November 27, 2004
New MS Drug Gets Federal Approval
WASHINGTON -- The government approved a drug Tuesday that tries a new method of attacking multiple sclerosis, an incurable disease of the central nervous system that affects 350,000 Americans.
The drug -- a monoclonal antibody produced by Cambridge, Mass.- based Biogen Idec Inc. and Irish drug maker Elan Corp. -- is known chemically as natalizumab. During clinical trials, it was called Antegren, but in the Food and Drug Administration announcement, the name was changed to Tysabri.
A second trial looked at MS patients who had one or more relapses with the drug Avonex. Some received Tysabri or placebo along with Avonex. The Tysabri-Avonex treatment reduced relapse frequency by 54 percent, compared with placebo. The most frequent serious side effects were pneumonia, rash, fever, low blood pressure and chest pain.
All told, 2,800 patients with multiple sclerosis and Crohn's disease received Tysabri in placebo-controlled clinical trials. The most frequent side effects were headache, fatigue and inflammation of the nose and pharynx.
Antibodies are proteins that the body's immune system uses to fight infection. Monoclonal antibodies are made in the lab and act just like people's own antibodies to attack foreign substances.
The FDA has approved monoclonal antibodies to battle other ailments, including cancer.
But Tuesday's approval of the monoclonal antibody treatment Tysabri was the first time the government approved the targeted therapy to treat multiple sclerosis. The approval covers intravenous delivery of the drug once a month in a doctor's office.
"It's exciting news for patients with MS," said Dr. David Ross, a supervisory reviewer in the FDA's Center for Drug Evaluation and Research. "There are no cures for MS, but it does reduce the frequency of relapses . . . a significant manifestation of the disease."
Dr. J. Theodore Phillips, an MS expert, said the relapses are devastating for patients who often were perfectly healthy before developing the chronic ailment.
Without warning, a relapse can erase vision, turn a working arm or leg useless or numb feeling below the waist.
"That will last for several weeks followed by a slow improvement," said Phillips, director of the MS Center at Texas Neurology in Dallas and the principal investigator for one of the Tysabri studies. "The best we have been able to do, up to this point, has been to reduce relapse frequency by about a third."
In the study Phillips led, Tysabri performed twice as well.
The drug is a bioengineered product that uses part of a mouse antibody to closely resemble a human antibody.
In patients with multiple sclerosis, their body's immune system turns rebellious, attacking, inflaming and damaging its own nerve tissue. The debilitating condition leaves people tired and numb with poor coordination and blurred vision.
The most common type of MS involves a worsening, or relapse, of acute symptoms.
Tysabri blocks destructive immune cells that want to leave the bloodstream and make their way into the brain, gastrointestinal tract and joints to wreak havoc.
Biogen Idec: www.biogen.com