Predicting peptide–HLA binding is crucial for advancing immunotherapy; however, current models face several challenges, including peptide length variability, HLA sequence similarity, and a lack of experimentally validated negative data. To address these issues, we present PHLA-SiNet, an efficient pipeline that combines innovative representations with a lightweight architecture. PHLA-SiNet introduces three key components: (1) ESM-Pep, a peptide representation derived from a pre-trained language model (ESM), enabling flexible and training-free embedding of variable-length peptides; (2) IC-HLA, an HLA representation that captures allele-specific discriminative features using information content from binding and non-binding peptides; and (3) SiNet, a Siamese neural network that aligns peptide and HLA embeddings, bringing true binders closer in feature space. Prioritizing sensitivity—essential for reliably …