Denileukin diftitox (trade name Ontak) is an antineoplastic agent, an engineered protein combining Interleukin-2 and Diphtheria toxin. This can bind to Interleukin-2 receptors and introduce the diphtheria toxin into cells that express those receptors, killing the cells. In some Leukemias and Lymphomas malignant cells express these receptors, so denileukin diftitox can target these.
A recent study at the University of Louisville found the drug caused many stage IV cutaneous T-cell lympomas to regress or stabilize extending patient life expectancy from about eight months to more than a year; a clinically significant increase especially given the guarded prognosis of patients with advanced disseminated cutaneous T-cell lymphoma (CTCL) and the generally poor response to other available treatments.
There is some evidence tying it to vision loss and in 2006 the FDA added a black box warning to the drug's label.
^Turturro F (2007). "Denileukin diftitox: a biotherapeutic paradigm shift in the treatment of lymphoid-derived disorders". Expert Rev Anticancer Ther7 (1): 11–7. doi:10.1586/1473722.214.171.124. PMID17187516.