A phase I and pharmacodynamic study of sequential topotecan and etoposide in patients with relapsed or refractory acute myelogenous and lymphoblastic leukemia

Abstract We designed a pharmacokinetic and pharmacodynamic phase I study of sequential topotecan (2.55–6.3 mg/m 2 ) by 72 h infusion followed by five daily doses of etoposide for patients with refractory acute leukemia based upon synergistic anti-tumor activity of topoisomerase I and II inhibitors in vitro. Eight of the 29 patients achieved bone marrow aplasia and two patients achieved clinical remission. Common grade 3–4 toxicities included hepatic and gastrointestinal dysfunction, and correlated with increased steady-state plasma topotecan concentration. The predicted up-regulation of topoisomerase II activity by topoisomerase I inhibition was not observed at this dose and schedule and may provide insight into the modest anti-leukemia activity of the regimen.