Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Statement [Abstract]
Licensing revenues	$ 0	$ 0	$ 0	$ 47,500
Operating expenses:
Research and development	6,641	3,868	15,620	12,241
Selling, general and administrative	6,553	1,761	13,214	5,057
Total operating expenses	13,194	5,629	28,834	17,298
(Loss) income from operations	(13,194)	(5,629)	(28,834)	30,202
Other (income) expense:
Grant and other income	(30)	(370)	(123)	(536)
Interest income	(61)	(38)	(156)	(109)
Interest expense	0	885	862	2,632
Foreign currency (gains) losses	(35)	0	(66)	14
Net (loss) income	(13,068)	(6,106)	(29,351)	28,201
Deemed dividend	4,105	2,752	11,255	8,254
Accretion to redemption value	19	527	1,093	1,582
Net (loss) income attributable to common stockholders	$ (17,192)	$ (9,385)	$ (41,699)	$ 18,365
Net (loss) income per share of common stock
basic (in USD per share)	$ (4.23)	$ (2.32)	$ (10.25)	$ 0.77
diluted (in USD per share)	$ (4.23)	$ (2.32)	$ (10.25)	$ 0.63
Weighted average common shares outstanding
diluted (in shares)	4,067,717	4,050,065	4,067,717