The dose-escalation portion of this study evaluated the safety of a single infusion of RG2077 (CTLA4-IgG4m) in 16 patients with MS and is now complete. Patients who participated in the single infusion portion of the study were assigned to one of four groups. Each group received a different dose of RG2077. The second portion of the study will evaluate the safety of 4 doses of RG2077 in 4 additional patients. In the multiple infusion portion of the study, all patients will receive the same dose of RG2077. Patients will be monitored for possible side effects of RG2077.