APPLICATION OF HYPHENATED LC NMR AND LC/MS TECHNIQUES IN RAPID IDENTIFICATION OF IN-VITRO AND IN-VIVO METABOLITES OF ILOPERIDONE/

Iloperidone, ]-1-piperidinyl]propoxy]-3-methoxyphenyl]ethanone, is cur rently undergoing clinical trials as a potential antipsychotic agent. Iloperidone was found to be extensively metabolized to a number of met abolites by rats, dogs, and humans, LC/MS/MS was used to characterize and identify metabolites of iloperidone present in complex biological mixtures obtained from all three species. Identification of some of th e unknown metabolites in rat bile was achieved successfully by combina tion of LC/NMR and LC/MS with a minimum amount of sample cleanup. The utility of coupling a semipreparative HPLC to LC/MS instrument for fur ther characterization of collected metabolites was demonstrated. It wa s shown that iloperidone was metabolized by O-dealkylation processes t o yield [3-hydroxypropyl)-4-piperidinyl]-1,2-benzisoxazole and )-1-pip eridinyl]propoxy]-2-hydroxyphenyl]ethanone. Oxidative N-dealkylation l ed to the formation of 6-fluoro-3-(4-piperidinyl)-1,2-benzisoxazole an d a secondary metabolite, 3-[(4-acetyl-2-methoxy)phenoxy]propionic aci d. Iloperidone was reduced to produce nyl]propoxy]-3-methoxy-alpha-met hylbenzenemethanol as the major metabolite in humans and rats. Hydroxy lation of iloperidone produced 1-[4-[3-[4-(6-fluoro-1 idinyl]propoxy]- 2-hydroxy-5-methoxyphenyl]ethanone and 1-[4-[3-[4-(6-fluoro-1,2-benzis oxazol-3-yl)-1 dinyl]-3-methoxyphenyl]propoxy]-2-hydroxyethanone, the later of which was found to be the principal metabolite in dogs. The i dentities of all these metabolites were established by comparing the L C/MS retention times and mass spectral data with synthetic standards.