The U.S. Food and Drug Administration (FDA) has approved a third exon-skipping medication to treat boys with Duchenne muscular dystrophy (DMD).
More specifically, the FDA approved Amondys 45 (casimersen) to treat DMD patients who have a confirmed mutation of the DMD gene that is amenable to exon 45 skipping.
This is the first therapy designed specifically for this subset of DMD patients, which makes up approximately 8% of the DMD population. The two other exon skipping therapies are for treating patients amenable to exon 51 (eteplirsen) or exon 53 skipping (goldodirsen).
The approval of casimersen is largely based on results from a double-blind, placebo-controlled study in which 43 males between the ages of 7 to 20 years, with mutations amenable to exon 45 skipping, received intravenous casimersen (30 mg/kg) or placebo (2:1 ratio). The study observed a significantly greater increase in dystrophin protein levels from baseline to week 48 of treatment compared to placebo.
The drug was granted an Accelerated Approval based on the serious nature of the disease in combination with the fact that the drug showed an increase in dystrophin levels that will likely provide clinical benefit to patients. An additional study is required to verify and describe anticipated clinical benefits of the drug. The developer of the drug, Sarepta Therapeutics, is conducting an ongoing, double-blind, placebo-controlled, multicenter study designed to evaluate the safety and efficacy of casimersen in ambulatory DMD patients.
The most common side effects observed in DMD patients treated with casimersen were upper respiratory tract infections, cough, fever, headache, joint pain, and throat pain.
DMD is a progressive form of muscular dystrophy that occurs primarily in males. DMD causes progressive weakness and loss of skeletal and heart muscles. Muscle weakness is usually noticeable by 3 or 4 years of age and begins in the hips, pelvic area, upper legs, and shoulders. The calves may be enlarged. Children with DMD may have an unusual walk and difficulty running, climbing stairs, and getting up from the floor. Muscle weakness worsens with age and progresses to the arms, legs, and trunk. Most children with DMD use a wheelchair full time by age 13. Heart and respiratory muscle problems begin in the teen years and lead to serious, life threatening complications.
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