The present invention relates to methods for decreasing cellular DNA repair ina target patient；decreasing cellular NAD+ biosynthesis in a target patient； increasingefficiency of radiationtherapy in a target patient； modulating nicotinamide phosphoribosyltransferase activity in apatient； or sensitizing a patient to a DNA damaging therapy. The inventionrelates to methodsfor treating a patient who received a toxic dose of a nicotinamidephosphoribosyl transferaseinhibitor. Theinvention also relates to pharmaceutical compositions comprising aphysiologically acceptable carrier； an effective amount of a NMPRT inhibitor；and nicotinicacid. The invention also relates to methods for treating a patient diagnosedwith or suspectedto have cancer deficient in nicotinic acid pathway.
