Study to Evaluate Soquelitinib in Participants With Moderate to Severe AD

Inclusion Criteria: * Adult male or female, ≥18 years of age, as applicable according to local legislation, at Screening. * Diagnosis of AD with onset of symptoms at least 1 year prior to the Screening visit. * Moderate to severe disease at screening and pre-randomization on Day 1 defined by: * EASI ≥16 * Body surface area ≥10% * vIGA ≥3 * PP-NRS average score of ≥4 over a period of 7 days prior to randomization at Day 1. * Documented history of prior topical and/or systemic therapy for AD within 6 months of randomization. * A female participant is eligible if she is not pregnant or breastfeeding, and is either of non-childbearing potential, OR of childbearing potential and agrees to use highly effective birth control Exclusion Criteria: * Other concomitant skin conditions that would interfere with evaluations of the effect of study medication on AD. * Other active skin diseases or skin infections (bacterial, fungal, or viral) requiring systemic treatment within 30 days of the Baseline visit or that could interfere with the appropriate assessment of AD lesions. * Known immunodeficiency syndrome, history of an invasive infection or active non skin-related infection requiring systemic anti-infective treatment within 30 days of Baseline. * History of immunosuppression not related to medication, history of clinically significant medical conditions, or any other reason which in the opinion of the investigator would interfere with the participant's participation in this study. * Have an unstable or uncontrolled illness, including but not limited to cerebrocardiovascular, respiratory, gastrointestinal, endocrine, hematologic, or neurologic disorders that would potentially affect participant safety within the study or confound efficacy and safety assessments.