Predictors of complete responses with denileukin diftitox in cutaneous T-cell lymphoma

The clinical course of cutaneous T-cell lymphoma (CTCL) is typically chronic, often progressive, and variably response to existing therapeutic interventions. To date, few controlled clinical trials demonstrate durable complete responses (CR) in advanced-stage patients. Denileukin diftitox (DD) is a recombinant fusion protein targeting the interleukin-2 receptor of malignant cells. Of 263 relapsed and refractory CTCL patients treated with denileukin diftitox in three prospective, randomized Phase II and III clinical trials, 24 (9.1%) patients attained a durable complete response lasting beyond 3.6 years. This study evaluated the characteristics of the complete responders in these trials. CR patients had received a mean of 3.6 prior therapies. There was no difference in the frequency of CR based on stage of disease, dose of DD (9 vs. 18 mg/kg/day) (P = 0.646) or between CD25-positive and CD25-negative patients (P = 1.00). Response durations were 57-1,325+ days in the CD25-positive group and 190-400+ days in the CD25-negative group. These studies demonstrate that DD therapy resulted in durable complete responses in a subset of patients with early and advanced CTCL and CD25-positive and CD25-negative disease.