A G protein–biased S1P1 agonist, SAR247799, protects endothelial cells without affecting lymphocyte numbers

Abstract

Endothelial dysfunction is a hallmark of tissue injury and is believed to initiate the development of vascular diseases. Sphingosine-1 phosphate receptor-1 (S1P ₁) plays fundamental physiological roles in endothelial function and lymphocyte homing. Currently available clinical molecules that target this receptor are desensitizing and are essentially S1P ₁ functional antagonists that cause lymphopenia. They are clinically beneficial in autoimmune diseases such as multiple sclerosis. In patients, several side effects of S1P ₁ desensitization have been attributed to endothelial damage, suggesting that drugs with the opposite effect, namely, the ability to activate S1P _1, could help to restore endothelial homeostasis. We found and characterized a biased agonist of S1P ₁, SAR247799, which preferentially activated downstream G protein signaling to a greater extent than β-arrestin and internalization signaling pathways. SAR247799 activated S1P ₁ on endothelium without causing receptor desensitization and potently activated protection pathways in human endothelial cells. In a pig model of coronary endothelial damage, SAR247799 improved the microvascular hyperemic response without reducing lymphocyte numbers. Similarly, in a rat model of renal ischemia/reperfusion injury, SAR247799 preserved renal structure and function at doses that did not induce S1P ₁-desensitizing effects, such as lymphopenia and lung vascular leakage. In contrast, a clinically used S1P ₁ functional antagonist, siponimod, conferred minimal renal protection and desensitized S1P ₁. These findings demonstrate that sustained S1P ₁ activation can occur pharmacologically without compromising the immune response, providing a new approach to treat diseases associated with endothelial dysfunction and vascular hyperpermeability.