Structural and functional characterization of integrin a5-targeting antibodies for anti-angiogenic therapy
Integrins are heterodimeric receptors important for cell adhesion and signaling. Integrin 5{beta}1 is a key mediator of angiogenesis and its dysregulation is associated with tumor progression and metastasis. Despite numerous efforts, 5{beta}1-targeting therapeutics have been unsuccessful due to poor efficacy and off-target effects. A contributing factor is our limited understanding of how integrin conformation influences interactions with therapeutics. Using cell-based functional assays, patient-derived xenografts, biophysics, and electron microscopy, we shed light on these relationships by characterizing two anti-5{beta}1 antibodies, BIIG2 and MINT1526A. We show that both antibodies bind 5{beta}1 with nanomolar affinity, reduce tube formation in vitro, and bind overlapping epitopes that block fibronectin binding. However, using electron microscopy, we reveal that while BIIG2 binding does not substantially alter the conformational states, MINT1526A preferentially recognizes the bent conformation and restricts the conformational ensemble. These insights can guide which aspects to prioritize to improve the design of future integrin-targeted therapeutics.