Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Research and Development Expense [Member]
Included in operating expenses, above, are the following amounts for non-cash stock based compensation expense:
Allocated share-based compensation	$ 184	$ 47	$ 431	$ 68
General and Administrative Expense [Member]
Included in operating expenses, above, are the following amounts for non-cash stock based compensation expense:
Allocated share-based compensation	$ 427	138	$ 1,063	166
Revenue		2,948		2,948
Research and development	$ 3,078	1,773	$ 8,801	4,558
General and administrative	2,004	1,041	5,882	2,697
Total operating expenses	5,082	2,814	14,683	7,255
Income (loss) from operations	(5,082)	134	(14,683)	(4,307)
Investment income	$ 34	$ 10	$ 111	13
Interest expense				(857)
Other expense	$ (335)	$ (5,325)	$ (463)	(5,424)
Total other expense	(301)	(5,315)	(352)	(6,268)
Net loss	(5,383)	(5,181)	(15,035)	(10,575)
Unrealized gain (loss) on available-for-sale investments	3	12	12	(11)
Comprehensive loss	(5,380)	(5,169)	(15,023)	(10,586)
Net loss	$ (5,383)	(5,181)	$ (15,035)	(10,575)
Accretion of redeemable convertible preferred stock to redemption value		(2,277)		(5,686)
Net loss attributable to common stockholders	$ (5,383)	$ (7,458)	$ (15,035)	$ (16,261)
Net loss per share attributable to common stockholders - basic and diluted (in dollars per share)	$ (0.33)	$ (31)	$ (0.91)	$ (67.65)
Weighted-average common shares outstanding used in net loss per share attributable to common stockholders - basic and diluted (in shares)	16,466,945	240,610	16,455,257	240,375
Allocated share-based compensation	$ 611	$ 185	$ 1,494	$ 234
Included in other expense, above, are the following amounts from forward foreign currency contracts:
Realized losses from forward foreign currency contracts			(14)
Unrealized losses from forward foreign currency contracts	$ (314)		(426)
Total	$ (314)		$ (440)