Phase 2a Study of the Safety, Tolerability, and Pharmacokinetics of Topically Administered PRN473 (SAR444727) in Patients With Mild to Moderate Atopic Dermatitis

Inclusion Criteria:

- Male and female adults 18 to 70 years of age (inclusive) at the time of informed
consent.

- Diagnosed with mild to moderate AD.

- History of AD for at least 6 months as determined by the Investigator through patient
interview.

- Stable disease for the 4 weeks prior to the screening visit with no significant flares
in AD as determined by the Investigator.

- Validated Investigator Global Assessment-atopic dermatitis (vIGA-AD) score of Moderate
or Mild at Screening. The vIGA-AD is evaluated for the entire body except scalp,
palms, soles and genitals.

- Has AD involvement (excluding scalp, palms, soles and genitals) of at least 1.0% BSA
and no more than 14.0% BSA.

- Has at least two target lesions 100 cm2 or greater with a difference no greater than 1
point in lesion TSS and at least 5 cm apart located on the trunk (excluding genitals)
or upper extremities (excluding palms).

- If female, patients with child-bearing potential must have a negative pregnancy test,
and agree to practice true abstinence or agree to use highly effective contraception.

- If male, agree to use a male condom and highly effective contraception with female
partners of child-bearing potential.

- In good health as judged by the Investigator.

Exclusion Criteria:

- Patients who have failed 2 or more prior systemic treatments for AD.

- Patients who have received a live or attenuated vaccine in the last 12 weeks or intend
to receive a live or attenuated vaccine during the study.

- Patients who cannot discontinue prohibited medications and treatments prior to the
Baseline visit and during the study.

- Has unstable AD, based on the judgement of the Investigator, or any consistent
requirement for high potency topical steroids to manage AD signs or symptoms.

- Patients who have significant active systemic or localized bacterial, viral, fungal,
and helminth infection in the last 30 days.

- Patients unwilling to refrain from prolonged sun exposure or use of a tanning bed or
other artificial light emitting devices for 4 weeks prior to Baseline and during the
study.

- Patients with other skin conditions that would interfere with evaluations of the
effect of the study medication on AD, as determined by the Investigator.

- Patients with known genetic dermatological conditions that overlap with AD, such as
Netherton syndrome.

- Previous use of a BTK inhibitor.

- Women who are pregnant, wishing to become pregnant during the study, or are
breastfeeding.

- Patients currently undergoing allergy (eg, food allergy testing or skin prick
testing), patch testing, or food challenges, or plan to do so during the study.

- Patients who have undergone major surgery within 4 weeks prior to Day 1 or patients
who have a major surgery planned during the study.

- Regular use of drugs of abuse or regular alcohol consumption within 6 months prior to
the study.