Safety, Tolerability and PK of ATTO-1310 in Healthy Volunteers and Patients With Atopic Dermatitis and Patients With Chronic Pruritus

Parts 1 \& 2 (Healthy Volunteers) Key Inclusion Criteria: * Any sex or gender who is 18 to 65 years old * Body weight of 50 to 125 kg and body mass index (BMI) between 18.5 and 35 kg/m2 * Considered in good general health based on medical history, physical exam, 12-lead ECG, screening clinical laboratory findings, and vital signs * Negative pregnancy test for subjects of child-bearing potential * Use of highly effective forms of birth control Part 3 (Subjects with Atopic Dermatitis) Inclusion Criteria: * Any sex or gender who is 18 to 65 years old * Body weight of 50 to 125 kg and BMI between 18.5 and 40 kg/m2 * Clinically confirmed diagnosis of active AD * At least a 1-year history of AD and had no significant flares in AD for at least 4 weeks before Screening * Baseline weekly mean of daily PP-NRS ≥ 7 at Day 1 * EASI score of ≥ 7 at Screening and Day 1 * vIGA-AD score of ≥ 3 at Screening and Day 1 * Use of topical bland emollient (moisturizer) once or twice daily for at least 5 of the 7 days immediately before Day 1 and agrees to continue using that same emollient at the same frequency throughout the study * Negative pregnancy test for subjects of child-bearing potential * Use of highly effective forms of birth control Part 4 (Subjects with Chronic Pruritus) Inclusion Criteria: * Any sex or gender who is 18 to 85 years old * Body weight of 50 to 125 kg, inclusive, and BMI between 18.5 and 40 kg/m2 * Has had chronic pruritus for at least 6 months and is unresponsive to …