A biomarker is a characteristic that can be measured and evaluated as an indicator of normal biological processes, pathogenetic processes, or pharmacologic responses to a therapeutic intervention. Biomarkers can be divided into two categories:
- Imaging biomarkers: To detect amyloid beta or tau deposits in the brain, to measure metabolic activity, and brain atrophy (shrinkage).
- Biological biomarkers: Such as CSF or blood samples where various forms of amyloid beta or tau protein and other compounds can be detected.
In the context of Alzheimer’s disease (AD), an AD biomarker indicates the presence or progression of the disease that may be altered by drug treatment, thereby demonstrating that it is hitting its target.
Deeper Dive
Clinical trials for Alzheimer’s disease almost all use some form of biomarkers to assess whether the drug is actually affecting the disease in the brain, according to Domenico Praticò, M.D., professor of pharmacology, chair for Alzheimer’s research, and director of the Alzheimer’s Center at Temple University’s School of Medicine in Philadelphia.
Biomarkers measured in the cerebrospinal fluid (CSF) are helpful in making diagnoses, and for predicting who will eventually develop AD. The three core CSF biomarkers currently used for AD diagnostics are the amyloid-beta peptide (Aβ1-42), total tau protein (t-tau), and tau phosphorylated at threonine 181 (p-tau181), according to research published in Alzheimer’s & Dementia: Diagnosis, Assessment & Disease Monitoring.
CSF levels of amyloid beta can indicate amyloid plaques in the brain. Tau protein levels can help detect neurodegeneration and progression of the disease. When combined, these markers can help identify people with Alzheimer’s, predict the shift from normal cognition to mild dementia, and help neurologists monitor the rate of progression from mild to more severe cognitive impairment.