Abstract
Background: In adults, genetic variation of the drug transporter, organic anion transporting polypeptide (OATP1B1) encoded by the gene SLCO1B1, decreases hepatic uptake of statins. This leads to increased circulating statin concentrations in plasma, thereby placing patients at higher risk for adverse events and decreased efficacy. Expression of OATP transporters in mice changes during development, raising the question of whether in humans the genotype-phenotype relationship observed in adults is relevant in the developing child. Methods: Participants (8-21 years) with at least one allelic variant of SLCO1B1 c.521 T>C (521TC; n=8) and wild type controls (521TT; n=5) were enrolled in a single oral dose pharmacokinetics (PK) study. Pravastatin and isomers were quantified by liquid chromatography tandem mass spectrometry. A model-independent PK approach was used to define the peak plasma concentration (Cmax), area under the curve (AUC) during the sample period and AUC to infinity. Results: 521TC subjects had a nearly 3-fold increase in Cmax (177.62 vs. 56.53 ng/ml; p=0.001) and AUC (389.81 vs. 139.57 ng/ml*h; p=0.004) compared to 521TT controls (Fig. 1). Formation of the 3-alpha-iso-pravastatin acid and lactone isomers in the acidic environment of the stomach prior to absorption was variable in both groups. There was a linear relationship between pravastatin acid AUC and the ratio of pravastatin acid to total analyte (pravastatin acid, 3-alpha-iso-pravastatin, and corresponding lactones) AUC amongst genetic variants (R=0.8961) that does not appear to be present in the control. Conclusion: The impact of the SLCO1B1 c.521 gene variant on pravastatin PK in adults was replicated in our pediatric cohort. However, other physicochemical factors appear to contribute to variability in the dose-exposure relationship. This data must be replicated in a larger cohort, and the pharmacodynamic consequences assessed, before implementing OATP1B1 driven dosing guidelines.
Published Version
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