The Current Landscape in the Development of Small-molecule Modulators Targeting Sphingosine-1-phosphate Receptors to Treat Neurodegenerative Diseases

Sphingosine 1-phosphate (S1P) is extensively researched as a lysophospholipid and is crucial in various physiological and pathological processes. It achieves this via signalling through five different subtypes of G protein-coupled receptors (GPCRs), namely S1PR1 to S1PR5. S1PR modulators possess the ability to traverse the blood-brain barrier, potentially leading to direct actions within the Central Nervous System (CNS). S1PR modulators specifically bind to receptors located on the surface of naive and central memory lymphocytes, causing these cells to be trapped or confined within the lymph node. The investigation of the S1P pathway has resulted in the approval of three S1PR modulators, namely fingolimod, siponimod, and ozanimod, as medications for the treatment of patients suffering from Multiple Sclerosis (MS). Additionally, new S1PR modulators, such as ponesimod and etrasimod, are currently being developed and tested in clinical trials. Research on the creation of S1P modulators in neurodegenerative illnesses is ongoing as scientists continue to explore novel possibilities for selective S1P modulators. This study provides a concise overview of sphingolipid metabolism, the mechanism by which S1P receptors are affected, and the structural characteristics of several small molecule S1P modulators, with a particular focus on their structure-activity connections.