Conjugates of a glycoprotein or a glycan with a toxic payload

A glycoprotein-toxic payload molecule conjugate represented by formula I

• [D-L-G]n-Gp Formula I
• wherein
• Gp is a glycoprotein comprising an N-glycan, wherein the N-glycan comprises a GlcNAc residue bound by a β-N linkage to an asparagine;
• n is an integer from 1 to about 20;
• D is a toxic payload molecule;
• L is a linker group covalently joining G to D;
• and
• G is a saccharide structure represented by formula II
• wherein
• R is a glycosidic bond to the N-glycan or a glycosidic bond to the GlcNAc residue bound by a β-N linkage to an asparagine;
• X1 is H or carboxyl;
• X2, X3 and X4 are each independently OH, H, amino, C2-C6 acylamide, phosphate or sulphate ester, or a bond to L;
• X5 is CH2OH, carboxyl, CH3, H, C1-C3 alkyl or substituted C1-C3 alkyl, or a bond to L;
• with the proviso that one substituent selected from X2, X3, X4 and X5 is a bond to L or bonded via a bond to L;
• and
• with the proviso that when X1 is carboxyl, then X2 is H, X3 is OH, X5 is C1-C3 alkyl or substituted C1-C3 alkyl;
• R is a glycosidic bond to the N-glycan;
• and X4 is a bond to L or X5 is bonded via a bond to L;
• or
• when X1 is H, then R is a glycosidic bond to the N-glycan or to the GlcNAc residue bound by a β-N linkage to an asparagine.