A Study to Assess Safety and Efficacy of Avalglucosidase Alfa Administered Every Other Week in Pediatric Patients With Infantile-onset Pompe Disease Previously Treated With Alglucosidase Alfa

This study is for children and teenagers who have been diagnosed with infantile-onset Pompe disease. They must be between 6 months and 17 years old. A key requirement is that they should have already been receiving the standard treatment, alglucosidase alfa, for at least six months before joining the study. This study is specifically for those who, despite receiving the current treatment, are still showing signs of their disease getting worse or not getting better enough. This could include issues with their breathing, movement, or heart.

To be considered for the study, doctors need to confirm the Pompe disease diagnosis by checking for a specific enzyme deficiency. Girls and young women who could become pregnant will need to have a negative pregnancy test and not be breastfeeding. The study aims to help children whose hearts were affected when they were first diagnosed with Pompe disease.

However, some things would mean a child cannot join the study. For example, if a child's body has developed a very strong immune reaction (high antibody levels) to the existing medicine, alglucosidase alfa, they would not be able to take part. Also, if they have other health conditions that might make it unsafe for them to be in the study, they would be excluded.

If your child takes part in this study, it will involve several stages over a long period, potentially up to 9 years and 4 months. Firstly, there's a screening period of about two weeks (which might sometimes be extended to four weeks) to check if your child is suitable for the study. During this time, they'll have various tests to confirm their diagnosis and current health status.

After screening, your child will enter the treatment phase. They will receive the study medicine, avalglucosidase alfa, as an intravenous infusion (a drip into a vein) every other week. Initially, this treatment period will last for about 25 weeks. Following this, there's a much longer extension period, potentially lasting several years. Throughout this time, your child will have regular visits to the clinic for assessments. These will include checks on their breathing, muscle strength, heart function, and overall health to see how they are responding to the new medicine.

Some children in the study might be assigned to different dose levels of the new medicine, and some might continue with the existing medicine, alglucosidase alfa, for comparison. This will be decided by the study doctors, and they will explain which treatment group your child would be in. After the treatment periods, there will be a final four-week observation period to monitor your child's health after finishing the study medication.