A Study to Evaluate the Safety and Effectiveness of Upadacitinib in Pediatric Participants With Alopecia Areata

Alopecia areata (AA) is a disease that happens when the immune system attacks hair follicles and causes hair loss. AA usually affects the scalp and face, but hair loss can happen on any hair-bearing part of the body. Some treatment options are available for adults and adolescents with AA, however there is still high unmet need for systemic treatments (treatment that moves throughout the bloodstream) approved for young patients with AA. Treatments may not work for all patients or may stop working over time. Because of this, researchers are developing new AA treatments, like upadacitinib. Upadacitinib is a type of medicine called a Janus- Kinase (JAK) inhibitor and works with the body to fight the inflammation that can cause AA. In this study, different doses (amounts) of upadacitinib are being compared to treatment with placebo (looks like the study treatment but contains no medicine). Upadacitinib is an investigational JAK inhibitor being developed for the treatment of severe alopecia areata in pediatric patients. This is a randomized, double-blind, placebo-controlled study. Participants are placed in 3 groups, called treatment arms. Each group receives a different treatment. There is a 1 in 5 chance that participants will be assigned to placebo. Pediatric participants with a diagnosis of severe alopecia areata with SALT score ≥ 50 scalp hair loss will be enrolled. Participants will be at least 6 years old at Screening and less than 18 years old at Baseline. Approximately 300 participants will be enrolled in the study at approximately 120 sites worldwide. Participants will receive oral doses of upadacitinib or matching placebo daily, or twice daily, for approximately 160 weeks. The study comprises a 35-day Screening Period, a 24-week placebo-controlled double-blinded treatment period (Period A), a 28-week blinded extension treatment period (Period B), a 108-week blinded long-term extension period (Period C), and a 30-day follow-up period. There may be higher treatment burden for participants in this trial compared to their standard of care. Participants will attend regular visits during the study at a hospital or clinic. The effect of the treatment will be checked by medical assessments, blood tests, checking for side effects and completing questionnaires.

Inclusion Criteria: * Participants must have a diagnosis of severe alopecia areata with SALT score \>= 50 scalp hair loss at Screening and Baseline * No spontaneous scalp hair regrowth over the past 6 months * Participants will have current episode of alopecia areata of less than 8 years Exclusion Criteria: * Participants must not have a current diagnosis of primarily diffuse type of alopecia areata * Participants must not have a diagnosis of other types of alopecia that would interfere with evaluation of alopecia areata, including but not limited to female pattern hair loss, male pattern hair loss (androgenetic alopecia) Stage III or greater, traction alopecia, lichen planopilaris, discoid lupus, frontal fibrosing alopecia, central centrifugal cicatricial alopecia, folliculitis decalvans, trichotillomania, and telogen effluvium * Participants must not have a diagnosis of other types of inflammatory scalp, eyebrow, or eyelash disorders that would interfere with evaluation of alopecia areata, including but not limited to seborrheic dermatitis, scalp psoriasis, AD, and tinea capitis