Tysabri, a drug generically known as natalizumab that was pulled off the market after three users developed a serious brain condition, decreases the rate of disease progression in those suffering from a relapse of multiple sclerosis (MS), three trial studies have found.
According to the researchers, the drug, administered alone or taken with the standard interferon treatment, slashes the relapse rate by almost two-thirds over a period of two years. “The available drugs for MS, interferon and Copaxone, have been shown in trials to reduce relapse rate by one third,” said Cleveland Clinic Foundation's Dr Richard A Rudick, who led one of the trials. He added that the “effectiveness of Tysabri” is much better.
“The two-year data from two Phase III clinical trials of Tysabri, among the largest ever in MS, alongside findings from a comprehensive safety evaluation, underscore the compelling efficacy of Tysabri in MS and the extensive nature of the safety evaluation. Both will be used to further define the benefit-risk profile,” said Davia Temin, a spokesperson for Elan Corp, which developed the drug along with Biogen Idec.
Under the first trial, the researchers, led by Dr Chris H Polman of the VU Medical Center in Amsterdam, divided 942 relapsed MS patients into two categories. The first category was given natalizumab once in four weeks and the second a placebo. After keeping the patients on the treatment for a period of two years, they found that the progression of disability fell by 42 per cent in the natalizumab group. In addition, this group also saw a 59 per cent reduced risk of relapse and the instances of new or growing MS lesions inside the brain went down by a whopping 83 per cent.
The second trial had Dr Richard A Rudick and his team studying 1171 MS patients who had undergone a minimum of one relapse in the last one year.
The study subjects, who were on interferon before the treatment began, had natalizumab added to their treatment. While some of them were placed on natalizumab every four weeks, others were administered placebo. Over a period of two years, the researchers noted that the natalizumab group had a 24 per cent reduced risk of progression of disability as against the group on placebo. The same group also saw a 55 per cent reduced rate of relapse and 83 per cent lesser chances of new or growing lesions.
But it was the third study that established the safety of the drug, as 3,116 patients taking natalizumab were found to have no additional instances of progressive multifocal leucoencephalopathy (PML), the side effect that had led to the suspension of the drug earlier. “We concluded that at this particular time there is no evidence that there are more PML cases,” said lead author Eugene Major, of US National Institute of Neurological Disorders and Stroke.
However, this doesn't mean that the risk doesn't exist. One person out of 1,000 taking the drug still developed PML. The findings of all the trials have been published in
New England Journal of Medicine.
Meanwhile, the drug has gone up for review before the US Food and Drug Administration (FDA).
According to National Multiple Sclerosis Society's Dr John Richert, the important thing is to evaluate all the data that is available and then release it to public so patients can make informed decisions. “The efficacy data was very encouraging and the extra year of follow-up during which people who had taken Tysabri were evaluated did not reveal any additional cases of PML, which is also very encouraging. The issue now is for the FDA to evaluate all of the efficacy data and all of the risk data and come up with the wisest decision possible,” he added.
