Rationale: Some therapies for cancer target both healthy and diseased cells in the body. Newer treatments have a more targeted approach that focus on tumor cells, including the drug offered in this study called denileukin diftitox. This drug targets specific receptors on malignant cells while minimizing damage to normal cells not expressing the receptor. Denileukin Diftitox attaches to the cell surface of T-cell lymphocytes, which most commonly cause skin lymphomas. Previous studies have demonstrated denileukin diftitox’s ability to kill certain leukemia and lymphoma cells due to the drug’s ability to attach to the T-cell lymphocytes and a protein called CD25. Some T-cell lymphocytes have the protein CD25 on their cell surface, while others do not. CD25 helps to create an immune response. Denileukin Diftitox is already approved for persistent or recurrent T-cell lymphoma with malignant cells that express CD25. The current study will test denileukin diftitox in patients with cutaneous T-cell lymphoma to gain information about treatment efficacy for patients who are CD25 positive or CD25 negative.

Treatment: Patients in this study will receive denileukin diftitox. This drug will be administered through intravenous infusions. Denileukin diftitox will be given for five consecutive days. This schedule will be repeated every three weeks. Several tests and exams will be conducted throughout the study, including imaging exams before each five day treatment period with denileukin diftitox. Treatments will be discontinued due to disease growth or unacceptable side effects. Patients responding to denileukin diftitox will continue receiving the drug on the same schedule. Those with a complete response will receive one additional five day treatment. All patients will be closely monitored.