Neuro Trials

Any neurological condition that may be contributing to cognitive impairment above and beyond that caused by the participant's Alzheimer's disease

History of transient ischemic attacks (TIA), stroke, or seizures within 12 months of Screening

Any psychiatric diagnosis or symptoms (example, hallucinations, major depression, or delusions) that could interfere with study procedures in the participant

Geriatric Depression Scale (GDS) score >=8 at Screening

Contraindications to MRI scanning, including cardiac pacemaker/defibrillator, ferromagnetic metal implants (example in skull and cardiac devices other than those approved as safe for use in MRI scanners)

Evidence of other clinically significant lesions on brain MRI at Screening that could indicate a dementia diagnosis other than Alzheimer's disease

Other significant pathological findings on brain MRI at screening, including but not limited to: more than 4 microhemorrhages (defined as 10 millimeter [mm] or less at the greatest diameter); a single macrohemorrhage >10 mm at greatest diameter; an area of superficial siderosis; evidence of vasogenic edema; evidence of cerebral contusion, encephalomalacia, aneurysms, vascular malformations, or infective lesions; evidence of multiple lacunar infarcts or stroke involving a major vascular territory, severe small vessel, or white matter disease; space occupying lesions; or brain tumors (however, lesions diagnosed as meningiomas or arachnoid cysts and <1 centimeter [cm] at their greatest diameter need not be exclusionary)

Any immunological disease which is not adequately controlled, or which requires treatment with immunoglobulins, systemic monoclonal antibodies (or derivatives of monoclonal antibodies), systemic immunosuppressants, or plasmapheresis during the study

inadequately controlled bleeding disorder (including a platelet count <50,000 or international normalized ratio [INR] >1.5 for participants who are not on anticoagulant treatment, example, warfarin). Participants who are on anticoagulant therapy should have their anticoagulant status optimized and be on a stable dose for 4 weeks before Screening. Participants who are on anticoagulant therapy are not permitted to participate in cerebrospinal fluid (CSF) assessments

Uncontrolled comorbidities including cardiac, respiratory, gastrointestinal, renal disease

Participation in a clinical study involving any therapeutic monoclonal antibody, immunoglobulin therapy, or vaccine within 6 months Participation in a clinical study involving any anti-amyloid therapies known prior exposure to lecanemab

involved any new chemical entities for AD within 6 months prior to screening