Evaluation of NM26-2198 in Healthy Subjects and in Patients With Moderate-to-severe Atopic Dermatitis (AD)

Inclusion Criteria:

1. SAD: Non-Asian ethnicity with grandparents and parents of non-Asian descent orJapanese descent having all four Japanese grandparents born in Japan.

2. SAD and MAD in Healthy Volunteers: Male or female aged 18 to 55 years; MAD: Male orfemale ≥18 years of age.

3. ALL COHORTS: Weight of 45 kg to 100 kg and BMI of 18.0 to 30.0 kg/m2.

4. SAD and MAD in Healthy Volunteers: Non-childbearing, non-breastfeeding females ormales willing to use double barrier contraception or abstention from sex and spermdonation during the study; MAD: Males willing to use double barrier contraception orabstention from sex and sperm donation during the study; non-childbearing females orfemales of childbearing potential using protocol-defined method contraception, andwho is not pregnant, lactating, or breastfeeding.

5. MAD: Diagnosis of chronic AD.

6. MAD: EASI score ≥16.

7. MAD: vIGA-AD™ score of ≥3.

8. MAD: Atopic lesions cover ≥10% of body surface area (BSA).

9. MAD: PP-NRS score ≥4.

10. MAD: Daily use of non-prescription emollient.

Note: Other protocol-defined Inclusion criteria apply.

Exclusion Criteria:

1. SAD and MAD in Healthy Volunteers: Any clinically-relevant medical history or lababnormality, including positive test for SARS-CoV-2, Hepatitis B or C, or HIV; MAD:Clinically-significant, abnormal laboratory findings, or positive test forSARS-CoV-2, Hepatitis B or C, or HIV.

2. ALL COHORTS: Clinically important ECG abnormalities or history/evidence thereof.

3. SAD and MAD in Healthy Volunteers: Use of prescription or non-prescriptionmedications (except occasional use of paracetamol).

4. MAD: Diagnosis of protocol-specified skin diseases other than AD, or history ofother significant skin condition that could interfere with study assessments.

5. MAD: History or ongoing allergy/hypersensitivity or history, or history ofhypersensitivity to biological drugs.

6. MAD: Recent receipt of immunoglobulin or blood products.

7. MAD: Recent treatment with protocol-specified investigational treatments, or anyprior treatment with dupilumab, tralokinumab, lebrikizumab, nemolizumab, or otherprotocol-specified drugs.

8. MAD: AD with recent ocular involvement requiring chronic ocular corticosteroidtreatment.

9. MAD: Chronic pruritis due to conditions other than AD.

10. MAD: Acute AD superinfection, recent superficial skin infection, or otherchronic/acute infection requiring protocol-defined treatments.

11. MAD: Recent use of sedating antihistimines, systemic corticosteroids, cytotoxictreatments, other immunosuppressive/immunomodulating agents, and otherprotocol-specified prohibited medications.

12. MAD: Recent topical corticosteroid or prescription moisturizer use.

Note: Other protocol-defined Exclusion criteria apply.