Pyrrolobenzodiazepines and conjugates thereof

A compound of formula (E):

• and salts and solvates thereof, wherein
• the dotted lines indicate the optional presence of a double bond between C1 and C2 or C2 and C3;
• R2 is independently selected from H, OH, ═O, ═CH2, CN, R, OR, ═CH—RD, ═C(RD)2, O—SO2—R, CO2R and COR, and optionally further selected from halo or dihalo;
• where RD is independently selected from R, CO2R, COR, CHO, CO2H, and halo;
• R6 and R9 are independently selected from H, R, OH, OR, SH, SR, NH2, NHR, NRR′, NO2, Me3Sn and halo;
• R7 is independently selected from H, R, OH, OR, SH, SR, NH2, NHR, NRR′, NO2, Me3Sn and halo;
• R8 is independently selected from H, R, OH, OR, SH, SR, NH2, NHR, NRR′, NO2, Me3Sn and halo;
• RL is a linker for connection to a cell binding agent;
• Q is independently selected from O, S and NH;
• R11 is either H, or R or, where Q is O, R11 is SO3M, where M is a metal cation;
• R and R′ are each independently selected from optionally substituted C1-12 alkyl, C3-20 heterocyclyl and C5-20 aryl groups, and optionally in relation to the group NRR′, R and R′ together with the nitrogen atom to which they are attached form an optionally substituted 4-, 5-, 6- or 7-membered heterocyclic ring;
• or any pair of adjacent groups from R6 to R9 together form a group —O—(CH2)p—O—, where p is 1 or 2;
• or the compound is a dimer with each monomer being of formula (E), or with one monomer being of formula (E) and the other being of formula (B):
• wherein R2, R6, R9, R7, and R8 are as defined according to the compounds of formula (A), and the R7 groups or R8 groups of each monomer form together a dimer bridge having the formula —X—R″—X— linking the monomers;
• wherein R″ is a C3-12 alkylene group, which chain may be interrupted by one or more heteroatoms, e.g. O, S, N(H), NMe and/or aromatic rings, e.g. benzene or pyridine, which rings are optionally substituted by NH2;
• and each X is O, S or N(H);
• and where the compound is a dimer with each monomer being of formula (E), the group RL in one of the monomers is either a capping group, RC, or is a linker for connection to a cell binding agent.