Key Inclusion Criteria:  Age ≥ 18 years to 65 years. Participant has a body mass index of ≥ 18 kg/m2 to ≤ 35 kg/m2.  Participants who are overtly healthy as determined by medical evaluation including medical history, physical examination, laboratory tests, and ECG monitoring at Screening and at Baseline.  Additional Inclusion Criteria for Participants with Moderate Atopic Dermatitis  Participant has moderate atopic dermatitis with a minimum of 5% and a maximum of 40% BSA involvement, and an IGA score of 2 or 3. Participant has had a confirmed diagnosis of atopic dermatitis for at least 6 months.  All participants must be using an emollient and should continue to use this once daily (or more, as needed) for at least 14 days prior to randomisation, and must continue this treatment once daily (or more, as needed) throughout the study.  Additional Inclusion Criteria for Participants with Moderate Psoriasis  Participant has moderate plaque psoriasis with plaque covering BSA of ≥3% and ≤10% and meets both of the following additional criteria:  PASI score of ≥6 and ≤15, and PGA score of 2 or 3.  Participant has a confirmed diagnosis of plaque psoriasis for at least 6 months.  Additional Inclusion Criteria for Participants with Mild Asthma  Participant has a diagnosis of stable asthma for at least six months FeNO of ≥40ppb. FEV1 ≥70% of predicted normal.  Key Exclusion Criteria:  Participant has received live attenuated vaccination within 6 weeks prior to Screening or intends to have such a vaccination during the course of the study (non-live vaccines are permitted). Participant requires treatment with an anti-inflammatory drug during the study period. Participant has an active infection (e.g. sepsis, pneumonia, abscess) or has had an infection requiring antibiotic treatment within 6 weeks prior to study intervention administration. Participant has renal or liver impairment Participant has active neoplastic disease or history of neoplastic disease within 5 years of Screening Participant has undergone major surgery within 4 weeks prior to Screening. Any known cardiac abnormality Participant has a known history of human immunodeficiency virus (HIV) Known, active hepatitis A, hepatitis B (HBV), or hepatitis C (HCV) infection Participant with any type of GI tract disease Participants with a history of any serious psychiatric condition; or on therapy for any psychiatric condition The participant has taken any over-the-counter (OTC) or prescription medication, within 14 days prior to baseline (Day -1); or anticipates an inability to abstain from these products for the duration of the study period The participant has a significant history of drug abuse or regular use of illicit drugs or a history of alcohol abuse within 1 year prior to Screening or has tested positive for drugs of abuse or alcohol at Screening or at baseline.  The participant has had an acute, clinically significant illness within 30 days prior to the first dose of study intervention.  Additional Exclusion Criteria for Participants with Atopic Dermatitis  Participant is receiving systemic immunosuppressive or non-biologic atopic dermatitis therapy or has received such therapy within 4 weeks prior to Screening. Participant has received treatment with biologic agents within 12 months prior to first dose. Participant continues to use topical medications, other than emollients, that could affect atopic dermatitis 2 weeks prior to the start of dosing.  Participant intends to continue to use sunbeds and/or increase their sun exposure significantly from their normal lifestyle  Additional Exclusion Criteria for Participants with Psoriasis  Psoriasis restricted to scalp, palm, and/or soles only. Non-plaque type of psoriasis Participant is receiving systemic immunosuppressive or nonbiologic psoriasis therapy or has received such therapy within 4 weeks prior to Screening Participant has received treatment with biologic agents within 12 months prior to first dose. Participant continues to use topical medications that could affect psoriasis within 2 weeks prior to the start of dosing  Participant intends to continue to use sunbeds and/or increase their sun exposure significantly from their normal lifestyle  Additional Exclusion Criteria for Participants with Asthma  History of life-threatening asthma, or a visit to the emergency department for asthma in the 6 months prior to screening, or exacerbation requiring oral corticosteroids within the previous 3 months. Smoker or nicotine user within the 3 months prior to screening; or a previous smoker with a greater than 10 pack year history. Other significant non-reversible pulmonary disease  Use of the following medicines within the specified time-frame prior to screening:  Long-acting inhaled β2-agonists: 8 weeks. Note: short-acting inhaled β2-agonists are permitted as required. Anti-IgE therapy: 6 months Inhaled corticosteroids: 8 weeks Oral or Injected corticosteroids: 8 weeks Intranasal or topical steroids: 4 weeks Leukotriene antagonists: 2 weeks Long-acting muscarinic antagonist: 8 weeks Xanthines (excluding caffeine), anticholinergics, cromoglycates: 1 week.