Enhanced tumor retention of radioiodinated anti-epidermal growth factor receptor antibody using novel bifunctional iodination linker for radioimmunotherapy

Abstract

Radioimmunotherapy (RIT) uses an antibody labeled with a radionuclide to deliver cytotoxic radiation to a target tumor cells. Radioiodine is most commonly employed to prepare radiolabeled proteins (antibodies, peptides) for in vitro and in vivo applications. A major shortcoming of radioiodinated proteins prepared by direct labeling methods is their deiodination in vivo. For the preparation of more stable radioiodinated antibodies, we developed a new linker (N-(4-isothiocyanatobenzyl)-2-(3-(tributylstannyl)phenyl) acetamide (IBPA). This study evaluated the usefulness of IBPA as a linker for the stable radioiodinated internalizing antibody, cetuximab. Directly labeled cetuximab ([125I]-cetuximab) was prepared by the chloramine T method. To prepare indirectly labeled cetuximab using IBPA ([125I]-IBPA-cetuximab), IBPA was radioiodinated using chloramine-T to give N-(4-isothiocyanatobenzyl)-2-(3-[125I]phenyl)acetamide ([125I]-IBPA), which was purified by high performance liquid chromatography. [125I]-IBPA was then conjugated to cetuximab. In vitro target binding and internalizing assays were performed in PC9, LS174T, and FaDu cell lines. In vivo planar images were obtained using an Inveon SPECT scanner 3, 24, 48, and 168 h after i.v. injection of [125I]-cetuximab or [125I]-IBPA-cetuximab in athymic mice bearing LS174T tumor xenografts. Specific binding and internalized radioactivity of [125I]-IBPA-cetuximab were higher than those of [125I]-cetuximab in PC9, LS174T, and FaDu cell lines. In planar images scant radioactivity was evident in thyroid glands after injection of [125I]-IBPA-cetuximab, while a high level of radioactivity was present in thyroid glands after injection of [125I]-cetuximab. Tumor uptake value of [125I]-IBPA-cetuximab was higher than that of [125I]-cetuximab for up to 168 h. [125I]-IBPA-cetuximab is stable and resistant to deiodination in vivo. IBPA is a promising bi-functional linker for radioiodination of internalizing monoclonal antibodies for in vivo applications including radioimmunotherapy.

The Use of a Non-Conventional Long-Lived Gallium Radioisotope 66Ga Improves Imaging Contrast of EGFR Expression in Malignant Tumours Using DFO-ZEGFR:2377 Affibody Molecule

“…A pre-requisite for successful use of molecular imaging is the development of a suitable probe that provides sufficiently high sensitivity and specificity. Anti-EGFR monoclonal antibodies labelled with several nuclides [ 7 , 8 , 9 , 10 , 11 , 12 , 13 ] have been evaluated for EGFR visualization. Imaging sensitivity using monoclonal antibodies is, however, limited by their long blood residence and slow tumor accumulation thereby requiring several days (4–7 days) to obtain an acceptable imaging contrast in clinics [ 14 , 15 ].…”

Analysis of Progress and Challenges of EGFR-Targeted Molecular Imaging in Cancer With a Focus on Affibody Molecules

“…10-1550399KR]). Kim et al 47 showed that the tumor uptake value of [125I]I-IBPA-cetuximab was higher than that of [125I]I-cetuximab for up to 168 hours in athymic mice bearing human colorectal adenocarcinoma LS174T tumor xenografts (12.42 ± 1.63%ID/g vs 7.10 ± 1.54%ID/g at 48 hours after injection). The thyroidal uptake value of [125I]I-IBPA-cetuximab (0.09 ± 0.05%ID/g) after injection was ∼8-fold lower than that of [125I]I-cetuximab (0.69 ± 0.36%ID/g), with a statistically significant difference ( P < .005).…”

Immuno-PET for Clinical Theranostic Approaches

“…Unfortunately, when internalization occurs, intracellular catabolism of the antibody and dehalogenation result in the clearance of radioiodine from the target tissue, leading to signal loss and unspecific accumulation such as thyroid for iodine. A number of research groups have developed prosthetic or pendant groups to solve this problem [ 28 , 29 , 30 ], but they are still at the level of preclinical proofs of concepts. Concerning 18 F, although its ease of production in large quantities, its half-life and the low energy of the emitted positron make it an ideal versatile radionuclide for PET imaging, preparing 18 F-conjugates require time-consuming and challenging radiosynthesis.…”