Influence of FMO3 and CYP3A4 Polymorphisms on the Pharmacokinetics of Teneligliptin in Humans

To evaluate whether alterations in the multidrug-resistance (MDR)-1 gene correlate with intestinal MDR-1 expression and uptake of orally administered P-glycoprotein (PGP) substrates, we analyzed the MDR-1 sequence in 21 volunteers whose PGP expression and function in the duodenum had been determined by Western blots and quantitative immunohistology (n = 21) or by plasma concentrations after orally administered digoxin (n = 8 + 14). We observed a significant correlation of a polymorphism in exon 26 (C3435T) of MDR-1 with expression levels and function of MDR-1. Individuals homozygous for this polymorphism had significantly lower duodenal MDR-1 expression and the highest digoxin plasma levels. Homozygosity for this variant was observed in 24% of our sample population (n = 188). This polymorphism is expected to affect the absorption and tissue concentrations of numerous other substrates of MDR-1.

P-glycoprotein, the gene product of MDR1, confers multidrug resistance against antineoplastic agents but also plays an important role in the bioavailability of common drugs in medical treatment. Various polymorphisms in the MDR1 gene were recently identified. A silent mutation in exon 26 (C3435T) was correlated with intestinal P-glycoprotein expression and oral bioavailability of digoxin. We wanted to establish easy-to-use and cost-effective genotyping assays for the major known MDR1 single nucleotide polymorphisms and study the allelic frequency distribution of the single nucleotide polymorphisms in a large sample of volunteers. In this study, the distribution of the major MDR1 alleles was determined in 461 white volunteers with the use of polymerase chain reaction and restriction fragment length polymorphism. Five amino acid exchanges were found with allelic frequencies of 11.2% for Asn21Asp and 5.5% for Ser400Asn. Strikingly, in exon 21 three variants were discovered at the same locus: 2677G (56.4%), 2677T (41.6%), and 2677A (1.9%), coding for 893Ala, Ser, or Thr. A novel missense Gln1107Pro mutation was found in two cases (0.2%). The highest frequencies were observed for intronic and silent polymorphisms; C3435T occurred in 53.9% of the subjects heterozygously, and 28.6% of individuals were homozygous carriers of 3435T/T with functionally restrained P-glycoprotein. This study provides the first analysis of MDR1 variant genotype distribution in a large sample of white subjects. It gives a basis for large-scale clinical investigations on the functional role of MDR1 allelic variants for bioavailability of a substantial number of drugs.

Our aim was to observe the impact of CYP3A4*1G genetic polymorphism on lipid-lowering efficacy of statins. We studied 217 unrelated hyperlipidemic patients who prospectively received atorvastatin and 199 patients who received simvastatin as a single-agent therapy (20 mg day(-1) p.o.) for 4 weeks. Genotyping of CYP3A4*1G was conducted by a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis. Serum triglyceride (TG), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C) levels were determined before and after treatment by enzymatic assays. The frequency of CYP3A4*1G in Chinese hyperlipidemic patients was 0.276. After atorvastatin treatment, the mean percentage reduction in serum TC was 16.8 +/- 3.3% (*1/*1), 17.8 +/- 3.8% (*1/*1G), and 20.9 +/- 5.0% (*1G/*1G), respectively. The CYP3A4*1G polymorphism had a gene-dose-dependent effect on percentage reduction in serum TC (P < 0.01). Conversely, there was no significant association between lipid-lowering efficacy of simvastatin and CYP3A4*1G polymorphism. Carrying CYP3A4*1G increase the lipid-lowering efficacy of atorvastatin and may have no significant effect on simvastatin treatment.