By Dr Ananya Mandal, MD
A test developed by Eli Lilly that detects the presence of proteins in the brain that are related to Alzheimer's disease was approved Friday by the Food and Drug Administration (FDA).
Using this tool clinicians can now detect Alzheimer's earlier and more accurately in patients at the earliest sign of memory problems. This is a potential boon to treatment and developing drugs against the disease.
The test uses a chemical called florbetapir, known by the brand name Amyvid, which is a radioactive agent that tags clumps of a sticky substance called an amyloid. Amyloid proteins are hallmarks of Alzheimer's disease. The chemical, which costs $1,600 per dose, then is 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.
Dr. Daniel Skovronsky, CEO of Avid, said one in five patients who are diagnosed with Alzheimer’s turn out not to have the disease after an autopsy. “The approval of Amyvid offers physicians a tool that, in conjunction with other diagnostic evaluations, can provide information to help physicians evaluate their patients,” he said in the company’s statement from Friday.
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,” said Skovronsky, who developed the agent and is the global brand-development leader for Amyvid at Lilly. Doctors for these patients can then look for other potential causes of the memory decline, he explained.
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, according to Denise Park, director of the Center for Vital Longevity at the University of Texas at Dallas. “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,” said Dr. Park, a behavioral and brain-sciences professor who uses Amyvid in her research on aging of healthy older adults.