A Study to Learn About the Study Medicine Called Tilrekimig in People With Moderate-to-Severe Eczema

The purpose of this study is to find out how well tilrekimig works, how safe it is, and how it affects the body when used together with medicated creams or ointments in adults and adolescents with moderate to severe atopic dermatitis (eczema). Eczema (also called atopic dermatitis) is a common skin condition that makes the skin dry, itchy, red, and irritated.

* This study is seeking participants who: Are aged 12 years or older. * Were confirmed to have atopic dermatitis (AD) at least 12 months ago. * Are not having an effective treatment result from medicines that are applied on skin for AD. * Are considered by their doctors to have moderate to severe AD.

Participants in this study will randomly receive either tilrekimig or placebo at a 2:1 ratio. A placebo does not have any medicine in it but looks just like the medicine being studied. The study treatment period will be 24 weeks. The last dose of study treatment will be administered at week 20.

Some participants will join the long-term extension study C4531008 at week 24. A long-term extension study is an additional study that participants may be able to join after completing the main study. It allows researchers to continue collecting information about how well the study medicine works and how safe it is when used for a longer period of time. Participants who do not join this study will enter a 12-week safety follow-up period. This period ends 16 weeks after their last study treatment dose.