Final approval is pending.
Mitoxantrone shows excellent efficacy in secondary progressive MS but can only be used for three years due to its toxicity profile. Thus, the goal of this trial is to combine the best of both drugs to determine whether we can obtain greatly enhanced suppression of disease activity. The patients will then receive a monthly dose of mitoxantrone on three separate occasions, while continuing with interferon beta-1b therapy. After beginning mitoxantrone, patients will continue to undergo monthly triple-dose gadolinium enhanced scans for a period of six months. Evaluation of the clinical status of the subjects, including side effects and neurological testing, will be conducted.