Efficacy and Safety of Denileukin Diftitox-Cxdl, an Improved Purity Formulation of Denileukin Diftitox, in Patients With Relapsed or Refractory Cutaneous T-Cell Lymphoma

PURPOSE Denileukin diftitox (DD)-cxdl is a fusion protein comprising diphtheria toxin fragments A and B and human interleukin-2. This phase III, multicenter, open-label, single-arm registrational trial evaluated the efficacy and safety of DD-cxdl in patients with relapsed/refractory (R/R) cutaneous T-cell lymphoma (CTCL). PATIENTS AND METHODS In the main study, which followed a dose-finding lead-in, DD-cxdl was administered intravenously daily (5 days; 9 µg/kg/d once daily) every 21 days for up to eight cycles. Patients in the primary efficacy analysis set (PEAS) were required to have stage IA-IIIB CTCL (mycosis fungoides and/or Sézary syndrome) and at least ≥one previous systemic therapy. The primary efficacy end point was objective response rate (ORR) using the Global Response Score. Secondary end points were duration of response (DOR), time to response (TTR), skin tumor burden, and safety and tolerability. RESULTS The PEAS included 69 patients (median age, 64.0 years). The ORR was 36.2% (95% CI, 25.0 to 48.7), including 8.7% with complete response. The median DOR was 8.9 months (95% CI, 5.0 to not estimable), and the median (Q1-Q3) TTR was 1.4 (0.7-2.1) months. A total of 84.4% of patients showed decreased skin tumor burden, with 48.4% showing a ≥50% decrease. Treatment-emergent adverse events (TEAEs) of special interest, most of which were grade 1 or 2, included infusion reaction (73.9%), hypersensitivity (68.1%), hepatotoxicity (36.2%), and capillary leak syndrome (20.3% [grade ≥3, 5.8%]). Other common TEAEs were nausea (43.5%) and fatigue (31.9%). CONCLUSION Efficacy and safety results show that DD-cxdl would potentially fulfill a serious, unmet medical need for patients with R/R CTCL.