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

Abstract It was previously shown that the99m Tc-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 with18 F via hydrazone formation and tested in vivo. Methods MB67 was [18 F]-fluorinated via reaction of the [18 F]-fluorinated intermediate p -[18 F]-fluorobenzaldehyde ([18 F]FB) and the HYNIC moiety of MB67 via hydrazone formation. For comparison, MB67 was also labeled with99m Tc. The biodistribution of18 F- and99m Tc-labeled MB67 was investigated in rabbits with intramuscular infection. Results [18 F]-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 [18 F]-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 the99m Tc-labeled analog. Abscess-to-muscle ratios were 23±4 for [18 F]-MB67 and 35±9 for [99m Tc]-MB67. Conclusion The present study showed the feasibility of a new [18 F]-labeling methodology and its application in the production of a new PET tracer for imaging of infection, [18 F]-MB67.