PET imaging of infection with a HYNIC-conjugated LTB4 antagonist labeled with F-18 via hydrazone formation

It was previously shown that the 99mTc-labeled hydrazinonicotinamide (HYNIC)-conjugated LTB4 antagonist MB81 visualized infectious foci in rabbits adequately and within a few hours after injection. Here, the bivalent HYNIC-conjugated LTB4 antagonist MB67 (analog of MB81) was fluorinated with 18F via hydrazone formation and tested in vivo.MethodsMB67 was [18F]-fluorinated via reaction of the [18F]-fluorinated intermediate p-[18F]-fluorobenzaldehyde ([18F]FB) and the HYNIC moiety of MB67 via hydrazone formation. For comparison, MB67 was also labeled with 99mTc. The biodistribution of 18F- and 99mTc-labeled MB67 was investigated in rabbits with intramuscular infection.Results[18F]-MB67 was obtained at a maximum specific activity of 1200 GBq/mmol and proved to be stable in phosphate buffered saline (PBS) at 37°C for at least 4 h. PET images obtained with [18F]-MB67 clearly delineated the abscess at 2 and 4 h pi. Counting of dissected tissues at 4 h pi revealed an abscess uptake of 0.073±0.005 %ID/g, as compared to 0.160±0.010 %ID/g for the 99mTc-labeled analog. Abscess-to-muscle ratios were 23±4 for [18F]-MB67 and 35±9 for [99mTc]-MB67.ConclusionThe present study showed the feasibility of a new [18F]-labeling methodology and its application in the production of a new PET tracer for imaging of infection, [18F]-MB67.