Parallel Phase I Studies of Daunorubicin Given With Cytarabine and Etoposide With or Without the Multidrug Resistance Modulator PSC-833 in Previously Untreated Patients 60 Years of Age or Older With Acute Myeloid Leukemia: Results of Cancer and Leukemia Group B Study 9420

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Abstract
PURPOSE: The Cancer and Leukemia Group B conducted parallel phase I trials of cytarabine, daunorubicin, and etoposide (ADE) with or without PSC-833 (P), a modulator of p-glycoprotein–mediated multidrug resistance. PATIENTS AND METHODS: One hundred ten newly diagnosed patients ≥ 60 years of age with de novo acute myeloid leukemia (AML) were treated. All patients received cytarabine by continuous infusion for 7 days at 100 mg/m2/d. The starting dose of daunorubicin was 30 mg/m2/d for 3 days. Etoposide was administered at a dose of 100 mg/m2/d for 3 days, except in the last cohort administered ADEP, who received 60 mg/m2. PSC-833 was given intravenously with a loading dose of 1.5 mg/kg over 2 hours and a simultaneous continuous infusion of 10 mg/kg/d continued until 24 hours after the last dose of daunorubicin or etoposide. RESULTS: There was no toxicity attributed to the PSC-833. Dose-limiting toxicity was primarily gastrointestinal (diarrhea, mucositis in the ADEP group). The estimated maximum-tolerated doses, calculated using a logistic regression model, were daunorubicin 40 mg/m2/d for 3 days with etoposide 60 mg/m2 for 3 days in the ADEP group and daunorubicin 60 mg/m2/d for 3 days and etoposide 100 mg/m2/d for 3 days in the ADE group. Twenty-one (48%) of 44 patients achieved complete remission with ADE, compared with 29 (44%) of 66 patients treated with ADEP. CONCLUSION: It is necessary to decrease the doses of daunorubicin and etoposide when they are administered with PSC-833, presumably because of the effect of the modulator on the pharmacokinetics of these agents. A phase III trial comparing the regimens derived from this phase I trial has recently begun.