Muscular dystrophy is a term that describes a wide range of debilitating muscle-wasting conditions.

A cause of several versions of the disease is mutations of genes that help protect and repair muscle fibers. For example, mutations in the DMD gene cause Duchenne or Becker muscular dystrophy. They can prevent or greatly reduce the production of dystrophin, a protein essential to muscle health.

Although there is no cure for any type of MD, the U.S. Food and Drug Administration, the European Medicines Agency and other regulatory bodies have approved therapies that address symptoms. And scientists continue to work on development of treatments.

Exondys 51

Exondys 51 (eteplirsen) was the first MD therapy to receive FDA approval — in September of 2016. The conditional authorization covers DMD patients whose disease is caused by certain mutations.

The therapy is not yet approved in Europe, although its developer, Sarepta Therapeutics, submitted a marketing authorization application for its approval in December 2016. The company expects a decision in late 2017.

Exondys 51, whose aim is to slow the progression of DMD, helps the body produce a workable version of dystrophin protein instead of an unviable one. The therapy works only in patients with mutations that can be corrected with exon skipping. Exons are sections of a gene’s DNA that code for the proteins the gene produces. With DMD, some exons are missing, preventing dystrophin production. Exondys 51 overcomes the problem.

Clinical trials have shown that Exondys 51 is safe and that patients tolerate it well. Sarepta is conducting the Phase 3 PROMOVI trial (NCT02255552) at 39 sites across the United States to evaluate Exondys 51’s effectiveness.

Translarna

Translarna (ataluren) treats certain types of DMD and BMD. European regulators have approved it, but it has yet to receive U.S. authorization.

PTC Therapeutics produces Translarna, which helps people with a particular DMD gene mutation produce a workable version of dystrophin. The goal is to help slow the progression of the disease.

European regulators’ approval was based on a Phase 2/3 clinical trial (NCT00592553) suggesting that 48 weeks of Translarna can slow patients’ decline in walking ability, compared with a placebo.

PTC Therapeutics is a conducting a trial (NCT02369731) at the request of European regulators on Translarna’s long-term safety and effectiveness. The company is recruiting participants for the study in Austria, France, Germany, Israel, and Sweden.

Emflaza

Emflaza (deflazacort) treats symptoms of DMD in patients 5 years old and older. The FDA approved the Marathon Pharmaceuticals therapy in February 2017.

Emflaza is what scientists call a corticosteroid prodrug. This means that the body converts it into an active corticosteroid, or anti-inflammatory agent.

Exactly how the therapy works in DMD is unknown. What scientists do know is that it has an anti-inflammatory effect, reducing swelling and damage caused by the immune system attacking healthy tissue.

Several severe side effects can prevent long-term use of corticosteroids. In a Phase 3 clinical trial (NCT01603407), Marathon researchers found Emflaza to have the beneficial effects of the corticosteroid prednisone, with fewer side effects.

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