Rheumatoid arthritis (RA) is a progressive, systemic autoimmune disease characterized by inflammation of the lining of the joint (synovial membrane). This inflammation causes pain, stiffness and swelling. More disturbing is that, over a short period of time, the inflammation leads to irreversible joint destruction and disability. RA affects more than 21 million people worldwide with approximately 2.5 million people affected in the United States.

RA also shortens life expectancy by affecting major internal organ systems. Studies have shown that after 10 years, fewer than 50% of patients can continue to work or function normally on a day- to-day basis.

A study presented this past week at EULAR 2007, the Annual European Congress of Rheumatology in Barcelona, Spain reported the results of the first phase III trial of a new RA drug, tocilizumab, which will be marketed as Actemra in the United States.

Tocilizumab is a novel humanized anti human interleukin 6 (IL-6) receptor monoclonal antibody. Monoclonal antibodies are proteins that are produced to have the same structure and properties. In this case, the proteins have all been grown to block the effects of IL-6 by binding to a specific part of the antibody called the receptor. By doing this, the effects of IL-6, which are to promote inflammation, are eliminated. IL-6 is a cytokine involved in the pathogenesis of RA and by targeted blockage of this receptor, tocilizumab slows down the progression of rheumatoid arthritis.

The study involved 623 patients with sustained moderate to severe RA despite long standing treatment with methotrexate. Patients received 4mg/kg, 8mg/kg tocilizumab or placebo intravenously every four weeks for a period of 24 weeks. Patients were allowed concurrent treatment with methotrexate at their pre-study dose (10-25mg weekly). Treatment with all other disease modifying anti-rheumatic drugs (DMARDs) was discontinued at the beginning of the trial.

Significant improvement in symptoms was observed in all patients receiving tocilizumab and methotrexate compared to placebo and methotrexate.

Nearly half (43.9%) of rheumatoid arthritis (RA) patients receiving tocilizumab 8mg/kg, in addition to ongoing methotrexate therapy experienced a 50% improvement in symptoms at 24 weeks and more than one fifth achieved a 70% symptom improvement. These numbers are very impressive and compare favorably with the effects reported in the clinical trials of drugs such as Enbrel, Humira, and Remicade, which are drugs that are already in use in the U.S.

Adverse Events (AEs) were recorded throughout the duration of the trial with a similar AE profile reported in all three groups (8mg/kg, 4mg/kg and placebo). The AE profile of tocilizumab is consistent with data presented in previous studies with the treatment being generally well tolerated.

The results of this study will undoubtedly advance the probability that the drug will be approved by the FDA for use in the United States.