Immune Thrombocytopenic Purpura (ITP) is a blood disorder in which the immune system attacks and destroys platelets in the blood, resulting in an abnormally low platelet count. Rigel is focusing its ITP program on the chronic form of this disorder, targeting the underlying autoimmune cause of the disease, rather than stimulating platelet production. Approximately 100,000 people suffer from chronic ITP, with the majority of these cases in women. Antibodies, usually of the IgG type, mediate the platelet destruction in ITP. Fostamatinib has a novel mechanism of action, blocking IgG receptor signaling in both macrophages and B-cells. Rigel released initial results from its Phase 2 ITP trial showing that Fostamatinib (R788) increased platelet counts for a majority of the patients treated.