The purpose of this first-in-human (FIH) study is to assess the safety and tolerability, pharmacokinetics (PK), immunogenicity (IG) and pharmacodynamics (PD) of DCY636. The results are intended to support the further clinical development of DCY636 in future studies.

This is a two-part FIH, randomized, placebo-controlled, participant- and investigator-blinded study in healthy participants (Part 1) and participants with moderate to severe AD (Part 2).

Key Inclusion Criteria:

Healthy Participants (Part 1)

• Healthy male and non-childbearing potential female participants 18 to 55 years of age inclusive.

Participants with moderate to severe atopic dermatitis (Part 2)

• Males and non-pregnant females age 18 years or older

• Diagnosis of atopic dermatitis for at least 1 year not adequately controlled by topicals

• Moderate to severe atopic dermatitis as defined by all of the following:

  • EASI score ≥12 at screening visit and ≥16 at baseline (BL) visit
  • IGA score ≥3 at screening visit and baseline visit
  • Total Body surface area (BSA) affected by AD ≥ 10 % at screening visit and baseline visit
  • Peak Pruritus NRS score ≥4 at baseline visit, based on weekly average of daily assessment in the week prior to baseline visit

Key Exclusion Criteria:

All Participants (Part 1, Part 2)

• Use of other investigational drugs within the last 30 days or 5 half-lives of the other drugs prior to initial dosing, whichever is longer.
• Meet any of the prohibited medication use criteria at baseline visit.
• A positive syphilis test result during screening period.
• Evidence of active or latent TB infection, as determined by T-Spot test during screening period.
• History of immunodeficiency diseases, or a positive human immunodeficiency virus (HIV) test result.
• Recent (within last half year) or ongoing helminth infection.
• History of hepatitis B or hepatitis C or serologic evidence for viral hepatitis. A positive Hepatitis B virus surface antigen (HBsAg), Hepatitis B virus core antibody (HBcAb) and/or Hepatitis B surface antibody (HBsAb) test during screening period excludes a participant. A positive test for HBsAb can be included if the test for HBsAg and HBcAb are negative and the history of hepatitis B vaccination is known. Participants with a positive Hepatitis C virus (HCV) antibody test should be excluded.

Healthy Participants (Part 1)

• Women of childbearing potential
• Smokers Participants with moderate to severe atopic dermatitis (Part 2)
• Regular use (more than 2 visits per week) of a tanning booth/parlor or extended sun exposure (per investigator judgement) within 4 weeks prior to baseline visit
• Have any chronic, uncontrolled medical condition, which would put the participant at increased risk during study participation, such as uncontrolled: diabetes, hypertension, morbid obesity, thyroid, adrenal, cardiovascular, pulmonary, hepatic, renal, neurologic or psychiatric disease, or other disease of concern, as per investigator judgment
• Women of childbearing potential (WOCBP) are excluded unless they are using highly effective methods of contraception (failure rate < 1% per year) while taking study treatment and for 202 days (= 5 times the terminal half-life) of study treatment after stopping study treatment.

Other protocol-defined inclusion/exclusion criteria may apply.