Study to Evaluate the Safety and Efficacy of Pegvaliase in Adolescents (Ages 12-17) With Phenylketonuria

This study is looking for teenagers aged 12 to 17 (in the UK, this is usually up to 15 for some aspects) who have been diagnosed with PKU. It's important that your current treatment, even if it includes special diets or other medicines, hasn't been able to consistently keep your blood phenylalanine levels low enough. Specifically, your levels need to have been above 600 μmol/L on a couple of recent tests, and generally high over the last year.

You and your family must be willing to work closely with a study dietitian to stick to the special diet required by the study. If you take medication for conditions like ADHD or depression, you need to have been on a stable dose for at least 8 weeks before joining. Also, an adult aged 18 or over must be available and willing to help you with the daily injection and watch you for about an hour afterwards.

There are also some reasons you wouldn't be able to join. For example, if you've ever had pegvaliase before. You also can't be taking any other PKU medicines, or certain types of injectable drugs that contain a substance called polyethylene glycol (PEG), within a specific time before or during the study, unless it's for something like contraception that's been discussed with the study team.

If you decide to take part in this study, you'll first have a screening period to make sure you're a good fit. During the study, you would be randomly placed into one of two groups: either you'll receive the pegvaliase injection every day, or you'll continue to manage your PKU with your special diet alone. You won't get to choose which group you're in, as this helps make the study fair.

The pegvaliase is given as a daily injection. An adult will need to be present to help you with this and to watch you for about an hour afterwards for any reactions. You'll also work closely with a study dietitian to manage your food intake according to the study's plan. Throughout the study, you'll have regular appointments at the clinic for assessments, which will include blood tests to check your phenylalanine levels and monitor your general health. These visits will help the doctors see how you are doing and if the treatment is working. The total duration of the study would be discussed in detail by the study team, including how long you would be receiving the study treatment and how often you'd need to visit the clinic.