 This study will assess the effects of each of the two therapies given separately, both targeting amyloid, on cognition, global clinical status, and underlying pathology in participants at risk for the onset of clinical symptoms of Alzheimers disease AD. Cognitively unimpaired individuals with two APOE4 genes and age 60 to 75 years, inclusive, are selected as they represent a population at particularly high risk of progression to Mild Cognitive Impairment andor dementia due to Alzheimers disease. 