<br>        Inclusion Criteria:<br><br>          -  Participant must meet the National Institute on Aging (NIA) and the Alzheimer's<br>             Association (AA) (NIA-AA) criteria for probable AD dementia.<br><br>          -  MMSE score of 20 to 26 inclusive at screening visit.<br><br>          -  For a diagnosis of mild AD dementia, participant must have a CDR global score of 0.5<br>             or 1, with the memory box score =0.5 at screening.<br><br>          -  Evidence of amyloid pathology.<br><br>          -  The participant must have a reliable study partner with whom he/she cohabits or has<br>             regular contact.<br><br>        Exclusion Criteria:<br><br>          -  Significant and/or current neurological disease affecting the central nervous system,<br>             other than AD, that may affect cognition or ability to complete the study, including<br>             but not limited to, other dementias, repetitive head trauma, serious infection of the<br>             brain, Parkinson's disease, epilepsy, or cervicocranial vascular disease.<br><br>          -  Participants with any current primary psychiatric diagnosis other than AD if, in the<br>             judgment of the investigator, the psychiatric disorder or symptom is likely to<br>             confound interpretation of drug effect, affect cognitive assessment, or affect the<br>             participant's ability to complete the study. Participants with history of<br>             schizophrenia or other chronic psychosis are excluded.<br><br>          -  Within 1 year before the screening visit or between screening and randomization, any<br>             of the following: myocardial infarction; moderate or severe congestive heart failure,<br>             New York Heart Association class III or IV; hospitalization for, or symptoms of,<br>             unstable angina; syncope due to orthostatic hypotension or unexplained syncope; known<br>             significant structural heart disease (such as, significant valvular disease,<br>             hypertrophic cardiomyopathy); or hospitalization for arrhythmia.<br><br>          -  Congenital QT prolongation.<br><br>          -  Intermittent second- or third-degree atrioventricular (AV) heart block or AV<br>             dissociation or history of ventricular tachycardia.<br><br>          -  A corrected QT (QTcF) interval measurement >470 milliseconds (men and women) at<br>             screening (as determined at the investigational site).<br><br>          -  History of malignant cancer within the last 5 years.<br><br>          -  History of vitiligo and/or current evidence of post-inflammatory hypopigmentation.<br><br>          -  Calculated creatinine clearance <30 milliliters per minute (Cockcroft-Gault formula;<br>             Cockcroft and Gault 1976) at screening.<br><br>          -  Currently enrolled in any other clinical trial involving an investigational product or<br>             any other type of medical research judged not to be scientifically or medically<br>             compatible with this study.<br>