Impact of CYP3A5 Gene Polymorphism on Efficacy of Simvastatin

BACKGROUND One of the promises of human genetics is individualized therapy. Therefore, we evaluated the impact of CYP3A5 gene polymorphism on the effectiveness of simvastatin (a HMG-CoA reductase inhibitor). METHODS Patients (n = 191) with hypercholesterolemia were treated with simvastatin for at least 6 months and were genotyped for the CYP3A5 polymorphism. RESULTS The frequency of CYP3A5 polymorphism was 0.5% for WT (wild-type), 15.6% for HT (heterozygous, expressors) and 83.9% for HM (homozygous, non-expressors). Differences in lipid profile before and after dose-response of simvastatin treatment were described as % difference {[(variable after-variable before)/variable before]*100}. There was a trend towards the decrease of low density lipoprotein cholesterol (LDL-C) in HT individuals who had a -35.2% reduction with a dose of 20 mg simvastatin and HM individuals who had a slightly higher decrease (-37.5%) despite the lower dose of simvastatin (10 mg, p = 0.07). Furthermore, HT genotype individuals had significantly higher than expected (6-8%) LDL-C % difference between 20 and 40 mg of simvastatin (-35.2 vs -49.2%, p = 0.037). In individuals with HM genotype a significant LDL-C % difference was found between 10 and 40 mg of simvastatin (-37.5 vs -48.4%, p = 0.023). CONCLUSION The individuals with HM polymorphism display a trend towards higher LDL-C reductions compared with HT polymorphism. Within the same genotype, differences between doses were also observed. These findings need to be confirmed in larger studies.