Structural determinants of sphingosine-1-phosphate receptor selectivity

Fingolimod, the prodrug of fingolimod-1-phosphate (F1P), was the first sphingosine-1-phosphate receptor (S1PR) modulator approved for multiple sclerosis. F1P unselectively targets all five S1PR subtypes. While agonism (functional antagonism via receptor internalization) at S1PR1 leads to the desired immune modulatory effects, agonism at S1PR3 is associated with cardiac adverse effects. This motivated the development of S1PR3-sparing compounds and led to a second generation of S1PR1,5-selective ligands like siponimod and ozanimod. Our method combines molecular dynamics simulations and three-dimensional pharmacophores (dynophores) and enables the elucidation of S1PR subtype-specific binding site characteristics, visualizing also subtle differences in receptor-ligand interactions. F1P and the endogenous ligand sphingosine-1-phosphate bind to the orthosteric pocket of all S1PRs, but show different binding mode dynamics, uncovering potential starting points for the development of subtype-specific ligands. Our study contributes to the mechanistic understanding of the selectivity profile of approved drugs like ozanimod and siponimod and pharmaceutical tool compounds like CYM5541. Fingolimod, the prodrug of fingolimod-1-phosphate, is approved for treating multiple sclerosis due to its immune-modulatory effects mediated by sphingosine-1-phosphate receptors (S1PR). S1PR3-associated side effects motivated the development of S1PR1,5-selective drugs. Combining molecular dynamics simulations and dynamic pharmacophores, structural reasons for selectivity are analyzed to contribute to understanding the S1PR subtype selectivity.image