In vitro metabolism of perospirone was examined with rat, monkey and human liver S9, human liver microsomes and yeast microsomes expressing human P450, using14C labeled perospirone. With rat liver S9, the major metabolites were MX9 and ID-11614, produced by cleavage at the butylene chain. However, some butylene non-cleavage and hydration of the cyclohexane ring were found, although limited in extent. Unknown metabolites accounted for about 10% of the total. After incubation for 10 minutes with monkey liver S9, the major metabolites were ID-15036 and MX11, hydrated in the cyclohexane ring. After incubation for 60 minutes, ID-15001, i.e. the butylene chain cleavage type increased. Unknown metabolites accounted for about 20%. After incubation for 10 minutes with human liver S9, the major metabolite was ID-15036, hydrated in the cyclohexane ring. In addition, MX11 and many unknown metabolites were evident. After incubation for 60 minutes, the butylene chain cleavage type and unknown metabolites increased. Individual differences were found in the metabolic reaction rate. With human liver microsomes, MX11, ID-15001 and unknown metabolites were again the major metabolites. With yeast microsomes expressing human P450 subtypes, CYP1A1, 2C8, 2D6, 3A4 were responsible for the metabolism in particular, and CYP3A4 contributes greatly. Therefore it is unlikely that genetic polymorphism will arise a present a problem with regard to the clinical drug.
The results demonstrated that the main metabolic pathway in human liver S9 and liver microsomes involve oxidation at cyclohexane, oxidative cleavage of the butylene side chain and S-oxidation. The same was the case in rat and monkey S9, but species differences were found in the proportions of the metabolites produced.