PHTHALAZINONE DERIVATIVES

The use of a compound of the formula: and isomers, salts, solvates, chemically protected forms, and prodrugs thereof, in the preparation of a medicament for inhibiting the activity of PARP, wherein: A and B together represent an optionally substituted, fused aromatic ring; R c is represented by -L-R L , where L is of formula: -(CH 2 ) N1 -Q N2 -(CH 2 ) N3 - wherein n 1 , n 2 and n 3 are each selected from 0,1, 2 and 3, the sum of n 1 , n 2 and n 3 is 1, 2 or 3 and Q is selected from O, S, NH or C(=O); and RL is an optionally substituted C 5-20 aryl group; and R N is selected from hydrogen, optionally substituted C 1-7 alkyl, C 3-20 heterocyclyl, and C 5-20 aryl, hydroxy, ether, nitro, amino, amido, thiol, thioether, sulfoxide and sulfone. Novel compounds, and their use as pharmaceuticals, are also disclosed.