Efficacy and safety of extending intravenous tocilizumab intervals from 4 to 6 weeks in rheumatoid arthritis patients with good response to 4-week intervals

A period of 4 weeks (w) has been recommended for rheumatoid arthritis (RA) patients as the interval between intravenous (IV) tocilizumab (TCZ, 8 mg/kg). In a previous paper, we showed the possibility that the interval between successive IV TCZ can be extended from 4 to 6 weeks in more than 60% of patients with low diseases activity (LDA) at 4-week intervals. Herein, we aimed to investigate the efficacy and safety of extending the interval from 4 to 6 weeks. A retrospective observational study was conducted by enrolling patients in whom the intervals of TCZ infusions could be extended from 4 to 6 weeks with an LDA for more than 2 years. We compared the efficacy and side effects of TCZ infusions at intervals of 4 and 6 weeks in a cohort of patients. We also examined serum lipid, platelet, IL-6, and trough TCZ levels. A total of 125 patients with an LDA at 4 weeks intervals were enrolled in this study, of which 78 patients maintained LDA at 6-week intervals of TCZ infusion. After extending the infusion intervals, the efficacy of the treatment was maintained, and the side effects decreased significantly. In addition, the levels of total cholesterol and triglyceride were returned to normal, and the serum trough levels of TCZ became undetectable at 6-week intervals. We proved that intervals between TCZ infusions can be extended from 4 to 6 weeks in more than 60% of RA patients along with a decrease in the side effects, thus suggesting the need to change the infusion intervals in suitable patients.