Denileukine Diftitox for Relapsed ALCL

Despite significant progress in the treatment and outcome for childhood ALCL, the prognosis for children who develop progressive or recurrent disease is poor with \< 30% DFS. Novel therapies are urgently needed for these subgroups of patients. One potential approach is the investigation of a new class of receptor targeted cytotoxic fusion proteins (denileukin diftitox{DD}). We have previously demonstrated that \> 85% of children with ALCL express CD25. The human IL-2 receptor exists in three forms, low (CD25), intermediate (CD122/CD132) and high (CD25/CD122/CD132) affinity. DD is a recombinant DNA-derived cytotoxic fusion protein composed of the amino acid sequences for diphtheria toxin fragments followed by the binding sequences for the interleukin-2 receptor. Malignant cells expressing one or more of the subunits of the IL-2 receptor are found in certain leukemias and lymphomas including cutaneous T-cell lymphoma (CTCL). Clinical studies have shown therapeutic efficacy of DD alone and in combination with CHOP chemotherapy in CD25 expressing malignancies such as CTCL, CLL and lymphoma. We hypothesize that DD will be safe and efficacious in children with relapsed ALCL.