The purpose of this study is to determine the safety and tolerability of ELND002 in patients with relapsing forms of secondary progressive multiple sclerosis (SPMS) or relapsing-remitting multiple sclerosis (RRMS).

Inclusion Criteria:

• Has either clinically definite or laboratory-supported definite relapsing forms of MS for at least 2 years
• Patients with SPMS or RRMS have documented medical history of relapse in the past year or MRI-documented evidence of MS activity in the past year
• Has had an inadequate response or intolerability to interferon and/or glatiramer acetate
• Is able and willing to undergo Gd administration and repeat MRI testing

Exclusion Criteria:

• Has primary progressive MS (PPMS)
• Any history of treatment with recombinant humanized monoclonal antibodies
• Has received treatment with immunosuppressant medications or experimental agents within 3 months prior to the Baseline
• A history of opportunistic infection or the presence of any active infection within 3 months prior to Baseline
• Any history of congestive heart failure or currently has a pacemaker
• Has a known or suspected hypersensitivity to sulfonamides or any of the components of the investigational drug
• Has any medical history or psychiatric condition that would impact outcome or study participation
• Has other clinically significant abnormality on physical, neurological, laboratory, or ECG examination as listed in the protocol during the Screening Phase