A new imaging agent may revolutionize Alzheimer’s detection and treatment.
The brain guards its secrets well. Encased in the skull and protected by the blood-brain barrier (a membrane that filters out many substances), it resists some of the scanning techniques that have illuminated the heart and other organs. But recent advances in brain imaging are now offering scientists remarkable new views of the brain.
Until recently, an autopsy was the only way to confirm a diagnosis of Alzheimer’s disease. Only by directly examining the brain after death could researchers identify one of the telltale signatures of Alzheimer’s -- deposits of a sticky protein called beta-amyloid (also known as amyloid plaque). Amyloid plaques are not visible through conventional brain scanning techniques.
The inability to see beta-amyloid deposits in the living brain has been a serious limitation that forced doctors to rely on symptoms and cognitive tests to make a diagnosis of Alzheimer’s disease. Moreover, research and treatment were stymied by not knowing how early in life the Alzheimer‘s process begins, which brain structures are affected first, and how quickly Alzheimer‘s progresses through the brain. In addition, the inability to see the amyloid plaques meant that drug developers had no way to tell if their experimental agents were actually working to clear plaques from the brain in an Alzheimer’s patient.
That may be changing with the advent of a new imaging agent called Pittsburgh Compound B (PIB). Developed by researchers at the University of Pittsburgh, PIB slips past the blood-brain barrier and binds to amyloid plaques. Used with positron emission tomography (PET), PIB “lights up” the amyloid deposits, offering researchers their first look at amyloid plaques in the living brain. Another compound that binds to amyloid plaques, developed by scientists at UCLA, is at an earlier stage of development but is also promising.
Although the use of PET/PIB is in its earliest stages, the potential implications are immense. If further testing confirms its diagnostic ability, the technique may allow doctors to detect the beginnings of Alzheimer’s disease years, or even decades, before Alzheimer’s symptoms develop. That, in turn, would provide the opportunity to intervene early, when Alzheimer’s medications should be most effective. Moreover, having a visible "target” to use in evaluating experimental therapies would spur new drug research and development.
