Rituximab pharmacokinetics in children and adolescents with de novo intermediate and advanced mature B-cell lymphoma/leukemia: A Children’s Oncology Group (COG) report.

Abstract

3055 Background: The COG trial ANHL01P1 was undertaken to determine pharmacokinetics (PK) and safety following the addition of rituximab (R) to FAB/LMB 96 chemotherapy in children and adolescents with stage III/IV mature B-NHL and B-ALL±CNS disease. Methods: Patients received R (375mg/m2) on day -2 and 0 of two induction cycles and day 0 of two consolidation cycles. R levels were measured prior to any antibody infusion, during induction cycles (1 hour prior and 30-60 minutes after each R dose) and following consolidation cycles (1, 3, 6 and 9 months after last R dose). R was measured by ELISA with goat anti-rituximab antibody as the capture reagent and goat anti-mouse IgG-conjugated to horseradish peroxidase as the detection reagent. R terminal half-life (t½) was calculated if at least 3 time points after the last dose were measurable in an individual subject. Results: Serum R levels are reported in the Table. Highest peak levels were achieved following the second dose of each induction cycle with sustained troughs and a t½ of 26-29 days. Group C patients tended to have lower R levels than Group B. Patients with LDH ≥2xULN were noted to have lower R levels during induction 1 compared to those with LDH <2xULN. Children (<13 years) exhibited higher peak concentrations, similar trough levels and a shorter t½ than adolescents (≥13 years). None of these differences reached significance after adjusting for multiple comparisons. Conclusions: R can be safely added to FAB chemotherapy with high early R peak/trough levels and a long terminal half-life. The efficacy of R combined with FAB chemotherapy is currently being investigated in an ongoing international intergroup trial. Clinical trial information: NCT00057811. [Table: see text]