Phase III study of R 788 (fostamatinib) meets primary endpoint in immune thrombocytopenia - Rigel Pharma

Rigel Pharmaceuticals announced that R 788 (fostamatinib), its oral spleen tyrosine kinase (SYK) inhibitor, met the primary endpoint in the first of two double-blind studies in the FIT Phase III clinical program for the treatment of adult chronic/persistent immune thrombocytopenia (ITP). The study (n=76) showed that 18% of patients receiving fostamatinib achieved a stable platelet response compared to none receiving a placebo control (p=0.0261). A stable platelet response was defined as achieving greater than 50,000 platelets per uL of blood on at least four of the last six scheduled visits between weeks 14 and 24 of treatment.

Patients who met the primary endpoint of this study typically had an increase in platelet counts to a level above 50,000/uL within the initial weeks of treatment, providing early feedback as to whether it was a viable option for treating their ITP. The results from the second FIT Phase III study are expected in October/November 2016. The most frequent adverse events were gastrointestinal-related, and the safety profile of the product was consistent with prior clinical experience, and no new or unusual safety issues were discovered.

All of the patients from this study who met the stable platelet response endpoint enrolled in the long-term, Phase III extension study and continued to maintain their platelet levels for months past the initial study period of 24 weeks. These data affirm similar results observed in two patients from the Rigel Phase II study of fostamatinib in ITP who have been taking fostamatinib for more than seven years and have maintained stable platelet levels over this extended time period.