Natalizumab (NTZ) is a highly effective disease modulatory treatment for relapsing-remitting multiple sclerosis (RRMS). Post-marketing surveillance is important for evaluation of long-term safety and effectiveness in a real-world setting. To this end, the “Immunomodulation and Multiple Sclerosis Epidemiology Study” (IMSE 1) was initiated upon NTZ launch in Sweden (August 2006).
To follow-up the long-term effectiveness and safety of NTZ in a real-world setting, with focus on patients treated at least 10 years.
IMSE 1 includes patients starting NTZ treatment and data is collected from the nationwide Swedish Neuro Registry (NeuroReg). Adverse events (AEs), JC-virus status (JCV) and clinical effectiveness measures are registered in NeuroReg prospectively. Effectiveness measures were assessed using the Wilcoxon Signed Rank Test.
A total of 3291 patients were included in the IMSE 1 study from August 2006 until June 2020 (72% female; mean age 36 years; 80% RRMS; mean treatment duration 50 months). 171/3291 patients (5%) had been treated for at least 120 months (73% female; men age 36 years; 87% RRMS; mean treatment duration 139 months). A total of 64% (110/171) were treated with interferons or glatiramer acetate prior to NTZ treatment. Over the duration of follow-up discontinued 21% (35/171) their NTZ treatment of which 46% (16/35) discontinued due to JCV positive (JCV+). In total, 27% (46/171) of these patients were JCV+ with a mean JCV index of 1.2±1.0 (4% missing data). The mean number of relapses were reduced from 0.84 one year before NTZ treatment start to 0.00 during the first treatment year (12% missing data). All clinical effectiveness measures (Extended Disability Status Scale (EDSS), Multiple Sclerosis Severity Scale (MSSS), Multiple Sclerosis Impact Scale (MSIS-29) and Symbol Digit Modalities Test (SDMT)) showed improvement in mean between baseline and 120 months. However, only MSSS, MSIS-29 psychological and SDMT were statistically significant. Over the entire observation time, 114 Serious AEs had been reported to the Swedish Medical Product Agency and included nine cases (2 fatal) of progressive multifocal leukoencephalopathy (PML) of which eight between year 2008 and 2012, and one in 2018. 17 patients died during or within 6 months of last NTZ infusion. None were judged to be directly associated with NTZ.
NTZ is generally well tolerated with sustained effectiveness regarding cognitive, physical and psychological measures, as well as relapse-control.