Unaudited Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Statement And Statement Of Comprehensive Income [Abstract]
Revenue	$ 181	$ 148	$ 675	$ 795
Operating expenses
Research and development	(14,387)	(9,951)	(40,979)	(32,586)
General and administrative	(7,460)	(2,683)	(13,430)	(7,917)
Impairment	(859)	0	(859)	0
Total operating expenses	(22,706)	(12,634)	(55,268)	(40,503)
Other operating income	4,309	6,296	14,949	19,881
Operating loss	(18,216)	(6,190)	(39,644)	(19,827)
Other income (expense), net	416	(75)	296	(231)
Loss before income tax	(17,800)	(6,265)	(39,348)	(20,058)
Income tax benefit (expense)	99	(111)	93	13
Net loss	$ (17,701)	$ (6,376)	$ (39,255)	$ (20,045)
Basic earnings (loss) per share (in dollars per share)	$ (0.26)	$ (0.20)	$ (0.58)	$ (0.63)
Diluted earnings (loss) per share (in dollars per share)	$ (0.26)	$ (0.20)	$ (0.58)	$ (0.63)
Other comprehensive income / (loss)
Foreign currency translation adjustment	$ 2,255	$ (1,255)	$ (2,312)	$ (1,299)
Total comprehensive loss	$ (15,446)	$ (7,631)	$ (41,567)	$ (21,344)