Association between gene polymorphisms and initial warfarin therapy in patients after heart valve surgery

BACKGROUND

Warfarin is widely used for the prevention and treatment of thrombotic events. This study aimed to examine the influence of gene polymorphisms on the early stage of warfarin therapy in patients following heart valve surgery.

METHODS

Nine single nucleotide polymorphisms were genotyped using microarray chips, categorizing patients into three groups: normal responders (Group I), sensitive responders (Group II), and highly sensitive responders (Group III). The primary clinical outcomes examined were time in therapeutic range (TTR) and international normalized ratio (INR) variability. To investigate potential influencing factors, a generalized linear regression model was employed.

RESULTS

Among 734 patients, the prevalence of CYP2C9*3-1075A > C, CYP2C19*3-636G > A, and CYP2C19*17-806C > T variants were 11.2%, 9.9%, and 1.9% of patients, respectively. VKORC1-1639G > A or the linked -1173C > T variant was observed in 99.0% of the patients. Generalized linear model analysis revealed an impact of sensitivity grouping on INR variability. Compared to Group I, Group II showed higher TTR values (p = 0.023), while INR variability was poorer in Group II (p < 0.001) and Group III (p < 0.001). Individual gene analysis identified significant associations between CYP2C9*3-1075A > C (p < 0.001), VKORC1-1639G > A or the linked -1173 C > T (p = 0.009) and GGCX-3261G > A (p = 0.019) with INR variability.

CONCLUSION

The genotypes of CYP2C9, VKORC1, and GGCX were found to have a significant impact on INR variability during the initial phase of warfarin therapy. However, no significant association was observed between TTR and gene polymorphisms. These findings suggest that focusing on INR variability is crucial in clinical practice, and preoperative detection of gene polymorphisms should be considered to assist in the initiation of warfarin therapy.

Development of a laboratory-based pharmacogenomics independent study and advanced pharmacy practice experience: Connecting basic science to clinical application

BACKGROUND AND PURPOSE

The role of pharmacists in pharmacogenomics (PGx) use clinically is expanding, leading to increased pharmacy education requirements. Current reports indicate that PGx is primarily taught through didactic courses, indicating a need for applied coursework in pharmacy curricula, including laboratory exercises and clinical experiences. Such courses are instrumental in helping students connect the science of PGx to patient care.

EDUCATIONAL ACTIVITY AND SETTING

An advanced PGx independent study and a similar advanced pharmacy practice experience (APPE) were developed. These courses included personal genetic testing, raw genetic sequence data analysis, and wet-laboratory genetic testing. The APPE included sessions with clinical pharmacists who use PGx and a genetic counselor, as well as a visit to a genetic reference laboratory. A pre-/post-examination and survey were used to measure the courses' effectiveness and student perceptions of their abilities, PGx, and course components. For this pilot study one student per course was evaluated.

FINDINGS

Each student completed all components of the courses successfully, supporting the feasibility of their implementation. Examination scores increased for both students with improvement in knowledge from basic genetics to clinical application. Both students also had a more positive perception of PGx after the courses and valued the various course components.

SUMMARY

Through this unique course format, pharmacy students developed expertise in understanding and implementing PGx which allowed them to gain skills that go beyond an introductory course. Our experience may provide guidance to other pharmacy programs in adding more applied PGx education to their curricula.

The impact of CYP2C9 and VKORC1 genetic polymorphisms in anticoagulant therapy management after cardiac surgery with extracorporeal circulation

Extracorporeal circulation during cardiac surgery is characterized with increased risk for hypercoagulation because blood is exposed to foreign, nonendothelial cell surfaces. Thus, the usage of extracorporeal circulation is essentially not possible without anticoagulation. Open-heart surgery as well as many perioperative factors, such as acidosis, hypocalcemia, hypothermia, and hemodilution, might affect hemostasis and lead to coagulopathy and bleeding. A new insight into the effectiveness of anticoagulant therapy is applied to modify the dosing regimen with respect to the genetic CYP2C9 and VKORC1allelic variants. A systematic literature search was performed for VKORC1 and CYP2C9 and their association with coumarin anticoagulant therapy and bleeding risk in postoperative period of cardiac surgery with extracorporeal circulation.

Pharmacogenetic-Guided Algorithm to Improve Daily Dose of Warfarin in Elder Han-Chinese Population

Objectives

To verify the accuracy of the International Warfarin Pharmacogenetics Consortium (IWPC) algorithm, identify the effects of genetic and clinical factors on warfarin stable dose, and to establish a new warfarin stable dose prediction algorithm for the elderly Han-Chinese population under the guidance of pharmacogenetics.

Methods

According to the inclusion criteria, 544 non-valvular atrial fibrillation patients taking warfarin for anticoagulation treatment were enrolled. Data information of three groups including the whole population, people under 65 years old and over 65 years old were substituted into the IWPC algorithm respectively to verify its accuracy. The basic data and clinical information of 360 elderly people were collected for statistical analysis and the genotypes of VKORC1-G1639A and CYP2C9 were detected by Sanger sequencing. The new algorithm of the elder pharmacogenetics warfarin dosing was obtained by stepwise multiple regression. The determination coefficient (R2), root mean squared error (RMSE), and the proportion of the predicted value within the true value range of ±20%(20%-p) were used to evaluate the accuracy of the IWPC algorithm and the new algorithm.

Results

Among the three different age groups, the warfarin stable dose predictive accuracy of IWPC algorithm was the lowest in the elderly patients above 65-year-old. In this study, the important factors influencing the stable dose of warfarin in the elderly Han-Chinese were height, weight, body surface area, serum creatinine level, amiodarone usage, CYP2C9 (*1*2, *1*3), and VKORC1 (GG/GA) genotypes. By means of stepwise multiple regression analysis, we established a new elder warfarin dosing algorithm (R²=0.3714) containing height, creatinine, amiodarone usage, CYP2C9 (*1*2 or *1*3), and VKORC1 (GA or GG) genotypes. The prediction accuracy and clinical availability of the Elderly algorithm was significantly better than that of IWPC algorithm verified by RMSE, R2, and (20%-p) methods.

Conclusions

The IWPC model may not be suitable for the elder Han-Chinese population. Polymorphism of CYP2C9 and VKORC1 obviously affected warfarin stable dose of the elder Han-Chinese. Combination of genetic data with demographic and clinical factors could help to better improve warfarin doses in the elder Han-Chinese population.

The effects of CYP2C9 and VKORC1 gene polymorphisms on warfarin maintenance dose in Turkish cardiac patients

Aim: Our aim was to examine the effect of CYP2C9 and VKORC1 polymorphisms on warfarin dose requirements in Turkish patients. Materials & methods: 24 warfarin prescribed patients were included and analyzed for eight VKORC1 and 6 CYP2C9 polymorphisms in the study. Results: Patients with CYP2C9 *1/*1 and VKORC1 -1639 GG and GA genotypes required higher warfarin doses in comparison to wild type VKORC1 genotype. Patients with CYP2C9 *1/*3 and VKORC1 -1639 GG genotypes simultaneously, required the lowest dose of warfarin (4.64 mg/day). Patients with CYP2C9 *1/*1 and VKORC1 9041 AA genotype were found to require higher warfarin doses. Conclusion: Our results provide additional evidence to support the hypothesis that CYP2C9 *2, *3, VKORC1 9041 G > A polymorphisms explain considerable proportion of inter-individual variability in warfarin dose requirement.

Effects of EPHX1 rs2260863 polymorphisms on warfarin maintenance dose in very elderly, frail Han-Chinese population

Aim: This study was conducted to investigate the effects of VKORC1, CYP2C9, CYP4F2 and EPHX1 and nongenetic factors on warfarin maintenance dose in a very elderly, frail Han-Chinese population. Materials & methods: 16 variants of VKORC1, CYP2C9, CYP4F2 and EPHX1 were genotyped. Univariate analysis and multivariable regression model were performed for the associations of gene variants and warfarin maintenance dose. Results & conclusion: EPHX1 rs2260863 nonvariant CC homozygotes required significantly lower daily warfarin dose than GC heterozygotes. In the multivariable model, VKORC1 rs9923231, CYP2C9 rs1057910, EPHX1 rs2260863, CYP4F2 rs2189784 and body surface area altogether explained 26.9% of dosing variability. This study revealed the main impact of genetic factors on warfarin response in this special population.

A Two-Sequence, Four-Period, Crossover, Replicate Study to Demonstrate Bioequivalence of Warfarin Sodium Tablet in Healthy Chinese Subjects Under Fasting and Fed Conditions

Warfarin is a narrow therapeutic index anticoagulant drug, and several generic formulations have been approved worldwide. However, there has been no report evaluating the bioequivalence of warfarin sodium according to US Food and Drug Administration draft guidance. We designed a 2-sequence and 4-period crossover study to compare the pharmacokinetic profile and assess bioequivalence between the test warfarin sodium tablet and reference product Coumadin (2.5 mg) in 56 healthy Chinese subjects under fasting and fed conditions. The plasma concentration of warfarin was analyzed by a validated liquid chromatography-tandem mass spectrometry assay, and the reference-scaled procedure was used to determine bioequivalence for the pharmacokinetics parameters. The results showed that the point estimate of geometric mean ratios of C_max and AUC_0-t for warfarin were 103.21% and 99.31%, respectively, in the fasting condition and 100.62% and 98.98%, respectively, in the fed condition, and the 90% confidence intervals were all within the range of 90.00%-111.11%. The upper limit of the 90% confidence interval of estimated within-subject variation ratios of the test and reference products was 1.33 for C_max and 2.22 for AUC_0-t under the fasting condition and 1.68 for C_max and 2.15 for AUC_0-t under the fed condition. Overall, bioequivalence of the 2 warfarin sodium products was demonstrated.

Arachidonic Acid Metabolism and Kidney Inflammation

As a major component of cell membrane lipids, Arachidonic acid (AA), being a major component of the cell membrane lipid content, is mainly metabolized by three kinds of enzymes: cyclooxygenase (COX), lipoxygenase (LOX), and cytochrome P450 (CYP450) enzymes. Based on these three metabolic pathways, AA could be converted into various metabolites that trigger different inflammatory responses. In the kidney, prostaglandins (PG), thromboxane (Tx), leukotrienes (LTs) and hydroxyeicosatetraenoic acids (HETEs) are the major metabolites generated from AA. An increased level of prostaglandins (PGs), TxA₂ and leukotriene B4 (LTB₄) results in inflammatory damage to the kidney. Moreover, the LTB₄-leukotriene B4 receptor 1 (BLT1) axis participates in the acute kidney injury via mediating the recruitment of renal neutrophils. In addition, AA can regulate renal ion transport through 19-hydroxystilbenetetraenoic acid (19-HETE) and 20-HETE, both of which are produced by cytochrome P450 monooxygenase. Epoxyeicosatrienoic acids (EETs) generated by the CYP450 enzyme also plays a paramount role in the kidney damage during the inflammation process. For example, 14 and 15-EET mitigated ischemia/reperfusion-caused renal tubular epithelial cell damage. Many drug candidates that target the AA metabolism pathways are being developed to treat kidney inflammation. These observations support an extraordinary interest in a wide range of studies on drug interventions aiming to control AA metabolism and kidney inflammation.

Association between four microRNA binding site-related polymorphisms and the risk of warfarin-induced bleeding complications

Bleeding is the most serious complication of warfarin anticoagulation therapy and is known to occur even at patients with therapeutic international normalized ratio (INR) range. Recently, it has been shown that microRNAs play a significant role in pharmacogenetics by regulating genes that are critical for drug function. Interaction between microRNAs and these target genes could be affected by single-nucleotide polymorphisms (SNPs) located in microRNA-binding sites. This study focused on 3′-untranslated region (3′-UTR) SNPs of the genes involved in the warfarin action and the occurrence of bleeding complications in an Iranian population receiving warfarin. A total of 526 patients under warfarin anticoagulation therapy with responding to the therapeutic dose and maintenance of the INR in the range of 2.0-3.5 in three consecutive blood tests were included in the study. Four selected 3'-UTR SNPs (rs12458, rs7294, rs1868774 and rs34669593 located in GATA4, VKORC1, CALU and GGCX genes, respectively) with the potential to disrupt/eliminate or enhance/create microRNA-binding site were genotyped using a simple PCR-based restriction fragment length polymorphism (PCR-RFLP) method. Patients with the rs12458 AT or TT genotypes of the GATA4 gene had a lower risk of bleeding compared to patients with the AA genotype (adjusted OR: 0.478, 95% CI: 0.285-0.802, P= 0.005, OR: 0.416, 95% CI: 0.192-0.902, P= 0.026, respectively). 3'-UTR polymorphisms in other genes were not significantly associated with the risk of bleeding complications. In conclusion, the SNP rs12458A>T in the 3′UTR region of GATA4 is associated with the incidence of warfarin-related bleeding at target range of INR, likely by altering microRNA binding and warfarin metabolism. Further genetics association studies are needed to validate these findings before they can be implemented in clinical settings.