Natalizumab High Titer Immunogenicity and Safety

Negative: no detectable antibody at all post-baseline visits. Persistent positive: antibody positive at 2 or more post-baseline visits at least 42 days apart, or positive at the last post-baseline visit. Transient positive: antibody positive at only 1 post-baseline visit prior to the last visit.

AE: any sign, symptom, or diagnosis/disease that was unfavorable or unintended, new, or if pre-existing, worsened in a participant administered a study treatment and that did not necessarily have a causal relationship with this treatment. SAE: an event that resulted in death; an event that, in the view of the investigator, placed the participant at immediate risk of death (life-threatening event); an outcome that resulted in a congenital anomaly/birth defect diagnosed in a child of a participant in this study; an event that required or prolonged inpatient hospitalization; an event that resulted in persistent or significant disability/incapacity; any other medically important event that, in the opinion of the investigator, may have jeopardized the participant or may have required intervention to prevent one of the other outcomes listed above. Events were classified as 'related' or 'not related' to study drug, and categorized as 'mild' moderate' or 'severe' per protocol.

EDSS assesses disability in 8 functional systems. An overall score ranging from 0 (normal) to 10 (death due to MS) was calculated. The change in EDSS at Month 36 was calculated as EDSS at Month 36 minus EDSS at baseline.

Annualized relapse rate was calculated as the total number of relapses that occurred during the study divided by the total number of years the participant was followed in the study. The annualized relapse rate was based only on those relapses that were determined to meet the definition of relapse per the investigator's clinical judgment. New or recurrent symptoms that occurred less than 30 days following the onset of a protocol-defined relapse were considered part of the same relapse.