A compound of formula or a pharmaceutically acceptable salt thereof: wherein: L represents a binding moiety selected from a nucleic acid aptamer; S 1 represents a spacer selected from a ―CH 2) a - or ―CH 2) b -(CH 2 -CH 2 -O c -(CH 2) d - group, wherein one to five of said ―CH 2 - groups may optionally be substituted by one or more groups selected from -O-, ―C NH- and -NHC - and phenyl; a represents an integer selected from 1 to 35; b represents an integer selected from 0 to 5; c represents an integer selected from 1 to 20; d represents an integer selected from 1 to 20; S 2 represents a spacer selected from a ―(CH 2) e - or ―(CH 2) f -(CH 2 -CH 2 -O) g -(CH 2) h - group, wherein one to three of said ―CH 2 - groups may optionally be substituted by one or more groups selected from -N -, ―C NH- and -NHC -; e represents an integer selected from 1 to 15; f represents an integer selected from 1 to 10; g represents an integer selected from 1 to 20; h represents an integer selected from 1 to 5; S 3 represents a spacer selected from a ―(CH 2) q - or ―(CH 2) r -(CH 2 -CH 2 -O) s -(CH 2) t - group, wherein one to ten of said ―CH 2 - groups may optionally be substituted by one or more groups selected from -N -, ―C NH-, -NHC - and -O-; q represents an integer selected from 1 to 25; r represents an integer selected from 1 to 10; s represents an integer selected from 1 to 20; t represents an integer selected from 1 to 10; X 1 represents -O-; Y 1 and Y 2 independently represent a bond, -O-, -S-, -NH-, -NHC -, -C NH-, -OC -, - C O-, -SC -, -C S-, -NHSO 2 -, -SO 2 NH- or ―NHC NH- group; F represents a carbohydrate molecule capable of binding to a human anti-alpha-galactosyl antibody; m1 and m2 independently represent an integer selected from 1 to 5; n represents an integer selected from 1 or 2; and CyA, CyB and CyC independently represent biphenyl or triphenyl. L represents a binding moiety selected from a nucleic acid aptamer; S 1 represents a spacer selected from a ―CH 2) a - or ―CH 2) b -(CH 2 -CH 2 -O c -(CH 2) d - group, wherein one to five of said ―CH 2 - groups may optionally be substituted by one or more groups selected from -O-, ―C NH- and -NHC - and phenyl; a represents an integer selected from 1 to 35; b represents an integer selected from 0 to 5; c represents an integer selected from 1 to 20; d represents an integer selected from 1 to 20; S 2 represents a spacer selected from a ―(CH 2) e - or ―(CH 2) f -(CH 2 -CH 2 -O) g -(CH 2) h - group, wherein one to three of said ―CH 2 - groups may optionally be substituted by one or more groups selected from -N -, ―C NH- and -NHC -; e represents an integer selected from 1 to 15; f represents an integer selected from 1 to 10; g represents an integer selected from 1 to 20; h represents an integer selected from 1 to 5; S 3 represents a spacer selected from a ―(CH 2) q - or ―(CH 2) r -(CH 2 -CH 2 -O) s -(CH 2) t - group, wherein one to ten of said ―CH 2 - groups may optionally be substituted by one or more groups selected from -N -, ―C NH-, -NHC - and -O-; q represents an integer selected from 1 to 25; r represents an integer selected from 1 to 10; s represents an integer selected from 1 to 20; t represents an integer selected from 1 to 10; X 1 represents -O-; Y 1 and Y 2 independently represent a bond, -O-, -S-, -NH-, -NHC -, -C NH-, -OC -, - C O-, -SC -, -C S-, -NHSO 2 -, -SO 2 NH- or ―NHC NH- group; F represents a carbohydrate molecule capable of binding to a human anti-alpha-galactosyl antibody; m1 and m2 independently represent an integer selected from 1 to 5; n represents an integer selected from 1 or 2; and CyA, CyB and CyC independently represent biphenyl or triphenyl.