Real World Effectiveness of Natalizumab Extended Interval Dosing in a French Cohort
Real World Effectiveness of Natalizumab Extended Interval Dosing in a French Cohort
Natalizumab (NTZ) use in Multiple Sclerosis (MS) in highly active patients has been largely
 established during the last Rationale 10 years in both clinical trials and real-world
 practice. Along with its efficacy, NTZ use has been limited by potential risk of progressive
 multifocal leukoencephalopathy (PML). Thus, several studies have tried to assess how to
 minimize this risk.

 One suggested approach is to move from the standard interval dose (SID) of 4 weeks to an
 extended interval dose (EID) of 5 weeks or longer. Extending the dosing interval of NTZ has
 been practiced by some physicians with the intention of improving the benefit/risk of the
 treatment by reducing the exposure-dependent risk of progressive multifocal
 leukoencephalopathy (PML) while maintaining efficacy. We propose to retrospectively analyze
 data from clinical records coming from RRMS patients treated in France at 5 different
 centers; Caen, Nice, Bobigny and Toulouse hospitals as well as Percy Military Hospital, to
 evaluate the effectiveness of natalizumab EID in subjects who have previously been treated
 with natalizumab SID for 12 months, in relation to continued SID treatment. In the clinical
 practice of these centers, patients are shifted after minimum 12 months under SID to an EID
 of 6 weeks regardless antibody JC serum status. Clinical, magnetic resonance imaging (MRI)
 and serum anti-JCV antibody status data are collected when available.

 The objective of this study is to assess the efficacy in term of ARR and safety.
Inclusion Criteria:

 -  Patients receiving at least 11 infusions of natalizumab as disease-modifying
 monotherapy for RRMS that is consistent with the approved dosing

 Exclusion Criteria:

 -  Patients for whom the NTZ infusion history and/or MRI and clinical history is not
 available.

 -  Patients with dosing gap defined as >=12 weeks between any two doses.

 -  Patients with over dose defined as <3 weeks between any two doses.

 -  Pregnancy during the follow-up period