Imaging the distribution of an antibody-drug conjugate constituent targeting mesothelin with 89Zr and IRDye 800CW in mice bearing human pancreatic tumor xenografts

Abstract

Mesothelin is a tumor differentiation antigen expressed by epithelial tumors, including pancreatic cancer. Currently, mesothelin is being targeted with an antibody-drug conjugate (ADC) consisting of a mesothelin-specific antibody coupled to a highly potent chemotherapeutic drug. Considering the toxicity of the ADC and reduced accessibility of pancreatic tumors, non-invasive imaging could provide necessary information. We therefore developed a zirconium-89 (89Zr) labeled anti-mesothelin antibody (89Zr-AMA) to study its biodistribution in human pancreatic tumor bearing mice. Biodistribution and dose-finding of 89Zr-AMA were studied 144 h after tracer injection in mice with subcutaneously xenografted HPAC. MicroPET imaging was performed 24, 72 and 144 h after tracer injection in mice bearing HPAC or Capan-2. Tumor uptake and organ distribution of 89Zr-AMA were compared with nonspecific 111In-IgG. Biodistribution analyses revealed a dose-dependent 89Zr-AMA tumor uptake. Tumor uptake of 89Zr-AMA was higher than 111In-IgG using the lowest tracer dose. MicroPET showed increased tumor uptake over 6 days, whereas activity in blood pool and other tissues decreased. Immunohistochemistry showed that mesothelin was expressed by the HPAC and CAPAN-2 tumors and fluorescence microscopy revealed that AMA-800CW was present in tumor cell cytoplasm. 89Zr-AMA tumor uptake is antigen-specific in mesothelin-expressing tumors. 89Zr-AMA PET provides non-invasive, real-time information about AMA distribution and tumor targeting.

Influence of protein properties and protein modification on biodistribution and tumor uptake of anticancer antibodies, antibody derivatives, and non‐Ig scaffolds

“…Therefore, increasing the d/p ratio may result in quenching of fluorescent signal and may increase the tendency of labeled proteins to aggregate. Aggregation has been observed with panitumumab conjugated with a NIR fluorescent cyanine dye (FNIR‐G‐765) at a d/p ratio of 5 and with an antimesothelin antibody that was conjugated with IRDye 800CW at a d/p ratio of 4 . For both constructs a d/p ratio of 2 did not result in visible precipitation of labeled antibodies.…”

“…c Not observed with anti-HER2 125 I-antibodies. d Observed at a dose of 1 g but not at a dose of 20 g. e Not observed with anti-HER2 111 In-antibodies. f Renal accumulation likely increases with the increase of overall charge of proteins that are prone to renal excretion.…”

“…The above‐mentioned studies have been performed in mice, in which high c/p ratios are often used to obtain high‐quality scans. However, lower c/p ratios are generally used in nonhuman primate and clinical studies . Such differences can hamper extrapolation of preclinical results to the clinical setting.…”

Harnessing Integrative Omics to Facilitate Molecular Imaging of the Human Epidermal Growth Factor Receptor Family for Precision Medicine

“…These results indicated that 89 Zr-trastuzumab might be used to identify patients who benefit from T-DM1 therapy. In another study, 89 Zr-labeled MMOT0530A, the naked antibody component of the mesothelin-ADC DMOT4039A, accumulated preferentially in human pancreatic cancer xenografts 108. 89 Zr-MMOT0530A was further tested in 11 patients with ovarian or pancreatic cancer, revealing a large degree of heterogeneity of lesion tracer uptake, while PET uptake 4 days post injection correlated with IHC staining for mesothelin on a per patient basis.…”

Theranostics Using Antibodies and Antibody-Related Therapeutics

“…Naked antibody uptake is assumed to reflect ADC uptake and thus may predict whether a patient will respond to ADC therapy. This approach was used in 3 preclinical trials in mice and 1 study in both mice and nonhuman primates (37)(38)(39)(40). Organ biodistribution and tracer tumor uptake were assessed.…”