Florbetaben ¹⁸F Other names: Florbetaben F-18

Florbetaben F18 is a F18-labeled stilbene derivative, which binds to β-amyloid plaques in the brain. The F18 isotope produces a positron signal that is detected by a PET scanner. ³H-florbetaben in vitro binding experiments reveal two binding sites (Kd of 16 nM and 135 nM) in frontal cortex homogenates from patients with AD. Binding of florbetaben F18 to β-amyloid plaques in post-mortem brain sections from patients with AD using autoradiography correlates with both immunohistochemical and Bielschowsky silver stains. Florbetaben F18 does not bind to tau or α-synuclein in tissue from patients with AD. Neither florbetaben F18 nor non-radioactive florbetaben F19 bind to AT8 positive tau deposits in brain tissue from patients with frontotemporal dementia (FTD), using autoradiography and immunohistochemistry, respectively.

Following intravenous administration, florbetaben F18 crosses the blood brain barrier and shows differential retention in brain regions that contain β-amyloid deposits. Differences in signal intensity between brain regions showing specific and non-specific florbetaben F18 uptake form the basis for the image interpretation method.

Ten minutes after intravenous bolus injection of 300 MBq of florbetaben F18 in human volunteers, approximately 6% of the injected radioactivity was distributed to the brain. Florbetaben F18 plasma concentrations declined by approximately 75% at 20 minutes post-injection, and by approximately 90% at 50 minutes. The F18 in circulation during the 45-130 minute imaging window was principally associated with polar metabolites of florbetaben. Florbetaben F18 was 98.5% bound to plasma proteins and was eliminated from plasma primarily via the hepatobiliary route with a mean biological half-life of approximately 1 hour. In vitro studies show that metabolism of florbetaben is predominantly catalyzed by CYP2J2 and CYP4F2. At 12 hours post-administration, approximately 30% of the injected radioactivity had been excreted in urine. Almost all F18 radioactivity in urine was excreted as polar metabolites of florbetaben F18 and only trace amounts of florbetaben F18 were detected.

In in vitro studies using human liver microsomes, florbetaben did not inhibit cytochrome P450 enzymes at concentrations present in vivo.