Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (21,421)	$ (23,410)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	3,038	2,666
Depreciation	156	106
Non-cash restructuring charges		811
Other	17	22
Changes in operating assets and liabilities:
Prepaid expenses and other assets	696	468
Accrued liabilities	(133)	(592)
Accounts payable	(2,035)	376
Net cash used in operating activities	(19,682)	(19,553)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of property and equipment	(87)	(193)
Change in restricted cash	13	25
Proceeds from sale of property and equipment		13
Net cash used in investing activities	(74)	(155)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common stock upon follow-on offering, net of offering costs	27,422
Proceeds from exercise of common stock options	23	120
Payment of deferred offering costs		(15)
Net cash provided by financing activities	27,445	105
Effect of foreign exchange rate changes on cash and cash equivalents	3	(27)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	7,692	(19,630)
CASH AND CASH EQUIVALENTS - Beginning of period	109,007	150,180
CASH AND CASH EQUIVALENTS - End of period	116,699	130,550
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:
Cash paid for income taxes	187	80
SUPPLEMENTAL DISCLOSURES OF NON-CASH INVESTING AND FINANCING INFORMATION:
Property and equipment purchases included in accounts payable and accrued liabilities	$ 10	$ 11