Finally, fast blood clearance nimotuzumab is a humanized monoclonal antibody that
recognise, with high specific affinity, the epidermal growth factor receptor (EGF-R) which play
an important role in the growth process associated with many solid tumors. In this work, the
whole antibody was digested with papain in order to generate a Fab fragment, derivatized with
NHS-HYNIC-Tfa and radiolabel with technetium-99m (99mTc) as a potential agent of molecular
imaging of cancer. Both, whole and fragment radiolabels were in-vivo and in-vitro
characterized. Radiolabeling conditions with Tricine as coligand and quality controls were
assessed to confirm the integrity of the labeled fragment.
Biodistribution and imaging studies in normal and spontaneous adenocarcinoma mice were
performed at different times to determine the in-vivo characteristics of the radiolabel fragment.
Tumor localization was visualized by conventional gamma camera imaging studies, and the results
were compared with the whole antibody. Also, an immunoreactivity assay was carried out for both.
The results showed clearly the integrity of the nimotuzumab fragment and the affinity by the receptor was verified.
Fab(nimotuzumab)-HYNIC was obtained with high purity and a simple strategy of radiolabeling was performed. Finally, a
fast blood clearance was observed in the biodistribution studies increasing the tumor uptake of Fab(nimotuzumab)-
HYNIC-99mTc over time, with tumor/muscle ratios of 3.81 ± 0.50, 5.16 ± 1.97 and 6.32 ± 1.98 at 1 h, 4 h and 24 h post
injection. Urinary excretion resulted in 32.89 ± 3.91 %ID eliminated at 24 h. Scintigraphy images showed uptake in
the tumor and the activity in non-target organs was consistent with the biodistribution data at the same time points.
Hence, these preliminary results showed important further characteristic of Fab(nimotuzumab)-HYNIC-99mTc as a
molecular imaging agent of cancer.