Patent ID: 7851432

Claim:
A maytansinoid-cell-binding agent conjugate, wherein the maytansinoid is represented by formula 4 1 ′: wherein: Y l ′ represents (CR 7 R 8 ) l (CR 9 ═CR 10 ) p (C≡C) q A o (CR 5 R 6 ) m D u (CR 11 ═CR 12 ) r (C≡C) s B t (CR 3 R 4 ) n CR 1 R 2 S—, wherein: R 1 and R 2 are each independently linear alkyl or alkenyl having from 1 to 10 carbon atoms, branched or cyclic alkyl or alkenyl having from 3 to 10 carbon atoms, phenyl, phenyl substituted with at least one alkyl containing from 1-4 carbon atoms, or an alkoxy, halogen or nitro, or heterocyclic aromatic or heterocyclic radical, and in addition R 2 can be H; A, B, and D, each independently is cycloalkyl or cycloalkenyl having 3-10 carbon atoms, simple aryl or aryl substituted with at least one alkyl containing from 1-4 carbon atoms, or an alkoxy, halogen or nitro, or heterocyclic aromatic or heterocyclic radical; R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , R 10 , R 11 , and R 12 are each independently H, linear alkyl or alkenyl having from 1 to 10 carbon atoms, branched or cyclic alkyl or alkenyl having from 3 to 10 carbon atoms, phenyl, phenyl substituted with at least one alkyl containing from 1-4 carbon atoms, or an alkoxy, halogen or nitro, or heterocyclic aromatic or heterocyclic radical; and l, m, n, o, p, q, r, s, t and u are each independently 0 or an integer of from 1 to 5; , provided that at least two of l, m, n, o, p, q, r, s, t and u are not zero at any one time, wherein said heterocyclic aromatic radical or said heterocyclic radical is a 3-10 membered ring containing one or two heteroatoms selected from N, O or S.