Abstract P1-02-01: HER2/neu antibody-fluorophore conjugate for intraoperative detection of HER2-positive breast cancer

Background: Although advances in neoadjuvant and adjuvant treatments have led to enhanced survival in patients with HER2 positive breast cancer, intraoperative detection of residual disease and tumor margins (including HER2 positive DCIS) remain challenging. Real-time fluorescence imaging is being used during surgery to improve tumor visualization and identify margins. However, the lack of an approved intraoperative imaging agent that is specific for HER2 expressing cancers limits the utility of fluorescence-guided surgery (FGS) in this patient population. We examined the potential of using clinically approved anti-HER2 monoclonal antibodies (mAbs), trastuzumab and pertuzumab, for the development of fluorescent immunoconjugates dual-labeled with radioactivity to enable quantitative assessment.

Methods: Trastuzumab, and pertuzumab were conjugated to the near-infrared (NIR) fluorophore, IR800CW, and radiometal chelator, deferoxamine (DFO), to permit dual labeling with 89Zr (positron emitting radionuclide). To confirm retention of HER2 specificity and functionality, flow cytometry analysis of the dual-labeled immunoconjugates was performed in HER2+ (BT474, SKBR3), HER2 moderate (MCF7), and HER2− (MDA231) cell lines. Using the same cell lines, radioactive uptake studies were employed to quantitatively measure cellular uptake study using 89Zr with and without blocking doses of unlabeled mAb. In vivo optical imaging of each immunoconjugate and IgG controls was performed in BT474 and MCF7 xenografts in BALB/c (nu/nu) mice 48 hours post injection using the BrukerXtreme system.

Results: In vitro results confirmed retention of receptor mediated binding on both flow cytometry and radioactive analyses. As shown in Table 1, uptake of each immunoconjugate correlated with the degree of HER2 expression. Importantly, the addition of unlabeled mAb led to a 79-93% reduction in binding to cells with the highest HER2 expression (BT474 and SKBR3). In MDA231 cells binding of the immunoconjugates was similar to the IgG control and indicates low non-specific binding. In vivo and ex vivo analysis of HER2+ and HER2 moderate xenografts demonstrated prominent tumor uptake with minimal signal in non-clearance organs. As a result, tumor-to-muscle, tumor-to-fat pad, and tumor-to-lung ratios were >5, indicating excellent contrast in key regions where surgical excisions are performed clinically.

Table 1: Uptake of 89Zr-mAb-IR800 in breast cancer cell linesCell Lines% Uptake of 89Zr-PertuzumabPertuzumab Block (Unlabeled)% Uptake of 89Zr-TrastuzumabTrastuzumab Block (Unlabeled)% Uptake of 89Zr-IgGBT47449.2±14.83.7±0.036.9±5.84.6±2.61.3±0SKBR337.9±1.77.9±0.942.8±3.52.9±1.73.5±0.4MCF721.7±2.63.2±0.44.0±0.12.5±0.11.3±0.7MDA2311.9±0.40.8±0.31.0±0.31.9±0.51.3±0.7

Conclusion: This study demonstrates the potential utility of HER2-targeted FGS to improve tumor visualization, increase the likelihood of obtaining clean surgical margins, and ultimately reduce morbidity in patients with HER2 breast cancer.

Citation Format: Jo Simien, Julie Voss, A.M. Thompson, S.C. Ghosh, S. AghaAmiri, A. Azhdarinia, H.S. Tran-Cao. HER2/neu antibody-fluorophore conjugate for intraoperative detection of HER2-positive breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P1-02-01.

Design of peptide imaging agents for whole-body and intraoperative molecular imaging

Due to the growing toolkit of targeted contrast agents, molecular imaging continues to play a prominent role in the clinical care of cancer. Peptide-based imaging approaches are of particular significance due to their favorable pharmacokinetic properties, established manufacturing infrastructure, and documented clinical success in whole-body imaging. A logical extension of molecular imaging with peptides is to improve surgical outcomes in cancer through highly sensitive and specific probes which can be used intraoperatively. Advances in fluorescent imaging have resulted in various peptide labeling strategies with intraoperative indications. In this review, we focused on the evolving design of peptide imaging agents starting with the clinically used somatostatin targeting peptides. We then review the current synthetic approaches used for dual-labeled agent development and offer perspectives on optimal protection schemes that can be used for multimodal probe development.

Clinical response to targeted radionuclide therapy with multiple 500 mCi doses of 111In-pentetreotide in patients with progressive neuroendocrine tumors

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Background: Patients with advanced stage neuroendocrine tumors have limited therapeutic options. Previous treatments with doses up to 360 mCi per fraction have shown promising results in stabilizing progressive disease. The intent of this study was to evaluate the efficacy and safety of 2 consecutive 500 mCi doses of 111In-pentetreotide in patients with progressive neuroendocrine tumors. This study was performed according to an FDA approved IND application. Methods: In a non-randomized study, 18 patients (13 men, 5 women) with an average age of 59 (ranging from 41–83 yr.) received 2 cycles of 500 mCi 111In-pentetreotide infused over 3 to 6 hours (avg. cumulative dose range: 955–1006.1 mCi). All patients had progressive neuroendocrine tumors and failed first line therapy. All patients had grade 3 to 5 uptake in the tumors in the pre-therapy diagnostic 111In-pentetreotide scan. The primary endpoint was clinical, metabolic and imaging response using RECIST criteria. Early and long term hematological, renal and hepatic toxicities during the average follow up period of 9.87 months (range 3.93 to 17.23 months) was performed using NCI Common Toxicities criteria. Results: Sixteen out of 18 patients with previously progressive disseminated neuroendocrine disease achieved stable disease by imaging criteria. Metabolic response defined as 25% or more decline in Chromogranin or other markers was achieved in 72% of the patients. Clinical response defined by Functional Living Index (FLI) questionnaire and physical exam was achieved in 84% of the patients. Ten patients (55%) had grade I or II hematological toxicities, one patient had grade III thrombocytopenia, with nadir mean of 5 weeks after therapy. None of the patients required supportive therapy. Duration of hematological toxicities ranged from 1–6 weeks). One patient had grade II liver toxicity which appeared 4 weeks after therapy and resolved on week 5. No renal toxicity was observed during the follow-up period. Conclusions: Multiple 500 mCi doses of 111In-pentetreotide therapy are effective in patients with progressive disseminated neuroendocrine tumors. Safety profile of this regimen suggests the opportunity for non-myeloablative dose escalation.

No significant financial relationships to disclose.

In vivo and in vitro measurement of apoptosis in breast cancer cells using 99mTc-EC-annexin V

OBJECTIVE

The purpose of this study was to develop an imaging technique to measure and monitor tumor cells undergoing programmed death caused by radiation and chemotherapy using 99mTc-EC-annexin V. Annexin V has been used to measure programmed cell death both in vitro and in vivo. Assessment of apoptosis would be useful to evaluate the efficacy and mechanisms of therapy and disease progression or regression.

METHODS

Ethylenedicysteine (EC) was conjugated to annexin V using sulfo-N-hydroxysuccinimide and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide-HCl as coupling agents. The yield of EC-annexin V was 100%. In vitro cellular uptake, pre- and post-radiation (10-30 Gy) and paclitaxel treatment, was quantified using 99mTc-EC-annexin V. Tissue distribution and planar imaging of 99mTc-EC-annexin V were determined in breast tumor-bearing rats at 0.5, 2, and 4 hrs. To demonstrate in vivo cell apoptosis that occurred during chemotherapy, a group of rats was treated with paclitaxel and planar imaging studies were conducted at 0.5-4 hrs. Computer outlined region of interest (ROI) was used to quantify tumor uptake on day 3 and day 5 post-treatment.

RESULTS

In vitro cellular uptake showed that there was significantly increased uptake of 99mTc-EC-annexin V after irradiation (10-30 Gy) and paclitaxel treatment. In vivo biodistribution of 99mTc-EC-annexin in breast tumor-bearing rats showed increased tumor-to-blood, tumor-to-lung and tumor-to-muscle count density ratios as a function of time. Conversely, tumor-to-blood count density ratios showed a time-dependent decrease with 99mTc-EC in the same time period. Planar images confirmed that the tumors could be visualized clearly with 99mTc-EC-annexin. There was a significant difference of ROI ratios between pre- and post-paclitaxel treatment groups at 2 and 4 hrs post injection.

CONCLUSION

The results indicate that apoptosis can be quantified using 99mTc-EC-annexin and that it is feasible to use 99mTc-EC-annexin to image tumor apoptosis.