ORLANDO, Florida—Rituximab (Rituxan) shows promise in the treatment of immune thrombocytopenic purpura (ITP), according to two poster presentations at the 43rd Annual Meeting of the American Society of Hematology (ASH). Nichola Cooper, MRCP, fellow, and James B. Bussel, MD, professor of pediatrics, both at Weill Medical College of Cornell University, and Mansoor N. Saleh, MD, professor of medicine at the University of Alabama at Birmingham, reported the results of separate studies investigating the efficacy and toxicity of rituximab(Drug information on rituximab) in adults with refractory ITP. Rituximab binds to the antigen CD20 and depletes circulating B-lymphocyte cells. "In theory," Dr. Cooper said, "if you get rid of the B cells, it decreases the autoimmune response."
Cornell Study
The Cornell team administered rituximab at 375 mg/m² once a week for 4 weeks to 23 patients who were refractory to at least one prior ITP treatment, had a platelet count of less than 30,000/µL, and were not infected with the human immunodeficiency virus (HIV). Twenty-one patients were evaluable after more than 9 weeks since the first infusion.
Ten patients (47%) had a good response to the drug, obtaining platelet levels of more than 50,000/µL on two counts, 1 week apart. In eight of these patients (38% of the total study population), ITP completely resolved, with platelet levels of more than 150,000/µL on both counts.
Patients responded at different rates, some earlier in treatment and others later. One person who responded to the drug relapsed 48 weeks after her first infusion and was successfully retreated. The trial demonstrated rituximab’s effectiveness in adults who have failed steroid treatment but have not undergone splenectomy.
"The most important finding is the long duration of activity and the low toxicity to patients," Dr. Cooper said. "Some patients go longer than a year without [additional] treatment and maintain counts above 50,000/µL. Most are up to normal levels."
Patients in both studies experienced infusion reactions, including red face, hives, pruritus, and throat discomfort, but no other side effects were noted. "The fact that there was no infection and no decrease in immunoglobulins is surprising," Dr. Cooper said. "We’re always concerned about long-term consequences but don’t know what they may be."
