Inclusion (Part 1 - Healthy):
1. Understand and voluntarily sign the informed consent form (ICF).
2. Male or female, aged 18 to 45 years (inclusive).
3. Body weight of 50 to 120 kg, BMI of 18.0 to 28.0 kg/m².
4. Males and females of childbearing potential must agree to use highly effective contraception and refrain from donating sperm/ova for 6 months after the last dose.
Inclusion (Part 2 - IgAN)
1. Understand and voluntarily sign the informed consent form (ICF).
2. Male or female, aged 18 to 65 years (inclusive).
3. Biopsy-confirmed primary IgA nephropathy without known secondary causes within 10 years prior to screening.
4. Persistent proteinuria at screening: 24h-UPCR ≥ 0.75 g/g or 24h-UPE ≥ 1.0 g/24h.
5. eGFR ≥ 45 mL/min/1.73 m² at screening (CKD-EPI 2021 equation).
6. Receiving stable and optimized supportive therapy (ACEI and/or ARB ≥ 12 weeks, stable dose ≥ 4 weeks prior to randomization).
7. Participants of childbearing potential must agree to use highly effective contraception and refrain from donating sperm/ova for 6 months after the last dose.
Exclusion (Both Parts)
* 1\. Known hypersensitivity to any component of IBI3034 or history of severe allergic reactions.
2\. Inability to tolerate subcutaneous injections. 3. Vaccination with a live vaccine within 30 days prior to randomization. 4. Blood donation or blood loss ≥ 400 mL within 3 months prior to screening. 5. Positive serological test for HIV-Ab, Treponema pallidum antibody, HCV-Ab, or any HBV-related markers.
6\. History of disseminated herpes zoster or recurrent localized dermatomal herpes zoster.
7\. Known active tuberculosis or positive IGRA. 8. Concurrent malignancy or lymphoproliferative disease. 9. Immunodeficiency disorders. 10. Severe infection or surgery requiring hospitalization within 6 months prior to randomization.
11\. Pregnant or lactating females. 12. History of drug abuse within 12 months prior to screening. 13. Any other condition that, in the investigator's opinion, makes the participant unsuitable for the study.
Part 2 Specific Exclusions
1. Participation in another drug or medical device clinical trial within 90 days prior to randomization.
2. Systemic corticosteroids (\>10 mg/day for \>14 consecutive days) or immunosuppressive therapy within 12 weeks prior to randomization.
3. Use of renin inhibitors or medications significantly affecting creatinine levels within 4 weeks prior to randomization.
4. Prior use of APRIL monoclonal antibodies, BAFF monoclonal antibodies, BAFF/APRIL dual-targeting agents, TACI/BCMA-targeting agents, etc.
5. Concurrent nephrotic syndrome or hypoalbuminemia.
6. Concurrent other chronic kidney diseases (e.g., diabetic nephropathy, membranous nephropathy).
7. Rapidly progressive glomerulonephritis.
8. Known or suspected immunodeficiency disorders.
9. Poorly controlled blood pressure prior to randomization (systolic BP \> 140 mmHg or diastolic BP \> 90 mmHg).
10. Poorly controlled type 2 diabetes mellitus (HbA1c \> 8%).
11. History of bone marrow, hematopoietic stem cell, or solid organ transplantation.
12. Laboratory abnormalities during screening, such as ALT/AST \> 3.0 × ULN, TBIL \> 1.5 × ULN, etc.
13. Any other condition that, in the investigator's opinion, makes the participant unsuitable for the study
