Influence Of Genetic Polymorphisms Of Uptake (OATP1B1) And Efflux (MRP2, BCRP) Transporters On The Pharmacokinetics Of Clinically Important Cardiovascular Drugs

BackgroundRecent clinical studies indicate that the large inter-individual variability in drug responses (pharmacokinetics and pharmacodynamics) occurs as a result of molecular alterations to various proteins such as drug metabolizing enzymes, drug targets and receptors, and drug transporters. Most of the studies on molecular alterations performed to date have focused on the impact of genetic variation on the expression and function of these proteins. Although genetic polymorphisms of hepatic metabolizing enzymes involved in phase I and phase II reactions have been intensively investigated, little is known about the role of genetic variations in the transporters that act in the liver and kidney.Drug transporters may be classified as influx (eg, OATP and OAT1) and efflux (eg, MDR1, MRP, and BCRP) transporters. The OATP1B1/BCRP/MRP2 combination represents two families of transporters that play important roles in the hepatic transport of organic anions at the sinusoidal and canalicular membranes. In human liver, the uptake of anionic drugs via the OATP 1B1, followed by excretion into the bile via MRP2/BCRP, constitutes vectorial transport for the hepatobiliary excretion of drugs. One important factor that can alter the transporter function of transporters is the genetic polymorphism, and the functional changes in some transporters sometimes affect the pharmacological and toxicological effects as well as pharmacokinetics. So it is important to investigate the clinical impact of genetic polymorphisms of OATP1B1/BCRP/MRP2 on the pharmacokinetics and subsequent pharmacodynamics and toxicological effects of substrate drug.Up to now, most of the evidences related to the combination effect of OATP1B1/BCRP/MRP2 polymorphisms on cardiovascular drugs are still in in vitro level. There is little information about the transporter combination contributions of OATP1B1/BCRP/MRP2 to drug disposition and response in humans. ObjectivesThe aim of the present study was to evaluate the combination effect of OATP1B1/BCRP/MRP2 polymorphisms on the pharmacokinetics of clinically important cardiovascular substrates, such as enalapril, valsartan, pitavastatin, and rosuvastatin in Chinese subjects, and provide molecular mechanism to the individual differences in drug disposition and response caused by membrane transporters.MethodsAfter genotyping screening, one hundred and four healthy Chinese subjects were enrolled in the following study groups:enalapril group (n=32), valsartan group (n=24), pitavastatin group (n=24), and rosuvastatin group (n=24). A high-performance liquid chromatography-tandem mass spectrometry method (LC-MS/MS) was used to determine plasma concentrations of enalapril, valsartan, pitavastatin, and rosuvastatin. The following single nucleotide polymorphisms (SNPs) were determined by polymerase chain reaction (PCR) with direct gene sequencing:organic anion transporting polypeptide 1B1 (OATP1B1) 521T>C and 388A>G, breast cancer resistance protein (BCRP) 421CA and 34G>A, and multidrug resistance-associated protein 2 (MRP2)-24CT.Results1. These variants, including OATP1B1 521T>C and 388A>G, BCRP 421C>A and 34G>A, and MRP2-24C>T and 3972C>T, are relatively common in Chinese population; their frequencies are similar to that in Asians, but significantly different from that in Caucasians and Blacks.2. Plasma concentrations of enalapril in OATP1B1 521TT subjects were lower than that in 521TC-CC subjects, with significant difference in AUCSS between 521TT and 521TC-CC subjects (P=0.048). In contrast to enalapril, the mean AUCo-24hand Cmax of enalaprilat in 521TT subjects were significantly higher than those in 521TC-CC subjects (P=0.040 and P=0.027, respectively) in the single-dose phase, and a similar trend was observed in the multiple-dose phase. Although enalapril pharmacokinetic parameters were not altered by MRP2 genotype, the AUCSS and Cav of enalaprilat were higher in the-24CC group than that in the-24CT-TT group (P=0.038).3. The OATP1B1 388A>G variant was associated with differences in the disposition kinetics of valsartan. The AUC0-48and Cmax of valsartan were 51%(P=0.039) and 39%(P=0.072) higher in the 388AA-AG group than those in the 388GG group. The t1/2 and tmax values showed no difference between these groups.4. For pitavastatin, subjects with the combined genotype of OATP1B1 521TC-CC/BCRP 421CC had a significant higher AUC (P=0.016) and Cmax (P =0.007) than those with the 521TT/421CC or 521TT/421CA-AA genotype, whereas there was no difference in the AUC and Cmax between the 521TT/421CC and 521TT/421CA-AA group. No significant differences were found between the genotype groups in terms of AUC and Cmax values of pitavastatin lactone.5. After single oral dose of rosuvastatin, the AUCo-t, Cmax and percent of cumulative amount eliminated into the urine (Percent_excretion) were significantly higher in BCRP 421CA+AA group than those in the 421CC wild-type group (P=0.030,0.015 and 0.041, respectively), whereas there was no difference in the t1/2 and Tmax between these groups. In contrast, no significant differences were found between the two genotype groups in terms of AUCSS, Cmax, total clearance and renal clearance values at steady state (P>0.05), but a prolonged t1/2was observed in 421CC wild-type group compared with that in 421CA+AA group (p=0.035). In addition, the OATP 1B1 521T>C and MRP2-24C>T variants were not associated with differences in the pharmacokinetic parameters of rosuvastatin.Conclusions1. The pharmacokinetic properties of enalapril and its active metabolite enalaprilat are affected by OATP 1B1 and MRP2 polymorphisms. Plasma exposure to enalaprilat was higher in subjects with a wild-type combination of OATP 1B1 521TT/MRP2-24TT than other polymorphic genotypes.2. The OATP 1B1388A>G polymorphism may play an important role in the pharmacokinetics of valsartan in healthy Chinese males after the exclusion of impoact of OATP 1B1 521T>C genetic polymorphism; whereas MRP2-24C>T variant has no effect on the pharmacokinetics of valsatan.3. The OATP 1B1 polymorphism appears to be an important determinant of the pharmacokinetics of pitavastatin, but not for pitavastatin lactone. However, BCRP 421 C>A variant is not associated with altered pharmacokinetics of pitavastatin and its lactone.4. The BCRP 421C>A variant, rather than MRP2-24C>T and OATP 1B1521T>C, is one of the determinant factors governing the interindividual variability in the pharmacokinetics of rosuvastatin.5. Large differences exist in the effect of transporter polymorphisms on different substrates in vivo in humans and single transporter polymorphism can partly explain why individual patients respond differently to various substrates.