Inclusion Criteria:

   - Body weight of ≥ 40 kg at Baseline Visit for participants between ≥ 12 and < 18 years
   of age

   - Chronic atopic dermatitis (AD) with onset of symptoms at least 3 years before Baseline
   Visit and subject meets Hanifin and Rajka criteria.

   - Active moderate to severe AD defined by:

      - Eczema Area and Severity Index (EASI) score ≥ 16 at the Screening and Baseline
      Visits;

      - Validated Investigator's Global Assessment (vIGA) score ≥ 3 at the Screening and
      Baseline Visits;

      - ≥ 10% Body surface area (BSA) of AD involvement at the Screening and Baseline
      Visits;

      - Baseline weekly average of daily Worst Pruritus NRS ≥ 4.

   - Candidate for systemic therapy or have recently required systemic therapy for AD

   - Subject has applied a topical emollient (moisturizer) twice daily for at least 7 days
   before the Baseline Visit.

   - Documented history of inadequate response to topical corticosteroids (TCS) or topical
   calcineurin inhibitor (TCI) or documented systemic treatment for AD within 6 months
   before Baseline Visit

Exclusion Criteria:

   - Prior exposure to any Janus kinase (JAK) inhibitor

   - Unable or unwilling to discontinue current atopic dermatitis treatments prior to the
   study

   - Requirement of prohibited medications during the study

   - Other active skin diseases or skin infections requiring systemic treatment or would
   interfere with appropriate assessment of atopic dermatitis lesions

   - Female subject who is pregnant, breastfeeding, or considering pregnancy during the
   study