Pre-Clinical Evaluation Of Immunopet Imaging Using Agonist Cd40 Monoclonal Antibody In Pancreatic Tumor-Bearing Mice

Background: A novel [Cu-64]Cu-NOTA-aCD40 immunoPET tracer was developed to image a CD40(+) pancreatic tumor model in C57BL/6 mice and to study the biodistribution profile of the agonist CD40 (aCD40) monoclonal antibody (mAb) alone or combined with other mAbs.Procedures: Copper-64 ([Cu-64]Cu) labeled NOTA-aCD40 and NOTA-IgG (10 mu g; 7 MBq) were injected intravenously into C57BL/6 mice with subcutaneous mT4 tumors to assess specificity 48 h post injection (p.i.) through positron emission tomography/computed tomography (PET/CT) imaging and biodistribution studies (n = 5). [Cu-64]Cu-NOTA-aCD40 was injected alone or simultaneously in combination with a therapeutic mass of cold aCD40 (100 mu g), aPD-1 (200 mu g) and aCTLA-4 (200 mu g) mAbs. A group of mice with or without tumor received the second round of injections 1 or 3 weeks apart, respectively. PET/CT imaging and biodistribution studies were performed at 48 h p.i. The organ dose for [Cu-64]Cu was estimated based on biodistribution studies with 2 mu g [Cu-64]Cu-NOTA-aCD40 (corresponds to 5 mg patient dose) in non-tumor bearing mice.Results: [Cu-64]Cu-NOTA-aCD40 accumulation was 2.3- and 7.8-fold higher than [Cu-64]Cu-NOTA-IgG in tumors and spleen, respectively, indicating the specificity of aCD40 mAb in a mouse pancreatic tumor model. Tumor accumulation of [Cu-64]Cu-NOTA-aCD40was 21.2 +/- 7.3%ID/g at 48 h after injection. Co-injection of [Cu-64]Cu-NOTA-aCD40 with cold aCD40 mAb alone or with PD-1 and CTLA-4 mAbs reduced both spleen and tumor uptake, whereas liver uptake was increased. With the second round of injections, the liver was the only organ with substantial uptake. With a 2 mu g administered dose of [Cu-64]Cu-NOTA-aCD40 in a dosimetry study, the liver to spleen ratio was greater compared to the 10 mu g dose (2.8 vs 0.37; respectively). The human equivalent for the highest dose organ (liver) was 198 +/- 28.7 mu Sv/MBq.Conclusions: A CD40-immunoreactive [Cu-64]Cu-NOTA-aCD40 probewas developed. The ratio of spleen to liver accumulation exceeded that of the IgG isotype and was greatest with a single small, injected mass. The safety of human patient imaging with [Cu-64]Cu was established based on extrapolation of the organ specificity to human imaging. (C) 2021 Elsevier Inc. All rights reserved.