Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
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	$ 321	$ 138	$ 629	$ 247
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	625	338	1,183	636
Research and development	5,241	3,090	9,590	5,723
General and administrative	2,613	1,891	5,083	3,878
Total operating expenses	7,854	4,981	14,673	9,601
Loss from operations	(7,854)	(4,981)	(14,673)	(9,601)
Investment income	53	37	109	77
Other (expense) income, net	(104)	(128)	107	(128)
Total other (expense) income	(51)	(91)	216	(51)
Net loss	(7,905)	(5,072)	(14,457)	(9,652)
Unrealized (loss) gain on available-for-sale investments	(2)	3	21	9
Comprehensive loss	(7,907)	(5,069)	(14,436)	(9,643)
Net loss attributable to common stockholders	$ (7,905)	$ (5,072)	$ (14,457)	$ (9,652)
Net loss per share attributable to common stockholders - basic and diluted (in dollars per share)	$ (0.48)	$ (0.31)	$ (0.87)	$ (0.59)
Weighted-average common shares outstanding used in net loss per share attributable to common stockholders - basic and diluted (in shares)	16,561,239	16,449,937	16,534,413	16,449,316
Allocated share-based compensation	$ 946	$ 476	$ 1,812	$ 883
Included in other (expense) income, net, above, are the following amounts from forward foreign currency contracts:
Realized losses from forward foreign currency contracts	(10)	(14)	(4)	(14)
Unrealized (losses) gains from forward foreign currency contracts	(53)	(112)	125	(112)
Total	$ (63)	$ (126)	$ 121	$ (126)