A Safety and Tolerability Evaluation of Ascending Single Oral Doses of Metacavir Enteric-coated Capsules Using a Randomized，Double-blind, Placebo-controlled Design conducted in Chinese Healthy Adult Volunteers.

A study to evaluate the safety and tolerability of ascending single oral doses of metacavir enteric-coated capsules using a placebo-controlled design conducted in Chinese healthy adult volunteers, and to provide references for the clinical trial of the next phase Ⅰ and Ⅱ.

48 eligible healthy subjects are involved. According to the set ascending-doses groups, subjects will be randomized in a 3:1 proportion to orally take a single dose of Metacavir enteric-coated capsule or placebo on the condition of fasting. Each group has 8 people, evenly composed of men and women. The beginning dose of the study is 40mg/d.According to the dose escalation method, subjects who have successfully completed tests of the previous dose group and passed the safety assessment will enter the next dose group with the same method. All subjects check in the phaseⅠresearch center one day early before taking the test drug. Vital signs and ECG will be observed before and 0.5,1,2,4,8,12,18,24,48,72 hours after administration and at the follow-up day which is the 7th day since administration. Laboratory tests will be conducted before and 6,24,48,72 hours after administration and at the follow-up day , and the adverse drug events are observed throughout the test.

Inclusion Criteria:

1. Healthy volunteers aged 18 to 45 years old ;
2. Body mass index (BMI) above/equal 18 and below 28 kg/m2;
3. Child bearing potential, has a negative serum pregnancy test at screening period, and agrees to use contraceptions consistently and correctly in 14 days after dosing;
4. No smoking in a year before post-dosing of study drug;
5. Give their signed written informed consent to participate.

Exclusion Criteria:

1. Subjects who have clinically significant abnormal laboratory test results;
2. Subjects with clinically significant abnormal ECG;
3. Subjects with cardiac or blood disease affecting the safety and pharmacokinetics;
4. Subjects with liver or renal disease affecting the safety and pharmacokinetics;
5. Subjects with digestive system disease affecting the safety of study drug;
6. Subjects with other acute or chronic disease affecting pharmacokinetics and product metabolism;
7. A positive hepatitis B surface antigen, hepatitis C or HIV test result;
8. History of hypersensitivity or allergy to any of the study drugs or to drugs of similar chemical classes;
9. Subjects, who in the opinion of the investigator, significantly abuse alcohol;
10. Drink in 36 hours before post-dosing of study drug;
11. Ingest any foods or beverages which may affect pharmacokinetics;
12. Drug abuse,a history of poisoning;
13. Smokers(use tobacco products in a year before post-dosing of study drug);
14. Subjects who had received other medications within 2 weeks prior to the first administration of Investigational Product,and the original and main metabolites were not completely eliminated;
15. Subjects who participated in any other clinical trials within 3 months prior to the administration of Investigational Product;
16. Subjects who had suffered from hemorrhage or blood donation over 200ml will be excluded; 17. Subjects over exercised accompanied with fatigue and muscle aches within 1 week period to the administration of Investigational Product;

18．Children,women who are pregnant,lactating,with childbearing potential and who are using acyeterions; 19．Haven't given their signed written informed consent to participate; 20．Subjects in the opinion of the investigator, could not participate in this study.