UB-312 in Patients With Synucleinopathies

Inclusion Criteria: 1. Written informed consent is signed and dated by the participant. 2. Male or female aged 40 to 75 years old, inclusive, at screening. 3. Participants must have a body mass index (BMI) between 18 and 32 kg/m2, inclusive at screening, and with a minimum weight of 50 kg. 4. Expected to be able to undergo all study procedures. 5. Women must be of non-childbearing potential (postmenopausal for at least 12 months before screening or surgically sterile) or, if of childbearing potential, must be using medically acceptable contraceptive measures throughout the study and for at least 24 weeks after their last dose of study treatment. 6. Male participants and their partners of childbearing potential must commit to using medically acceptable contraception for the study duration and at least 90 days after their last dose of study treatment. Men must refrain from donating sperm during this same period. The female partners should use a medically acceptable contraception method, and these contraceptive measures should be used throughout the study and for at least 90 days after their last dose of study treatment. 7. A diagnosis of PD or MSA, confirmed by the PI, as per the current Movement Disorders Society's criteria (Postuma 2015, Wenning 2022). 8. Stable treatment of permitted antiparkinsonian medications from 30 days before first study drug administration or 60 days for MAO-B inhibitors and expected to remain stable throughout the study unless required adjustment or initiation per the investigator's judgment; except for short-acting rescue medications, which are allowed (see Section 7.1 for the list of permitted medications). 9. Eligible participants must be fully vaccinated against COVID-19 according to local guidelines. Participants also must have received a COVID-19 booster vaccination, and the interval between booster vaccination and sample collection for inflammatory markers at Screening should be at least seven days. 10. Subjects with a MOCA score \> 21 at screening and throughout enrollment. Exclusion Criteria: 1. Clinically significant abnormalities, as judged by the investigator, in test results (including hepatic and renal panels, complete blood count, chemistry panel, a level of anti-cyclic citrullinated peptide (anti-CCP) above the upper limit of normal (ULN) at Screening, positive antinuclear antibodies (ANA), except judged to be clinically irrelevant by the investigator, urinalysis, ECG and imaging), or vital signs. In the case of uncertain or questionable results, tests performed during screening may be repeated before randomization to confirm eligibility or judged to be clinically irrelevant. 2. History of medical, neurological, or psychiatric conditions, which in the opinion of the investigator, may compromise the participant's safety or scientific value of the study, posing an unacceptable risk to the participant or interfering with the participant's ability to comply with the study procedures or abide by study restrictions. 3. History of Substance Use Disorder within the past 2 years before screening (Diagnostic and Statistical Manual of Mental Disorders-5 \[DSM-V\] criteria). 4. Acute or chronic infection with human immunodeficiency virus (HIV), hepatitis C virus (HCV), or hepatitis B virus (HBV) at Screening or any confirmed or suspected immunosuppressive or immunodeficient condition, including HIV-1, HIV-2 infection, or cytotoxic therapy in the previous 5 years. 5. History or evidence of an autoimmune disorder (e.g. Sjogren's syndrome, systemic lupus erythematosus, rheumatoid arthritis, multiple sclerosis, etc.), which in the opinion of the investigator may compromise the patient's safety or scientific value of the study, posing an unacceptable risk to the participant. 6. History of anergy. 7. Any confirmed significant allergic reactions (urticaria or anaphylaxis) against any drug or vaccine, or multiple drug allergies (non-active hay fever is acceptable). 8. History of cancer (except basal cell and in situ squamous cell carcinomas of the skin that have been excised and resolved) which has not been in remission for at least 5 years before Screening. 9. Contraindications to MRI, including but not limited to the presence of metal devices or implants (e.g., pacemaker, vascular- or heart-valves, stents, clips), metal deposited in the body (e.g. bullets or shells), or metal grains in the eyes. 10. Receipt of an investigational product or device, or participation in a drug research study within 90 days before baseline at V1. 11. Participated/participating in any clinical trial with monoclonal antibodies or vaccines directed at aSyn. 12. Underwent any procedures/studies involving intracranial surgery, implantation of a device into the brain, or stem cell study. 13. Pregnancy, confirmed by a positive pregnancy test. 14. Participants who are currently breastfeeding or intend to breastfeed during the study. Participants should not be willing to get pregnant and breastfeed till 24 weeks after the last injection. 15. Use of any prohibited medications within 30 days or 5 half-lives (whichever is greater) before Screening till the end-of-study; also excluded administration of chronic (defined as more than 14 days) immunosuppressants or other immune modifying drugs within 6 months of Screening (including prednisone or equivalent, greater than or equal to 0.5 mg/kg/day; except Intranasal, inhalation, and topical steroids are allowed). 16. Immunization or vaccination will be prohibited within 2 weeks before Screening. Regular vaccinations scheduled for preventative illnesses (e.g., flu, COVID-19) required as per local guidelines after Screening until Week 16 need to be discussed with the Investigator and approved on a case-by-case basis. Vaccinations after Week 16 until the end of the study are allowed if not within 2 weeks of (e.g., 2 weeks before and 2 weeks after) each post-baseline IP administration. 17. Any contraindication to undergoing a lumbar puncture (e.g., anatomical variations or local skin infection), as judged by the investigator. 18. Loss or donation of blood over 500 mL within three months before Screening or intention to donate blood or blood products for transfusion during the study and 13 months after their last dose. 19. Received blood and/or blood derivatives treatment within 3 months before Screening. 20. Positive test result for SARS-CoV-2 infection (if test performed according to local guidelines) in the 2 weeks before the first dose. 21. Other known or suspected causes of Parkinsonism other than idiopathic PD or MSA, including but not limited to, progressive supranuclear gaze palsy, drug- or toxin-induced parkinsonism, essential tremor, primary dystonia, or vascular parkinsonism.