Oxime coupling of active site inhibited factor seven with a non-volatile, water soluble fluorine-18 labelled aldehyde.

A nonvolatile fluorine-18 aldehyde prosthetic group was developed from [F-18]SFB, and used for site-specific labeling of active site inhibited factor VII (FVHai). FVIIai has a high affinity for tissue factor (TF), a transmembrane protein involved in angiogenesis, proliferation, cell migration, and survival of cancer cells. A hydroxylamine N-glycan modified FVIIai (FVIIai-ONH2) was used for oxime coupling with the aldehyde [F-18]2 under mild and optimized conditions in an isolated RCY of 4.7 +/- 0.9%, and a synthesis time of 267 +/- 5 min (from EOB). Retained binding and specificity of the resulting [F-18]FVIIai to TF was shown in vitro. TF-expression imaging capability was evaluated by in vivo PET/CT imaging in a pancreatic human xenograft cancer mouse model. The conjugate showed exceptional stability in plasma (>95% at 4 h) and a binding fraction of 90%. In vivo PET/CT imaging showed a mean tumor uptake of 3.8 +/- 0.2% ID/g at 4 h post-injection, a comparable uptake in liver and kidneys, and low uptake in normal tissues. In conclusion, FVIIai was labeled with fluorine-18 at the N-glycan chain without affecting TF binding. In vitro specificity and a good in vivo imaging contrast at 4 h postinjection was demonstrated.