Shared ligand-blocking mechanism but distinct conformational modulation by α5-targeting antibodies BIIG2 and MINT1526A

Abstract Integrins are heterodimeric receptors important for cell adhesion and signaling. Integrin α5β1 is a key mediator of angiogenesis and its dysregulation is associated with tumor progression and metastasis. Despite numerous efforts, α5β1-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-α5β1 antibodies, BIIG2 and MINT1526A. We show that both antibodies bind α5β1 with nanomolar affinity, reduce angiogenesis in vitro, and bind overlapping epitopes that block fibronectin binding. However, using cryoEM, we reveal that while BIIG2 binding doesn’t alter the conformational states, MINT1526A restricts α5β1’s range of flexibility. These insights can guide which aspects to prioritize and improve the design of future integrin-targeted therapeutics. Competing Interest Statement JBH is a current employee and owns stock in Nykode Therapeutics ASA, a clinical-stage biopharmaceutical company with a focus on cancer immunotherapies. CMA is a current employee at Genentech. All other authors declare no potential conflicts of interest. Footnotes Updated main text for clarity and improved organization; adjusted article title to more accurately reflect the conclusions; revised figure 1 and 2; supplemental files updated