A Study of Zasocitinib in Adults With Nonsegmental Vitiligo

Inclusion criteria: Participant willingness: 1. Participant is willing and able to understand and fully comply with trial procedures and requirements (including digital tools and applications), in the opinion of the investigator. 2. Participant has provided written informed consent and any required privacy authorization before the initiation of any trial procedures. Disease Characteristics: 3. Participants must have a clinical diagnosis of nonsegmental vitiligo: F-VASI greater than or equal to (\>=) 0.5 and a T-VASI \>= 5 and less than or equal to (\<=) 50 at screening and Day 1. Age and Reproductive Status: 4. Participant is aged \>=18 years to \<=75 years old at the time of consent. 5. Participant meets the following birth control requirement: An individual with potential for pregnancy who is now of nonchildbearing potential with laboratory confirmation of postmenopausal status; or an individual with potential for pregnancy who if sexually active with a nonsterilized individual who produces sperm, agrees to use a highly effective method of contraception from the signing of informed consent throughout the duration of the trial. The use of effective contraception will be required for assigned male sex at birth participants. In the European Union (EU) / European Economic Area (EEA) and the United Kingdom (UK), for participants who elect to use hormonal contraception as a form of highly effective contraception, the investigator must document a favorable benefit-risk assessment to justify the participant's inclusion in the trial at screening and every 3 months during the trial. 6. For participants in the EU/EEA or UK, the investigator must have no reason to believe that the participant would be placed at risk by participating in the trial with regard to the European Commission decision as of 10 March 2023 on measures to minimize risk of serious side effects with Janus Kinase inhibitor (JAKi) (EMA/142279/2023) and the UK MHRA guideline on JAKi: new measures to reduce risks of major cardiovascular events, malignancy, venous thromboembolism, serious infections and increased mortality as of 26 April 2023 (Drug Safety Update volume 16, issue 9). Exclusion Criteria: Target Disease-Related Exclusions: 1. Participant has segmental vitiligo (including mixed vitiligo) or any other congenital or acquired cause of hypopigmentation or depigmentation that could interfere with the diagnosis or assessment of nonsegmental vitiligo. 2. Participant has \>50 percent (%) leukotrichia on the face or \>50% leukotrichia of the body (includes the face), within the skin affected by vitiligo. 3. Participant requires immunomodulatory or immunosuppressive systemic treatment, other than nonsteroidal anti-inflammatory drugs, during the trial period for an immune-related disease (for example, inflammatory bowel disease). 4. Participant has a history of phototherapy (including, but not limited to, broadband Ultra-Violet \[UV\]-B, narrowband UV-B, psoralen and UV-A, excimer or other laser therapy, or tanning booth use) within 8 weeks before Day 1. Use of sunscreen products and protective apparel is recommended when sun exposure cannot be avoided. 5. Participant has concomitant comorbid skin condition that, in the opinion of the investigator, would interfere with the trial assessments. 6. History of any depigmenting or bleaching treatment for vitiligo or other skin disorder (for example, monobenzone or phenol). 7. History of any surgical treatments for vitiligo. 8. History of recent or progressive undiagnosed hearing loss. Recent/Concurrent Infectious Disease Exclusions: 9. Tuberculosis (TB): 1. Participant has history of active TB infection, regardless of treatment status. 2. Participant has signs or symptoms of active TB (including, but not limited to, chronic fever, chronic productive cough, night sweats, or weight loss) as judged by the investigator. 3. Participant has evidence of Latent Tuberculosis Infection (LTBI) as evidenced by a positive QuantiFERON (QFT) result OR 2 indeterminate QFT results and participant does not have documentation of appropriate LTBI prophylaxis or is not able or not willing to initiate appropriate LTBI prophylaxis. Participant remains eligible if there are no signs/symptoms of active TB AND documentation of no history of active TB can be provided AND (1) participant can provide documentation of prior and complete treatment for LTBI (appropriate in duration and type per current local country guidelines) or (2) participant has a positive QFT result or 2 indeterminate QFT results but has initiated prophylaxis (appropriate in duration and type per current local guidelines) a minimum of 2 weeks prior to Day 1. In the EU/ EEA and the UK, participants with evidence of LTBI, regardless of prophylaxis treatment status, must receive approval to participate in the trial from an infectious disease or other TB specialist (for example, pulmonologist). 4. Participant has had any imaging trial during or 6 months prior to screening, including x-ray, chest Computed Tomography (CT), magnetic resonance imaging, or other chest imaging suggesting evidence of current active or a history of active TB. X-ray is required for all participants regardless of QuantiFERON-TB Gold results unless the participant has had normal chest imaging in the 6 months prior to screening. CT imaging is allowed per local sites requirements. 10. Herpes infections: 1. Participant has active herpes virus infection, including herpes zoster or herpes simplex 1 and 2 (demonstrated on physical examination and/or medical history) at screening or Day 1. 2. Participant has history of serious herpetic infection that includes any episode of disseminated disease, multidermatomal herpes zoster, herpes encephalitis, ophthalmic herpes, or recurrent herpes zoster (defined as 2 episodes within 2 years). 11. Non-herpetic viral diseases: 1. Participant has presence of Hepatitis C Virus (HCV) antibody and a posi