The FDA has approved rilzabrutinib, a BTK inhibitor acquired by Sanofi through the $3.7 billion acquisition of Principia Biopharma. The drug is indicated for immune thrombocytopenia, a rare disease characterized by low platelet counts. This approval aligns with Sanofi’s immunology strategy and expands treatment options for patients with this condition. The clearance marks a significant milestone in rare disease therapeutics and reinforces Sanofi’s portfolio in immunology.