A compound of formula (I) or a salt or solvate thereof, wherein the dotted double bond indicates the presence of a single or double bond between C2 and C3； R2 is selected from &mdash；H, &mdash；OH, &boxH；O, &boxH；CH2, &mdash；CN, &mdash；R, OR, halo, dihalo, &boxH；CHR, &boxH；CHRR&prime；, &mdash；O&mdash；SO2&mdash；R, CO2R and COR； R7 is 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 C1-7 alkyl, C3-20 heterocyclyl and C5-20 aryl groups； R10 and R11 either together form a double bond, or are selected from H and QRQ respectively, where Q is selected from O, S and NH and RQ is H or C1-7 alkyl or H and SOxM, where x is 2 or 3, and M is a monovalent pharmaceutically acceptable cation； A is selected from (A1), (A2), (A3), (A4) or (A5) where X1 and Y1 are selected from: CH and NH； CH and NMe； N and NMe； CH and S； N and S； N and O； and CH and O, respectively； X2 and Y2 are selected from: CH and NH； CH and NMe； N and NMe； CH and S； N and S； N and O； and CH and O, respectively； Z1 is selected from O and S； Z2 is selected from CH and N； F is selected from a single bond and -(E-F1)m&mdash；； each E is independently selected from a single bond, and &mdash；C(&boxH；O)&mdash；NH&mdash；； each F1 is independently a C3-20 heteroarylene group； m is 1, 2 or 3； G is selected from hydrogen, C1-4alkyl, &mdash；C(&boxH；O)&mdash；O&mdash；C1-4alkyl, &mdash；(CH2)n&mdash；C3-20 heterocycloalkyl, and &mdash；O&mdash；(CH2)n&mdash；C3-20 heterocycloalkyl group； each n is 0-4； provided that A2 is not A2&prime；, where X1 and Y1 of A2&prime； are selected from: CH and NMe； COH and NMe； CH and S； N and NMe； N and S, respectively； and provided that A3 is not A3&prime；, where X2 and Y2 of A3&prime； are selected from: CH and NMe； COH and NMe； CH and S； N and NMe； N and S, respectively； B is either a single bond or (B1), where X and Y of B1 are selected from: CH and NMe； COH and NMe； CH and S； N and NMe； N and
