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MDA Celebrates FDA Approval of Vyondys 53 for Treatment of DMD Amenable to Exon 53 Skipping

Second approved exon-skipping therapy for Duchenne muscular dystrophy

NEW YORK, Dec. 13, 2019 /PRNewswire/ -- The Muscular Dystrophy Association (MDA) today celebrated the decision by the US Food and Drug Administration (FDA) to grant accelerated marketing approval to golodirsen (Vyondys 53) for the treatment of Duchenne muscular dystrophy (DMD) in patients amenable to skipping exon 53. It is the second exon-skipping, disease-modifying drug to treat DMD, the most common childhood form of muscular dystrophy. Vyondys 53 will be made available in the United States and marketed by Sarepta Therapeutics.

In September 2016, the approval of eteplirsen (marketed by Sarepta as Exondys 51) marked a watershed moment for treating neuromuscular diseases with gene-targeting therapies such as exon skipping. Approval of Vyondys 53, another exon-skipping drug designed to treat a different subset of DMD individuals than those who qualify for Exondys 51, is another significant step forward in the development of therapies for DMD — and all neuromuscular diseases — that target the root cause of the disease.

"The approval of Vyondys 53 is another breakthrough toward treating Duchenne, a disease that, up until a few years ago, had no approved therapies," says MDA's Executive Vice President and Chief Research Officer Sharon Hesterlee, PhD. "It's another milestone for the field of DMD research and drug development, and it represents the fulfillment of the promise of effective genetic medicines for DMD patients and their families."

DMD is caused by mutations in the dystrophin gene (DMD) on the X chromosome that result in little or no production of dystrophin, a protein essential to keeping muscle cells intact. Vyondys 53 is called an "exon-skipping" drug in that it is designed to target and promote skipping over a section of genetic code in order to avoid the gene mutation and produce more of the dystrophin protein. It is estimated that up to 8% of patients with DMD have mutations amenable to treatment with Vyondys 53. Although treatment with the drug will not cure DMD, it could slow progression of the disease, which, in turn, could extend the length of time individuals with DMD could walk, eat independently, and breathe without assistance.

The FDA's decision to approve Vyondys 53 highlights the importance of years of commitment to supporting and funding breakthrough research by MDA and others into gene identification and unlocking the cause of DMD. MDA-supported research has been central to the development of the exon-skipping approach behind both Exondys 51 and Vyondys 53 from the beginning, having funded foundational work upon which the strategy was built as well as extensive research into the strategy since that time. Laboratory development of exon-skipping therapies began in the 1990s, including notably with MDA-funded work by Steve Wilton, PhD, and colleagues. Their work led to the invention of what would later become Exondys 51 and Vyondys 53.

Since its inception, MDA has committed more than $218 million to DMD and Becker muscular dystrophy research and more than $1 billion across the spectrum of neuromuscular diseases. While this may be the second exon-skipping therapy for treating DMD, the increasing pace of drug development holds immense promise for the future of all neuromuscular diseases. Of the now 11 approved therapies for treating neuromuscular diseases, nine have been approved by the FDA in the past decade alone.

Clinical trials support approval of Vyondys 53

The FDA based its decision to grant accelerated approval to Vyondys 53 on the positive results of a pivotal (phase 1/2) clinical trial conducted in Europe to assess the safety, tolerability, pharmacokinetics (how the drug is absorbed, distributed, and metabolized in the body), and efficacy (dystrophin expression) of Vyondys 53 in 25 boys with DMD with confirmed deletions in the dystrophin gene amenable to exon 53 skipping.

The results showed an observed statistically significant increase in dystrophin production in skeletal muscle of patients treated with Vyondys 53, which is reasonably likely to predict clinical benefit for those patients. Consistent with the FDA's accelerated approval pathway, the continued approval of Vyondys 53 may be contingent on confirmation of a clinical benefit in a post-marketing confirmatory trial (ESSENCE), which is currently enrolling and expected to conclude by 2024. 

Hypersensitivity reactions, including rash, fever, itchy skin, hives, dermatitis, and skin exfoliation, have occurred in patients who were treated with Vyondys 53. Renal toxicity was observed in animal studies. The most common adverse reactions that occurred in at least 20% of treated patients and more frequently than in placebo-group patients were headache (41%), fever (41%), fall (29%), abdominal pain (27%), nasopharyngitis (27%), cough (27%), vomiting (27%), and nausea (20%).

About SareptAssist

SareptAssist is a patient support program designed to provide patients with information to help navigate the process of starting and staying on therapy. Sarepta's dedicated team will provide information on insurance benefits, financial assistance options, treatment logistics, options for drug delivery, and ongoing education and support.

MDA's Resource Center provides support, guidance, and resources for patients and families, including information about the approval of Vyondys 53, open clinical trials, and other services. Contact the MDA Resource Center at 1-833-ASK-MDA1 or ResourceCenter@mdausa.org.

About DMD

DMD occurs in 1 in every 3,500 to 5,000 males born worldwide. The disease primarily affects boys, but in rare cases it can affect girls. Onset of symptoms occurs in early childhood, usually between ages 3 and 5. Muscle weakness can begin as early as age 3, first affecting the muscles of the hips, pelvic area, thighs, and shoulders, and later the skeletal (voluntary) muscles in the arms, legs, and trunk. The calves often are enlarged. By the early teens, the heart and respiratory muscles also are affected.

About Vyondys 53

Vyondys 53 uses Sarepta Therapeutics' exon-skipping technology to target exon 53 of the DMD gene. Exon skipping is a treatment strategy in which sections of genetic code are "skipped" (spliced out, or left out) during the protein manufacturing process, allowing cells to create shortened but partially functional dystrophin protein, the muscle protein missing in DMD. Exon skipping is not a cure for DMD but potentially could lessen the severe muscle weakness and atrophy that is the hallmark of the disease.

Just as individuals with DMD caused by a mutation that would be amenable to skipping exon 51 could benefit from treatment with Exondys 51, those with DMD caused by a mutation that would be impacted by skipping exon 53 potentially could benefit from treatment with Vyondys 53.

About the Muscular Dystrophy Association

MDA is committed to transforming the lives of people affected by muscular dystrophy, ALS, and related neuromuscular diseases. We do this through innovations in science and innovations in care. As the largest source of funding for neuromuscular disease research outside of the federal government, MDA has committed more than $1 billion since our inception to accelerate the discovery of therapies and cures. Research we have supported is directly linked to life-changing therapies across multiple neuromuscular diseases. MDA's MOVR is the first and only data hub that aggregates clinical, genetic, and patient-reported data for multiple neuromuscular diseases to improve health outcomes and accelerate drug development. MDA supports the largest network of multidisciplinary clinics providing best in class care at more than 150 of the nation's top medical institutions. Our Resource Center serves the community with one-on-one specialized support, and we offer educational conferences, events, and materials for families and healthcare providers. Each year thousands of children and young adults learn vital life skills and gain independence at summer camp and through recreational programs, at no cost to families. For more information visit mda.org.

SOURCE: Muscular Dystrophy Association