Copper-64-Labeled Antibody Fragments for Immuno-PET/Radioimmunotherapy with Low Renal Radioactivity Levels and Amplified Tumor-Kidney Ratios

Abstract

Copper-64 ( 64 Cu)-labeled antibody fragments such as Fab are useful for molecular imaging (immuno-PET) and radioimmunotherapy. However, these fragments cause high and persistent localization of radioactivity in the kidneys after injection. To solve this problem, this study assessed the applicability of a molecular design to 64 Cu, which reduces renal radioactivity levels by liberating a urinary excretory radiometabolite from antibody fragments at the renal brush border membrane (BBM). Since 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA) forms a stable complex with Cu, NOTA-conjugated Met-Val-Lys-maleimide (NOTA-MVK-Mal), which is a radio-gallium labeling agent for antibody fragments, was evaluated for applicability to 64 Cu. The MVK linkage was recognized by the BBM enzymes to liberate [ 64 Cu]Cu-NOTA-Met although the recognition of the MVK sequence for the [ 64 Cu]Cu-NOTA-MVK derivative was reduced compared with that of its [ 67 Ga]Ga-counterpart, probably due to the difference in the charge of the metal-NOTA complexes. When injected into mice, [ 64 Cu]Cu-NOTA-MVK-Fab resulted in similar renal radioactivity levels to the 67 Ga-labeled counterpart. In addition, [ 64 Cu]Cu-NOTA-MVK-Fab resulted in lower renal radioactivity levels than those from 64 Cu-labeled Fab using a conventional method, without a reduction in the tumor radioactivity levels. These findings indicate that our approach to reducing renal radioactivity levels by liberating a radiolabeled compound from antibody fragments at the renal BBM for urinary excretion is applicable to 64 Cu-labeled antibody fragments and useful for immuno-PET and radioimmunotherapy.

Application of Cleavable Linkers to Improve Therapeutic Index of Radioligand Therapies

“…Research groups have leveraged the MVK motif to reduce renal activity for 68 Ga-labeled NOTA-exendin 4 [ 64 ], 68 Ga-labeled DOTA-PSMA inhibitor [ 65 ], and 64 Cu/ 67 Ga-labeled NOTA-Fab [ 66 ]. In each case, the addition of the cleavable linker was able to reduce the renal uptake of the tracer compared with the control.…”

Diagnostic and Therapeutic Radiopharmaceuticals

“…30 Other strategies to produce high radioactivity concentrations in tumor tissues have been reported, such as pre-targeting approaches 31,32 and the design of radiopharmaceuticals possessing differential metabolism in tumors versus organs. 33,34 Three papers have analyzed PET/SPECT images of animal cancer models to study the change of accumulation of the antibody trastuzumab with lowering hyaluronan concentration, 35 the stereoisomerism of 18 F-radiolabeled nonnatural cyclic amino acids, 36,37 and the therapeutic effect of nanocapsules sealed with 153 Sm. E. First-in-human studies of PET radiopharmaceuticals.…”

“…To reach this aim, the addition of albumin-binding and immunoglobulin-binding domains in FAP- and PSMA-targeting radioligands , and HER2 nanobodies has been chosen to prolong their blood circulation time, enhance tumor uptake, and prolong tumor residence . Other strategies to produce high radioactivity concentrations in tumor tissues have been reported, such as pre-targeting approaches , and the design of radiopharmaceuticals possessing differential metabolism in tumors versus organs. , Three papers have analyzed PET/SPECT images of animal cancer models to study the change of accumulation of the antibody trastuzumab with lowering hyaluronan concentration, the stereo­isomerism of 18 F-radiolabeled non-natural cyclic amino acids, , and the therapeutic effect of nanocapsules sealed with 153 Sm Development of multimodal probes combining PET (and SPECT) imaging with fluorescence − and photodynamic treatment.…”

Diagnostic and Therapeutic Radiopharmaceuticals

“…30 Other strategies to produce high radioactivity concentrations in tumor tissues have been reported, such as pre-targeting approaches 31,32 and the design of radiopharmaceuticals possessing differential metabolism in tumors versus organs. 33,34 Three papers have analyzed PET/SPECT images of animal cancer models to study the change of accumulation of the antibody trastuzumab with lowering hyaluronan concentration, 35 the stereoisomerism of 18 F-radiolabeled nonnatural cyclic amino acids, 36,37…”