Leukemia Drug Proves Effective for Treating Multiple Sclerosis

Results of a Phase 2 clinical trial have shown that despite having some potentially dangerous side effects, the drug alemtuzumab is effective for slowing the progression of multiple sclerosis (MS) and for reversing some of the neurological damage caused by the disease.

Alemtuzumab is a humanized monoclonal antibody that selectively binds to CD52, a protein found on the surface of normal and malignant B and T cells, that is used to reduce the numbers of circulating malignant cells of patients who have B-cell chronic lymphocytic leukemia (B-CLL). The [U.S.] Food and Drugs Administration (FDA) approved the use of alemtuzumab for the treatment of refractory B-CLL in May of 2001.

In the current study, investigators at the University of Cambridge (UK) compared the efficacy of alemtuzumab treatment to that of interferon beta-1a, one of the most effective licensed therapies for MS. They assigned 334 patients with scores of 3.0 or less on the Expanded Disability Status Scale and disease duration of three years or less to receive either subcutaneous interferon beta-1a three times per week or intravenous doses of alemtuzumab for 36 months.

Results published in the October 23, 2008, issue of the New England Journal of Medicine (NEJM) revealed that alemtuzumab significantly reduced the rate of sustained accumulation of disability, as compared with interferon beta-1a. The mean disability score on a 10-point scale improved by 0.39 points in the alemtuzumab group and worsened by 0.38 points in the interferon beta-1a group. In the alemtuzumab group, the lesion burden (as seen with magnetic resonance imaging) was reduced, as compared with that in the interferon beta-1a group. From month 12 to month 36, brain volume increased in the alemtuzumab group but decreased in the interferon beta-1a group. Alemtuzumab reduced the number of attacks experienced by people with relapsing-remitting multiple sclerosis by 74% over and above that achieved with interferon beta-1a, and it also reduced the risk of sustained accumulation of disability by 71% compared to interferon beta-1a.

On the downside, alemtuzumab therapy was suspended before the end of the study after immune thrombocytopenic purpura developed in three patients, one of whom died. The investigators are confident that they will be able to find ways to minimize this potentially dangerous side effect.

"Alemtuzumab is the most promising experimental drug for the treatment of multiple sclerosis, and we are hopeful that the Phase 3 trials will confirm that it can both stabilize and allow some recovery of what had previously been assumed to be irreversible disabilities,” said contributing author Dr. Alastair Compston, professor of neurology at the University of Cambridge.

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