Researchers unveiled Pepyrus, a platform that uses user‑defined peptide libraries produced in Escherichia coli to enhance mass‑spectrometry detection of HLA‑bound tumor peptides, improving sensitivity for tumor antigen discovery. The approach enables targeted, high‑throughput identification of neoantigens and low‑abundance tumor peptides that are often missed by conventional immunopeptidomics. Pepyrus combines synthetic biology for scalable peptide library production with optimized MS workflows; the team reported that the platform substantially increases identification rates of tumor‑derived peptides and facilitates downstream antigen validation for immunotherapy development. The method could accelerate neoantigen discovery pipelines used for personalized cancer vaccines and T‑cell receptor therapy target selection, while lowering the barrier for labs to build bespoke immunopeptidomic assays. Next steps: broader benchmarking against existing immunopeptidomics tools, adoption by translational labs, and integration with antigen validation workflows.