A phase II study of DT fusion protein denileukin diftitox in patients with fludarabine-refractory chronic lymphocytic leukemia.

DAB(389)IL2 produced a rapid decrease of leukemic cells in the bone marrow and peripheral blood of most chemotherapy refractory CLL patients. Most patients also tolerated DAB(389)IL2 well, without significant myelosuppression and/or immunosuppression. The prolonged progression-free interval and subjectively observed quality-of-life in responders is intriguing. The results suggest DAB(389)IL2 has biological activity in patients with B-cell CLL. Follow-up studies of combinations or altered schedules or doses to improve the response rate are warranted.