Company decision of termination of the clinical program.

This is a phase 1, single-center, first-in-human study to assess the safety, pharmacokinetics and pharmacodynamics of DS-2741a after subcutaneous injection in healthy Japanese male volunteers and Japanese participants with moderate to severe atopic dermatitis.

This study consists of three parts. Part 1 and Part 3 are a single ascending and multiple dose study to assess the safety, pharmacokinetics and pharmacodynamics of DS-2741a after subcutaneous injection in healthy Japanese male participants. Part 2 is a single-dose study to assess the pharmacokinetics, safety, pharmacodynamics and efficacy of DS-2741a after subcutaneous injection in Japanese participants with moderate to severe atopic dermatitis.

Inclusion Criteria:

• For Part 1 and Part 3:

  • Japanese healthy male subjects.
  • Age ≥20 and ≤45 years upon providing informed consent.
  • Body mass index (BMI) ≥18.5 and <25.0 kg/m^2 at screening.

• For Part 2:

  • Japanese Male or female, Age ≥20 upon providing informed consent.
  • Diagnosed with chronic atopic dermatitis (AD) at least 3 years before screening and by the criteria of Hannifin and Rajka at screening.

Exclusion Criteria:

• For Part 1 and Part 3:

  • Having a history of atopic dermatitis
  • Having a history of hypersensitivity to drugs or other substances or being idiosyncratic
  • Having alcohol or drug dependence, etc.

• For Part 2:

  • Having an active dermatological disease other than AD, which, in the investigator's opinion, would affect study assessments.
  • Having a history of serious disease in the study potentially endangering the participant, as judged by the investigator or sub-investigator.
  • Having a chronic or acute infection requiring treatment within 28 days before screening.
  • Having superficial skin infections within 7 days before screening.
  • Having a history of recurrent oral herpes and recurrent genital herpes.
  • Having a history of parasitic infection or invasive, opportunistic infection such as histoplasmosis despite infection resolution, etc.

De-identified individual participant data (IPD) and applicable supporting clinical trial documents may be available upon request at https://vivli.org/. In cases where clinical trial data and supporting documents are provided pursuant to our company policies and procedures, Daiichi Sankyo will continue to protect the privacy of our clinical trial participants. Details on data sharing criteria and the procedure for requesting access can be found at this web address: https://vivli.org/ourmember/daiichi-sankyo/

Studies for which the medicine and indication have received European Union (EU) and United States (US), and/or Japan (JP) marketing approval on or after 01 January 2014 or by the US or EU or JP Health Authorities when regulatory submissions in all regions are not planned and after the primary study results have been accepted for publication.

Formal request from qualified scientific and medical researchers on IPD and clinical study documents from clinical trials supporting products submitted and licensed in the United States, the European Union and/or Japan from 01 January 2014 and beyond for the purpose of conducting legitimate research. This must be consistent with the principle of safeguarding study participants' privacy and consistent with provision of informed consent.

The participant, care provider, investigator, and outcomes assessor will be blinded in Part 1 and Part 3 of the study. Part 2 of the study will be unblinded.