Study to Assess the Efficacy, Safety, and Tolerability of Vixarelimab in Reducing Pruritus in Prurigo Nodularis

Inclusion Criteria (apply to both Phase 2a and Phase 2b unless otherwise specified):

1. Male or female aged 18 to 75 years (Phase 2a), 18 to 80 years (Phase 2b)

2. Have clinical diagnosis of prurigo nodularis for at least 6 months

3. Have at least 10 nodules (Phase 2a), 20 nodules (Phase 2b) at the Screening Visit and Day 1

4. Moderate to severe pruritus (Phase 2a); severe pruritus (Phase 2b)

5. Female subjects of childbearing potential must have a negative pregnancy test, be nonlactating, and having agreed to use a highly effective method of contraception, as specified in the protocol, from the Screening Visit until 16 weeks after final study drug administration

6. Able to comprehend and willing to sign an Informed Consent Form and able to abide by the study restrictions and comply with all study procedures for the duration of the study

Exclusion Criteria (apply to both Phase 2a and Phase 2b unless otherwise specified):

1. Use of prohibited medications within the indicated timeframe from Day 1

2. Is currently using medication known to cause pruritus

3. Presence of any inflammatory, pruritic, and/or fibrotic skin condition other than moderate to severe prurigo nodularis or atopic dermatitis unless approved by the Sponsor

4. Laboratory abnormalities that fall outside the windows specified in the protocol at the Screening Visit

5. Has an active infection, including skin infection

6. Any medical or psychiatric condition which, in the opinion of the Investigator or the Sponsor, may place the subject at increased risk as a result of study participation, interfere with study participation or study assessments, affect compliance with study requirements, or complicate interpretation of study results