This is a phase 1, randomised, open-label, three-way, three-period, crossover relative bioavailability study to assess the pharmacokinetics of HRS-6209 capsules (old and new formulation) in healthy participants. The effect of high-fat food on the pharmacokinetics of HRS-6209 in new formulation will also be evaluated. A total of 21 healthy participants will be randomised to receive a single oral dose of HRS-6209 in three treatment periods: old formulation (fasted); new formulation (fasted); new formulation (fasted).

Inclusion Criteria:

1. Healthy men and women aged 18 to 50 years old at informed consent signing.
2. Male body weight ≥ 50 kg, female ≥ 45 kg; BMI 19 to 26 kg/m² at screening and baseline.
3. Have no clinically significant abnormalities at screening and baseline.
4. Fertile females and males with fertile female partners: effective contraception 2 weeks before consent, and sustained until 6 months after the last dose (abstinence or highly effective contraception); no sperm/egg donation.

Exclusion Criteria:

1. Current or history of clinically significant disorders of any major system (urinary, circulatory, endocrine, nervous, digestive, respiratory, hematologic, immune, psychiatric, metabolic, etc.) or any other condition that may interfere with study results per investigator judgment.
2. History of epilepsy, including febrile seizures in childhood, loss of consciousness, transient ischemic attack, or any condition predisposing to seizures (e.g., cerebrovascular disease, brain injury, stroke, brain cancer).
3. Clinically significant acute illness within 1 month prior to screening, including fever or febrile symptoms, viral, bacterial (including upper respiratory tract infection), or non-cutaneous fungal infections.
4. Any surgery within 6 months prior to study, or planned surgery during study period; prior surgery affecting gastrointestinal absorption (including gastrectomy, bowel resection, bariatric surgery) or affecting liver function.
5. Positive for anti-HCV, anti-HIV, HBsAg, or syphilis antibodies.
6. Blood donation or loss ≥ 400 mL within 3 months, or ≥ 200 mL within 1 month prior to screening; blood transfusion or use of blood products within 3 months prior to screening.
7. Long-term use (> 7 consecutive days) of hepatotoxic drugs within 6 months; use of any drug affecting liver metabolism within 1 month prior to first dose; use of other drugs (prescription, OTC, herbal, vitamins, calcium, etc.) within 14 days prior to first dose, other than those affecting liver metabolism.
8. Participation in another clinical trial with investigational drug within 3 months; vaccination within 3 months prior to screening or planned during study.
9. History of drug abuse/dependence; positive urine drug screen at screening.
10. History of heavy smoking (average ≥ 5 cigarettes/day) within 3 months prior to screening; inability to abstain from any tobacco products during study; positive smoke screen.
11. Alcoholism (average daily intake exceeding: > 14 units/week; 1 unit = 285 mL beer, 25 mL spirits, or 100 mL wine); positive alcohol screen; inability to abstain from alcohol during study.
12. Special dietary requirements or inability to comply with standardized meals.
13. Dysphagia, difficulty with venous blood collection, or inability to tolerate intensive blood sampling.
14. Other conditions that, in the investigator's judgment, make the participant unsuitable for the study.