Consolidated statements of cash flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating activities
Net loss	$ (37,002)	$ (21,860)	$ (24,027)
Non-cash items and reclassifications:
Change in fair value of derivative liability (Note 8)	(81)	52	(949)
Stock-based compensation (Note 7(e))	1,966	1,506	854
Stock-based purchase of patent rights			186
Unrealized foreign exchange loss and others	185	580	549
Financing costs			320
Fees and penalty on bank loan repayment			100
Amortization and extinguishment of remaining discount on preferred stock upon conversion of preferred stock			1,884
Changes in operating assets and liabilities:
Receivable, prepayments and deposits	(109)	(96)	(17)
Accounts payable and other liabilities	4,815	(450)	3,614
Cash used in operating activities	(30,226)	(20,268)	(17,486)
Investing activities
Purchase of investments	(106,442)	(60,703)	(36,475)
Proceeds from maturity of investments	59,097	13,196	12,990
Purchase of property and equipment	(713)	(27)	(114)
Sale of property and equipment		1	26
Cash used in investing activities	(48,058)	(47,533)	(23,573)
Financing activities
Public offering of common stock (Note 7(c))	75,368	98,038	53,130
Public offering costs (Note 7(c))	(4,692)	(6,210)	(5,251)
Proceeds from exercise of stock options	440	1,120
Bank loan repayment, fees and penalty			(2,600)
Payment on capital lease obligations	(4)
Cash provided by financing activities	71,112	92,948	45,279
Effect of exchange rate changes on cash and cash equivalents	(53)	(527)	(320)
Net change in cash and cash equivalents during the year	(7,225)	24,620	3,900
Cash and cash equivalents, beginning of year	39,526	14,906	11,006
Cash and cash equivalents, end of year	32,301	39,526	14,906
Supplemental disclosure of cash flow information:
Interest paid	1		32
Interest received	619	108	$ 91
Non-cash investing and financing activities:
Assets acquired through capital leases	65	11
Accrued offering costs		$ 35
Exercise of warrants on a net settlement basis	43
Accrued purchase of property & equipment	$ 77