Inclusion Criteria:
1. Understand and comply with the study procedures, voluntarily participate in this trial, and sign the informed consent form.
2. Aged 18-55 years, inclusive.
3. Body weight ≥50 kg for males and ≥45 kg for females; body mass index (BMI) 18.5-28.0 kg/m², inclusive.
4. Serum IgA, IgG, and IgM are within the normal reference range.
5. Medical history review, physical examination, laboratory tests, vital signs, imaging examinations, etc. are normal, or are judged by the investigator as abnormal but not clinically significant.
6. From signing the informed consent form until the end of the trial or within 3 months after the last dose of the investigational product, whichever is longer: no plan to donate sperm or eggs, no plan for pregnancy, and willingness to use effective contraception.
Exclusion Criteria:
1. History of definite food or drug allergy, or known allergy to the investigational product or its excipients.
2. Prior use of any biologic targeting APRIL or MASP-2.
3. Use of any prescription or non-prescription drug within 14 days before Screening, or still within 5 half-lives of the drug before Screening, whichever is longer.
4. Use of other therapeutic biologics within 1 month before Screening; or still within 5 half-lives of the drug before Screening, whichever is longer.
5. Blood donation/blood loss \>400 mL within 3 months before Screening, or \>200 mL within 4 weeks before Screening.
6. Average daily smoking of more than 5 cigarettes per day within 3 months before Screening.
7. Weekly alcohol intake exceeding 14 units of alcohol within 3 months before Screening - or positive alcohol breath test on D-1.
8. History of drug abuse within 5 years before Screening, or positive urine drug screen on D-1.
9. History of active tuberculosis, or positive tuberculosis screening at Screening.
10. History of fainting during needle insertion or blood draw, or difficult blood collection.
11. Severe infection within 1 month before Screening; or hospitalization due to infection, or receipt of systemic antibiotics/antiviral therapy, within 1 month before Screening.
12. Surgery within 3 months before Screening, or planned surgery of Grade 2 or above as defined in the Medical Institution Surgical Procedure Classification Management Measures during the study.
13. QT interval corrected by Fridericia's formula (QTcF) ≥450 ms for males or ≥460 ms for females at Screening or on D-1.
14. Positive hepatitis B surface antigen (HBsAg), hepatitis C virus antibody (HCV Ab), Treponema pallidum-specific antibody, or human immunodeficiency virus antibody (HIV Ab) at Screening.
15. Presence of a disease that the investigator judges may affect the pharmacokinetic characteristics of the investigational product.
16. Pregnant or lactating women, or positive pregnancy test at Screening or on D-1.
