Randomized, double-blind and placebo-controlled study to assess the safety, tolerability and pharmacokinetics of single ascending doses of SYH2085 and its food effect in China healthy adult participants. The study is composed of 2 parts. Part 1 is to assess the safety, tolerability and pharmacokinetics of a single ascending dose of SYH2085 tablet. Part 2 is to assess the food effect on SYH2085 at a selected dose in a cross-over design.

Inclusion Criteria:

1. Age of 18 - 45 years (inclusive), male or female; BMI: 19.0-28.0 kg/m^2 (inclusive), with a minimum weight of 50.0 kg (inclusive) for male and 45.0 kg (inclusive) for female;
2. Normal vital signs; Normal physical examination; Normal ECG findings; Normal laboratory examination; Normal imaging examination (X-ray);
3. Participants and their partners agree to use effective and reliable contraceptive methods to avoid pregnancy, and male subjects had no plans to donate sperm, and female subjects had no plans to donate eggs, from the time they signed the informed consent to 3 months after the end of the study;
4. Participants must give informed consent before the trial, fully understand the content, procedures and possible adverse reactions, and voluntarily sign a written informed consent.

Exclusion Criteria:

1. History of hypersensitivity or allergy to drug or food, or any component of the study drug；
2. Participants with a history of serious diseases, including pancreas, cardiovascular, liver, kidney, blood and lymphatic, central nervous system, and gastrointestinal systems, or other important diseases that may affect the absorption, metabolism, or excretion of the study drug;
3. History of gastrointestinal surgery or resection that may alter the absorption and/or elimination of orally administered drugs (except for appendectomy);
4. Participants who have undergone any surgical procedure within 6 months prior to the trial;
5. Participants with a history of respiratory or systemic acute infection within 2 weeks prior to screening;
6. Participants who have experienced blood loss exceeding 400 mL (e.g., due to blood donation or other reasons) within 3 months prior to the trial;
7. Participants who have participated in another investigational drug study within 3 months prior to the planned administration of the study drug, where the last dose was received less than 3 months before screening for this trial; or subjects who plan to participate in another drug trial during the course of this study;
8. Participants who have been vaccinated within 28 days prior to screening or plan to receive vaccination during the trial period;
9. Participants who have taken any prescription drugs, over-the-counter (OTC) medications, Chinese patent medicines, herbal medicines, health supplements, or oral supplements (e.g., calcium, iron, magnesium, selenium, zinc, etc.) within 28 days prior to screening or during the trial period;
10. Participants who have used oral long-acting contraceptives or implanted long-acting contraceptives within 28 days prior to screening;
11. Participants who have used any known inducers or inhibitors of hepatic enzymes (e.g., grapefruit, orange juice, etc.) within 28 days prior to screening or during the trial period;
12. Participants with any electrocardiogram (ECG) abnormality considered clinically significant by the investigator, including but not limited to: QTcF interval ≥450 ms, or a history of QTcF interval prolongation; PR interval ≥210 ms; QRS duration ≥120 ms; or a history of arrhythmia, syncope related to arrhythmia, use of a cardiac pacemaker, or other cardiac-related conditions. Note: Conditions include but are not limited to: heart failure; hypokalemia; atrial fibrillation, atrial flutter, premature atrial contractions, premature ventricular contractions, non-sustained or sustained ventricular tachycardia; bradycardia or sick sinus syndrome; personal or family history of any cardiac conduction abnormalities; personal or family history of Long QT Syndrome (LQTS); or family history of sudden death;
13. Participants with one or more abnormal vital signs at screening: aural temperature >37.5°C, pulse rate >100 beats per minute, systolic blood pressure ≥140 mmHg or <90 mmHg, diastolic blood pressure ≥90 mmHg or <50 mmHg;
14. Participants who smoked an average of more than 5 cigarettes per day within 3 months prior to screening, or who are unable to discontinue the use of any tobacco products during the trial period；
15. Participants who habitually consumed excessive amounts of xanthine- or caffeine-containing foods, beverages, or other items that may affect drug absorption, distribution, metabolism, or excretion within 1 month prior to screening and are unwilling to abstain during the trial. Examples include: coffee (>1100 mL daily), tea (>2200 mL daily), cola (>2200 mL daily), energy drinks (>1100 mL daily), chocolate (>510 g daily);
16. Participants with alcohol abuse: alcohol consumption exceeding 14 units per week within 1 month prior to signing the informed consent form (1 unit = 285 mL of beer, 25 mL of spirits, or 150 mL of wine)；
17. Participants with a positive alcohol breath test (>0 mg/100 mL) or those unable to abstain from alcohol during the trial period;
18. Participants with a positive result for any of the following: Hepatitis B virus surface antigen (HBsAg), anti-Hepatitis C virus antibody (Anti-HCV), Treponema pallidum specific antibody, or anti-Human Immunodeficiency Virus antibody (Anti-HIV);
19. Participants with a history of drug abuse and/or use of illicit drugs within 3 months prior to screening;
20. Participants with a positive urine drug screen;
21. Participants with a history of needle phobia, blood phobia, or intolerance to venipuncture for blood sampling;
22. Participants who are pregnant, breastfeeding, or have a positive β-HCG pregnancy test;
23. Participants with specific dietary requirements who cannot comply with the standardized diet and schedule;
24. Participants deemed unsuitable for participation in this study by the investigator for any other reason.