Fab(nimotuzumab)-HYNIC-99mTc: Antibody Fragmentation for Molecular Imaging Agents
Victoria Calzada1, María Fernanda García, Luis Michel Alonso-Martínez
1Departamento de Radiofarmacia, Centro de Investigaciones Nucleares, Facultad de Ciencias, Universidad de la República, Uruguay. vcalzada@cin.edu.uy.
Abstract:
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.
Insights
This study developed a technetium-99m labeled nimotuzumab fragment (Fab(nimotuzumab)-HYNIC-99mTc) for cancer molecular imaging. The agent demonstrated fast blood clearance and increased tumor uptake, showing promise for improved cancer detection.
Area of Science:
- Nuclear Medicine
- Oncology
- Radiopharmaceutical Chemistry
Background:
- Epidermal Growth Factor Receptor (EGF-R) is crucial in solid tumor growth.
- Nimotuzumab, a humanized monoclonal antibody, targets EGF-R with high affinity.
- Developing targeted radiopharmaceuticals is key for effective cancer molecular imaging.
Purpose of the Study:
- To develop and characterize a technetium-99m labeled nimotuzumab Fab fragment for cancer imaging.
- To evaluate the in-vivo behavior and tumor targeting efficacy of the radiolabeled fragment.
- To compare the imaging potential of the Fab fragment with the whole antibody.
Main Methods:
- Digestion of nimotuzumab with papain to generate Fab fragments.
- Derivatization of Fab fragments with NHS-HYNIC-Tfa and radiolabeling with technetium-99m (99mTc).
- In-vitro and in-vivo characterization including biodistribution, imaging studies in mice, and immunoreactivity assays.
Main Results:
- Successfully synthesized and radiolabeled Fab(nimotuzumab)-HYNIC with high purity.
- Demonstrated fast blood clearance and significant tumor uptake in mice models.
- Achieved favorable tumor-to-muscle ratios (up to 6.32 ± 1.98 at 24h) and confirmed receptor affinity.
Conclusions:
- Fab(nimotuzumab)-HYNIC-99mTc exhibits promising characteristics as a molecular imaging agent for cancer.
- Fast blood clearance and enhanced tumor uptake suggest improved diagnostic potential.
- Further investigation is warranted to establish its clinical utility in cancer detection.
