A Phase I Study of XJ103 in Chinese Healthy Subjects

Inclusion Criteria: 1. Age 18 through 45 years at screening. 2. Male weight ≥ 50.0 kg, female weight ≥ 45.0 kg, and body mass index (BMI) within the range of 19.0 to 26.0 kg/m2 (including critical values). 3. The subjects have no pregnancy plan and voluntarily avoid pregnancy from signing the informed consent form until the end of the trail. 4. Healthy on the basis of physical examination and medical and surgical history and twelve-lead electrocardiogram (ECG) without clinically relevant abnormalities. 5. Written informed consent and any locally required authorization (eg, HIPAA) obtained from the subject prior to performing any protocol-related procedures, including screening evaluations. Exclusion Criteria: 1. Subjects with any abnormalities of respiratory system, circulatory system, digestive system, nervous system, skeletal muscle system, blood and lymphatic system, immune system and endocrine system. 2. History of allergy to drugs or biological products or individuals with allergic constitution. 3. Acute infection within 4 weeks prior to study entry. 4. Suffer from diseases caused by streptococcus pneumoniae within 1 year prior to study entry, such as pneumococcal pneumonia, pneumococcal meningitis, etc. 5. Receipt of any standard vaccine against streptococcus pneumoniae before the study period. 6. Receipt of any standard vaccine within 4 weeks prior to investigational product dosing or plan to vaccinate during the study period. 7. Receipt of any major surgery within 3 months prior to the start of the trial, or have not recovered from surgery, or plan to have a surgical during the trial. 8. Those who cannot tolerate venipuncture, or have a history of injector and blood sickness, or are not suitable for venous blood collection. 9. Subjects with a history of drug abuse or drug use, or those with positive urine drug screening. 10. Blood donation or massive blood loss (\> 200 mL) within three months prior to screening or plan to donate blood, receive blood transfusions, or use blood products during the trial period or within 1 month after the end of the trial. 11. Pregnant or lactating women. 12. Use of any prescription drugs, over-the-counter drugs, vitamin products or herbal medicines within 14 days prior to screening. 13. Smoke more than 5 cigarettes per day within three months prior to screening. 14. Frequent drinkers in the three months before screening, i.e. those who drink more than or equal to 14 units of alcohol per week on average (1 unit=17.7 ml ethanol, 1 unit=354 ml beer with 5% alcohol, 44.25 ml spirits with 40% alcohol, or 147.5 ml wine with 12% alcohol), or those who do not agree to ban alcohol during the study period. 15. Evidence of infection with HBV, hepatitis C, HIV, or syphilis. 16. Positive alcohol breath test. 17. Subjects with special dietary requirements or cannot accept a unified diet. 18. Participation in other clinical trials within three months prior to enrollment or plan to participate in other clinical trials during this period. 19. Any other factors evaluated by investigators that patients cannot be enrolled.