Sphingolipids at large form a class of lipids characterized by a particular aliphatic aminoalcohol, which is sphingosine.

Originally thought as an intracellular second messenger, it was discovered to be an extracellular ligand for G protein-coupled receptor S1PR1 in 1998.

S1P interaction with its receptor S1PR1 is needed for the egress of immune cells from the lymphoid organs (such as thymus and lymph nodes) into the lymphatic vessels.

[12] A research team, led by a scientist at Weill Cornell Medical College, has discovered that red blood cells perform a second vital function: angiogenesis.

Given its role in creating new blood vessels, scientists recognize S1P as vital to human health — and a player in some diseases, such as cancer.

S1P has protected ovarian tissue xenografts in SCID mouse models from radiation induced atresia.

[24] However, its mechanism of inhibiting the sphingomyelin apoptotic pathway may also interfere with the apoptosis action of chemotherapy drugs.

[citation needed] Although S1P is active at very low concentrations, bioavailability of the compound in human skin is a concern.

[citation needed] Sonepcizumab is an experimental anti-S1P monoclonal antibody that has had a phase II clinical trial for renal cell carcinoma.

The drug fingolimod (FTY720), which agonizes the S1P receptor,[29] prevents autoimmune lymphocytes from moving from the lymphoid organs into the central nervous system.

It has been shown in phase III clinical trials to reduce relapses and improve other outcomes in multiple sclerosis.

[30][31] S1P, as well as FTY720, has been shown to have anti-inflammatory properties at low concentrations and prevent monocyte:endothelial interactions in aorta, possibly through the S1P1 receptor.