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89Zr-trastuzumab PET supports clinical decision making in breast cancer patients, when HER2 status cannot be determined by standard work up.

ABSTRACT: BACKGROUND:Up-to-date information on human epidermal growth factor receptor 2 (HER2) status in breast cancer (BC) is important, as expression can vary during the course of the disease, necessitating anti-HER2 therapy adjustments. Repeat biopsies, however, are not always possible. In this feasibility trial we assessed whether 89Zr-trastuzumab PET could support diagnostic understanding and aid clinical decision making, when HER2 status could not be determined by standard work up. Additionally, HER2 status on circulating tumour cells (CTCs) was assessed. PATIENTS AND METHODS:89Zr-trastuzumab PET was performed in patients if disease HER2 status remained unclear after standard work up (bone scan, 18F-FDG PET, CT and if feasible a biopsy). PET result and central pathologic revision of available tumour biopsies were reported to the referring physician. CTC HER2 status prior to PET was evaluated afterwards and therefore not reported. Diagnostic understanding and treatment decision questionnaires were completed by the referring physicians before, directly after and???3 months after 89Zr-trastuzumab PET. RESULTS:Twenty patients were enrolled: 8 with two primary cancers (HER2-positive and HER2-negative BC or BC and non-BC), 7 with metastases inaccessible for biopsy, 4 with prior HER2-positive and -negative metastases and 1 with primary BC with equivocal HER2 status. 89Zr-trastuzumab PET was positive in 12 patients, negative in 7 and equivocal in 1 patient. In 15/20 patients, 89Zr-trastuzumab PET supported treatment decision. The scan altered treatment of 8 patients, increased physicians' confidence without affecting treatment in 10, and improved physicians' disease understanding in 18 patients. In 10/20 patients CTCs were detected; 6/10 showed HER2 expression. CTC HER2 status was not correlated to 89Zr-trastuzumab PET result or treatment decision. CONCLUSION:89Zr-trastuzumab PET supports clinical decision making when HER2 status cannot be determined by standard work up. The impact of CTC HER2 status needs to be further explored.

SUBMITTER: Bensch F

PROVIDER: S-EPMC6208812 | biostudies-literature | 2018 Dec

REPOSITORIES: biostudies-literature

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<sup>89</sup>Zr-trastuzumab PET supports clinical decision making in breast cancer patients, when HER2 status cannot be determined by standard work up.

Bensch Frederike F Brouwers A H AH Lub-de Hooge M N MN de Jong J R JR van der Vegt B B Sleijfer S S de Vries E G E EGE Schröder C P CP

European journal of nuclear medicine and molecular imaging 20180730 13

<h4>Background</h4>Up-to-date information on human epidermal growth factor receptor 2 (HER2) status in breast cancer (BC) is important, as expression can vary during the course of the disease, necessitating anti-HER2 therapy adjustments. Repeat biopsies, however, are not always possible. In this feasibility trial we assessed whether <sup>89</sup>Zr-trastuzumab PET could support diagnostic understanding and aid clinical decision making, when HER2 status could not be determined by standard work up ...[more]

PMID: 30058029

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Project description:BackgroundDe novo or acquired resistance in breast cancer leads to treatment failures and disease progression. In human epidermal growth factor receptor 2 (HER2)-positive (HER2+) breast cancer, Src, a non-receptor tyrosine kinase, is identified as a major mechanism of trastuzumab resistance, with its activation stabilizing aberrant HER2 signaling, thus making it an attractive target for inhibition. Here, we explored the causal relationship between Src and HER2 by examining the potential of 89Zr-trastuzumab as a surrogate imaging marker of Src activity upon inhibition with dasatinib in HER2+ breast cancer.MethodsHER2+ primary breast cancer cell lines BT-474 and trastuzumab-resistant JIMT-1 were treated with dasatinib and assessed for expression and localization of HER2, Src, and phosphorylated Src (pSrc) (Y416) through western blots and binding assays. Mice bearing BT-474 or JIMT-1 tumors were treated for 7 or 14 days with dasatinib. At the end of each treatment, tumors were imaged with 89Zr-trastuzumab. The results of 89Zr-trastuzumab positron emission tomography (PET) was compared against tumor uptake of fluorodeoxyglucose (18F-FDG) obtained the day before in the same group of mice. Ex vivo western blots and immunohistochemical staining (IHC) were performed for validation.ResultsIn BT-474 and JIMT-1 cells, treatment with dasatinib resulted in a decrease in internalized 89Zr-trastuzumab. Confirmation with immunoblots displayed abrogation of pSrc (Y416) signaling; binding assays in both cell lines demonstrated a decrease in cell surface and internalized HER2-bound tracer. In xenograft models, dasatinib treatment for 7 days (BT-474, 11.05 ± 2.10 % injected dose per gram of tissue %(ID)/g; JIMT-1, 3.88 ± 1.47 %ID/g)) or 14 days (BT-474, 9.20 ± 1.85 %ID/g; JIMT-1, 4.45 ± 1.23 %ID/g) resulted in a significant decrease in 89Zr-trastuzumab uptake on PET compared to untreated control (BT-474, 17.88 ± 2.18 %ID/g; JIMT-1, 8.04 ± 1.47 %ID/g). No difference in 18F-FDG uptake was observed between control and treated cohorts. A parallel decrease in membranous HER2 and pSrc (Y416) staining was observed in tumors post treatment on IHC. Immunoblots further validated the 89Zr-trastuzumab-PET readout. Positive correlation was established between 89Zr-trastuzumab tumor uptake versus tumor regression, pSrc and pHER2 expression.Conclusions89Zr-trastuzumab can potentially assess tumor response to dasatinib in HER2+ breast cancer and could be used as a surrogate tool to monitor early changes in Src signaling downstream of HER2.

Project description:One of the main challenges of PET imaging with 89Zr-labeled monoclonal antibodies (mAbs) remains the long blood circulation of the radiolabeled mAbs, leading to high background signals, decreasing image quality. To overcome this limitation, here we report the use of a bioorthogonal linker cleavage approach (click-to-release chemistry) to selectively liberate [89Zr]Zr-DFO from trans-cyclooctene-functionalized trastuzumab (TCO-Tmab) in blood, following the administration of a tetrazine compound (trigger) in BT-474 tumor-bearing mice. Methods: We created a series of TCO-DFO constructs and evaluated their performance in [89Zr]Zr-DFO release from Tmab in vitro using different trigger compounds. The in vivo behavior of the best performing [89Zr]Zr-TCO-Tmab was studied in healthy mice first to determine the optimal dose of the trigger. To find the optimal time for the trigger administration, the rate of [89Zr]Zr-TCO-Tmab internalization was studied in BT-474 cancer cells. Finally, the trigger was administered 6 h or 24 h after [89Zr]Zr-TCO-Tmab- administration in tumor-bearing mice to liberate the [89Zr]Zr-DFO fragment. PET scans were obtained of tumor-bearing mice that received the trigger 6 h post-[89Zr]Zr-TCO-Tmab administration. Results: The [89Zr]Zr-TCO-Tmab and trigger pair with the best in vivo properties exhibited 83% release in 50% mouse plasma. In tumor-bearing mice the tumor-blood ratios were markedly increased from 1.0 ± 0.4 to 2.3 ± 0.6 (p = 0.0057) and from 2.5 ± 0.7 to 6.6 ± 0.9 (p < 0.0001) when the trigger was administered at 6 h and 24 h post-mAb, respectively. Same day PET imaging clearly showed uptake in the tumor combined with a strongly reduced background due to the fast clearance of the released [89Zr]Zr-DFO-containing fragment from the circulation through the kidneys. Conclusions: This is the first demonstration of the use of trans-cyclooctene-tetrazine click-to-release chemistry to release a radioactive chelator from a mAb in mice to increase tumor-to-blood ratios. Our results suggest that click-cleavable radioimmunoimaging may allow for substantially shorter intervals in PET imaging with full mAbs, reducing radiation doses and potentially even enabling same day imaging.

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.

Project description:BackgroundIn vivo monitoring of cell biodistribution using positron emission tomography (PET) provides a quantitative non-invasive method to further optimize cell therapies and related new developments in the field. Our group has earlier optimized and evaluated the in vitro properties of two radiotracers,[89Zr]Zr-(oxinate)4 and [89Zr]Zr-DFO-NCS, for the radiolabelling of different cell types. Here, we performed a microPET study to assess the in vivo biodistribution of cells in rats using these two radiotracers. Human decidual stromal cells (hDSC) and rat macrophages (rMac) were radiolabelled with [89Zr]Zr-(oxinate)4 or [89Zr]Zr-DFO-NCS. Rats were intravenously injected with radiolabelled cells, and the in vivo biodistribution was monitored with microPET/CT imaging for up to day 7. Organ uptake was evaluated and presented as a percentage of injected activity per gram tissue (%IA/g) and total absorbed organ doses (mSv/MBq).ResultsThe biodistribution in vivo showed an immediate uptake in the lungs. Thereafter, [89Zr]Zr-(oxinate)4 labelled cells migrated to the liver, while the signal from [89Zr]Zr-DFO-NCS labelled cells lingered in the lungs. The differences in the in vivo behaviour for the same cell type appeared related to the radiotracer labelling. After 24 h, [89Zr]Zr-(oxinate)4 labelled cells had over 70% higher liver uptake for both hDSC and rMac compared to [89Zr]Zr-DFO-NCS labelled cells, whereas [89Zr]Zr-DFO-NCS labelled cells showed over 60% higher uptake in the lungs compared to [89Zr]Zr-(oxinate)4 labelled cells. This difference in both lung and liver uptake continued until day 7. Dosimetry calculations showed a higher effective dose (mSv/MBq) for [89Zr]Zr-DFO-NCS compared to [89Zr]Zr-(oxinate)4, for both cell types. Although the bone uptake was higher for [89Zr]Zr-(oxinate)4 labelled cells, the prolonged uptake in the lungs contributed to a significant crossfire to bone marrow resulting in a higher bone dose.ConclusionThe [89Zr]Zr-DFO-NCS labelled cells suggest a prolonged accumulation in the lungs, while [89Zr]Zr-(oxinate)4 suggests quicker clearance of the lungs followed by accumulation in the liver. Accumulation of radiolabelled cells in the liver corresponds to other cell-tracking methods. Further studies are required to determine the actual location of the [89Zr]Zr-DFO-NCS labelled cell.

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89Zr-trastuzumab PET supports clinical decision making in breast cancer patients, when HER2 status cannot be determined by standard work up.

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<sup>89</sup>Zr-trastuzumab PET supports clinical decision making in breast cancer patients, when HER2 status cannot be determined by standard work up.

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