Clinical activity of a cytotoxic fusion protein in the treatment of cutaneous T-cell lymphoma.

PURPOSE: A phase I trial in patients with refractory hematologic malignancies was performed at our institution to test the clinical relevance of the selective cytotoxic activity of the interleukin-2 (IL-2)-diphtheria toxin fusion protein, DAB486IL-2. A subset of five patients from this trial, all with cutaneous T-cell lymphomas (CTCL), forms the basis of this report. PATIENTS AND METHODS: Two treatment schedules were used. One patient received DAB486IL-2 at a dose of 0.075 mg/kg/d intravenous (i.v.) bolus over 15 minutes daily for 5 consecutive days. The other four patients received DAB486IL-2 at a dose of 0.1 mg/kg as an i.v. infusion over 180 minutes weekly for 5 consecutive weeks. RESULTS: Three of the five CTCL patients achieved significant tumor responses. One patient attained a complete clinical and pathologic response (CR), which has been sustained without any interval treatment for 33+ months. Two other patients achieved partial responses (PRs) of 17+ and 4 months' duration, respectively. Treatment was well tolerated. The most common adverse effect was a transient increase in hepatic transaminases experienced by all five patients. CONCLUSION: The growth factor-cytotoxin fusion protein DAB486IL-2 demonstrated significant clinical activity with acceptable toxicity in a group of heavily pretreated patients with CTCL.