By Susan Heavey
SILVER SPRING, Maryland (Reuters) - U.S. advisers have rejected an Eli Lilly & Co imaging agent, saying more data is needed before the drug can be approved for helping doctors rule out the presence of plaque linked to Alzheimer's disease.
The move by the Food and Drug Administration's outside advisers on Thursday is a set-back for what has been one of the most promising imaging tests in helping researchers and physicians and patients grappling with the most common form of dementia.
FDA's advisory panel unanimously said the radioactive dye, called Amyvid, appears to help detect brain plaques associated with the memory disease but that more data is needed first to show the scans can be properly read and interpreted.
"The information is useful, and I do think it has clinical utility," said panel chairman Dr. Britt Anderson, a psychology professor at the University of Waterloo. "But for me it's a problem that the readings thus far are significantly inconsistent."
Lilly is seeking FDA approval to market the agent, called Amyvid, for use with positron emission tomography, or PET, scans to help doctors rule out the plaque linked with Alzheimer's, but not to diagnose the disease.
The FDA will weigh the panel's advice in making its approval decision, which Lilly expects in the first half of 2011.
The drugmaker has been ahead in the race for such imaging agents that are estimated to have a potential global market anywhere from $1 billion to $5 billion. It acquired the drug, known chemically as florbetapir F 18, through its recent purchase of Avid Radiopharmaceuticals Inc.
General Electric Co and Bayer AG are also developing rival products.
"We don't intend this as a screening tool," Avid's Chief Executive Dr. Daniel Skovronsky told the panel. "It's simply another tool that physicians can add to their armamentarium to tell them one more thing about what's going on with a patient."
In a statement released after the meeting, Skovronsky said the company "was encouraged that (the panel) recommended a clear path toward approval."
New tests for Alzheimer's have raised numerous questions since there is no cure for the disease, which government statistics show affects anywhere from 2.4 million to more than 5 million Americans mostly over the age of 65.
The market is expected to expand as more Americans live longer and the so-called "Baby Boomer" generation ages.
While such brain scans can help researchers, of particular concern is how useful they are for doctors and patients, especially since the clumps of brain protein and tangles can occur years before symptoms arise.
At the meeting, FDA staff raised concerns about whether technicians will be able to properly read and interpret the scan images for routine clinical use and have proper training to do so. They also questioned the usefulness of the imaging tests if interpretation of the scans can vary so widely.
"Our biggest concern is the implementation process," Dr. Rafel Dwaine Rieves, who oversees the FDA's Division of Medical Imaging Products.
Panel members overwhelmingly agreed and said the drug could merit approval if data could show training would help technicians consistently review brain images using the dye.
Several patient advocacy groups at the meeting called on the FDA to back the dye, with some noting it could be especially useful for researchers looking to find better treatments for the disease.
Maria Carrillo of the Alzheimer's Association, who spoke at the panel meeting, said the committee was concerned the data would be misinterpreted by doctors and patients, and they asked the company to reassess their data to provide a clearer answer about whether the scan was positive or negative.
And, the company needs to provide training protocols for radiologists on how best to read the scans.
"It won't take them very long. If that is done I think the FDA will lean toward approval," Carrillo said.
If approved, she said the scans would give doctors a better way of assessing whether a patient has amyloid deposits in the brain. If the test is positive, a patient might be a good candidate for clinical trial, she said.
Avid already has made the agent available to various government and pharmaceutical companies for their studies, but FDA approval could make it more widely available.
(Reporting by Susan Heavey; Additional reporting by Julie Steenhuysen in Chicago and Lisa Richwine in Washington; Editing by Tim Dobbyn and Carol Bishopric)