This is a non-randomized, open label, dose-escalation study to evaluate the safety and efficacy of KL002 in the treatment of advanced primary Parkinson's disease.

Condition or disease: Parkinson's Disease Intervention/treatment: Drug: KL002 Phase: NA

9 patients will be enrolled to this open-label dose escalation study to evaluate up to three dose levels of KL002 of three patients each. All patients will receive bilateral intraputaminal injections of KL002 through stereotactic brain surgery. The safety and potential clinical responses to KL002 will be assessed by clinical evaluations of Parkinson's disease, cognitive tests, laboratory blood tests and neuroimaging.

Inclusion Criteria:

1. Males/females between 40 and 70 years (inclusive)
2. Diagnosed with idiopathic Parkinson's disease, Hoehn and Yahr stage 4 and 5
3. Disease duration at least 5 years
4. MDS UPDRS Part III (total motor) score ≥ 25 and a maximum of 60 in the OFF state
5. Good compliance and can complete all follow-up in accordance with the protocol requirements

Exclusion Criteria:

1. Prior brain surgery including deep brain stimulation or abnormal brain imaging.
2. Presence of depression as measured by Hamilton Depression Scale ≥20
3. History of brain injury or central nervous system infection.
4. Cognitive impairment score<26 on MoCA and ≤ 20 on MMSE dementia scale
5. Evidence of significant medical or psychosis, such as dementia, psychosis, and a history of drug abuse
6. Atypical or secondary parkinsonism, including but not limited to symptoms believed to be due to trauma, brain tumor, infection, cerebrovascular disease, other neurological disease, or to drugs, chemicals, or toxins.
7. Prior gene therapy.
8. Chronic immunosuppressive therapy, including chronic steroids, immunotherapy, cytotoxic therapy and chemotherapy
9. Any other conditions that the investigator believed unsuitable for participation in this study.