Till Örebro universitet

Introduction: 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 (Aug 2006).

Objectives/Aims: To follow-up  the  long-term  effectiveness  and  safety of NTZ in a real-world setting.

Methods: Adverse  events  (AEs),  Serious  AEs  (SAEs),  John  Cunningham  virus status  (JCV)  and  clinical  effectiveness  measures; Extended Disability Status Scale (EDSS), Multiple Sclerosis Severity  Scale  (MSSS),  Symbol  Digit  Modalities Test  (SDMT)  and Multiple Sclerosis Impact Scale (MSIS-29) data is collected from  the nationwide Swedish Neuro Registry (NeuroReg). Effectiveness measures were assessed using the Wilcoxon Signed Rank Test.

Results: A total of 3622 NTZ patients were included in the IMSE 1 study from August 2006 until March 2022 (72% female; mean age  36  years;  80%  RRMS; mean  treatment  duration  49  months)  and  186  had  been  treated  for  at  east  132  months.  Of  the  132-month cohort, 73% were female, the mean age was 36 years, 88% had  RRMS,  and  the  mean  treatment  duration  was  155 months.  The majority were treated with interferons and glatiramer acetate prior NTZ  (64%).  25%  (47/186)  discontinued  NTZ  treatment  of  which 47% (n=22) discontinued due to JCV positive (JCV+). In total,  30%  (55/186)  of  these patients  were  JCV+  with  a  mean  JCV index of 1.2±1.0 (2% missing data). Relapses before treatment were reduced from 380/1000 patient years to 43/1000 during treatment,  71%  were  relapse-free  and  18%  had  1  relapse  during  the entire  treatment  period  (15%  missing  data).  Most  clinical  effectiveness measures, MSSS, MSIS-29 and SDMT showed statistically  significant  improvement between  baseline  and  132  months (p<0.05). Over the entire observation time, 125 SAEs had been reported to the Swedish MPA including 9 cases (2 fatal) of progressive  multifocal  leukoencephalopathy  (PML)  of  which  8  occurred between 2008 and 2012, and one in 2018.

Conclusions: NTZ  is  generally  well  tolerated  with  sustained  effectiveness regarding  cognitive,  physical  and  psychological  measures, as well as relapse-control. Introduction of JCV testing has  led  to  fewer  treated  JCV+  patients, which  likely  explains  a  drastic drop in number of reported cases of PML.