Sanofi’s Rilzabrutinib Granted Orphan Drug Status in Japan for IgG4-Related Disease
Tuesday, March 03, 2026
Sanofi has received orphan drug designation in Japan for rilzabrutinib for the treatment of IgG4-related disease (IgG4-RD). The designation was granted by Japan’s Ministry of Health, Labour and Welfare for medicines intended to treat rare conditions with high unmet medical need.
IgG4-RD is a rare, progressive and immune-mediated chronic disease in which the immune system attacks different tissues and organs, potentially leading to serious and sometimes irreversible damage. Treatment options remain limited in Japan.
Rilzabrutinib is a novel, oral, reversible covalent Bruton’s tyrosine kinase (BTK) inhibitor. It was evaluated in a Phase II study (NCT04520451), with results presented at the European Alliance of Associations for Rheumatology 2025 congress. In patients with IgG4-RD, 52 weeks of treatment reduced disease flares and other disease markers, while lowering the need for glucocorticoid therapy. The safety profile was consistent with earlier studies in other indications, and no new safety concerns were reported. The most common treatment-emergent adverse events, reported in more than 10% of patients, included diarrhoea, COVID-19, dizziness, dry mouth and nausea.
The therapy is currently being assessed in the Phase III RILIEF study (NCT07190196) for IgG4-RD.
Rilzabrutinib is under development across several rare immune-mediated diseases. In 2025, it was approved for immune thrombocytopenia (ITP) in the United States, the European Union and the United Arab Emirates. Regulatory review for ITP is ongoing in Japan. The drug has also received expedited designations globally for ITP, IgG4-RD, warm autoimmune haemolytic anaemia and sickle cell disease. Apart from the approved ITP indications in the US, EU and UAE, other uses remain investigational.
IgG4-RD is a relapsing condition that can affect almost any organ. It is characterised by periods of flare-ups and may lead to organ failure if not properly managed. Due to its rarity and diagnostic challenges, its global prevalence is not clearly defined.
Source: sanofi.com
