Patent ID: 8053564

Claim:
A compound of formula (I): wherein: A, A 1 and A 2 independently represent an antibody or fragment thereof; L, L 1 and L 2 independently represent a spacer group; R represents a reactive group which is suitable for attaching an effector molecule but does not react with any of A, A 1 and A 2 , and wherein R is selected from except that when Y represents a covalent bond and B represents —NHCO— or —CO— then R is selected from Y represents a covalent bond or —(CH 2 ) y -; B represents —CONH—, —NHCO— or —CO—; V represents a covalent bond or —(CH 2 ) v -; W, W 1 and W 2 independently represent —(CH 2 ) w O—; T, T 1 and T 2 independently represent a linker group; v is 1, 2, 3 or 4; w is 1, 2, 3 or 4; and y is 1, 2, 3, 4, 5 or 6.