Efficacy and tolerability of tocilizumab in rheumatoid arthritis patients seen in daily clinical practice in Japan: Results from a retrospective study (REACTION study)

Tocilizumab, a humanized monoclonal antibody to the interleukin 6 (IL-6) receptor, was approved for use as rheumatoid arthritis (RA) therapy in Japan in 2008, but its efficacy and tolerability in daily practice has not yet been reported. We report the results of a multicenter retrospective study on the efficacy and safety of tocilizumab involving all patients (n = 229) who were started on tocilizumab therapy at three rheumatology institutes in Japan from April 2008 through to March 2009. Tocilizumab was infused every 4 weeks at a dose of 8 mg/kg according to the drug labeling. Among the 229 patients, 55% concomitantly received methotrexate (MTX) and 63% had previously received anti-tumor necrosis factor (TNF) therapy. Average disease activity score (DAS) 28 of all 229 patients significantly decreased from 5.70 to 3.25 after 24 weeks of therapy. A European League Against Rheumatism (EULAR) good response and DAS28 remission was achieved in 57.4 and 40.7% of the patients, respectively, at 24 weeks. White blood cell counts significantly decreased and liver enzymes and total cholesterol slightly but significantly increased; however, liver enzyme levels did not increase in patients without MTX. Tocilizumab was discontinued in 47 cases (20.5%) due to lack of efficacy (5.2%), adverse events (11.4%), and other reasons (3.9%). The overall retention rate at 24 weeks was 79.5%. Based on these results, we conclude that tocilizumab therapy in daily rheumatology practice appears to be highly efficacious and well tolerated among active RA patients, including the anti-TNF therapy-refractory population. Tocilizumab infusion is therefore applicable not only as an alternative approach for anti-TNF therapy-resistant patients, but also as primary biologic therapy for active RA patients.