Direct comparison of the in vitro and in vivo stability of DFO, DFO* and DFOcyclo* for 89Zr-immunoPET

Abstract

Purpose Currently, the most commonly used chelator for labelling antibodies with 89 Zr for immunoPET is desferrioxamine B (DFO). However, preclinical studies have shown that the limited in vivo stability of the 89 Zr-DFO complex results in release of 89 Zr, which accumulates in mineral bone. Here we report a novel chelator DFOcyclo*, a preorganized extended DFO derivative that enables octacoordination of the 89 Zr radiometal. The aim was to compare the in vitro and in vivo stability of [ 89 Zr]Zr-DFOcyclo*, [ 89 Zr]Zr-DFO* and [ 89 Zr]Zr-DFO. Methods The stability of 89 Zr-labelled chelators alone and after conjugation to trastuzumab was evaluated in human plasma and PBS, and in the presence of excess EDTA or DFO. The immunoreactive fraction, IC 50 , and internalization rate of the conjugates were evaluated using HER2-expressing SKOV-3 cells. The in vivo distribution was investigated in mice with subcutaneous HER2 + SKOV-3 or HER2 − MDA-MB-231 xenografts by PET/CT imaging and quantitative ex vivo tissue analyses 7 days after injection. Results 89 Zr-labelled DFO, DFO* and DFOcyclo* were stable in human plasma for up to 7 days. In competition with EDTA, DFO* and DFOcyclo* showed higher stability than DFO. In competition with excess DFO, DFOcyclo*-trastuzumab was significantly more stable than the corresponding DFO and DFO* conjugates ( p < 0.001). Cell binding and internalization were similar for the three conjugates. In in vivo studies, HER2 + SKOV-3 tumour-bearing mice showed significantly lower bone uptake ( p < 0.001) 168 h after injection with [ 89 Zr]Zr-DFOcyclo*-trastuzumab (femur 1.5 ± 0.3%ID/g, knee 2.1 ± 0.4%ID/g) or [ 89 Zr]Zr-DFO*-trastuzumab (femur 2.0 ± 0.3%ID/g, knee 2.68 ± 0.4%ID/g) than after injection with [ 89 Zr]Zr-DFO-trastuzumab (femur 4.5 ± 0.6%ID/g, knee 7.8 ± 0.6%ID/g). Blood levels, tumour uptake and uptake in other organs were not significantly different at 168 h after injection. HER2 − MDA-MB-231 tumour-bearing mice showed significantly lower tumour uptake ( p < 0.001) after injection with [ 89 Zr]Zr-DFOcyclo*-trastuzumab (16.2 ± 10.1%ID/g) and [ 89 Zr]Zr-DFO-trastuzumab (19.6 ± 3.2%ID/g) than HER2 + SKOV-3 tumour-bearing mice (72.1 ± 14.6%ID/g and 93.1 ± 20.9%ID/g, respectively), while bone uptake was similar. Conclusion 89 Zr-labelled DFOcyclo* and DFOcyclo*-trastuzumab...

WITHDRAWN: Positron Emission Tomographic imaging of tumor cell death using Zirconium-89-labeled APOMAB® following cisplatin chemotherapy in lung and ovarian cancer xenograft models

“…However, new chelators are being developed and may improve the stability and biodistribution of 89 Zr-labeled mAbs such as [ 89 Zr]Zr-chDAB4, which can generate free [ 89 Zr]Zr IV and result in its uptake by bone. For example, Donnelly et al compared their novel chelator DFO-Sq to DFO-pPhe-NCS using the HER2-targeting antibody, trastuzumab[47] and Raave et al also indicated greater stability and less bone accumulation when DFOcyclo was used in preference to DFO to radiolabel trastuzumab with [ 89 Zr]Zr IV[48]. Consequently, the stability of the chelator together with the activity and antibody concentration[49] of [ 89 Zr]Zr-labeled mAbs will be important parameters to consider in planning future clinicals of [ 89 Zr]Zr-labeled chDAB4.…”

Synthesize of a novel 89Zr labeled HER2 affibody and its application study in tumor PET imaging

“…It is consisted of three hydroxamate groups and forms a thermodynamically stable complex with zirconium. [35] The radioactivities distributing in the tumor showed significant heterogeneity by ex vivo immunohistochemistry and autoradiography. Abundant HER2 was expressed in the periphery of the tumor and the corresponding radio signal was strong.…”

Cross-species/cross-modality physiologically based pharmacokinetics for biologics: 89Zr-labelled albumin-binding domain antibody GSK3128349 in humans

“…Zr equilibrium with DFO is strongly shifted toward the complex, but remains rapidly reversible as demonstrated by the dissociating effect of excess free competing chelator, e.g., ethylenediaminetetraacetic acid. 55 Likewise, around 0.2% of 89 Zr was found to have dissociated during 24-hour incubation in plasma in vitro, 56 which would be subject to renal filtration with possibility of accumulating to PET-detectable levels in the small volume of kidneys. Given the patterns of 89 Zr tissue distribution dependence on the compound, be it chloride, oxalate or DFO chelate, 51 this is an aspect that needs to be considered whilst interpreting the tissue distribution data of 89 Zr-labeled proteins in immunoPET studies.…”