French healthcare company Sanofi S.A. (Euronext Paris:SAN) (Nasdaq:SNY) announced on Monday that Japan's Ministry of Health, Labour and Welfare has granted orphan drug designation to rilzabrutinib, its oral, reversible covalent Bruton's tyrosine kinase inhibitor, for the treatment of IgG4-related disease (IgG4-RD).

This designation addresses a rare, progressive immune-mediated condition with limited treatment options in Japan.

Rilzabrutinib was evaluated in a phase 2 study in IgG4-RD patients, showing reductions in disease flares and markers over 52 weeks while minimising glucocorticoid use, with a safety profile consistent with prior studies. Common treatment-emergent adverse events included diarrhoea, COVID-19, dizziness, dry mouth, and nausea. The drug is currently being assessed in the RILIEF phase 3 study for IgG4-RD.

Rilzabrutinib has received multiple global orphan drug and expedited designations for IgG4-RD, immune thrombocytopenia (ITP), warm autoimmune haemolytic anaemia, and sickle cell disease, reflecting Sanofi's focus on rare immune-mediated diseases. It is approved for ITP in the United States, European Union, and United Arab Emirates, and is under review for ITP in Japan, while all other indications remain investigational.