Soluble T cell receptor (TCR)-based T cell engagers (TCEs) offer a powerful strategy for targeting otherwise inaccessible intracellular cancer antigens via peptide-HLA recognition and redirected T cell killing. However, native TCR affinities are far too weak for therapeutic use and require substantial affinity maturation to achieve clinical potency. Adimab scientists developed a high-throughput yeast-based platform to engineer soluble TCRs for use in TCR×CD3 bispecific TCEs targeting intracellular antigens via peptide–HLA (pHLA). This work demonstrates how iterative yeast-based engineering can rapidly generate high-affinity, highly specific TCRs suitable for TCE formats. 

Approach and outcomes 

• A yeast-based system was employed for both presentation and secretion of TCR-Fc constructs, supporting high-throughput selection, expression, purification, and kinetic characterization. 

• Affinity maturation of the cancer-targeting 1G4 TCR through iterative CDR diversification and FACS selection produced variants with >30,000-fold improved affinity compared with the parent, while requiring fewer mutations than a high-affinity clinical control. 

• Library-derived TCR variants retained selective peptide recognition and showed fewer off-target interactions than a related clinical control when tested against peptide-diversified pHLA libraries. 

• When reformatted into clinically validated TCE bispecific formats, library-derived variants mediated potent T cell activation and target cell killing equivalent to the clinical benchmark. 

Why it matters

The results show that Adimab's high-throughput yeast-based platform overcomes the traditional limitations of soluble TCRs by delivering high-affinity, minimally mutated variants with improved specificity. The platform enables rapid generation of TCR-based T cell engagers that combine potent cytotoxic activity with reduced off-target risk, supporting the development of therapies against intracellular targets. 

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