Multiple Sclerosis Drug Combats Vision Loss
But doctors must weigh the potential risks of Tysabri, experts say
TUESDAY, April 17, 2007 (HealthDay News) -- A controversial multiple sclerosis drug called Tysabri also reduces vision loss associated with the disease by 47 percent, a new study found.
"Vision loss is probably one of the most disabling things that happens to people with MS," said lead researcher Dr. Laura J. Balcer, an associate professor of neurology at the University of Pennsylvania School of Medicine. "The exciting thing is, first, that we now have an eye-chart test that can pick that up and can show if treatments help vision. Second, this particular drug appears to help prevent vision loss."
In the study, Balcer's group looked at the results of two trials -- called AFFIRM and SENTINEL -- that included 2,138 people with relapsing MS. More than half the patients received Tysabri (generic name natalizumab) every four weeks for two years.
To evaluate eyesight, the researchers used a specially developed eye chart of low contrast letters. They found vision loss was reduced by as much as 47 percent among the people taking Tysabri, compared with those taking a placebo.
"Vision is one more dimension of MS that the drug helps," Balcer said. "It has already been shown that the drug reduces the rates of relapses and disability."
Balcer thinks that other MS drugs may have similar effects on vision, and there is now a test that can be included in trials to evaluate this. "Now, we can get to see how these other medications may help vision," she said.
The findings are published in the April 17 issue of the journal Neurology.
Tysabri's history has been marked by some controversy.
It received U.S. Food and Drug Administration approval in November 2004, only to be pulled from the market three months later after several patients in clinical trials developed a rare but deadly viral infection of the brain called progressive multifocal leukoencephalopathy. In June 2006, the FDA allowed the drug to return to the mart, but with strict conditions. According to the new guidelines, Tysabri can only be administered by approved doctors, infusion sites and pharmacies that register and comply with a patient-safety program designed by Biogen-IDEC, the maker of Tysabri, and approved by the FDA.
One expert thinks that despite the vision benefit, Tysabri should be reserved for patients with aggressive MS or those who failed other medications.
"This study confirms the benefits of this particular MS drug in relapsing MS patients," said Dr. Anne H. Cross, a professor of neurology at Washington University School of Medicine, in St. Louis. "In addition, it validates the use of a new vision test which is relevant to MS."
But the benefit to vision doesn't negate the risks associated with the drug, Cross said. "I don't think I will change my prescribing habits based upon this paper," she said. "I will probably continue to use it in the same type of patients I have been using it in in the past."
However, Nicholas LaRocca, the director of health care delivery and policy research at the National Multiple Sclerosis Society, said the new study provides additional insight into the benefits of the drug and may influence the decision whether to start using it or not.
"For patients who are on natalizumab or considering natalizumab, this gives them another piece of information to consider as they are trying to make their decision," he said.
According to the U.S. National Institutes of Health, multiple sclerosis is an unpredictable disease of the central nervous system that can range from relatively benign to somewhat disabling to devastating, as communication between the brain and other parts of the body is disrupted. Many researchers believe MS to be an autoimmune disease -- one in which the body, through its immune system, launches a defensive attack against its own tissues. In the case of MS, it is the nerve-insulating myelin that comes under assault.
The National Multiple Sclerosis Society can tell you more about multiple sclerosis.