First patient enrolled in phase III clinical trial of fostamatinib

Rigel Pharmaceuticals, Inc. announced that it has enrolled the first patient in a pivotal Phase III clinical trial of fostamatinib disodium hexahydrate (fostamatinib) in warm antibody autoimmune hemolytic anemia (AIHA). The clinical trial protocol calls for approximately 80 patients in a 24-week study with topline results projected for early 2021. This disorder affects an estimated 40,000 patients in the U.S., for whom no approved treatment options currently exist.

The Phase III clinical trial of fostamatinib is a placebo-controlled study of approximately 80 patients with primary or secondary warm AIHA who have failed at least one prior treatment. The primary endpoint will be a durable hemoglobin response by week 24, defined as Hgb > 10 g/dL and > 2 g/dL greater than baseline and a durability of response measure, with the response not being attributed to rescue therapy. Enrollment is expected to take approximately 12 months. In Rigel's SOAR Phase II clinical trial evaluating the safety and efficacy of fostamatinib in patients with warm AIHA who did not receive a meaningful benefit from at least one previous treatment, 9 out of 21 evaluable patients (43%) achieved the primary efficacy endpoint at week 24. One additional patient was a late responder at week 30, for a total of 10 out 21 evaluable patients (48%) that achieved a response. The primary endpoint was defined as a hemoglobin level of greater than 10 g/dl and at least a 2 g/dl increase from baseline. The safety profile was consistent with the existing fostamatinib safety database, including diarrhea and hypertension as the most common adverse events. The open-label extension period of the SOAR Phase II study is ongoing.

Currently, fostamatinib is commercially available in the U.S. under the brand name Tavalisse (fostamatinib disodium hexahydrate), 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.