A Study to Evaluate the Efficacy and Safety Study of Povorcitinib in Participants With Prurigo Nodularis (STOP-PN1)

Inclusion Criteria: * Male and female participants 18 to 75 years of age. * Clinical diagnosis of PN for at least 3 months prior to Screening visit. * Pruritus, defined as an average Itch NRS score ≥ 7 during the 7 days prior to Day 1/Baseline. * Total of ≥ 20 pruriginous lesions on ≥ 2 different body regions (both legs, and/or both arms, and/or trunk) at Screening and Day 1/Baseline. * Documented history of treatment failure, demonstrated intolerance, or contraindication to a previous PN treatment. * Willingness to avoid pregnancy or fathering children. Exclusion Criteria: * Chronic pruritus due to a condition other than PN or neuropathic and psychogenic pruritus. * Diagnosis of PN secondary to medications. * Active AD lesions (signs and symptoms other than dry skin) within 3 months prior to Screening visit. * Women who are pregnant (or are considering pregnancy) or breastfeeding. * Medical history including thrombocytopenia, coagulopathy or platelet dysfunction; venous and arterial thrombosis, deep vein thrombosis, pulmonary embolism, stroke, moderate to severe heart failure, cerebrovascular accident, myocardial infarction, or other significant cardiovascular diseases; Q-wave interval abnormalities; disseminated herpes zoster or dermatomal herpes zoster; disseminated herpes simplex; chronic/recurrent infections; malignancies. * Evidence of infection with TB, HBV, HCV or HIV. * History of failure to any topical or systemic JAK or TYK2 inhibitor as treatment of PN or any inflammatory disease. * Laboratory values outside of the protocol-defined ranges. Other protocol-defined Inclusion/Exclusion Criteria apply.