Disposition and Metabolism of Setipiprant, a Selective Oral CRTH2 Antagonist, in Humans

BACKGROUND Setipiprant, a tetrahydropyridoindole derivative, is a CRTH2 (chemoattractant receptor-homologous molecule expressed on T-helper [Th]-2 cells) antagonist that has the potential to be effective in the treatment of patients with diseases with an allergic etiology, such as allergic rhinitis and asthma. OBJECTIVES This study investigated the disposition, metabolism, and elimination of setipiprant. STUDY DESIGN In this open-label study, a single oral dose of 1,000 mg (14)C-labeled setipiprant was administered. PARTICIPANTS Six healthy male subjects were enrolled in this study. RESULTS The radioactive dose was almost completely recovered in feces (88.2 %) and to a smaller extent in urine (11.7 %). The main recovery route for unchanged setipiprant was feces (50 % of the radioactive dose). The recovered amount of unchanged setipiprant in urine accounted for 3.7 %. The two main metabolites were M7 and M9 with the intact tetrahydropyridoindole core of setipiprant. M7 and M9 are supposedly two distinct dihydroxy-dihydronaphthalene isomers assumed to be formed by intermediate epoxidation of the naphthyl ring followed by a hydrolytic epoxide ring-opening. M7 and M9 accounted for 20.0 and 15.3 % of the administered radioactive dose. Both metabolites were mainly excreted via feces and to a lesser extent via urine. M7 was the only metabolite quantifiable in plasma, but at concentrations consistently below 10 % of those of the parent drug. CONCLUSION Setipiprant is mainly excreted in feces in the form of the parent drug and in smaller amounts as its metabolites M7 and M9.