INTRODUCTION: Alemtuzumab is a humanized IgG1 kappa monoclonal antibody approved 
for treatment of B-cell chronic lymphocytic leukemia. This cytolytic antibody is 
directed against CD52 and depletes lymphocytes, with monocytes, macrophages, 
natural killer cells and a subpopulation of granulocytes being affected to a 
much lesser degree. Alemtuzumab is currently under review to treat relapsing 
multiple sclerosis (MS) in the United States, based on positive Phase II and 
Phase III trials in both treatment-naïve and treated relapsing MS patients. 
There was excellent efficacy in suppressing both clinical and neuroimaging 
disease activities. In these trials, the comparator arm was not placebo, but 
high dose frequently dosed subcutaneous interferon beta 1a. Alemtuzumab has 
recently been approved by the European authorities for active relapsing MS, in 
essence as a first-line agent. It produces long-standing effects, consistent 
with an induction agent. Efficacy will have to be weighed against risk of 
adverse effects, which include autoimmune disorders and infection. Alemtuzumab 
joins an increasingly crowded market, and will add to the complexity of treating 
MS.
AREAS COVERED: This review will discuss alemtuzumab as a therapy for MS, 
reviewing PubMed for clinical trials, publications and presentations at 
international meetings. It will focus on a United States market perspective.
EXPERT OPINION: Alemtuzumab offers induction strategy for very active relapsing 
MS patients who have failed conventional therapy, and possibly selected 
treatment-naive patients. Alemtuzumab use is likely to be restricted to 
specialized MS centers, with long-term monitoring to determine the true risk for 
adverse effects.