Iwuchukwu OF, Feng Q, Wei WQ, Jiang L, Jiang M, Xu H, Denny JC, Wilke RA, Krauss RM, Roden DM, Stein CM. Genetic variation in the UGT1A locus is associated with simvastatin efficacy in a clinical practice setting. Pharmacogenomics. 2014 Nov;15(15). 1739-1747. PMID: 25493567 [PubMed] PMCID: PMC4292894 NIHMSID: NIHMS652640.
Aim: Simvastatin is a lactone prodrug that exists in equilibrium with its active hydroxyacid through a process mediated by UGT1A enzymes. The UGT1A locus has been associated with simvastatin response and disposition in humans. Therefore, we fine-mapped the UGT1A locus to identify genetic variations contributing to simvastatin disposition and response variability. Methods: Using de-identified electronic medical records linked to a DNA biobank, we extracted information about dose and low-density lipo-protein cholesterol (LDL-C) concentrations for patients who received more than two different doses of simvastatin. Pharmacodynamic measures of simvastatin potency and efficacy were calculated from dose-response curves (E0 = baseline LDL-C, ED50 = dose yielding 50% maximum response, and Emax = maximum decrease in LDL-C) in 1100 patients. We selected 153 polymorphisms in UGT1A1 and UGT1A3 for genotyping and conducted genotype-phenotype associations using a prespecified additive model. Results: Two variants in UGT1A1 (rs2003569 and rs12052787) were associated with Emax (p = 0.0059 and 0.031, respectively; for rs2003569 the mean Emax was 59.3 ± 23.0, 62.0 ± 22.4, and 69.7 ± 24.8 mg/dl, for patients with 0, 1 or 2 copies of the minor A allele, respectively). When stratified by race, the difference in response was greater in African-Americans than in European Americans. Rs2003569 was also negatively associated with total serum bilirubin levels (p = 7.85 × 10(-5)). Four rare SNPs were nominally associated with E0 and ED50. Conclusion: We identified a UGT1A1 promoter variant (rs2003569) associated with simvastatin efficacy. Original submitted 26 March 2014; Revision submitted 26 August 2014.