The U.S. Food and Drug Administration (FDA) has accepted Scholar Rock's Biologics License Application (BLA) for apitegromab with priority review, marking a significant milestone in the development of new treatment options for spinal muscular atrophy (SMA). The FDA has assigned a Prescription Drug User Fee Act (PDUFA) target action date of September 22, 2025.
Apitegromab is an investigational muscle-targeted treatment designed to provide clinically meaningful improvement in motor function for people living with SMA who are already receiving SMN-targeted treatments. The priority review designation indicates the FDA has determined that apitegromab could offer significant improvement in the safety or effectiveness of SMA treatment.
Novel Approach to SMA Treatment
Unlike existing therapies that target the underlying genetic cause of SMA, apitegromab works through a complementary mechanism. As a selective inhibitor of the activation of myostatin, apitegromab aims to directly address muscle function in SMA patients. This approach positions it as a potential adjunctive therapy to be used alongside SMN-targeted treatments such as nusinersen (Spinraza), risdiplam (Evrysdi), or onasemnogene abeparvovec (Zolgensma).
"The acceptance of our BLA with priority review reflects the significant unmet need that still exists in SMA despite current treatments," said a representative from Scholar Rock. "Our goal is to provide a complementary approach that could further improve outcomes for patients."
Evolving SMA Treatment Landscape
The SMA treatment landscape has seen remarkable progress in recent years. In February 2025, Genentech, a member of the Roche Group, received FDA approval for an Evrysdi (risdiplam) tablet formulation. This approval provides a non-invasive treatment option that can either be swallowed whole or dispersed in water, potentially improving administration for patients with swallowing difficulties.
Additionally, in January 2025, Biogen announced that the FDA had accepted its supplemental New Drug Application (sNDA) for a higher dose regimen of nusinersen for SMA. The European Medicines Agency (EMA) has also validated this application. The proposed higher dose regimen includes a more rapid loading schedule and increased maintenance dosing compared to the currently approved nusinersen (SPINRAZA) regimen.
Ongoing Research and Clinical Trials
The SMA pipeline remains robust, with approximately 18 companies developing over 20 treatment therapies. Key players in this space include Scholar Rock, Biogen, Astellas Pharma, Alcyone Therapeutics, Hoffmann-La Roche, and others.
Several clinical trials are currently underway to evaluate new treatments and optimize existing ones:
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Hoffmann-La Roche is conducting a Phase IV open-label study evaluating the effectiveness and safety of risdiplam administered as an early intervention in pediatric patients with SMA after gene therapy.
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Genentech is investigating the long-term safety and effectiveness of risdiplam in a multi-center, longitudinal, prospective study.
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Biogen is examining the clinical efficacy of nusinersen administered intrathecally at higher doses to SMA participants.
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NMD Pharma A/S is evaluating the efficacy, safety, and tolerability of NMD670 in ambulatory adults with Type 3 SMA.
Understanding Spinal Muscular Atrophy
SMA is a rare genetic neuromuscular disorder affecting approximately 1 in 10,000 live births worldwide. It is caused by mutations in the SMN1 (Survival Motor Neuron 1) gene, resulting in reduced levels of the SMN protein essential for motor neuron survival.
The condition primarily affects voluntary muscles involved in movement, breathing, and swallowing. SMA is classified into different types (0-4) based on age of onset and disease progression, with Type 1 being the most common and severe form, typically presenting in infancy.
Before the approval of disease-modifying therapies in recent years, SMA was the leading genetic cause of infant mortality. However, the introduction of treatments like nusinersen, risdiplam, and onasemnogene abeparvovec has dramatically changed the prognosis for many patients.
Future Outlook
The development of apitegromab and other emerging therapies represents the next wave of innovation in SMA treatment. While current therapies address the underlying genetic cause of the disease, these new approaches aim to further improve outcomes by targeting different aspects of the condition.
"We're seeing a shift toward combination approaches and therapies that can complement existing treatments," noted a neuromuscular disease specialist familiar with SMA research. "The goal is to maximize functional outcomes for patients across all SMA types and ages."
As research continues, the focus is increasingly on optimizing treatment regimens, improving administration methods, and developing therapies that can be used in combination to address multiple aspects of the disease. The priority review for apitegromab signals the FDA's recognition of the continued need for innovation in this field despite recent advances.
With the PDUFA date set for September 2025, the SMA community awaits the FDA's decision on what could become an important addition to the treatment armamentarium for this challenging condition.
