Rilzabrutinib (WAYRILZ™) is a small-molecule, reversible, highly specific, covalent BTK inhibitor being developed by Sanofi for the treatment of multiple immune-related and inflammatory disorders, including immune thrombocytopenia, warm autoimmune haemolytic anaemia, sickle cell disease, IgG4-related disease, asthma, chronic spontaneous urticaria, among others. As a BTK inhibitor, rilzabrutinib demonstrates multiple immunomodulatory effects, including reduced B cell activation and autoantibody production, inhibition of macrophage activity, and anti-inflammatory effects. In clinical trials, rilzabrutinib was associated with durable platelet responses in patients with previously treated immune thrombocytopenia. This article summarizes the milestones in the development of rilzabrutinib leading to its first approval for the treatment of adults with persistent or chronic immune thrombocytopenia who have had an insufficient response to previous treatment.