This is a Phase I, single-center trial to assess the safety, tolerability, PK and food effect of KR23343 in healthy volunteers. The study will be conducted in 3 sequential stages:

Stage 1: Single-Ascending-Dose (SAD) study A randomized, double-blind, placebo-controlled, dose-escalation study to assess the safety, tolerability, and PK of single ascending doses of KR23343.

Stage 2: Food-Effect (FE) study An open-label, randomized, two-period, two-sequence crossover study to evaluate the effect of food on the PK of a single dose of KR23343.

Stage 3: Multiple-Ascending-Dose (MAD) study A randomized, double-blind, placebo-controlled, dose-escalation study to investigate the safety, tolerability, and PK of repeated once-daily administration of KR23343 for 10 days.

This first-in-human study will investigate the safety, tolerability, and pharmacokinetics (PK) of KR23343 following single and multiple ascending oral doses in healthy subjects, as well as assess the effect of food on the PK of KR23343. The results of this study will be used to select doses for subsequent studies in patients.

Primary objectives:

Stage 1: To assess the safety and tolerability of single ascending oral doses of KR23343 in healthy participants. Stage 3: To assess the safety and tolerability of multiple ascending oral doses of KR23343 in healthy participants.

Secondary objectives:

Stage 1: To assess the PK profile of KR23343 following single oral doses in healthy participants and evaluate the effect of KR23343 tablets on the corrected QT interval (QTcF) and other electrocardiogram (ECG) parameters. Stage 2: To assess the PK profile, safety and tolerability of a single dose of KR23343 following high-fat food intake relative to fasting conditions in healthy participants. Stage 3: To assess the PK profile of KR23343 after repeated oral doses in healthy participants.

Inclusion Criteria:

1. Healthy male or female participants aged 18 to 45 years, inclusive.
2. Body mass index (BMI) between 19 and 28 kg/m² (inclusive) and body weight ≥ 50 kg for males or ≥45 kg for females.
3. All screening assessments (vital signs, physical examination, laboratory tests, ECG) must be within normal limits or deemed not clinically significant by the investigator. One repeat assessment is permitted during the screening period to confirm eligibility.
4. Participants must agree not to donate gametes (sperm or ova), must not be planning pregnancy, and must use a reliable contraceptive method from the time of informed consent signing through 3 months following the last dose.
5. Able to understand study requirements, provide written informed consent, and comply with all trial procedures per protocol.

Exclusion Criteria:

1. Hypersensitivity or allergic to KR23343.
2. History of severe hypersensitivity reactions or multiple drug/food allergies
3. Significant disease affecting the central nervous, cardiovascular, gastrointestinal, respiratory, renal, hematologic, metabolic, or musculoskeletal systems, or any condition considered by the Investigator to make the participant unsuitable for the trial.
4. Any surgical or medical condition that may significantly affect drug absorption, distribution, metabolism, or excretion, or compromise participant safety, including but not limited to urinary tract obstruction, dysuria, gastroenteritis, peptic ulcer disease, or history of gastrointestinal bleeding.
5. History of psychiatric disorders or cerebral dysfunction; suicidal ideation identified by the Columbia-Suicide Severity Rating Scale (C-SSRS) or investigator judgment; or history of self-harm behavior.
6. Abnormal screening investigations meeting any of the following criteria: a) Hepatic dysfunction: ALT or AST>1.5x upper limit of normal (ULN), or total bilirubin >1.3x ULN; b) Creatinine clearance <80 mL/min (calculated by Cockcroft-Gault formula: CrCl = [(140 - age) × weight (kg)] / [0.814 × Scr (μmol/L)], multiplied by 0.85 for females); c) Vital signs outside specified ranges (heart rate <50 or >100 bpm, systolic blood pressure <90 or ≥140 mmHg, diastolic blood pressure <60 or ≥90 mmHg, tympanic temperature <35.7 or >38.0°C); d) QTc-F interval ≥450 ms (males) or ≥470 ms (females), or other clinically significant ECG abnormalities; e) Any other screening abnormality deemed clinically significant by the investigator.
7. Blood loss or donation ≥400 mL within 3 months prior to screening, or planned donation during the study.
8. Use of any medication within 2 weeks (or 5 half-lives, whichever is longer) prior to screening or during the study, including prescription drugs, over-the-counter medications, Chinese herbal products, dietary supplements, vaccines, or any drug known to induce or inhibit hepatic metabolizing enzymes (e.g., CYP3A4, CYP3A5).
9. Participation in a clinical trial involving investigational products, vaccines, or devices within 3 months prior to screening, or within 5 half-lives of the last dose, whichever is longer.
10. History of drug abuse or illicit drug use within 6 months prior to screening, or positive urine drug screen.
11. Hazardous alcohol consumption ( >14 units/week; 1 unit = 360 mL beer, 25 mL 40% spirits, or 100 mL wine) within 6 months prior to screening, inability to abstain from screening through end-of-study, or positive alcohol breath test.
12. Smoking >10 cigarettes per day within the 3 months prior to screening, or inability to abstain from smoking and nicotine products during the trial.
13. Regular consumption of >8 cups/day (1 cup = 250 mL) of grapefruit juice, tea, coffee, or caffeinated beverages within the 3 months prior to screening, or inability to abstain during the trial.
14. Positive serology for hepatitis B surface antigen (HBsAg), hepatitis C virus (HCV) antibody, Treponema pallidum antibody, or human immunodeficiency virus (HIV) antibody.
15. Pregnancy, lactation, or clinically significant abnormal pregnancy test as judged by the investigator.
16. Specific dietary restrictions or inability to adhere to the standardized diet during their CPU stay.
17. Difficult venous access, history of vasovagal syncope (needle or blood phobia), or inability to tolerate venipuncture.
18. Any condition or circumstance that, in the opinion of the Investigator, would make the participant unsuitable for the study.