A Study of Potential Disease Modifying Treatments in Individuals at Risk for or With a Type of Early Onset AD Caused by a Genetic Mutation

This study will recruit participants from the Dominantly Inherited Alzheimer Network observational study (DIAN-OBS), a multicenter international study supported by the National Institutes of Health (Grant Number U01-AG032438; RJ Bateman), Dominantly Inherited Alzheimer Network Trials Unit (DIAN-TU) sites, DIAN-TU partner sites, DIAN Expanded Registry (DIAN-EXR), and families identified by the sites. As part of the DIAN-TU-002 protocol, participants undergo longitudinal assessments that include clinical assessment, cognitive testing, magnetic resonance imaging (MRI) and amyloid imaging, and analysis of cerebrospinal fluid (CSF).

Participants in DIAN are recruited from families that have at least one member who has been identified as having a mutation linked to dominantly inherited Alzheimer's disease (DIAD). The mutations in presenilin 1 (PSEN1), presenilin 2 (PSEN2) and amyloid precursor protein (APP) genes that are associated with DIAD have very high penetrance (near 100%). This study will enroll individuals who are either known to have a known disease-causing mutation, or who are at risk for such a mutation (the child or sibling of a proband with a known mutation) and unaware of their genetic status. Because the age at onset of cognitive changes is relatively consistent within each family and for each mutation, an age at onset is determined for each affected parent or mutation as part of the DIAN-OBS study protocol. This study will enroll participants who are asymptomatic and are within a specific window of time of expected age at onset for their family and/or mutation.

The ability to identify individuals destined to develop Alzheimer's disease (AD) with a high degree of confidence provides a unique opportunity to assess the efficacy of therapies at asymptomatic and very early stages of dementia. Families with known disease-causing mutations are extremely rare and are geographically dispersed throughout the world. These constraints necessitate a specialized study design. Participants in this study will not yet have developed any symptoms of AD; they will be "asymptomatic" carriers of mutations that cause DIAD and would be expected to perform normally on standard cognitive and functional testing. Further, most mutation carriers will have levels of AD-associated amyloid beta (Aβ) and non-Aβ biomarkers that are the same as non-carriers. Imaging and fluid biomarkers will be used to demonstrate that the treatment compounds have engaged their therapeutic targets. A set of cognitive measures designed to assess the very earliest and most subtle cognitive changes will be collected. However, the goal of this study is to address whether decreasing plaque prone Aβ peptides in the absence of measurable or mild elevations of Aβ plaques in participants with minimal to no amyloid plaque at baseline can lead to the subsequent prevention of non-Aβ biomarkers of disease progression. Additionally, because many at-risk individuals decide not to know whether they have the disease-associated mutation, some of the at-risk individuals enrolled in this study will not have the disease-causing mutations; they will be "mutation-negative." It is important to enroll these participants to avoid coercion (e.g., potential participants may feel pressured into genetic testing to learn their genetic status to be eligible for the trial). These mutation-negative individuals will be assigned to the placebo group and data will be used to determine normal ranges of outcome. Participants and site study staff will remain blinded as to these individuals' active or placebo group assignment and mutation status. Thus, the study will be blinded for placebo and for mutation status, except for mutation carriers who are aware of their genetic status. There may be exceptional circumstances as required by local regulation or health authorities where enrollment may be restricted to mutation carriers only, but such mandates will be thoroughly documented and agreed upon by the governing regulatory agency and the study sponsor.