A Phase 1/1b Study to Evaluate Safety, Tolerability and Pharmacokinetics of ZL-1503 in Healthy Volunteers and Participants With Moderate to Severe Atopic Dermatitis

This is a phase 1/1b randomized, double blind, placebo-controlled, single dose escalation (SAD) and multiple dose escalation (MAD) study to evaluate the safety, tolerability, and pharmacokinetics (PK) of ZL-1503 in healthy volunteers and participants with moderate to severe atopic dermatitis (AD)

Inclusion Criteria: * Part A: 1. Healthy male and female volunteers, 18-65 years of age 2. Body mass index (BMI) between ≥ 18.5 and \< 32.5 kg/m2 3. Negative pregnancy tests for women of childbearing potential. * Part B: 1. 18-65 years of age; 2. BMI between ≥18.5 and \500mL blood within 2 months of dosing. * For Part B only: 1. Presence of dermatologic conditions and/or comorbidities that might confound the diagnosis of AD and/or might interfere with study assessments. 2. Uncontrolled chronic disease that might require bursts of oral corticosteroids. 3. Any other sound medical, psychiatric, and/or social reason as determined by the investigator.