The new treatment works alongside existing therapies and showed improved motor function in children with the rare genetic disease
A new treatment approved in the United States is giving patients with spinal muscular atrophy another option in the fight against the progressive effects of the disease.
The U.S. Food and Drug Administration approved Isembyld, also known as apitegromab-mstn, on September 11. It is the first FDA-approved therapy for spinal muscular atrophy designed to directly target muscle loss.
The treatment is approved for adults and children ages 2 and older who are already receiving an SMN2-targeted treatment.
What is spinal muscular atrophy?
Spinal muscular atrophy, known as SMA, is a rare progressive neuromuscular disease that affects approximately one in every 10,000 live births. It is also one of the leading genetic causes of infant mortality.
The condition is caused by a faulty SMN1 gene, which prevents the body from producing enough of a protein necessary for the survival of motor neurons. As those neurons are lost, patients can experience progressive muscle weakness and wasting.
Existing treatments have changed the outlook for many patients by helping the body produce more of the protein needed to protect motor neurons. But some people, particularly those with more advanced disease, continue to experience significant limitations in movement.
The new therapy takes a different approach by directly addressing muscle loss while patients continue receiving existing treatment.
What did the study find?
The FDA based its decision on a 52-week randomized, double-blind, placebo-controlled clinical trial involving 188 participants between the ages of 2 and 21. All participants were already receiving an approved SMN2-targeted therapy.
The primary analysis focused on 156 children between ages 2 and 12. Among children receiving the approved 10 mg/kg dose of Isembyld, researchers found an improvement in motor function after one year compared with patients receiving placebo.
The FDA reported that 34.2% of treated patients achieved a clinically meaningful improvement, compared with 13.5% of patients receiving placebo. That means patients receiving the treatment were more than twice as likely to reach that level of improvement.
The treatment does have risks
Isembyld is administered through an intravenous infusion once every four weeks. The most commonly reported side effects included upper respiratory infections, vomiting, cough, viral infections, headache, gastroenteritis and sore throat.
The FDA also reported an increased risk of fractures, including serious fractures, among patients receiving the drug. The treatment may cause fetal harm and may affect reproductive function.
The FDA granted Isembyld Fast Track, Orphan Drug and Rare Pediatric Disease designations. The approval was granted to Scholar Rock.
Source: U.S. Food and Drug Administration
