A Study of APO866 for the Treatment of Cutaneous T-cell Lymphoma

CTCL is the most frequent occurring cutaneous non-Hodgkin lymphoma characterized by an indolent and protracted course of patches, plaques and tumors. It is highly symptomatic, debilitating, disfiguring and impacting on the patient's quality of life. The treatment strategy for CTCL is based on the exact diagnosis including the stage of disease and aims to preserve cellular immune function, while achieving an anti-tumor effect. Given the nature of the disease and the cumulative and additive toxicities of treatments used, the intensity and duration of long-term therapy is limited. 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. APO866 has shown to induce, at low nM level, growth inhibition of human Myla CTCL cells as well as in human subcutaneous xenografts of Myla CTCL in Balb-C nude mice. APO866 was investigated in 24 patients with advanced cancers in a phase I study aiming to determine the DLT and MTD. Treatment was well tolerated and safe. The unique DLT was thrombocytopenia. At dose levels higher than 0.036 mg/m2/hr CTC grade III lymphocytopenia, thought not be clinically relevant, preceded all other toxicities. The recommended dose for phase II studies of APO866 is 0.126 mg/m2/hr administered by civ infusion for 4 consecutive days (MTD). This dose was selected because of its safety profile, and the translational observation that Css of APO866 at MTD was similar or higher as compared to the concentrations at which efficacy was established in vitro and in vivo. No objective tumor response was observed. However, 4 patients had stable disease for at least 3 months: prostate cancer (4 months), melanoma (5 months), sarcomatoid mesothelioma (3 months) and oropharyngeal cancer (5 months). In addition, lesion size reductions were observed in the melanoma patient (80% size reduction and stable size of other lesions) at an APO866 dose level of 0.072 mg/m2/hr, and in the mesothelioma patient (moderate size reductions of pleural lesions) at 0.108 mg/m2/hr. Treatment with APO866 was safe and well tolerated. The anti-tumor effect of APO866, in particular on hematological cancer cells in vitro and ex vivo, and its lymphocytopenic effect in patients support the rationale to conduct an open phase II study of APO866 in patients with refractory or relapsed CTCL qualifying for systemic chemotherapy