Description_x000D_ Biochem/physiol Actions_x000D_ NBIR189 is a high-affinity, potent and selective EBI2 (GPR183) antagonist (IC50 = 16 nM against 10 nM 7α,25-OHC for binding human EBI2) that inhibits 7α,25-OHC-induced GTPγS binding (IC50 = 8.5 and 7.0 nM, respectively, against 0.33 and 0.1 nM OHC; human EBI2-expressing CHO membrane), calcium mobilization (IC50 = 11 and 15 nM using human or mouse EBI2-transfected cells, respectively), and chemotaxis (IC50 = 0.3 nM against 20 nM OHC-induced U937 migration). NBIR189 displays no inhibitory potency against 5HT2A, muscarinic acetylcholine receptor M2, adrenoreceptor α1A, nor significant affintiy toward 18 other GPCRs/transporters/enzymes, and exhibits good pharmacokinetic properties and oral availability in mice (AUC = 3608 nmol h/L, Cmax = 835 nM, tmax = 1 h, F = 49%; 3 mg/kg p.o.). A useful tool for probing EBI2-mediated physiological functions and autoimmune disorders.