Study to Assess Relative Bioavailability of GP681 Formulations in Healthy Chinese Male Subjects

The primary objective is to evaluate the relative bioavailability and pharmacokinetic profile of a single oral dose of the test formulation, GP681 Powder for Oral Suspension (20 mg/sachet), compared to the reference formulation, GP681 tablet (20 mg/tablet), in healthy Chinese male subjects. The secondary objectives are to assess the safety of a single oral dose of the GP681 Powder for Oral Suspension (20 mg/sachet) and GP681 tablet (20 mg/tablet) in healthy Chinese male subjects, as well as the palatability (taste acceptability) of the GP681 Powder for Oral Suspension.


Eligibility Criteria:
Inclusion Criteria:

1. Gender: Healthy male subjects.
2. Age: 18 to 45 years (inclusive).
3. Body Weight: Body mass index (BMI = weight (kg)/height2 (m2)) between 19.0 and 26.0 kg/m2 (inclusive), with body weight ≥ 50.0 kg.
4. Taste Perception Ability: Successfully passed the taste perception ability test.
5. Informed Consent: Fully understands the study's purpose, nature, requirements, methodology, and potential adverse reactions; voluntarily agrees to participate in the clinical trial and signs the informed consent form prior to any study procedures.
6. Contraception: Subject (and their partner) has no plans to conceive or donate sperm from the time of first dosing until 3 months after the last dose and agrees to use effective contraception during this period.

Exclusion Criteria:

1. Clinically significant abnormalities, as determined by the investigator, including history of neurological, respiratory, cardiovascular, gastrointestinal, urinary, hematological and lymphatic, endocrine, musculoskeletal, or other disorders that could affect study results, or history of gastrointestinal disease within 3 months prior to screening.
2. Inability to accurately express true taste perception.
3. Dysfunction in taste or olfactory senses.
4. Known hypersensitivity or allergy to the investigational product or any of its components (e.g., copovidone, crospovidone, lactose, microcrystalline cellulose, mannitol, maltitol, hydroxypropyl methylcellulose, colloidal silicon dioxide, sodium stearyl fumarate, sucralose, strawberry flavoring), or history of allergic diseases or a predisposition to allergies.
5. Clinically significant abnormalities in vital signs, physical examination, clinical laboratory tests, 12-lead ECG, or chest X-ray (posteroanterior view), or QTcF \>450 ms, as assessed by the investigator.
6. Positive test results for hepatitis B surface antigen (HBsAg), HCV antibodies, Treponema pallidum antibodies, or HIV antibodies.
7. Smoking ≥10 cigarettes per day within 3 months prior to the first dose.
8. Surgical procedure within 3 months before the first dose or planned surgery during the study period.
9. Blood donation or significant blood loss ≥400 mL within 3 months before the first dose, or plans to donate blood within 3 months after the study.
10. Participation in another clinical drug trial within 3 months before the first dose.
11. Difficulty swallowing.
12. Intolerance to skin puncture, fear of blood or needles, or poor venous access for blood sampling.
13. Special dietary requirements or inability to adhere to the provided diet and study dietary restrictions.
14. Positive urine drug screen, history of substance abuse within the past 5 years, or use of illicit drugs within 3 months before the first dose.
15. Alcohol consumption exceeding 21 units per week (1 unit = 360 mL beer, 45 mL spirits with 40% alcohol, or 150 mL wine) within 6 months prior to screening, or a positive breath alcohol test.
16. Use of any drugs known to inhibit or induce hepatic drug metabolism (e.g., inducers like barbiturates, carbamazepine, phenytoin, glucocorticoids, omeprazole; inhibitors like SSRIs, cimetidine, diltiazem, macrolides, nitroimidazoles, sedatives, verapamil, fluoroquinolones, antihistamines) within 30 days before the first dose.
17. Use of any prescription drugs, over-the-counter medications, herbal remedies, or supplements within 2 weeks prior to the first dose.
18. Vaccination within 2 weeks before the first dose, or planned vaccination during the study.
19. Consumption of foods or beverages rich in caffeine, poppy seeds, and/or theobromine, theophylline, or grapefruit (e.g., coffee, strong tea, chocolate, caffeinated carbonated drinks, cola, grapefruit juice) within 48 hours before the first dose, or engaging in vigorous exercise within 48 hours before the first dose.
20. Any other condition deemed unsuitable for study participation by the investigator.