Fostamatinib

Fostamatinib is an experimental drug candidate for the treatment of a variety of diseases, originally developed by Rigel Pharmaceuticals. The drug is administered orally as a disodium salt, and is a prodrug of the active compound tamatinib (R-406), which is an inhibitor of the enzyme spleen tyrosine kinase (Syk).

Fostamatinib has been in phase II trials for rheumatoid arthritis, autoimmune thrombocytopenia and lymphoma.

A phase II study of rheumatoid arthritis patients failing to respond to a biologic agent showed little efficacy as compared to placebo, but the drug was well tolerated. In patients with high inflammatory burden, measured by levels of C-reactive protein, ACR20 was achieved by a significantly higher portion of those in the fostamatinib group (42%) versus the placebo group (26%).

On June 4, 2013, Astra Zeneca announced they were giving up future development on the compound, and terminated their license with Rigel after early results from a Phase IIb study for rheumatoid arthritis. Astra Zeneca is estimated to lose $140 million as part of the contract termination. Rigel plans to now focus on ITP and start phase III clinical trials soon.