Rigel Finalizes Study Design of Fostamatinib Trial for Warm Autoimmune Hemolytic Anemia

Rigel Pharmaceuticals has reached agreement with the U.S. Food and Drug Administration (FDA) on the final design of its FORWARD study, a pivotal Phase 3 clinical trial of fostamatinib disodium hexahydrate (fostamatinib) in warm autoimmune hemolytic anemia (AIHA). The FDA agreed to Rigel's proposed durable response measure for the primary efficacy endpoint as well as the inclusion of additional secondary endpoints.

The Phase 3 clinical trial is a randomized, double-blind, placebo-controlled study of approximately 90 patients with primary or secondary warm AIHA who have failed at least one prior treatment. The primary efficacy endpoint for the trial is a durable response defined as a hemoglobin level ≥ 10 g/dl with an increase from baseline of ≥ 2 g/dl on three consecutive available visits during the 24-week treatment period, with the response not being attributed to rescue therapy. This endpoint allows for missed visits due to the COVID-19 pandemic without impacting a durable outcome. As of November 5, the trial had enrolled 57 of the 90 patients targeted for enrollment and currently has over 90 clinical trial sites established across 22 countries.

"Our conversations with the FDA have enabled us to finalize the primary efficacy endpoint for the only ongoing Phase 3 trial in warm AIHA, a condition for which there is no approved therapy," said Raul Rodriguez, Rigel's president and CEO. "We are over 60% of our enrollment target despite the headwinds drug development is facing due to COVID-19. We believe this progress is a result of the geographic diversity of our clinical sites, the ability of fostamatinib to be given orally, and the FDA's clinical trial guidance during the pandemic."

Fostamatinib is commercially available in the U.S. under the brand name TAVALISSE® (fostamatinib disodium hexahydrate) tablets, which is the first and only spleen tyrosine kinase (SYK) inhibitor indicated for the treatment of thrombocytopenia in adult patients with chronic ITP who have had an insufficient response to a previous treatment. The FDA has granted TAVALISSE Orphan Drug designation for the treatment of patients with warm AIHA.

Autoimmune hemolytic anemia (AIHA) is a rare, serious blood disorder in which the immune system produces antibodies that result in the destruction of the body's own red blood cells. AIHA affects approximately 45,000 adult patients in the U.S. and can be a severe, debilitating disease. Warm AIHA (wAIHA), the most common form of AIHA, is characterized by the presence of antibodies that react with the red blood cell surface at body temperature. To date, there are no disease-targeted therapies approved for AIHA, despite the unmet medical need that exists for these patients.

TAVALISSE® (fostamatinib disodium hexahydrate) tablets is indicated for the treatment of thrombocytopenia in adult patients with chronic immune thrombocytopenia (ITP) who have had an insufficient response to a previous treatment.