A compound with the formula I: wherein: R2 is of formula II: where A is a C5-7 aryl group, X is selected from the group comprising: NHNH2, CONHNH2, formula III, formula IV, and either: (i) Q1 is a single bond, and Q2 is selected from a single bond and &mdash；Z&mdash；(CH2)n&mdash；, where Z is selected from a single bond, O, S and NH and n is from 1 to 3； or (ii) Q1 is &mdash；CH&boxH；CH&mdash；, and Q2 is a single bond； R12 is a C5-10 aryl group, optionally substituted by one or more substituents selected from the group comprising: halo, nitro, cyano, ether, C1-7 alkyl, C3-7 heterocyclyl and bis-oxy-C1-3 alkylene； R6 and R9 are independently selected from H, R, OH, OR, SH, SR, NH2, NHR, NRR&prime；, nitro, Me3Sn and halo； where R and R&prime； are independently selected from optionally substituted C1-12 alkyl, C3-20 heterocyclyl and C5-20 aryl groups； R7 is selected from H, R, OH, OR, SH, SR, NH2, NHR, NHRR&prime；, nitro, Me3Sn and halo； either: (a) R10 is H, and R11 is OH, ORA, where RA is C1-4 alkyl； (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 SOzM, where z is 2 or 3 and M is a monovalent pharmaceutically acceptable cation； R&Prime； is a C3-12 alkylene group, which chain may be interrupted by one or more heteroatoms, and/or aromatic rings； Y and Y&prime； are selected from O, S, or NH； R6&prime；, R7&prime；, R9&prime； are selected from the same groups as R6, R7 and R9 respectively and R10&prime； and R11&prime； are the same as R10 and R11, wherein if R11 and R11&prime； are SOzM, M may represent a divalent pharmaceutically acceptable cation.Composé de formule I. Dans la formule I, R2 est de formule II : où A est un groupe aryle C5-7, X est choisi dans le groupe comprenant : NHNH2, CONHNH2, formule III, formule IV, et soit : (i) Q1 est une liaison simple, et Q2 est choisi parmi une liaison simple et -Z-(CH2)n-, où Z est choisi parmi une liaison simple, O, S et NH et n vaut de
