• Body weight range of ≥40 kg (88 lbs) to ≤110 kg (242 lbs) and a body mass index (BMI) of 18 to 34 kg/m2.

• Diagnosis of Parkinson's Disease (PD) per UK Parkinson's Disease Society Brain Bank Clinical Diagnostic Criteria.

• Hoehn and Yahr Stage III-IV (as determined in Practically Defined OFF state).

• Stable use of background medications at least 8 weeks prior to investigational product (IP) administration, including but not limited to those used for treatment of PD. Gaucher Disease-PD patients receiving GD treatments should be on a stable regimen of their ERT or substrate replacement therapy (SRT) medication for at least 3 months prior to screening.

• At least 1 pathogenic GBA1 mutation confirmed by the central laboratory

• Negative screening test for Mycobacterium tuberculosis (MTB), documented negative MTB test within 1 year prior to Screening, or clearance by an infectious disease specialist.

• Patient and/or patient's legally authorized representative (LAR) has the ability to understand the purpose and risks of the study and provide written informed consent and authorization to use protected health information in accordance with national and local privacy regulations.

• Patient has a reliable study partner/informant (e.g., family member, friend) willing and able to participate in the study as a source of information on the patient's health status and cognitive and functional abilities (including providing input into the rating scales). The study partner should have regular contact with the patient (in person or via phone/video communication). The study partner must sign a separate partner informed consent form (ICF) indicating that she/he understands the study requirements and is willing to participate and attend study visits requiring study partner input.

• Women of nonchildbearing potential must be either surgically sterile or postmenopausal. Men and women of childbearing potential must use a highly effective method of contraception consistently and correctly for the duration of the study including the long-term follow-up. Individuals in an exclusively same sex relationship (as their preferred and usual lifestyle) are not required to use contraception.

• Men must agree to abstain from sperm donation for the duration of the study, including long-term follow-up.

• Women must agree to abstain from egg donation for the duration of the study, including long-term follow-up.

• Women of childbearing potential cannot be pregnant or lactating/breastfeeding and must have a negative result for serum pregnancy test at Screening.

• Patient is generally ambulatory, not dependent on walker or wheelchair

• Patient is living in the community (i.e., not in nursing home); some levels of assisted living may be permitted at the discretion of the Investigator.

• Pneumococcal and shingles vaccines are required within 10 years of Screening (allowed to be performed during Screening but must be given at least 4 weeks prior to start of the immunosuppressant treatment).

• Patient is up to date with age and gender-appropriate cancer screening as per local standard of care based on Principal Investigator's (PI) judgment.