JAK1 Inhibitor With Medicated Topical Therapy in Adolescents With Atopic Dermatitis

This is a randomized, double blind, placebo controlled, parallel group, Phase 3 study to evaluate the efficacy and safety of PF 04965842 in adolescent participants 12 to \<18 years of age with moderate to severe AD.

This is a randomized, double blind, placebo controlled, parallel group, Phase 3 study to evaluate the efficacy and safety of PF 04965842 in adolescent participants 12 to \<18 years of age with moderate to severe AD. Participants will be screened within 28 days prior to the first dose of study intervention to confirm study eligibility. Subjects must have moderate-severe AD involving at least 10% Body Surface Area (BSA); an Investigator Global Assessment (IGA) score of at least 3; an Eczema Area Severity Index (EASI) of at least 16 and Peak Pruritus Numerical Rating Score (NRS) of at least 4 on baseline/Day 1. Eligible subjects will be randomized at the Baseline/Day 1 visit. Approximately 225 participants will be randomized in a 1:1:1 ratio to receive once daily PF 04965842 at 200 mg, 100 mg, or placebo for 12 weeks. Randomization will be stratified by baseline disease severity (moderate \[IGA = 3\] vs. severe \[IGA = 4\] AD). The investigational products will be administered QD for 12 weeks. Background therapy (medicated and non-medicated topical therapy) must be applied BID for the duration of the treatment period. The co-primary efficacy endpoints are an IGA score of clear (0) or almost clear (1) with a reduction from baseline of greater than 2 points at Week 12 AND an at least 75% improvement of the EASI score (EASI-75) at week 12. Safety and efficacy assessments will be conducted at the investigator site by a clinical assessor blinded to treatment assignment. Scheduled clinic or telephone study visits for all subjects will occur at Screening, Baseline/Day 1, Day 8 (by phone), Day 15, Day 29, Day 43 (by phone), Day 57, Day 85 (End of treatment/Early termination), Day 113 (End of Study). Participants discontinuing early from the study will undergo a 4 week follow up period.

This study includes an immunogenicity sub study integrated into the last 4 weeks of the main study treatment period. At Week 8, up to approximately 90 participants (up to approximately 30 in each treatment arm) who have completed 8 weeks of treatment with study intervention will receive a tetanus, diphtheria and acellular pertussis combination vaccine (Tdap), and collection of blood samples for the evaluation of immunogenicity at Weeks 8 and 12. Participants of this sub study will complete all other protocol specified procedures in the main study.

At the end of the 12 week study treatment, qualified participants completing the study will have the option to enter the long term extension (LTE) study B7451015.

Eligibility Criteria:
Inclusion Criteria:

* Aged between 12 and to 17 with a minimum body weight of 40 kg
* Diagnosis of atopic dermatitis (AD) for at least 1 year and current status of moderate to severe disease (\>= the following scores: BSA 10%, IGA 3, EASI 16, Pruritus NRS severity 4)

Exclusion Criteria:

* Acute or chronic medical or laboratory abnormality that may increase the risk associated with study participation
* Unwilling to discontinue current AD medications prior to the study or require treatment with prohibited medications during the study
* Prior treatment with JAK inhibitors
* Other active non-AD inflammatory skin diseases or conditions affecting skin
* Medical history including thrombocytopenia, coagulopathy or platelet dysfunction, malignancies, current or history of certain infections, lymphoproliferative disorders and other medical conditions at the discretion of the investigator
* Pregnant or breastfeeding women, or women of childbearing potential who are unwilling to use contraception