The present invention relates to tetraaza phenalen-3-one compounds which inhibitpoly (ADP-ribose) polymerase (PARP) and are useful in the chemosensitizationof cancer therapeutics. The induction of peripheral neuropathy is a common side-effectof many of the conventional and newer chemotherapies. The present inventionfurther provides means to reliably prevent or cure chemotherapy- induced neuropathy.The invention also relates to the use of the disclosed PARP inhibitor compoundsin enhancing the efficacy of chemotherapeutic agents such as temozolomide.The invention also relates to the use of the disclosed PARP inhibitor compoundsto radiosensitize tumor cells to ionizing radiation. The invention also relatesto the use of the disclosed PARP inhibitor compounds for treatment of cancerswith DNA repair defects.
