A Study to Investigate Vaccine Responses in Subcutaneous Amlitelimab Treated Atopic Dermatitis Participants Aged 18 Years and Older Compared With Placebo

This is a Phase 2, multicenter, randomized, double-blind placebo controlled, 2-arm study to evaluate the effect of amlitelimab on vaccine antibody responses, and the safety of amlitelimab concurrently administered with non-live vaccines in adult participants with moderate-to-severe atopic dermatitis (AD). The purpose of this study is to compare the immune responses to concomitantly administered Boostrix (tetanus, diphtheria, and acellular pertussis \[Tdap\]) and Pneumovax 23 (PPSV) vaccines in adult participants with moderate-to-severe AD treated with amlitelimab versus placebo. The study will evaluate the percentage of participants achieving a positive anti-tetanus response at Week 16 (primary endpoint) and a positive anti-pneumococcal response at Week 16 (key secondary endpoint). Study details include: The study duration will be up to 36 weeks (for participants not entering the LTS17367 \[RIVER-AD\]). The screening period will be 9 days to 4 weeks. The treatment duration will be up to 16 weeks. The post-treatment safety follow-up period will be16 weeks. The number of visits will be up to 7 (or 6 for those entering LTS17367 \[RIVER-AD\]).

Inclusion Criteria: * Participants must be 18 years of age (when signing informed consent form) * Diagnosis of AD for at least 1 year (defined by the American Academy of Dermatology Consensus Criteria) * Documented history (within 6 months before screening) of either inadequate response or inadvisability to topical treatments * Validated Investigator Global Assessment scale for atopic dermatitis (vIGA-AD) of 3 or 4 at baseline visit * Eczema area and severity index (EASI) score of 12 or higher at baseline * AD involvement of 10% or more of body surface area (BSA) at baseline * Able and willing to comply with requested study visits and procedures * Body weight ≥40 kg and ≤150 kg Exclusion Criteria: * Skin co-morbidity that would adversely affect the ability to undertake AD assessments * Receipt of any vaccine (expect influenza and COVID-19 vaccines) within 3 months prior to screening * Receipt of any pneumococcal vaccine within approximate timeframe of 5 years prior to screening * Prior receipt of two or more doses of Pneumovax 23 at any time * Receipt of any tetanus-, diphtheria-, or pertussis-containing vaccine within approximate timeframe of 5 years prior to screening * Participants for whom administration of the pneumococcal vaccine provided in this study is contraindicated or medically inadvisable, according to local label of the vaccine * Participants for whom administration of the tetanus, diphtheria, and pertussis vaccine provided in this study is contraindicated or medically inadvisable, according to local label of the vaccine * Having received any of the specified therapy within the specified timeframe(s) prior to the baseline visit * Known history of or suspected significant current immunosuppression * Any malignancies or history of malignancies prior to baseline (excluding non-melanoma skin cancer excised and cured \>5 years prior to baseline) * History of solid organ or stem cell transplant * Any active or chronic infection including helminthic infection requiring systemic treatment within 2 weeks prior baseline * Positive for human immunodeficiency virus (HIV), Hepatitis B or hepatitis C at screening visit * Participants with active tuberculosis (TB), latent TB, a history of incompletely treated TB, suspected extrapulmonary TB infection, or who are at high risk of contracting TB The above information is not intended to contain all considerations relevant to a potential participation in a clinical trial.