A Study Investigating the Effect of EDP1815 in the Treatment of Mild, Moderate and Severe Atopic Dermatitis

The purpose of this research study is to determine whether the study drug, EDP1815, is safe and effective in the treatment of atopic dermatitis compared with placebo. The study will look at different doses of the study drug, and whether there are differences when the drug is given once daily or twice daily.

Atopic dermatitis (atopic eczema) is a very common type of skin disease. It typically causes red, dry, and itchy skin and may have a significant impact on quality of life. Rashes may appear on the arms and behind the knees, or anywhere else on the body. While there are existing therapies, there is currently no cure for atopic dermatitis.

This is a randomized, double blind, placebo controlled, parallel group, Phase 2 study to evaluate the efficacy and safety of EDP1815 in adult participants 18 to ≤75 years of age with mild, moderate, and severe atopic dermatitis (AD).

Participants will be screened within 28 days prior to the first dose of study intervention to confirm study eligibility. Subjects must have mild, moderate, or severe AD involving at least 5% Body Surface Area (BSA); an Investigator Global Assessment (IGA) score of 2, 3, or 4; and an Eczema Area Severity Index (EASI) of at least 6 at screening and Day 1.

All participants must agree to use a background therapy (per protocol) twice daily for at least 14 days prior to Day 1 in order to be considered eligible for the study.

Approximately 405 participants will be randomized to receive either EDP1815 or placebo (295 to EDP1815: 110 to placebo) and treated for 16 weeks. Participants in Cohorts 1, 2, \& 3 will be randomized in a 3:1 ratio (225 to EDP1815: 75 to placebo). Participants in Cohort 4 will be randomized in a 2:1 ratio (70 to EDP1815: 35 to placebo). Cohorts 1, 2 \& 3 will be run concurrently, and Cohort 4 recruitment will commence after enrollment for Cohorts 1, 2, \& 3 are completed.

Randomization will be stratified by baseline disease severity (mild \[IGA = 2\], moderate \[IGA = 3\] or severe \[IGA = 4\] AD). The investigational product will be administered either once or twice daily for 16 weeks. Background emollient (moisturizer) therapy must continue at least twice daily for the duration of the treatment and follow-up periods. Topical rescue therapy is allowed during the treatment period per protocol.

The primary efficacy endpoint is achievement of an EASI-50 response at Week 16. Secondary efficacy endpoints will look at EASI, IGA, BSA, SCORAD, DLQI, Pruritus-NRS, Sleep Disturbance-NRS, POEM, and the need for rescue therapy at Weeks 4, 8, 12 and 16 (unless otherwise specified in the protocol). Safety and efficacy assessments will be conducted at the investigator site by a clinical assessor blinded to treatment assignment. Scheduled clinic study visits for all subjects will occur at Screening, Day 1, Week 2, Week 4, Week 8, Week 12, Week 16 (end of treatment) and Week 20 (post-treatment follow-up). Participants discontinuing early from the study will undergo a 28-day follow-up period, where possible.

At the end of the 16-week study treatment, qualified participants completing the study will have the option to enter an open label study.

Eligibility Criteria:
Inclusion Criteria:

* Provide written informed consent.
* Must meet age criteria.
* Must have a diagnosis of atopic dermatitis (AD)for at least 6 months.
* Must have severity of atopic dermatitis meeting the below criteria at both Screening and Day 1:

  * An IGA of 2, 3 or 4 on the vIGA scale, and;
  * A BSA of ≥5%, and;
  * An EASI score of ≥6.
* Must agree to use emollients.
* Must meet contraception requirements.

Exclusion Criteria:

* Have been in a clinical trial for EDP1815 prior to signing of ICF.
* Use of phototherapy or tanning beds; systemic medications/treatments that could affect AD or its symptoms including immunosuppressive therapy (e.g., oral or injectable corticosteroids, methotrexate, azathioprine, cyclosporine, mycophenolate mofetil, JAK inhibitors, tacrolimus, and/or leukotriene inhibitor) within 4 weeks of randomization.
* Treatment with topical agents that could affect atopic dermatitis, including topical corticosteroids, topical calcineurin inhibitors (e.g., tacrolimus or pimecrolimus), or topical PDE-4 inhibitor (e.g., crisaborole) within 14 days prior to randomization.
* Clinically significant abnormalities in screening laboratory values that in the opinion of the Investigator would make a participant unsuitable for inclusion in the study. One retest is permitted within the 28-day screening window.
* Hypersensitivity to P histicola or to any of the excipients.
* Unwillingness to comply with study procedures, including follow-up, as specified by this protocol, or unwillingness to cooperate fully with the Investigator.
* Have any other conditions, which, in the opinion of the Investigator or Sponsor, would make the participant unsuitable for inclusion or could interfere with the participant participating in or completing the study.