Cellular ara-CTP pharmacokinetics, response, and karyotype in newly diagnosed acute myelogenous leukemia

We evaluated relationships between ara-CTP pharmacokinetics in myeloblasts, response, and karyotype in 147 patients with newly diagnosed AML treated on three protocols each initiated by a 3 g/m2 ara-C dose given over 2 h. Area under the curve of ara-CTP concentration times time (AUC) or peak ara-CTP concentration after this dose did not predict response or response duration, suggesting that inability to form ara-CTP is an unlikely mechanism of ara-C resistance. Following high-dose bolus ara-C therapy patients with INV [16] or del [16q] had long remissions despite low AUC and peak values while patients with -5, del [5q], -7, or del [7q] were frequently resistant despite average AUC and peak values. In 55 patients treated with high-dose continuous infusion ara-C as a single agent, steady-state ara-CTP concentrations were significantly lower in resistant patients (who again were disproportionately those with -5, del [5q], -7, or del [7q]) although there was no correlation with CR duration.