Sanofi’s rilzabrutinib has officially earnt orphan drug designation for IgG4-related disease in Japan

Sanofi has recently announced that The Ministry of Health, Labour and Welfare in Japan has granted orphan drug designation to rilzabrutinib, a novel, oral, reversible covalent Bruton’s tyrosine kinase inhibitor, for IgG4-related disease. There is still unmet medical need and limited treatment options in Japan for IgG4-RD, a rare, progressive, immune-mediated chronic condition in which the immune system attacks various tissues and organs leading to serious damage.

Note that Rilzabrutinib for the treatment of IgG4-RD was evaluated in a phase 2 study , and results were presented at the European Alliance of Associations for Rheumatology 2025 congress. In IgG4-RD patients, treatment with rilzabrutinib for 52 weeks led to a reduction in disease flares and other disease markers and minimised the need for glucocorticoid treatment. The safety profile of rilzabrutinib in the study was consistent with previous studies in other indications, with no new safety signals observed. Treatment-emergent adverse events reported by >10% of patients include diarrhoea, COVID-19, dizziness, dry mouth and nausea.

In addition, Rilzabrutinib is studied across multiple rare immune-mediated diseases. In 2025, it received approval for immune thrombocytopenia in the US, the EU, and the UAE. Additionally, rilzabrutinib is currently under regulatory review for ITP in Japan. Rilzabrutinib has received several expedited designations from global regulatory authorities for ITP, IgG4-RD, warm autoimmune hemolytic anemia and sickle cell disease.

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IgG4-related disease, rilzabrutinib, Sanofi, Sanofis rilzabrutinib