To evaluate the safety of single and repeated administration of TAS3731.

Key Inclusion Criteria:

1. Healthy adult male subjects who provided written informed consent to participate in the study
2. Aged 18 years or older and younger than 40 years at the time of informed consent
3. Body weight of 50 kg or more at screening:
4. Body mass index of 18.5 or more and less than 25.0 (Japanese) or less than 30.0 kg/m2 (Caucasian)
5. Capable of oral intake.

Key Exclusion Criteria

1. Complications or history of diseases that may affect absorption, distribution, metabolism, or excretion of the investigational drug, such as hepatic/biliary tract disease, renal/urologic disease, or gastrointestinal disease. The stomach or small intestine has been resected.

2. The 12-lead electrocardiogram at the time of the screening test was judged by the investigator to be inadequate for this study.

3. Had any concurrent disease (including symptoms and signs; however, diseases that do not affect evaluations in the study such as asymptomatic pollinosis and wart are excluded)

4. The patient has the following complications or a history of the following.

   1. Had current or previous drug abuse (including use of illicit drugs) or alcoholism
   2. Had current or previous hypersensitivity or allergy to drugs

5. Suspected COVID-19 disease.

Data will not be shared according to the Sponsor policy on data sharing. Taiho policy on data sharing may be found at https://www.taiho.co.jp/en/science/policy/clinical\_trial\_information\_disclosure\_policy/index.html.