Metabolite analysis of [18F]Florbetaben (BAY 94-9172) in human subjects: a substudy within a proof of mechanism clinical trial

[F-18]Florbetaben ([F-18]BAY 94-9172) is a promising beta-amyloid (A beta) targeted PET-tracer currently in late stage clinical development. [F-18]Florbetaben can assist in the more accurate diagnosis of Alzheimer's Disease (AD) by non-invasive, in vivo detection of A beta in the brain. To determine the arterial input function of the PET tracer-as part of a proof of mechanism (PoM) study-arterial samples were drawn from all subjects at predefined time points post injection (p.i.), and the proportion of unchanged tracer [F-18]Florbetaben was determined by HPLC analysis. Plasma metabolite profiles were investigated following intravenous administration of 300 MBq (+/- 60 MBq) of [F-18]Florbetaben to both, patients with AD and healthy controls (HCs), and various methods for processing the blood samples were evaluated. Addition of acetonitrile to plasma samples (obtained from whole blood by centrifugation) and precipitation of proteins resulted in a recovery of more than 90% of the initial radioactivity in the supernatants. High Performance Liquid Chromatography using a polymer-based column (PRP-1) in conjunction with gradient elution was found to be a suitable method of metabolite analysis of [F-18]Florbetaben. HPLC analyses indicated that [F-18]Florbetaben is rapidly metabolized in vivo with an estimated initial half-life of about 6 min. A polar metabolite fraction, consisting presumably of more than one component, and (to a smaller extent) of the demethylated derivative of [F-18]Florbetaben were time-dependently detected in plasma.