A compound of formula (I) 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(O)NH- and -NHC(O)- 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(H)-, ―C(O)NH- and -NHC(O)-; 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(H)-, ―C(O)NH-, -NHC(O)- 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(O)-, -C(O)NH-, -OC(O)-, - C(O)O-, -SC(O)-, -C(O)S-, -NHSO 2 -, -SO 2 NH- or ―NHC(O)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(O)NH- and -NHC(O)- 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(H)-, ―C(O)NH- and -NHC(O)-; 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(H)-, ―C(O)NH-, -NHC(O)- 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(O)-, -C(O)NH-, -OC(O)-, - C(O)O-, -SC(O)-, -C(O)S-, -NHSO 2 -, -SO 2 NH- or ―NHC(O)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. <EOS>