Investigational BTK Inhibitor Receives FDA Orphan Drug Designation For 2 Rare Diseases

The FDA has granted orphan drug designation to rilzabrutinib for the treatment of warm autoimmune hemolytic anemia (wAIHA) and IgG4-related disease (IgG4-RD), according to a press release from Sanofi. Currently, there are no approved medications for both rare diseases.¹

Rilzabrutinib an investigational, novel, advanced, oral, reversible Bruton’s tyrosine kinase (BTK) inhibitor, is also under regulatory review in the U.S., the European Union, and China for the treatment of immune thrombocytopenia (ITP).¹

Efficacy and safety results of rilzabrutinib in patients with wAIH were presented at the 66th American Society of Hematology Annual Meeting & Exposition. Of 21 patients with primary wAIH, 14 (64%) achieved overall hemoglobin (Hb) response, including three (14%) with complete response and nine (41%) with durable response. Rilzabrutinib also led to a clinically meaningful improvement in fatigue. According to the Functional Assessment of Chronic Illness Therapy (FACIT)-fatigue scale, the overall mean baseline of 30.0 (11.1) increased to 36.4 (10.5) at 12 weeks of treatment and 37.0 (11.5) at 24 weeks.²

Nineteen (86%) patients experienced on-treatment adverse events (AEs), and 10 (45.5%) patients had treatment-related AEs. The most common AEs were nausea (32%), diarrhea (23%), and upper abdominal pain (18%), and were all mild grade.²

For patients with IgG4-RD, 52 weeks of rilzabrutinib treatment reduced disease flare, other disease markers, and glucocorticoid sparing. The safety profile was consistent with previous data.¹ Detailed results are expected to be presented at an upcoming medical meeting, according to Sanofi.

References

1. Press Release: Rilzabrutinib granted orphan drug designation in the US for two rare diseases with no approved medicines. News Release. Sanofi. April 3, 2025. Accessed April 7, 2025. https://www.sanofi.com/en/media-room/press-releases/2025/2025-04-03-05-00-00-3054815
2. Cooper N, Kuter DJ, Frederiksen H, et al. Part a efficacy and safety of oral bruton tyrosine kinase inhibitor (BTKi) rilzabrutinib in patients with warm autoimmune hemolytic anemia (wAIHA): multicenter, open-label, phase 2b study. Presented at: 66th American Society of Hematology Annual Meeting & Exposition. December 7-10, 2024; San Diego, CA.