Test Quickly Assesses Whether Alzheimer's Drugs Are Hitting Their Target
April 17, 2009
Adapted from Washington University
A test developed by physician-scientists at Washington University School of Medicine in St. Louis may help assess more quickly the ability of Alzheimer's drugs to affect one of the possible underlying causes of Alzheimer's disease in humans, accelerating the development of new treatments.
Scientists used the test to show that an Alzheimer's drug given to healthy volunteers reduced production of a substance known as amyloid beta (A-beta), a normal byproduct of human metabolism that builds to unhealthy levels forming brain plaques in Alzheimer's patients. The drug candidate, LY450139, which is also known as semagacestat, is being studied in clinical trials by Eli Lilly and Company.
Ongoing clinical trials are studying the effect that semagacestat may have on cognitive function and biochemical and brain imaging biomarkers in patients with Alzheimer's disease. Washington University researchers wanted to see whether the new measurement technique, stable isotope-linked kinetics (SILK), could detect the study drug's impact on A-beta synthesis in healthy volunteers.
"Bringing an Alzheimer's disease drug into clinical trials from tests in animal models has always been challenging," says study director Randall Bateman, M.D., a Washington University neurologist who treats patients at Barnes-Jewish Hospital. "We haven't had a way to quickly and accurately assess a drug's effects, and that meant there always had to be some degree of educated guesswork when it came to setting the optimal dosage for humans. SILK may help to eliminate much of that guesswork."
Scientists are unsure whether increased A-beta production, reduced clearance or a combination of the two lead to the A-beta buildup in the brain, a process that many believe triggers Alzheimer's disease. Bateman and his colleagues are currently using SILK to try to answer this question.
The SILK procedure takes 36 hours, but provides scientists a more detailed assessment of amyloid beta production and clearance levels than they can obtain through conventional methods.
"You could use a spinal tap to look directly at the amount of A-beta present in the cerebrospinal fluid, but we've shown that natural processes cause A-beta levels to change dynamically," says Bateman. "Such changes make it more difficult to assess the effects of a drug in that fashion."
Though this study was not funded by the BrightFocus Foundation, Dr. Bateman is supported for other related projects through the BrightFocus Alzheimer's Disease Research program. These ongoing projects are to understand how a key genetic risk factor for Alzheimer's disease, Apolipoprotein E, is processed and cleared from the central nervous system.
The results appear online in Annals of Neurology on April 10.
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