The Use of Biomarkers and PET in Early Alzheimer’s Disease Diagnosis

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The Use of Imaging Biomarkers and Positron Emission Tomography to Diagnose Early Alzheimer’s Disease

Colin G. Miller, PhD FICR CSci
Alzheimer’s disease (AD) is the most common form of dementia and is incurable, degenerative and irreversible.  It affects around 4.5 million people in the United States, a number that is expected to exceed 12 million by 2050.  Neuropsychological tests, such as the mini-mental state examination (MMSE), are commonly used to diagnose patients. However, cognitive impairment may be due to another disease, not Alzheimer’s.  There remains an unmet need to be able to differentiate between different forms of dementia.

Imaging biomarkers are providing new diagnostic tools. One of the seminal biomarkers for Alzheimer’s disease is Pittsburgh compound B (PiB).  PiB is a fluorescent analog of thioflavin T; it is used in combination with Positron Emission Tomography (PET) scans to image beta-amyloid plaques in the brains of Alzheimer’s disease patients (more information here). Beta-amyloid has been proven to be a hallmark of Alzheimer’s disease and is accumulated in the brain in the very early course of the disease (more information here).

Recent PiB PET studies Recent PiB PET studies have shown that they can improve the accuracy of dementia diagnosis in early stages of the disease by measuring disease-related amyloid accumulation.

Source:  Society of Nuclear Medicine, 2009 Press Conference on Scientific Paper 251, “PET Neurochemical vs. Clinical Phenotypes in Mild-Early Dementia.” (see PowerPoint document for reference)

Companies are now developing imaging biomarkers for Alzheimer’s disease diagnosis.  Bayer has florbetaben (BAY 94-9172), an 18F radiolabeled tracer that binds to beta-amyloid in phase III clinical trials.  Avid Radiopharmaceuticals is a company purely focused on new imaging biomarkers with AV-45 in Phase III development.

Presuming that florbetaben or AV-45 ends up being approved, it will be interesting to see what price the respective companies charges for these injectable tracers.  Not only do imaging biomarkers have to work, they have to be cost-effective in today’s healthcare environment.

What are your thoughts on using biomarkers and PET in early diagnosis of Alzheimer’s disease?

Sources:

1. http://www.ncbi.nlm.nih.gov/pubmed/14991808
2. http://www.ncbi.nlm.nih.gov/pubmed/16854944
3. http://www.snm.org/index.cfm?PageID=8779&RPID=8729
4. http://clinicaltrials.gov/ct2/show/NCT01020838