Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Operating expenses:
Research and development	$ 9,509	$ 4,966	$ 27,316	$ 12,076
General and administrative	3,148	1,486	7,402	8,410
Impairment of acquired IPR&D			21,692
Depreciation	127	91	387	272
Total operating expenses	12,784	6,543	56,797	20,758
Loss from operations	(12,784)	(6,543)	(56,797)	(20,758)
Other income (expense):
Interest expense, net	111	(277)	(106)	(1,038)
Foreign currency exchange gain (loss)	(7)	(71)	87	(225)
Loss on extinguishment of debt				(1,816)
Change in fair value of financial instruments	10	(43)	(52)	(280)
Total other income (expense)	114	(391)	(71)	(3,359)
Loss before income taxes	(12,670)	(6,934)	(56,868)	(24,117)
Income tax benefit	110	117	5,866	824
Net loss	(12,560)	(6,817)	(51,002)	(23,293)
Accretion of redeemable convertible preferred stock				(578)
Deemed dividend on beneficial conversion feature				(404)
Net loss attributable to common stockholders	(12,560)	(6,817)	(51,002)	(24,275)
Other comprehensive income:
Gain (loss) on foreign currency translation	(105)	348	(620)	1,343
Unrealized gain (loss) on short-term investments	13	(5)	26	(5)
Total Comprehensive Loss	$ (12,652)	$ (6,474)	$ (51,596)	$ (21,955)
Net loss per share:
Basic and diluted	$ (0.37)	$ (0.28)	$ (1.61)	$ (1.76)
Weighted average common shares outstanding
Basic and diluted	33,708,563	24,209,517	31,648,510	13,770,032