Inclusion Criteria:
The participants must meet all of the following criteria to be included in this study:
1. The participants must fully understand and comply with the research procedures, voluntarily participate in the study and sign the informed consent form;
2. At the time of signing the informed consent, the participants must be aged 18 or above and under 75 years old, with no gender restrictions;
3. During the screening process, the participants must have had primary Parkinson's disease for at least 5 years, have a confirmed medical history record and meet the diagnostic criteria for primary Parkinson's disease as defined by the International Parkinson and Movement Disorder Society (MDS);
4. During the screening, according to the MDS-UPDRS scoring scale, the Hoehn-Yahr classification of the "off" period of drug treatment is 2 to 4;
5. During the screening, the score of the third part of the MDS-UPDRS in the "off" period must be greater than 30;
6. During the screening, the stable duration of Parkinson's disease and the stable duration of the optimized drug dosage must be at least 4 weeks, and the duration of levodopa use must be at least 1 year;
7. During the screening, the participants must have a response to levodopa treatment, and the levodopa loading test must be positive;
8. The participants must experience a decline in the efficacy of anti-Parkinson's disease treatment, which affects their quality of life;
9. The participants must have good compliance and be able to cooperate with the completion of the assessment items of the trial; For participants with reproductive potential and their partners, they must be free from pregnancy plans for at least 2 weeks before the screening to at least 1 year after the administration of the drug, and must agree to take effective non-drug contraceptive measures during the trial (such as condoms, non-drug intrauterine devices, etc.), except for those who have taken permanent contraceptive measures, such as bilateral tubal ligation, vasectomy, etc.
Exclusion Criteria:
If the subjects meet any of the following criteria, they will not be included in this study:
1. Allergic to the study drug or its excipients, or allergic to similar drugs of the study drug, or have a history of severe allergies (including any food allergy or drug allergy);
2. Have a previous history of mental disorders, serious diseases, or other significant diseases that may affect safety;
3. Have a known history of human immunodeficiency virus (HIV) infection (HIV 1/2 antibody positive), or acquired immunodeficiency syndrome-related diseases, or positive HIV serological test results;
4. Positive for hepatitis B surface antigen (HBsAg), or hepatitis C antibody (HCV-Ab), or Treponema pallidum antibody positive;
5. Previously diagnosed with secondary or atypical Parkinson's syndrome caused by drugs, metabolic disorders, or other reasons;
6. Previously diagnosed with epilepsy, stroke, multiple sclerosis, poorly controlled or progressive neurological diseases;
7. Have new or unstable mental symptoms within 1 year before screening (such as mental confusion, severe depression, or tendencies towards self-harm/suicide);
8. Have a history of dementia or severe cognitive dysfunction; or have obvious dementia or cognitive dysfunction at screening; the 1.1 part of the MDS-UPDRS score at screening is \> 3; due to dementia, the subject's compliance is affected, diary cannot be accurately recorded, and/or the informed consent cannot be signed;
9. Have other serious systemic diseases at the time of screening;
10. Have any history of malignant tumors in the past;
11. Are participating in other clinical trials, or have participated in other clinical studies within 3 months before administration and received intervention treatment;
12. Have active infections at the screening period, and still need systemic application of antibiotics, antifungal, antiviral treatment at baseline and the infection has not been controlled;
13. Have a history of stroke, unstable angina pectoris, or myocardial infarction attack within 6 months before screening;
14. Have a history of schizophrenia or other severe mental disorders, drug or alcohol abuse;
15. Pregnant or lactating women; Subjects deemed unsuitable for participation in the study by the investigator's comprehensive assessment.
