Siemens Announces Publication of Research Data Identifying Potential Imaging Agent for Tau Pathologies in Journal of Alzheimer’s Disease

Malvern, Pa., Aug. 22, 2012 – Siemens Healthcare announced today the publication of research data on its [18F]-T808 compound used in positron emission tomography (PET) imaging that selectively targets neurofibrillary tangles (NFTs) of tau protein – a prominent hallmark of Alzheimer’s disease. Siemens Healthcare, which supported the study research in its entirety, is developing the [18F]-labeled compound as a potential PET imaging agent for commercialization. The data appeared in the study “A Highly Selective and Specific PET Tracer for Imaging Tau Pathologies,” published in the August 2012 issue of the Journal of Alzheimer’s Disease.

NFTs of hyperphosphorylated tau protein are one of two critical protein abnormalities associated with Alzheimer’s disease, the other being senile plaques consisting of beta-amyloid peptides. Both protein abnormalities are considered to be targets for therapeutic intervention, in addition to being biomarkers for diagnostic in vivo imaging agents. The severity of tau abnormalities and NFT burden consistently correlates with the degree of cognitive impairment and neuronal circuitry deterioration associated with Alzheimer’s disease dementia, whereas the presence of senile brain plaques lack that correlation. For this reason, NFT can potentially be an additional imaging biomarker for Alzheimer’s-related dementia.

A research team led by Hartmuth C. Kolb, PhD, vice president of Molecular Imaging Biomarker Research at Siemens Healthcare, designed, synthesized, and tested more than 900 compounds in an effort to identify [18F]-PET tracers that possess strong binding affinity and selectivity toward tau protein tangles. Researchers created a competitive autoradiography assay to test compounds that would bind to native tau tangles and beta-amyloid plaques on sections of postmortem human brain tissue. In in vitro assays, the compound [18F]-T808 displayed a high level of binding affinity and good selectivity for tau aggregates over beta-amyloid plaques. The compound demonstrated rapid uptake and washout in rodent brains. The researchers’ in vivo and in vitro studies suggest that [18F]-T808 possesses suitable properties and characteristics to be a specific and selective PET tracer for the imaging of paired helical filament tau in human brains.

“Highly selective and high-affinity tau PET imaging agents are needed to support evaluation and research into potential therapeutic efforts to manage tau-related diseases,” Dr. Kolb said.  “Preclinical characterization of [18F]-T808 demonstrated high levels of binding affinity, selectivity, and specificity, which makes this agent a suitable candidate for further study as a PET tracer for tau aggregate imaging.”

A key issue with Alzheimer’s disease is identifying a biomarker that can be correlated with the progression of clinical symptoms and allow extrapolation back to early preclinical stages. This appears possible in the case of tau deposits. The study’s authors plan to test the [18F]-T808 tracer clinically in Alzheimer’s disease patients to determine its usefulness as an early diagnostic tool of the disease.

About [18F]-T808
[18F]-T808 is the first highly selective and specific PET tracer with potential for in vivo neurological imaging of tau pathologies. It is metabolically stable and has fast uptake and rapid washout period in rodents.
 
About Alzheimer’s Disease
Alzheimer’s disease is a progressive, degenerative disorder that attacks the neurons in the brain, causing behavioral changes and resulting in loss of memory, thinking and language skills, and eventually death. Alzheimer’s disease is the most common cause of dementia among people aged 65 or older. Every 68 seconds a person in the U.S. develops the disease. Deaths from Alzheimer’s disease have increased 66 percent between 2000 and 2008, while deaths from other major diseases – including prostate cancer, breast cancer and the nation’s number-one killer, heart disease – have all decreased during the same period. Many experts predict that with the rise in the aging population, Alzheimer’s disease could be the next health global health epidemic.¹

¹  2012 Alzheimer's Disease Facts & Figures. www.alz.org

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