Open-Label Natalizumab Safety Extension Study

An Open-Label, Multicenter Extension Study to Evaluate the Safety and Tolerability of Natalizumab in Subjects With Multiple Sclerosis Who Have Completed Studies C-1801, C-1802, or C-1803

The primary objective of this study is to determine the safety and the immunogenicity of extended treatment with natalizumab when administered at a dose of 300 mg intravenously (IV) to subjects with multiple sclerosis (MS) who have completed natalizumab Studies C-1801, C-1802, or C-1803.

Inclusion Criteria:

• Must give written informed consent.
• Must be an MS subject who has completed natalizumab Study C-1801, C-1802 or C-1803

Exclusion Criteria:

• History of, or available abnormal laboratory results, indicative of any significant disease that would preclude treatment.
• History of severe allergic or anaphylactic reactions or known drug hypersensitivity
• A clinically significant infectious illness within 30 days prior to study entry.