A compound of formula I or a pharmaceutically acceptable salt or solvate thereof, or a conjugate thereof, wherein R has formula III, where A is a Saryl group, X is or NHR, where R is selected from the group consisting of H and C1-6 alkyl, and either , Q is selected from a single bond and —Z— (CH) -, where Z is selected from a single bond, O, S, and NH and n is from 1 to 3； or (ii) Q represents -CH = CH- and Q represents a single bond； R5 is a Caryl group； substituted by a group selected from OH, COH, COR, where R is selected from C1-6 alkyl； R1 and R4 are independently selected from H, R, OH, OR, SH, SR, NH, NHR, NRR ', nitro, MeSn, and halogen； where R and R 'are independently selected from the optionally substituted C1-6 alkyl, C2 heterocyclyl and Caryl groups； R is selected from H, R, OH, OR, SH, SR, NH, NHR, NHRR ', nitro, MeSn and halogen； either: (a) R 2 is H and R 1 is OH, OR, where R 2 is C 1-6 alkyl； (b) R and R form a nitrogen-carbon double bond between the nitrogen and carbon atoms to which they are attached； or (c) R 2 is H and R 3 is SOM, where z is 2 or 3 and M is a monovalent pharmaceutically acceptable cation； R "is a C1-6 alkylene group whose chain can be interrupted by one or more heteroatoms, for example O, S, NR, where R1 is H or C1-6 alkyl, and / or aromatic rings, for example benzene or pyridine； or NH； R, R, R selected from the same groups as R, R and R, respectively, and R and R represent the same groups as R and R, where, if R and R represent SOM, M may be a bivalent pharmaceutically acceptable cation.Соединение формулы Iили его фармацевтически приемлемая соль или сольват, или его конъюгат, где R2 имеет формулу III,где А представляет собой С5-7арильную группу, X представляет собой или NHRN, где RN выбран из группы, включающей Н и С1-4алкил, и либо (i) Q1 представляет собой одинарную связь, Q2 выбран из одинарной связи и -Z-(CH2)n-, где Z выбран из одинарной связи, О, S и NH и n составляет от 1 до 3； или (ii) Q1 представляет собой -СН=СН- и Q
