Arsenic trioxide: Pharmacokinetics in acute promyelocytic leukemia (APL) patients.

7055 Background: Arsenic (As) has significantly increased survival for APL patients. As and its metabolites’ effects on cell proliferation, apoptosis, and methylation, especially long term, remain largely unknown. It is imperative to study the pharmacokinetics of As at therapeutic doses in order to limit untoward effects resulting from treatment. Arsenic trioxide (ATO), available as arsenous acid (iAsIII), is readily metabolized through sequential methyl group additions and electron reduction steps: iAsIII →MAsV →MAsIII →DMAsV →DMAsIII →TMAsVO →TMAsIII. iAsIII, MAsIII and DMAsIII are more biologically active and more toxic than pentavalent forms. The key enzyme involved is arsenic methyltransferase, and polymorphisms contribute to metabolic differences between individuals. Methods: Cancer patients not treated with ATO (controls) had one collection of blood and urine samples, while APL patients receiving therapeutic doses of ATO had collections immediately prior to and at 1, 2, 4, 6, and 24 hours, days 4, ...