Fostamatinib (R788) is a prodrug rapidly converted to its active metabolite on 
oral administration. This (known as R406) is a potent inhibitor of spleen 
tyrosine kinase, required for the expression of a number of proinflammatory 
cytokines. Fostamatinib has shown significantly superior efficacy (when compared 
with placebo) in the control of patients with rheumatoid arthritis not 
responding to methotrexate in Phase II clinical trials. Treatment emergent 
adverse events with a higher frequency than in those on placebo included 
diarrhea, hypertension, urinary tract infections, neutropenia and elevated 
transaminases. The studied doses have shown a linear pharmacokinetic pattern and 
the administration of methotrexate does not affect it. Fostamatinib may have a 
role in the therapy of patients with rheumatoid arthritis with poor response to 
conventional therapy. If these results are confirmed once Phase III studies are 
completed, it may find a place in the evolving treatment algorithm for 
rheumatoid arthritis.