Clinical Pharmacogenetics Implementation Consortium (CPIC) Guideline for Pharmacogenetics-Guided Warfarin Dosing: 2017 Update

Effects of Crocus sativus and its active constituents on cytochrome P450: a review

Cytochrome P450 (CYP) enzymes play an important role in the biotransformation of drugs and endogenous substances. Clinical medications and herbal remedies can either enhance or inhibit the activity of CYP enzymes, leading to potential drug interactions between herbal supplements and prescribed medications. Such interactions can lead to serious consequences, especially for drugs with a narrow therapeutic index, such as digoxin, warfarin, and cyclosporine A. In this review article, we provide an updated review of the impact of saffron, and its active constituents, safranal and crocin, on the 12 major human CYP enzymes and possible drug interactions between saffron and prescription drugs. The available evidence indicates that saffron and its active constituents affect the expression or activity of some CYP isoforms, including the CYP1A1/2, CYP3A4, and CYP2E1 subfamily. Considering the important role of these CYPs in the biotransformation of frequently prescribed medications and the activation of procarcinogen into carcinogenic metabolites, it can be expected that the consumption of saffron and its active constituents may influence the pharmacokinetics and toxicity of several substances. In particular, given the critical role of CYP3A4 in drug metabolism, and saffron's inhibitory impact on this CYP enzyme, it appears that saffron's most significant interaction is linked to its inhibition of CYP3A4. In addition, the inhibitory effect of saffron on CYP1A1/2, and CYP2E1 expression can play a role in the chemopreventive effect of this herbal medicine. Additional research is crucial for evaluating the clinical significance of these interactions in patients who consume saffron along with prescription drugs and determining the dose that can lead to drug interactions.

Local ancestry informed GWAS of warfarin dose requirement in African Americans identifies a novel CYP2C19 splice QTL

African Americans (AAs) are underrepresented in pharmacogenomics which has led to a significant gap in knowledge. AAs are admixed and can inherit specific loci from either their African or European ancestor, known as local ancestry (LA). A previous study in AAs identified single nucleotide polymorphisms (SNPs) located in the CYP2C cluster that are associated with warfarin dose. However, LA was not considered in this study. An IWPC cohort (N=340) was used to determine the LA-adjusted association with warfarin dose. Ancestry-specific GWAS's were conducted with TRACTOR and ancestry tracts were meta-analyzed using METAL. We replicated top associations in the independent ACCOuNT cohort of AAs (N=309) and validated associations in a warfarin pharmacokinetic study in AAs. To elucidate functional roles of top associations, we performed short-read RNA-sequencing from AA hepatocytes carrying each genotype for expression of CYP2C9 and CYP2C19. We identified 6 novel genome-wide significant SNPs (P<5E-8) in the CYP2C locus (lead SNP, rs7906871 (P=3.14E-8)). These associations were replicated (P≤2.76E-5) and validated with a pharmacokinetic association for S-Warfarin concentration in plasma (P=0.048). rs7906871 explains 6.0% of the variability in warfarin dose in AAs. Multivariate regression including rs7906871, previously associated SNPs, clinical and demographic factors explain 37% of dose variability, greater than previously reported studies in AAs. RNA-seq data in AA hepatocytes identified a significant alternate exon inclusion event between exons 6 and 7 in CYP2C19 for carriers of rs7906871. In conclusion, we have found and replicated a novel CYP2C variant associated with warfarin dose requirement and potential functional consequences to CYP2C19.

Pharmacogenetic Influences on Individual Responses to Ocular Hypotensive Agents in Glaucoma Patients

Background/Objectives: To analyze the genotype that predicts the phenotypic characteristics of a cohort of patients with glaucoma and ocular hypertension (OHT) and explore their influence on the response to ocular hypotensive treatment. Methods: This was a prospective study that included 193 eyes of 109 patients with glaucoma or OHT under monotherapy with beta-blockers, prostaglandin, or prostamide analogues (BBs, PGAs, PDs). Eight single-nucleotide polymorphisms were genotyped using real-time PCR assays: prostaglandin-F2α receptor (PTGFR) (rs3766355, rs3753380); beta-2-adrenergic receptor (ADRB2) (rs1042714); and cytochrome P450 2D6 (CYP2D6) (*2 rs16947; *35 rs769258; *4 rs3892097; *9 rs5030656, and *41 rs28371725). The main variables studied were baseline (bIOP), treated (tIOP), and rate of variation in intraocular pressure (vIOP), and mean deviation of the visual field (MD). The metabolizer phenotype and the CYP2D6 copy number variation were also evaluated. Results: In total, 112 eyes were treated with PGAs (58.0%), 59 with BBs (30.6%), and 22 with PDs (11.4%). For PTGFR (rs3753380), statistically significant differences were observed in vIOP in the PGA group (p = 0.032). Differences were also observed for ADRB2 (rs1042714) in MD (p < 0.001) and vIOP (p = 0.017). For CYP2D6, ultrarapid metabolizers exhibited higher tIOP (p = 0.010) and lower vIOP (p = 0.046) compared to the intermediate and poor metabolizers of the BB group. Additionally, systemic treatment metabolized by CYP2D6 showed a significant influence on vIOP (p = 0.019) in this group. Conclusions: These preliminary findings suggest the future potential of pharmacogenetic-based treatments in glaucoma to achieve personalized treatment for each patient, and thus optimal clinical management.

Pre-emptive pharmacogenetic testing in the acute hospital setting: a cross-sectional study

BACKGROUND

Pharmacogenetic-guided prescribing can be used to improve the safety and effectiveness of medicines. There are several approaches by which this intervention might be implemented in clinical practice, which will vary depending on the health system and clinical context.

AIM

To understand the clinical utility of panel-based pharmacogenetic testing in patients admitted acutely to hospital and to establish variables that predict if an individual might benefit from the intervention.

DESIGN

A cross-sectional study recruiting patients admitted acutely to hospital.

METHODS

Participants underwent panel-based pharmacogenetic testing, and their genetic results were analysed in their context of the medicines they had been exposed to as an inpatient. The primary outcome was the proportion of patients with clinically actionable gene-drug interactions. Individual variables that predict the clinical utility of pharmacogenetic testing were established via logistic regression.

RESULTS

Genetic and prescribing data were available for 482 inpatients (55% male; median age 61.2 years; range: 18-96), 97.9% of whom carried a pharmacogenetic result of interest. During their admission, 79.5% of patients were exposed to a medicine for which there is pharmacogenetic prescribing guidance available. Just under one in seven individuals (13.7%) had a clinically actionable gene-drug interaction. Increasing age (>50 years) was positively correlated with the likelihood (2.7-fold increased risk) of having a clinically actionable interaction.

CONCLUSIONS

These findings demonstrate the potential scale, and potential clinical utility, of pharmacogenetic testing as an intervention, highlighting the need to develop infrastructure to support healthcare professionals make use of this emerging tool.

Clinical Pharmacogenetic Testing and Application: 2024 Updated Guidelines by the Korean Society for Laboratory Medicine

In the era of precision medicine, pharmacogenetics has substantial potential for addressing inter-individual variability in drug responses. Although pharmacogenetics has been a research focus for many years, resulting in the establishment of several formal guidelines, its clinical implementation remains limited to several gene-drug combinations in most countries, including Korea. The main causes of delayed implementation are technical challenges in genotyping and knowledge gaps among healthcare providers; therefore, clinical laboratories play a critical role in the timely implementation of pharmacogenetics. This paper presents an update of the Clinical Pharmacogenetic Testing and Application guidelines issued by the Korean Society for Laboratory Medicine and aims to provide the necessary information for clinical laboratories planning to implement or expand their pharmacogenetic testing. Current knowledge regarding nomenclature, gene-drug relationships, genotyping technologies, testing strategies, methods for clinically relevant information delivery, QC, and reimbursements has been curated and described in this guideline.

A Chinese patient with cardiogenic stroke and warfarin resistance: a case report

BACKGROUND

Warfarin is the most commonly used oral anticoagulant drug in clinical practice due to its effective anticoagulant effect and low cost. Warfarin plays a crucial role in the anticoagulant treatment of patients with thrombotic diseases such as atrial fibrillation, heart valve replacement, and deep vein thrombosis. In general, low-dose warfarin can effectively achieve the optimal international normalized ratio (INR) for patients requiring anticoagulation therapy. In some cases, patients may require significantly higher doses of warfarin to achieve an INR in the desired range; failure to achieve this is commonly referred to as warfarin resistance. We report a rare case of cerebral infarction caused by atrial fibrillation and warfarin resistance in China.

CASE PRESENTATION

A Chinese patient with atrial fibrillation complicated by cerebral infarction had been taking warfarin for 2 years, and the dose was gradually increased to 12.5 mg per day; however, the INR remained below the standard. The patient was considered to be resistant to warfarin. The cause of warfarin resistance in this patient is unknown, but we speculate that pharmacodynamic and genetic factors may be involved. Finally, we chose to replace warfarin with rivaroxaban to avoid the risk of bleeding at high doses. To date, there has been no bleeding or infarcts since the patient was discharged. In cases where the cause of warfarin resistance cannot be determined, alternative drugs may be more appropriate.

CONCLUSIONS

When considering warfarin resistance, it is important to actively search for the cause of resistance early on. If the cause is determined, appropriate measures should be taken. If the cause is not determined or cannot be resolved, the dose can be gradually increased under close monitoring, alternatives can be actively adopted, and patients can be informed and educated.

The Association Between Promoter Tandem Repeat Polymorphism (pVNTR) and CYP2C9 Gene Expression in Human Liver Samples

CYP2C9 metabolizes approximately 20% of clinically administered drugs. Several single-nucleotide polymorphisms (SNPs) of CYP2C9 (e.g., *2, *3, *8, and rs12777823) are used as biomarkers to predict CYP2C9 activity. However, a large proportion of variability in CYP2C9 expression remains unexplained.

BACKGROUND/OBJECTIVES

We previously identified a variable number tandem repeat (pVNTR) polymorphism in the CYP2C9 promoter. The short repeat (pVNTR-S) showed reduced transcriptional activity in reporter gene assays and was associated with decreased CYP2C9 mRNA expression. However, because pVNTR-S is in high linkage disequilibrium (LD) with CYP2C9*3 in the European population, whether pVNTR-S directly impacts CYP2C9 expression remains unclear. The objective of this study was to clarify the association between the pVNTR-S and CYP2C9 mRNA expression in human liver samples and to assess its impact on CYP2C9 expression independently of known CYP2C9 biomarkers.

METHODS

Gene expression was measured by real-time qPCR. SNPs and pVNTRs were genotyped using SNapShot assays and fragment analysis, respectively. Associations between CYP2C9 and the pVNTR-S or SNPs were analyzed using multiple linear regression.

RESULTS

Our results showed that pVNTR-S was associated with lower CYP2C9 expression (34% reduction, p-value = 0.032) in human liver samples (n = 247), while the known CYP2C9 biomarkers (CYP2C9*2, *3, *8, or rs12777823) were not. These results suggest that pVNTR-S reduces CYP2C9 expression independently of known biomarkers. Therefore, pVNTR-S may explain additional variability in CYP2C9 expression when present alone or in conjunction with other CYP2C9 alleles.

Efficacy and safety of anticoagulation in asymptomatic cirrhotic patients with portal vein thrombosis: a systematic review and meta-analysis

BACKGROUND

The role of anticoagulation in asymptomatic cirrhotic patients with portal vein thrombosis (PVT) remains unclear. This study aims to evaluate the efficacy and safety of anticoagulation in this patient population.

METHODS

We systematically searched PubMed, Web of Science, Cochrane Library, and Embase up to August 2024. The primary outcomes analyzed were PVT recanalization, progression of PVT, bleeding events, and mortality. Odds ratios (OR) with 95% confidence intervals (CI) were calculated for dichotomous variables.

RESULTS

Seventeen studies, including randomized controlled trials (RCTs) and observational studies, were included in the analysis. Compared to no intervention, anticoagulation significantly increased the PVT recanalization rate (OR = 3.89, p < .001) and decreased the PVT progression rate (OR = 0.28, p < .001) as well as overall mortality (OR = 0.66, p = .008). Importantly, anticoagulation did not significantly increase the bleeding rate (OR = 1.21, p = .41). Subgroup analysis revealed a greater benefit in PVT recanalization within the short-term treatment subgroup (≤ 6 months) compared to long-term treatment subgroup (> 6 months), and in the Asian subgroup compared to the European or United States of America (USA) subgroup. In the Warfarin subgroup, while the total bleeding rate increased significantly, there was no significant rise in major bleeding events. Additionally, a downward trend in variceal bleeding was observed in the Asian subgroup (OR = 0.44; 95% CI: 0.19-1.04; p = .06).

CONCLUSION

Anticoagulation is both safe and effective for asymptomatic cirrhotic patients with PVT. It not only treats PVT and reduces all-cause mortality, but also does so without significantly increasing the risk of bleeding events.

Impact of Genetic Variants on Pregabalin Pharmacokinetics and Safety

Background/Objectives: Pregabalin is a useful therapeutic option for patients with anxiety or neuropathic pain. Genetic variants in certain genes encoding for transporters related to absorption and distribution could have an impact on the efficacy and safety of the drug. Furthermore, extreme phenotypes in metabolic enzymes could alter pregabalin-limited metabolism. Methods: In this study, we included 24 healthy volunteers participating in a bioequivalence clinical trial and administered pregabalin 300 mg orally; 23 subjects were genotyped for 114 variants in 31 candidate genes, and we explored their impact on pregabalin pharmacokinetics and safety. Results: The uncorrected mean (±SD) of AUC∞ and Cmax were 61,097 ± 14,762 ng*h/mL and 7802 ± 1659 ng/mL, respectively, which were significantly higher in females than in males (p = 0.002 and p = 0.001, respectively), with no differences in dose/weight (DW)- corrected exposure metrics. NAT2 slow acetylators (SAs) showed a 16-18% increase in exposure compared to intermediate (IAs) and normal (NAs) acetylators; NAT2 SAs exhibited a 25% higher t1/2 as compared with NAT2 IAs and 58% higher compared to NAT2 NAs. In contrast, neither the NAT2 phenotype nor other genetic variants were related to pregabalin adverse drug reaction (ADR) occurrence. On the contrary, sex and sex-related exposure differences (i.e., females and their higher exposure compared to males) were the main predictors of ADR occurrence. Conclusions: Our findings suggest that NAT2 could be partially responsible for the minor proportion of pregabalin metabolism, but the effect of NAT2 phenotype does not seem clinically relevant. Therefore, pharmacogenetic biomarkers appear to play a restrained role in pregabalin pharmacotherapy.

Innovation in cancer pharmacotherapy through integrative consideration of germline and tumor genomes

Precision cancer medicine is widely established, and numerous molecularly targeted drugs for various tumor entities are approved or are in development. Personalized pharmacotherapy in oncology has so far been based primarily on tumor characteristics, for example, somatic mutations. However, the response to drug treatment also depends on pharmacological processes summarized under the term ADME (absorption, distribution, metabolism, and excretion). Variations in ADME genes have been the subject of intensive research for >5 decades, considering individual patients' genetic makeup, referred to as pharmacogenomics (PGx). The combined impact of a patient's tumor and germline genome is only partially understood and often not adequately considered in cancer therapy. This may be attributed, in part, to the lack of methods for combined analysis of both data layers. Optimized personalized cancer therapies should, therefore, aim to integrate molecular information, which derives from both the tumor and the germline genome, and taking into account existing PGx guidelines for drug therapy. Moreover, such strategies should provide the opportunity to consider genetic variants of previously unknown functional significance. Bioinformatic analysis methods and corresponding algorithms for data interpretation need to be developed to integrate PGx data in cancer therapy with a special meaning for interdisciplinary molecular tumor boards, in which cancer patients are discussed to provide evidence-based recommendations for clinical management based on individual tumor profiles. SIGNIFICANCE STATEMENT: The era of personalized oncology has seen the emergence of drugs tailored to genetic variants associated with cancer biology. However, the full potential of targeted therapy remains untapped owing to the predominant focus on acquired tumor-specific alterations. Optimized cancer care must integrate tumor and patient genomes, guided by pharmacogenomic principles. An essential prerequisite for realizing truly personalized drug treatment of cancer patients is the development of bioinformatic tools for comprehensive analysis of all data layers generated in modern precision oncology programs.

Value of Pharmacogenetic Testing Assessed with Real-World Drug Utilization and Genotype Data

Implementation of pharmacogenetic testing in clinical care has been slow and with few exceptions is hindered by the lack of real-world evidence on how to best target testing. In this retrospective register-based study, we analyzed a nationwide cohort of 1,425,000 patients discharged from internal medicine or surgical wards and a cohort of 2,178 university hospital patients for purchases and prescriptions of pharmacogenetically actionable drugs. Pharmacogenetic variants were obtained from whole genome genotype data for a subset (n = 930) of the university hospital patients. We investigated factors associated with receiving pharmacogenetically actionable drugs and developed a literature-based cost-benefit model for pre-emptive pharmacogenetic panel testing. In a 2-year follow-up, 60.4% of the patients in the nationwide cohort purchased at least one pharmacogenetically actionable drug, most commonly ibuprofen (25.0%) and codeine (19.4%). Of the genotyped subset, 98.8% carried at least one actionable pharmacogenetic genotype and 23.3% had at least one actionable gene-drug pair. Patients suffering from musculoskeletal or cardiovascular diseases were more prone to receive pharmacogenetically actionable drugs during inpatient episode. The cost-benefit model included frequently dispensed drugs in the university hospital cohort, comprising ondansetron (19.4%), simvastatin (7.4%), clopidogrel (5.0%), warfarin (5.1%), (es)citalopram (5.3%), and azathioprine (0.5%). For untargeted pre-emptive pharmacogenetic testing of all university hospital patients, the model indicated saving €17.49 in direct healthcare system costs per patient in 2 years without accounting for the cost of the test itself. Therefore, it might be reasonable to target pre-emptive pharmacogenetic testing to patient groups most likely to receive pharmacogenetically actionable drugs.

Pharmacogenetics: Opportunities for the All of Us Research Program and Other Large Data Sets to Advance the Field

Pharmacogenetic variation is common and an established driver of response for many drugs. There has been tremendous progress in pharmacogenetics knowledge over the last 30 years and in clinical implementation of that knowledge over the last 15 years. But there have also been many examples where translation has stalled because of the lack of available data sets for discovery or validation research. The recent availability of data from very large cohorts with linked genetic, electronic health record, and other data promises new opportunities to advance pharmacogenetics research. This review presents the stages from pharmacogenetics discovery to widespread clinical adoption using prominent gene-drug pairs that have been implemented into clinical practice as examples. We discuss the opportunities that the All of Us Research Program and other large biorepositories with genomic and linked electronic health record data present in advancing and accelerating the translation of pharmacogenetics into clinical practice.

The relationship between CYP2C9 gene polymorphisms and azilsartan metabolism in vitro

BACKGROUND

The gene polymorphisms of the CYP2C9, as well as the substrate specificity of the enzyme, result in different clearances for different substrates by CYP2C9 variants.

RESEARCH DESIGNAND METHODS

The CYP2C9 wild type and 38 CYP2C9 variants, expressed in insectmicrosomes, were incubated with azilsartan. The resulting metabolite,O-desethyl azilsartan, was determined by HPLC-MS/MS. The enzyme kineticparameters of the 38 variants were calculated and compared with the wild type.Subsequently, we selected CYP2C9*1, *2, and  *3 as target proteins for molecular docking with azilsartan to elucidate the mechanisms underlying changes in enzyme function.

RESULTS

Compared with CYP2C9*1, three variants (CYP2C9*29, *39, and *49) exhibited markedlyincreased CLint values (from 170%-275%, *p < 0.05), whereas 28 variants exhibited significantly decreased CLint values (from 3-63%,*p < 0.05). The molecular docking results showed that the binding energy of CYP2C9*2 and *3 was lower than that of the wild type.

CONCLUSION

Thisassessment revealed the effect of CYP2C9 gene polymorphisms on azilsartan metabolism, establishing a theoretical basis for further in-vivo studies and clinical applications. This study will help expand the database of CYP2C9 gene-drug pairs and identify appropriate treatment strategies for azilsartan, contributing to the field of precision medicine.

Effect of Genetic Variants on Rosuvastatin Pharmacokinetics in Healthy Volunteers: Involvement of ABCG2, SLCO1B1 and NAT2

Statins are the primary drugs used to prevent cardiovascular disease by inhibiting the HMG-CoA reductase, an enzyme crucial for the synthesis of LDL cholesterol in the liver. A significant number of patients experience adverse drug reactions (ADRs), particularly musculoskeletal problems, which can affect adherence to treatment. Recent clinical guidelines, such as those from the Clinical Pharmacogenetics Implementation Consortium (CPIC) in 2022, recommend adjusting rosuvastatin doses based on genetic variations in the ABCG2 and SLCO1B1 genes to minimize ADRs and improve treatment efficacy. Despite these adjustments, some patients still experience ADRs. So, we performed a candidate gene study to better understand the pharmacogenetics of rosuvastatin. This study included 119 healthy volunteers who participated in three bioequivalence trials of rosuvastatin alone or in combination with ezetimibe at the Clinical Trials Unit of the Hospital Universitario de La Princesa (UECHUP). Participants were genotyped using a custom OpenArray from ThermoFisher that assessed 124 variants in 38 genes associated with drug metabolism and transport. No significant differences were observed according to sex or biogeographic origin. A significant increase in t1/2 (pmultivariate(pmv) = 0.013) was observed in the rosuvastatin plus ezetimibe trial compared with the rosuvastatin alone trials. Genetic analysis showed that decreased (DF) and poor function (PF) volunteers for the ABCG2 transporter had higher AUC∞/DW (adjusted dose/weight), AUC72h/DW and Cmax/DW compared to normal function (NF) volunteers (pmv< 0.001). DF and PF volunteers for SLCO1B1 showed an increase in AUC72h/DW (pmv = 0.020) compared to increased (IF) and NF individuals. Results for ABCG2 and SLCO1B1 were consistent with the existing literature. In addition, AUC∞/DW, AUC72h/DW and Cmax/DW were increased in intermediate (IA) and poor (PA) NAT2 acetylators (pmv = 0.001, pmv< 0.001, pmv< 0.001, respectively) compared to rapid acetylators (RA), which could be associated through a secondary pathway that was previously unknown.

Application of rapid genotyping of Warfarin individualized pharmacogenetic variants in Warfarin therapy

Warfarin is the most widely used oral anticoagulant in clinical practice. The cytochrome P450 2C9 (CYP2C9), vitamin K epoxide reductase complex 1 (VKORC1), and cytochrome P450 4F2 (CYP4F2) genotypes are associated with warfarin dose requirements in China. Accurate genotyping is vital for obtaining reliable genotype-guided warfarin dosing information. The current method for individualized dosing gene polymorphism detection for warfarin has the disadvantages of being easily contaminated, time-consuming, expensive, and unsuitable for clinical use. Herein, we present a novel application, a multiplex fluorescent melting curve assay of whole-blood direct amplification of nested polymerase chain reaction (PCR), to genotyping single-nucleotide polymorphism (SNPs) rapidly that affect warfarin efficacy. This method requires only 1 µL of whole blood, no DNA extraction, takes less than 2 h, costs less than $1, and is able to accurately distinguish between different SNP sites. Polymorphic loci were detected in whole blood specimens of 181 clinical warfarin-administered patients through nested blood direct PCR fluorescence melting curve analysis and gene sequencing. The results of the nested blood direct PCR multiplex fluorescence melting curve technology were 100% consistent with those of sequencing-characterized by high accuracy and high specificity. The allele frequencies were 94.5% for A and 5.5% for C at CYP2C9*3 (rs1057910), 7.5% for G and 92.5% for A at VKORC1 (rs9923231), and 77.1% for G and 22.9% for A at CYP4F2*3 (rs2108622). For CYP2C9*2 (rs1799853), only allele C was detected, with a frequency of 100%. Warfarin doses were lower in the CYP2C9*1*1 genotype population than in the CYP2C9*1*3 population, lower in the VKORC1 (AA) population than in the VKORC1 (GG) population, and higher in individuals with the CYP4F2*3 mutation (GA/AA) compared with those with wild-type (GG). In summary, the detection and genotyping of four polymorphic SNP sites using a multiplex fluorescent melting curve assay of whole blood direct amplification through nested PCR is highly importance for guiding personalized warfarin anticoagulant therapy.

Pharmacogenomic profiling of the South Korean population: Insights and implications for personalized medicine

Adverse drug reactions (ADRs) pose substantial public health issues, necessitating population-specific characterization due to variations in pharmacogenes. This study delineates the pharmacogenomic (PGx) landscape of the South Korean (SKR) population, focusing on 21 core pharmacogenes. Whole genome sequencing (WGS) was conducted on 396 individuals, including 99 healthy volunteers, 95 patients with chronic diseases, 81 with colon cancer, 81 with breast cancer, and 40 with gastric cancer, to identify genotype-specific drug dosing recommendations. Our detailed analysis, utilizing high-throughput genotyping (HTG) of CYP2D6 and comparative data from the 1,000 Genomes Project (1 KG) and the US National Marrow Donor Program (NMDP), revealed significant pharmacogenetic diversity in core pharmacogenes such as CYP2B6, CYP2C19, CYP4F2, NUDT15, and CYP2D6. Notably, intermediate metabolizer frequencies for CYP2B6 in SKR (3.28%) were comparable to Europeans (5.77%) and East Asians (5.36%) but significantly differed from other global populations (p < 0.01). For CYP2C19, 48.74% of SKR individuals were classified as intermediate metabolizers, with the *35 allele (2.02%) being unique to SKR, the allele not observed in other East Asian populations. Additionally, the high-risk *3 allele in CYP4F2 was significantly more frequent in SKR (34.72%) than in other East Asian populations (p < 0.01). NUDT15 poor metabolizers were found in 0.76% of SKR, aligning closely with other East Asians (1.59%), while TPMT poor metabolizers were predominantly observed in Europeans and Africans, with one case in SKR. We identified significant allele frequency differences in CYP2D6 variants rs1065852 and rs1135840. Among the 72 drugs analyzed, 93.43% (n = 370) of patients required dosage adjustments for at least one drug, with an average of 4.5 drugs per patient. Moreover, 31.31% (n = 124) required adjustments for more than five drugs. These findings reveal the substantial pharmacogenetic diversity of the SKR population within the global population, emphasizing the urgency of integrating population-specific PGx data into clinical practice to ensure safe and effective drug therapies. This comprehensive PGx profiling in SKR not only advances personalized medicine but also holds the potential to significantly improve healthcare outcomes on a broader scale.

Status of the implementation of pharmacogenetics in clinical practice in Spain: from regional to national initiatives

INTRODUCTION

Pharmacogenetics (PGx) has the potential to improve patient care, allowing to transform medical interventions by providing personalized therapeutic strategies. Scientific evidence supports the use of PGx in clinical practice and international organizations are developing clinical guidelines to facilitate the utilization of PGx testing. However, clinical implementation of PGx is limited and unequal worldwide.

CONTENT

This review summarizes regional and national Spanish initiatives to implement PGx in the clinical practice.

SUMMARY AND OUTLOOK

Diverse strategies to implement PGx in healthcare are applied across countries or even in the different regions of a specific country. Such was the case of Spain, a European country with 17 Autonomous Regions and two Autonomous Cities, each one with capacity to manage their own healthcare systems. Nevertheless, during the past years, many initiatives and strategies have been launched in Spain to develop different aspects of PGx. Importantly, the National Healthcare System has approved a PGx testing catalogue. This review highlights the crucial work and efforts of scientific societies (like the Spanish Society of Pharmacogenetics and Pharmacogenomics), of experts in PGx, of healthcare providers and of governmental parties in the implementation of PGx to personalize patient therapy, focused in Spain.

Pharmacogenomics Concierge Service as an Opportunity for Pharmacist Reimbursement and Practice-based Learning

OBJECTIVE

To assess the feasibility of a pilot pharmacogenomics concierge service that incorporates student practice-based learning opportunities and a survey to determine the patients' interest and willingness to pay.

METHODS

Participants in the pilot study (n = 34) completed a survey to determine their willingness to pay for concierge services. Six participants indicating the highest level of interest were selected to participate in the program free of charge. Students conducted preliminary genetic testing to assess the potential value of a pharmacogenomics service. For the subset of participants (n = 6) invited to the concierge service, confirmatory genetic testing was completed by a third-party laboratory. A layered learning model allowed senior students to mentor and train junior students in the area of pharmacogenomics.

RESULTS

Six invited participants completed the concierge program and third-party pharmacogenomic testing, and the majority (83%) received pharmacogenomic consultation with the pharmacist. Completed surveys from participants in the pilot program (n = 34) indicated a willingness to pay $25 to $50 per month to have continued access to a pharmacist. Surveyed individuals rated their likelihood of utilizing the concierge service at a mean rating of 8.6 (SD 1.88) on a scale of 1 to 10, although this rating dropped significantly when insurance did not cover the cost. The pilot program offered opportunities for practice-based learning through a layered learning model.

CONCLUSION

This pilot concierge program presented several successes and challenges which may help others avoid common pitfalls and spur discussion on optimal ways to develop new pharmacy services and experiential opportunities for students.

Pharmacogenomics in Sri Lanka: a comprehensive systematic review of the research landscape and clinical implications

Aim: Pharmacogenomics is emerging in South Asia, including Sri Lanka, with potential to optimize drug therapy and reduce adverse effects. This review evaluates the state of pharmacogenomics research in Sri Lanka, emphasizing population-specific factors to guide future advancements.Materials & methods: A literature search was performed across PubMed/Web-of-Science/SciVerse-Scopus/Embase, and Sri Lanka Journals Online, along with searches for relevant theses in local health repositories/university databases. Studies were categorized into clinical correlational, descriptive or novel assay development studies.Results: Eleven published articles and eight theses were included. One study examined somatic variants (KRAS gene), while all others focused on germline variants. There were two clinical correlational studies: tamoxifen adverse effects and CYP2D6 variants and FTO gene rs9939609 variants and weight gain caused by second-generation antipsychotics. Eight descriptive studies evaluated prevalence of CYP2D6 variants, HLA-B*15:02 allele, KRAS gene mutations and variants related to statin, warfarin and anticancer drug metabolism. Additionally, nine studies developed, validated and tested novel assays for detecting key pharmacogenomically important variants.Conclusion: While pharmacogenomics research in Sri Lanka has made strides, more clinical studies and broader genomic research are needed. Overcoming challenges related to funding, public awareness and regional collaboration is essential to advance personalized medicine and improve therapeutic outcomes in Sri Lanka and South Asia.

Afro-Latin American Pharmacogenetics of CYP2D6, CYP2C9, and CYP2C19 in Dominicans: A Study from the RIBEF-CEIBA Consortium

Background/Objectives: Research on pharmacogenetic variability in response to prescribed drugs and across ethnic groups is essential for personalized medicine, particularly in admixed and unstudied populations. For the first time, this study examines CYP2D6, CYP2C9, and CYP2C19 alleles and genotypes in 197 healthy volunteers from the Dominican Republic, as part of the RIBEF-CEIBA collaborative network. Methods: The analysis focuses on the participants' tri-hybrid genomic ancestry, with CYP alleles determined by real-time PCR and molecular ancestry inferred using 90 AIMs. Linear regression was used to associate ancestry components with CYP frequencies. Results: The average ancestry was 23.8% European, 42.6% Native American, and 33.6% African, the latter being higher than in most Latin American populations. Native American ancestry was also higher than expected. Predicted phenotype frequencies based on genotypes were 4.2% poor metabolizers (gPMs) and 3.6% ultrarapid metabolizers (gUMs) for CYP2D6, as well as 3% gPMs, 22.8% rapid metabolizers (gRMs), and 1.5% gUMs for CYP2C19. No gPM individuals were observed for CYP2C9. Certain alleles associated with decreased CYP2D6 activity (*17 and *29) and increased CYP2C19 activity (*17 and gUMs) were positively linked with African ancestry and negatively with Native American ancestry. Rare CYP2C9 alleles (*5 and *6) with clinical relevance were additionally found. Conclusions: These findings build on previous results from the RIBEF-CEIBA collaborative network, demonstrating differences in allele frequencies of CYP2D6, CYP2C9, and CYP2C19 in relation to genomic ancestry. In summary, ethnicity must be considered in the development of pharmacogenetic guidelines for clinical application, research, and regulation to avoid widening the biotechnology gap and to allow Personalized Medicine to reach the entire world population.

Drug-gene interactions in older patients with coronary artery disease

BACKGROUND

Older patients with coronary artery disease (CAD) are particularly vulnerable to the efficacy and adverse drug reactions, and may therefore particularly benefit from personalized medication. Drug-gene interactions (DGIs) occur when an individual's genotype affects the pharmacokinetics and/or pharmacodynamics of a victim drug.

OBJECTIVES

This study aimed to investigate the impact of cardiovascular-related DGIs on the clinical efficacy and safety outcomes in older patients with CAD.

METHODS

Hospitalized older patients (≥ 65 years old) with CAD were consecutively recruited from August 2018 to May 2022. Eligible patients were genotyped for the actionable pharmacogenetic variants of CYP2C9, CYP2C19, CYP2D6, CYP3A5, and SLCO1B1, which had clinical annotations or implementation guidelines for cardiovascular drugs. Allele frequencies and DGIs were determined in the cohort for the 5 actionable PGx genes and the prescribed cardiovascular drugs. All patients were followed up for at least 1 year. The influence of DGIs on the cardiovascular drug-related efficacy outcomes (all-cause mortality and/or major cardiovascular events, MACEs) and drug response phenotypes of "drug-stop" and "dose-decrease" were evaluated.

RESULTS

A total of 1,017 eligible older patients with CAD were included, among whom 63.2% were male, with an average age of 80.8 years old, and 87.6% were administrated with polypharmacy (≥ 5 medications). After genotyping, we found that 96.0% of the older patients with CAD patients had at least one allele of the 5 pharmacogenes associated with a therapeutic change, indicating a need for a therapeutic change in a mean of 1.32 drugs of the 19 cardiovascular-related drugs. We also identified that 79.5% of the patients had at least one DGI (range 0-6). The median follow-up interval was 39 months. Independent of age, negative association could be found between the number of DGIs and all-cause mortality (adjusted HR: 0.84, 95% CI: 0.73-0.96, P = 0.008), and MACEs (adjusted HR: 0.84, 95% CI: 0.72-0.98, P = 0.023), but positive association could be found between the number of DGIs and drug response phenotypes (adjusted OR: 1.24, 95% CI: 1.05-1.45, P = 0.011) in the elderly patients with CAD.

CONCLUSIONS

The association between cardiovascular DGIs and the clinical outcomes emphasized the necessity for the integration of genetic and clinical data to enhance the optimization of cardiovascular polypharmacy in older patients with CAD. The causal relationship between DGIs and the clinical outcomes should be established in the large scale prospectively designed cohort study.

One Step Ahead in Realizing Pharmacogenetics in Low- and Middle-Income Countries: What Should We Do?

Pharmacogenetics is a promising approach in future personalized medicine. This field holds excellent prospects for healthcare quality acceleration. It promotes the transition to the precision medicine era, whereby a health treatment is driven by a deeper understanding of individual characteristics by interpreting the underlying genomic variation. Pharmacogenetics has been developing rapidly since the human genome project. Many pharmacogenetics studies have shown the association between genetic variants and therapy outcomes. Several pharmacogenetics working groups have recommended guidelines for the clinical application of pharmacogenetics. However, the development of pharmacogenetics in low- and middle-income countries (LMICs) is still retarded behind. The problems mainly include clinical evidence, technology, policy and regulation, and human resources. Currently, available genome and drug effect data in LMICs are scarce. Pharmacogenetics development should be escalated with evidence proof through research collaboration across countries. The challenges of pharmacogenetics implementation are discussed comprehensively in this article, along with the prospect of pharmacogenetics-guided personalized medicine in developed countries. Stepwise is expected to help the researchers and stakeholders define the problem that hindered the pharmacogenetics application.

[Pharmaceutical Indication Service in a case of palmar-plantar erythema after amoxicillin and ibuprofen treatment]

Case description

Patient (29 years old) with palmo-plantar erythema, goes to the community pharmacy (FC) requesting a cream to treat atopy.

Evaluation

The patient accessed the Pharmaceutical Indication Service (SPIF), showing that the manifestations appeared 24 hours after the start of dental treatment with amoxicillin 1g/12h and ibuprofen 600 mg/8h without any concomitant medication.

Intervention

After explaining the possible relationship of the symptoms with their medication, patient was derived to the doctor with the referral report completed by SEFAC-eXPERT.

Results

The patient went to the emergency where she was treated with intravenous corticosteroid and a prescription for cetirizine 10 mg. The dentist changed the beta-lactam to a macrolide (azithromycin) and the ibuprofen to paracetamol. From the FC, the evolution of the symptoms was monitored, which took 72 hours to disappear. Allergy tests suggested avoiding beta-lactams, cephalosporins, and arylpropionics without being conclusive. Months later, the patient suffered similar symptoms after inhaling a disinfectant spray and the allergy diagnosis was confirmed.

Conclusions

The FC identified and immediately referred using SPIF a case of hypersensitivity in a patient susceptible to RNM and the SPIF helps to record the intervention and follow-up, increasing patient safety.

[Selection of pharmacogenomic variants and methodology for their use in community pharmacy]

Regulatory agencies such as the Food and Drug Administration (FDA) and the European Medicines Agency (EMA) recognize pharmacogenetics as a key tool in their pharmacological guidelines for pharmaceutical counseling. In this context, community pharmacies play a crucial role in addressing this healthcare need, which could lead to a significant improvement in patients' quality of life by preventing ineffective or contraindicated treatments.In this work, we conducted a systematic review of the available scientific evidence regarding druggene interactions relevant to community pharmacy. We identified the main genes and polymorphisms associated with treatment response and adverse effects in primary care. Finally, we propose a model for implementing pharmacogenetic services in community pharmacies.

Pharmacogenomics revolutionizing cardiovascular therapeutics: A narrative review

Background and Aim

Among the cardiovascular diseases (CVDs), heart failure, hypertension, and myocardial infarction are associated with the greatest number of disability-adjusted life years due to lifestyle changes and the failure of therapeutic approaches, especially the one-size-fits-all interventions. As a result, there has been advances in defining genetic variants responsible for different responses to cardiovascular drugs such as antiplatelets, anticoagulants, statins, and beta-blockers, which has led to their usage in guiding treatment plans. This study comprehensively reviews the current state-of-the-art potential of pharmacogenomics in dramatically altering CVD treatment. It stresses the applicability of pharmacogenomic technology, the threats associated with its adoption in the clinical setting, and proffers relevant solutions.

Methods

Literature search strategies were used to retrieve articles from various databases: PubMed, Google Scholar, and EBSCOhost. Articles with information relevant to pharmacogenomics, DNA variants, cardiovascular diseases, sequencing techniques, and drug responses were reviewed and analyzed.

Results

DNA-based technologies such as next generation sequencing, whole genome sequencing, whole exome sequencing, and targeted segment sequencing can identify variants in the human genome. This has played a substantial role in identifying different genetic variants governing the poor response and adverse effects associated with cardiovascular drugs. Thus, this has reduced patients' number of emergency visits and hospitalization.

Conclusion

Despite the emergence of pharmacogenomics, its implementation has been threatened by factors including patient compliance and a low adoption rate by clinicians. Education and training programs targeting both healthcare professionals and patients should be established to increase the acceptance and application of the emerging pharmacogenomic technologies in reducing the burden of CVDs.

PharmVar GeneFocus: CYP4F2

The Pharmacogene Variation Consortium (PharmVar) serves as a global repository providing star (*) allele nomenclature for the polymorphic human CYP4F2 gene. CYP4F2 genetic variation impacts the metabolism of vitamin K, which is associated with warfarin dose requirements, and the metabolism of drugs, such as imatinib or fingolimod, and certain endogenous compounds including vitamin E and eicosanoids. This GeneFocus provides a comprehensive overview and summary of CYP4F2 genetic variation including the characterization of 14 novel star alleles, CYP4F2*4 through *17. A description of how haplotype information cataloged by PharmVar is utilized by the Pharmacogenomics Knowledgebase (PharmGKB) and the Clinical Pharmacogenetics Implementation Consortium (CPIC) is also provided.

Mapping the Pharmacogenetic Landscape in a Ugandan Population: Implications for Personalized Medicine in an Underrepresented Population

Africans are extremely underrepresented in global genomic research. African populations face high burdens of communicable and non-communicable diseases and experience widespread polypharmacy. As population-specific genetic studies are crucial to understanding unique genetic profiles and optimizing treatments to reduce medication-related complications in this diverse population, the present study aims to characterize the pharmacogenomics profile of a rural Ugandan population. We analyzed low-pass whole genome sequencing data from 1998 Ugandans to investigate 18 clinically actionable pharmacogenes in this population. We utilized PyPGx to identify star alleles (haplotype patterns) and compared allele frequencies across populations using the Pharmacogenomics Knowledgebase PharmGKB. Clinical interpretations of the identified alleles were conducted following established dosing guidelines. Over 99% of participants displayed actionable phenotypes across the 18 pharmacogenes, averaging 3.5 actionable genotypes per individual. Several variant alleles known to affect drug metabolism (i.e., CYP3A5*1, CYP2B6*9, CYP3A5*6, CYP2D6*17, CYP2D6*29, and TMPT*3C)-which are generally more prevalent in African individuals-were notably enriched in the Ugandan cohort, beyond reported frequencies in other African peoples. More than half of the cohort exhibited a predicted impaired drug response associated with CFTR, IFNL3, CYP2B6, and CYP2C19, and approximately 31% predicted altered CYP2D6 metabolism. Potentially impaired CYP2C9, SLCO1B1, TPMT, and DPYD metabolic phenotypes were also enriched in Ugandans compared with other African populations. Ugandans exhibit distinct allele profiles that could impact drug efficacy and safety. Our findings have important implications for pharmacogenomics in Uganda, particularly with respect to the treatment of prevalent communicable and non-communicable diseases, and they emphasize the potential of pharmacogenomics-guided therapies to optimize healthcare outcomes and precision medicine in Uganda.

Assessing the Performance of In silico Tools and Molecular Dynamics Simulations for Predicting Pharmacogenetic Variant Impact

The ability of freely available in silico tools to predict the effect of non-synonymous single nucleotide polymorphisms (nsSNPs) in pharmacogenes on protein function is not well defined. We assessed the performance of seven sequence-based (SIFT, PolyPhen2, mutation accessor, FATHMM, PhD-SNP, MutPred2, and SNPs & Go) and five structure-based (mCSM, SDM, DDGun, CupSat, and MAESTROweb) tools in predicting the impact of 118 nsSNPs in the CYP2C19, CYP2C9, CYP2B6, CYP2D6, and DPYD genes with known function (24 normal, one increased, 42 decreased, and 51 no-function). Sequence-based tools had a higher median (IQR) positive predictive value (89% [89-94%] vs. 12% [10-15%], P < 0.001) and lower negative predictive value (30% [24-34%] vs. 90% [80-93%], P < 0.001) than structure-based tools. Accuracy did not significantly differ between sequence-based (59% [37-67%]) and structure-based (34% [23-44%]) tools (P = 0.070). Notably, the no-function CYP2C9*3 allele and decreased function CYP2C9*8 allele were predicted incorrectly as tolerated by 100% of sequenced-based tools and as stabilizing by 60% and 20% of structure-based tools, respectively. As a case study, we performed mutational analysis for the CYP2C9*1, *3 (I359L), and *8 (R150H) proteins through molecular dynamic (MD) simulations using S-warfarin as the substrate. The I359L variant increased the distance of the major metabolic site of S-warfarin to the oxy-ferryl center of CYP2C9, and I359L and R150H caused shifts in the conformation of S-warfarin to a position less favorable for metabolism. These data suggest that MD simulations may better capture the impact of nsSNPs in pharmacogenes than other tools.

An Investigational Study on the Role of CYP2D6, CYP3A4 and UGTs Genetic Variation on Fesoterodine Pharmacokinetics in Young Healthy Volunteers

Introduction: Fesoterodine is one of the most widely used antimuscarinic drugs to treat an overactive bladder. Fesoterodine is extensively hydrolyzed by esterases to 5-hydroxymethyl tolterodine (5-HMT), the major active metabolite. CYP2D6 and CYP3A4 mainly metabolize 5-HMT and are, therefore, the primary pharmacogenetic candidate biomarkers. Materials and Methods: This is a candidate gene study designed to investigate the effects of 120 polymorphisms in 33 genes (including the CYP, COMT, UGT, NAT2, and CES enzymes, ABC and SLC transporters, and 5-HT receptors) on fesoterodine pharmacokinetics and their safety in 39 healthy volunteers from three bioequivalence trials. Results: An association between 5-HMT exposure (dose/weight corrected area under the curve (AUC/DW) and dose/weight corrected maximum plasma concentration (Cmax/DW)), elimination (terminal half-life (T1/2) and the total drug clearance adjusted for bioavailability (Cl/F)), and CYP2D6 activity was observed. Poor/intermediate metabolizers (PMs/IMs) had higher 5-HMT AUC/DW (1.5-fold) and Cmax/DW (1.4-fold) values than the normal metabolizers (NMs); in addition, the normal metabolizers (NMs) had higher 5-HMT AUC/DW (1.7-fold) and Cmax/DW (1.3-fold) values than the ultrarapid metabolizers (UMs). Lower 5-HMT exposure and higher T1/2 were observed for the CYP3A4 IMs compared to the NMs, contrary to our expectations. Conclusions: CYP2D6 might have a more important role than CYP3A4 in fesoterodine pharmacokinetics, and its phenotype might be a better predictor of variation in its pharmacokinetics. An association was observed between different genetic variants of different genes of the UGT family and AUC, Cmax, and CL/F of 5-HMT, which should be confirmed in other studies.

Effect of Vascular Senescence on the Efficacy and Safety of Warfarin: Insights from Rat Models and a Prospective Cohort Study

Warfarin, with its narrow therapeutic range, requires the understanding of various influencing factors for personalized medication. Vascular senescence, marked by vascular stiffening and endothelial dysfunction, has an unclear effect on the efficacy and safety of warfarin. Based on previous studies, we hypothesized that vascular senescence increases the risk of bleeding during warfarin therapy. This study aimed to explore these effects using animal models and clinical cohorts. We established rat models of vascular senescence and calcification using d-galactose, vitamin D, and nicotine. After validating the models, we examined changes in the international normalized ratio (INR) at fixed warfarin doses (0.20 and 0.35 mg/kg). We found that vascular senescence caused significantly elevated INR values and increased bleeding risk. In the prospective clinical cohort study (NCT06428110), hospitalized warfarin patients with standard dose adjustments were divided into vascular senescence and control groups based on ultrasound and computed tomography diagnosis. Using propensity score matching to exclude the influence of confounding factors, we found that the vascular senescence group had lower steady-state warfarin doses and larger dose adjustments, with a higher probability of INR exceeding the therapeutic range. The vascular senescence group tended to experience more bleeding or thromboembolic/ischemic events during 1 year of follow-up, while there was no statistical difference. In conclusion, vascular senescence leads to unstable INR values and increases higher bleeding risk during warfarin therapy, highlighting the importance of considering vascular senescence in future precision warfarin therapies. SIGNIFICANCE STATEMENT: Many factors influence warfarin efficacy; however, the effect of vascular senescence remains unclear. This study aimed to investigate the effects of vascular senescence on the efficacy and safety of warfarin. Through both rat models and clinical cohort studies, our findings indicated that vascular senescence may compromise the stability of warfarin, presenting challenges in maintaining its efficacy and safety.

The need to diversify genomic studies: Insights from Andean highlanders and Amazonians

More globally diverse perspectives are needed in genomic studies and precision medicine practices on non-Europeans. Here, we illustrate this by discussing the distribution of clinically actionable genetic variants involved in drug response in Andean highlanders and Amazonians, considering their environment, history, genetic structure, and historical biases in the perception of biological diversity of Native Americans.

Leveraging QSP Models for MIPD: A Case Study for Warfarin/INR

Warfarin dosing remains challenging due to substantial inter-individual variability, which can lead to unsafe or ineffective therapy with standard dosing. Model-informed precision dosing (MIPD) can help individualize warfarin dosing, requiring the selection of a suitable model. For models developed from clinical data, the dependence on the study design and population raises questions about generalizability. Quantitative system pharmacology (QSP) models promise better extrapolation abilities; however, their complexity and lack of validation on clinical data raise questions about applicability in MIPD. We have previously derived a mechanistic warfarin/international normalized ratio (INR) model from a blood coagulation QSP model. In this article, we evaluated the predictive performance of the warfarin/INR model in the context of MIPD using an external dataset with INR data from patients starting warfarin treatment. We assessed the accuracy and precision of model predictions, benchmarked against an empirically based reference model. Additionally, we evaluated covariate contributions and assessed the predictive performance separately in the more challenging outpatient data. The warfarin/INR model performed comparably to the reference model across various measures despite not being calibrated with warfarin initiation data. Including CYP2C9 and/or VKORC1 genotypes as covariates improved the prediction quality of the warfarin/INR model, even after assimilating 4 days of INR data. The outpatient INR exhibited higher unexplained variability, and predictions slightly exceeded observed values, suggesting that model adjustments might be necessary when transitioning from an inpatient to an outpatient setting. Overall, this research underscores the potential of QSP-derived models for MIPD, offering a complementary approach to empirical model development.

Patterns of pharmacogenetic variation in nine biogeographic groups

Frequencies of pharmacogenetic (PGx) variants are known to differ substantially across populations but much of the available PGx literature focuses on one or a few population groups, often defined in nonstandardized ways, or on a specific gene or variant. Guidelines produced by the Clinical Pharmacogenetic Implementation Consortium (CPIC) provide consistent methods of literature extraction, curation, and reporting, including comprehensive curation of allele frequency data across nine defined "biogeographic groups" from the PGx literature. We extracted data from 23 CPIC guidelines encompassing 19 genes to compare the sizes of the populations from each group and allele frequencies of altered function alleles across groups. The European group was the largest in the curated literature for 16 of the 19 genes, while the American and Oceanian groups were the smallest. Nearly 200 alleles were detected in nonreference groups that were not reported in the largest (reference) group. The genes CYP2B6 and CYP2C9 were more likely to have higher frequencies of altered function alleles in nonreference groups compared to the reference group, while the genes CYP4F2, DPYD, SLCO1B1, and UGT1A1 were less likely to have higher frequencies in nonreference groups. PGx allele frequencies and function differ substantially across nine biogeographic groups, all but two of which are underrepresented in available PGx data. Awareness of these differences and increased efforts to characterize the breadth of global PGx variation are needed to ensure that implementation of PGx-guided drug selection does not further widen existing health disparities among populations currently underrepresented in PGx data.

Insights into pharmacogenetics, drug-gene interactions, and drug-drug-gene interactions

This review explores genetic contributors to drug interactions, known as drug-gene and drug-drug-gene interactions (DGI and DDGI, respectively). This article is part of a mini-review issue led by the International Society for the Study of Xenobiotics (ISSX) New Investigators Group. Pharmacogenetics (PGx) is the study of the impact of genetic variation on pharmacokinetics (PK), pharmacodynamics (PD), and adverse drug reactions. Genetic variation in pharmacogenes, including drug metabolizing enzymes and drug transporters, is common and can increase the risk of adverse drug events or contribute to reduced efficacy. In this review, we summarize clinically actionable genetic variants, and touch on methodologies such as genotyping patient DNA to identify genetic variation in targeted genes, and deep mutational scanning as a high-throughput in vitro approach to study the impact of genetic variation on protein function and/or expression in vitro. We highlight the utility of physiologically based pharmacokinetic (PBPK) models to integrate genetic and chemical inhibitor and inducer data for more accurate human PK simulations. Additionally, we analyze the limitations of historical ethnic descriptors in pharmacogenomics research. Altogether, the work herein underscores the importance of identifying and understanding complex DGI and DDGIs with the intention to provide better treatment outcomes for patients. We also highlight current barriers to wide-scale implementation of PGx-guided dosing as standard or care in clinical settings.

Implementation of pharmacogenomics: Where are we now?

Pharmacogenomics (PGx), examining the effect of genetic variation on interpatient variation in drug disposition and response, has been widely studied for several decades. However, as cost, as well as turnaround time associated with PGx testing, has significantly improved, the use of PGx in the clinical setting has been gaining momentum. Nevertheless, challenges have emerged in the broader clinical implementation of PGx. In this review, we will outline current models of PGx delivery and methodologies of evaluation, and discuss clinically relevant PGx tests and associated medications. Additionally, we will describe our approach for the broad implementation of pre-emptive DPYD genotyping in patients taking fluoropyrimidines in Ontario, Canada, as an example of clinically actionable PGx testing with sufficient clinical evidence of patient benefit that can become a new standard of patient care. We will highlight challenges associated with PGx testing, including a lack of diversity in PGx studies as well as general limitations that impact the broad adoption of PGx testing. Lastly, we examine the future of PGx, discussing new clinical targets, methodologies and analysis approaches.

Therapeutic drug monitoring of osimertinib in EGFR mutant non-small cell lung cancer by dried blood spot and plasma collection: A pilot study

AIMS

Therapeutic drug monitoring (TDM) has led to significant improvements in individualized medical care, although its implementation in oncology has been limited to date. Tyrosine kinase inhibitors (TKIs) are a group of therapies for which TDM has been suggested. Osimertinib is one such therapy used in the treatment of epidermal growth factor receptor (EGFR) mutation-driven lung cancer. Herein, we describe a prospective pilot study involving 21 patients on osimertinib primarily as a preliminary evaluation of drug levels in a real-world setting.

METHODS

Concentrations of the drug and its primary metabolites were measured with a validated liquid chromatography-mass spectrometry (LC-MS) assay across serial timepoints. As part of this study, inter-individual variability by dose and ethnicity as well as intra-individual variability across timepoints are explored. Furthermore, we attempted to validate dried blood spot (DBS)-based quantitation as an accurate alternative to plasma quantitation.

RESULTS

Successful quantitation of osimertinib and primary metabolites was achieved for our subjects. Compound plasma levels were highly correlated to DBS levels. There was no significant difference in concentrations with ethnicity or dosing or intra-individual variability across timepoints.

CONCLUSIONS

As such, we demonstrate that TDM for osimertinib is practical for future trials. We also validated the use of DBS as an alternative to conventional quantitation for exploration of TDM for osimertinib in larger trials and for other targeted therapies.

Implementation of a pharmacogenetic panel-based test for pharmacotherapy-based supportive care in an adult oncology clinic

The University of Florida Health conducted a pragmatic implementation of a pharmacogenetics (PGx) panel-based test to guide medications used for supportive care prescribed to patients undergoing chemotherapy. The implementation was in the context of a pragmatic clinical trial for patients with non-hematologic cancers being treated with chemotherapy. Patients were randomized to either the intervention arm or control arm and received PGx testing immediately or at the end of the study, respectively. Patients completed the MD Anderson Symptom Inventory (MDASI) to assess quality of life (QoL). A total of 150 patients received PGx testing and enrolled in the study. Clinical decision support and implementation infrastructure were developed. While the study was originally planned for 500 patients, we were underpowered in our sample of 150 patients to test differences in the patient-reported MDASI scores. We did observed a high completion rate (92%) of the questionnaires; however, there were few medication changes (n = 6 in the intervention arm) based on PGx test results. Despite this, we learned several lessons through this pragmatic implementation of a PGx panel-based test in an outpatient oncology setting. Most notably, patients were less willing to undergo PGx testing if the cost of the test exceeded $100. In addition, to enhance PGx implementation success, reoccurring provider education is necessary, clinical decision support needs to appear in a more conducive way to fit in with oncologists' workflow, and PGx test results need to be available earlier in treatment planning.

Construction of warfarin population pharmacokinetics and pharmacodynamics model in Han population based on Bayesian method

The purpose of this paper is to study the genetic polymorphisms of related gene loci (CYP2C9*3, VKORC1-1639G > A) based on demographic and clinical factors, and use the maximum a posterior Bayesian method to construct a warfarin individualized dose prediction model in line with the Chinese Han population. Finally, the built model is compared and analyzed with the widely used models at home and abroad. In this study, a total of 5467 INR measurements are collected from 646 eligible subjects in our hospital, and the maximum a posterior Bayesian method is used to construct a warfarin dose prediction that conforms to the Chinese Han population on the basis of the Hamberg model. The model is verified and compared with foreign models. This study finds that body weight and concomitant use of amiodarone have a significant effect on the anticoagulant effect of warfarin. The model can provide an effective basis for individualized and rational dosing of warfarin in Han population more accurately. In the performance of comparison with different warfarin dose prediction models, the new model has the highest prediction accuracy, and the prediction percentage is as high as 72.56%. The dose predicted by the Huang model is the closest to the actual dose of warfarin. The population pharmacokinetics and pharmacodynamics model established in this study can better reflect the distribution characteristics of INR values after warfarin administration in the Han population, and performs better than the models reported in the literature.

Pharmacogenetic guided versus standard warfarin dosing for routine clinical care with its pharmacoeconomic impact: a randomized controlled clinical trial

BACKGROUND

Empirical use of pharmacogenetic test(PGT) is advocated for many drugs, and resource-rich setting hospitals are using the same commonly. The clinical translation of pharmacogenetic tests in terms of cost and clinical utility is yet to be examined in hospitals of low middle income countries (LMICs).

AIM

The present study assessed the clinical utility of PGT by comparing the pharmacogenetically(PGT) guided- versus standard of care(SOC)- warfarin therapy, including the health economics of the two warfarin therapies.

METHODS

An open-label, randomized, controlled clinical trial recruited warfarin-receiving patients in pharmacogenetically(PGT) guided- versus standard of care(SOC)- study arms. Pharmacogenetic analysis of CYP2C9*2(rs1799853), CYP2C9*3(rs1057910) and VKORC1(rs9923231) was performed for patients recruited to the PGT-guided arm. PT(Prothrombin Time)-INR(international normalized ratio) testing and dose titrations were allowed as per routine clinical practice. The primary endpoint was the percent time spent in the therapeutic INR range(TTR) during the 90-day observation period. Secondary endpoints were time to reach therapeutic INR(TRT), the proportion of adverse events, and economic comparison between two modes of therapy in a Markov model built for the commonest warfarin indication- atrial fibrillation.

RESULTS

The study enrolled 168 patients, 84 in each arm. Per-protocol analysis showed a significantly high median time spent in therapeutic INR in the genotype-guided arm(42.85%; CI 21.4-66.75) as compared to the SOC arm(8.8%; CI 0-27.2)(p < 0.00001). The TRT was less in the PG-guided warfarin dosing group than the standard-of-care dosing warfarin group (17.85 vs. 33.92 days) (p = 0.002). Bleeding and thromboembolic events were similar in the two study groups. Lifetime expenditure was ₹1,26,830 in the PGT arm compared to ₹1,17,907 in the SOC arm. The QALY gain did not differ in the two groups(3.9 vs. 3.65). Compared to SOC, the incremental cost-utility ratio was ₹35,962 per QALY gain with PGT test opting. In deterministic and probabilistic sensitivity analysis, the base case results were found to be insensitive to the variation in model parameters. In the cost-effectiveness-acceptability curve analysis, a 90% probability of cost-effectiveness was reached at a willingness-to-pay(WTP) of ₹ 71,630 well below one time GDP threshold of WTP used.

CONCLUSION

Clinical efficacy and the cost-effectiveness of the warfarin pharmacogenetic test suggest its routine use as a point of care investigation for patient care in LMICs.

Clinical versus fixed warfarin dosing and the impact on quality of anticoagulation (The ClinFix trial)

Different dosing strategies exist to initiate warfarin, most commonly fixed warfarin dosing (FWD), clinical warfarin dosing (CWD), and genetic-guided warfarin dosing (GWD). Landmark trials have shown GWD to be superior when compared to FWD in the EU-PACT trial or CWD in the GIFT trial. COAG trial did not show differences between GWD and CWD. We aim to compare the anticoagulation quality outcomes of CWD and FWD. This is a prospective cohort study with a retrospective comparator. Recruited subjects in the CWD (prospective) arm were initiated on warfarin according to the clinical dosing component of the algorithm published in www.warfarindosing.org. The primary efficacy outcome was the percentage time in the therapeutic range (PTTR) from day 3 to 6 till day 28 to 35. The study enrolled 122 and 123 patients in the CWD and FWD, respectively. The PTTR did not differ statistically between CWD and FWD (62.2 ± 26.2% vs. 58 ± 25.4%, p = 0.2). There was also no difference between both arms in the percentage of visits with extreme subtherapeutic international normalized ratio (INR) (<1.5; 15 ± 18.3% vs. 16.8 ± 19.1%, p = 0.44) or extreme supratherapeutic INR (>4; 7.7 ± 14.7% vs. 7.5 ± 12.4%, p = 0.92). We conclude that CWD did not improve the anticoagulation quality parameters compared to the FWD method.

QPGx-CARES: Qatar pharmacogenetics clinical applications and research enhancement strategies

Pharmacogenetic (PGx)-informed medication prescription is a cutting-edge genomic application in contemporary medicine, offering the potential to overcome the conventional "trial-and-error" approach in drug prescription. The ability to use an individual's genetic profile to predict drug responses allows for personalized drug and dosage selection, thereby enhancing the safety and efficacy of treatments. However, despite significant scientific and clinical advancements in PGx, its integration into routine healthcare practices remains limited. To address this gap, the Qatar Genome Program (QGP) has embarked on an ambitious initiative known as QPGx-CARES (Qatar Pharmacogenetics Clinical Applications and Research Enhancement Strategies), which aims to set a roadmap for optimizing PGx research and clinical implementation on a national scale. The goal of QPGx-CARES initiative is to integrate PGx testing into clinical settings with the aim of improving patient health outcomes. In 2022, QGP initiated several implementation projects in various clinical settings. These projects aimed to evaluate the clinical utility of PGx testing, gather valuable insights into the effective dissemination of PGx data to healthcare professionals and patients, and identify the gaps and the challenges for wider adoption. QPGx-CARES strategy aimed to integrate evidence-based PGx findings into clinical practice, focusing on implementing PGx testing for cardiovascular medications, supported by robust scientific evidence. The current initiative sets a precedent for the nationwide implementation of precision medicine across diverse clinical domains.

Ancestry, ethnicity, and race: explaining inequalities in cardiometabolic disease

Population differences in cardiometabolic disease remain unexplained. Misleading assumptions over genetic explanations are partly due to terminology used to distinguish populations, specifically ancestry, race, and ethnicity. These terms differentially implicate environmental and biological causal pathways, which should inform their use. Genetic variation alone accounts for a limited fraction of population differences in cardiometabolic disease. Research effort should focus on societally driven, lifelong environmental determinants of population differences in disease. Rather than pursuing population stratifiers to personalize medicine, we advocate removing socioeconomic barriers to receipt of and adherence to healthcare interventions, which will have markedly greater impact on improving cardiometabolic outcomes. This requires multidisciplinary collaboration and public and policymaker engagement to address inequalities driven by society rather than biology per se.

Decoding Pharmacogenomic Test Interpretation and Application to Patient Care

Pharmacogenomics is a growing area of medicine, and pharmacists across clinical practice settings have the opportunity to individualize medication selection and dosing using genetic data. However, many practicing pharmacists may feel ill-equipped to interpret pharmacogenomic test results because of insufficient education and training. Evidence-based, updated, and freely available resources such as the Clinical Pharmacogenetics Implementation Consortium guidelines can help pharmacists interpret and apply pharmacogenomic test results to patient care. Although gaps for the application of pharmacogenomic information exist, this commentary aims to demystify the interpretation of pharmacogenomic test results and empower pharmacists to apply genetic data alongside other clinical variables to optimize medication-related outcomes for their patients. An "ABCD" framework is proposed to guide pharmacists through the steps: (1) Actionability - Are the gene(s) clinically relevant for the patient? (2) Be Mindful of Limitations - What are the caveats with pharmacogenomic test results and reports? (3) Clinical Practice Guidelines - How do you use pharmacogenomic test results to guide clinical decision-making? and (4) Document and Discuss - How do you educate the patient about their pharmacogenomic test results and document the results for future use? Key concepts are illustrated using a psychiatric patient case example.

Genetic polymorphisms and major bleeding risk during vitamin K antagonists treatment: The BLEEDS case-cohort

BACKGROUND

Major bleeding occurs annually in 1%-3% of patients on vitamin K antagonists (VKAs), despite close monitoring. Genetic variants in proteins involved in VKA response may affect this risk.

AIM

To determine the association of genetic variants (cytochrome P450 enzymes 2C9 [CYP2C9] and 4F2 [CYP4F2], gamma-glutamyl carboxylase [GGCX]) with major bleeding in VKA users, separately and combined, including vitamin K epoxide reductase complex subunit-1 (VKORC1).

METHODS

A case-cohort study was established within the BLEEDS cohort, which includes 16,570 patients who initiated VKAs between 2012 and 2014. We selected all 326 major bleeding cases that occurred during 17,613 years of follow-up and a random subcohort of 978 patients. We determined variants in CYP2C9, CYP4F2, GGCX, VKORC1 and evaluated the interaction between variant genotypes. Hazard ratios for major bleeding with 95% confidence intervals (95% CI) were estimated by weighted Cox regression.

RESULTS

Genotype was determined in 256 cases and 783 subcohort members. Phenprocoumon was the most prescribed VKA for both cases and the subcohort (78% and 75%, respectively). Patients with major bleeding were slightly older than subcohort patients. CYP4F2-TT carriership was associated with a 1.6-fold (95% CI 0.9-2.8) increased risk of major bleeding compared with CC-alleles, albeit not statistically significant. For the CYP2C9 and GGCX variants instead, the major bleeding risk was around unity. Carrying at least two variant genotypes in CYP2C9 (poor metabolizer), CYP4F2-TT, and VKORC1-AA was associated with a 4.0-fold (95%CI 1.4-11.4) increased risk, while carriers of both CYP4F2-TT and VKORC1-AA had a particularly increased major bleeding risk (hazard ratio 6.7, 95% CI 1.5-29.8) compared with carriers of CC alleles in CYP4F2 and GG in VKORC1. However, the number of major bleeding cases in carriers of multiple variants was few (8 and 5 patients, respectively).

CONCLUSIONS

CYP4F2 polymorphism was associated with major bleeding, especially in combination with VKORC1 genetic variants. These variants could be considered to further personalize anticoagulant treatment.

Development of a comprehensive cardiovascular disease genetic risk assessment test

Background

Despite monogenic and polygenic contributions to cardiovascular disease (CVD), genetic testing is not widely adopted, and current tests are limited by the breadth of surveyed conditions and interpretation burden.

Methods

We developed a comprehensive clinical genome CVD test with semi-automated interpretation. Monogenic conditions and risk alleles were selected based on the strength of disease association and evidence for increased disease risk, respectively. Non-CVD secondary findings genes, pharmacogenomic (PGx) variants and CVD polygenic risk scores (PRS) were assessed for inclusion. Test performance was modeled using 2,594 genomes from the 1000 Genomes Project, and further investigated in 20 previously tested individuals.

Results

The CVD genome test is composed of a panel of 215 CVD gene-disease pairs, 35 non-CVD secondary findings genes, 4 risk alleles or genotypes, 10 PGx genes and a PRS for coronary artery disease. Modeling of test performance using samples from the 1000 Genomes Project revealed ~6% of individuals with a monogenic finding in a CVD-associated gene, 6% with a risk allele finding, ~1% with a non-CVD secondary finding, and 93% with CVD-associated PGx variants. Assessment of blinded clinical samples showed complete concordance with prior testing. An average of 4 variants were reviewed per case, with interpretation and reporting time ranging from 9-96 min.

Conclusions

A genome sequencing based CVD genetic risk assessment can provide comprehensive genetic disease and genetic risk information to patients with CVD. The semi-automated and limited interpretation burden suggest that this testing approach could be scaled to support population-level initiatives.

The landscape of very important pharmacogenes variants and potential clinical relevance in the Chinese Jingpo population: a comparative study with worldwide populations

BACKGROUND

Pharmacogenomics is a facet of personalized medicine that explores how genetic variants affect drug metabolism and adverse drug reactions. Therefore, this study aims to detect distinct pharmacogenomic variations among the Jingpo population and explore their clinical correlation with drug metabolism and toxicity.

METHODS

Agena MassARRAY Assay was used to genotype 57 VIP variants in 28 genes from 159 unrelated Jingpo participants. Subsequently, the chi-squared test and Bonferroni's statistical tests were utilized to conduct a comparative analysis of genotypes and allele frequencies between the Jingpo population and the other 26 populations from the 1000 Genome Project.

RESULTS

We discovered that the KHV (Kinh in Ho ChiMinh City, Vietnam), CHS (Southern Han Chi-nese, China) and JPT (Japanese in Tokyo, Japan) exhibited the smallest differences from the Jingpo with only 4 variants, while ESN (Esan in Nigeria) exhibited the largest differences with 30 variants. Besides, a total of six considerably different loci (rs4291 in ACE, rs20417 in PTGS2, rs1801280 and rs1799929 in NAT2, rs2115819 in ALOX5, rs1065852 in CYP2D6, p < 3.37 × 10-5) were identified in this study. According to PharmGKB, rs20417 (PTGS2), rs4291 (ACE), rs2115819 (ALOX5) and rs1065852 (CYP2D6) were found to be associated with the metabolism efficiency of non-steroidal anti-inflammatory drugs (NSAIDs), aspirin, montelukast and tamoxifen, respectively. Meanwhile, rs1801280 and rs1799929 (NAT2) were found to be related to drug poisoning with slow acetylation.

CONCLUSION

Our study unveils distinct pharmacogenomic variants in the Jingpo population and discovers their association with the metabolic efficiency of NSAIDs, montelukast, and tamoxifen.

Ascorbic acid-induced warfarin resistance after breast cancer surgery: a case report and literature review

Warfarin is an anticoagulant that requires INR-based dosage adjustment. Ascorbic acid may impair warfarin effectiveness according to limited literature. We report a rare case of a 63-year-old woman with an aortic valve replacement history who developed warfarin resistance after taking ascorbic acid for anemia following breast cancer surgery. Despite increasing the warfarin dose from 6 mg to 10 mg daily, her INR remained below the therapeutic range. After ruling out other causes of warfarin resistance, we discontinued ascorbic acid and observed a rapid increase in INR to target values. The temporal relationship and the absence of other confounding factors confirmed the causality of ascorbic acid in this case. We recommend that patients concomitantly taking vitamin C and warfarin should monitor their INR values closely and discontinue ascorbic acid as soon as possible if they exhibit signs of warfarin resistance.

Correlation between Metabolic Parameters and Warfarin Dose in Patients with Heart Valve Replacement of Different Genotypes

Background

Warfarin has become the first choice for anticoagulation in patients who need lifelong anticoagulation due to its clinical efficacy and low price. However, the anticoagulant effect of warfarin is affected by many drugs, foods, etc. accompanied by a high risk of bleeding and embolism. The Vitamin K epoxide reductase complex 1 (VKORC1) and Cytochrome P450 2C9 (CYP2C9) genotypic variation can influence the therapeutic dose of warfarin. However, it is not clear whether there is a correlation between warfarin dose and liver function, kidney function and metabolic markers such as uric acid (UA) in patients with different genotypes. We performed a single-center retrospective cohort study to evaluate the factors affecting warfarin dose and to establish a dose conversion model for warfarin patients undergoing heart valve replacement.

Methods

We studied 343 patients with a mechanical heart valve replacement, compared the doses of warfarin in patients with different warfarin-related genotypes (CYP2C9 and VKORC1), and analyzed the correlation between liver function, kidney function, UA and other metabolic markers and warfarin dose in patients with different genotypes following heart valve replacement.

Results

Genotype analysis showed that 72.01% of patients had CYP2C9*1/*1 and VKORC1 mutant AA genotypes. Univariate regression analysis revealed that the warfarin maintenance dose was significantly correlated with gender, age, body surface area (BSA), UA and genotype. There was no correlation with liver or kidney function. Multiple linear regression analysis showed that BSA, genotype and UA were the independent factors influencing warfarin dose.

Conclusions

There is a significant correlation between UA content and warfarin dose in patients with heart valve replacement genotypes CYP2C9*1/*1/VKORC1(GA+GG), CYP2C9*1/*1/VKORC1AA and CYP2C9*1/*1/VKORC1AA.

Pharmacogenetic considerations in therapy with novel antiplatelet and anticoagulant agents

Antiplatelets and anticoagulants are extensively used in cardiovascular medicine for the prevention and treatment of thrombosis in the venous and arterial circulations. Wide inter-individual variability has been observed in response to antiplatelets and anticoagulants, which triggered researchers to investigate the genetic basis of this variability. Data from extensive pharmacogenetic studies pointed to strong evidence of association between polymorphisms in candidate genes and the pharmacokinetics and pharmacodynamic action and clinical response of the antiplatelets clopidogrel and the anticoagulant warfarin. In this review, we conducted an extensive search on Medline for the time period of 2009-2023. We also searched the PharmGKB website for levels of evidence of variant-drug combinations and for drug labels and clinical guidelines. We focus on the pharmacogenetics of novel antiplatelets and anticoagulants while excluding acetylsalicylic acid, warfarin and heparins, and discuss the current knowledge with emphasis on the level of evidence.

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.