Selective Visualization of ROR1-Positive TNBC of the Mesenchymal-Like Subtype Using Peptide-Based ⁶⁸Ga-PET...

Area of Science:

• Oncology
• Radiochemistry
• Molecular Imaging

Background:

• Triple-negative breast cancer (TNBC) lacks effective molecular imaging targets.
• Receptor tyrosine kinase-like orphan receptor 1 (ROR1) is overexpressed in the mesenchymal-like (claudin-low) TNBC subtype.

Purpose of the Study:

• To develop and evaluate novel peptide-based radiotracers for imaging ROR1-positive TNBC.
• To assess the binding affinity, stability, and in vivo performance of the developed tracers.

Main Methods:

• Developed two linear peptide radiotracers (DR1, DR2) from anti-ROR1 antibody CDRs, conjugated with DOTA and labeled with 68Ga.
• Evaluated binding affinities (KD), in vitro stability in human serum, and in vivo clearance in mice.
• Performed micro-PET/CT imaging in MDA-MB-231 xenograft mouse models, including blocking studies.

Main Results:

• Both DR1 and DR2 showed nanomolar binding affinities.
• [68Ga]Ga-DOTA-DR2 demonstrated excellent in vitro stability and rapid in vivo clearance.
• Micro-PET/CT imaging showed rapid tumor visualization with high tumor uptake and tumor-to-muscle ratio, confirming ROR1-specific targeting.

Conclusions:

• [68Ga]Ga-DOTA-DR2 is a promising PET tracer for imaging ROR1-positive mesenchymal-like TNBC.
• Further optimization of this tracer could lead to improved diagnostic capabilities for TNBC.