Multiple Sclerosis: Tysabri Therapy

In February 2005, the makers of Tysabri voluntarily withdrew sales of the drug after three patients in the drug's clinical trials developed a serious brain infection called progressive multifocal leukoencephalopathy (PML), which usually leads to death or severe disability.

On June 5, 2006, the FDA allowed the drug Tysabri back on the market after there were no additional cases of PML in a clinical trial that was resumed in February 2006 and on re-examination of patients from the previous clinical trials.

The drug's return to the market will include a risk-minimization program with mandatory patient registration and periodic follow-up to identify any possible cases of PML as soon as possible.

Tysabri is a new drug used to treat multiple sclerosis (MS). Tysabri is unique among MS drugs in that it works by blocking the effects of white blood cells, which are believed to be harmful to the nervous system (brain, spinal cord, and nerves) and may create the damaging effects of MS. Tysabri, a monoclonal antibody, binds to white blood cells and prevents them from entering the brain and spinal cord.

Tysabri is the first monoclonal antibody approved for the treatment of MS.

Which Patients Should Receive Tysabri?

Tysabri can be prescribed to treat patients who have relapsing forms of MS. The drug reduces the frequency of MS attacks. In a study comparing Tysabri with a placebo (sugar pill), Tysabri reduced the average yearly relapse rate by 66%. In addition, patients taking Tysabri had fewer new brain lesions.

How Is the Medication Given?

Tysabri is given intravenously (through a vein) over the course of an hour every four weeks in a doctor's office.

What Are the Side Effects of Tysabri?

The most common side effects are:

• Infections
• Allergic reactions
• Depression
• Gall bladder disorders
• Headache
• Fatigue
• Joint pain
• Menstrual problems

It is important that patients are observed for one hour after each infusion in case an allergic reaction develops.

As is the case with all medications, it is important to weigh the risks and benefits carefully. Talk to your doctor to determine if this treatment is right for you.

Reviewed by the doctors at The Cleveland Clinic Neuroscience Center.