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Updated: Aug 5, 2026
Analyzing Tumor and Tissue Distribution of Target Antigen Specific Therapeutic Antibody
Published on: May 16, 2020
Imaging of ROR1 expression in tumors using radiolabeled affibody molecules
Cornelia Westerberg1, Tianqi Xu2, Maria Marth1
1Department of Protein Science, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, 100 44, Stockholm, Sweden.
Purpose:
Receptor tyrosine kinase-like orphan receptor 1 (ROR1) is an attractive molecular target for anti-tumor therapies undergoing late-stage clinical development. Quantitative imaging of ROR1 expression could enable identification of patients likely to respond to such treatments. This study aimed to assess the feasibility of specific in vivo imaging of ROR1 using radiolabeled affibody molecules.
Methods:
The affibody molecule ZROR1:A10, with high affinity for human (4 nM) and murine (2 nM) ROR1, was labeled with indium-111 using a DOTA chelator. In vitro binding specificity, affinity, and cellular processing were evaluated using a panel of ROR1-expressing cell lines. The affibody [111In]In-DOTA-Zcov19s, which does not bind ROR1, served as a nonspecific control. The biodistribution of [111In]In-DOTA-ZROR1:A10 and [111In]In-DOTA-Zcov19s was measured in immunodeficient mice bearing ROR1-positive tumors, with ROR1-negative Ramos xenografts used as an additional specificity control.
Results:
[111In]In-DOTA-ZROR1:A10 bound specifically to ROR1-expressing cells, with significantly higher uptake than [111In]In-DOTA-Zcov19s. The apparent equilibrium dissociation constant for ROR1 binding in vitro was 1-4 nM. Tumor uptake of [111In]In-DOTA-ZROR1:A10 in MDA-MB-468 xenografts was saturable and significantly (p < 0.05) higher than in Ramos tumors, as well as higher than uptake of the control affibody. At 4 h post‑injection of 1 µg (50 µg/kg), tumor‑to‑blood, tumor‑to‑bone, and tumor‑to‑muscle ratios were 14 ± 6, 19 ± 6, and 11 ± 1, respectively. Micro-SPECT/CT imaging clearly visualized ROR1‑positive tumors and discriminated them from ROR1‑negative xenografts.
Conclusion:
The preclinical evaluation shows that visualization of ROR1-expressing tumors using a radiolabeled affibody molecule is feasible.
Insights
This study demonstrates that radiolabeled affibody molecules can successfully visualize Receptor tyrosine kinase-like orphan receptor 1 (ROR1) in tumors. This imaging approach shows promise for identifying patients who may benefit from ROR1-targeted anti-cancer therapies.
Area of Science:
- Oncology
- Molecular Imaging
- Radiochemistry
Background:
- Receptor tyrosine kinase-like orphan receptor 1 (ROR1) is a key target for novel anti-cancer therapies.
- Accurate imaging of ROR1 expression is crucial for patient selection in clinical trials.
Purpose of the Study:
- To evaluate the feasibility of in vivo imaging of ROR1 using radiolabeled affibody molecules.
- To assess the specificity and efficacy of a novel affibody-based imaging agent.
Main Methods:
- The affibody molecule ZROR1:A10 was labeled with indium-111.
- In vitro binding assays were performed on ROR1-expressing cell lines.
- Biodistribution and micro-SPECT/CT imaging were conducted in mice bearing ROR1-positive and ROR1-negative tumors.
Main Results:
- The radiolabeled affibody [111In]In-DOTA-ZROR1:A10 demonstrated specific binding to ROR1-expressing cells and tumors.
- High tumor-to-background ratios were achieved, with clear visualization of ROR1-positive tumors via micro-SPECT/CT.
- Tumor uptake was saturable and significantly higher compared to control groups.
Conclusions:
- Preclinical studies confirm the feasibility of visualizing ROR1-expressing tumors using radiolabeled affibody molecules.
- This imaging approach holds potential for guiding ROR1-targeted cancer therapies.
