Phase I trial with escalating doses of idarubicin and multidrug resistance reversal by short-course cyclosporin A, sequential high-dose cytosine arabinoside, and granulocyte colony-stimulating factor for adult patients with refractory acute leukemia.

BACKGROUND AND OBJECTIVES Patients with refractory acute myeloid or lymphoid leukemia (AML, ALL) were treated with a high-dose regimen comprising idarubicin (IDR) plus short-course cyclosporin A (CsA) as multidrug resistance type-1 (MDR1) blocking agent. The principal aim was to define the maximum tolerated dose (MTD) of IDR, which is reported to be a less MDR1-sensitive anthracycline. The short CsA infusion was patterned after the results of a previous in vitro study. DESIGN AND METHODS This was a phase I trial, in which eligible patients received high-dose cytarabine (HDAC) 3 g/m(2)/bd on days 1, 2 and 8, 9, and IDR 12.5-20 mg/m(2)/d on days 3 and 10, with increments of 2.5 mg/m(2)/d from the baseline per treatment group. Intravenous CsA infusion started 4 hours before IDR and lasted 12 hours. Recombinant granulocyte colony-stimulating factor (G-CSF) was added from day 11. IDR MTD was evaluated through analysis of regimen-related toxicity (RRT). RESULTS Eighteen patients were treated (16 AML, 2 ALL; MDR1+: 8/8 studied). Overall response rate was 61%. Toxicity was severe but manageable up to an IDR dose of 17.5 mg/m(2)/d, while grade 4 RRT developed with IDR 20 mg/m(2)/d. High-grade toxicity, not strictly regimen-related, was sometimes observed at lower IDR concentrations in patients with unresolved complications from prior extensive treatments. In keeping, the complete response (CR) rate was 92% (11/12) for patients with an ECOG performance score <2 compared to 0% (0/6) in the others (p=0.000). Apart from that, induction of markedly hypocellular, leukemia-free bone marrow on day 11 was associated with achievement of CR (13 evaluable: CR 8/10 vs 0/3, p=0.035). INTERPRETATION AND CONCLUSIONS IDR at 17.5 mg/m(2)/d (x2) can be associated with short-course CsA and HDAC for the management of refractory acute leukemias. While this regimen could deserve testing in a larger phase II trial, to document activity in MDR1+ disease, it remains important to select the most suitable patients in order to avoid the occurrence of life-threatening cumulative toxicity.