Integrin αvβ3 Antagonists for Anti-Angiogenic Cancer Treatment

Direct contact between cellular and extracellular matrix (ECM) proteins is necessary for a diverse array of physiologic processes including cellular activation, migration, proliferation, and differentiation. These direct interactions are modulated by cell adhesion molecules (CAMs) such as integrins, selectins, cadherins, and immunoglobulins. Integrin signaling also plays a key role in tumor growth, angiogenesis, and metastasis. Recent advances in the discovery and characterization of CAMs and their receptors, most notably integrin αvβ3, and the clarification of their roles in disease states have laid the groundwork for the development and clinical implementation of novel anti-cancer treatments. Integrin αvβ3 is a glycoprotein membrane receptor which recognizes ECM proteins expressing an arginine-glycine-aspartic acid (RGD) peptide sequence. The receptor is highly expressed on activated tumor endothelial cells, but not resting endothelial cells and normal organ systems, thus making αvβ3 an appropriate target for anti-angiogenic therapeutics. In addition, αvβ3 is also expressed on tumor cells, allowing for both tumor cell and tumor vasculature targeting of anti-integrin therapy. Throughout the past decade, numerous patents have been published and issued using αvβ3 antagonists for the prevention and/or treatment of cancer, with many antagonists demonstrating positive pre-clinical anti-angiogenic and anti-tumor results. This review will focus on the key points and distinguishing factors for patents which use antibodies, RGD peptides, non-RGD peptides, peptidomimetics, and amine salts as αvβ3 antagonists.