New active lesions were defined as the sum of gadolinium (Gd)-enhancing lesions and non-enhancing new or newly enlarging T2 hyperintense lesions over a period of 24 weeks.

FAS included all participants who had received at least 1 study treatment injection and had at least 1 post baseline efficacy assessment. Here, 'overall number of participants analyzed' signifies the number of participants available for outcome measure analysis.

New active lesions were defined as the sum of Gd-enhancing lesions and non-enhancing new or newly enlarging T2 hyperintense lesions over a period of 48 weeks.

Week 48 analysis set included all participants in the FAS but excluded participants who withdrew from study due to termination of the study by Sponsor. Here, 'overall number of participants analyzed' signifies the number of participants available for outcome measure analysis.

New active lesions were defined as the sum of gadolinium-enhancing lesions and non-enhancing new or newly enlarging T2 hyperintense lesions.

FAS included all participants who had received at least 1 study treatment injection and had at least 1 post baseline efficacy assessment. Here, 'overall number of participants analyzed' signifies the number of participants available for outcome measure analysis.

New active lesions were defined as the sum of Gd-enhancing lesions and non-enhancing new or newly enlarging T2 hyperintense lesions.

Week 48 analysis set included all participants in the full analysis set but excluded participants who withdrew from study due to termination of the study by Sponsor. Here, 'overall number of participants analyzed' signifies the number of participants available for outcome measure analysis.

FAS included all participants who had received at least 1 study treatment injection and had at least 1 post baseline efficacy assessment. Here, 'number analyzed' signifies the number of participants available for analysis at specified time point.

FAS included all participants who had received at least 1 study treatment injection and had at least 1 post baseline efficacy assessment. Here, 'overall number of participants analyzed' signifies the number of participants available for outcome measure analysis.

Week 48 analysis set included all participants in the full analysis set but excluded participants who withdrew from study due to termination of the study by Sponsor. Here, 'overall number of participants analyzed' signifies the number of participants available for outcome measure analysis.

FAS included all participants who had received at least 1 study treatment injection and had at least 1 post baseline efficacy assessment. Here, 'overall number of participants analyzed' signifies the number of participants available for outcome measure analysis.

Week 48 analysis set included all participants in the full analysis set but excluded participants who withdrew from study due to termination of the study by Sponsor. Here, 'overall number of participants analyzed' signifies the number of participants available for outcome measure analysis.

ARR is calculated as the total number of relapses that occurred during the treatment period divided by the total number of participant-years. ARR was analyzed using negative binomial regression model.

FAS included all participants who had received at least 1 study treatment injection and had at least 1 post baseline efficacy assessment.

A multiple sclerosis (MS) relapse was defined as the onset of new or recurrent neurological symptoms lasting at least 24 hours, accompanied by new objective abnormalities on a neurological examination, and not explained solely by non-MS processes such as fever, infection, severe stress, or drug toxicity.

FAS included all participants who had received at least 1 study treatment injection and had at least 1 post baseline efficacy assessment.

The participant's global impression of his/her well-being was assessed with a VAS. The instrument ranges from 0 to 100 millimeters (mm), where a score of 0 denotes 'poor' and a score of 100 denotes 'excellent'. Higher scores indicates a better health state.

FAS included all participants who had received at least 1 study treatment injection and had at least 1 post baseline efficacy assessment. Here 'number analyzed' signifies the number of participants available for analysis at a specified time point.

An AE is any untoward medical occurrence in a participant or clinical investigation participant administered a pharmaceutical product and that does not necessarily have a causal relationship with this treatment. An AE can therefore be any unfavorable and unintended sign (including an abnormal assessment such as an abnormal laboratory value), symptom, or disease temporally associated with the use of a medicinal (investigational) product, whether or not related to the medicinal (investigational) product. A TEAE is defined as any AE that has an onset date and time that is on or after the date and time of the first dose of study treatment, or that has worsened after the date and time of the first dose of study treatment through 84 days after the last dose of study treatment.

Safety analysis set included all participants who had received at least 1 study treatment injection.

Safety analysis set included all participants who had received at least 1 study treatment injection.

Safety analysis set included all participants who had received at least 1 study treatment injection.

Immunogenicity analysis set included all participants who had received at least 1 study treatment injection and had at least 1 postbaseline assessment for the specific parameter.

The EDSS is a scale based on standardized neurological examination which comprised of optic, brain stem, pyramidal, cerebellar, sensory and cerebral functions, as well as walking ability. It measures the MS disability status on a scale ranging from 0 (normal) to 10 (death due to MS), with higher scores indicating more disability. A negative change from baseline indicates an improvement in the disability.

Safety analysis set included all participants who had received at least 1 study treatment injection. Here 'number analyzed' signifies the number of participants available for analysis at a specified time point.

Pharmacokinetic (PK) analysis set included all participants who had received at least 1 study treatment injection and had at least 1 measurable serum natalizumab concentration. Here 'number analyzed' signifies the number of participants available for analysis at a specified time point.

One blood sample was collected between Day 6 and Day 8.

PK analysis set included all participants who had received at least 1 study treatment injection and had at least 1 measurable serum natalizumab concentration.

Pharmacodynamic (PD) analysis set included all participants who had received at least 1 study treatment injection and had at least 1 assessment for α4-integrin saturation, serum soluble vascular cell adhesion molecule-1 (VCAM-1) concentration, and lymphocyte counts with lymphocyte subsets. Here 'number analyzed' signifies the number of participants available for analysis at a specified time point.

PD analysis set included all participants who had received at least 1 study treatment of study treatment and had at least 1 assessment for α4-integrin saturation, serum soluble VCAM-1 concentration, and lymphocyte counts with lymphocyte subsets. Here 'number analyzed' signifies the number of participants available for analysis at a specified time point.