A multicenter, retrospective study in patients with multiple sclerosis treated with natalizumab in a real-world...

Natalizumab (TYSABRI^Ⓡ) is known to be an efficacious treatment at a standard-interval dosing (SID; 300 mg administered intravenously every 4 weeks) for patients with relapsing-remitting sclerosis (RRMS). However, the SID of natalizumab is associated with increased risk of progressive multifocal leukoencephalopathy (PML). Lengthening the time between doses of natalizumab beyond 4 weeks, also known as extended-interval dosing (EID), is associated with lower risk of PML in patients with RRMS, and patients have been switched from SID to EID without meaningful loss of efficacy. In this multicenter, retrospective, observational study, REFIND, we examined real-world natalizumab dosing patterns and MS disease activity in patients with RRMS in Japan.

REFIND retrospectively collected data from medical records of patients at 20 study centers in Japan. Patients with MS aged 20 years and older who received at least one dose of natalizumab after January 1, 2018, and had at least one clinical assessment were included. The primary endpoints were dosing patterns used in clinical practice and MS disease activity by dosing patterns. SID was defined as a mean natalizumab dosing interval ≤35 days, and EID was defined as a mean natalizumab dosing interval ≥36 to ≤84 days. Dosing pattern groups included SID-only, EID-only, or SID followed by EID (SID/EID). For each dosing pattern group, the annualized relapse rate (ARR) before and after administration of natalizumab was compared using a negative binomial regression model.

Of the 203 patients with MS eligible for inclusion in the REFIND study, 120 patients with RRMS were treated with natalizumab for ≥1 year, with a mean ± standard deviation (SD) age of 36.0 ± 9.4 years and a mean ± SD administration period of 32.8 ± 18.8 months. Among these patients, 13 had an SID-only natalizumab dosing pattern, 49 had EID-only, and 58 had SID/EID, with mean ± SD dosing intervals of 30.8 ± 1.6 days, 45.9 ± 3.4 days, and 38.7 ± 3.4 days, respectively. Overall ARR 1 year before vs 1 year after initiation of natalizumab was 1.03 vs 0.12 (P < 0.0001). ARR before vs after natalizumab in the SID-only group was 1.08 vs 0.62 (P = 0.378), in the EID-only group was 0.95 vs 0.02 (97.9% reduction, P = 0.0005), and in the SID/EID group was 1.08 vs 0.09 (91.7% reduction, P < 0.0001). Proportions of patients with new or enlarging T2 lesions in the SID-only, and the EID-only, and SID/EID groups were reduced by 89.1%, 83.5%, and 95.7%, respectively, after natalizumab initiation compared with the year before natalizumab.

The significant reduction in ARR observed with EID or SID/EID suggests that there is little difference between these dosing regimens in this retrospective dataset in Japan. The effectiveness of natalizumab in reducing the number of new or enlarging T2 lesions was similar across all dosing groups and consistent with known high efficacy of natalizumab in controlling disease activity. These real-world data on natalizumab EID in Japan may help inform treatment choices for Asian populations.