HDX-MS-Guided computational modeling for rapid and accurate antibody-antigen interface mapping.

Accurate mapping of paratopes and epitopes at antibody-antigen (Ab-Ag) interfaces is essential for the rational design of therapeutic antibodies in early drug development. Traditional methods for determining high-resolution Ab-Ag complex structures, such as X-ray crystallography and cryo-electron microscopy, are labor-intensive and require substantial time and resources. Although recent computational approaches have increased throughput, prediction accuracy and reliability remain limited, particularly without experimental structural constraints. Here, we present a hydrogen-deuterium exchange mass spectrometry (HDX-MS)-guided structural modeling workflow for efficient and accurate epitope and paratope mapping across three prospective case studies in therapeutic protein discovery and engineering. Across these systems, peptide-level HDX-MS data were sufficient to guide docking and structural modeling, whereas targeted electron transfer dissociation (ETD) HDX-MS was applied in one system as a higher-resolution, orthogonal approach to further localize critical binding residues. The workflow was applied to diverse Ab-Ag architectures spanning Fab and VHH binders and homodimeric and heterodimeric antigen ectodomains, and HDX-MS data were integrated with HADDOCK, AlphaFold2, and Protenix to generate Ab-Ag complex models. Comparison with subsequently obtained in-house X-ray crystal structures, used here as orthogonal high-resolution reference structures, showed strong agreement in overall binding orientation and interface placement. These results demonstrate the robustness and practical utility of this integrative approach for structure-informed antibody engineering in therapeutic protein discovery.