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The Bioconjugation and Radiosynthesis of 89Zr-DFO-labeled Antibodies
Published on: February 12, 2015
Labeling anti-HER2/neu monoclonal antibodies with 111In and 90Y using a bifunctional DTPA chelating agent
Michael J Blend1, Jerry J Stastny, Steven M Swanson
1Department of Radiology, Section of Nuclear Medicine, College of Medicine, University of Illinois at Chicago, 60607, USA.
Abstract:
The goal of this investigation was to develop stable radioimmunoconjugates (RICs) of anti-HER2/neu monoclonal antibodies (MoAbs) for imaging and therapy in an animal model bearing human breast tumor xenografts that express normal (MCF-7 cells) and increased amounts of HER2/neu receptors (HCC-1954, BT-474, SKBR-3 cells) on their cell surface membranes. Pharmacy-grade Herceptin, a murine anti-HER2/neu MoAb, and nonspecific mouse IgG protein were conjugated with the recently developed DTPA linker known as CHX-A"-DTPA. These immunoconjugates were labeled with (111)InCl(3) and (90)YCl(3). Using a molar excess of 10:1 CHX-A"-DTPA to immunoglobulin, average specific activities of 1.87 microCi (111)In/microg RIC and 2.71 microCi (90)Y/microg RIC were obtained. The purity of RICs was 96%+ for (111)In and 99%+ for (90)Y. Stability in human plasma at 37 degrees C for both RICs ranged from 98% at 24 h to 85% at 96 h. Binding capacity of the RICs was tested with human cancer cell lines MCF-7, HCC-1954, BT-474, and SKBR-3. Using (111)In-labeled nonspecific IgG protein as a control, (111)In-Herceptin RIC was found to bind to MCF-7 cells with a ratio of 2.5:1 and to SKBR-3 cells with a ratio of 85:1 after 3 h of incubation. (111)In anti-HER2/neu RIC bound to MCF-7 cells with a ratio of 6:1 and to SKBR-3 cells with a ratio of 115:1 after 3 h of incubation. (90)Y-anti-HER2/neu RIC bound 10-times greater to BT-474 cells than to MCF-7 cells. Thus, these MoAbs can be labeled with (111)In and (90)Y using the CHX-A"-DTPA linker. The resulting RICs ((111)In- and (90)Y-anti HER2/neu antibodies) are stable and bind significantly to HER2 overexpressing tumor cell lines.
Insights
Stable radioimmunoconjugates (RICs) of anti-HER2/neu monoclonal antibodies (MoAbs) were developed for breast cancer imaging and therapy. These RICs demonstrate excellent stability and specific binding to HER2-overexpressing tumor cells.
Area of Science:
- Oncology
- Radiochemistry
- Immunology
Background:
- HER2/neu receptor overexpression is a hallmark of aggressive breast cancers.
- Radioimmunoconjugates (RICs) offer targeted delivery of radioisotopes for imaging and therapy.
- Development of stable and effective RICs is crucial for clinical translation.
Purpose of the Study:
- To develop stable RICs using anti-HER2/neu monoclonal antibodies (MoAbs).
- To evaluate the stability and binding capacity of these RICs in HER2-expressing breast cancer models.
- To assess the potential of these RICs for targeted breast cancer imaging and therapy.
Main Methods:
- Pharmacy-grade Herceptin (anti-HER2/neu MoAb) and nonspecific mouse IgG were conjugated with CHX-A"-DTPA linker.
- Immunoconjugates were radiolabeled with Indium-111 ((111)In) and Yttrium-90 ((90)Y).
- RIC stability was assessed in human plasma, and binding affinity was evaluated using HER2-expressing human breast cancer cell lines (MCF-7, HCC-1954, BT-474, SKBR-3).
Main Results:
- High purity RICs were obtained with specific activities of 1.87 microCi (111)In/microg and 2.71 microCi (90)Y/microg.
- RICs exhibited excellent stability in human plasma, with 85-98% retention over 96 hours.
- (111)In- and (90)Y-labeled anti-HER2/neu RICs showed significantly higher binding to HER2-overexpressing cell lines compared to control IgG and MCF-7 cells.
Conclusions:
- The CHX-A"-DTPA linker enables stable radiolabeling of anti-HER2/neu MoAbs with (111)In and (90)Y.
- The resulting RICs are stable and demonstrate specific binding to HER2-overexpressing breast cancer cells.
- These findings support the potential of (111)In- and (90)Y-labeled anti-HER2/neu RICs for targeted breast cancer imaging and therapy.
