	1,405
Unrealized foreign exchange loss and others	481	122
Changes in operating assets and liabilities:
Receivable, prepayments and deposits	(444)	(357)
Accounts payable and other liabilities	(2,103)	3,440
Cash used in operating activities	(33,113)	(21,229)
Investing activities
Purchase of investments	(5,995)	(56,336)
Proceeds from maturity of investments	54,000	53,598
Purchase of property and equipment	(478)	(616)
Cash provided by (used in) investing activities	47,527	(3,354)
Financing activities
Proceeds from exercise of stock options	380	440
Payment on capital lease obligations	(11)	(2)
Public offering of common stock		75,368
Public offering costs		(4,531)
Cash provided by financing activities	369	71,275
Effect of exchange rate changes on cash and cash equivalents	21	7
Net change in cash and cash equivalents during the period	14,804	46,699
Cash and cash equivalents, beginning of period	32,301	39,526
Cash and cash equivalents, end of period	47,105	86,225
Supplemental disclosure of cash flow information:
Interest received	996	481
Non-cash investing and financing activities:
Accrued purchase of property & equipment	(77)	103
Assets acquired through capital leases		35
Accrued offering costs	$ (30)	306
Exercise of warrants on a net settlement basis		$ (43)