The investigators propose a gene therapy strategy for Parkinson's disease - a chemogenetic inhibition technique to intervene in the abnormal activity of the subthalamic nucleus in Parkinson's patients. The investigators design and construct a therapeutic injection agent called STP-001, through an efficient adeno-associated virus capsid (AAV), a neuronal promoter (hSyn), and a chemogenetic effector element (hM4Di). Then, the drug was accurately injected into the bilateral subthalamic nuclei through stereotactic surgery. After the surgery, combined with clozapine, the abnormal activity of the subthalamic nucleus was precisely intervened to improve the core motor symptoms of Parkinson's disease.

This is a single-arm, open-label preliminary safety assessment study design. Six patients with iPD will be recruited from the Department of Neurology of the Second Affiliated Hospital of Zhejiang University School of Medicine. After signing the informed consent form, these 6 participants will be divided into 2 dose groups according to the dose escalation principle and receive the STP-001 injection solution. The virus dose escalation principle is as follows:

After 3 sentinel subjects receive 1×10¹² volts of the virus vector, the research team will assess the safety, tolerance and efficacy of the current drug dosage 3 months later. If the test subjects do not show dose-limiting toxicity and have some efficacy, the sample size will be expanded to 6 at the original dosage. If the test subjects do not show dose-limiting toxicity but have no obvious efficacy, the titer will be increased to 3×10¹² volts and three more participants will be recruited for the trial. Four weeks after the injection of STP-001, when the participants recover, clozapine dose escalation treatment will be carried out. The participants will take clozapine orally every day, with doses of 1/32, 1/16 and 1/8 tablets respectively, taken in the morning and noon, and each dose will be repeated for 3 days, totaling 9 days. If there is no disease progression during this period, the participants will continue to take the 1/8 dose of the drug twice a day as the maintenance dose and undergo monitoring for 12 months.

Inclusion Criteria:

• Age range: 40 - 70 years (inclusive), gender not restricted;
• Diagnosed with primary Parkinson's disease, with H&Y grade ranging from 4 to 5;
• Disease duration of at least 5 years;
• Response to levodopa treatment lasting for at least 12 months;
• Score of the third part of the MDS-UPDRS Part III ≥ 35;
• Improvement rate of the Madopar challenge test ≥ 30%;
• Stable clinical symptoms and drug treatment for at least 4 weeks before screening;
• Capable of understanding and voluntarily signing the informed consent form;
• Participants agree to postpone any neurological surgery, including deep brain stimulation, until the completion of 12-month follow-up;
• The efficacy of dopamine drugs has significantly decreased, or there are obvious motor complications, or severe drug side effects;
• There are no acute adverse reactions to the prescribed olanzapine dose;
• Good compliance and willing to complete all the follow-up as stipulated in this protocol.

Exclusion Criteria:

• Has a past history of brain surgery for Parkinson's disease, such as deep brain stimulation, or other abnormal brain imaging findings;
• Hamilton Depression Scale score ≥ 20;
• Hamilton Anxiety Scale score ≥ 14
• Has a history of brain injury or central nervous system infection;
• MoCA cognitive impairment score < 26 points, and MMSE dementia rating scale cognitive impairment score ≤ 20 points;
• Focal neurological deficits;
• Evidence of major medical or mental illness, such as dementia, psychosis, history of drug abuse or severe depression;
• Atypical Parkinson's disease or secondary Parkinson's disease caused by factors such as trauma, brain tumor, infection, cerebrovascular disease, other neurological diseases or drugs, chemicals or toxins;
• Received other gene or cell therapy drugs;
• Has a history of malignant tumors, but not including treated carcinoma in situ, or medical conditions that are poorly controlled and may increase the risk of surgery;
• Has a history of stroke, or obvious cardiovascular diseases, diabetes;
• Clinically obvious or laboratory-detected infections;
• Chronic immunosuppressive therapy, including chronic steroids, immunotherapy, cytotoxic therapy and chemotherapy;
• Coagulation disorders or inability to temporarily stop any anticoagulant or antiplatelet treatment before surgery;
• Severe liver disease (AST/ALT ≥ 2.5 times the upper limit of normal (ULN));
• Any factor that may prevent the subject from following the study protocol, including medical or social factors, including geographical inconvenience;
• Any other situation that the investigator deems unsuitable for participation in this study.

As this study involves participants' personal health information, in strict compliance with the ethical approval terms and the Personal Information Protection Law, the original IPD will not be publicly shared. The data is currently stored on the secure server , and can be provided to eligible researchers under the condition of adhering to the data protection protocol. Researchers interested in conducting confirmatory or collaborative analyses can contact the corresponding author to submit a proposal.