PET scan reveals the presence of beta-amyloid protein in red and yellow areas of this brain. Image Source: Discover Magazine

GE Healthcare, Bayer Healthcare Pharmaceuticals and Avid Radiopharmaceuticals met Thursday with an FDA advisory panel to discuss the development of new imaging markers, which could aid in the diagnosis of Alzheimer’s disease (AD).

The advisory committee meeting was aimed at providing specific recommendations based on clinical utility towards the design of phase III diagnostic imaging studies in AD.

The agents, which would be used in combination with PET scans, are designed to essentially light up areas of the brain that contain amyloid on imaging scans, but so far none are FDA approved, according to the Wall Street Journal (WSJ). Beta-amyloid is a protein contained in clumps or plaques seen in the brains of people who have died of Alzheimer's complications.

New agents in development, with an approximate half-life of two-hours, hope to be indicated for PET imaging of amyloid plaque pathology in the brain to aid in the evaluation of patients with signs or symptoms of cognitive impairment. They could also be used to monitor patient response to disease modifying drugs in development.

Bayer, GE and Avid have developed imaging agents designed to show amyloid on PET scans. The companies said that the scans could be used as a diagnosing tool in Alzheimer's disease, or at least ruling it out if amyloid is not detected, and have asked the FDA for advice in developing clinical studies needed to get the agents approved, WSJ reported.

Rafel Rieves, FDA's office of medical imaging director, told WSJ that the agency wants to come up with guidelines for companies to follow to conduct clinical trials. FDA approval and commercial use of the agents is a few years away because none of the proposed studies have begun.

“This is potentially a powerful tool ...but it's going to require a lot more research,” Larry Goldstein, the panel's acting chairman and a professor of medicine at Duke University Medical Center in Durham, N.C., told the WSJ. He added that the agents could be a useful tool for drug companies who are developing drugs to attack amyloid.

The FDA panel said clinical trials looking at amyloid imaging agents that would be used with the PET scans need to contain a component that involves an examination of brains of Alzheimer's patients after death.

“Prior to this meeting, there were two major unanswered questions that could have impeded the further development of amyloid imaging. The FDA Advisory Committee today tackled both the issues of defining the clinical utility and of selecting the appropriate reference standard, thereby addressing these major obstacles to late stage development of amyloid imaging,” said Michael Weiner, MD, professor of radiology at the VA Medical Center, University of California San Francisco and the principal investigator of the Alzheimer’s Disease Neuroimaging Initiative.