Systematic screening for polymorphisms in the CYP3A4 gene in the Chinese population

Effect of recombinant CYP3A4 variants and interaction on imatinib metabolism in vitro

The aim of this study was to investigate the catalytic activity of 26 Cytochrome P450 3A4 (CYP3A4) variants and drug interactions on imatinib metabolism in recombinant insect microsomes. This study was designed with an appropriate incubation system and carried out in the constant temperature water. By using ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) to measure the quantities of its metabolite N-desmethyl imatinib, to elucidate the impacts of the CYP3A4 genetic polymorphism and drug interactions on the metabolism of imatinib. Consequently, as compared to CYP3A4.1, the intrinsic clearance (CLint) values of the variations were dramatically changed, rising from 2.34 % to 120.57 %. CYP3A4.14 showed an increase in CLint in comparison to CYP3A4.1, and the remaining 24 variants demonstrated decreases in catalytic activity for the metabolism of imatinib. In addition, the metabolism of imatinib was decreased to varied degrees by ketoconazole, itraconazole, and fluconazole in CYP3A4.1 and CYP3A4.18. Moreover, most of CYP3A4 variants showed similar trend of enzyme activity under different substrates of imatinib and cabozantinib, except 6 variants (CYP3A4.3,.4,.10,.15,.29 and.31). The first study of the effects of 26 CYP3A4 variants on imatinib metabolism will contribute to the clinical evaluation of imatinib and help personalize therapy in clinical settings.

Cytochrome P4503A4 gene polymorphisms guide safe sufentanil analgesic doses in pregnant Chinese mothers: a multicenter, randomized, prospective study

BACKGROUND

Sufentanil and ropivacaine when used as epidural anesthetics effectively reduce maternal pain during labor. From previous reports, rs2242480 single nucleotide polymorphisms (SNPs) can alter sufentanil metabolism, which affects analgesic efficacy.

METHODS

We randomly divided 573 eligible mothers into groups A and B (in a 1 : 3 ratio). The control group (group A) was given sufentanil at the usual 0.5 mg/L-1 dose + 0.15% ropivacaine hydrochloride mixture in 10 ml. The sufentanil dose given to the intervention group (group B) was determined by genotype: the GA and AA genotype group (group B1) was given 87.6% (design based on previous study results) of the usual sufentanil clinical dose (0.438 mg/L-1 sufentanil + 0.15% ropivacaine hydrochloride mixture in 10 ml) and the GG genotype group (group B2) was given the same dose as group A. Efficacy indicators consisting of maternal vital signs, obstetric transfer, neonatal prognostic indicators, and adverse effects were recorded before and after analgesia across groups.

RESULTS

Visual analog scale scores after analgesia across groups were significantly different from scores before analgesia, showing that analgesic effects across groups were effective. No significant differences were observed in efficacy, obstetric transfer, and neonatal prognosis indicators between groups. In comparison to groups B1 and B2, group A showed more markedly suppressed cardiovascular and respiratory effects, and also a higher incidence of negative side effects such as vomiting and urinary retention.

CONCLUSION

We confirmed that individualizing sufentanil doses based on maternal genotypes increased safety and success rates for women during childbirth.

The impacts of CYP3A4 genetic polymorphism and drug interactions on the metabolism of lurasidone

The aim of this study was to investigate the impacts of 24 variants of recombinant human CYP3A4 and drug interactions on the metabolism of lurasidone. In vitro, enzymatic reaction incubation system of CYP3A4 was established to determine the kinetic parameters of lurasidone catalyzed by 24 CYP3A4 variants. Then, we constructed rat liver microsomes (RLM) and human liver microsomes (HLM) incubation system to screen potential anti-tumor drugs that could interact with lurasidone and studied its inhibitory mechanism. In vivo, Sprague-Dawley (SD) rats were applied to study the interaction between lurasidone and olmutinib. The concentrations of the analytes were detected by ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). As the results, we found that compared with the wild-type CYP3A4, the relative intrinsic clearances vary from 355.77 % in CYP3A4.15 to 14.11 % in CYP3A4.12. A series of drugs were screened based on the incubation system, and compared to without olmutinib, the amount of ID-14283 (the metabolite of lurasidone) in RLM and HLM were reduced to 7.22 % and 7.59 %, and its IC50 were 18.83 ± 1.06 μM and 16.15 ± 0.81 μM, respectively. At the same time, it exerted inhibitory effects both through a mixed mechanism. When co-administration of lurasidone with olmutinib in rats, the AUC(0-t) and AUC(0-∞) of lurasidone were significantly increased by 73.52 % and 69.68 %, respectively, while CLz/F was observably decreased by 43.83 %. In conclusion, CYP3A4 genetic polymorphism and olmutinib can remarkably affect the metabolism of lurasidone.

The effect of CYP3A4 genetic polymorphism and drug interaction on the metabolism of istradefylline

AIM

This study investigated into the effect of CYP3A4 genetic polymorphism on istradefylline metabolism. Moreover, the potential drug-drug interaction with istradefylline was determined as well as underlied mechanism.

METHOD

In vitro, enzymatic reaction was performed to determine the kinetic parameters of CYP3A4 and its variants on catalyzing istradefylline. Meanwhile, the rat liver microsomes incubation assay was applied to screen interacting drugs. In vivo, SD rats were used to investigate the selected drug interaction. UPLC-MS/MS was used to detect the metabolite M1.

RESULT

The results demonstrated that the relative clearance rate of CYP3A4.29 decrease significantly compared with CYP3A4.1. But there is no statistically diverse in activities among CYP3A4.1, 2 and 3. The relative clearance rates of the remaining variants are significantly decreased compared with CYP3A4.1. In addition, 148 drugs were screened to determine the potential interaction with istradefylline, among which calcium channel blockers were identified. It's indicated that nimodipine has a significant inhibitory effect on metabolizing istradefylline with IC₅₀ of 6.927 ± 0.372 μM, which via competitive and non-competitive mixed mechanism. In vivo, when istradefylline and nimodipine was co-administered to SD rats, we found the main pharmacokinetic parameters of M1 reduced remarkably, including AUC, MRT, C_max and CL_z/F.

CONCLUSION

CYP3A4 genetic polymorphism and nimodipine affect the metabolism of istradefylline. Thus, the present study provided reference data for clinical individualized medicine of istradefylline.

Functional evaluation of vandetanib metabolism by CYP3A4 variants and potential drug interactions in vitro

AIM

To investigate the enzymatic properties of cytochrome P450 3A4 (CYP3A4) variants and their ability to metabolize vandetanib (VNT) in vitro, and to study potential drug interactions in combination with VNT.

METHOD

Recombinant CYP3A4 cell microsomes were prepared using a Bac-to-Bac baculovirus expression system. Enzymatic reactions were carried out, and the metabolites were determined by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS).

RESULTS

The activities of 27 CYP3A4 variants were determined to assess the degree of VNT metabolism that occurred. Analysis indicated that there was enhanced intrinsic clearance (V_max/K_m, CLint) for eight variants (CYP3A4.2, 3, 9, 15, 16, 29, 32, and 33), while there was a significant decrease in CYP3A4.5, 7, 8, 10-14, 17-20, 23, 24, 28, 31, and 34. Compared with CYP3A4.1, no significant differences were found for CYP3A4.6 and 30. Furthermore, the relative clearances were compared between VNT and cabozantinib, which were all metabolized by CYP3A4 with the same indications. When combined with ketoconazole, which is a CYP inhibitor, obvious differences were observed in the potency of VNT between different variants, including CYP3A4.2, 15, and 18.

CONCLUSION

This comprehensive assessment of CYP3A4 variants provides significant insights into the allele-specific metabolism of VNT and drug interactions in vitro. We hope that these comprehensive data will provide references and predictions for the clinical application of VNT.

Interaction of Hepatitis B Virus X Protein with the Pregnane X Receptor Enhances the Synergistic Effects of Aflatoxin B1 and Hepatitis B Virus on Promoting Hepatocarcinogenesis

BACKGROUND AND AIMS

Hepatitis B virus (HBV) infection has been found to increase hepatocellular sensitivity to carcinogenic xenobiotics, by unknown mechanisms, in the generation of hepatocellular carcinoma. The pregnane X receptor (PXR) is a key regulator of the body's defense against xenobiotics, including xenobiotic carcinogens and clinical drugs. In this study, we aimed to investigate the molecular mechanisms of HBV X protein (HBx)-PXR signaling in the synergistic effects of chemical carcinogens in HBV-associated hepatocarcinogenesis.

METHODS

The expression profile of PXR-cytochrome p450 3A4 (CYP3A4) signaling was determined by PCR, western blotting, and tissue microarray. Cell viability and aflatoxin B1 (AFB1) cytotoxicity were measured using the cell counting kit-8 assay. Target gene expression was evaluated using transient transfection and real time-PCR. The genotoxicity of AFB1 was assessed in newborn mice with a single dose of AFB1.

RESULTS

HBx enhanced the hepatotoxicity of AFB1 by activating CYP3A4 and reducing glutathione S-transferase Mu 1 (GSTM1) in cell lines. Activation of PXR by pregnenolone 16α-carbonitrile increased AFB1-induced liver tumor incidence by up-regulating oncogenic KRAS to enhance interleukin (IL)-11:IL-11 receptor subunit alpha-1 (IL11RA-1)-mediated inflammation in an HBx transgenic model.

CONCLUSIONS

Our finding regarding AFB1 toxicity enhancement by an HBx-PXR-CYP3A4/ GSTM1-KRAS-IL11:IL11RA signaling axis provides a rational explanation for the synergistic effects of chemical carcinogens in HBV infection-associated hepatocarcinogenesis.

Development and validation of a rapid liquid chromatography/tandem mass spectrometry method to quantitate gabapentin and buprenorphine in human serum

RATIONALE

Gabapentin has shown initial promise as an opioid-sparing medication in pain patients as well as a treatment for opioid withdrawal and liquid chriomatography/tandem mass spectrometry (LC/MS/MS) is often used for clinical monitoring. Despite reports of validated tandem mass spectrometric methods for the determination of gabapentin and buprenorphine, mechanisms for the collision-induced fragmentation have not been adequetely described.

METHODS

A rapid analytical method has been developed to determine gabapentinoid, gabapentin, and the partial opioid agonist, buprenorphine, in 20 μL of human serum using LC/MS/MS with a chromatographic run time of 2 min. A simplified sample cleanup procedure using methanol precipitation of serum proteins/lipids followed by evaporation and reconstitution in mobile phase was demonstrated. Gabapentin and buprenorphine were detected following positive ion electrospray ionization using multiple-reaction monitoring. The internal standard approach was used for quantitation with labeled gabapentin-D10 and buprenorphine-D4 serving as internal standards. Using organic reaction principals and stable isotope labels, collision-induced fragmentation mechanisms for both gabapentin and buprenorphine are proposed. The method was validated according to the FDA Guidance for Industry - Bioanalytical Method Validation.

RESULTS

Accuracy was demonstrated by error values ≤15% for buprenorphine and ≤6% for gabapentin. The inter-day precision was ≤4.88% and 15.59% for gabapentin and buprenorphine and the intra-day precision was ≤5.20% and 11.65% for gabapentin and buprenorphine. The lower limit of quantitation corresponded to 10 ng/mL for gabapentin and 1 ng/mL for buprenorphine in serum. Recoveries were 104 ± 2.55% and 85 ± 2.03% for gabapentin and buprenorphine, respectively.

CONCLUSIONS

Concentrations of gabapentin and buprenorphine were determined for five authentic human serum samples to further validate the utility of the method and applicable to therapeutic drug monitoring beyond its use as a drug screening assay. Furthermore, new mechanisms for the collision-induced dissociation of gabapentin and buprenorphine have been proposed.

Functional assessment of the effects of CYP3A4 variants on acalabrutinib metabolism in vitro

AIM

We aimed (i) to study the effects of genetic polymorphism of cytochrome P450 3A4 (CYP3A4) and drug interactions on acalabrutinib (ACA) metabolism and (ii) to investigate the mechanisms underlying the effects of CYP3A4 variants on the differential kinetic profiles of ACA and ibrutinib.

METHOD

Recombinant human CYP3A4 and variants were expressed using a Bac-to-Bac baculovirus expression system. The cell microsome was prepared and subjected to kinetic study. The analyte concentrations were determined by UPLC-MS/MS. A molecular docking assay was employed to investigate the mechanisms leading to differences in kinetic profiles.

RESULTS

The kinetic parameters of ACA, catalyzed by CYP3A4 and 28 of its variants, were determined, including V_max, K_m, and K_si. CYP3A4.6-8, 12, 13, 17, 18, 20, and 30 lost their catalytic function. No significant differences were found for CYP3A4.4, 5, 10, 15, 31, and 34 compared with CYP3A4.1 with respect to intrinsic clearance (V_max/K_m, Clint). However, the Clint values of CYP3A4.9, 14, 16, 19, 23, 24, 28, 32 were obviously decreased, ranging from 0.02 to 0.05 μL/min/pmol. On the contrary, the catalytic activities of CYP3A4.2, 3, 11, 29, and 33 were increased dramatically. The Clint value of CYP3A4.11 was 5.95 times as high as that of CYP3A4.1. Subsequently, CYP3A4.1, 3, 11, 23, and 28 were chosen to study the kinetic changes in combination with ketoconazole. Interestingly, we found the inhibitory potency of ketoconazole varied in different variants. In addition, the kinetic parameters of ibrutinib and ACA were accordingly compared in different CYP3A4 variants. Significant differences in relative clearance were observed among variants, which would probably influence the distance between the redox site and the heme iron atom.

CONCLUSION

Genetic polymorphism of CYP3A4 extensively changes its ACA-metabolizing enzymatic activity. In combination with a CYP inhibitor, its inhibitory potency also varied among different variants. Even the same variants exhibited different capabilities catalyzing ACA. Its enzymatic capabilities are probably determined by the distance between the substrate and the heme iron atom, which could be impacted by mutation.

Pharmacogenetics of common SNP affecting drug metabolizing enzymes: comparison of allele frequencies between European and Malaysian/Singaporean

Compared to Europe, data on genetic variation in genes transcribing drug metabolizing enzymes among Asian is limited due to ethnic diversity. Here we compare frequencies for clinically relevant single nucleotide polymorphism (SNP) commonly observed in drug metabolizing enzymes between European and Malaysian/Singaporean. Minor allele frequencies (MAF) for the indicated SNPs for European, South Asian and East Asian populations were obtained from the NCBI website (https://www.ncbi.nlm.nih.gov/snp). The SNP prevalence among Malaysian/Singaporean was characterized from gene association studies. Generally, some SNPs in CYP2D6 and CYP2C19 do not show good agreement between the two populations as to the MAF value obtained. CYP2D6*4 tends to be more common among European, whereas CYP2D6*10 is more common in Malays and Chinese among Singaporean. Regardless of different phenotype, MAF of CYP2D6*4 for Indians is similar to that seen by the European. Singaporeans show smaller MAF for CYP2C19*17 but higher CYP2C19*2 frequencies as opposed to European ones. Following growing attention to the contribution of CYP3A4/5, N-acetyltransferases (NAT2), thiopurine methyltransferase (TPMT) and uridine diphosphate glucuronosyltransferases (UGT)2B7 in predicting drug response across Europe, there are limited pharmacogenetics (PGx) studies examining the gene-drug interaction among Malaysian/Singaporean. To better understand the heterogeneity of the drug response, PGx studies for the abovementioned enzymes between ethnics in Malaysian/Singaporean should be identified.

Pharmacogenetics of common SNP affecting drug metabolizing enzymes: comparison of allele frequencies between European and Malaysian/Singaporean

Compared to Europe, data on genetic variation in genes transcribing drug metabolizing enzymes among Asian is limited due to ethnic diversity. Here we compare frequencies for clinically relevant single nucleotide polymorphism (SNP) commonly observed in drug metabolizing enzymes between European and Malaysian/Singaporean. Minor allele frequencies (MAF) for the indicated SNPs for European, South Asian and East Asian populations were obtained from the NCBI website (https://www.ncbi.nlm.nih.gov/snp). The SNP prevalence among Malaysian/Singaporean was characterized from gene association studies. Generally, some SNPs in CYP2D6 and CYP2C19 do not show good agreement between the two populations as to the MAF value obtained. CYP2D6*4 tends to be more common among European, whereas CYP2D6*10 is more common in Malays and Chinese among Singaporean. Regardless of different phenotype, MAF of CYP2D6*4 for Indians is similar to that seen by the European. Singaporeans show smaller MAF for CYP2C19*17 but higher CYP2C19*2 frequencies as opposed to European ones. Following growing attention to the contribution of CYP3A4/5, N-acetyltransferases (NAT2), thiopurine methyltransferase (TPMT) and uridine diphosphate glucuronosyltransferases (UGT)2B7 in predicting drug response across Europe, there are limited pharmacogenetics (PGx) studies examining the gene-drug interaction among Malaysian/Singaporean. To better understand the heterogeneity of the drug response, PGx studies for the abovementioned enzymes between ethnics in Malaysian/Singaporean should be identified.

Pharmacogenetics of tamoxifen therapy in Asian populations: from genetic polymorphism to clinical outcomes

BACKGROUND

Compared with western countries, Asian breast cancer patients have unique pathological and biological characteristics. Most of them are premenopausal women with HR positive. Tamoxifen as the first-line drug for premenopausal women with HR+ is involved in multiple enzymes and transporters during metabolizing and transporting process. Variants that cause decreased or inactive gene products leading to abnormal responses in tamoxifen therapy have well been studied in western countries, whereas such information is much less reported in Asian populations.

OBJECTIVE

In order to elucidate the relationship between genetic variants and tamoxifen-induced individual drug reactions in different Asian populations and further identify genotypes/phenotypes with potential therapeutic significance.

METHODS

We reviewed the frequencies of genetic variants in major enzymes and transporter genes involved in the metabolism and transport of tamoxifen across Asian populations as well as significant correlations between genotypes/metabolic phenotypes and metabolites concentrations or BC clinical outcomes.

RESULTS

Significant inter-ethnic differences in allele frequencies was found among Asian populations, such as CYP2D6*4, *10, *41, CYP2C9*2, ABCB1 C3435T and SLCO1B1*5, and CYP2D6*10/*10 is the most common genotype correlated with adverse clinical outcomes. Moreover, we summarized the barriers and controversies of implementing pharmacogenetics in tamoxifen therapy and concluded that more population-specific pharmacogenetic studies are needed in the future.

CONCLUSION

This review revealed more systematic pharmacogenomics of genes involved in the metabolism and transport besides CYP2D6, are required to optimize the genotyping strategies and guide the personalized tamoxifen therapy in Asian populations.

Evaluation of Recombinant CYP3A4 Variants on the Metabolism of Oxycodone In Vitro

Cytochrome P450 3A4 is a highly polymorphic enzyme and metabolizes approximately 40%-60% of therapeutic drugs. Its genetic polymorphism may significantly affect the expression and function of CYP3A4 resulting in alterations of the pharmacokinetics and pharmacodynamics of the CYP3A4-mediated drugs. The purpose of this study was to evaluate the catalytic activities of 30 CYP3A4 nonsynonymous variants and wild type toward oxycodone in vitro. CYP3A4 proteins were incubated with oxycodone for 30 min at 37 °C and the reaction was terminated by cooling to -80 °C immediately. Ultraperformance liquid chromatography tandem mass-spectrometry was used to analyze noroxycodone, and kinetic parameters Km, Vmax, and intrinsic clearance (Vmax/Km) of noroxycodone were also determined. Compared with CYP3A4.1, 24 CYP3A4 variants (CYP3A4.2-.5, -.7-.16, -.18 and -.19, -.23 and -.24, -.28 and -.29, and -.31-.34) exhibited significantly decreased relative clearance values (from 4.82% ± 0.31% to 80.98% ± 5.08%), whereas CYP3A4.6, -.17, -.20, -.21, -.26, and -.30 displayed no detectable enzyme activity. As the first study of these alleles for oxycodone metabolism in vitro, results of this study may provide insight into establishing the genotype-phenotype relationship for oxycodone and serve as a reference for clinical administrators and advance the provision of personalized precision medicine.

Buprenorphine-cannabis interaction in patients undergoing opioid maintenance therapy

Buprenorphine is a partial μ-opioid agonist widely used for opioid maintenance therapy (OMT). It is mainly metabolized to pharmacologically active norbuprenorphine by the cytochrome P450 (CYP) isozyme 3A4. This may give rise to drug-drug interactions under combinations with inhibitors or inducers of CYP3A4. Cannabis is a potential inhibitor of CYP3A4, and there is a large degree of concomitant cannabis use among OMT patients. We performed a retrospective analysis on liver healthy OMT patients substituted with buprenorphine, either with (n = 15) or without (n = 17) concomitant use of cannabis. Patients with additional illicit drugs or medications affecting CYP3A were excluded. Measured blood concentrations of buprenorphine and norbuprenorphine were compared between the two groups. Cannabis users and non-users received similar doses, but users had 2.7-fold higher concentrations of buprenorphine (p < 0.01) and 1.4-fold for norbuprenorphine (1.4-fold, p = 0.07). Moreover, the metabolite-to-parent drug ratio was 0.98 in non-users and 0.38 in users (p = 0.02). Female gender did not produce significant effects. These findings indicate that cannabis use decreases the formation of norbuprenorphine and elevates buprenorphine and norbuprenorphine concentrations in blood most probably by inhibition of CYP3A4. The pharmacokinetic interaction may give rise to enhanced or altered opioid activity and risk of intoxications. Physicians should inform patients about this risk and supervise cannabis users by regular control of buprenorphine blood levels, i.e., by therapeutic drug monitoring.

The Genetic Polymorphism of CYP3A4 rs2242480 is Associated with Sirolimus Trough Concentrations Among Adult Renal Transplant Recipients

BACKGROUND

The large interindividual variability in the genetic polymorphisms of sirolimus (SIR)- metabolizing enzymes, transporters, and receptors can lead to qualitatively and quantitatively distinct therapeutic responses.

OBJECTIVE

We examined the impact of numerous candidate single-nucleotide polymorphisms (SNPs) involved in the trough concentration of SIR-based immunosuppressant regimen.

METHODS

This is a retrospective, long-term cohort study involving 69 renal allograft recipients. Total DNA was isolated from recipient blood samples and trough SIR concentrations were measured by microparticle enzyme immunoassay. Genome sequence reading was targeted based on next-generation sequencing. The association of tagger SNPs to SIR trough concentrations with non-genetic covariate adjusting was analyzed using logistic regression.

RESULTS

A total of 300 SNPs were genotyped in the recipient DNA samples using target sequencing analysis. Only the SNP of CYP3A4 (Ch7: 99361466 C>T, rs2242480) had a significantly higher association with SIR trough concentration as compared to the other 36 tagger SNPs. The mean trough SIR concentration of patients in the CYP3A4 rs2242480-CC group was more significant compared to that of the CYP3A4 rs2242480-TC and TT group, respectively 533.3; 157.4 and 142.5 (ng/ml)/mg/kg, P<0.0001. After adjusting the SNPs, there was no significant association between clinical factors such as age, follow-up period, the incidence of delayed graft function, immunosuppression protocol, and sex with SIR trough concentration.

CONCLUSION

These findings indicated a significant association of polymorphism in the CYP3A4 (Ch7: 99361466 C>T, rs2242480) with SIR trough concentration after 1-year administration in patients who have undergone kidney transplantation.

Effects of 26 Recombinant CYP3A4 Variants on Brexpiprazole Metabolism

As a new atypical antipsychotic, brexpiprazole is primarily metabolized by cytochrome P450 3A4 (CYP3A4). However, genetic polymorphisms in CYP3A4 cause wide variability in individuals' responses to brexpiprazole, leading to unpredictable adverse side effects or even therapeutic failure. The present study was designed to systematically study the effects of 26 recombinant CYP3A4 variants on the metabolism of brexpiprazole and investigate their enzymatic activity. Wild-type CYP3A4 and the 26 variants were incubated with the substrate brexpiprazole for 30 min at 37 °C. The metabolite DM-3411 was detected using ultraperformance liquid chromatography-tandem mass spectrometry. The activity of the wild-type CYP3A4 and 26 of its variants was analyzed. Then, the mechanism underlying the changes in enzyme function was observed using molecular dynamics simulations and molecular docking. Compared with CYP3A4.1, the enzymatic activities of CYP3A4.19, -.24, and -.28 were not significantly different (from 91.82% to 96.25%), but CYP3A4.14 and CYP3A4.15 exhibited higher enzyme activity (from 117.9 to 127.5%). The remaining 21 isoforms, including CYP3A4.2, -.3, -.4, -.5, -.7, -.8, -.9, -.10, -.11, -.12, -.13, -.16, -.17, -.18, -.20, -.23, -.29, -.31, -.32, -.33 and -.34, displayed lower enzymatic activities (from 2.90% to 75.72%). The results obtained from computer modeling indicated that weak binding affinity impaired the function of CYP3A4.32. Mutations that occur around the active site might lead to a loss of enzymatic activity, while the variants located far away from the active site perhaps had little effect on function of CYP3A4. These comprehensive data provide a reference and prediction for treatment strategies and risk assessments of brexpiprazole.

Enzymatic Activities of CYP3A4 Allelic Variants on Quinine 3-Hydroxylation In Vitro

Cytochrome P450 3A4 (CYP3A4) enzyme activity is known to show considerable ethnic heterogeneity and inter-individual differences, affecting the outcome of drug treatment. CYP3A4 genetic polymorphisms are believed to be one of the important causes, leading to inter-individual variability in drug metabolism. Quinine is an antipyretic drug with antimalarial properties that is metabolized primarily by CYP3A4. Quinine 3-hydroxylation has been proven as a biomarker reaction for evaluating CYP3A4 ability. Quinine has frequent adverse effects and there are distinct inter-individual differences in quinine sensitivity. The open reading frame for 30 CYP3A4 allelic variants were constructed from wild-type CYP3A4*1A by an overlap extension polymerase chain reaction. Recombinant CYP3A4 variants were expressed using baculovirus-insect cell expression system, and their catalytic activities towards quinine hydroxylation were determined and evaluated. Of the 30 CYP3A4 allelic variants, 23 variants exhibited significantly reduced intrinsic clearance towards quinine, 2 variants showed increased intrinsic clearance for quinine, 2 variants possessed no significant differences towards quinine, compared with CYP3A4*1A, and 3 variants had no detected expression and enzyme activity. Our assessment on the enzymatic activities of CYP3A4 variants towards quinine may contribute to laying an experimental foundation for further clinical studies so as to accelerate the process of determining the associations between genetic variations and clinical phenotypes.

CYP3A4 gene polymorphism is correlated with individual consumption of sufentanil

BACKGROUND

Pain is one of the major adverse clinical outcomes of cesarean section (CS). In the past few years, researchers and physicians have been optimizing post-operative analgesic modalities, but the results are still undesirable for the parturient. The cytochrome P-450 3A4 (CYP3A4) gene has been reported to contribute significantly to human liver microsomal oxidation of sufentanil and alfentanil.

METHODS

We detected the frequency of CYP3A4 mutant allele, which is associated with the metabolism of diverse drugs, including opioids used for anesthesia. We then investigated the correlation between sufentanil (an opioid analgesic) consumption and CYP3A4 genetic polymorphism.

RESULTS

We found the frequency of the CYP3A4∗1G (the mutant form of CYP3A) variant allele to be 0.279 in 71 parturients undergoing cesarean section and 137 age-matched parturients with vaginal delivery. Interestingly, the parturients with homozygous CYP3A4∗1G showed less sufentanil consumption compared with those having the wild-type genotype.

CONCLUSION

In summary, we found a correlation between CYP3A4 genetic polymorphism and sufentanil consumption. This might be helpful for optimizing the anesthesia strategies and reducing their side effects.

Correlations between CYP3A4 polymorphism and susceptibility to breast cancer in Chinese Han population

BACKGROUND

CYP3A4 is a major enzyme catalyzing the metabolism of endogenous steroids that play an important role in the etiology of carcinogenesis. This study was designed to investigate the contribution of CYP3A4 polymorphism to breast cancer in Chinese Han female population.

METHODS

To examine whether variants of CYP3A4 contribute to breast cancer, 5 single-nucleotide polymorphisms (SNPs) of CYP3A4 were genotyped by Sequenom MassARRAY in 267 breast cancer patients and 302 healthy controls. Odds ratio (OR) and 95% confidence intervals (CIs) were calculated by unconditional logistic regression adjusted for age.

RESULTS

We found that the TT genotype of CYP3A4*1G (rs2242480) polymorphism was associated with increased risk of breast cancer using the fixed effects model (recessive model: OR = 2.34, p = 0.018). Stratified according to age, CYP3A4*1G increased the risk of breast cancer especially in less than 50-year-old group (codominant model OR = 3.68, p = 0.041; recessive model: OR = 3.55, p = 0.012). Furthermore, TT genotype of rs2242480 was associated with Cerb-B2 positive (recessive model: OR = 2.47, p = 0.025) and stage I/II (recessive model: OR = 2.32, p = 0.041). However, no statistically significant associations in other polymorphisms and haploview analysis were observed.

CONCLUSIONS

This study provides an evidence for polymorphism of CYP3A4 gene associated with the development of breast cancer, also a new insight into etiology of breast cancer. However, the underlying mechanism of the CYP3A4 gene in breast cancer is necessary for further study.

Functional assessment of CYP3A4 allelic variants on lidocaine metabolism in vitro

Aim

Human cytochrome P450 3A4 is the most abundant isoform of P450 enzyme in the liver. It plays an important role in the metabolism of wide variety of xenobiotic and endogenous substrates. So far, there are few reports about the functional characterization of CYP3A4 variants in terms of specific substrates. The aim of this study was to systematically investigate the genetic polymorphisms of 23 CYP3A4 alleles and evaluate their catalytic activities on the metabolism of lidocaine in vitro.

Methods and results

The wild-type and 22 CYP3A4 variants were expressed in Spodoptera frugiperda 21 insect cells. Then the insect microsomes were incubated with the CYP3A4-specific substrate lidocaine. Reactions were performed with 50–3,000 µM for 60 min at 37°C. Lidocaine and its metabolite monoethylglycinexylidide were analyzed by ultra-performance liquid chromatography-tandem mass spectrometry system. Of the 23 CYP3A4 allelic variants tested, 2 variants (CYP3A4*17 and CYP3A4*30) had no detectable enzyme activity; and 5 variants (CYP3A4*2, CYP3A4*5, CYP3A4*9, CYP3A4*16 and CYP3A4*24) showed significantly decreased intrinsic clearance values compared with wild-type CYP3A4*1.

Conclusion

As the first study of all these CYP3A4 alleles for lidocaine metabolism, our results in vitro assessment may provide novel insights into the allele-specific and substrate-specific activity of CYP3A4 and may also offer a reference to the personalized treatment of lidocaine in a clinical setting.

A new donors' CYP3A5 and recipients' CYP3A4 cluster predicting tacrolimus disposition, and new-onset hypertension in Chinese liver transplant patients

AIM

The purpose of the current study was to investigate individualized therapy of tacrolimus (Tac), as well as complications after liver transplantation (LT) with the known genetic determinants and clinical factors.

METHODS

In this retrospective study, two cohorts (n=170) from the China Liver Transplant Registry (CLTR) database from July 2007 to March 2015 were included.

RESULTS

Both donors' CYP3A5*3 and recipients' CYP3A4*1G had a correlation with Tac pharmacokinetics at four weeks (all P<0.05), except recipients' CYP3A4*1G nearly had an association at week 2 (P=0.055). The model of donors' CYP3A5*3, recipients' CYP3A4*1G, and total bilirubin (TBL), for the prediction of Tac disposition, was better than donors' CYP3A5*3 only at week 1, 2, and 3 (P=0.010, P=0.007, and P=0.010, respectively), but not apparent at week 4 (P=0.297). Besides, when the P value was greater than or equal to 0.6685 after considering the false-positive rate R=10%, the patients were considered to have a faster metabolism, according to the mentioned model. Interestingly, we found that if more than or equal to two alleles A were present in the combination of donors' CYP3A5*3 and recipients' CYP3A4*1G genotype, there was a lower Tac C/D ration at week 1, 2, and 3 (P<0.001, P=0.001, and P<0.001), except at week 4 (P=0.082), and the probability of new-onset hypertension was lesser (P<0.001).

CONCLUSIONS

These data provided a potential basis for a comprehensive approach to predicting the Tac dose requirement in individual patients and provided a strategy for the effective prevention, early diagnosis of new-onset hypertension in Chinese LT recipients.

Genetic Polymorphisms Contribute to the Individual Variations of Imatinib Mesylate Plasma Levels and Adverse Reactions in Chinese GIST Patients

Imatinib mesylate (IM) has dramatically improved the outcomes of gastrointestinal stromal tumor (GIST) patients. However, the clinical responses of IM may considerably vary among single individuals. This study aimed to investigate the influences of genetic polymorphisms of drug-metabolizing enzyme (CYP3A4), transporters (ABCB1, ABCG2), and nuclear receptor (Pregnane X Receptor (PXR, encoded by NR1I2)) on IM plasma levels and related adverse reactions in Chinese GIST patients. A total of 68 Chinese GIST patients who have received IM 300–600 mg/day were genotyped for six single nucleotide polymorphisms (SNPs) (CYP3A4 rs2242480; ABCB1 rs1045642; ABCG2 rs2231137; NRI12 rs3814055, rs6785049, rs2276706), and the steady-state IM trough plasma concentrations were measured by a validated HPLC method. There were statistically significant variances in the steady-state IM trough plasma concentrations (from 272.22 to 4365.96 ng/mL). Subjects of GG in rs2242480, T allele carriers in rs1045642 and CC in rs3814055 had significantly higher steady-state IM dose-adjusted trough plasma concentrations. Subjects of CC in rs3814055 had significantly higher incidence rate of edema. The genetic polymorphisms of rs2242480, rs1045642, rs3814055 were significantly associated with IM plasma levels, and the genetic variations of rs3814055 were significantly associated with the incidence rate of edema in Chinese GIST patients. The current results may serve as valuable fundamental knowledge for IM therapy in Chinese GIST patients.

Systematic screening for CYP3A4 genetic polymorphisms in a Han Chinese population

Aim: To systematically investigate the genetic polymorphisms of the CYP3A4 gene in a Han Chinese population. Materials & methods: The promoter and exons of CYP3A4 gene in 1114 unrelated, healthy Han Chinese subjects were amplified and genotyped by direct sequencing. Results: In total, five previously reported alleles (*1G, *4, *5, *18B and *23) were detected, of which one allele (*23) was reported for the first time in Han Chinese population. Additionally, seven novel exonic variants were also identified and designated as new alleles CYP3A4*28–*34. Conclusion: This study provides the most comprehensive data of CYP3A4 polymorphisms in Han Chinese population and detects the largest number of novel CYP3A4 alleles in one ethnic group.

The relationship between pharmacokinetic parameters of carbamazepine and therapeutic response in epileptic patients

INTRODUCTION

The prescribed dose and carbamazepine plasma concentration to achieve the optimal therapeutic efficacy are highly variable from one patient to the other. Our study aimed to determine whether biological parameters may be used as plasma markers that can individually adjust the carbamazepine dose necessary to optimize therapeutic efficacy.

MATERIAL AND METHODS

Ninety-four epileptic patients under carbamazepine monotherapy and who have never used combination therapy were recruited from the consecutive admissions at the Department of Neurology "CHU Sahloul" of Sousse Central Hospital in Tunisia from February 2010 to April 2011. The patients were monitored for epilepsy for three years on average. Carbamazepine and 10,11-epoxide-carbamazepine concentrations were analyzed through high-performance liquid chromatography. Simultaneously, therapeutic efficacy was assessed through the annual number of seizures in each patient.

RESULTS

Our results showed the absence of any significant correlations between specific dose (mg/kg/day), carbamazepine plasma concentrations and therapeutic efficacy (r = 0.0025, p = 0.30; r = 0.1584, p = 0.38 respectively), whereas both plasma 10,11-epoxide-carbamazepine concentration and 10,11-epoxide-carbamazepine to plasma carbamazepine ratio were closely correlated with therapeutic efficacy (r = 0.34, p = 0.03; r = 0.45, p = 0.008 respectively). The optimum therapeutic response was observed among patients who simultaneously had a plasma concentration of 0.8 μg/ml of metabolite and 5.5 μg/ml of carbamazepine.

CONCLUSIONS

The results suggest that plasma levels of both carbamazepine and of 10,11-epoxide-carbamazepine must be set to achieve an optimum therapeutic response.

Patients with CYP3A4*1G genetic polymorphism consumed significantly lower amount of sufentanil in general anesthesia during lung resection

CYP3A4, an isoform of cytochrome P450 enzymes, is responsible for the metabolism of 45% to 60% of currently prescribed drugs. It has been shown that CYP3A4*1G, a single nucleotide polymorphism (SNP), affects the enzymatic activity of CYP3A4. Sufentanil, a synthetic opioid commonly used for the induction and maintenance of general anesthesia, analgesia, and sedation, is mainly metabolized by CYP3A4. So far, the impact of CYP3A4*1G on sufentanil metabolism has not been investigated. In the present study, we first determined the frequency of CYP3A4*1G polymorphism in patients of Chinese Han nationality who underwent lung resection, and then compared the amount of sufentanil used in general anesthesia during the surgical procedure between wild type and mutant patients.DNA sequencing was performed to genotype the CYP3A4*1G allele in 191 patients. The sufentanil dosages consumed in general anesthesia were recorded and compared between wild-type and mutant patients.The frequency of the CYP3A4*1G variant allele was 0.202 (77/382). No significant difference was observed in age, body weight, or operation time between wild-type and mutant patients. The amount of sufentanil consumed by patients with the point mutation was significantly lower than that in the wild type group. No significant difference in sufentanil dosages was observed between females and males within wild type or within mutant group.High frequency of CYP3A4*1G variants was detected in patients of Chinese Han nationality. Significantly lower amount of sufentanil was consumed in mutant patients compared with wild type subjects, likely a result of impaired CYP3A4 activity due to the point mutation. These findings suggest genotyping of CYP3A4 might be of value in providing guidance for the use of sufentanil.

Effect of polymorphisms in CYP3A4, PPARA, NR1I2, NFKB1, ABCG2 and SLCO1B1 on the pharmacokinetics of lovastatin in healthy Chinese volunteers

AIM

This study examined whether gene polymorphisms (CYP3A4, ABCG2, SLCO1B1, NR1I2, PPARA and NFKB1) influenced the pharmacokinetics of lovastatin in Chinese healthy subjects.

PATIENTS & METHOD

Plasma concentrations of lovastatin and lovastatin acid were quantified using LC/MS/MS.

RESULTS

PPARA c.208+3819 G allele carriers had approximately twofold higher AUC_0-∞ and C_max of lovastatin than wild-type (PPARA c.208+3819 AA) subjects. After adjustment for the PPARA variants, subjects with the SLCO1B1 521TT genotype had approximately 50% lower AUC_0-∞ of lovastatin acid than those with 521TC/CC genotypes, while the AUC_0-∞ of lovastatin lactone in NFKB1-94 DD wild-type carriers was twofold higher than in mutant homozygotes carriers.

CONCLUSION

Gene polymorphisms of PPARA, SLCO1B1 and NFKB1 affected the pharmacokinetics of lovastatin.

Genetic polymorphisms of CYP3A4 among Chinese patients with steroid-induced osteonecrosis of the femoral head

BACKGROUND

Steroid therapy has been an important reason of nontraumatic osteonecrosis of the femoral head (ONFH). Steroids are metabolized by hepatic cytochrome P4503A, a low endogenous activity of this enzyme can contribute to the pathogenesis of ONFH. The aim of this study was to investigate the associations of polymorphisms of cytochrome P4503A4 (CYP3A4) gene with steroid-induced ONFH in Chinese patients.

METHODS

A total of 150 steroid-induced ONFH patients and 250 healthy controls were enrolled. We evaluated 5 single-nucleotide polymorphisms of the CYP3A4 gene in this case-control study.

RESULTS

We identified rs2242480 in the CYP3A4 gene that was potentially associated with an increased risk of steroid-induced ONFH in the allele model (P = 0.023; odds ratio [OR]: 1.47; 95% confidence intervals [CI]: 1.05-2.04) and in the additive model (P = 0.028; OR: 1.44; 95% CI: 1.04-1.99) adjusted age + gender. Furthermore, we also observed a protective effect of haplotype "TG" (P = 0.025; OR: 0.69; 95% CI: 0.49-0.96) and a risk effect of haplotype "CG" (P = 0.006; OR: 1.81; 95% CI: 1.19-2.77) of the CYP3A4 gene adjusted age + gender.

CONCLUSION

These findings suggested that polymorphisms of CYP3A4 gene may be associated with susceptibility to steroid-induced ONFH.

Associations of CYP3A4, NR1I2, CYP2C19 and P2RY12 polymorphisms with clopidogrel resistance in Chinese patients with ischemic stroke

AIM

There is a high incidence of the antiplatelet drug clopidogrel resistance (CR) in Asian populations. Because clopidogrel is a prodrug, polymorphisms of genes encoding the enzymes involved in its biotransformation may be the primary influential factors. The goal of this study was to investigate the associations of polymorphisms of CYP3A4, NR1I2, CYP2C19 and P2RY12 genes with CR in Chinese patients with ischemic stroke.

METHODS

A total of 191 patients with ischemic stroke were enrolled. The patients were treated with clopidogrel for at least 5 days. Platelet function was measured by light transmission aggregometry. The SNPs NR1I2 (rs13059232), CYP3A4(*)1G (rs2242480), CYP2C19(*)2 (rs4244285) and P2RY12 (rs2046934) were genotyped.

RESULTS

The CR rate in this population was 36%. The CYP2C19(*)2 variant was a risk factor for CR ((*)2/(*)2+wt/(*)2 vs wt/wt, OR: 2.366, 95% CI: 1.180-4.741, P=0.014), whereas the CYP3A4(*)1G variant had a protective effect on CR ((*)1/(*)1 vs (*)1G/(*)1G+(*)1/(*)1G, OR: 2.360, 95% CI: 1.247-4.468, P=0.008). The NR1I2 (rs13059232) polymorphism was moderately associated with CR (CC vs TT+TC, OR: 0.533, 95% CI: 0.286-0.991, P=0.046). The C allele in P2RY12 (rs2046934) was predicted to be a protective factor for CR (CC+TC vs

TT, OR

0.407, 95% CI: 0.191-0.867, P=0.018). In addition, an association was found between hypertension and CR (P=0.022).

CONCLUSION

The individuals with both the CYP2C19(*)2 allele and hypertension are at high risk of CR during anti-thrombosis therapy. The CYP3A4(*)1G allele, P2RY12 (rs2046934) C allele and NR1I2 (rs13059232) CC genotype may be protective factors for CR. The associated SNPs studied may be useful to predict clopidogrel resistance in Chinese patients with ischemic stroke.

Pharmacodynamics, pharmacokinetics, and safety of ticagrelor in Chinese patients with stable coronary artery disease

AIM

The aim of the study was to assess ticagrelor's effects on inhibition of platelet aggregation (IPA), P2Y12 reaction units (PRU, measure of platelet P2Y12 receptor blockade), pharmacokinetic (PK) parameters and safety in Chinese patients with stable coronary artery disease (CAD).

METHODS

This was an open label, single centre, randomized study. Thirty-six patients on low dose aspirin (75-100 mg day(-1) ) received ticagrelor 45, 60 or 90 mg (single dose, days 1 and 7; twice daily, days 3-6). IPA (final extent), PRU and ticagrelor and AR-C124910XX plasma concentrations were determined.

RESULTS

On day 1, peak IPA >80% occurred 2-6 h post-dose (all doses). PRU was markedly reduced at 1 h vs. baseline (all doses). With ticagrelor 45 and 90 mg twice daily, maximum IPA (mean, SD) was 91% (13%), and 99% (3%), and maximum PRU reduction from baseline (mean, SD) was 82% (17%) and 92% (9%), respectively. Approximate dose-proportional increases (mean [%CV]; 45 vs. 90 mg twice daily) in ticagrelor Cmax (616 [37] vs. 1273 [43] ng ml(-1) ) and AUC (3882 [42] vs. 8206 [51] ng ml(-1) h) and AR-C124910XX parameters were seen. Pharmacodynamic and PK differences between 45 and 60 mg were small. No safety issues were identified.

CONCLUSIONS

In Chinese patients with CAD, ticagrelor (45, 60 and 90 mg) markedly reduced platelet aggregation. The IPA and PRU magnitude increased generally with increasing doses. However, the mean pharmacodynamic differences between 45 and 60 mg doses were small. Following single and multiple doses, the mean Cmax and AUC values of ticagrelor and AR-C124910XX increased approximately dose proportionally between 45 and 90 mg doses.

Polymorphic Variants of SCN1A and EPHX1 Influence Plasma Carbamazepine Concentration, Metabolism and Pharmacoresistance in a Population of Kosovar Albanian Epileptic Patients

Aim

The present study aimed to evaluate the effects of gene variants in key genes influencing pharmacokinetic and pharmacodynamic of carbamazepine (CBZ) on the response in patients with epilepsy.

Materials & Methods

Five SNPs in two candidate genes influencing CBZ transport and metabolism, namely ABCB1 or EPHX1, and CBZ response SCN1A (sodium channel) were genotyped in 145 epileptic patients treated with CBZ as monotherapy and 100 age and sex matched healthy controls. Plasma concentrations of CBZ, carbamazepine-10,11-epoxide (CBZE) and carbamazepine-10,11-trans dihydrodiol (CBZD) were determined by HPLC-UV-DAD and adjusted for CBZ dosage/kg of body weight.

Results

The presence of the SCN1A IVS5-91G>A variant allele is associated with increased epilepsy susceptibility. Furthermore, carriers of the SCN1A IVS5-91G>A variant or of EPHX1 c.337T>C variant presented significantly lower levels of plasma CBZ compared to carriers of the common alleles (0.71±0.28 vs 1.11±0.69 μg/mL per mg/Kg for SCN1A IVS5-91 AA vs GG and 0.76±0.16 vs 0.94±0.49 μg/mL per mg/Kg for EPHX1 c.337 CC vs TT; P<0.05 for both). Carriers of the EPHX1 c.416A>G showed a reduced microsomal epoxide hydrolase activity as reflected by a significantly decreased ratio of CBZD to CBZ (0.13±0.08 to 0.26±0.17, p<0.05) also of CBZD to CBZE (1.74±1.06 to 3.08±2.90; P<0.05) and CDR_CBZD (0.13±0.08 vs 0.24±0.19 μg/mL per mg/Kg; P<0.05). ABCB1 3455C>T SNP and SCN1A 3148A>G variants were not associated with significant changes in CBZ pharmacokinetic. Patients resistant to CBZ treatment showed increased dosage of CBZ (657±285 vs 489±231 mg/day; P<0.001) but also increased plasma levels of CBZ (9.84±4.37 vs 7.41±3.43 μg/mL; P<0.001) compared to patients responsive to CBZ treatment. CBZ resistance was not related to any of the SNPs investigated.

Conclusions

The SCN1A IVS5-91G>A SNP is associated with susceptibility to epilepsy. SNPs in EPHX1 gene are influencing CBZ metabolism and disposition. CBZ plasma levels are not an indicator of resistance to the therapy.

Liver toxicity during temozolomide chemotherapy caused by Chinese herbs

Background

Complementary and alternative medicine is often used by patients with malignant glioma. Although several interactions of various alternative agents with chemotherapy are known, none has been described for temozolomide so far.

Case presentation

We report the case of severe liver toxicity with jaundice during radiochemotherapy with temozolomide likely due to interaction with a popular Chinese herbal formula after surgery for glioblastoma. After cessation of the herbal formula as well as the chemotherapy liver enzymes slowly normalized. Due to tumor progression the patient was retreated with temozolomide for 5 cycles without toxicity. Because of further progression combination treatment of bevacizumab and irinotecan was started and again no liver toxicity was observed.

Conclusions

We conclude that the observed toxicity with jaundice was probably caused by an interaction of this popular Chinese formula and temozolomide. This is the first report about a relevant interaction of temozolomide and any herbal formula.

The Influence of MDR1 G2677T/a genetic polymorphisms on the pharmacokinetics of repaglinide in healthy Chinese volunteers

AIMS

The aim of this study was to evaluate the pharmacogenetic variability in the disposition of repaglinide in healthy Chinese subjects.

METHODS

A single dose of 2 mg repaglinide was orally administered to 24 healthy Chinese subjects. The serum concentrations of repaglinide were measured by using liquid chromatography/tandem mass spectrometry. We determined the polymorphic alleles of MDR1 C1236T, MDR1 G2677T/A, MDR1 C3435T, CYP3A4*18, OATP1B1 G388A, and OATP1B1 T521C in each subject.

RESULTS

The area under the plasma concentration-time curve from time 0 to infinity (AUC((0-inf))) of repaglinide was significantly higher in subjects possessing the MDR1 2677GT and 2677TT alleles than in those with the MDR1 2677GG and 2677TA alleles (p = 0.007). The mean AUCs and peak plasma concentration were higher in subjects with the 521TC allele than in those with the OATP1B1 521TT allele, and the OATP1B1 388A allele is associated with a reduced trend of pharmacokinetic exposure; however, these trends were not statistically significant. The pharmacokinetics of repaglinide was not associated with MDR1 C1236T, MDR1 C3435T, and CYP3A4*18.

CONCLUSION

This study shows that the genetic polymorphisms of MDR1 G2677T/A might explain the variability in the pharmacokinetics of repaglinide in the Chinese population.

Therapeutic drug monitoring for drugs used in the treatment of substance-related disorders: literature review using a therapeutic drug monitoring appropriateness rating scale

BACKGROUND

The efficacy of drugs for the treatment of substance-related disorders is moderate at best. Therapeutic drug monitoring (TDM) could be an instrument to improve outcomes. Because TDM for most of those drugs is not established, the authors reviewed the literature and built a rating scale to detect the potential added value of TDM for these pharmacologic agents.

METHODS

A literature search was performed for acamprosate, bupropion, buprenorphine, clomethiazole, disulfiram, methadone, naltrexone, and varenicline. The rating scale included 22 items and was divided in five categories: efficacy, toxicity, pharmacokinetics, patient characteristics, and cost-effectiveness. Three reference substances with established TDM were similarly assessed for comparison: clozapine, lithium, and nortriptyline. The three reference substances achieved scores of 15, 12, and 14 points, respectively.

RESULTS

Drugs for treatment of substance-related disorders achieved 3 to 17 points, 17 for methadone, 11 for buprenorphine, 10 for disulfiram, also 10 for naltrexone for the indication opioid-dependence and 9 for the indication alcohol dependence as well as bupropion, 7 points for acamprosate, 6 points for clomethiazole, and 3 for varenicline.

CONCLUSIONS

It is concluded that systematic evaluation of drug- and patient-related variables with the new rating scale can estimate the appropriateness of TDM. Because their rating revealed similar scores as the three reference drugs, it is proposed that TDM should be established for bupropion, buprenorphine, disulfiram or a metabolite, methadone, and naltrexone. An objective rating of drug- and patient-related characteristics could help laboratories focus their method development on the most likely drugs to require TDM along with a thorough drug use evaluation.

Analysis of CYP3A4 genetic polymorphisms in Han Chinese

Our study aimed to comprehensively investigate the genetic polymorphisms of CYP3A4 in Han Chinese. We sequenced the gene regions of CYP3A4, including its promoter, exons, surrounding introns and 3' untranslated region (3'UTR), from 100 unrelated-healthy Han Chinese individuals. We detected 11 SNPs, three of which are novel. According to in silico functional prediction of novel variants, 20148 A>G in exon 10, resulting in substitution of Tyr319 with Cys (CYP3A4*21), may induce dramatic alteration of protein conformation, and 26908 G>A in 3'UTR may disrupt post-transcriptional regulation. We identified five alleles in Han Chinese, the allele frequencies of CYP3A4*1, *5, *6, *18 and *21 are 97, 0.5, 1, 1 and 0.5%, respectively. Haplotype inference revealed 14 haplotypes, of which the major haplotype CYP3A4*1A constitutes 59% of the total chromosomes. We also examined the possible role of natural selection in shaping the variation of CYP3A4 and confirmed a trend, consistent with the action of positive selection. We systematically screened the genetic polymorphisms of CYP3A4 in Han Chinese, highlighted possible functional impairment of the novel allele and summarized the distinct allele and haplotype frequency distribution, with an emphasis on detecting the footprint of recent positive selection on the CYP3A4 gene in Han Chinese.

Impact of CYP3A4*1G polymorphism on metabolism of fentanyl in Chinese patients undergoing lower abdominal surgery

PURPOSE

This study aimed to investigate the impact of CYP3A4*1G genetic polymorphism on metabolism of fentanyl in Chinese patients undergoing lower abdominal surgery.

METHODS

176 patients receiving elective lower abdominal surgery under general anesthesia were recruited into this study. Genotyping of CYP3A4*1G was carried out by direct sequencing. The plasma fentanyl concentration was detected 30 min after anesthesia induction by high performance liquid chromatography-ultraviolet ray (HPLC-UV). The visual analog scale (VAS) was used for pain evaluation at rest during patient-controlled analgesia (PCA) treatment 0 h, 12 h and 24 h after operation. PCA fentanyl consumption and adverse effects were recorded during the first 24 h after surgery.

RESULTS

The frequency of CYP3A4*1G variant allele was 0.227 (80/352, 95% CI 0.165, 0.289) in these patients. After grouping according to the genotype of CYP3A4*1G, plasma fentanyl concentration in the *1/*1 variant (wild-type) group (12.8±6.5 ng/ml) was significantly lower than that in the *1/*1G group (16.8±9.0 ng/ml, P<0.01) and the *1G/*1G group (28.1±9.5 ng/ml, P<0.01). Patients in the *1G/*1G group (247.1±73.2 μg) consumed significantly less fentanyl than that in either the wild-type group (395.0±138.5 μg) or the *1/*1G group (359.8±120.2 μg) (P<0.01). There was a significant correlation between plasma fentanyl concentration and PCA fentanyl consumption (r=-0.552, P<0.001).

CONCLUSIONS

CYP3A4*1G polymorphism is related to the pharmacokinetics of fentanyl, and patients with CYP3A4*1G variant A allele have a lower metabolic rate of fentanyl. The specific CYP3A4*1G polymorphism may predict the individual requirement of fentanyl.

Relationship between response to risperidone, plasma concentrations of risperidone and CYP3A4 polymorphisms in schizophrenia patients

In this study, we examined the relationships between plasma concentrations of risperidone and 9-hydroxyrisperidone and polymorphisms of CYP3A4. All 130 schizophrenia patients (45 men, 85 women, age 15-60 years) who met DSM-IV criteria were given risperidone for 8 weeks. Clinical efficacy was determined using the Positive and Negative Syndrome Scale (PANSS). CYP3A4*1G was found to be associated with the change in total PANSS scores (Kruskal-Wallis test, P = 0.021), which was not significant on adjusting for multiple testing. Our study has, for the first time, conducted a genetic association study of the CYP3A4 gene with risperidone response. Further studies on larger groups and on the effects of the longer term risperidone treatment are needed to confirm these results.

A case-control association study between the CYP3A4 and CYP3A5 genes and schizophrenia in the Chinese Han population

In this study, variants of two genes coding for cytochrome P450 enzyme (CYP3A4 and CYP3A5) were analysed in a case-control sample using 398 schizophrenic patients and 391 healthy controls. All subjects were unrelated Han Chinese from Shanghai. No difference was observed on the allelic or genotypic distribution of CYP3A4 and CYP3A5 gene polymorphisms between the groups. However, the two-marker haplotypes covering components CYP3A41G and CYP3A53 were observed to be significantly associated with schizophrenia (corrected global p=0.0009). In addition, we identified one common risk haplotype, G/G (present in 59.5% of the general population). The results suggest that CYP3A4 and CYP3A5 might play a role in genetic susceptibility to schizophrenia. However, confirmatory studies in independent samples are needed.

Incidence of genetic polymorphisms involved in lipid metabolism among Chinese patients with osteonecrosis of the femoral head

BACKGROUND AND PURPOSE Corticosteroid treatment is associated with osteonecrosis of the femoral head (ON) in certain patients. The degree of drug sensitivity in general is governed by genetic variation between individuals. We investigated the relationship between ON and the presence of different alleles of the cytochrome P450 gene (CYP3A4), the product of which metabolizes corticosteroids, and of the P-glycoprotein (P-gp) gene (ABCBI), the product of which modulates cellular uptake of corticosteroids, to determine whether patients with certain alleles may be at higher risk of ON after corticosteroid treatment.

METHODS

We studied 31 patients from Guangdong, China who were both treated with corticosteroid therapy and developed ON, and 17 corticosteroid-therapy patients without ON. Patient DNA was screened for known polymorphisms in the CYP3A4 gene (CYP3A4*4, CYP3A4*5, CYP3A4*6) and the P-gp gene ABCB1 (mutations C3435T, G2677T/A).

RESULTS

The majority (20/31) of the corticosteroid-treated patients who developed ON were heterozygous for ABCB1, whereas only 3/17 without ON were heterozygous. Statistical significance was observed between the ON and the control groups for the ABCB1 G2677T/A polymorphism. Analysis of haplotypic frequencies indicated significant linkage disequilibrium between the two ABCB1 polymorphisms, C3435T and G2677T/A (D' = 0.034). No CYP3A4 polymorphisms were detected in any of the patients.

INTERPRETATION

Patients carrying an ABCB1 polymorphism had a higher risk of having corticosteroid-associated ON than those with wild-type genotypes. This statistically significant association conflicts with previous studies, possibly due to different sampling methods. Knowing which genetic backgrounds are most strongly associated with corticosteroid-associated ON provides a method of screening for patients who are most at risk of developing ON.

The CYP3A4*18 allele, the most frequent coding variant in asian populations, does not significantly affect the midazolam disposition in heterozygous individuals

The objective of this study was to identify CYP3A4 variants in Koreans and to characterize their functional consequences in vitro and in vivo. Four single nucleotide polymorphisms were identified in 50 Koreans by direct DNA sequencing. In an additional genotyping using 248 subjects, CYP3A4(*)18 was confirmed as the most frequent coding variant in Koreans at 1.7%, and its frequency was similar to that of Asians, suggesting that CYP3A4(*)18 would be the highest coding variant in Asians. The recombinant CYP3A4.18 protein prepared in baculovirus expression system showed 67.4% lower Vmax and 1.8-fold higher K(m) for midazolam 1'-hydroxylation compared with the wild type. The mean values of Cmax and area under the concentration curve (AUC) in the CYP3A4(*)1/(*)18 and CYP3A5(*)1/(*)3 subjects (n = 8) were 63% and 32% higher than in CYP3A4(*)1/(*)1 and CYP3A5(*)1/(*)3 carriers (n = 8), respectively. Although the in vitro assay exhibited a significant reduction of the enzyme activity for midazolam, the in vivo differences associated with the CYP3A4(*)1/(*)18 tend to be low (P < 0.07 in Cmax and P < 0.09 in AUC). In summary, the heterozygous CYP3A4(*)1/(*)18 does not appear to cause a significant change of midazolam disposition in vivo; however, the clinical relevance of CYP3A4(*)18/(*)18 remains to be evaluated.