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Updated: May 16, 2026
Polymalic Acid-based Nano Biopolymers for Targeting of Multiple Tumor Markers: An Opportunity for Personalized Medicine?
Published on: June 13, 2014
Targeting breast carcinoma with radioiodinated anti-HER2 Nanobody
Marek Pruszynski1, Eftychia Koumarianou, Ganesan Vaidyanathan
1Department of Radiology, Duke University Medical Center, Durham, NC 27710, USA.
Introduction:
With a molecular weight an order of magnitude lower than antibodies but possessing comparable affinities, Nanobodies (Nbs) are attractive as targeting agents for cancer diagnosis and therapy. An anti-HER2 Nb could be utilized to determine HER2 status in breast cancer patients prior to trastuzumab treatment. This provided motivation for the generation of HER2-specific 5F7GGC Nb, its radioiodination and evaluation for targeting HER2 expressing tumors.
Methods:
5F7GGC Nb was radioiodinated with ¹²⁵I using Iodogen and with ¹³¹I using the residualizing agent N(ɛ)-(3-[¹³¹I]iodobenzoyl)-Lys⁵-N(α)-maleimido-Gly¹-GEEEK ([¹³¹I]IB-Mal-D-GEEEK) used previously successfully with intact antibodies. Paired-label internalization assays using BT474M1 cells and tissue distribution experiments in athymic mice bearing BT474M1 xenografts were performed to compare the two labeled Nb preparations.
Results:
The radiochemical yields for Iodogen and [¹³¹I]IB-Mal-D-GEEEK labeling were 83.6±5.0% (n=10) and 59.6±9.4% (n=15), respectively. The immunoreactivity of labeled proteins was preserved as confirmed by in vitro and in vivo binding to tumor cells. Biodistribution studies showed that Nb radiolabeled using [¹³¹I]IB-Mal-D-GEEEK, compared with the directly labeled Nb, had a higher tumor uptake (4.65±0.61% ID/g vs. 2.92±0.24% ID/g at 8h), faster blood clearance, lower accumulation in non-target organs except kidneys, and as a result, higher concomitant tumor-to-blood and tumor-to-tissue ratios.
Conclusions:
Taken together, these results demonstrate that 5F7GGC anti-HER2 Nb labeled with residualizing [¹³¹I]IB-Mal-D-GEEEK had better tumor targeting properties compared to the directly labeled Nb suggesting the potential utility of this Nb conjugate for SPECT (¹²⁹I) and PET imaging (¹²⁴I) of patients with HER2-expressing tumors.
Insights
Nanobodies (Nbs) offer a promising alternative to antibodies for cancer imaging. A novel residualizing radiolabeling method significantly improved the tumor targeting of an anti-HER2 Nanobody, enhancing its potential for clinical applications.
Area of Science:
- Biotechnology and Nanomedicine
- Molecular Imaging and Diagnostics
- Oncology Therapeutics
Background:
- Nanobodies (Nbs), smaller than antibodies but with comparable affinities, are valuable for cancer diagnosis and therapy.
- An anti-HER2 Nanobody can assess HER2 status in breast cancer patients before trastuzumab treatment.
- This study focused on developing and evaluating a HER2-specific Nanobody (5F7GGC) for targeting HER2-expressing tumors.
Purpose of the Study:
- To compare two radioiodination methods for the HER2-specific 5F7GGC Nanobody.
- To evaluate the in vitro and in vivo tumor targeting capabilities of the differently labeled Nanobodies.
- To assess the potential of the optimized Nanobody conjugate for SPECT and PET imaging.
Main Methods:
- Radioiodination of 5F7GGC Nanobody using Iodogen (¹²⁵I) and a residualizing agent ([¹³¹I]IB-Mal-D-GEEEK).
- Paired-label internalization assays using BT474M1 cells.
- Tissue distribution experiments in athymic mice bearing BT474M1 xenografts.
Main Results:
- Radiochemical yields were 83.6±5.0% for Iodogen and 59.6±9.4% for [¹³¹I]IB-Mal-D-GEEEK.
- Both labeling methods preserved Nanobody immunoreactivity.
- The residualizing [¹³¹I]IB-Mal-D-GEEEK labeled Nanobody showed higher tumor uptake (4.65±0.61% ID/g vs. 2.92±0.24% ID/g at 8h), faster blood clearance, and improved tumor-to-tissue ratios compared to direct labeling.
Conclusions:
- The 5F7GGC anti-HER2 Nanobody labeled with residualizing [¹³¹I]IB-Mal-D-GEEEK exhibits superior tumor targeting properties.
- This optimized Nanobody conjugate demonstrates significant potential for SPECT and PET imaging of HER2-expressing tumors.
- The findings support the clinical utility of this Nanobody conjugate for personalized cancer diagnostics and potentially therapy.
