Abstract Background The clinical success of fluorescence-guided surgery is dependent on tumor-specific probes that can achieve high tumor-to-background contrast. Conventional near-infrared (NIR) fluorophores often alter the pharmacokinetic properties of the parental molecule that result in aggregation, altered biodistribution, and impaired tumor targeting. Methods This present study evaluates two charge-balanced heptamethine cyanine dyes, FNIR-Tag-766 and FNIR-Tag-804, conjugated to a humanized anti-carcinoembryonic antigen antibody (M5A). Their performance was compared to the standard M5A-IR800CW conjugate in both subcutaneous and orthotopic colorectal cancer xenograft models in mice. Mean fluorescence intensity (MFI), tumor-to-background ratio (TBR), and ex vivo biodistribution were compared. Results The M5A-FNIR-766 conjugate produced a greater MFI in tumors at all timepoints compared to M5A-IR800CW, resulting in a significantly improved TBR. Ex vivo analysis at 96 h confirmed higher tumor accumulation for M5A-FNIR-766 and revealed a reduction in hepatic signal for both M5A-FNIR-Tag conjugates. The observations were concordant in the clinically relevant orthotopic model. Conclusion Antibody-fluorophore conjugates linked to the charge-modified FNIR-Tag dyes provide improved tumor-specific signals and a more favorable biodistribution profile than the same antibody conjugated to a conventional dye. By achieving superior performance through intrinsic fluorophore design rather than complex bioconjugation strategies, the approach provides a clinically translatable advancement for tumor-specific FGS.
Cox et al. (Tue,) studied this question.