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Title: Single-agent Rituximab May Prove Effective and Safe for Chronic Thrombocytopenia Purpura: Presented at NHL

"Single-agent Rituximab May Prove Effective and Safe for Chronic Thrombocytopenia Purpura: Presented at NHL"

By Chris Berrie PRAGUE, CZECH REPUBLIC -- September 15, 2004 -- One course of single-agent rituximab appears to induce a lasting, substantial response in adults with chronic immune thrombocytopenia purpura (ITP), according to a study presented here September 11th at The Role of Immunotherapy in NHL: Optimising Treatment Outcomes, sponsored by Roche. "The standard common treatment for patients with ITP includes a variety of chemotherapy agents, corticosteroids, and splenectomy", explained Nicola Cooper, MD, haematology specialist registrar, department of rheumatology, University College Hospital, London, United Kingdom. However, these therapies have limitations, such as moderate efficacy, significant rate of toxicities, and a high rate of relapse, for which there is no curative treatment. Rituximab has a B-cell depleting effect; the agent has therefore been suggested as a treatment for severe autoimmune conditions. Dr. Cooper reported on his team's recently published study (Cooper et al. Brit J Haematol. 2004;125:232-9) which evaluated rituximab for treatment of ITP. Through a combined analysis of 2 individual phase 1/2 trials based in the United States and Italy, a total of 57 patients with chronic ITP were included in this single-agent rituximab assessment. Of note, there were no differences in response to therapy between the 2 studies, thus allowing this combination. The rituximab regimen involved a dose of 375 mg/m[² weekly for 4 weeks.

All the patients had platelet counts below 30x 10⁶/L at baseline, all had received 2 or more previous ITP treatments, and 54% had undergone splenectomy.

Following the rituximab regimen, the overall response rate (ORR) of 72% comprised 32% in complete response (CR; platelet count >150x 10⁶/L), and 23% in partial remission (PR; platelet count 50-150x 10⁶/L). Furthermore, some 75% of the CR and PR patients responded to retreatment.

"What was interesting and surprising was that with the patients who had a complete response to treatment, there were 3 distinct patterns," said Dr. Cooper. These were an early platelet response with normalisation of platelet counts within 1 week of treatment (39%); little early response but an acute increase in the platelet counts between weeks 4 to 8 (28%); and a slow, steady increase in platelet counts that reached normalisation of platelet counts by week 31 (33%). The duration of these responses were directly related to their magnitudes.

Among the patients who achieved a CR, 91% remained in complete remission after a median follow-up of 72.5 weeks. According to subset analysis, there was no effect of splenectomy on the likelihood of response, and the only factor that affected response was early treatment of the disease.

Overall, this single-agent rituximab regimen was well tolerated by the patients chronic ITP, with 58% experiencing grade 1/2 adverse events, and 2% with grade 3. Despite circulating B-cells dropping to below 0.03x 10⁶/L, there were also no infectious complications.

Dr. Cooper concluded that the combination of these highly effective responses to single-agent rituximab treatment for adults with chronic ITP with other recent evidence of its efficacy in autoimmune haemolytic anaemia underscore the need for further studies to define the optimal use of rituximab in the treatment of these autoimmune diseases.

[Presentation title: Use of Rituximab in ITP and Haemolytic Anaemia. Abstract 517]

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