17,18 Fludeoxyglucose (FDG)-positron emission tomography (PET) scans, where blood flow and glucose utilization over different brain regions can be measured, may also provide useful information as to disease progression over time.19 Further, methods are improving to image amyloid plaques in
living patients using PET ligands that bind Aβ.20 These methods have been used to measure significant changes in amyloid deposition in patients with MCI.21 The most promising of these neuroimaging techniques and biochemical readouts could in time be used together as Dabrafenib mouse surrogate markers to provide an accurate assessment of disease state over time within Inhibitors,research,lifescience,medical an individual or across a population. There is a risk, however, of focusing too heavily on surrogate markers. In studies of rosiglitizone for diabetes, negative outcomes on disease appeared despite expected positive effects on the surrogate.22 Cholesterol has long been used as a surrogate for heart disease; however, in clinical Inhibitors,research,lifescience,medical trials of high-density lipoprotein-modifying drugs (such as torceptrabib) for prevention of heart disease, a positive effect on the surrogate was seen even though clinical outcomes were Inhibitors,research,lifescience,medical worsened.23 As in AD, these other chronic degenerative diseases have complex, multifactorial causes that are not necessarily reflected in the surrogate marker. Therefore, while using surrogate markers can be quite a meaningful
method to monitor aspects of disease progression, it is crucial to keep in mind the limitations of this approach. Understanding genetic risk factors for AD is another
method to facilitate early detection of high-risk individuals, while also providing insight into disease mechanisms. The discovery Inhibitors,research,lifescience,medical of genes underlying risk for AD has provided us with many of our most promising drug targets. Individuals with the apolipoprotein E4 allele (ApoE4), for example, have a significantly greater risk Inhibitors,research,lifescience,medical of developing Alzheimer’s disease, and often exhibit an earlier age of onset and a more aggressive form of the disease.24’1 While ApoE4 is a known risk factor for AD, we still do not fully understand its mechanism of function in AD pathogenesis. Identifying genetic subtypes of AD could allow for the development of more individualized therapies, as well as aid in clinical trial design for novel drug therapies. In fact, in the Phase II trial for Bapineuzumab, a monoclonal Rolziracetam antibody to β-amyloid developed by Wyeth and Elan, ApoE4 carriers were separated from noncarriers in the analysis. Only noncarriers demonstrated a significant benefit from the treatment, which would not have been detected had the population been analyzed as a whole.25 It is our hope that in the near future early detection techniques, such as measurements of Aβ load, neuroimaging analysis, and/or genetic testing will function much like cholesterol testing does for heart disease.