Related Experiment Video
Updated: Mar 26, 2026
Determining Binding Affinity KD of Radiolabeled Antibodies to Immobilized Antigens
Published on: June 23, 2022
PET imaging of epidermal growth factor receptor expression in tumours using 89Zr-labelled ZEGFR:2377 affibody
Javad Garousi1, Ken G Andersson2, Bogdan Mitran3
1Institute of Immunology, Genetic and Pathology, Uppsala University, SE-75185 Uppsala, Sweden.
Abstract:
Epidermal growth factor receptor (EGFR) is a transmembrane tyrosine kinase receptor, which is overexpressed in many types of cancer. The use of EGFR-targeting monoclonal antibodies and tyrosine-kinase inhibitors improves significantly survival of patients with colorectal, non-small cell lung cancer and head and neck squamous cell carcinoma. Detection of EGFR overexpression provides important prognostic and predictive information influencing management of the patients. The use of radionuclide molecular imaging would enable non-invasive repeatable determination of EGFR expression in disseminated cancer. Moreover, positron emission tomography (PET) would provide superior sensitivity and quantitation accuracy in EGFR expression imaging. Affibody molecules are a new type of imaging probes, providing high contrast in molecular imaging. In the present study, an EGFR-binding affibody molecule (ZEGFR:2377) was site-specifically conjugated with a deferoxamine (DFO) chelator and labelled under mild conditions (room temperature and neutral pH) with a positron-emitting radionuclide (89)Zr. The (89)Zr-DFO-ZEGFR:2377 tracer demonstrated specific high affinity (160 ± 60 pM) binding to EGFR-expressing A431 epidermoid carcinoma cell line. In mice bearing A431 xenografts, (89)Zr-DFO-ZEGFR:2377 demonstrated specific uptake in tumours and EGFR-expressing tissues. The tracer provided tumour uptake of 2.6 ± 0.5% ID/g and tumour-to-blood ratio of 3.7 ± 0.6 at 24 h after injection. (89)Zr-DFO-ZEGFR:2377 provides higher tumour-to-organ ratios than anti-EGFR antibody (89)Zr-DFO-cetuximab at 48 h after injection. EGFR‑expressing tumours were clearly visualized by microPET using (89)Zr-DFO-ZEGFR:2377 at both 3 and 24 h after injection. In conclusion, 8(9)Zr-DFO-ZEGFR:2377 is a potential probe for PET imaging of EGFR-expression in vivo.
Insights
A novel imaging probe, (89)Zr-DFO-ZEGFR:2377, shows promise for non-invasively detecting epidermal growth factor receptor (EGFR) expression in tumors. This tracer enables clear visualization of EGFR-expressing tumors using positron emission tomography (PET).
Area of Science:
- Nuclear Medicine
- Molecular Imaging
- Oncology
Background:
- Epidermal growth factor receptor (EGFR) is a key target in various cancers, with overexpression impacting patient prognosis and treatment.
- Current diagnostic methods for EGFR expression are often invasive or lack the sensitivity needed for disseminated disease.
- Radionuclide molecular imaging, particularly positron emission tomography (PET), offers a non-invasive approach for assessing EGFR expression.
Purpose of the Study:
- To develop and evaluate a novel affibody-based imaging probe, (89)Zr-DFO-ZEGFR:2377, for positron emission tomography (PET) imaging of EGFR expression.
- To assess the binding affinity, specificity, and in vivo performance of the (89)Zr-DFO-ZEGFR:2377 tracer in preclinical models.
Main Methods:
- Site-specific conjugation of an EGFR-binding affibody molecule (ZEGFR:2377) with a deferoxamine (DFO) chelator.
- Radiolabeling of the DFO-conjugated affibody with the positron-emitting radionuclide zirconium-89 ((89)Zr) under mild conditions.
- In vitro assessment of binding affinity to EGFR-expressing cells and in vivo evaluation in mice bearing A431 xenografts using microPET imaging.
Main Results:
- The (89)Zr-DFO-ZEGFR:2377 tracer demonstrated high specific affinity (160 ± 60 pM) for EGFR-expressing A431 cells.
- In vivo studies showed specific tumor uptake (2.6 ± 0.5% ID/g) and favorable tumor-to-blood ratios (3.7 ± 0.6 at 24 h) in xenograft models.
- The tracer achieved higher tumor-to-organ ratios compared to (89)Zr-DFO-cetuximab and enabled clear visualization of EGFR-expressing tumors via microPET.
Conclusions:
- The developed (89)Zr-DFO-ZEGFR:2377 tracer is a promising candidate for sensitive and specific in vivo PET imaging of EGFR expression.
- This affibody-based probe facilitates non-invasive, repeatable assessment of EGFR status in tumors, potentially aiding in treatment selection and monitoring.
- The findings support the potential clinical utility of (89)Zr-DFO-ZEGFR:2377 for personalized cancer therapy guided by EGFR expression levels.
