Sanofi's Nexviazyme hits all endpoints in infantile Pompe phase 3
Sanofi has reported that Nexviazyme (avalglucosidase alfa) met every primary and secondary endpoint in the Baby-COMET phase 3 study, a single-arm, open-label trial evaluating the enzyme replacement therapy in treatment-naïve infants aged six months and under with infantile-onset Pompe disease. The company said it intends to file for a US label extension in the second half of 2026, adding the most severe form of Pompe disease to an indication that currently covers late-onset patients aged one year and older.
The primary endpoint was the proportion of participants alive and free of invasive ventilation at 52 weeks of treatment. Secondary endpoints included ventilator-free survival at 12 and 18 months of age, alongside numerical improvements at week 52 in left ventricular mass Z-score, Alberta Infant Motor Scale score, and urinary glucose tetrasaccharide, a biomarker of glycogen clearance. Seventeen participants received intravenous Nexviazyme at 40 mg/kg every other week. The full dataset is scheduled for presentation on 8 July 2026 at the 19th International Congress on Neuromuscular Diseases in Florence.
Safety and clinical context
Sanofi reported a clean safety read-across in Baby-COMET. There were no serious treatment-related adverse events, no deaths, and no discontinuations. Infusion-associated reactions occurred in 29.4% of participants, a rate the company described as manageable and consistent with the established profile of avalglucosidase alfa.
Priya S. Kishnani, Professor of Pediatrics and Division Chief of Medical Genetics at Duke University Medical Center, who was involved in the study, said the findings show "the potential of avalglucosidase alfa to support ventilator-free survival in infants, alongside encouraging cardiac and motor outcomes." Kishnani noted that IOPD typically manifests within the first days or weeks of life, making early intervention critical to survival beyond the first year.
Without treatment, IOPD leads to heart failure and death within the first year of life in most cases. The condition is caused by a deficiency of the acid alpha-glucosidase (GAA) enzyme, leading to glycogen accumulation in skeletal and cardiac muscle.
Market context and regulatory outlook
Nexviazyme is already approved in Europe under the name Nexviadyme for both LOPD and IOPD, having received EMA authorisation in 2022. In the US, however, the current FDA-approved label is restricted to LOPD in patients aged one year and older, meaning IOPD infants have been outside the approved indication. A successful US label extension would close that gap and directly compete with alglucosidase alfa, marketed as Myozyme and Lumizyme, the established standard of care from which Sanofi positions Nexviazyme as a meaningfully differentiated successor, citing approximately 15-fold higher mannose-6-phosphate receptor binding affinity.
The rare-disease enzyme replacement market for lysosomal storage disorders is well established but continues to evolve, with several academic and commercial groups exploring next-generation approaches including gene therapy as potential long-term alternatives to infused ERT. For IOPD specifically, the short treatment window at birth and the urgency of early diagnosis give any approved ERT a structural advantage over gene therapy candidates, which remain in earlier-stage development for this indication.
Sanofi's submission timing in H2 2026 would place it within a regulatory environment where the FDA has shown continued willingness to support rare-disease label expansions on the basis of single-arm studies when the disease is severe and the unmet need is well documented. The Baby-COMET trial design, with 17 participants, is small by conventional standards, but is typical for an ultra-rare paediatric indication where large randomised trials are neither feasible nor ethically straightforward. Investors will look for the full dataset presentation in Florence for hazard estimates and longer-term durability signals before drawing conclusions about the label extension's commercial impact.