Fostamatinib (Rigel Pharmaceuticals), an oral investigational spleen tyrosine kinase (SYK) inhibitor, has met the primary endpoint in the first of two phase 3, double-blind studies involving adults with chronic/persistent immune thrombocytopenia (ITP). Eighteen percent of patients receiving fostamatinib achieved a stable platelet response compared with none receiving placebo (P = 0.0261). Results from the second phase 3 study are expected in October or November 2016.
In general, the clinical goal of ITP treatment is to increase platelet counts to more than 50,000/uL. Patients who met the primary endpoint in the new study had their platelet counts rise from a median of 16,000/uL at baseline to a median of more than 100,000/uL at week 24.
All of the patients who met the stable platelet response endpoint enrolled in a long-term, phase 3 extension study and continued to maintain their platelet levels for months past the initial study period of 24 weeks. These data reflect similar results observed in two ITP patients from a phase 2 study of fostamatinib who have been taking fostamatinib for more than seven years and have maintained stable platelet levels over this extended period.
If the results from the new phase 3 trial are reproduced in the second trial and are supported by the results of a planned interim analysis of the phase 3 extension study, Rigel Pharmaceuticals expects to submit a new drug application to the FDA in the first quarter of 2017.
Fostamatinib is an oral investigational drug with a mechanism of action designed to inhibit SYK kinase, a key player in the immune process that leads to platelet destruction in ITP. The FDA has granted an orphan drug designation to fostamatinib for the treatment of patients with ITP. Unlike other therapies that modulate the immune system or stimulate platelet production, fostamatinib is believed to address the underlying autoimmune basis of ITP by impeding platelet destruction.
Source: Rigel Pharmaceuticals; August 30, 2016.