Depemokimab in Participants With Hypereosinophilic Syndrome, Efficacy, and Safety Trial

Inclusion Criteria:

• Participants who are greater than or equal (>=) 40 kilogram (kg) at Screening Visit

• Participants who have a documented diagnosis of HES prior to Visit 2.

• A history of 2 or more HES flares within the past 12 months prior to Visit 1.

• A female participant is eligible to participate if she is not pregnant orbreastfeeding, and one of the following conditions applies: a) woman ofnon-childbearing potential (WONCBP) Or b) woman of childbearing potential (WOCBP)and using a contraceptive method that is highly effective, with a failure rate ofless than (<) 1 percentage (%).

• Capable of giving signed informed consent.

Exclusion Criteria:

• Participants with HES disease manifestations which in the opinion of theinvestigator may put the participant at unacceptable risk from study participationor confound interpretation of efficacy or safety data.

• Participants with chronic or ongoing active infections requiring systemic treatmentor a pre-existing parasitic infestation within 6 months prior to Visit 1.

• Participants with a known immunodeficiency (e.g., Human Immunodeficiency Virus [HIV]), other than that explained by the use of OCS or other therapy taken for HES.

• Participants with a history of or current lymphoma.

• Participants with current malignancy or previous history of cancer in remission forless than 5 years prior to Visit 1. Participants that had localized carcinoma (i.e.,basal or squamous cell) of the skin which was resected for cure will not beexcluded.

• Participants with a haematologic malignancy with hypereosinophilia in which HES isnot the primary diagnosis, e.g., chronic myeloid leukaemia, myelodysplasticsyndrome, chronic eosinophilic leukaemia-not otherwise specified.

• Cirrhosis or current unstable liver or biliary disease per investigator assessment.

• Participants who have severe or clinically significant cardiovascular diseaseuncontrolled with standard treatment.

• Participants with current diagnosis of vasculitis.

• Hypereosinophila with no clinical symptoms and/or proof of organ dysfunction.

• Clinical diagnosis of Eosinophilic granulomatosis with polyangiitis (EGPA).

• Participants with an allergy/ intolerance to a monoclonal antibody or biologic, orany of the excipients of the investigational product.

• Participants who have a previous documented failure with anti-interleukin (IL)-5/5Rtherapy.

• Participants who have received monoclonal antibodies (mAb) within 30 days or 5half-lives, whichever is longer, prior to Visit 1.

• Participants who test positive for the FIP1L1-PDGFRα fusion gene.

• QT interval corrected for heart rate according to Fridericia's formula (QTcF) ≥450milliseconds (msec) or QTcF ≥480 msec for participants with Bundle Branch Block atScreening Visit 1.

• Participants who are not responsive to OCS based on clinical response or bloodeosinophil counts in the opinion of the Investigator.

• Participants who are pregnant or breastfeeding.