An FDA advisory panel Thursday said it will recommend approval of a new imaging compound that can detect Alzheimer's brain plaques. But the panel added that the chemical in combination with a scan requires additional research to prove its usefulness and reliability in a real-world setting before it's ready for clinical use.
The Food and Drug Administration panel voted 16-0 to recommend approval of Eli Lilly's/Avid's Amyvid, which is currently only used in investigational studies, says the Alzheimer's Association's Maria Carrillo. She says widespread clinical use of the new injectible imaging drug is pending based on the two criteria.
"The FDA wants the company to first take a look at the data and make sure there is reliability in the data analysis. And second, to implement a training program for radiologists and technicians on how they are going to interpret the scan results in order to give a positive or a negative result," says Carrillo, who attended the FDA meeting and gave public testimony during the hearing. The existing data provides a scaled method of interpreting how much plaque exists but doesn't provide a standard cut-off point for what constitutes Alzheimer's.
"The boundary between a positive and negative amyloid scan is unclear," says Scott Turner, director of the Memory Disorders Program at Georgetown University, who is involved in several research studies that use the novel amyloid imaging agent - the first of its kind seeking FDA approval.
The injectible compound works by traveling through the bloodstream and binding with beta-amyloid in the brain. It is used in conjunction with positron emission tomographic (PET) imaging which picks up the highlighted plaques and helps physicians see where they exist in the brain.
"Amyvid may be most useful in identifying individuals with early Alzheimer's disease - for screening and diagnosis," says Turner. He notes that some individuals, especially those over 85 years, can have a lot of plaque buildup even without showing signs of dementia. "And there will be some variability among different readers of the same scan. All of these issues require further research, and the FDA will review this data before making a final decision."
But experts are hopeful that full approval isn't too far off.
"These are relatively easy hurdles to overcome, and theoretically, if those conditions are met and the FDA agrees, then they may grant approval in 2011," Carrillo says.
GE, Bayer, and Astra Zeneca also have similar drugs in the works, says Carrillo.
Duke University Medical Center Alzheimer's expert Murali Doraiswamy, who is also involved in the drug's research, says it will more likely be used to rule out Alzheimer's, rather than diagnose it.
"Many conditions can mimic Alzheimer's - thyroid, vitamin deficiencies, depression, rarer dementias. Knowing someone doesn't have amyloid in the brain can help a clinician focus on those other conditions," Doraiswamy says.
By Mary Brophy Marcus, USA TODAY
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