This is a single-center, randomized, double-blind, placebo-controlled, first-in-human study in which the safety, tolerability, and pharmacokinetics of orally administered AP303 will be assessed in healthy adult subjects.

The study will consist of 2 parts: Part A is a single ascending doses (SAD) phase enrolling a total of 4 cohorts of healthy subjects; Part B is a multiple ascending doses (MAD) phase enrolling 3 cohorts of healthy subjects. One cohort of Part A will receive AP303 under both fasted and fed conditions to investigate the effect of food.

Inclusion Criteria:

1. Healthy male and female subjects, 18 to 55 years of age, inclusive.
2. Body Mas index(BMI) between 18 to 32 kg/m2 inclusive.
3. Female subjects of child-bearing potential must have a negative pregnancy test result and agree to use highly effective contraception consisting of two forms of birth control
4. Subjects and their partners of childbearing potential must use two medically approved methods of contraception and the subjects should refrain from sperm/egg donation for the duration of the study and for 3 months after drug administration

Exclusion Criteria:

1. Pregnant (positive pregnancy test) or lactating women, and male subjects with partners who are or plan to be pregnant or lactating.
2. History or symptoms of any clinically significant gastrointestinal, renal, hepatic, broncho-pulmonary, neurological, psychiatric, cardio-vascular, endocrinological, ophthalmologic, hematological or allergic disease, metabolic disorder, cancer or cirrhosis.
3. People with a history of specific allergies, or allergic conditions or known allergies to any ingredient of the investigational medicinal product (IMP).
4. History of having received or currently receiving any systemic anti-neoplastic or immune-modulatory treatment ≤ 6 months prior to the first dose of study drug or the expectation that such treatment will be needed at any time during the study.
5. Positive test at screening of any of the following: Hepatitis B (HBsAg), Hepatitis C (HCVAb) or human immunodeficiency virus (HIV Ab).
6. Received an investigational drug within 30 days or 5 xT1/2 whichever is longer prior to the first dose of our study for small molecule; or within 90 days or 5 x T1/2 whichever is longer prior to the first dose of our study drug; or device study within 90 days prior to screening or more than 4 times per year.
7. History of drug and/or alcohol abuse or addiction.
8. Use of >5 cigarettes or equivalent nicotine-containing product per day.