On Friday, the U.S. Food and Drug Administration (FDA) approved a radioactive compound for evaluating people with cognitive impairment for Alzheimer's disease. The drug, called Amyvid, binds to amyloid plaques, the calling card of Alzheimer's disease in the brain. When administered before a PET scan, Amyvid allows doctors to see whether amyloid has begun to build up. A negative test reduces the likelihood that a patient's cognitive problems are due to Alzheimer's, FDA said in its approval letter, but a positive test does not necessarily confirm a diagnosis of Alzheimer's.
The compound was developed by Avid Radiopharmaceuticals, which was acquired by Eli Lilly and Company in 2010. Last year, an FDA panel decided to hold off on approving Amyvid pending more compelling evidence that different doctors would read the scans consistently. Lilly subsequently developed an online training course for neuroradiologists to ensure consistent readings.
Amyvid has been used in research, including clinical trials, for years, says Michael Weiner, a neurologist at the University of California, San Francisco, and principal investigator of the Alzheimer's Disease Neuroimaging Initiative. The compound will be a powerful tool for clinicians when used in combination with other diagnostic tests, Weiner says. But there are potential downsides, too. "There are many concerns: that it could be overused in general, that it could be misused and there will be false diagnoses, both false positives and false negatives," Weiner says. "The medical community is going to have to develop its own standards for how to use it."