UGT1A128 polymorphism influences glucuronidation of bazedoxifene

Bazedoxifene is used for the prevention and treatment of osteoporosis. After peroral application, bazedoxifene is metabolized by UDP-glucuronosyltransferases (UGTs) to bazedoxifene-4'-glucuronide (M4) and bazedoxifene-5-glucuronide (M5). It has already been shown that a relatively common UGT1A1*28 polymorphism can considerably affect raloxifene pharmacokinetics and pharmacodynamics. As pharmacokinetics of bazedoxifene and raloxifene are very similar, the influence of UGT1A1*28 polymorphism on metabolism of bazedoxifene was investigated by genotyped microsomes. Our results indicate an influence of UGT1A1*28 allele on the formation clearance of both bazedoxifene metabolites. The decreased metabolic clearance was most pronounced in microsomes from polymorphic homozygote (*28/*28) where a 7 to 10-fold lower metabolic clearance was observed for both metabolites compared to other genotypes. In conclusion, the significant UGT1A1*28 genotype effect on bazedoxifene intrinsic metabolic clearance indicates that this subject is worth further exploration in vivo and provides valuable information research in this field.