Paris, March 2, 2026
Sanofi announced that Japan’s Ministry of Health, Labour and Welfare (MHLW) has granted orphan drug designation to rilzabrutinib, a novel oral Bruton’s tyrosine kinase (BTK) inhibitor, for the treatment of IgG4-related disease (IgG4-RD), a rare and progressive immune-mediated disorder with significant unmet medical need. The designation marks the third global orphan recognition for rilzabrutinib in IgG4-RD and reinforces Sanofi’s commitment to advancing therapies for rare immune-mediated diseases.
Japan Grants Orphan Drug Designation
The orphan drug designation was granted based on positive findings from a Phase 2 clinical study (NCT04520451) evaluating rilzabrutinib in patients with IgG4-RD. IgG4-RD is a chronic, relapsing autoimmune condition that can affect multiple organs, leading to irreversible tissue damage and, in severe cases, organ failure. In Japan, treatment options remain limited, making regulatory incentives for rare disease therapies particularly significant. Orphan designation in Japan provides development support, priority consultation, and extended market exclusivity, accelerating potential patient access.
Phase 2 Data Demonstrate Clinical Benefit
Results presented at the European Alliance of Associations for Rheumatology 2025 Congress showed that 52 weeks of rilzabrutinib treatment reduced disease flares and key disease markers, while also minimizing reliance on glucocorticoids. The safety profile was consistent with prior studies, with no new safety signals identified. Reported adverse events occurring in more than 10% of patients included diarrhea, COVID-19, dizziness, dry mouth, and nausea.Based on these findings, rilzabrutinib is now advancing into the RILIEF Phase 3 trial (NCT07190196) to further evaluate its efficacy and safety in IgG4-RD.
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Expanding Global Regulatory Footprint
Rilzabrutinib has already received regulatory approval for immune thrombocytopenia (ITP) in the United States, European Union, and United Arab Emirates. Regulatory review for ITP is currently ongoing in Japan, while additional expedited designations have been granted globally for other rare immune-mediated disorders including warm autoimmune hemolytic anemia (wAIHA) and sickle cell disease (SCD). These milestones position rilzabrutinib as a multi-indication immunology asset with growing global recognition.
Rilzabrutinib is a reversible covalent BTK inhibitor developed using TAILORED COVALENCY® technology, enabling selective BTK inhibition across B cells, macrophages, and innate immune pathways. By targeting a central regulator of immune activation, the therapy aims to restore immune balance without broad immunosuppression.
IgG4-RD remains difficult to diagnose and manage due to its rarity and multi-organ involvement. Patients experience recurrent inflammatory flare-ups, progressive fibrosis, and potential organ dysfunction. The development of targeted therapies like rilzabrutinib represents a critical advancement over conventional corticosteroid-based regimens, which are often associated with long-term safety concerns.
With this latest Japanese designation, Sanofi strengthens its strategic focus on rare immunology and precision-targeted therapies, expanding its regulatory and clinical footprint in Asia. As the global biopharmaceutical industry intensifies efforts in autoimmune and inflammatory disease innovation, rilzabrutinib’s continued advancement highlights the importance of orphan drug frameworks in accelerating development for underserved patient populations.
Source: Sanofi press release
