Condensed Consolidated Statements of Convertible Preferred Shares and Shareholders’ Equity (Deficit) - USD ($) $ in Thousands	Series A Convertible Preferred Shares	Series B1 Convertible Preferred Shares	Series B2 Convertible Preferred Shares	Ordinary Shares	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Total
Beginning balance at Dec. 31, 2017	$ 41,820	$ 54,621		$ 5	$ 838	$ 69	$ (48,096)	$ (47,184)
Beginning balance (in shares) at Dec. 31, 2017	2,800,001	3,947,198		368,995
Increase (decrease) in shareholders' equity (deficit)
Issuance of restricted share awards				$ 1	53			54
Issuance of restricted share awards (in shares)				35,725
Issuance of ordinary shares upon exercise of share options (in shares)				9,002
Share based compensation expense					198			198
Foreign currency translation adjustment						1,796		1,796
Net loss							(2,534)	(2,534)
Ending balance at Mar. 31, 2018	$ 41,820	$ 54,621		$ 6	1,089	1,865	(50,630)	(47,670)
Ending balance (in shares) at Mar. 31, 2018	2,800,001	3,947,198		413,722
Beginning balance at Dec. 31, 2017	$ 41,820	$ 54,621		$ 5	838	69	(48,096)	(47,184)
Beginning balance (in shares) at Dec. 31, 2017	2,800,001	3,947,198		368,995
Increase (decrease) in shareholders' equity (deficit)
Foreign currency translation adjustment								(1,398)
Net loss								(15,205)
Ending balance at Sep. 30, 2018	$ 41,820	$ 54,621		$ 6	1,654	(1,329)	(63,301)	(62,970)
Ending balance (in shares) at Sep. 30, 2018	2,800,001	3,947,198		442,409
Beginning balance at Mar. 31, 2018	$ 41,820	$ 54,621		$ 6	1,089	1,865	(50,630)	(47,670)
Beginning balance (in shares) at Mar. 31, 2018	2,800,001	3,947,198		413,722
Increase (decrease) in shareholders' equity (deficit)
Issuance of restricted share awards					26			26
Issuance of restricted share awards (in shares)				12,757
Issuance of ordinary shares upon exercise of share options (in shares)				359
Share based compensation expense					309			309
Foreign currency translation adjustment						(2,657)		(2,657)
Net loss							(4,979)	(4,979)
Ending balance at Jun. 30, 2018	$ 41,820	$ 54,621		$ 6	1,424	(792)	(55,609)	(54,971)
Ending balance (in shares) at Jun. 30, 2018	2,800,001	3,947,198		426,838
Increase (decrease) in shareholders' equity (deficit)
Issuance of restricted share awards					27			27
Issuance of restricted share awards (in shares)				15,571
Share based compensation expense					203			203
Foreign currency translation adjustment						(537)		(537)
Net loss							(7,692)	(7,692)
Ending balance at Sep. 30, 2018	$ 41,820	$ 54,621		$ 6	1,654	(1,329)	(63,301)	(62,970)
Ending balance (in shares) at Sep. 30, 2018	2,800,001	3,947,198		442,409
Beginning balance at Dec. 31, 2018	$ 41,820	$ 54,621	$ 25,756
Beginning balance (in shares) at Dec. 31, 2018	2,800,001	3,947,198	1,323,248
Increase (decrease) in convertible preferred shares
Issuance of convertible preferred shares			$ 1,583
Issuance of convertible preferred shares (in shares)			80,385
Ending balance at Mar. 31, 2019	$ 41,820	$ 54,621	$ 27,339
Ending balance (in shares) at Mar. 31, 2019	2,800,001	3,947,198	1,403,633
Beginning balance at Dec. 31, 2018				$ 10	1,857	(1,751)	(69,942)	$ (69,826)
Beginning balance (in shares) at Dec. 31, 2018				814,728				814,728
Increase (decrease) in shareholders' equity (deficit)
Issuance of restricted share awards				$ 1	103			$ 104
Issuance of restricted share awards (in shares)				27,304
Issuance of ordinary shares upon exercise of share options (in shares)				3
Share based compensation expense					172			172
Foreign currency translation adjustment						1,080		1,080
Net loss							(6,503)	(6,503)
Ending balance at Mar. 31, 2019				$ 11	2,132	(671)	(76,445)	(74,973)
Ending balance (in shares) at Mar. 31, 2019				842,035
Beginning balance at Dec. 31, 2018	$ 41,820	$ 54,621	$ 25,756
Beginning balance (in shares) at Dec. 31, 2018	2,800,001	3,947,198	1,323,248
Ending balance (in shares) at Sep. 30, 2019	0	0	0
Beginning balance at Dec. 31, 2018				$ 10	1,857	(1,751)	(69,942)	$ (69,826)
Beginning balance (in shares) at Dec. 31, 2018				814,728				814,728
Increase (decrease) in shareholders' equity (deficit)
Reclassification of warrant liability to additional paid-in capital and exercise of warrants								$ 10,021
Foreign currency translation adjustment								(856)
Net loss								(26,202)
Ending balance at Sep. 30, 2019				$ 226	193,850	(2,607)	(96,144)	$ 95,325
Ending balance (in shares) at Sep. 30, 2019				17,902,869				17,902,869
Beginning balance at Mar. 31, 2019	$ 41,820	$ 54,621	$ 27,339
Beginning balance (in shares) at Mar. 31, 2019	2,800,001	3,947,198	1,403,633
Increase (decrease) in convertible preferred shares
Conversion of convertible preferred shares to ordinary shares	$ (41,820)	$ (54,621)	$ (27,339)
Conversion of convertible preferred shares to ordinary shares (in shares)	(2,800,001)	(3,947,198)	(1,403,633)
Beginning balance at Mar. 31, 2019				$ 11	2,132	(671)	(76,445)	$ (74,973)
Beginning balance (in shares) at Mar. 31, 2019				842,035
Increase (decrease) in shareholders' equity (deficit)
Conversion of convertible preferred shares to ordinary shares				$ 146	123,634			123,780
Conversion of convertible preferred shares to ordinary shares (in shares)				11,647,529
Reclassification of warrant liability to additional paid-in capital and exercise of warrants				$ 9	10,018			10,027
Reclassification of warrant liability to additional paid-in capital and exercise of warrants (in shares)				702,557
Issuance of ADSs in initial public offering, net of underwriting discounts, commissions and offering expenses of $8.4 million				$ 59	56,469			56,528
Number of shares issued (in shares)				4,637,666
Issuance of restricted share awards				$ 1	292			293
Issuance of restricted share awards (in shares)				56,643
Issuance of ordinary shares upon exercise of share options					21			21
Issuance of ordinary shares upon exercise of share options (in shares)				14,301
Share based compensation expense					612			612
Foreign currency translation adjustment						(1,512)		(1,512)
Net loss							(10,217)	(10,217)
Ending balance at Jun. 30, 2019				$ 226	193,178	(2,183)	(86,662)	104,559
Ending balance (in shares) at Jun. 30, 2019				17,900,731
Ending balance (in shares) at Sep. 30, 2019	0	0	0
Increase (decrease) in shareholders' equity (deficit)
Issuance of ordinary shares upon exercise of share options (in shares)				2,138
Share based compensation expense					819			819
Public offering costs					(147)			(147)
Foreign currency translation adjustment						(424)		(424)
Net loss							(9,482)	(9,482)
Ending balance at Sep. 30, 2019				$ 226	$ 193,850	$ (2,607)	$ (96,144)	$ 95,325
Ending balance (in shares) at Sep. 30, 2019				17,902,869				17,902,869