A Study to Evaluate Efficacy and Safety of Povorcitinib in Participants With Nonsegmental Vitiligo (STOP-V1)

Inclusion Criteria: * Aged ≥ 18 years. * Clinical diagnosis of nonsegmental vitiligo and meet the following: * T-BSA ≥ 5% * T-VASI score ≥ 4 * F-BSA ≥ 0.5% * F-VASI score ≥ 0.5 * Agreement to discontinue all agents and procedures used to treat vitiligo from screening through the final safety follow-up visit. * Willingness to avoid pregnancy or fathering children. Exclusion Criteria: * Other forms of vitiligo or skin depigmentation disorders. * Clinically significant abnormal TSH or free T4 at screening. * Use of laser or phototherapy within 8 weeks and dihydroxyacetone within 4 weeks prior to Day 1. * Current or past use of the depigmenting agent monobenzyl ether of hydroquinone including Benoquin®. * History of melanocyte-keratinocyte transplantation procedure or other surgical treatment for vitiligo. * Spontaneous and significant repigmentation within 6 months prior to screening. * Women who are pregnant, considering pregnancy, or breast feeding. * 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 recurrent dermatomal herpes zoster; disseminated herpes simplex; chronic/recurrent infections; malignancies. * Evidence of infection with TB, HBV, HCV or HIV. * History of failure to JAK inhibitor treatment of any inflammatory disease. * Laboratory values outside of the protocol-defined ranges. Other protocol-defined Inclusion/Exclusion Criteria may apply.