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Rapid nanobody-based imaging of mesothelin expressing malignancies compatible with blocking therapeutic antibodies
Abdennour Benloucif1, Damien Meyer1, Laure Balasse2,3
1Aix Marseille Univ, CNRS, INSERM, Institut Paoli-Calmettes, CRCM, Marseille, France.
Introduction:
Mesothelin (MSLN) is overexpressed in a wide variety of cancers with few therapeutic options and has recently emerged as an attractive target for cancer therapy, with a large number of approaches currently under preclinical and clinical investigation. In this respect, developing mesothelin specific tracers as molecular companion tools for predicting patient eligibility, monitoring then response to mesothelin-targeting therapies, and tracking the evolution of the disease or for real-time visualisation of tumours during surgery is of growing importance.
Methods:
We generated by phage display a nanobody (Nb S1) and used enzymatic approaches were used to site-directed conjugate Nb S1 with either ATTO 647N fluorochrome or NODAGA chelator for fluorescence and positron emission tomography imaging (PET) respectively.
Results:
We demonstrated that Nb S1 displays a high apparent affinity and specificity for human mesothelin and demonstrated that the binding, although located in the membrane distal domain of mesothelin, is not impeded by the presence of MUC16, the only known ligand of mesothelin, nor by the therapeutic antibody amatuximab. In vivo experiments showed that both ATTO 647N and [68Ga]Ga-NODAGA-S1 rapidly and specifically accumulated in mesothelin positive tumours compared to mesothelin negative tumours or irrelevant Nb with a high tumour/background ratio. The ex vivo biodistribution profile analysis also confirmed a significantly higher uptake of Nb S1 in MSLN-positive tumours than in MSLNlow tumours.
Conclusion:
We demonstrated for the first time the use of an anti-MSLN nanobody as PET radiotracer for same day imaging of MSLN+ tumours, targeting an epitope compatible with the monitoring of amatuximab-based therapies and current SS1-derived-drug conjugates.
Insights
We developed a novel nanobody tracer for mesothelin (MSLN) imaging. This tracer enables precise visualization of MSLN-positive tumors, aiding in patient selection and monitoring of targeted cancer therapies.
Area of Science:
- Oncology
- Molecular Imaging
- Nanotechnology
Background:
- Mesothelin (MSLN) is a cancer target with limited therapeutic options.
- Developing MSLN-specific tracers is crucial for personalized cancer therapy and surgical guidance.
Purpose of the Study:
- To generate and evaluate a nanobody-based tracer for mesothelin (MSLN) imaging.
- To assess the tracer's utility in predicting patient eligibility and monitoring MSLN-targeting treatments.
Main Methods:
- Phage display was used to generate a mesothelin-specific nanobody (Nb S1).
- Nb S1 was conjugated to a fluorochrome (ATTO 647N) or a chelator (NODAGA) for imaging.
- Fluorescence and positron emission tomography (PET) imaging were performed in vivo and ex vivo.
Main Results:
- Nb S1 demonstrated high affinity and specificity for human MSLN, independent of MUC16 or amatuximab.
- In vivo imaging showed rapid and specific accumulation of Nb S1 tracers in MSLN-positive tumors.
- High tumor-to-background ratios were achieved, confirming effective tumor visualization.
Conclusions:
- An anti-MSLN nanobody serves as an effective PET radiotracer for same-day imaging of MSLN-positive tumors.
- The tracer targets an epitope compatible with current MSLN-targeting therapies, including amatuximab-based treatments.
