Therapeutic antibodies—like other biotherapeutic proteins—can trigger unwanted immune responses, impacting both drug efficacy and patient safety. Early assessment of immunogenicity risk is critical to optimize drug design and avoid costly late-stage failures. ImmuneSpec’s high-sensitive MAPPs (MHC-associated peptide proteomics) assay offers direct insights into T cell epitope presentation by antigen-presenting cells (APCs). It reveals which parts of a therapeutic protein are truly displayed on MHC molecules (after uptake and lysosomal processing), pinpointing the sequences that may trigger immune responses. Our data correlate with clinical immunogenicity outcomes, supporting selection and optimization of biotherapeutics for improved safety and efficacy.