Conjugate compounds of formula (A): wherein: R2 is where R36a and R36b are independently selected from H, F, C1-4 saturated alkyl, C2-3 alkenyl, which alkyl and alkenyl groups are optionally substituted by a group selected from C1-4 alkyl amido and C1-4 alkyl ester or, when one of R36a and R36b is H, the other is selected from nitrile and a C1-4 alkyl ester； R6 and R9 are independently selected from H, R, OH, OR, SH, SR, NH2, NHR, NRR&prime；, NO2, Me3Sn and halo； R7 is independently selected from H, R, OH, OR, SH, SR, NH2, NHR, NRR&prime；, NO2, Me3Sn and halo； Y is selected from formulae A1, A2, A3, A4, A5 and A6: L is a linker connected to a cell binding agent； CBA is the cell binding agent； n is an integer selected in the range of 0 to 48； RA4 is a C1-6 alkylene group； either (a) R10 is H, and R11 is OH, ORA, where RA is C1-4 alkyl； or (b) R10 and R11 form a nitrogen-carbon double bond between the nitrogen and carbon atoms to which they are bound； or (c) R10 is H and R11 is OSOzM, where z is 2 or 3 and M is a monovalent pharmaceutically acceptable cation； R and R&prime； are each independently selected from optionally substituted C1-12 alkyl, C3-20 heterocyclyl and C5-20 aryl groups, and optionally in relation to the group NRR&prime；, R and R&prime； together with the nitrogen atom to which they are attached form an optionally substituted 4-, 5-, 6- or 7-membered heterocyclic ring； wherein R16, R17, R19, R20, R21 and R22 are as defined for R6, R7, R9, R10, R11 and R2 respectively； wherein Z is CH or N； wherein T and T&prime； are independently selected from a single bond or a C1-9 alkylene, which chain may be interrupted by one or more heteroatoms e.g. O, S, N(H), NMe, provided that the number of atoms in the shortest chain of atoms between X and X&prime； is 3 to 12 atoms； and X and X&prime； are independently selected from O, S and N(H).
