FDA Delays Apitegromab Approval, Cites Facility Concerns

The FDA has issued a Complete Response Letter (CRL) for the apitegromab Biologics License Application (BLA) for the treatment of patients with spinal muscular atrophy (SMA), according to a news release published today.

The CRL is not specific to apitegromab’s safety, efficacy or third-party drug substance manufacturer. Instead, the CRL cited observations made during a routine inspection of Catalent Indiana LLC, a third-party fill-finish facility.

Scholar Rock, apitegromab’s developer, will resubmit the apitegromab BLA when Catalent Indiana addresses the FDA observations.

Apitegromab already has Orphan Drug Designation, Rare Pediatric Disease Designation, Priority Review and Fast Track Designation.

“While we are disappointed that the availability of a muscle-targeted treatment approach for patients with SMA has been delayed, we remain enthusiastic about the transformative potential of apitegromab,” Kenneth Hobby, president of Cure SMA, said in the news release. “Muscle strength and motor function are significant unmet needs for many in the SMA community and are fundamental to independence. A gain in motor function can allow someone to participate in important activities of daily living, from self-care to work and social interactions, and as such, we urgently await the availability of the first-ever treatment with the potential to address the muscular component of SMA.”

Spinal muscular atrophy is a rare, progressive and genetic disease that affects motor neurons, which causes progressive weakness in the arms, legs, face and throat. Weakness is often most severe in the trunk.

Depending on severity and symptom onset, patients may lose the ability to speak or walk. Secondary complications include respiratory infections, scoliosis and joint contractures, which is the chronic shortening of muscles and tendons.

The most severe form of SMA, called Type 1, generally manifests before 6 months of age. These children rarely live beyond the age of 2.

Approximately 10,000 to 25,000 Americans have SMA, and about 6 million Americans are carriers of the SMA gene, called Survival Motor Neuron 1 (SMN). Although SMA gene carriers do not exhibit any symptoms, if both parents are carriers, their child has a 25% chance of having the disease.

There is no cure for SMA, but there are therapies that can manage symptoms. Current SMA-targeted treatments are designed to prevent motor neuron loss but do not directly address the muscle, the news release says.

Apitegromab is an investigational, fully human monoclonal antibody. It works by preventing myostatin activation, the process that leads to the development of SMA. It is the first muscle-targeted treatment for SMA to demonstrate clinically meaningful success in a phase 3 trial.

Apitegromab is currently under review by the European Medicines Agency. A decision is anticipated in mid-2026, and a European launch will likely follow in the second half of 2026. Germany is expected to be the first European country with access.

“We are continuing to work closely with Catalent Indiana on the FDA’s manufacturing observations so that we can resubmit the apitegromab BLA as soon as possible,” David L. Hallal, chairman and CEO of Scholar Rock, said in the news release. “We remain focused on working hand-in-hand with the FDA to pursue approval of the first and only muscle-targeted treatment for people living with SMA.”