Three Amyloid Tracers in Development

Just because you can detect brain amyloid, doesn't necessarily mean that you should—at least not in clinical practice.

But that word of caution isn't stopping 3 companies from pushing forward with their late-phase development of radiolabeled* tracers for the protein—which is a pathologic signature for Alzheimer disease but is also seen, importantly, in a substantial chunk of cognitively normal elderly.

Who are we kidding? Reflection is not the bailiwick of industry.

The furthest along is Avid/Lilly's florbetapir (Amyvid), which has been the subject of many a critical post at this blog. Last word is that the company is working with the FDA to establish a reader-training program, an agency requirement for approval.

GE's flutemetamol is in phase 3 development, according to entries at clinicaltrials.gov, and the company is promoting at the current ICAD meeting 1) the tracer's comparability to the reference standard of amyloid-imaging agents, Pittsburgh compound B, and 2) the success of its own reader-training program.

Bayer's tracer, florbetaben, is just entering phase 3 study, but the compound may be the easiest to use in practice (notwithstanding the issue of knowing what to do with the results), because PET imaging may be performed up to 130 minutes after the tracer is injected.

For a recent review of the 3 amyloid-detecting compounds, see a comprehensive write-up in July's Lancet Neurology.

ICAD = International Conference on Alzheimer's Disease.

* All use 18F, which has a substantially longer half-life than the 11C-labeled Pittsburgh compound B, the reference standard for amyloid imaging. The longer, 18F-labeled amyloid tracers were developed because the short-lived Pittsburgh compound requires an on-site cyclotron. The longer-acting tracers mean that the compound can be administered and then the patient transported (if necessary) to a PET-imaging center.

Photograph: Atrophied brain from person with AD from National Institute on Alcohol Abuse and Alcoholism.