A much-anticipated test developed by Eli Lilly that detects the presence of proteins in the brain that are related to Alzheimer's disease was approved by the US Food and Drug Administration.
This test could enable clinicians to detect Alzheimer's earlier and more accurately in patients at the earliest sign of memory problems -- a potential boon to treatment and developing drugs against the disease.
The test uses a chemical known by the brand name Amyvid, a radioactive agent that tags clumps of a sticky substance called an amyloid. Amyloid proteins are hallmarks of Alzheimer's disease. The chemical is then detected using a brain imaging technique called positron emission tomography, known as PET scans.
For patients who already have some symptoms of cognitive decline, a positive scan suggests that moderate to frequent amyloid plaques are present in the brain, which is consistent with Alzheimer's disease.
If the scan is negative, indicating no clumps or few clumps of amyloid, "that gives the clinician a clue that Alzheimer's is less likely to be the cause of those symptoms," according to Daniel Skovronsky, who developed the agent at Lilly. For those patients, doctors can look for other potential causes of the memory decline, which may have another prognosis or be treated differentially than Alzheimer's.
The imaging agent cannot be used to diagnose someone with Alzheimer's disease if the individual does not experience memory impairment because the presence of amyloid in the brain does not alone suggest that someone has Alzheimer's.
Before the development of imaging agents, amyloid plaques could be determined only after death, by examining the brain during an autopsy.
Some 20% of cognitively healthy older adults have been found during autopsies to have large quantities of amyloid in the brain.
"It is likely to play an important role in learning both how to diagnose and treat the disease, but it's still an open question at this point for asymptomatic people," according to Park, a behavioral and brain-sciences professor who uses Amyvid in her research on aging of healthy older adults.
Amyvid will be available in limited quantities starting in June after being approved Friday, Lilly said.
Wall Street Journal