A Clinical Study of MK-2214 in People With Early Alzheimer's Disease (MK-2214-004)

Researchers want to know if the study treatment called MK-2214 works to slow certain changes in the brains of people with Alzheimer's disease (AD). AD is a type of dementia that can cause loss of memory, communication (such as speech), and decision-making skills. It can limit a person's ability to do daily tasks. MK-2214 is a study treatment designed to slow down AD. The goals of the study are to learn: * If MK-2214 slows the spread of tau in the brain compared to placebo. Tau is a protein that accumulates in AD \& damages brain cells. A placebo looks like the study treatment but has no study treatment in it. Using a placebo helps researchers better understand the effects of a study treatment. * About the safety of MK-2214 and if people tolerate it

Inclusion Criteria: The main inclusion criteria include but are not limited to the following: * Has mild cognitive impairment (MCI) or mild dementia due to Alzheimer's Disease (AD) * Has a designated study partner who can fulfill the requirements of this study * If on an approved AD therapy for symptomatic AD, the dosing regimen must have been stable for 3 months prior to screening Exclusion Criteria: The main exclusion criteria include but are not limited to the following: * Has a known history of stroke or cerebrovascular disease * Has diagnosis of a clinically relevant central nervous system disease other than AD or other condition that negatively impacts cognition or cognitive status chronically * Has structural brain disease * Has a history of seizures or epilepsy within 5 years before screening * Has any other major central nervous system trauma, or infections that affect brain function * Has major medical illness or unstable medical condition within 3 months before screening * Has a severe, acute, or chronic medical or psychiatric condition or laboratory abnormality * Has any immunological disease, which is not adequately controlled, or which requires treatment with biologics and/or immunosuppressants during the study * Has a bleeding disorder that is not under adequate control * Has a history of malignancy occurring within 5 years of screening * Has a risk factor for corrected QT interval (QTc) prolongation * Has liver disease * Is unwilling or unable to undergo computed tomography (CT), positron emission tomography (PET), or magnetic resonance imaging (MRI) scan * Resides in a nursing home or assisted care facility with need for direct continuous medical care and nursing supervision