The controversial multiple sclerosis drug Tysabri also reduces vision loss associated with the disease by 47%, 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 in Philadelphia. "The first exciting thing about the study is that we have now developed an eye-chart test that can pick up vision loss and it can show if treatments are helping vision. Secondly, this particular drug appears to actually 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.
New Vision Test
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% among the people taking Tysabri, compared with those taking a placebo.
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.
"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."
Never An Easy Path
Tysabri's history has been marked by some controversy.
It received US 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 market, 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.
Caution: One expert thinks that despite the vision benefit, Tysabri should be reserved for patients with aggressive MS or for those who used other medications unsuccessfully.
"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 the past."
New Information Always Welcome
However, Nicholas LaRocca, the director of health care delivery and policy research at the National Multiple Sclerosis Society in New York City, 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 are considering it, this gives them another piece of information to consider as they are trying to make their decision," he said.
What Is Multiple Sclerosis?
According to the US 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.