A Study to Learn How Well the Study Treatment Zabedosertib (BAY1834845) Works and How Safe it is Compared to Placebo in Adult Participants With Moderate-to-severe Atopic Dermatitis

Researchers are looking for a better way to treat atopic dermatitis (AD), an often long-lasting inflammation of the skin. Atopic dermatitis, also called eczema, is causing patches of skin to become swollen, red, cracked, and itchy.

The immune system helps protect the body from diseases. But sometimes the immune system can be too sensitive and overreact. This may then lead to allergies but also to skin conditions like atopic dermatitis.

The study treatment zabedosertib (BAY1834845) is currently under development for the treatment of atopic dermatitis and other inflammatory diseases. It works by reducing the activity of a protein called IRAK4. IRAK4 promotes the production and activation of a series of proteins that trigger inflammation reactions in the immune cells. By reducing the activity of IRAK4, the inflammation reactions are expected to be reduced.

The main purpose of the study is to learn how well zabedosertib works compared to placebo. A placebo is a treatment that looks like a medicine but does not have any medicine in it. How well it works means to find out the efficacy of zabedosertib. To answer this, the researchers will compare how many participants had 75% EASI score reduction after 12 weeks treatment between participants treated with zabedosertib and those treated with placebo. EASI represents Eczema Area and Severity Index (EASI). It is a tool for measuring the amount and severity of atopic dermatitis that a patient has on his or her body. The score ranges from 0-72, with 0 meaning clear skin and 72 meaning severe atopic dermatitis. In addition, the itch of the study participants and other tools for measuring the severity of atopic dermatitis will be assessed.

The secondary purpose of the study is to learn how safe it is compared to placebo. To know this, study team will compare how many participants having adverse events after taking study treatment between participants treated with zabedosertib and those treated with placebo.

In the study, participants will be randomly (by chance) assigned to receive zabedosertib or placebo. The participants from both treatment groups will take zabedosertib or placebo for up to 12 weeks.

The study consists of an up to 28-day screening period (Visits 1 and 2), a 12-week treatment period consisting of 5 visits (Visits 3 to 7), and a 4-week follow-up visits (Visits 8). Thus, the total study duration per participant will be 17 to 20 weeks (approximately 140 days).

During the study, the study team will:

* take blood and urine samples
* take skin samples (not obligatory for all patients)
* check the participants' disease area for assessment
* provide participants device to record their disease status and to take pictures on their disease areas
* have participants complete self-reported questionnaires
* do physical examinations
* examine heart health using ECG
* check vital signs
* ask the participants questions about how they are feeling and what events they are having.

An adverse event is any problem that a participant has during a study. Doctors keep track of all adverse events that happen in studies, even if they do not think the adverse events might be related to the study treatments.

At 28 days after the participants take their last treatment, the study team will check if participants have any events that might be related to the study treatment. This will be the last visit for the study.


Eligibility Criteria:
Inclusion Criteria:

* 18 to 65 years of age inclusive, at the time of signing the informed consent.
* Diagnosis of atopic dermatitis (AD) for ≥ 1 year at the screening visit.
* Moderate-to-severe AD at randomization visit as defined by

  * Eczema Area and Severity Index (EASI) score ≥ 16,
  * Body surface area (BSA) affected by AD ≥ 10%,
  * Validated Investigator Global Assessment for Atopic Dermatitis (vIGA-AD) score ≥ 3, and
  * Peak Pruritus 0-10 numerical rating scale (NRS) ≥ 4 (average score of the daily scores of the 7 days before randomization, with ≥ 4 scores required).
* Documented history (within 6 months prior to the first screening visit) of inadequate response to treatment with topical corticosteroids (TCS), or if TCS are medically not advisable (e.g., due to important side effects or safety risks).
* Stable amount of emollient applied to skin over the whole body twice daily for at least the 7 consecutive days before the randomization visit
* Body mass index (BMI) within the range of 18.5 to 35.0 kg/m\^2 (inclusive) at screening (Visit 1) and randomization visits.
* Women of childbearing potential and male subjects able to father children must agree to use adequate contraception when sexually active.

Exclusion Criteria:

* History of any major surgery within 8 weeks prior to screening or scheduled (elective) surgery, planned hospitalization and/or planned dental treatment during the study that could constitute a risk when participating in a study.
* Severe invasive infections in medical history and/or active clinically significant viral, bacterial, fungal, or parasitic infection (systemic or severe skin infection) ≤ 3 months prior to the randomization visit.
* A presence of uncontrolled condition including cardiovascular, respiratory, hepatic renal, gastrointestinal, endocrine, hematological, neurological, or neuropsychiatric disorders or any other unstable illness that, in the opinion of the investigator, could constitute a risk when taking investigational product, study conduct or could interfere with the interpretation of data.
* Known immunodeficiency disorder or immunocompromised state or, in the opinion of the investigator, unacceptable risk for participating in the study.
* Use of topical treatments for AD within 7 days before the randomization visit.
* Systemic immunosuppressive/ immunomodulating therapy or phototherapy within 4 weeks before the randomization visit.
* Therapy with biologic drugs within 5 half-lives of the biologic drug
* Known hypersensitivity to the study drug