Dual B- and T-cell de-immunization of recombinant immunotoxin targeting mesothelin with high cytotoxic activity

Area of Science:

• Oncology
• Immunology
• Protein Engineering

Background:

• Recombinant immunotoxins (RITs) are engineered proteins for cancer therapy, combining cancer-targeting Fv fragments with toxic payloads.
• Clinical application of RITs is hindered by their immunogenicity, which elicits immune responses against the therapeutic agent.

Purpose of the Study:

• To develop a non-immunogenic RIT targeting mesothelin, a protein highly expressed in mesothelioma and other cancers.
• To engineer a novel RIT, LMB-T14, with reduced B- and T-cell epitopes to minimize immune reactions.

Main Methods:

• Systematic introduction of mutations to suppress B-cell and T-cell epitopes in an existing immunotoxin.
• Assessment of antigenicity via human anti-sera binding and T-cell activation assays.
• Evaluation of cytotoxicity against mesothelioma cell lines and in vivo efficacy in a mesothelin-expressing xenograft model.

Main Results:

• The engineered protein, LMB-T14, exhibited significantly reduced binding to human anti-sera and diminished T-cell activation.
• LMB-T14 demonstrated potent cytotoxicity against patient-derived mesothelioma cells and cancer cell lines.
• Complete tumor remission was achieved in a mesothelin-expressing xenograft model treated with LMB-T14.

Conclusions:

• The de-immunization strategy successfully created a non-immunogenic RIT (LMB-T14) with potent anti-cancer activity.
• LMB-T14 shows promise as a novel therapeutic agent for mesothelin-expressing cancers.
• The approach of de-immunizing therapeutic proteins by reducing epitopes is broadly applicable to other protein-based therapies.