Background/Purpose: For active rheumatoid arthritis (RA) patients with inadequate response to synthetic DMARDs, biologic agents, such as TNF inhibitor and IL-6 receptor inhibitor, are indicated. However, all biologics are very expensive, and, therefore all patients with high disease activities always can not receive biologics. Indeed, the interval of administration is fixed in most of biologics, but the interval is flexible in some biologics such as etanercept and infliximab. Tocilizumab (TCZ) is one of useful biologics, and the interval of TCZ infusion is fixed for 4 weeks. In the course of treating active RA patients by TCZ with 4 weeks interval, sometimes we experienced that longer interval was also effective. In preliminary study, we found that six weeks interval was effective in these patients. The present study is carried out to clarify the efficacy of six weeks interval of TCZ infusion in the patients with active RA.

Methods: The patients who showed inadequate response to DMARDs and the patients who showed inadequate response to biologics other than TCZ and who agreed with TCZ therapy of six weeks interval were enrolled in the present study. In addition to oral medicines, the patients were infused 8mg/kg of tocilizumab in every six weeks (SIWETO study). The clinical assessments and blood tests were also carried out in every 6 weeks. To the patients who did not achieve clinical remission by 6 weeks interval of TCZ, prednisolone (PSL) and/or methotrexate were added with increasing the dose. The patients who achieved clinical remission in 12 months were estimated as responder and others were as non-responders. We followed up the patients at least for 3 years. 

Results: Total of 74 patients was enrolled in the present study. Male and female were 18 and 56 respectively. Forty-four patients achieved clinical remission with 6w interval, and the rest of the patients were non-responder. To the patients who did not achieve clinical remission with 6w interval, TCZ infusion with 5w or 4w interval was carried out. Nineteen patients achieved clinical remission by 5w interval and four patients by 4w interval, respectively. The rest of 7 patients could not achieve clinical remission by TCZ infusion. In 44 patients who achieved clinical remission with 6w interval of TCZ infusion, 10 patients were treated by TCZ alone without any oral medicines for rheumatoid arthritis and kept the condition throughout the observation and the rest of patients received either or both PSL (1 to 7.5 mg) and MTX (2 to 8mg). It is generally accepted in Japanese rheumatologist that the effective dose of MTX in Japanese is lower than that in Caucasian. Severe adverse events including tuberculosis and death were not found. The frequency of other adverse events of 6w interval of TCZ was less than those of regular use (4w interval).  

Conclusion: The SIWETO study provides evidence that 6w interval of TCZ infusion is also effective in active rheumatoid arthritis patients. The finding of SIWETO study is quite useful for taking care of active rheumatoid arthritis patients, especially in financial aspects. The cost of 6 weeks interval of TCZ became two thirds of that of 4 weeks regular use.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/trial-of-six-weeks-interval-of-tocilizumab-infusion-in-patients-with-rheumatoid-arthritis/