Enhanced Responses To Fostamatinib As Second-Line Therapy And In Persistent Immune Thrombocytopenia (Itp) Patients

Introduction. Immune thrombocytopenia (ITP) is characterized by autoantibody-mediated platelet destruction resulting in thrombocytopenia and often at least a degree of bruising and bleeding. Platelet destruction occurs within activated macrophages that signal via spleen tyrosine kinase (SYK) following Fcγ receptor engagement by platelet-bound IgG antibodies. Fostamatinib is a SYK inhibitor, taken orally twice daily with or without food. In the three phase 3 clinical studies (2 randomized, controlled trials and 1 open-label extension study), 145 adults with ITP received fostamatinib. These patients had a median of 3 prior therapies (range 1-13) and a median of 8.4 years (range <1-53 years) since ITP diagnosis, making them the most difficult-to-treat ITP population studied thus far in registration trials. Since gaining FDA approval in April 2018, fostamatinib has been prescribed to a wide range of ITP patients, including those with persistent disease and those for whom fostamatinib is second-line therapy. We conducted a post hoc analysis of the phase 3 clinical study data in patients for whom fostamatinib was second-line therapy as well as in patients with earlier stage disease, eg ITP of duration <2 years.