To Örebro University

Background: Natalizumab (NTZ) is a highly effective disease modulatory treatment for relapsing-remitting multiple sclerosis (RRMS). Post-marketing surveillance is important for determination of long-term safety and effectiveness in a real-world setting. To this end the “Immunomodulation and Multiple Sclerosis Epidemiology Study 1” (IMSE 1) was initiated upon NTZ launch in Sweden (Aug 2006).

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

Methods: In Sweden MS patients are registered in the nationwide Swedish Neuro Registry (NeuroReg). IMSE 1 includes patients starting NTZ treatment and data is collected from NeuroReg. Adverse events (AEs), JC-virus status (JCV) and clinical effectiveness measures are registered prospectively.

Results: 3052 patients (72% female; 82% RRMS; mean age at treatment start 36 years; mean treatment duration 45.9 months) have been included in IMSE 1 from August 2006 until April 2018. A total of 1234 RRMS patients where included year ≥2011 (JCV test introduction) and had information on JCV (482 anti-JCV anti-bodies (JCV+), 752 JCV negative (JCV-)). 691 of these patients were currently treated with NZT at cutoff date, 88 (13%) of which were JCV+ with a mean JCV index at 1.1±1.1. A total of 612/1234 (49%) discontinued NTZ treatment at some time point of which 266/403 (66%) JCV+ discontinued due to JCV+. JCV- patients mainly discontinued due to pregnancy/planning pregnancy (78/209, 37%) and other reasons (57/209, 27%). The one and two-year drug survival rate was 79% and 45% for JCV+ and 90% and 82% for JCV-. The overall drug survival rate was 16% for JCV+ and 72% for JCV-. In patients with continuous NTZ treatment for ≥2 years (n=738), long lasting stabilization of disease activity was observed. From year 2006 until cutoff, 96 Serious AEs had been reported to the Swedish MPA and included 8 cases (1 fatal) of progressive multifocal leukoencephalopathy (PML), reported between 2008 and 2012. A total of 14 patients have died during or within 6 months after NTZ discontinuation, as reported in NeuroReg. None were reported to be associated to NTZ.

Conclusions: NeuroReg functions well as a post-marketing drug surveillance platform, providing long-term data on drug effects and AEs. NTZ is generally well tolerated with sustained effective-ness. The introduction of JCV testing has led to fewer treated JCV+ patients, which likely explains a reduced incidence of PML.