Approved Treatments for Muscular Dystrophy
There is no cure for any type of muscular dystrophy (MD), but various medications and therapies can help manage symptoms or slow the progression of the disease. Many therapies are specific to one type of dystrophy. Some of the treatments approved to treat MD are summarized below.
Exon skipping is a treatment approach for people whose Duchenne muscular dystrophy is due to certain mutations in its causative gene. Exon skipping works like a molecular patch, so that the DMD gene can produce a shorter version of the dystrophin protein to help protect and maintain the strength of muscle fibers.
Amondys 45 (casimersen) is a treatment for DMD patients with mutations amenable to exon 45 skipping. It is the third Sarepta exon-skipping therapy that the FDA approved for DMD patients. Others include Exondys 51 (eteplirsen) for patients amenable to exon 51 skipping and Vyondys 53 (golodirsen) for those with mutations amenable to exon 53 skipping.
Exondys 51 (eteplirsen or AVI-4658) is the first treatment approved by the FDA for a specific group of patients with DMD. These patients — 13% of the total Duchenne population — have gene deletions that are amenable to exon 51 skipping. Exondys 51 is designed to address the underlying cause of DMD.
Viltepso (viltolarsen) is an approved therapy to treat DMD resulting from mutations amenable to exon 53 skipping. Viltepso is administered as an infusion into the bloodstream. Patients can choose to receive the weekly hour-long treatment, done by a healthcare professional, at home, at a hospital, or a treatment center. The FDA gave Viltepso conditional approval on Aug. 12, 2020. This conditional approval is pending the results of the ongoing Phase 3 RACER53 trial.
Vyondys 53 (golodirsen, SRP-4053) is an approved exon-skipping therapy to treat DMD patients whose disease is amenable to exon 53 skipping. The FDA gave Vyondys 53 accelerated approval in December of 2019. Vyondys 53 is designed to mask exon 53 in the mRNA (a temporary copy of a gene used to make a protein) of the DMD gene so the protein synthesis machinery can skip this exon and piece together the remaining exons to make a smaller, but functional, dystrophin protein.
Patients with MD are often prescribed corticosteroids, also called glucocorticoids, which may preserve muscle tissue by reducing both inflammation and immune system attacks on those tissues. They also may speed up the processes that are involved in repairing cell membranes. There are many types of corticosteroids that may be prescribed for MD.
Emflaza (deflazacort) is a therapy to treat Duchenne muscular dystrophy (DMD) in patients 2 or older, regardless of disease-causing genetic mutation. Emflaza is a pro-drug, meaning that the therapy must be metabolized in the body into its active form. It contains a pro-corticosteroid, which, once metabolized, becomes a corticosteroid. Once metabolized to its active form, Emflaza acts to suppress the immune system.
Prednisone is a synthetic corticosteroid that is generally prescribed to delay the progression of muscle weakness in muscular dystrophy patients. It mimics the action of a naturally occurring corticosteroid called cortisol, which is produced by the adrenal glands. Prednisone is prescribed for its anti-inflammatory properties, and in the case of MD, its long-term use can delay the progression of muscle weakness.
Gene therapy is a promising treatment option for genetic conditions such as muscular dystrophy. It involves correcting the genetic defect by introducing a normal copy of the affected gene into the patient’s cell or by silencing a faulty gene. Harmless modified viruses are commonly used for the targeted delivery of healthy genes into the body. The adeno-associated virus (AAV) is one such delivery vector, and several AAV-mediated gene therapy candidates are currently being evaluated as potential treatments for muscular dystrophy.
Elevidys (delandistrogene moxeparvovec-rokl), previously called SRP-9001, is a onetime gene therapy approved to treat certain patients with DMD. The FDA granted Elevidys accelerated approval in June 2023, making it the first gene therapy for DMD to be authorized for commercial use. Elevidys was approved based on data showing it leads to the expression of micro-dystrophin protein in patients’ muscles, suggesting it works as designed.