Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (31,416)	$ (38,619)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	4,498	3,965
Depreciation	228	151
Non-cash restructuring charges		811
Other	30	36
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(483)	(843)
Accrued liabilities	681	7,184
Accounts payable	(2,093)	(184)
Net cash used in operating activities	(28,555)	(27,499)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of property and equipment	(92)	(196)
Change in restricted cash	13	25
Proceeds from sale of property and equipment		43
Net cash used in investing activities	(79)	(128)
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	194
Payment of deferred offering costs		(15)
Net cash provided by financing activities	27,445	179
Effect of foreign exchange rate changes on cash and cash equivalents	6	(50)
NET DECREASE IN CASH AND CASH EQUIVALENTS	(1,183)	(27,498)
CASH AND CASH EQUIVALENTS - Beginning of period	109,007	150,180
CASH AND CASH EQUIVALENTS - End of period	107,824	122,682
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:
Cash paid for income taxes	221	94
SUPPLEMENTAL DISCLOSURES OF NON-CASH INVESTING AND FINANCING INFORMATION:
Property and equipment purchases included in accounts payable and accrued liabilities	$ 5	$ 10