Compounds of formula I: A-B-C  (I)and isomers, salts, solvates, chemically protected forms, and prodrugs thereof wherein: B is selected from the group consisting of:  where RN is H or Me; or B is a divalent C5 heterocyclic residue containing one or two ring heteroatoms; A is: RA3 and RA5 are independently selected from halo, ORO and RAC, where RO is H or Me, and RAC is H or C1-4 alkyl; XA is selected from N and CRA4, where RA4 is selected from H, ORO, CH2OH, CO2H, NHSO2Me and NHCOMe; RA2 and RA6 are independently selected from H, halo and ORO; or RA3 and RA4 together with the carbon atoms to which they are attached, or RA2 and RA3 together with the carbon atoms to which they are attached, may form a C5-6 heterocylic or heteroaromatic ring, containing at least one nitrogen ring atom; where if X is not N, 1, 2, or 3 of RA2 to RA6 are not H; C is:  where X is selected from N and CH, Y is selected from N and CH, and Z is selected from N and CRC6; RC3 is selected from H, halo and an optionally substituted N-containing C5-7 heterocyclic group; RC5 is a group selected from:  which group may be selected by one or two C1-4 alkyl groups or a carboxy group; RC6 is H; or, when X and Y are N, RC5 and RC6 (when Z is CRC6) together with the carbon atoms to which they are attached may form a fused C6 aromatic ring selected from the group consisting of: