Inclusion Criteria:  Participant has a body mass index (BMI) range of 18.5 to 32.0 kg/m^2, inclusive and weighs at least 50 kg at screening.  Female participant is not pregnant and at least 1 of the following conditions apply:  Not a woman of childbearing potential (WOCBP) WOCBP who agrees to follow the contraceptive guidance from the time of informed consent through at least 30 days after final IP administration. Female participant must agree not to breastfeed starting at 90 days prior to screening and throughout the study period and for 30 days after final investigational product (IP) administration. Female participant must not donate ova starting at first dose of IP and throughout the study period and for 30 days after final IP administration. Male participant with female partner(s) of childbearing potential (including breastfeeding partner[s]) must agree to use contraception throughout the treatment period and for 90 days after final IP administration. Male participant must not donate sperm during the treatment period and for 90 days after final IP administration. Male participant with pregnant partner(s) must agree to remain abstinent or use a condom for the duration of the pregnancy throughout the study period and for 30 days after final IP administration. Participant agrees not to participate in another interventional study while receiving study treatment in the present study.  Exclusion Criteria:  Participant has received any investigational therapy within 28 days or 5 half lives, whichever is longer, prior to screening. Participant has any condition which makes the participant unsuitable for study participation. Participant has a known or suspected hypersensitivity to ASP8731 or any components of the formulation used. Female participant who has been pregnant within 6 months prior to screening or breastfeeding within 90 days prior to screening. Participant has had previous exposure with ASP8731. Participant has any of the liver function tests (alkaline phosphatase, alanine aminotransferase, aspartate aminotransferase and total bilirubin) above the upper limit of normal (ULN) on day -1. In such a case, the assessment may be repeated once. Participant has creatinine level outside normal limits on day -1. In such a case, the assessment may be repeated once. Participant has any clinically significant history of allergic conditions (including drug allergies, asthma, eczema or anaphylactic reactions, but excluding untreated, asymptomatic, seasonal allergies) prior to first IP administration. Participant has any history or evidence of any clinically significant cardiovascular, gastrointestinal, endocrinologic, hematologic (e.g., sickle cell disease, hemoglobinopathies, hemolytic anemias, etc.), hepatic, immunologic, metabolic, urologic, pulmonary, neurologic, dermatologic, psychiatric, renal and/or other major disease or malignancy. Participant has/had febrile illness or symptomatic, viral, bacterial (including upper respiratory infection) or fungal (noncutaneous) infection within 1 week prior to day -1. Participant has any clinically significant abnormality of the physical examination, ECG and protocol-defined clinical laboratory tests at screening or on day -1. Participant has a mean pulse < 45 or > 90 bpm; mean systolic blood pressure > 140 mmHg; mean diastolic blood pressure > 90 mmHg (measurements taken in triplicate after participant has been resting in the supine position for at least 5 minutes; pulse will be measured automatically) on day -1. If the mean blood pressure or pulse exceeds the limits above, 1 additional triplicate may be taken. Participant has a mean QT corrected for heart rate by Fridericia's cube root formula (QTcF) of > 430 msec (for male participants) and > 450 msec (for female participants) on day -1. If the mean QTcF exceeds the limits above, 1 additional triplicate ECG may be taken. Participant has used any prescribed or nonprescribed drugs (including vitamins, natural and herbal remedies, e.g., St. John's Wort) in the 2 weeks prior to first IP administration, except for occasional use of acetaminophen (up to 2 g/day), topical dermatological products (including corticosteroid products), hormonal contraceptives and hormone replacement therapy (HRT). Participant has smoked, used tobacco-containing products or nicotine containing products (e.g., electronic vapes) within 6 months prior to screening or the participant tests positive for cotinine at screening or on day -1. Participant has a history of consuming > 14 units for male participants or > 7 units for female participants of alcoholic beverages per week within 6 months prior to screening or has a history of alcoholism or drug/chemical/substance abuse within 2 years prior to screening (note: 1 unit = 12 ounces of beer, 4 ounces of wine, 1 ounce of spirits/hard liquor) or the participant tests positive for alcohol at screening or on day -1. Participant has used any drugs of abuse (amphetamines, barbiturates, benzodiazepines, cannabinoids, cocaine and/or opiates) within 3 months prior to day -1 or the participant tests positive for drugs of abuse (amphetamines, barbiturates, benzodiazepines, cannabinoids, cocaine and opiates) at screening or on day -1. Participant has consumed more than 400 mg of caffeine (4 cups of coffee) per day in the 48 hours prior to first IP administration on day 1 and/or is unwilling to abstain from coffee (or caffeine-containing product) consumption through discharge from unit. Participant has used any inducer of metabolism (e.g., barbiturates and rifampin) in the 3 months prior to day -1. Participant has had significant blood loss, donated ≥ 1 unit (450 mL) of whole blood or donated plasma within 7 days prior to day -1 and/or received a transfusion of any blood or blood product within 60 days. Participant has a positive serology test for hepatitis A virus (HAV) antibodies (IgM), hepatitis B core (HBc) antibodies, hepatitis B surface antigen (HBsAg), hepatitis C virus (HCV) antibodies or antibodies to human immunodeficiency virus (HIV) type 1 and/or type 2 at screening. Participant has received a coronavirus disease 2019 (COVID-19) vaccine within the 2 weeks prior to first IP administration or will have a COVID-19 vaccine dose before the end-of-study visit (ESV). Participant has a positive result for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) polymerase chain reaction (PCR) test at screening or on day 1. Participant is an employee of Astellas, the study-related contract research organizations (CROs) or the clinical unit.