Immuno-PET Imaging and Radioimmunotherapy of ⁶⁴Cu-/¹⁷⁷Lu-Labeled Anti-EGFR Antibody in Esophageal Squamous Cell Carcinoma Model

Abstract

Immuno-PET provides valuable information about tumor location, phenotype, susceptibility to therapy, and treatment response, especially to targeted radioimmunotherapy. In this study, we prepared antiepidermal growth factor receptor (EGFR) antibody via identical chelator, 3,6,9,15-tetraazabicyclo[9.3.1]-pentadeca-1(15),11,13-trience-3,6,9,-triacetic acid (PCTA), labeled with 64 Cu or 177 Lu to evaluate the EGFR expression levels using immuno-PET and the feasibility of radioimmunotherapy in an esophageal squamous cell carcinoma (ESCC) model. Methods: Cetuximab was conjugated with p-SCN-Bn-PCTA and radiolabeled with 64 Cu or 177 Lu. In vitro EGFR expression levels were determined and compared using flow cytometry and cell binding assay. In vivo EGFR expression levels were evaluated via immuno-PET imaging of 64 Cu-cetuximab and biodistribution analysis. Micro-SPECT/CT imaging, biodistribution, and radioimmunotherapy studies of 177 Lu-cetuximab were performed in the ESCC model. Therapeutic responses were monitored using 18 F-FDG PET and immunohistochemical staining. Results: 64 Cu-or 177 Lu-labeled antibodies showed high radiolabeling yield (.98%), stability (.90%), and favorable immunoreactivity. In vitro EGFR status measured by cell binding assay was correlated with the flow cytometry data. Immuno-PET, micro-SPECT/CT, and biodistribution demonstrated specific uptake in ESCC tumors depending on the EGFR expression levels. Tumor accumulation of 64 Cu-and 177 Lu-cetuximab was peaked at 48 and 120 h, respectively. Radioimmunotherapy with 177 Lu-cetuximab showed significant inhibition of tumor growth (P , 0.01) and marked reduction of 18 F-FDG SUV compared with that of control (P , 0.05). Terminal deoxynucleotidyl transferase dUTP nick-end labeling positivity and Ki-67 staining indices increased and decreased, respectively, in the radioimmunotherapy group compared with other groups (P , 0.01). Conclusion: 64 Cu-cetuximab immuno-PET represented EGFR expression levels in ESCC tumors, and 177 Lu-cetuximab radioimmunotherapy effectively inhibited the tumor growth. The diagnostic and therapeutic convergence radiopharmaceutical 64 Cu-/ 177 Lu-PCTA-cetuximab may be useful as a diagnostic tool in patient selection and a potent radioimmunotherapy agent in EGFR-positive ESCC tumors.

Development of 64Cu-NOTA-Trastuzumab for HER2 Targeting: A Radiopharmaceutical with Improved Pharmacokinetics for Human Studies

“…To overcome these problems, novel techniques such as PET and SPECT have been studied for evaluating HER2 expression. Molecular imaging using radiolabeled antibodies can provide real-time information and noninvasively assess the presence of specific targets throughout the body (35). PET imaging depends on the delivery of a targeting ligand containing a positron-emitting radionuclide to a tissue or organ of interest.…”

64Cu-Intraperitoneal Radioimmunotherapy: A Novel Approach for Adjuvant Treatment in a Clinically Relevant Preclinical Model of Pancreatic Cancer

“…64 Cu was produced and purified using previously published methods (14). Cetuximab was 64 Cu-labeled with the chelator 3,6,9,15-tetraazabicyclo[9.3.1]pentadeca-1(15),11,13-triene-3,6,9-triacetic acid (PCTA), since previous studies using PCTA for 64 Cu labeling with cetuximab showed a high radiolabeling yield and in vitro serum stability (8,18). 64 Cu-PCTAcetuximab was prepared according to the methods described in our previous study (8), with the specific activity ranging from 1.1 to 1.7 GBq/mg.…”

“…Additionally, the effectiveness of the 64 Cu-labeled antiepidermal growth factor receptor (EGFR) antibody cetuximab for PET imaging and internal radiotherapy has been well established in many preclinical studies (17,18). We previously showed that ipRIT with 64 Cu-labeled cetuximab was effective in peritoneal-dissemination mouse colorectal and gastric cancer cells (HCT116-RFP and NUGC4-RFP) and that the estimated absorbed doses to normal organs in humans were sufficiently low relative to the reported tolerance doses (8).…”

64Cu-Labeled Repebody Molecules for Imaging of Epidermal Growth Factor Receptor–Expressing Tumors

“…Development of imaging probes for visualization of EGFR expression has been reported, including a 111 In-labeled murine antibody (clone 225), 64 Cu-labeled peptides, and a 64 Cu-labeled chimeric cetuximab molecule for SPECT or PET imaging (28)(29)(30)(31). Furthermore, in terms of in vivo performance, cetuximab variants labeled with 89 Zr (78.41 h) or 177 Lu (6.65 d) have a longer physical half-life than the 64 Cu-labeled molecule (28,32,33). However, EGFR expression with these radiolabeled antibodies could not be visualized in various solid tumors until after 24 h, because of low clearance and tissue penetration.…”