4-Heteroarymethyl substituted phthalazinone derivatives

Disclosed is a 4-Heteroarymethyl substituted phthalazinone derivatives of formula (I) where the variables are as disclosed in the description. Also disclosed is a pharmaceutical composition containing a compound of formula (I) and the use of a compound of formula (I) to prepare a medicament for (a) preventing poly(ADP-ribose) chain formation by inhibiting the activity of cellular PARP (PARP-1 and/or PARP-2); (b) the treatment of: vascular disease; septic shock; ischemic injury, both cerebral and cardiovascular; reperfusion injury, both cerebral and cardiovascular; neurotoxicity, including acute and chronic treatments for stroke and Parkinson's disease; haemorrhagic shock; inflammatory diseases, such as arthritis, inflammatory bowel disease, ulcerative colitis and Crohn's disease; multiple sclerosis; secondary effects of diabetes; as well as the acute treatment of cytoxicity following cardiovascular surgery or diseases ameliorated by the inhibition of the activity of PARP; or (c) use as an adjunct in cancer therapy or for potentiating tumour cells for treatment with ionizing radiation or chemotherapeutic agents or for the treatment of cancer which is deficient in Homologous Recombination (HR) dependent DNA double strand break (DSB) repair activity.