Source: Rocky Mountain MS Center enews Aug 6
MS Therapies in the Pipeline:
In this week's eMS News, we continue with our series, MS Therapies in the Pipeline.
As MS progresses, walking can become a challenge and many people with MS are forced to use the aid of a cane, walker or wheelchair. According to recent research, 64% - 85% of people with MS have difficulty walking, and 70% report it to be the greatest symptomatic challenge that they face.
Hope for these individuals may soon be available in pill form. Fampridine-SR, a sustained-release tablet, is a selective neuronal potassium (K+) that blocks potassium channels on the surface of nerve fibers. The idea is that by blocking these channels, the conduction of nerve signals – which travel through nerve fibers – is improved, despite the myelin damage that characterizes MS. The improved nerve communication facilitates vital nerve connections that are necessary for mobility.
The thought is not that Fampridine-SR will replace standard disease modifying therapies, but rather that it will function as an add-on symptomatic treatment option for those who have difficulty walking.
The second large Phase III clinical trial on Fampridine-SR involved 240 individuals with relapsing remitting, secondary-progressive, primary-progressive, and progressive-remitting MS. The results were presented at the World Congress on Treatment and Research in Multiple Sclerosis in Montreal, Canada, in June 2008. Investigators' primary goal was to evaluate whether participants were able to complete the Timed 25-Foot Walk more quickly after receiving Fampridine-SR (pre and post-study testing was done). One hundred and twenty participants were treated with Fampridine-SR – 10mg twice a day – and 119 with placebo; all participants were permitted to continue their prescribed immunomodulator therapies
Of those on Fampridine-SR, the response rate – the improvement in walking ability – was higher than placebo in all four MS subtypes. The highest improvement rate, 50%, was seen in primary-progressive patients. Overall, 42.9% of participants on Fampridine-SR demonstrated improvement in walking speed, compared to 9.3% of participants on placebo. Additionally, participants on Fampridine-SR also demonstrated increased leg strength, which was the secondary outcome – or goal – of the study.
Because the effect of Fampridine-SR on increasing conduction velocity is not restricted to motor pathways but is a general effect, it may also be useful for other symptoms of MS, says Dr. Vollmer, who has worked on the drug for more than 10 years. Whether this is true or not will probably be determined by patients and their physicians as they carefully try the medication for other important MS symptoms.
Throughout the various studies done on Fampridine-SR, investigators have struggled to find the most efficient dosage. If given too little, patients demonstrated no improvement; if given too much, the risk of developing epileptic seizures went up significantly. In the above study, however, side effects were quite mild. Urinary tract infections, insomnia, nausea, dizziness and headache were among the most frequently reported side effects for those on Fampridine-SR. Only one adverse event involving a partial seizure was seen, and it was in the placebo group.
These encouraging results are the latest in a stream of positive findings on Fampridine-SR, which has been studied in a number of clinical trials to date. In fact, in May 2009 the FDA assigned Priority Review for Fampridine-SR’s New Drug Application. The FDA hopes to complete the review by Oct. 22, 2009, meaning the therapy will likely be on the market – and available – by the end of the year.