Consolidated statements of operations and comprehensive loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating expenses
Research and development	$ 28,382	$ 15,799	$ 18,079
General and administrative	9,263	5,541	4,296
Total operating expenses	37,645	21,340	22,375
Other income (expenses)
Amortization and extinguishment of remaining discount on preferred shares upon conversion of preferred shares			(1,884)
Interest expense	(1)		(451)
Other income (expenses) (Note 8)	644	(520)	683
Total Other income (expenses)	643	(520)	(1,652)
Net loss	$ (37,002)	$ (21,860)	$ (24,027)
Net loss per common stock - basic and diluted (Note 9)	$ (1.96)	$ (1.73)	$ (2.75)
Basic and diluted weighted average number of common stock outstanding (Note 9)	18,893,515	12,637,839	8,667,387
Comprehensive loss:
Net loss	$ (37,002)	$ (21,860)	$ (24,027)
Other comprehensive income (loss) - unrealized gain (loss) on available-for-sale securities	121	(286)	(4)
Comprehensive loss	$ (36,881)	$ (22,146)	$ (24,031)