Clinical Disease Activity With Long Term Natalizumab Treatment

MRI and Clinical Disease Activity in Patients Treated Long Term With Natalizumab

The primary objective of the study is to retrospectively investigate the proportion of participants free of new or enlarging fluid-attenuated inversion recovery (FLAIR) lesions over time in approximately 300 Relapsing-Remitting Multiple Sclerosis (RRMS) participants with regular MRI follow-up, who have received natalizumab ≥24 month from two different observational cohorts: 1) approximately 230 participants from the Czech Republic; and 2) approximately 70 participants from Belgium. The secondary objectives of this study are as follows: Brain volume change by various measures; Changes in the number and volume of magnetic resonance imaging (MRI) lesions; No evidence of disease activity (NEDA) with and without brain volume change.

Natalizumab will not be provided to participants by Biogen as a part of this study. Participants will remain on natalizumab therapy as prescribed by their physician.

Key Inclusion Criteria:

• Diagnosis of RRMS.
• Continuous treatment with natalizumab of ≥24 months. In case of a treatment interruption from natalizumab ≥60 days after a total treatment period of ≥24 months, only the treatment prior to the interruption will be analyzed. Any data after this treatment interruption (even if the patient restarts natalizumab) will not be analyzed/collected.
• ≥1 MRI scan of sufficient quality for reliable measurement.
• Baseline MRI scan ≤6 month prior to natalizumab treatment acquired.
• ≥1 MRI scan of sufficient quality for reliable measurement taken while on natalizumab treatment for ≥6 months.
• EDSS ≤ 6.5.

Key Exclusion Criteria:

• Anti-natalizumab antibody detection.
• Prior treatment with alemtuzumab.
• Prior treatment with mitoxantrone within 12 months of the first infusion of natalizumab.

NOTE: Other protocol defined Inclusion/Exclusion criteria may apply.