The Safety and Tolerability of STSA-1301 Subcutaneous Injection in Healthy Subjects

Inclusion Criteria:

1. Healthy subjects, male and female, aged between 18 and 65 years, inclusive;

2. Body mass index: 18.0～28.0 kg/m2, inclusive; weight ≥50 kg for males and ≥45kg forfemales at enrollment;

3. Subjects (including their partners) agree to take highly effective contraceptivemeasures during the study, and they have no birth plan or sperm donation plan within 3 months after the end of the study;

4. Medical histories, physical examinations, laboratory examinations and study-relatedexaminations and tests of the subjects show normal results or mild abnormalitieswith no clinical significance before enrollment, and the Investigator judges thatthey are eligible;

5. Subjects are aware of the risks of the study, and voluntarily participate in theclinical study and sign an informed consent form (ICF).

Exclusion Criteria:

1. Pregnant or lactating women;

2. History of cardiovascular, respiratory, kidney, liver, metabolism, endocrine,gastrointestinal, blood, nerve, skin and mental illness, cancer or other majordisease that in the judgment of the Investigator might put the subject as risk onthis study.

3. After splenectomy or any major surgery within 6 months prior to screening;

4. Subjects have an active infection or have a serious infection (leading tohospitalization or requiring parenteral antibiotic therapy) within 6 weeks prior tothe first dose; subjects with clinically active or chronic uncontrolled bacterial,viral or fungal infections at screening;

5. Total IgG was less than the lower limit of normal at screening. Subjects withabsolute neutrophil count <1.5X109/L and/or absolute lymphocyte count <1.0X109/L;

6. Subjects have a history of malignancy;

7. Subjects who are allergic to this product or any of its ingredients, history ofeczema, asthma or other allergic diseases;

8. Subjects are TIGRA (T cell interferon gamma release assay) positive at screening. IfTIGRA is not available, a PPD skin test may be used instead and chest imagingperformed at screening showing evidence of latent/active tuberculosis (TB);

9. Positive screening test results for human immunodeficiency virus (HIV) antibodies,syphilis specific antibody, hepatitis B surface antigen (HBsAg) or hepatitis Cantibody (Anti-HCV);

10. Presence of electrocardiogram (ECG) abnormalities during the screening period, asdefined by an Investigator;

11. Subjects have any conditions affecting blood collection;

12. Subjects whose daily consumption of coffee, tea and/or cola is more than 750 mL inthe last 3 months before enrollment;

13. Subject who have nicotine consumption more than 5 cigarettes or the equivalentamount of tobacco per day within 3 months prior to screening;

14. Subjects whose daily consumption of alcohol at the time of screening or at any timewithin the prior 6 months is more than 2 standard drinks, where 1 standard drink = 360 mL or 12 oz (1 can) of regular-strength (5%) beer; 150 mL or 5 oz wine; 45 mL or 1.5 oz liquor/spirits (40%); abnormal alcohol test results at screening or baseline;

15. History of drug abuse within 1 year prior to screening; subjects with a positiveurine drug abuse screen at screening or baseline;

16. Blood loss or donation>400mL within 3 months prior to screening or history oftransfusion or use of any blood products within 3 months prior to enrollment;

17. Participation as a subject in any drug or vaccine or medical device clinical trialwithin 3 months prior to screening;

18. Vaccination or planned vaccination within 4 weeks prior to screening to 3 monthsafter end of dosing;

19. Subjects who have taken drugs that may affect immune function within 6 months beforescreening, have received any monoclonal antibody or biological agent for treatmentwithin the previous 3 months, and have previous treatment with any prescribedmedications, over-the-counter (OTC) medications, herbal medicines or othersupplements within 14 days prior to screening;

20. Subjects with any factors that would, in the Investigator's judgment, preclude themfrom participating in this study.