Structural and antigen-binding surface definition of an anti-CD93 monoclonal antibody for the treatment of degenerative vascular eye diseases.

CD93 is a receptor predominantly expressed on the surface of endothelial cells, where it plays a pivotal role in angiogenesis through its interaction with the extracellular matrix. In our previous studies, we identified the monoclonal antibody 4E1 as a potent inhibitor of angiogenesis by targeting the CD93-Multimerin-2 axis. Here, we report the development of 4E1 as a recombinant whole immunoglobulin and a single-chain variable fragment, designated sc-4E. Both formats retained the binding properties of the parental monoclonal antibody and exhibited comparable inhibitory effects on endothelial cell migration and differentiation. To elucidate the molecular basis of the 4E1-CD93 interaction, we initially employed machine learning-based modeling and docking analyses of the variable heavy and light domains of 4E1. Subsequent crystallographic analysis of sc-4E provided high-resolution structural insights, confirming and validating the predicted model. Further docking experiments and molecular dynamics simulations using the crystallographic structures of CD93 and sc-4E revealed that the interaction is primarily mediated by the CDR-H3 and CDR-L2 loops. Notably, these regions engage with the sushi-like domain of CD93, which is critical for its interaction with Multimerin-2. This comprehensive structural and functional characterization of 4E1 and sc-4E underscores their potential as anti-angiogenic agents. By effectively inhibiting endothelial cell migration and differentiation, 4E1 derivatives represent promising therapeutic candidates for the treatment of ocular vascular diseases driven by pathological angiogenesis.