Treatment of Acute Myelogenous Leukemia (non-APL) with Intravenous Trisenox® (Arsenic Trioxide) and Ascorbic Acid: Preliminary Results.

Introduction: Arsenic trioxide (ATO) is an exceptionally active drug in acute promyelocytic leukemia (APL), inducing complete remissions in 85% of relapsed patients. ATO also has clinical activity in myelodysplastic syndrome (MDS). In non-APL AML cells lines, ATO induces apoptosis in vitro ; however, in a small study of 11 non-APL AML patients, ATO showed no activity (Parmer et al Leuk Res28:090, 2004). In some types of cancer cells, ATO-induced apoptosis has been shown to correlate inversely with the level of intracellular reduced glutathione (GSH) via generation of reactive oxygen species; cells with high concentrations of GSH are more resistant to ATO. Ascorbic acid (AA) increases apoptosis and overcomes resistance to ATO in multiple myeloma, non-APL AML and other cell lines by reducing intracellular GSH levels. AA alone has no activity in these cells. We therefore conducted a clinical trial in patients with non-APL AML combining ATO and AA. Methods: ATO at a dose of 0.25 mg/kg is administrated intravenously over 1–3 hour with 1 gram of intravenous AA given within 30 minutes daily for five days a week (five days on/2 days off) for five weeks (25 doses - one cycle). These doses were based on a phase I/II trial of ATO+AA in patients with multiple myeloma (Behalis et al Clin Cancer Res8:3658, 2002)). Responding patients receive an additional consolidation cycle of 25 doses followed by maintenance of two weeks of every month of ATO+ AA for 4 cycles. Patients who fail to respond after two cycles are considered treatment failures. Results : Seven patients have so far enrolled: three (aged 36,52,59) had relapsed after chemotherapy, and four aged 66–84 (median 70), never received chemotherapy. For these untreated patients ATO+AA was given as front line treatment. In three of the four previously untreated patients the number of bone marrow blasts dropped from > 40% to Conclusion: These preliminary results in patients with non-APL AML suggest that: (1) AA +ATO has anti-leukemia activity in untreated non-APL AML patients with minimal toxicity; (2) more than one cycle is probably needed to achieve a response in the peripheral blood counts; (3) in non-APL AML, ATO can cause the so called “differentiation syndrome” which should be anticipated and treated early. If confirmed in additional patients, ATO+AA might be a less toxic alternative upfront approach to intensive chemotherapy in elderly patients with non-APL AML.