A Study of ONO-2020 in Participants With Mild to Moderate Alzheimer's Disease

Inclusion Criteria:

1. Have a diagnosis of Alzheimer's disease according to the recommendations from therevised criteria for diagnosis and staging of Alzheimer's disease: Alzheimer'sAssociation Workgroup , along with any positive AD-specific biomarker results (abnormal Core 1 or Core 2 biomarkers) from a previous diagnosis or at screening.

2. Have a previous MRI or CT scan of the brain, which was performed within 1 year priorto enrollment in the study, to confirm that more recent neurological events (e.g.,stroke) would not potentially constitute a confounder in the assessment of theetiology of the participant's cognitive status.

3. MMSE score of 15 to 24, inclusive, and MMSE score cannot deviate more than 3 pointsin either direction between the screening and baseline visits.

4. AD numeric clinical stage 4 or stage 5 based on NIA-AA criteria 2024, at screeningand baseline visits

5. Participants receiving concurrent AD treatment (acetylcholinesterase inhibitors and /or memantine) must be on a stable dose for at least 90 days prior to randomization,and the participant must be willing to remain on the same dose for the duration ofthe study.

6. Have the ability to comply with procedures for cognitive and other tests in theopinion of the investigator

7. If female, postmenopausal for at least 1 year

8. Non-vasectomized male participants with female partners of childbearing potentialmust agree to use an effective method of contraception from dosing on Day 1 until 3months after the last administration of study intervention and agree not to donatesperm until 3 months after the last administration of study intervention.

9. Participant must have a Caregiver who has frequent contact with the participant (defined as at least 8 hours per week spread across 3~4 visits per week) to providesupport to the participant to ensure compliance with study requirements. TheCaregiver must be willing to consent to participate in this study, to provide arating of the extent and severity of change of the participant's memory,problem-solving abilities, or activities of daily living from prior abilities.

10. General health status acceptable for participation in the study, and the participantmust be able to ingest pills.

11. Participant and his/her Caregiver have provided full written informed consent priorto the performance of any protocol-specified procedure; or if a participant isunable to provide informed consent due to cognitive status, he/she has providedassent, and a legally acceptable representative (LAR) has provided full writteninformed consent on behalf of the participant.

Exclusion Criteria:

1. Participants with dementia or other memory impairment not due to Alzheimer'sdisease, including, but not limited to, dementia with Lewy bodies, vasculardementia, Parkinson's disease, Huntington disease, corticobasal degeneration,Creutzfeldt-Jakob disease, progressive supranuclear palsy, frontotemporaldegeneration, normal pressure hydrocephalus, hypoxia, severe sleep apnea or otherchronic sleep disturbance, or baseline intellectual disability.

2. Participants with a history of stroke, well-documented transient ischemic attack, orpulmonary or cerebral embolism.

3. History of significant psychiatric illness such as schizophrenia or bipolaraffective disorder, or history or current major depressive disorder in the past yearand any other significant psychiatric illness that in the opinion of theinvestigator could interfere with participation in the study.

4. Participants with delirium or history of delirium within the 30 days prior to thescreening visit.

5. Have suicide ideation according to the investigator's clinical judgment as per theColumbia-Suicide Severity Rating Scale (C-SSRS) at screening or have made a suicideattempt in the 6 months prior to screening.

6. Clinically significant ECG abnormality as judged by the investigator.

7. Confirmed absolute QTcF >450 msec for males or >470 msec for females.

8. Positive results at screening for active viral infections that include humanimmunodeficiency virus (HIV), hepatitis B surface antigen (HBsAg), and hepatitis Cvirus (HCV) RNA PCR test.

9. Participants with total bilirubin, alanine transaminase (ALT) or aspartatetransaminase (AST) greater than 1.5×upper limit of normal (ULN), or internationalnormalized ratio (INR) greater than 1.7 at screening.

10. Participants with estimated creatinine clearance (CrCL, Cockcroft-Gault equation) ≤30 mL/min at screening.

11. Participants with a history of treatment, and/or current treatment, with anti-Aβantibodies

12. Changes in any medications that, in the opinion of the investigator, may potentiallyimpair participants' ability to perform cognitive testing or study procedures duringthe study period (from Screening to EOT), and their dosing should be stable for atleast 1 month before Screening (such as benzodiazepines and sedatives/hypnotics).All concomitant medications must be kept as stable as medically possible during thestudy.

13. Participants who have taken any investigational products, or used investigationalmedical devices, within 3 months or five half-lives of the therapy (whichever islonger) with respect to first dosing and throughout the study