This is a randomized, double-blind, vehicle-controlled study to evaluate the safety and efficacy of ALX-101 Gel 1.5% and 5% and a matching ALX-101 Gel Vehicle when applied topically twice daily for 42 days to adult and adolescent subjects with moderate atopic dermatitis.

The main objectives of this study are to:

• Evaluate the safety and tolerability of ALX-101 Gel 1.5% and 5% when applied topically in subjects with moderate atopic dermatitis compared with a matching ALX-101 Gel Vehicle
• Evaluate the dose-response relationship of ALX-101 Gel 1.5% and 5% when applied topically twice daily in subjects with moderate atopic dermatitis compared with a matching ALX-101 Gel Vehicle.

Inclusion Criteria:

In order to be eligible for the study, subjects must fulfill all of the following criteria:

1. Subject is at least 12 years of age

2. Subject has a clinical diagnosis of stable AD characterized by:

   1. Pruritus

   2. Eczema (acute, subacute, chronic)

      • Typical morphology and distribution with age-specific patterns
      • Chronic or relapsing history

3. Subject must have active AD covering 4-24% body surface area (BSA) (right and left treatment areas combined)

4. Bilateral treatment areas of AD must be 5 cm apart

5. Presence of AD with comparable bilateral target evaluation areas on (right and left sides of body) and within each bilateral treatment area:

   a. Bilateral target evaluation areas must each have active AD covering 0.5 -2% body surface area (BSA)

6. Bilateral target evaluation areas of AD must each have a Physician's Global Assessment score of 3 ("moderate") to be treated

7. Subject Visit 1 photographs are approved for enrollment by dermatology assessor

8. If the subject is a woman of childbearing potential, she has a negative urine pregnancy test and agrees to use an approved effective method of birth control for the duration of the study

9. Subject is non-pregnant and non-lactating

10. Subject is in good general health and free of any known disease state or physical condition which, in the investigator's opinion, might impair evaluation of the AD being treated or which exposes the subject to an unacceptable risk by study participation

11. Subject is willing and able to follow all study instructions and to attend all study visits

12. Subject is able to comprehend and willing to sign an Informed Consent Form (ICF)/Assent Form (AF)

13. Parent/guardian has the ability to understand, agree to and sign the study Informed Consent Form (ICF) prior to initiation of any protocol-related procedures as applicable; subject has the ability to give assent in the Assent Form (AF)

14. All female subjects of childbearing potential must use acceptable methods of contraception from the Screening Visit continuously until 14 days after stopping study drug.

Exclusion Criteria:

Any subject who meets one or more of the following criteria will not be included in this study:

1. Subject has spontaneously improving or rapidly deteriorating AD
2. Subject has clinically infected AD
3. Subject has any signs or symptoms associated with topical AD therapy (e.g., history of anaphylaxis, hypersensitivity reactions, skin atrophy, striae, pigmentary changes) which, in the investigator's opinion, might impair evaluation of the AD being treated or which exposes the subject to an unacceptable risk by study participation
4. Subject has used any systemic immunosuppressive or immunomodulatory therapy (e.g., etanercept, alefacept, infliximab) within 16 weeks prior to Visit 1
5. Subject has used any phototherapy (e.g., ultraviolet A, ultraviolet B) which, in the investigator's opinion, might affect AD within 4 weeks prior to Visit 1
6. Subject has used any systemic therapy (e.g., systemic corticosteroids [intranasal and inhaled corticosteroids are allowed]), prednisone cyclosporine, immunosuppressants/immunomodulators, Janus Kinase (JAK) inhibitors, methotrexate, cytostatics) within 4 weeks prior to Visit 1 which, in the investigator's opinion, might impair evaluation of the AD being treated or which exposes the subject to an unacceptable risk by study participation
7. Subject has used any systemic antibiotics within 2 weeks prior to Visit 1
8. Subject has used any topical AD therapy (e.g., corticosteroids, calcineurin inhibitors, topical H1 and H2 antihistamines, topical antimicrobials, and other medicated topical agents) on the planned treatment area(s) within one week prior to Visit 1
9. Subject has used emollients/moisturizers on the planned treatment area(s) within 4 hours prior to Visit 1
10. Subject is currently using H1 antihistamines (e.g., diphenhydramine, terfenadine) UNLESS a stable dose has been used for at least 14 days prior to Visit 1
11. Subject has a history of sensitivity to any of the ingredients in the study medications
12. Subject has any known concomitant dermatologic or medical condition which, in the investigator's opinion, might impair evaluation of the bilateral treatment and/or target evaluation areas of AD being treated or which exposes the subject to an unacceptable risk by study participation (e.g., psoriasis, lichen planus, lichen simplex chronicus,…)
13. Subject has participated in an investigational drug trial in which administration of an investigational study medication occurred within 30 days prior to Visit 1.