The radiochemical yield for 18F-alakyne folate was 22%. Mice inoculated with human KB cancer cells were intravenously injected with 18F-DBCO folate and 18F-alakyne folate. Both folate derivatives demonstrated stability in human serum albumin and high affinity for the folate receptor. However, 18F-DBCO folate was more lipophilic than 18F-alakyne folate, which resulted in a greater degree of non-specific binding. The in vivo performance was consequently higher for 18F-alakyne folate, giving much clearer visualization of folate receptor-positive tumours in PET scans7. There was lower tumour-to-liver contrast than expected due to accumulation of 18F-alakyne folate in the liver and gal bladder.
In view of high radiochemical yield, radiochemical purity and favourable pharmacokinetics, 18F-alakyne folate is expected to be a promising candidate for folate receptor PET imaging. However, there remains the need to fine-tune the metabolism profile of 18F-alakyne folate.
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