This is a single-center, open-label, randomized, single-dose, parallel, Phase 1, 4-arm study designed to determine the bioequivalence and investigate the safety and tolerability profiles of subcutaneous amlitelimab delivered by 2 different devices at 2 different total doses in healthy adult participants.

Inclusion Criteria:

• Male and/or female participant, between 18 and 55 years of age, inclusive, at the time of signing the informed consent form (ICF).
• Certified as healthy by a comprehensive clinical assessment [detailed medical history and complete physical examination including neurological exam (at screening and D1), skin, and mucous membranes].
• Body weight between 50.0 and 100.0 kg, inclusive, if male, and between 40.0 and 90.0 kg, inclusive, if female, body mass index between 18.0 and 30.0 kg/m2, inclusive.

Exclusion Criteria:

• Any history or presence of clinically relevant cardiovascular, pulmonary, gastrointestinal, dermatologic, hepatic, renal, metabolic, hematological, neurological, osteomuscular, articular, psychiatric, systemic, ocular, gynecologic (if female), or infectious disease, or signs of acute illness.
• Known history of significant immunosuppression or suspected current significant immunosuppression, including history of invasive opportunistic or helminthic infections despite infection resolution or otherwise recurrent infections of abnormal frequency or prolonged duration.
• Any malignancies or history of malignancies prior to baseline (except for non-melanoma skin cancer that has been excised and cured for more than 5 years prior to baseline).
• History of solid organ (including corneal transplant) or stem cell transplant.
• Any pre-planned major elective surgery known about at baseline visit that in the Investigator's opinion would impede participation in the study.
• Frequent headaches and/or migraine, recurrent nausea and/or vomiting (for vomiting only: more than twice a month).
• Blood donation, any volume, within 2 months before inclusion.
• Any nicotine use within 4 weeks before study inclusion. Regular smoking more than 5 cigarettes or equivalent in nicotine per week, unable to stop smoking or using nicotine for duration of the study.
• If female, pregnancy (defined as positive beta human chorionic gonadotropin [β-HCG] blood test), breast feeding.

The above information is not intended to contain all considerations relevant to a participant's potential participation in a clinical trial.

Qualified researchers may request access to patient level data and related study documents including the clinical study report, study protocol with any amendments, blank case report form, statistical analysis plan, and dataset specifications. Patient level data will be anonymized and study documents will be redacted to protect the privacy of trial participants. Further details on Sanofi's data sharing criteria, eligible studies, and process for requesting access can be found at: https://vivli.org

This study is open-label. Participants, investigators, and study members have access to treatment assignment.