Study Evaluating the Efficacy and Safety of Povorcitinib in Adults With Chronic Spontaneous Urticaria

Inclusion Criteria: Participants are eligible to be included in the study only if all of the following criteria apply: * CSU diagnosis for ≥ 3 months prior to screening. * CSU refractory to second-generation H1 antihistamines * Participants must have been on a stable dose of second-generation H1 antihistamine, and must agree to maintain the stable dose of second-generation H1 antihistamine throughout study. * Willingness and ability to comply with the study Protocol and procedures. * Further inclusion criteria apply Exclusion Criteria: * Treatment with an anti-IgE biologic (eg, omalizumab) within 8 weeks prior to screening. * Clearly defined underlying etiology for chronic urticarias other than CSU * Other cutaneous or systemic diseases with chronic itching or with symptoms of urticaria or angioedema. * Women who are pregnant (or who are considering pregnancy) or breastfeeding. * Concurrent or history of Thrombocytopenia, coagulopathy, or platelet dysfunction, Venous and arterial thrombosis, deep vein thrombosis, pulmonary embolism, stroke, moderate to severe heart failure (NYHA Class III or IV), cerebrovascular accident, MI, coronary stenting, or CABG surgery, other significant cardiovascular diseases or uncontrolled hypertension * Recipient of an organ transplant that requires continued immunosuppression. * Any malignancies or history of malignancies with the exception of adequately treated or excised nonmetastatic basal cell or squamous cell cancer of the skin, or cervical carcinoma in situ. * Chronic or recurrent infectious disease. * Further exclusion criteria apply.