A Study to Evaluate Efficacy, Safety, and Tolerability of 6-Week Extended Interval Dosing of Natalizumab (BG00002) in Participants With Relapsing-Remitting Multiple Sclerosis (RRMS) Switching From Treatment With 4-Week Natalizumab Standard Interval Dosing (SID) in Relation to Continued SID Treatment

INTERVENTION: Trade Name: TYSABRI Product Name: AN100226, BG00002 Pharmaceutical Form: Concentrate for solution for infusion INN or Proposed INN: NATALIZUMAB CAS Number: 189261‐10‐7 Concentration unit: mg milligram(s) Concentration type: equal Concentration number: 300‐ CONDITION: Relapsing‐remitting multiple sclerosis (RRMS) ; MedDRA version: 21.1 Level: PT Classification code 10063399 Term: Relapsing‐remitting multiple sclerosis System Organ Class: 10029205 ‐ Nervous system disorders Therapeutic area: Diseases [C] ‐ Nervous System Diseases [C10] PRIMARY OUTCOME: Main Objective: The primary objective of this study is to evaluate the efficacy of natalizumab extended interval dosing (EID) in; subjects who have previously been treated with natalizumab standard interval dosing (SID) for at least; 12 months, in relation to continued SID treatment. Primary end point(s): Number of New or Newly Enlarging T2 Hyperintense Lesions at Week 72 Secondary Objective: The secondary objectives are to evaluate additional clinical and MRI based efficacy endpoints, and safety of; EID in subjects who have previously been treated with natalizumab SID for at least 12 months, in relation to; continued SID treatment. Timepoint(s) of evaluation of this end point: Week 72 SECONDARY OUTCOME: Secondary end point(s): •Time to First Relapse as Adjudicated by an Independent Neurology Evaluation Committee (INEC) ; •Number of new Gadolinium (Gd) Enhancing and new T1 Hypointense Lesions at Weeks 24, 48 and 72 ; •Annualized Relapse Rate at Week 72 ; •Number of New or Newly Enlarging T2 Hyperintense Lesions at Weeks 24 and 48 ; •Percentage of Participants With Adverse Events (AEs) and Serious Adverse Events (SAEs) ; •Time to Expanded Disability Status Scale (EDSS) worsening Timepoint(s) of evaluation of this end point: Variable time frames throughout the study INCLUSION CRITERIA: • Ability of the participant to understand the purpose and risks of the study and provide signed and dated informed consent and authorization to use confidential health information in accordance with national and local participant privacy regulations. • Diagnosis of relapsing remitting multiple sclerosis (RRMS) according to the McDonald criteria [Thompson 2018]. • Treatment with natalizumab as disease‐modifying monotherapy for RRMS that is consistent with the approved dosing for a minimum of 12 months prior to randomization. The participant must have received at least 11 doses of natalizumab in the 12 months prior to randomization with no missed doses in the 3 months prior to randomization. • Expanded Disability Status Scale (EDSS) <=5.5 at screening. • No relapses in the last 12 months prior to randomization, as determined by the enrolling Investigator NOTE: Other protocol‐defined inclusion criteria may app