Background/Purpose: A period of 4 weeks (w) has been recommended as the interval between tocilizumab (TCZ) infusions. The cost of TCZ is very high, which makes it difficult for all patients to receive TCZ because of the associated expenses. Treating the patients with TCZ, we experienced that longer intervals than 4w were also effective. We examined whether the intervals between TCZ infusions could extend from 4w to 6w or 5w.

Methods: The RA patients who had shown good response and sustained low disease activity (LDA) with 8mg/kg of TCZ infusions at 4w intervals were enrolled in the study. To the eligible patients, the intervals between TCZ infusions were extended to 5w at the same TCZ dose (8mg/kg). For the patients who could maintain LDA for 6 months and more at 5w interval of TCZ infusion, the intervals between TCZ infusions were extended to 6w. We followed the patients up for 2 years and more. Good response and LDA was defined as DAS-28CRP EULAR criteria.

Results: One hundred patients were enrolled in the present study, and 96 patients completed the study. 93 patients maintained LDA with 8mg/kg of TCZ infusion every 5w for 6 months and more and the rest of 7 patients could not keep LDA and the intervals between TCZ infusions were shortened to 4w. The 93 patients who maintained LDA with 8mg/kg of TCZ infusion every 5w were received 8mg/kg of TCZ infusion every 6 weeks, and 62 patients maintained LDA with 6w-interval. After 2 years follow-up, 96 patients could maintain LDA and 4 patients were dropped from the study. Among 96 patients who could maintain LDA, the intervals between TCZ intervals were 6w in 62 patients, 5w in 28 patients, and 4w in 6 patients, indicating that 90% of patients who had shown good response and sustained LDA with 4w intervals could extend the intervals between TCZ infusions from 4w to 5w or 6w. The mean baseline DAS28-CRP score in patients who could maintain LDA with TCZ infusions at 6w intervals were 2.2 and was significantly lower than that at 4 weeks interval (2.6). The frequency of adverse events with TCZ infusions at 6 weeks intervals was lower than that at 4 weeks intervals.

Conclusion: The present study provides evidence that most of RA patients who showed good response to TCZ infusions at 4w and sustained LDA could extend the intervals to 6w or 5w. This finding should be of great interest for both financial and labor reasons.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/tocilizumab-infusion-intervals-can-be-extended-to-5-or-6-weeks-in-ra-patients-who-sustained-low-disease-activity-by-4-weeks-interval-of-tocilizumab-infusion/