This study is for people aged 12 and older with moderate-to-severe atopic dermatitis (AD), a skin condition causing itchy and inflamed skin. The study will compare the effects of a medicine called amlitelimab, given as an injection under the skin, to a placebo, which is a treatment with no active medicine. The study is "double-blind," meaning neither the participants nor the researchers know who is getting the real medicine or the placebo.

Participants can expect up to 44 weeks in the study, including a screening period, treatment for 24 weeks, and a follow-up. Those joining an extension study may spend up to 28 weeks in the main study. There will be up to 10 visits, or 9 for those in the extension study.

• Participants must have had atopic dermatitis for at least 1 year and meet other health conditions.
• Those with certain health issues like infections or certain past medical histories may not join.
• The study requires commitment to visits and procedures and offers a chance to continue in an extension study.