DNA-damage and NAD(+)-depletion are initial events in oxygen radical induced islet cell death

The NAD biosynthesis inhibitor APO866 has potent antitumor activity against hematologic malignancies

APO866 inhibits nicotinamide phosphoribosyltransferase (NMPRTase), a key enzyme involved in nicotinamide adenine dinucleotide (NAD) biosynthesis from the natural precursor nicotinamide. Intracellular NAD is essential for cell survival, and NAD depletion resulting from APO866 treatment elicits tumor cell death. Here, we determine the in vitro and in vivo sensitivities of hematologic cancer cells to APO866 using a panel of cell lines (n = 45) and primary cells (n = 32). Most cancer cells (acute myeloid leukemia [AML], acute lymphoblastic leukemia [ALL], mantle cell lymphoma [MCL], chronic lymphocytic leukemia [CLL], and T-cell lymphoma), but not normal hematopoietic progenitor cells, were sensitive to low concentrations of APO866 as measured in cytotoxicity and clonogenic assays. Treatment with APO866 decreased intracellular NAD and adenosine triphosphate (ATP) at 24 hours and 48 to72 hours, respectively. The NAD depletion led to cell death. At 96 hours, APO866-mediated cell death occurred in a caspase-independent mode, and was associated with mitochondrial dysfunction and autophagy. Further, in vivo administration of APO866 as a single agent prevented and abrogated tumor growth in animal models of human AML, lymphoblastic lymphoma, and leukemia without significant toxicity to the animals. The results support the potential of APO866 for treating hematologic malignancies.

The pharmacokinetics, toxicities, and biologic effects of FK866, a nicotinamide adenine dinucleotide biosynthesis inhibitor

BACKGROUND

FK866 is a potent inhibitor or NAD synthesis. This first-in-human study was performed to determine the maximum-tolerated dose, toxicity profile, and pharmacokinetics on a 96-h continuous infusion schedule.

MATERIALS AND METHODS

Twenty four patients with advanced solid tumor malignancies refractory to standard therapies were treated with escalating doses of FK866 as a continuous, 96-h infusion given every 28 days. Serial plasma samples were collected to characterize the pharmacokinetics of FK866. Further blood samples were collected for the measurement of plasma VEGF levels.

RESULTS

There were 12 women and 12 men with a median age of 61 (range 34-78) and a median KPS of 80%, received a 4-day of infusion of FK866 at dose levels of 0.018 mg/m2/h (n=3), 0.036 mg/m2/h (n=3), 0.072 mg/m2/h (n=3), 0.108 mg/m2/h (n=4), 0.126 mg/m2/h (n=6), and 0.144 mg/m2/h (n=5). Thrombocytopenia was the dose limiting toxicity, observed in two patients at the highest dose level and one patient at the recommended phase II dose of 0.126 mg/m2/h No other hematologic toxicities were noted other than mild lymphopenia and anemia. There was mild fatigue and grade 3 nausea; the latter was controlled with antiemetics and was not a DLT. Css (the mean of the 72 and 96 h plasma concentrations) increased in relation to the dose escalation. The study drug did not significantly affect plasma concentrations of VEGF. There were no objective responses, although four patients had stable disease (on treatment for 3 months or greater).

CONCLUSIONS

The recommended phase II dose is 0.126 mg/m2/h given as a continuous 96-h infusion every 28 days. The dose limiting toxicity of FK866 is thrombocytopenia. Pharmacokinetic data suggest an increase in the plasma Css in relation to the escalation of FK866.