The FDA granted approval to Sanofi's BTK inhibitor, rilzabrutinib, marking a critical expansion in Sanofi's immunology portfolio. Acquired through the $3.7 billion purchase of Principia Biopharma, rilzabrutinib targets immune thrombocytopenia, a rare hematologic disorder characterized by low platelet counts. This regulatory clearance underscores Sanofi's strategic commitment to rare immunological diseases and introduces a novel therapeutic option for patients.