Inclusion Criteria:
1. Must meet the 2024 diagnostic criteria for Alzheimer's disease (AD) published by the Alzheimer's Association (AA), and be in the moderate stage of AD.
2. The Clinical Dementia Rating-Sum of Boxes (CDR-SB) score must be between 9.5 and 15.5.
3. Aged 55-80 years.
4. Must be receiving treatment with stable doses of acetylcholinesterase inhibitors, memantine, or both for at least 3 months prior to the screening visit.
5. Have a study partner who will provide written informed consent to participate, is in frequent contact with the participant (defined as at least 10 hours per week), and will accompany the participant to study visits or be available by telephone at designated times.
6. Have adequate literacy, vision, and hearing for neuropsychological testing in the opinion of the investigator at the time of screening.
Exclusion Criteria:
1. Has diagnosis of a clinically relevant central nervous system (CNS) disease other than AD dementia or other condition that negatively impacts cognition or cognitive status chronically.
2. Contraindications to MRI (e.g., metal implants) or inability to tolerate/comply with the scanning procedure.
3. Prior exposure to ozanimod or any other sphingosine-1-phosphate receptor regulators for AD before starting treatment with ozanimod subject of this study
4. Participants must not have clinically relevant hepatic, neurological, pulmonary, ophthalmological, endocrine, renal, infectious diseases, or other major systemic disease making implementation of the protocol or interpretation of the study results difficult or that would put the participant at risk by participating in the study in the opinion of the Investigator.
5. Specific cardiac conditions are excluded, including history or presence of:
i) Recent (within the past 6 months) occurrence of myocardial infarction, unstable angina, stroke, transient ischemic attack, decompensated heart failure requiring hospitalization, New York Heart Association (NYHA) Class III/IV heart failure, or severe untreated sleep apnea.
ii) Resting heart rate \<55 beats per minute, second-degree (Mobitz type II) atrioventricular (AV) block, third-degree AV block, sick sinus syndrome, or sino-atrial block unless participants have a pacemaker in place.
iii) Prolonged corrected QT interval by Fredericia's formula (QTcF; \> 450 msec males and \> 470 msec females), or participants at additional risk for QT prolongation.
6. Participants must not receive a live vaccine or a live-attenuated vaccine within 4 weeks prior to first dose or planning to receive a live vaccine or a live-attenuated vaccine during the study or within 90 days after discontinuation from study intervention.
7. Participants must not have a history of any significant drug allergy (such as anaphylaxis or hepatotoxicity).
