Inclusion Criteria:
1. Aged 18 to 70 years (inclusive), with no restriction on sex.
2. Clinically diagnosed with moderate to severe (Stage II or III) periodontitis according to the 2018 International Classification of Periodontal and Peri-Implant Diseases. participants must have at least 2 non-adjacent natural teeth (excluding third molars) in the dentition with a Probing Depth (PD) of 5 to 8 mm (inclusive), and at least 1 site per tooth with a BI score \> 2.
3. Participants and their partners must agree to practice effective non-pharmacological contraception from the time of signing the Informed Consent Form (ICF) until 3 months after the study completion. For female participants of childbearing potential, a negative pregnancy test result is required within 7 days prior to the first dose.
4. Voluntary participation in the trial and signed approval of the ICF.
Exclusion Criteria:
1. At the time of screening, the target tooth and/or adjacent teeth (as determined by the investigator to affect the target tooth) exhibit periapical periodontitis, pericoronitis, or combined pulp-periodontal lesions; or the participant has orthodontic appliances (including fixed lingual retainers, etc.);
2. At screening, the target tooth and/or adjacent teeth (as determined by the investigator to affect the target tooth) are found by the investigator to have severe caries or caries requiring immediate treatment;
3. At screening, the participant has a periodontal or dental abscess, or a tumor of the oral soft or hard tissues;
4. Participants who have previously undergone periodontal surgery on the target teeth and/or adjacent teeth (as determined by the investigator to affect the target teeth), or who have undergone subgingival scaling and root planning (SRP) within 6 months prior to screening;
5. Participants with a history of Neisseria meningitidis infection;
6. Participants with a history of splenectomy or congenital asplenia;
7. Participants with impaired immune function (e.g., HIV infection, neutropenia, complement deficiency, etc.);
8. Participants with autoimmune diseases that the investigator determines may interfere with the evaluation of the study disease, such as Sjögren's syndrome, systemic lupus erythematosus, psoriasis, rheumatoid arthritis, etc.;
9. Participants with poorly controlled blood pressure at screening, such as systolic blood pressure ≥160 mmHg and/or diastolic blood pressure ≥100 mmHg;
10. Participants with glycated hemoglobin (HbA1c) \>7.5% or severe diabetic complications at screening;
11. Participants with severe or poorly controlled systemic diseases at screening, as determined by the investigator, such as respiratory, gastrointestinal, cardiovascular, hematological, urological, neurological, or psychiatric disorders;
12. Participants who have continuously taken medications deemed by the investigator to interfere with the study within 1 month prior to screening, such as nifedipine, phenytoin, or anticoagulants (e.g., warfarin);
13. Participants who have received systemic antibiotic therapy within 3 months prior to screening;
14. Participants who have taken nonsteroidal anti-inflammatory drugs (NSAIDs) or corticosteroids on a long-term basis (≥3 times per week) prior to screening;
15. Participants with any of the following laboratory test results at the time of screening:
* ALT or AST \> 2.5 times the upper limit of normal (ULN) or serum total bilirubin \> 1.5 times ULN;
* Serum creatinine \> 1.5 times the upper ULN;
* International Normalized Ratio (INR) ≥ 1.5 times ULN, or activated partial thromboplastin time (APTT) ≥ 1.5 times ULN (excluding participants currently receiving anticoagulant therapy);
* Platelet count (PLT) \< 100 × 10⁹/L;
16. Participants who test positive for hepatitis B surface antigen (HBsAg), hepatitis C virus antibody (HCV-Ab), human immunodeficiency virus antibody (HIV-Ab), or Treponema pallidum antibody (TP-Ab) at screening;
17. Participants with a history of malignant tumors within 5 years prior to screening;
18. Participants with a history of heavy smoking (≥10 cigarettes per day) within 12 months prior to screening;
19. Participants with known allergies to any drugs or materials used during surgery;
20. Pregnant or breastfeeding women;
21. Participants who have participated in other clinical trials within 30 days prior to screening or who plan to participate in other clinical trials during the study period;
22. Participants assessed by the investigator as having other conditions rendering them unsuitable for participation in the clinical study.
