This is a phase I study to evaluate the safety, tolerability and pharmacokinetics of RSS0343 following multiple oral doses in healthy subjects, as well as its effects on the QT/QTc interval.

Inclusion Criteria:

1. Subjects who provided written informed consent after being fully informed of the trial's purpose, significance, and protocol requirements.
2. Healthy individuals aged 18 to 55 years, inclusive. Males and females
3. Body weight ≥ 50 kg for males and ≥ 45 kg for females. Body mass index (BMI) = weight (kg)/height 2 (m²). BMI between 19 and 28 kg/m², inclusive.
4. Fertile male and female subjects and their partners must agree to use highly effective contraception as stipulated in the protocol, from screening until 6 months (for females) or 3 months (for males) after the last dose. Additionally, fertile female subjects must have a negative serum pregnancy test at screening and prior to the first dose (baseline) and must not be lactating.

Exclusion Criteria:

1. Subjects who smoked more than 5 cigarettes (or equivalent nicotine products) daily within 3 months prior to screening or intended to use tobacco products during the trial.
2. Subjects with frequent alcohol consumption (>15 g/day for females or >25 g/day for males [5g of alcohol is equivalent to 150 mL of beer, 50 mL of wine or approximately 17 mL of low-alcohol liquor], on more than 2 occasions per week) within 6 months prior to screening, or were unable to abstain during the trial, or who tested positive on the alcohol breath test at baseline.
3. Subjects with a history of, or current, drug abuse, or drug dependence (during consultation), or with a positive urine drug screening result.
4. Subjects who had donated blood or experienced a total blood loss of ≥200 mL within 1 month, or ≥400 mL within 3 months prior to dosing, or who had received a blood transfusion within 8 weeks prior to dosing.
5. Subjects with dysphagia; or a history of needle or blood phobia, poor venous access, or inability to tolerate venipuncture.
6. Subjects deemed by the investigators to be unsuitable for the trial for any other reason.
7. Subjects with any clinically significant abnormalities, as determined by the investigator, in physical examination, vital signs, laboratory tests (including hematology, urinalysis, blood biochemistry, coagulation), chest imaging, abdominal ultrasonography, or electrocardiogram.
8. Subjects who tested positive for hepatitis B surface antigen, hepatitis C antibody, syphilis antibody or HIV antibody.
9. Subjects with a known or suspected allergy to the investigational drug or its excipients, or a history of severe allergic reactions (e.g., to drugs, food, toxins).
10. Subjects with any active autoimmune disease or immunodeficiency at screening.
11. Subjects with any history of severe clinical disease, or any condition that, in the investigator's judgment, could compromise trial outcomes, affect drug absorption, distribution, metabolism, or excretion (pharmacokinetics), or pose an undue risk to the subject. This includes, but is not limited to, significant disorders of the circulatory, endocrine, nervous, digestive, urinary, hematological, immune, psychiatric, or metabolic systems.
12. Subjects who had undergone any surgery within 3 months prior to screening, had not fully recovered as determined by the investigator, or planned to undergo surgery during the trial or within 1 month after its completion.