This is a Phase 3, open-label study to evaluate the long-term safety of difamilast ointment 1% in subjects ≥2 years of age with mild to moderate AD. The study will also evaluate the long-term efficacy of difamilast ointment 1%, including durability of response.

Important Inclusion Criteria:

1. Subjects who are male or female ≥2 years of age at Screening (Visit 1).
2. Subjects who have a diagnosis of AD based on the American Academy of Dermatology AD diagnostic criteria
3. Subjects who have had a diagnosis of AD for at least 3 months prior to Screening .
4. Subjects who have an IGA of mild or moderate AD Severity and treatable body surface area (BSA) ≥3%at Baseline if not previously enrolled in study MEDI-MM36-301 OR b. IGA ≤ 3, with no minimum BSA and completed through Week 4/EOT Visit 6 of the study MEDI-MM36-301.
5. Subject is willing and able to comply with all study-related procedures, including, but not limited to, application of the study drug, and visit requirements.

Important Exclusion Criteria:

1. Subjects who have an AD flare (defined as rapid intensification of AD) within 28 days prior to Screening or Baseline (except for those previously enrolled in Study MEDI-MM36-301) or history of consistent requirement for high-potency topical corticosteroids to manage AD signs and symptoms.

2. Subjects who have an active or acute skin infection (eg, herpes simplex, herpes zoster, or chicken pox), and/or clinically infected AD

3. Subjects with significant systemic or localized infection

4. Subjects with minimal/mild depression and suicidal ideation

5. Subjects using restricted medications, biologics and alternative therapies, or using investigational drug

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