Using Positron Emission Tomography (PET) Imaging and Pittsburgh Compound-B (PIB) to View Amyloid Deposits
The Alzheimer's Association is very proud to have funded Drs. Klunk and Wang, in part, for this research. It is one of the most important studies published in recent years. The implications of these findings may be enormous for Alzheimer's disease research, specifically, to observe the effects of amyloid-targeting drugs in the brain and perhaps also for efforts to detect Alzheimer's in the early stages.
The findings clearly demonstrate that we now have a tool to detect one of the two, well-known hallmarks of Alzheimer's disease in living patients, that is, amyloid plaques and neurofibrillary tangles. Until now, this could only be done at autopsy or by brain biopsy.
Realistically, this is a small trial. Many more patients need to be studied to confirm and extend these findings. However, the potential repercussions are very wide-ranging.
A powerful tool in anti-amyloid drug development
The ability to detect amyloid in the brains of living people has powerful implications for evaluating therapies to slow, stop or reverse the Alzheimer's disease process.
The buildup in the brain of a sticky protein called amyloid is thought to be a major player in the development of Alzheimer's disease. Companies are right now at work developing anti-amyloid therapies for Alzheimer's. However, it is very hard to tell if these drugs are reaching their targets because none of the currently known biomarkers correlate well with levels of brain amyloid deposition. This is discouraging pharmaceutical CEOs from moving anti-amyloid drugs into very expensive human clinical trials, even though they have already proven effective in animal models.
When PET with PIB – or something like it – is well accepted, it will be more economical to test anti-amyloid therapies and there should be a vast acceleration in the number of anti-amyloid Alzheimer drugs that are brought to clinical trial.
Potential for early detection
Amyloid imaging demonstrates promise as an aid in confirming the diagnosis of people with Alzheimer's disease. More importantly, it may help identify individuals who are at high risk of getting Alzheimer's before symptoms become evident. That's because we now know that changes in the brain associated with Alzheimer's disease may begin 10, 20 even 30 years before there are any outward physical signs or symptoms. This new technology may help us see those changes as they are taking place.
And, combining our two key points, if anti-amyloid therapies are created that are safe and effective, and we can identify at risk individuals before symptoms start, then we will able to intervene early in these individuals to test the notion that we might prevent Alzheimer's symptoms with these drugs.
Challenges remain, however. Many "normal" people have some amyloid in their brains; so it is not obvious that this compound will be absolutely specific for Alzheimer's disease. Nonetheless, to have the powerful new tool and figure out how many different uses there may be for it is still a significant advance.
Editor's Note: In news articles, this statement or excerpts from it can be attributed to William Thies, Ph.D., vice president, Medical & Scientific Affairs, Alzheimer's Association.
"Imaging Brain Amyloid in Alzheimer's Disease Using the Novel Positron Emission Tomography Tracer, Pittsburgh Compound-B," by W.E. Klunk, et al., was chosen for rapid publication online in the early view section of Annals of Neurology.
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