This is a randomized, open-label, parallel-group, phase 1 study to evaluate the PD effect of AP301 capsule in healthy volunteers. The study is planned to have 4 treatment arms: Arm 1: 2.10 g/day; arm 2: 4.20 g/day; arm 3: 6.30 g/day; arm 4: 8.40 g/day.

A total of 32 participants will participate in this study and the study consists of 3 periods such as screening period, hospitalization period and follow up period.

Important Inclusion Criteria:

• Healthy male volunteers, 18-55 years of age
• Body mass index (BMI) 18-30 kg/m2 (exclusive) at screening.

Important Exclusion Criteria:

• Serum phosphorus is below 1.00 mmol/L at screening.
• History of significant gastrointestinal disease or disorder, major gastrointestinal surgeries, or cholecystectomy
• History or symptoms of any clinically significant kidney, liver, broncho-pulmonary, gastrointestinal, neurological, psychiatric, cardiovascular, endocrine/metabolic, hematological diseases, or cancer.
• History of specific allergies or allergic conditions or known allergies to the study drug as judged by the investigator, or any confirmed significant allergic reactions (urticaria or anaphylaxis) to any drug, or multiple drug allergies (non-active hay fever is acceptable). Allowing for childhood asthma, history of mild eczema that has had no flare ups for ≥5 years or is fully resolved.
• Known history of allergy to common food like milk or gluten, or lactose intolerance, or special diet habit for religious/life-style reasons, which might potentially jeopardize the participant's compliance of study diet.
• Any clinically significant concomitant disease, or condition or treatment that could interfere with the conduct of the study.
• Confirmed (based on the average of 3 separate resting blood pressure measurements, after at least 5 minutes rest) systolic blood pressure (BP) greater than 150 or less than 90 mmHg, and diastolic BP greater than 90 or less than 50 mmHg at screening.
• Clinically relevant ECG abnormalities on screening ECG.
• Estimated glomerular filtration rate (eGFR) ≤ 70 mL/min/1.73 m2.
• Positive test at screening of any of the following: Hepatitis B (HBsAg), Hepatitis C (HCV Ab) or human immunodeficiency virus (HIV-1 or HIV-2 Ab).
• Alanine aminotransferase (ALT) or aspartate transaminase (AST) > 1.5 × upper limit of normal (ULN), or any other clinically significant abnormalities in laboratory test results at screening.
• Dosed with a small-molecule or biologic investigational drug within 30 days or 90 days, respectively, or 5 half-lives (whichever is the longer) prior to first dose of this study.
• Positive urine test for drugs of abuse and/or positive alcohol test at screening.
• Any medical or social conditions that, in the view of investigator, might potentially jeopardize the participant's compliance of study.

Male