Improved non-invasive positron emission tomographic imaging of chemotherapy-induced tumor cell death using Zirconium-89-labeled APOMAB®

Abstract

Purpose The chimeric monoclonal antibody (mAb) chDAB4 (APOMAB®) targets the Lupus associated (La)/Sjögren Syndrome-B (SSB) antigen, which is over-expressed in tumors but only becomes available for antibody binding in dead tumor cells. Hence, chDAB4 may be used as a novel theranostic tool to distinguish between responders and nonresponders early after chemotherapy. Here, we aimed to ascertain which positron emitter, Zirconium-89 ([89Zr]ZrIV) or Iodine-124 ([124I]I), was best suited to label chDAB4 for post-chemotherapy PET imaging of tumor-bearing mice and to determine which of two different bifunctional chelators provided optimal tumor imaging by PET using [89Zr]ZrIV-labeled chDAB4. Methods C57BL/6 J mice bearing subcutaneous syngeneic tumors of EL4 lymphoma were either untreated or given chemotherapy, then administered radiolabeled chDAB4 after 24 h with its biodistribution examined using PET and organ assay. We compared chDAB4 radiolabeled with [89Zr] ZrIV or [124I] I, or [89Zr]Zr-chDAB4 using either DFO-NCS or DFOSq as a chelator. Results After chemotherapy, [89Zr]Zr-chDAB4 showed higher and prolonged mean (± SD) tumor uptake of 29.5 ± 5.9 compared to 7.8 ± 1.2 for [124I] I -chDAB4. In contrast, antibody uptake in healthy tissues was not affected. Compared to DFO-NCS, DFOSq did not result in significant differences in tumor uptake of [89Zr]Zr-chDAB4 but did alter the tumor:liver ratio in treated mice 3 days after injection in favour of DFOSq (8.0 ± 1.1) compared to DFO-NCS (4.2 ± 0.7). Conclusion ImmunoPET using chDAB4 radiolabeled with residualizing [89Zr] ZrIV rather than [124I] I optimized post-chemotherapy tumor uptake. Further, PET imaging characteristics were improved by DFOSq rather than DFO-NCS. Therefore, the radionuclide/chelator combination of [89Zr] ZrIV and DFOSq is preferred for the imminent clinical evaluation of chDAB4 as a selective tumor cell death radioligand.

Positron Emission Tomographic Imaging of Tumor Cell Death Using Zirconium-89-Labeled APOMAB® Following Cisplatin Chemotherapy in Lung and Ovarian Cancer Xenograft Models

“…For example, Donnelly et al compared their novel chelator, DFO-Sq, which is a squaramide ester derivative of DFO-pPhe-NCS, to DFO-pPhe-NCS using the HER2-targeting antibody, trastuzumab, and showed improved radiolabeling efficiency and PET imaging characteristics resulting from use of the DFO-Sq chelator [58]. Similarly, in a study of [ 89 Zr]Zr-chDAB4, we found that DFO-Sq as a chelator led to better in vitro and in vivo stability and PET imaging quality than DFO-pPhe-NCS [41]. Another recent study confirmed the very good shelf stability and high chemical purity of a [ 89 Zr]Zr-labeled immunoconjugate employing the DFO-Sq chelator [59].…”

Preclinical evaluation of anti‐VEGFR2 monoclonal antibody ramucirumab labelled with zirconium‐89 for tumour imaging

“…The construction of [ 89 Zr]Zr‐DFO‐RAM began with the conjugation of DFO to RAM and resulted in an immunoconjugate of average ratio 1.2:1 (DFO:RAM), which was an acceptable result compared with the previously published conjugation efficacy (1.3 DFO per antibody) in 89 Zr labelling 24 . [ 89 Zr]Zr‐DFO‐RAM radiochemical purity was over 95%, a level that enabled in vitro and in vivo experiments with no need of further purification.…”

“…The presented study focused on the application of in 89 Zr labelling. 24 [ 89 Zr]Zr-DFO-RAM radiochemical purity was over 95%, a level that enabled in vitro and in vivo experiments with no need of further purification.…”

State of the Art in Radiolabeling of Antibodies with Common and Uncommon Radiometals for Preclinical and Clinical Immuno-PET

“…On the contrary, radionuclides such as gallium-68 (t 1/2 = 67.7 min) are preferred for antibody fragments and mimetics with a very short serum half-life such as nanobodies or affibodies (see Table 1). Although 89 Zr, 64 Cu, and 68 Ga are the most commonly used radiometals for radiolabeling of antibodies, none of them are perfect, triggering research on other emerging radiometals such as manganese-52, yttrium-86, gallium-66, and scandium-44. Moreover, recent advances in [ 18 F]AlF radiochemistry expand the options for radiolabeling of antibodies with 18 F. 18 F is by far the most commonly used PET radionuclide thanks to its short half-life (110 min), its ideal physical properties as extensively shown in small molecule imaging, and its increasing availability.…”

“…Radiometals and chelators have extensively been evaluated to come to the most ideal radiometal−chelator pair for each type of antibody derivative. Although PET imaging of antibodies is a relatively recent tool, applications with 89 Zr, 64 Cu, and 68 Ga have greatly increased in recent years, especially in the clinical setting, while other less common radionuclides such as 52 Mn, 86 Y, 66 Ga, and 44 Sc, but also 18 F as in [ 18 F]AlF are emerging promising candidates for the radiolabeling of antibodies. This review presents a state of the art overview of the practical aspects of radiolabeling of antibodies, ranging from fast kinetic affibodies and nanobodies to slow kinetic intact mAbs.…”