T. H. Oude Munnink

Biodistribution of 89Zr-trastuzumab and PET Imaging of HER2-Positive Lesions in Patients With Metastatic Breast Cancer

We performed a feasibility study to determine the optimal dosage and time of administration of the monoclonal antibody zirconium‐89 (89Zr)‐trastuzumab to enable positron emission tomography (PET) imaging of human epidermal growth factor receptor 2 (HER2)‐positive lesions. Fourteen patients with HER2‐positive metastatic breast cancer received 37 MBq of 89Zr‐trastuzumab at one of three doses (10 or 50 mg for those who were trastuzumab‐naive and 10 mg for those who were already on trastuzumab treatment). The patients underwent at least two PET scans between days 2 and 5. The results of the study showed that the best time for assessment of 89Zr‐trastuzumab uptake by tumors was 4–5 days after the injection. For optimal PET‐scan results, trastuzumab‐naive patients required a 50 mg dose of 89Zr‐trastuzumab, and patients already on trastuzumab treatment required a 10 mg dose. The accumulation of 89Zr‐trastuzumab in lesions allowed PET imaging of most of the known lesions and some that had been undetected earlier. The relative uptake values (RUVs) (mean ± SEM) were 12.8 ± 5.8, 4.1 ± 1.6, and 3.5 ± 4.2 in liver, bone, and brain lesions, respectively, and 5.9 ± 2.4, 2.8 ± 0.7, 4.0 ± 0.7, and 0.20 ± 0.1 in normal liver, spleen, kidneys, and brain tissue, respectively. PET scanning after administration of 89Zr‐trastuzumab at appropriate doses allows visualization and quantification of uptake in HER2‐positive lesions in patients with metastatic breast cancer.

Molecular imaging of breast cancer.

Molecular imaging of breast cancer can potentially be used for breast cancer screening, staging, restaging, response evaluation and guiding therapies. Techniques for molecular breast cancer imaging include magnetic resonance imaging (MRI), optical imaging, and radionuclide imaging with positron emission tomography (PET) or single photon emission computed tomography (SPECT). This review focuses on PET and SPECT imaging which can provide sensitive serial non invasive information of tumor characteristics. Most clinical data are gathered on the visualization of general processes such as glucose metabolism with the PET-tracer [(18)F]fluorodeoxyglucose (FDG) and DNA synthesis with [18F]fluoro-L-thymidine (FLT). Increasingly more breast cancer specific targets are imaged such as the estrogen receptor (ER), growth factors and growth factor receptors. Imaging of the ER with the PET tracer 16-alpha-[(18)F]fluoro-17-beta-estradiol (FES) has shown a good correlation between FES tumor uptake and ER density. (111)In-trastuzumab SPECT to image the human epidermal growth factor receptor 2 (HER2) showed that in most patients with metastatic HER2 overexpressing disease more lesions were detected than with conventional staging procedures. The PET tracer (89)Zr-trastuzumab showed excellent, quantifiable, and specific tumor uptake. (111)In-bevacizumab for SPECT and (89)Zr-bevacizumab for PET-imaging have been developed for vascular endothelial growth factor (VEGF) imaging as an angiogenic marker. Lastly, tracers for the receptors EGFR, IGF-1R, PDGF-betaR and the ligand TGFbeta are under development. Although molecular imaging of breast cancer is still not commonly used in daily clinical practice, its application portfolio is expanding rapidly.

Bevacizumab-Induced Normalization of Blood Vessels in Tumors Hampers Antibody Uptake

In solid tumors, angiogenesis occurs in the setting of a defective vasculature and impaired lymphatic drainage that is associated with increased vascular permeability and enhanced tumor permeability. These universal aspects of the tumor microenvironment can have a marked influence on intratumoral drug delivery that may often be underappreciated. In this study, we investigated the effect of blood vessel normalization in tumors by the antiangiogenic drug bevacizumab on antibody uptake by tumors. In mouse xenograft models of human ovarian and esophageal cancer (SKOV-3 and OE19), we evaluated antibody uptake in tumors by positron emission tomographic imaging 24 and 144 hours after injection of (89)Zr-trastuzumab (SKOV-3 and OE19), (89)Zr-bevacizumab (SKOV-3), or (89)Zr-IgG (SKOV-3) before or after treatment with bevacizumab. Intratumor distribution was assessed by fluorescence microscopy along with mean vessel density (MVD) and vessel normalization. Notably, bevacizumab treatment decreased tumor uptake and intratumoral accumulation compared with baseline in the tumor models relative to controls. Bevacizumab treatment also reduced MVD in tumors and increased vessel pericyte coverage. These findings are clinically important, suggesting caution in designing combinatorial trials with therapeutic antibodies due to a possible reduction in tumoral accumulation that may be caused by bevacizumab cotreatment.

Therapeutic drug monitoring of monoclonal antibodies in inflammatory and malignant disease: Translating TNF‐α experience to oncology

Lack of response to monoclonal antibodies (mAbs) has been associated with inadequate mAb serum concentrations. Therapeutic drug monitoring (TDM) of mAbs has the potential to guide to more effective dosing in individual patients. This review discusses the mechanisms responsible for interpatient variability of mAb pharmacokinetics, summarizes exposure‐response data of mAbs used in inflammatory and malignant disease, presents current evidence of mAb‐TDM in inflammatory disease, and provides hurdles and required future steps for further implementing mAb‐TDM.

Abstract 5303: Serial HER2-PET imaging with 89 Zr-trastuzumab-F(ab’) 2 of lapatinib and 17AAG treated mice bearing SKBR3 xenografts

Background: Understanding molecular responses involved in human epidermal growth factor receptor-2 (HER2) targeted drugs may improve treatment of HER2 positive breast cancer. In vivo assessment of effects on HER2 expression is of value in this setting. The EGFR/HER2 tyrosine kinase inhibitor lapatinib inhibits HER2 signaling and stabilizes HER2 at the cell membrane, while the heat shock protein-90 (HSP90) inhibitor 17AAG degrades HER2/EGFR. We therefore evaluated the effect on HER2 dynamics in vivo with 89 Zr-trastuzumab-F(ab’) 2 HER2-PET imaging in human tumor bearing mice treated with lapatinib and 17AAG. Materials and methods: Effects of lapatinib and 17AAG on EGFR and HER2 membrane expression were evaluated in vitro in the human breast cancer cell line SKBR3 using flow cytometry. In vivo effects on HER2 expression were evaluated with 89 Zr-trastuzumab-F(ab’) 2 μPET imaging in SKBR3 xenograft bearing mice. 89 Zr-trastuzumab-F(ab’) 2 (5 MBq; 20 μg) was injected two times with a 7 day interval and μPET imaging was performed 24 hours after tracer injection. Lapatinib was dosed 100 mg/kg/day orally for 6 days, starting 1 day after the first μPET scan. 17AAG was dosed 3×50 mg intraperitoneal in the 24 hours prior to the second tracer injection. A non-treated group of mice served as control and for validation of 89 Zr-trastuzumab-F(ab’) 2 μPET imaging. Imaging data were compared with ex vivo biodistribution analysis, immunohistochemistry, and with an in vitro HER2 internalization experiment. Results: On flow cytometry, lapatinib induced upregulation of EGFR (+70%; P = 0.0011), but not HER2 (+19%; P = 0.1275). 17AAG treatment lowered both EGFR (−41%; P = 0.016) and HER2 (−76%; P = 0.022) expression. This EGFR/HER2 reduction by 17AAG was inhibited by lapatinib. In vivo, 89 Zr-trastuzumab-F(ab’) 2 tumor uptake on the second μPET scan was lowered by lapatinib (−32%; P = 0.00004), 17AAG (−34%; P = 0.0022) and the lapatinib plus 17AAG combination (−53%; P = 0.011). 89 Zr-trastuzumab-F(ab’) 2 tumor uptake in mice treated with lapatinib plus 17AAG was lower than with either lapatinib or 17AAG alone (P = 0.0043 and P = 0.0022, respectively). In vitro, 89 Zr-trastuzumab-F(ab’) 2 internalization was reduced by lapatinib (−25%; P = 0.0022), explaining the lower 89 Zr-trastuzumab-F(ab’) 2 tumor uptake after lapatinib. Conclusion: 89 Zr-trastuzumab-F(ab’) 2 μPET visualized treatment induced impact on HER2 expression and -dynamics. Lapatinib inhibited HER2 internalization, and thereby decreased 89 Zr-trastuzumab-F(ab’) 2 tumor uptake. HSP90 inhibition lowered HER2 membrane expression and thereby 89 Zr-trastuzumab-F(ab’) 2 tumor uptake. This knowledge on HER2 dynamics ameliorates understanding of efficacy of several combinations of HER2 targeted agents. Supported by grant 2007-3739 of the Dutch Cancer Society. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5303. doi:10.1158/1538-7445.AM2011-5303