Full Breakdown
Scholar Rock's Apitegromab Faces FDA Rejection Due to Manufacturing Issues
9/24/2025, 4:05:21 AM
FDA's Complete Response Letter
On September 23, 2025, the U.S. Food and Drug Administration (FDA) issued a Complete Response Letter (CRL) to Scholar Rock (NASDAQ: SRRK), rejecting the Biologics License Application (BLA) for apitegromab, an investigational treatment for spinal muscular atrophy (SMA). The rejection stemmed from observations made during a routine inspection of the Catalent Indiana LLC facility, a third-party contractor responsible for the drug's fill-finish process. Notably, the FDA did not raise any concerns regarding the safety or efficacy of apitegromab itself.
Background on Apitegromab
Apitegromab is a fully human monoclonal antibody designed to inhibit myostatin, a protein that limits muscle growth. It is the first muscle-targeted treatment for SMA to demonstrate clinical success in a pivotal Phase 3 trial, known as SAPPHIRE, which showed significant improvements in motor function among patients receiving concurrent SMN-targeted therapies like nusinersen (Spinraza) or risdiplam (Evrysdi). The trial involved 188 patients aged 2 to 21 years, and results indicated a statistically significant improvement in motor function measured by the Hammersmith Functional Motor Scale Expanded (HFMSE).
Manufacturing Concerns and Next Steps
The observations at the Catalent facility, which was acquired by Novo Nordisk A/S in December 2024, were not specific to apitegromab. Scholar Rock indicated that Catalent submitted a comprehensive response to the FDA in early August 2025 and has been actively working to address the identified issues. Once these manufacturing concerns are resolved, Scholar Rock plans to resubmit the BLA, with expectations for a swift review by the FDA.
David L. Hallal, Chairman and CEO of Scholar Rock, stated, “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.”
Community Response and Implications
The SMA community has expressed disappointment over the delay in accessing a muscle-targeted treatment. Kenneth Hobby, President of Cure SMA, emphasized the unmet needs for muscle strength and motor function among SMA patients, stating, “A gain in motor function can allow someone to participate in important activities of daily living from self-care to work and social interactions.”
Scholar Rock has also applied for marketing authorization in Europe, where a decision is anticipated in mid-2026, with Germany expected to be the first market for patient access.
Criticism and Market Impact
The rejection of apitegromab has raised concerns among investors and analysts regarding Scholar Rock's future. Following the announcement, Scholar Rock's stock experienced a significant decline. Analysts noted that while the delay is disappointing, the drug's unique mechanism and potential market positioning remain promising.
Despite the setback, some analysts maintain an optimistic outlook, projecting substantial sales for apitegromab once it gains approval. The anticipated launch in Europe and the potential for apitegromab to address muscle deterioration in SMA patients could position Scholar Rock favorably in the competitive landscape of SMA treatments.
Conclusion
Scholar Rock's apitegromab represents a significant advancement in the treatment of spinal muscular atrophy, targeting muscle function directly. However, the recent FDA rejection due to manufacturing issues at a third-party facility has delayed its path to market. The company remains committed to resolving these issues and resubmitting its application, with hopes of providing a much-needed treatment option for SMA patients in the near future.
