Placebo Controlled Study in Subjects With Relapsing Forms of MS to Evaluate the Safety, Tolerability and Effects of CDP323

Inclusion Criteria: * relapsing form of MS * screening EDSS score 0 - 5.5, inclusive * at least one clinical relapse in the 12 months before screening * active disease, defined by set of MRI activity criteria * failed prior treatment with beta-interferons or glatiramer acetate Exclusion Criteria: * signs of silent infections, including positive tests for HIV1, HIV2 or Hepatitis B or Hepatitis C or tuberculosis * known allergy to gadolinium-DTPA, and/or ingredients of the study drug formulation * pre-treatment with immunosuppressive or immunomodulatory drugs prior to screening within certain time frames