The Therapeutic Antibody LM609 Selectively Inhibits Ligand Binding to Human αVβ3 Integrin via Steric Hindrance
- Structure. 2017 Nov 7;25(11):1732-1739.e5. doi: 10.1016/j.str.2017.09.007.
- 1. Department of Biochemistry, University of Washington, Seattle, WA 98195, USA.
- 2. Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195, USA.
- 3. Department of Hematology and Oncology, University of California at San Diego, La Jolla, CA 92093-0726, USA.
- 4. Unité de Virologie Structurale, Institut Pasteur, Paris, France; CNRS UMR 3569 Virologie, Paris, France.
- 5. Unité de Virologie Structurale, Institut Pasteur, Paris, France; CNRS UMR 3569 Virologie, Paris, France. Electronic address: [email protected].
- 6. Department of Biochemistry, University of Washington, Seattle, WA 98195, USA. Electronic address: [email protected].
The LM609 antibody specifically recognizes αVβ3 Integrin and inhibits angiogenesis, bone resorption, and viral infections in an arginine-glycine-aspartate-independent manner. LM609 entered phase II clinical trials for the treatment of several cancers and was also used for αVβ3-targeted radioimmunotherapy. To elucidate the mechanisms of recognition and inhibition of αVβ3 Integrin, we solved the structure of the LM609 antigen-binding fragment by X-ray crystallography and determined its binding affinity for αVβ3. Using single-particle electron microscopy, we show that LM609 binds at the interface between the β-propeller domain of the αV chain and the βI domain of the β3 chain, near the RGD-binding site, of all observed Integrin conformational states. Integrating these data with fluorescence size-exclusion chromatography, we demonstrate that LM609 sterically hinders access of large ligands to the RGD-binding pocket, without obstructing it. This work provides a structural framework to expedite future efforts utilizing LM609 as a diagnostic or therapeutic tool.