This study is designed to evaluate the safety, tolerability, PK and PD of multiple subcutaneous injections of GenSci120 in a randomized, double-blind, placebo-controlled, multiple-ascending-dose phase Ib trial involving healthy adult participants.

Inclusion Criteria:

1. Ages 18-55; ≥3 per gender for each cohort.
2. BMI: 18-30; Weight: ≥50 kg (male), ≥45 kg (female).
3. No clinically significant abnormalities in medical history, physical exam, vital signs, or lab/ECG/pulmonary imaging.
4. Men/WOCBP must use effective contraception throughout study; no plans to conceive; WOCBP must have negative pregnancy test and not breastfeeding. Women of non-childbearing potential: post-hysterectomy/salpingectomy or postmenopausal (FSH >40 IU/L).
5. Able to provide informed consent; willing to comply with all study requirements

Exclusion Criteria:

1. Allergy to GenSci120 or severe allergies.
2. Injection site issues affecting evaluation.
3. Significant medical conditions impacting study outcome.
4. History of malignant tumors, including listed cancers.
5. Seizure history, head injury causing unconsciousness.
6. Psychiatric disorders impairing daily activities or cognitive issues.
7. Severe immunodeficiency (e.g., HIV).
8. Recent trauma, surgery, or GI issues affecting absorption.
9. Recent severe infections or antimicrobial treatments.
10. Live vaccines within a month prior to screening.
11. Abnormal vital signs/ECG: BP extremes, QTcF >450ms.
12. Positive for hepatitis B/C, HIV, syphilis during screening.
13. Positive TB test via IGRA.
14. Recent use of immunosuppressive or targeted therapies.
15. Medication use within 14 days prior to randomization.
16. Participation in other clinical trials recently/currently.
17. Excessive alcohol consumption (over six months).
18. Heavy smoking, unwillingness to quit, positive nicotine tests.
19. Positive drug screen for specific substances.
20. Recent soft/hard drug use within specified periods.
21. Blood donation/product receipt recently or poor venous access.
22. Study staff involved in the trial.
23. Other conditions deemed unsuitable by investigators.