A method of treatment of a disease of the human or animal body mediated by PARP comprising administering to such a subject a therapeutically effective amount of a compound of formula: or an isomer, salt, solvate, chemically protected form, and prodrug thereof, wherein: A and B together represent an optionally substituted, fused aromatic ring; RC is represented by -L-RL, where L is of formula: —(CH2)n1-Qn2-(CH2)n3— wherein n1, n2 and n3 are each selected from 0, 1, 2 and 3, the sum of n1, n2 and n3 is 1, 2 or 3 and Q is selected from O, S, NH, C(═O) or —CR1R2—, where R1 and R2 are independently selected from hydrogen, halogen or optionally substituted C1-7 alkyl, or may together with the carbon atom to which they are attached form a C3-7 cyclic alkyl group, which may be saturated (a C3-7 cycloalkyl group) or unsaturated (a C3-7 cycloalkenyl group), or one of R1 and R2 may be attached to an atom in RL to form an unsaturated C3-7 cycloalkenyl group which comprises the carbon atoms to which R1 and R2 are attached in Q, —(CH2)n3— (if present) and part of RL; and RL is optionally substituted C5-20 aryl; and RN is selected from hydrogen, optionally substituted C1-7 alkyl, C3-20 heterocyclyl, and C5-20 aryl, hydroxy, ether, nitro, amino, amido, thiol, thioether, sulfoxide and sulfone.