A Phase III Study to Evaluate the Efficacy and Safety of Benralizumab in Patients With Hypereosinophilic Syndrome (HES)

To be considered for this study, you must be 12 years of age or older and have a confirmed diagnosis of Hypereosinophilic Syndrome (HES). It's important that your HES treatment has been stable for at least 4 weeks before the study starts, and you must have a certain level of eosinophils in your blood at the beginning. You'll also need to have experienced HES symptoms or complications recently, or a history of two or more HES flare-ups within the past year. Crucially, tests must show that your HES is not caused by a specific genetic change (called FIP1L1-PDGFRA).

Part of the entry process will involve a short course of steroid medication to see how your eosinophil levels respond. If your eosinophil count doesn't drop enough after these steroids, you might not be eligible for this study. If you're a woman who could become pregnant, you'll need to agree to use effective contraception throughout the study.

There are also other medical criteria that the study doctors will check to make sure the study is safe and appropriate for you. Your study doctor will discuss all the detailed requirements with you to assess if you are a good fit for this research.

If you join this study, it will involve several visits to the clinic over a period of time. Initially, there's a short 3-day screening period to check if you meet all the requirements. If eligible, you’ll then be randomly assigned (like tossing a coin) to receive either benralizumab or a placebo. Neither you nor your study doctor will know which one you are receiving during the first 24 weeks. Both treatments are given as injections under the skin every four weeks.

Throughout the study, you'll continue with your usual HES medication. The study team will closely monitor your HES symptoms, carry out blood tests to check your eosinophil levels, and ask about any side effects you experience. There will also be some questions about your quality of life. After the initial 24-week period, all participants will be offered benralizumab. The total duration of your participation will depend on when you join and how long the study continues, but the initial treatment period is 24 weeks, followed by an open-label extension that you could participate in.