A Study of Intravenous MK-8226 in Participants With Moderate-to-Severe Atopic Dermatitis (MK-8226-003 AM2)

Part 1 of the study is a multiple rising dose assessment of the safety, tolerability, and
pharmacokinetics of MK-8226 for a period of 12 weeks followed by a 20-week off-treatment
follow-up period.

Part 2 of the study is an assessment of the safety, tolerability, and efficacy of MK-8226
for 12 weeks followed by a 20-week off-treatment follow-up period.

An interim futility analysis will be performed when approximately 40% of the participants
that have been treated with study drug have completed the active treatment portion of the
study (Week 12) while additional patients will continue to be enrolled into Part 2 of the
study. If the interim results support study continuation, additional participants may be
enrolled in Part 3 of the study.

In Part 3 of the study, participants will be treated with MK-8226 for a period of 12 weeks
followed by a 20-week off-treatment follow-up period to evaluate pharmacokinetic and
pharmacokinetic correlations to assist with modeling the dose range planned for further
studies.

Inclusion Criteria:

- Body weight >=40 kg

- Clinical diagnosis of atopic dermatitis for at least 6 months prior

- Candidate for systemic or phototherapy (i.e., failed topical treatment)

- Moderate-to-severe disease as defined by Body Surface Area (BSA) ≥10%, EASI ≥12, and
IGA ≥3

- No clinically significant abnormality on electrocardiogram

- No history of active or latent TB and no signs or symptoms suggestive of TB

- No history of active or latent TB and no signs or symptoms suggestive of TB

- History of inadequate response to a stable (≥ 1 month) regimen of topical
corticosteroids or calcineurin inhibitors within 3 months before the screening visit

Exclusion Criteria:

- Concurrent significant skin disease

- Any significant organ dysfunction within 6 months prior

- History of clinically significant heart disease

- History of neoplastic disease

- Positive for hepatitis B, hepatitis C, or human immunodeficiency virus (HIV)

- Infection requiring oral antibiotics within 2 weeks prior

- Receipt of a live virus vaccine within 4 weeks prior

- Inability to refrain from topical or systemic therapy during course of the study

- Had major surgery or donated or lost >=1 unit of blood within 4 weeks prior

- Participation in another study within 4 weeks prior

- Current or regular user of illicit drugs or a history of drug or alcohol abuse within
1 year prior

- Pregnant, breast-feeding, or anticipated to conceive during the course of the study