Therapeutic soluble T cell receptors (TCRs) can target intracellular antigens via peptide-HLA (pHLA) recognition, but natural TCRs often bind their targets weakly and express poorly, representing a key bottleneck for drug development. Adimab scientists address these limitations through high-throughput screening of the first fully human synthetic TCR libraries built in yeast to discover potent, specific, and manufacturable soluble TCRs at scale.  

Approach and results 

• High-frequency human TCR α/β variable domains were paired with large CDR3α and CDR3β diversities to construct repertoire-scale synthetic libraries in yeast. 
• Synthetic libraries were subjected to iterative selections under stringent conditions to enrich TCRs with highly specific and high-affinity binding to a model viral pHLA target.

• Compared with antigen-matched natural repertoire-derived TCRs, library-derived TCRs showed markedly improved monovalent affinities (e.g., KD 58 nM vs 1.1 µM) and superior mammalian expression titers and quality.  

• Sequence analyses indicated that synthetic library-derived TCRs retained natural repertoire-like features (e.g., TRBV19 predominance) while incorporating distinct CDR3β motifs at the pHLA interface that may account for their enhanced affinities.  

• Next steps include defining the peptide specificities of library- and natural repertoire–derived TCRs using peptide-diversified pHLA libraries built in yeast, combined with off-target prediction and validation.  

Overall, our data show that a fully human synthetic TCR library built in yeast reproducibly delivers soluble TCRs that surpass those isolated from natural repertoires in both affinity and mammalian expression while preserving sequence hallmarks of naturally derived TCRs. The approach directly addresses long-standing bottlenecks in the development of TCR-based therapeutics.  

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