Updated project metadata. To demonstrate the on-target binding of the MAGE-A4 antibody to the target HLAp GVYDGREHTV, we developed a reverse immunopeptidomics strategy that uses the HLAp-targeting antibody as a bait to enrich interacting HLAp from A375 xenografts. For this purpose, we immobilized the IgG-format of the MAGE-A4 TCR-like antibody on Protein A beads by cross-linking, and exposed the molecule to the solubilized proteome, including membrane bound HLAp, of the A375 xenografts. We subsequently eluted the interacting HLAp bound to the MAGE-A4 antibody and purified the HLA-associated peptides through a 5 kDa molecular weight filter before liquid chromatography tandem mass spectrometry analysis for sequence determination.