Etrasimod is an organic heterotricyclic compound that is 1,2,3,4-tetrahydrocyclopenta[b]indole substituted by carboxymethyl and [4-cyclopentyl-3-(trifluoromethyl)phenyl]methoxy groups at positions 3R and 7, respectively. It is a potent and functional antagonist of the sphingosine-1-phosphate-1 (S1P1) receptor (IC50 = 1.88 nM in CHO cells). It has a role as an antibacterial agent, a sphingosine-1-phosphate receptor 1 antagonist, an immunosuppressive agent and an anti-inflammatory drug. It is a member of (trifluoromethyl)benzenes, a member of cyclopentanes, an aromatic ether, a monocarboxylic acid and an organic heterotricyclic compound. It is a conjugate acid of an etrasimod(1-).