A Study of BBT001 in Healthy Volunteers (HVs) and in Adult Patients With Atopic Dermatitis (AD)

This is a Phase 1, randomized, blinded, placebo controlled, single ascending dose (SAD) and multiple ascending dose (MAD) study of BBT001 in healthy volunteers (HVs) and adult patients with moderate to severe Atopic Dermatitis (AD).

The study consists of five parts: * Part A (single dose of IV administration in HVs in sequential ascending dose cohorts, SAD IV in HVs part) * Part B (3 repeat doses of IV administration in HVs in sequential ascending dose cohorts, multiple ascending dose (MAD) IV in HVs part) * Part C (3 repeat doses in participants with moderate to severe AD, MAD IV in patients part) * Part D (single dose of SC administration in HVs in sequential ascending dose cohorts, SAD SC in HVs part) * Part E (4 repeat doses in participants with moderate to severe AD, MAD SC in patients part)

Key Inclusion Criteria (Part A, B, C, D) 1. Age of 18-65 years. 2. Body mass index between 18-32 kg/m², capped at 120 kg. 3. Negative pregnancy tests for women of childbearing potential. 4. Willingness to refrain from alcohol consumption for 24 hours prior to each study visit. 5. Non-smokers, healthy current smokers (≤5 cigarettes/day), or ex-smokers. 6. Adequate contraception use (for men and women of childbearing potential). 7. No clinically significant abnormalities or history of relevant diseases. Key Inclusion Criteria (Parts C and E only) 1. Must have dermatologist-confirmed chronic atopic dermatitis (≥12 months). Inadequate response to topical treatments or where they are medically inadvisable. 2. Moderate to severe atopic dermatitis 3. Validated investigator's global assessment for atopic dermatitis (vIGA-ADTM) score ≥3 4. Atopic lesions cover ≥10% of body surface area (BSA) 5. Average peak pruritus numeric rating scale (PP-NRS) score ≥4 in the 7 days before randomization. Key Exclusion Criteria for (Part A, B, C, D) 1. Significant health issues, such as: diabetes, positive tests for human immunodeficiency virus (HIV), hepatitis C virus (HCV), or hepatitis B surface antigen (HBsAg), immunodeficiencies, autoimmune diseases, or cancer, history of conditions predisposing to infections. 2. History of major metabolic, dermatological, liver, kidney, hematological, or other significant disorders. 3. Clinically relevant abnormal lab results, including low blood counts, liver issues, or abnormal kidney function. 4. Positive drug/alcohol tests or abnormal vital signs at screening or Day -1. 5. Abnormal Electrocardiogram (ECG) findings 6. History of drug/alcohol abuse in the past 2 years. 7. Donated \>500mL blood within 2 months of screening. 8. History of severe allergic reactions or hypersensitivity. Key Exclusion Criteria for (Parts C and E only) 1. Skin diseases other than atopic dermatitis, significant tattoos, or scarring. 2. Receipt of immunoglobulin or blood products within 30 days. 3. Atopic dermatitis with ocular symptoms or chronic ocular steroid use. 4. Chronic pruritus from conditions other than atopic dermatitis. 5. Acute/treated infections or chronic skin infections. 6. Current use of sedating antihistamines or corticosteroids.