Study finds why some benefit from MS drug

CHICAGO (Reuters) - Genetic factors may help reveal which multiple sclerosis patients are likely to benefit from a widely used therapy and explain why some are not helped, according to a report published on Monday.

The treatment involved uses a protein known as recombinant interferon beta to try to treat multiple sclerosis symptoms and perhaps slow the course of the disease, for which there is no known cure.

The study looked at three drugs -- Betaseron by Bayer HealthCare Pharmaceuticals, Avonex by Biogen Idec and Pfizer's Rebif.

The problem, according to the report published in the Archives of Neurology, is that about half of patients given the therapy continue to suffer relapses and a worsening disability.

"In addition, adverse effects, such as flu-like symptoms and depression, are common, leading many patients to discontinue therapy," Dr. Esther Byun of the University of California, San Francisco, and colleagues wrote in their report.

The researchers said they examined 206 patients in southern Europe with the disabling disease who were receiving the therapy. A check of their DNA found genetic differences between those who were helped by the treatment and those who were not.

During the study, 99 of the patients were helped by interferon beta and 107 were not.

They found 18 different small mutations, called single nucleotide polymorphisms or SNPs, that might explain the differences.

Identification of genetic mutations that affect how the body responds to the therapy "provides important new insights" into the way the treatment works, the study said, and brings "rational drug design and personalized medicine one step further."

The researchers cautioned however, that more research and a larger study are needed to explore the issue farther. (Reporting by Michael Conlon; Editing by Maggie Fox and Cynthia Osterman)