APO866 is novel drug that induces cell death by specifically inhibiting the biosynthesis of NAD+ from niacinamide, which is essential for the cellular metabolism, protein modification (e.g. PARP mediated DNA repair, sirtuins (histone deacetylation)) and Calcium dependent messenger synthesis. APO866 is not subject to the commonly known mechanisms of MDR. Its activity is cell cycle independent. APO866 exerted high anti-tumor activity on a broad range of different tumor cells derived from both human solid cancers and leukemias in vitro and on large number of human xenografts in nude mice and rats in vivo. Hematologic cancer cells were highly sensitive to APO866. Lymphocytes are the most sensitive normal cells to APO866 resulting to lymphocytopenia and reticulocytopenia in rats, monkeys and cancer patients. Furthermore, APO866 may have anti-angiogenic properties as shown in vivo and in patients.