Dataset Information

124I-huA33 antibody uptake is driven by A33 antigen concentration in tissues from colorectal cancer patients imaged by immuno-PET.

ABSTRACT:

Unlabelled

The primary aim of this analysis was to examine the quantitative features of antibody-antigen interactions in tumors and normal tissue after parenteral administration of antitumor antibodies to human patients.

Methods

Humanized anti-A33 antibody (10 mg) labeled with the positron-emitting radionuclide (124)I ((124)I-huA33) was injected intravenously in 15 patients with colorectal cancer. Clinical PET/CT was performed approximately 1 wk later, followed by a detailed assay of surgically removed tissue specimens including radioactivity counting, autoradiography, immunohistochemistry, and antigen density determination.

Results

PET/CT showed high levels of antibody targeting in tumors and normal bowel. In tissue specimens, the spatial distribution of (124)I-huA33 conformed to that of A33 antigen, and there was a linear relationship between the amount of bound antibody and antigen concentration. Antibody uptake was high in 1- to 2-mm regions of antigen-positive tumor cells (mean, ~0.05 percentage injected dose per gram) and in antigen-positive normal colonic mucosa (mean, ~0.03 percentage injected dose per gram). The estimated binding site occupancy for tumor and normal colon was 20%-50%.

Conclusion

The in vivo biodistribution of (124)I-huA33 in human patients 1 wk after antibody administration was determined by A33 antigen expression. Our data imply that the optimal strategy for A33-based radioimmunotherapy of colon cancer will consist of a multistep treatment using a radionuclide with short-range (α- or β-particle) emissions.

SUBMITTER: O'Donoghue JA

PROVIDER: S-EPMC3394180 | biostudies-literature | 2011 Dec

REPOSITORIES: biostudies-literature

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Publications

124I-huA33 antibody uptake is driven by A33 antigen concentration in tissues from colorectal cancer patients imaged by immuno-PET.

O'Donoghue Joseph A JA Smith-Jones Peter M PM Humm John L JL Ruan Shutian S Pryma Daniel A DA Jungbluth Achim A AA Divgi Chaitanya R CR Carrasquillo Jorge A JA Pandit-Taskar Neeta N Fong Yuman Y Strong Vivian E VE Kemeny Nancy E NE Old Lloyd J LJ Larson Steven M SM

Journal of nuclear medicine : official publication, Society of Nuclear Medicine 20111108 12

<h4>Unlabelled</h4>The primary aim of this analysis was to examine the quantitative features of antibody-antigen interactions in tumors and normal tissue after parenteral administration of antitumor antibodies to human patients.<h4>Methods</h4>Humanized anti-A33 antibody (10 mg) labeled with the positron-emitting radionuclide (124)I ((124)I-huA33) was injected intravenously in 15 patients with colorectal cancer. Clinical PET/CT was performed approximately 1 wk later, followed by a detailed assay ...[more]

PMID: 22068895

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Project description:UnlabelledTumor endothelial marker 1 (TEM1/endosialin) is a tumor vascular marker highly overexpressed in multiple human cancers with minimal expression in normal adult tissue. In this study, we report the preparation and evaluation of (124)I-MORAb-004, a humanized monoclonal antibody targeting an extracellular epitope of human TEM1 (hTEM1), for its ability to specifically and sensitively detect vascular cells expressing hTEM1 in vivo.MethodsMORAb-004 was directly iodinated with (125)I and (124)I, and in vitro binding and internalization parameters were characterized. The in vivo behavior of radioiodinated MORAb-004 was characterized in mice bearing subcutaneous ID8 tumors enriched with mouse endothelial cells expressing hTEM1 and by biodistribution and small-animal immuno-PET studies.ResultsMORAb-004 was radiolabeled with high efficiency and isolated in high purity. In vitro studies demonstrated specific and sensitive binding of MORAb-004 to MS1 mouse endothelial cells expressing hTEM1, with no binding to control MS1 cells. (125)I-MORAb-004 and (124)I-MORAb-004 both had an immunoreactivity of approximately 90%. In vivo biodistribution experiments revealed rapid, highly specific and sensitive uptake of MORAb-004 in MS1-TEM1 tumors at 4 h (153.2 ± 22.2 percentage injected dose per gram [%ID/g]), 24 h (127.1 ± 42.9 %ID/g), 48 h (130.3 ± 32.4 %ID/g), 72 h (160.9 ± 32.1 %ID/g), and 6 d (10.7 ± 1.8 %ID/g). Excellent image contrast was observed with (124)I-immuno-PET. MORAb-004 uptake was statistically higher in TEM1-positive tumors than in control tumors. Binding specificity was confirmed by blocking studies using excess nonlabeled MORAb-004.ConclusionIn our preclinical model, with hTEM1 exclusively expressed on engineered murine endothelial cells that integrate into the tumor vasculature, (124)I-MORAb-004 displays high tumor-to-background tissue contrast for detection of hTEM1 in easily accessible tumor vascular compartments. These studies strongly suggest the clinical utility of (124)I-MORAb-004 immuno-PET in assessing TEM1 tumor-status.

Project description:BackgroundPET scans using zirconium-89 labelled monoclonal antibodies (89Zr-mAbs), known as 89Zr-immuno-PET, are made to measure uptake in tumour and organ tissue. Uptake is related to the supply of 89Zr-mAbs in the blood. Measuring activity concentrations in blood, however, requires invasive blood sampling. This study aims to identify the best delineation strategy to obtain the image-derived blood concentration (IDBC) from 89Zr-immuno-PET scans.MethodsPET imaging and blood sampling of two 89Zr-mAbs were included, 89Zr-cetuximab and 89Zr-durvalumab. For seven patients receiving 89Zr-cetuximab, PET scans on 1-2 h, 2 and 6 days post-injection (p.i.) were analysed. Five patients received three injections of 89Zr-durvalumab. The scanning protocol for the first two injections consisted of PET scanning on 2, 5 and 7 days p.i. and for the third injection only on 7 days p.i. Blood samples were drawn with every PET scan and the sample-derived blood concentration (SDBC) was used as gold standard for the IDBC. According to an in-house developed standard operating procedure, the aortic arch, ascending aorta, descending aorta and left ventricle were delineated. Bland-Altman analyses were performed to assess the bias (mean difference) and variability (1.96 times the standard deviation of the differences) between IDBC and SDBC.ResultsOverall, the activity concentration obtained from the IDBC was lower than from the SDBC. When comparing IDBC with SDBC, variability was smallest for the ascending aorta (20.3% and 17.0% for 89Zr-cetuximab and 89Zr-durvalumab, respectively). Variability for the other regions ranged between 17.9 and 30.8%. Bias for the ascending aorta was - 10.9% and - 11.4% for 89Zr-cetuximab and 89Zr-durvalumab, respectively.ConclusionsImage-derived blood concentrations should be obtained from delineating the ascending aorta in 89Zr-immuno-PET scans, as this results in the lowest variability with respect to sample-derived blood concentrations.

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Project description:Antibody-based PET tracers are exceptionally well-suited for determination of the in vivo biodistribution and quantification of therapeutic antibodies. The continued expansion in antibody-based therapeutics has accordingly driven the development towards more robust conjugation strategies in order to reliably predict the performance of such agents. We therefore aimed to evaluate the effect of site-specific labeling by enzymatic remodeling on the stability, immuno-reactivity and tumor-targeting properties of the monoclonal antibody (mAb) trastuzumab and compare it to conventional, random labeling in a HER2-positive xenograft mouse model. Methods: Trastuzumab was conjugated with the p-SCN-Bn-Desferrioxamine (SCN-Bn-DFO) chelator randomly on lysine residues or site-specifically on enzymatically modified glycans using either β-galactosidase or endoglycosidase S2 prior to 89Zr radiolabeling. 89Zr-DFO-trastuzumab was injected into SK-OV-3 tumor-bearing NMRI nude mice. The antibody dose was titrated with either 100 µg or 500 µg of unlabeled trastuzumab. Mice underwent small animal PET/CT imaging 24, 70 and 120 hours post-injection for longitudinal assessment. Parallel experiments were conducted with an isotype control matched antibody. In vivo imaging was supported by conventional ex vivo biodistribution and HER2 immuno-histochemistry. Furthermore, site-specifically labeled 89Zr-DFO-trastuzumab was evaluated in a panel of subcutaneous patient-derived xenograft (PDX) models. Additionally, the affinity, in vitro stability and immuno-reactivity were assessed for all tracers. Results: Site-specific labeling significantly increased PET tumor uptake (One-way ANOVA, p<0.0001) at all time-points when compared to random labeling. Mean tumor uptakes were 6.7 ± 1.7, 13.9 ± 3.3 and 15.3 ± 3.8 % injected dose per gram tissue (%ID/g) at 70 hours post-injection, for random, β-galactosidase or endoglycosidase S2 labeled probes, respectively. Co-injection with unlabeled trastuzumab increased the circulation time of tracers but did not alter tumor uptake notably. Site-specific probes presented with a superior in vitro stability and immuno-reactivity compared to the randomly labeled probe. Ex vivo biodistribution confirmed the data obtained by in vivo PET imaging, and site-specific 89Zr-DFO-trastuzumab successfully detected HER2-positive tumors in PDX mouse models. Conclusion: 89Zr-DFO-trastuzumab is well-matched for specific immuno-PET imaging of HER2-positive tumors and site-specific labeling of trastuzumab by the SiteClickTM technology minimizes the impact of the DFO chelator on immuno-reactivity, stability and biodistribution. These findings support further development of site-specifically radiolabeled mAbs for immuno-PET.

Dataset Information

124I-huA33 antibody uptake is driven by A33 antigen concentration in tissues from colorectal cancer patients imaged by immuno-PET.

Unlabelled

Methods

Results

Conclusion

Publications

124I-huA33 antibody uptake is driven by A33 antigen concentration in tissues from colorectal cancer patients imaged by immuno-PET.

Similar Datasets

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