S1PR1 (sphingosine-1-phosphate receptor 1) is a G-protein-coupled receptor that binds the bioactive lipid sphingosine-1-phosphate (S1P) and activates downstream signaling through Gi proteins, RAC1, SRC, and MAP kinases 1. The receptor plays critical roles in lymphocyte trafficking by maintaining an S1P gradient that guides immune cell egress from lymphoid tissues into circulation 23, and is essential for normal T-cell development and peripheral distribution. S1PR1 also regulates vascular biology, promoting endothelial integrity and controlling angiogenesis through the KLF2-S1PR1 pathway 4, while supporting cardiac morphogenesis and heart development 1. In lung adenocarcinoma, S1PR1 suppresses tumor progression by inhibiting COL5A1, MMP1, and SERPINE1 expression through a p-STAT1/miR-30c-5p/FOXA1 signaling axis, with reduced S1PR1 levels correlating with poor prognosis 5. S1PR1 emerges as a biomarker in endometriosis pathogenesis 6, and represents a therapeutic target in immune-mediated diseases; S1PR1-biased agonists maintain endothelial barrier function without excessive immunosuppression, offering advantages over pan-S1P modulators for treating inflammatory bowel disease and other endothelial dysfunction-associated conditions 73.