Fludarabine add-on therapy in interferon-beta-treated patients with multiple sclerosis experiencing breakthrough disease.

Background: Patients with relapsing-remitting multiple sclerosis (RRMS) may experience breakthrough disease despite effective interferon beta (IFNβ) therapy. Fludarabine (FLU) is a chemotherapeutic agent used in lymphoproliferative disorders that may be synergistic when combined with immunomodulatory therapy to control active multiple sclerosis (MS).

Objective: The objective of this study was to explore the safety and tolerability of FLU versus monthly methylprednisolone (MP) in IFNβ-treated RRMS patients with breakthrough disease.