The invention provides a compound of the formula (1): or a salt, solvate, N-oxide or tautomer thereof； wherein either R1 is R1a and R2 is R2a； or R1 is R1b and R2 is R2b； provided that in each case at least one of R1 and R2 is other than hydrogen； R1a and R2a are the same or different and each is selected from hydrogen, C1-4 alkyl, C2-4 alkenyl and C2-4 alkynyl wherein the C1-4 alkyl is optionally substituted by C1-2 alkoxy； R1b and R2b are the same or different and are selected from hydrogen, C(O)NR4R5, C(O)R6 and C(O)OR6 where R6 is C1-4 alkyl, R4 and R5 are both C1-4 alkyl, or NR4R5 forms a 4 to 7 membered saturated heterocyclic ring optionally containing a second heteroatom ring member selected from O, N or S and oxidized forms of N and S, the heterocyclic ring being optionally substituted by one or two C1-4 alkyl groups and/or one or two oxo groups； and R3 is a group D: wherein the asterisk denotes the point of attachment to the isoindoline ring； but excluding acetic acid 5-acetoxy-4-isopropyl-2-[5-(4-methyl-piperazin-1-ylmethyl)-1,3-dihydro-isoindole-2-carbonyl]-phenyl ester.
