An experimental drug called eteplirsen has shown potential as a treatment for Duchenne’s Muscular Dystrophy (DMD), Sarepta Therapeutics, Inc. announced today. The drug, which so far has shown no serious side effects, enabled boys to walk longer than those who received placebo. Most significantly, eteplirsen was shown not only to help in maintaining current muscle mass, but also in repairing damaged muscle.
DMD results in rapid muscle loss as a result of a lack of dystrophin protein, which protects and repairs muscle. The disease, which primarily affects boys (due to the fact that it is X-linked), typically is diagnosed early in childhood, with most affected losing the ability to walk by their early teens. As the disease progresses, movement is gradually lost and most boys require mechanical ventilation and nutritional support in their late teens to early twenties; many do not survive past their thirties.
As a result, any treatment that could delay the progression of the disease or potentially halt the muscle damage altogether would be momentous. Eteplirsen only works on a select subgroup of those with DMD, since, as an oligonucleotide, it works to “trick” the body into producing a form of dystrophin based on a particular genetic defect.
In approximately 85% of those with DMD, the protein dystrophin isn’t produced because a section of the gene coding for the protein is missing, often simply because of a single missing base pair. One of these common errors is Exon 51, for which eteplirsen works, and affects roughly 13% of those with DMD. What eteplirsen does is allow the protein production machinery of the body to “skip” over the missing segment, therefore producing a slightly incomplete–yet apparently still effective–version of dystrophin.
In the study, boys who received the treatment ultimately walked nearly 90 meters longer than those who received the placebo/delayed treatment. Although the study size was small (only 12 participants), Sarepta is hopeful they will get FDA approval soon. Not only is this great news for those with DMD that would qualify for eteplirsen treatment, it also opens the door for other similar drugs for common exons such as Exon 45 and 50 (of which Serepta is in pre-clinical trials).
You can read more detail about the drug and Serepta on their official website.