Study to Evaluate the Efficacy and Safety of Deuruxolitinib in Japanese Adults With Severe Alopecia Areata

Inclusion Criteria: * Written informed consent has been obtained. * Japanese subjects with severe alopecia areata who are between 18 and 65 years of age, inclusive, at the time of informed consent. * Definitive diagnosis of alopecia areata with a current episode of scalp hair loss lasting at least 6 months. * SALT score of 50 or more at both Screening and Baseline. Exclusion Criteria: * Treatment with systemic immunosuppressive medications or agents, including Janus kinase inhibitors, within 4 months prior to randomization. * Treatment with biologics within 6 months prior to Screening. * Positive test results for hepatitis B virus, hepatitis C virus, or human immunodeficiency virus at Screening. * History of active tuberculosis, a positive interferon gamma release assay at Screening, or evidence of tuberculosis-related lesions on chest radiography. * Clinically significant hematologic abnormalities, hepatic impairment, or renal impairment at Screening.