Dab₃₈₉IL2 diphtheria fusion toxin produces clinical responses in tumor stage cutaneous T cell lymphoma

Four patients with late stage cutaneous T cell lymphoma (IB-IVA) who had failed at least two previous therapies were treated with DAB₃₈₉IL2 at 9 or 18 μg/kg as 15-min intravenous infusions daily for 5 days every 3 weeks for eight cycles. Mild vascular leak syndrome (VLS) with transient edema, hypoalbuminemia, weight gain, and myalgias was observed in two of the patients lasting 7-10 days and only occurring on the first cycle. One stage IB patient had a pathologic complete remission (CR) lasting 11+ months from treatment initiation, one stage lib patient had a complete clinical remission (CCR) lasting >6 months with complete clearing of a large tumor lasting >18 months, and one stage lib and the one stage IVA patient had partial remissions (80-99% reduction in tumor masses) lasting 5 months. While IL2 receptor (IL2R) was expressed on 20-50% of tumor cells prior to therapy, recurrent tumor was IL2R negative in three of the patients. DAB₃₈₉IL2 at tolerable doses decreased tumor burden in each of these four standard treatment refractory CTCL patients and may offer an important alternative to standard palliative chemotherapy regimens.