Rigel Pharmaceuticals, Inc. today announced the publication of data in the American Journal of Hematology from the open label, multicenter, Phase 2 clinical study of fostamatinib in adults with warm antibody autoimmune hemolytic anemia (wAIHA) who had failed at least one prior treatment. The published data demonstrate that fostamatinib, an oral spleen tyrosine kinase (SYK) inhibitor, rapidly and durably increased hemoglobin (Hgb) levels, with clinically meaningful Hgb responses observed in nearly half of the patients, and a safety and tolerability profile consistent with the existing fostamatinib safety database of patients across multiple disease programs studied. The publication, entitled “Fostamatinib for the treatment of warm antibody autoimmune hemolytic anemia: Phase 2, multicenter, open-label study”, is available on the journal website.
“The results observed in our Phase 2 study in warm autoimmune hemolytic anemia reinforce the potential of fostamatinib to help patients with this rare, serious blood disorder for whom no disease-targeted therapies are currently approved,” said Raul Rodriguez, Rigel’s president and chief executive officer. “If approved, fostamatinib has the potential to be the first-to-market therapy for patients with wAIHA in 2023 and would be fostamatinib’s second approved indication.”
The Phase 2 study evaluated the response to fostamatinib at 150 mg BID (twice daily) in adult patients with wAIHA and active hemolysis with Hgb of less than 10 g/dL who had failed at least one prior treatment. The primary endpoint was Hgb greater than 10 g/dL with an increase of ≥2 g/dL from baseline by Week 24 without rescue therapy or red blood cell transfusion. The study demonstrated that 46% (11/24) of patients achieved the primary endpoint, with 1 late responder at week 30 (total of 12 responders [50%]). Increases in median Hgb were detected at Week 2 and sustained over time. The most common adverse events (AEs) were diarrhea (42%), fatigue (42%), hypertension (27%), dizziness (27%), and insomnia (23%). AEs were manageable and consistent with the fostamatinib safety database of over 3,900 patients across multiple diseases (rheumatoid arthritis, B-cell lymphoma, COVID-19, and immune thrombocytopenia (ITP)). No new safety signals were detected.