Depemokimab Study for Hypereosinophilic Syndrome (HES): This study lasts 52 weeks and checks if a drug called depemokimab is safe and helps people with HES. HES is when your body makes too many eosinophils, a type of white blood cell. These cells can cause problems if there are too many. The study is "randomized," meaning you are randomly chosen to get the real medicine or a "placebo" (a fake treatment) without knowing which one you get. You must already be on stable HES medicine to join.

To qualify, you need to have had at least two flare-ups of HES in the past year and have a blood eosinophil count of 1,000 or more cells per microliter. People with certain infections, cancers, or other health problems can't join.

• Participants will continue their usual HES treatment and either get depemokimab or placebo.
• The study involves multiple visits and tests to check your health and the medicine's effect.
• Women must not be pregnant or breastfeeding and follow birth control guidelines if needed.