⁃ Part A Healthy study participants

• Participant must be 18 to 55 years of age inclusive at the time of signing the informed consent form (ICF)

• Participant must be overtly healthy as determined by medical evaluation including medical history, physical examination, laboratory tests, and cardiac monitoring

• Participant has a body mass index (BMI) within the range 18 to 30 kg/m2 (inclusive)

• Participant can be male or female and must agree to use contraception

⁃ Part B Participants with moderate to severe Atopic dermatitis (AtD)

• Participant must be 18 to 65 years of age inclusive at the time of signing the ICF

• Participant has moderate or severe AtD that has been present for at least 12 months prior to initiating the study (signing of the ICF) and with:

• A validated Investigator Global Assessment (vIGA) score ≥3 at Screening and Baseline

• An Eczema Area and Severity Index (EASI) score of ≥14 at Screening and ≥16 at Baseline

• Pruritis Numerical Rating Scale (NRS) ≥3 at Screening and Baseline

• ≥10 % body surface area (BSA) of AtD involvement at Screening and Baseline

• Either documented recent history (within 6 months before the Screening Visit) of inadequate response to treatment with topical medications (regular use of topical corticosteroids \[TCS\] or topical calcineurin inhibitors \[TCIs\]) or when topical treatments are confirmed to be otherwise medically inadvisable (eg, because of important side effects or safety risks)

• Participant has a BMI within the range 18 to 35 kg/m2 (inclusive)