Meeting on January 20th, the Peripheral and Central Nervous System Drugs Advisory Committee of the FDA met to discuss potential approval for Amyvid, a novel radiotracer used to image beta amyloid plaque in the brain. Manufactured by Eli Lilly, Amyvid (florbetapir) is a PET radiotracer which binds to beta amyloid plaque, identified as an indicator of the progression of Alzheimer's disease. The Committee voted not to fully approve the new radiotracer, but rather, to give conditional approval should the manufacturer provide a sufficient training program for readers. Previous studies demonstrated significant variation in readers' ability to extract and interpret data, resulting in a high false-positive rate. The FDA is not calling for more research trials, but rather, that once a training program has been developed, the FDA will likely approve the radiotracer.
To date, the use of PET for neuroimaging has previously been challenging due to the lack of brain-specific radiotracers given existing limitations of using FDG-glucose. High metabolism in the brain renders standard glucose-based imaging unreliable, and PET has thus far been used primarily for oncologic imaging. Amyvid avoids this setback by binding directly to beta amyloid plaque, rather than tracking a specific metabolic process. While Amyvid will not likely be able to definitively diagnose Alzheimer's disease, it can confidently rule it out in favor of other neurodegenerative disorders.
While the availability of Amyvid marks an important step in the evolution of PET imaging to assess myriad neurodegenerative diseases, there is still uncertainty within the medical field regarding the value of detecting precursors to Alzheimer's disease. Without a valid treatment plan, questions remain as to the anxiety placed on the patient and their family in knowing that Alzheimer's is potentially impending. Confidently ruling out Alzheimer's can redirect physician attention to other diseases but detection of beta amyloid plaque does not always indicate Alzheimer's will be present. However, conditional approval of Amyvid and more widespread use of the neuro PET imaging agent can help to further answer these questions and determine an appropriate course of action.