The pharmaceutical firms Zenyaku Kogyo Co., Ltd. and Chugai Pharmaceutical Co., Ltd. have announced that Zenyaku has successfully secured regulatory authorization from Japan’s Ministry of Health, Labour and Welfare (MHLW) to expand the use of the anti-CD20 monoclonal antibody, Rituxan, for the treatment of “chronic idiopathic thrombocytopenic purpura in children.” This injectable drug, offered in 100 mg and 500 mg doses, is co-promoted by the two companies under the generic moniker rituximab (genetical recombination).
Until now, Rituxan had been endorsed solely for adult patients with certain dosage and administration protocols. The need for pediatric application emerged following a request from the Japanese Society of Paediatric Haematology/Oncology. Upon evaluation, their appeal qualified for a public knowledge-driven submission at the “58th Evaluation Committee on Unapproved or Off-label Drugs with High Medical Needs” in March 2024. A decision to permit the submission was later confirmed by the “Pharmaceutical Affairs Council’s First Committee on Drugs” in April 2024. Prompted by this, Zenyaku lodged a formal application on May 24, 2024, which subsequently received approval.
Idiopathic Thrombocytopenic Purpura (ITP) affects the autoimmune process by producing autoantibodies against platelet surface proteins, resulting in thrombocytopenia through heightened platelet destruction and reduced production. As a designated intractable disease (designated intractable disease 63) by the national authorities, the precise causes of ITP remain unidentified, with the autoantibody origin still under research.
While many children newly diagnosed with ITP exhibit considerable thrombocytopenia, serious bleedings, such as those occurring intracranially, are uncommon and tend to resolve themselves without treatment. An estimated 30-56% of cases, however, necessitate intervention particularly when resistant to first-line therapies like corticosteroids or intravenous immunoglobulin. Both national and international medical guidelines endorse Rituxan as a treatment option for pediatric ITP cases displaying such resistance.
Mechanistically, Rituxan is an anti-CD20 monoclonal antibody that targets CD20 proteins present on B cells, excluding hematopoietic stem cells and plasma cells. The drug uses the host’s immune system to attack and destroy these B cells. Given B cells’ potential role in ITP pathology, removing them with Rituxan could offer therapeutic benefits, particularly for cases resistant to initial treatments.
Zenyaku and Chugai remain committed to working closely to ensure that Rituxan continues to serve as an effective treatment for chronic ITP in both adult and pediatric populations.