Background/Purpose:  The treatment of active rheumatoid arthritis (RA) patients are usually started with synthetic disease modifying antirheumatic drugs (DMARDs), but when adequate response are not achieved, biologics DMARDs are introduced. Tocilizumab (TCZ) is one of useful biologics and the infusion dose of TCZ was settled at 8mg/kg. The residues of TCZ fluid were always discarded. The procedure of sucking and discharging of TCZ is troublesome and dispose of TCZ residue is uneconomical. The fixed dose injection become majority of biologics administration, but fixed dose of biologics infusion has not been attempted to date. The present study is carried out to clarify that one vial (400mg) of TCZ infusion per body (body weight >50kg) is effective in the patients with active RA.

Methods: The RA patients who showed inadequate response to synthetic and biologic  DMARDs other than TCZ and whose body weight was between 50 to 100kg were enrolled in the present study. The patients discontinued biologics before starting TCZ, and one vial (400mg) per body infusion of tocilizumab every 4 weeks (OBOTO study) was added to synthetic DMARDs. The clinical assessments and blood tests were also carried out every 4 weeks. To the patients who did not achieve clinical remission by one vial (400mg) of TCZ, prednisolone (PSL) and/or methotrexate were added. The patients who achieved clinical remission in 12 months were estimated as responder and others were as non-responders. To the patients who achieved clinical remission, we tapered the dose of PSL and/or DMARDs. We followed up the patients at least for 5 years.

Results: Total of 106 patients was enrolled in the present study. Male and female were 25 and 81 respectively. Seventy-four patients achieved good response, 21 patients achieved moderate response and 11 patients were non-responders. DAS28 remission was achieved in 59 patients. The body weight of the patients enrolled was between 92 to 50 kg and the mean body weight of responders and non-responders did not differ significantly. After the clinical remission was achieved, PSL and/or DMARDs were decreased. In five years, 12 patients were treated TCZ alone without any synthetic DMARDs or corticosteroids and kept the condition more than 4 years. The rest of responders received either or both PSL (1 to 7.5 mg/day) and MTX (2 to 8mg/week). To the patients who could not achieve clinical remission, dose escalation of TCZ was not attempted in the present study. Serious adverse events including tuberculosis or death were not found. The overall incidence of adverse events of one vial (400mg) of TCZ was less than those of 8mg/kg infusion.  

Conclusion: We provide evidence that one vial (400mg) of TCZ infusion is effective in active RA patients whose body weight is over 50 kg. The finding of OBOTO study is quite useful for taking care of active RA patients both financially and technically.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/study-of-one-vial-400mg-per-body-infusion-of-tocilizumab-in-patients-with-active-rheumatoid-arthritis/