MS drug’s side effects may be preventable

The future of a revolutionary treatment for multiple sclerosis may hinge on a single patient who survived a rare but potentially fatal side effect that wreaks havoc in the brain, doctors reported online today in the New England Journal of Medicine.

The drug, Tysabri, was pulled from the market in February by its maker, Biogen Idec and Elan Pharmaceuticals, after two patients died of a brain disease seen mostly in AIDS patients. That a patient survived suggests that, with early diagnosis and treatment, doctors may be able to avert brain damage in Tysabri patients, salvaging the drug for those who need it.

“Stopping therapy may prevent the disease,” said Burt Adelman, vice president of drug development for Biogen. He said the firm hopes to find an approach to Tysabri therapy that will protect patients and bring the drug back to market.

Doctors feared that the Tysabri disaster could derail a new generation of drugs that represent medicine’s best hope of treating autoimmune diseases.

The drugs are knock-offs of natural infection-fighters called antibodies. The man-made versions target immune system or cancer cells that cause disease. Tysabri attacks renegade white blood cells that damage nerves in patients with multiple sclerosis.

The government approved Tysabri in November after studies showed that the drug reduced the relapse rate by 66 percent over a placebo and 54 percent over a rival drug called Avonex. The drug has also been tested in patients with Crohn’s disease and rheumatoid arthritis.