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.

Development and validation wise assessment of genotype guided warfarin dosing algorithm in Indian population.

OBJECTIVES: A study was conducted to develop and validate the warfarin pharmacogenetic dose optimization algorithm considering the clinical pharmacogenetic implementation consortium (CPIC) recommendations for the Asian ethnicity population. METHODS: The present prospective observational study recruited warfarin-receiving patients. We collected a three ml blood sample for VKORC1, CYP2C9*2, CYP2C9*3, and CYP4F2 polymorphism assessment during the follow-up visits. Clinical history, sociodemographic and warfarin dose details were noted. RESULTS: The study recruited 300 patients (250 in derivation and 50 in validation timed cohort) receiving warfarin therapy. The baseline characteristics were similar in both cohorts. BMI, presence of comorbidity, VKORC1, CYP2C9*2, and CYP2C9*3 were identified as covariates significantly affecting the warfarin weekly maintenance dose (p<0.001 for all) and the same were included in warfarin pharmacogenetic dose optimization algorithm building. The algorithm built-in the present study showed a good correlation with Gage (r=0.57, p<0.0001), and IWPC (r=0.51, p<0.0001) algorithms, widely accepted in western side of the globe. The receiver operating characteristic curve analysis showed a sensitivity of 73 %, a positive predictive value of 96 %, and a specificity of 89 %. The algorithm correctly identified the validation cohort's warfarin-sensitive, intermediate reacting, and resistant patient populations. CONCLUSIONS: Validation and comparisons of the warfarin pharmacogenetic dose optimization algorithm have made it ready for the clinical trial assessment.

Pharmacogenetics of warfarin and healthcare costs - Real-world data analysis.

PURPOSE: Variants in CYP2C9 and VKORC1 genes have been associated with individuals' sensitivity to warfarin. The aim of this study was to investigate the differences of healthcare costs of genetically normal and genetically sensitive warfarin responder groups. METHODS: This was a retrospective study linking genotype data from three Finnish biobanks (THL Biobank, Auria Biobank, Helsinki Biobank) with healthcare encounter data of the Finnish Institute of Health and Welfare (THL), drug dispensation data from the Social Insurance Institution of Finland (Kela) and laboratory data from Finnish hospital districts and municipalities. We compared the normal and sensitive warfarin responder groups in terms of healthcare costs related to bleeding and thromboembolic events, INR tests and medication purchases. RESULTS: We found a trend towards increased bleeding-related hospital costs in the sensitive warfarin responder group (881 patients) when compared with the normal responders (1627 patients) with a per patient difference of 150.9 €/year (95% CI: -55.1, 414.6 €/year, p = 0.087). INR test costs were higher in the sensitive responder group with a difference of 7.2 €/year (95% CI: -1.5, 16.4 €/year, p = 0.047). Medication costs were significantly lower in the sensitive responder group with a difference of -14.4 €/year (95% CI: -15.8, -12.9 €/year, p < 0.001). CONCLUSIONS: The difference in the costs of bleeding-related hospitalization between genetically sensitive and normal warfarin responders may justify genotype-guided warfarin dosing. Further studies with larger sample sizes would be needed to verify the result.

Toxicokinetic analysis of the anticoagulant rodenticides warfarin & diphacinone in Egyptian fruit bats (Rousettus aegyptiacus) as a comparative sensitivity assessment for Bonin fruit bats (Pteropus pselaphon).

Anticoagulant rodenticides have been widely used to eliminate wild rodents, which as invasive species on remote islands can disturb ecosystems. Since rodenticides can cause wildlife poisoning, it is necessary to evaluate the sensitivity of local mammals and birds to the poisons to ensure the rodenticides are used effectively. The Bonin Islands are an archipelago located 1000 km southeast of the Japanese mainland and are famous for the unique ecosystems. Here the first-generation anticoagulant rodenticide diphacinone has been used against introduced black rats (Rattus rattus). The only land mammal native to the archipelago is the Bonin fruit bat (Pteropus pselaphon), but little is known regarding its sensitivity to rodenticides. In this study, the Egyptian fruit bats (Rousettus aegyptiacus) was used as a model animal for in vivo pharmacokinetics and pharmacodynamics analysis and in vitro enzyme kinetics using their hepatic microsomal fractions. The structure of vitamin K epoxide reductase (VKORC1), the target protein of the rodenticide in the Bonin fruit bat, was predicted from its genome and its binding affinity to rodenticides was evaluated. The Egyptian fruit bats excreted diphacinone slowly and showed similar sensitivity to rats. In contrast, they excreted warfarin, another first-generation rodenticide, faster than rats and recovered from the toxic effect faster. An in silico binding study also indicated that the VKORC1 of fruit bats is relatively tolerant to warfarin, but binds strongly to diphacinone. These results suggest that even chemicals with the same mode of action display different sensitivities in different species: fruit bat species are relatively resistant to warfarin, but vulnerable to diphacinone.

Implementation of pharmacogenomic clinical decision support for health systems: a cost-utility analysis.

We constructed a cost-effectiveness model to assess the clinical and economic value of a CDS alert program that provides pharmacogenomic (PGx) testing results, compared to no alert program in acute coronary syndrome (ACS) and atrial fibrillation (AF), from a health system perspective. We defaulted that 20% of 500,000 health-system members between the ages of 55 and 65 received PGx testing for CYP2C19 (ACS-clopidogrel) and CYP2C9, CYP4F2 and VKORC1 (AF-warfarin) annually. Clinical events, costs, and quality-adjusted life years (QALYs) were calculated over 20 years with an annual discount rate of 3%. In total, 3169 alerts would be fired. The CDS alert program would help avoid 16 major clinical events and 6 deaths for ACS; and 2 clinical events and 0.9 deaths for AF. The incremental cost-effectiveness ratio was $39,477/QALY. A PGx-CDS alert program was cost-effective, under a willingness-to-pay threshold of $100,000/QALY gained, compared to no alert program.

VKORC1 mutations in rodent populations of a tropical city-state as an indicator of anticoagulant rodenticide resistance.

Anticoagulant rodenticides are commonly used in rodent control because they are economical and have great deployment versatility. However, rodents with Single Nucleotide Polymorphism (SNP) mutations within the Vkorc1 gene are resistant to the effects of anticoagulant rodenticide use and this influences the effectiveness of control strategies that rely on such rodenticides. This study examined the prevalence of rat SNP mutations in Singapore to inform the effectiveness of anticoagulant rodenticide use. A total of 130 rat tail samples, comprising 83 Rattus norvegicus (63.8%) and 47 Rattus rattus complex (36.2%) were conveniently sampled from November 2016 to December 2019 from urban settings and sequenced at exon 3 of Vkorc1. Sequencing analysis revealed 4 synonymous and 1 non-synonymous mutations in Rattus rattus complex samples. A novel synonymous mutation of L108L was identified and not previously reported in other studies. Non-synonymous SNPs were not detected in the notable codons of 120, 128 and 139 in R. norvegicus, where these regions are internationally recognised to be associated with resistance from prior studies. Our findings suggest that the prevalence of anticoagulant rodenticide resistance in Singapore is low. Continued monitoring of rodenticide resistance is important for informing rodent control strategies aimed at reducing rodent-borne disease transmission.

Comparing outcomes and costs among warfarin-sensitive patients versus warfarin-insensitive patients using The Right Drug, Right Dose, Right Time: Using genomic data to individualize treatment (RIGHT) 10K warfarin cohort.

Oral anticoagulant (OAC) therapy has been the main treatment approach for stroke prevention for decades. Warfarin is the most widely prescribed OAC in the United States, but is difficult to manage due to variability in dose requirements across individuals. Pharmacogenomics may mitigate risk concerns related to warfarin use by fostering the opportunity to facilitate individualized medicine approaches to warfarin treatment (e.g., genome-guided dosing). While various economic evaluations exist examining the cost-effectiveness of pharmacogenomics testing for warfarin, few observational studies exist to support these studies, with even fewer using genotype as the main exposure of interest. We examined a cohort of individuals initiating warfarin therapy between 2004 and 2017 and examined bleeding and cost outcomes for the year following initiation using Mayo Clinic's billing and administrative data, as well the Mayo Clinic Rochester Cost Data Warehouse. Analyses included descriptive summaries, comparison of characteristics across exposure groups, reporting of crude outcomes, and multivariate analyses. We included N = 1,143 patients for analyses. Just over a third of our study population (34.9%) carried a warfarin-sensitive phenotype. Sensitive individuals differed in their baseline characteristics by being of older age and having a higher number of comorbid conditions; myocardial infarction, diabetes, and cancer in particular. The occurrence of bleeding events was not significantly different across exposure groups. No significant differences across exposure groups existed in either the likelihood of incurring all-cause healthcare costs or in the magnitude of those costs. Warfarin-sensitive individuals were no more likely to utilize cardiovascular-related healthcare services; however, they had lower total and inpatient cardiovascular-related costs compared to warfarin-insensitive patients. No significant differences existed in any other categories of costs. We found limited evidence that warfarin-sensitive individuals have different healthcare spending than warfarin-insensitive individuals. Additional real-world studies are needed to support the traditional economic evaluations currently existing in the literature.

Cost-Effectiveness of Multigene Pharmacogenetic Testing in Patients With Acute Coronary Syndrome After Percutaneous Coronary Intervention.

OBJECTIVE: To evaluate the cost-effectiveness of multigene testing (CYP2C19, SLCO1B1, CYP2C9, VKORC1) compared with single-gene testing (CYP2C19) and standard of care (no genotyping) in acute coronary syndrome (ACS) patients undergoing percutaneous coronary intervention (PCI) from Medicare's perspective. METHODS: A hybrid decision tree/Markov model was developed to simulate patients post-PCI for ACS requiring antiplatelet therapy (CYP2C19 to guide antiplatelet selection), statin therapy (SLCO1B1 to guide statin selection), and anticoagulant therapy in those that develop atrial fibrillation (CYP2C9/VKORC1 to guide warfarin dose) over 12 months, 24 months, and lifetime. The primary outcome was cost (2016 US dollar) per quality-adjusted life years (QALYs) gained. Costs and QALYs were discounted at 3% per year. Probabilistic sensitivity analysis (PSA) varied input parameters (event probabilities, prescription costs, event costs, health-state utilities) to estimate changes in the cost per QALY gained. RESULTS: Base-case-discounted results indicated that the cost per QALY gained was $59 876, $33 512, and $3780 at 12 months, 24 months, and lifetime, respectively, for multigene testing compared with standard of care. Single-gene testing was dominated by multigene testing at all time horizons. PSA-discounted results indicated that, at the $50 000/QALY gained willingness-to-pay threshold, multigene testing had the highest probability of cost-effectiveness in the majority of simulations at 24 months (61%) and over the lifetime (81%). CONCLUSIONS: On the basis of projected simulations, multigene testing for Medicare patients post-PCI for ACS has a higher probability of being cost-effective over 24 months and the lifetime compared with single-gene testing and standard of care and could help optimize medication prescribing to improve patient outcomes.

Systematic review of the evidence on the cost-effectiveness of pharmacogenomics-guided treatment for cardiovascular diseases.

PURPOSE: To examine the evidence on the cost-effectiveness of implementing pharmacogenomics (PGx) in cardiovascular disease (CVD) care. METHODS: We conducted a systematic review using multiple databases from inception to 2018. The titles and abstracts of cost-effectiveness studies on PGx-guided treatment in CVD care were screened, and full texts were extracted. RESULTS: We screened 909 studies and included 46 to synthesize. Acute coronary syndrome and atrial fibrillation were the predominantly studied conditions (59%). Most studies (78%) examined warfarin-CYP2C9/VKORC1 or clopidogrel-CYP2C19. A payer's perspective was commonly used (39%) for cost calculations, and most studies (46%) were US-based. The majority (67%) of the studies found PGx testing to be cost-effective in CVD care, but cost-effectiveness varied across drugs and conditions. Two studies examined PGx panel testing, of which one examined pre-emptive testing strategies. CONCLUSION: We found mixed evidence on the cost-effectiveness of PGx in CVD care. Supportive evidence exists for clopidogrel-CYP2C19 and warfarin-CYP2C9/VKORC1, but evidence is limited in other drug-gene combinations. Gaps persist, including unclear explanation of perspective and cost inputs, underreporting of study design elements critical to economic evaluations, and limited examination of PGx panel and pre-emptive testing for their cost-effectiveness. This review identifies the need for further research on economic evaluations of PGx implementation.

Genetic polymorphisms of patients on stable warfarin maintenance therapy in a Ghanaian population.

BACKGROUND: Warfarin is a widely prescribed anticoagulant with narrow therapeutic window for thromboembolic events. Warfarin displays large individual variability in dose requirements. The purpose of this study is to assess the contribution of patient-specific and genetic risk factors to dose requirements of patients on either high or low warfarin maintenance dose in Ghana. Blood samples were collected from 141 (62 males, 79 females) Ghanaian patients on stable warfarin dose to determine their INR. Influence of patient specific factors and gene variations within VKORC1, CYP2C9 and CYP4F2 were determined in patients on either high or low warfarin maintenance dose. RESULTS: One hundred and forty-one patients took part in the study with 79 (56%) participants being Female. The median age of the study participants was 48 years [IQR: 34-58]. The median duration for patients to be on warfarin therapy was 24 months [IQR: 10-72]. Majority of the study participants (80.9%, n = 114) did not have any side effects to warfarin. CYP2C9*2 and CYP2C9*3 variant alleles were not detected. VKORC1 variant allele was observed at 6% and CYP4F2 variant allele was observed at 41%. Duration of patients on warfarin therapy was marginally associated with high warfarin dose (adjusted OR = 1.01 [95% CI 1.00-1.02], p = 0.033) while the odds of heterozygous individuals (G/A) for VKORC1 gene to have high warfarin dose compared to persons with homozygous (G/G) (adjusted OR = 0.06 [95% CI 0.01-0.63], p = 0.019). Age, gender, diagnosis, presence of side effects and other medications were not associated with warfarin dose (p = 0.05). CONCLUSION: This study provides data on VKORC1 and CYP4F2 variants among an indigenous African population. Duration of patients on warfarin therapy was marginally associated with high warfarin dose. CYP2C9*2 and *3 variants were not detected and may not be the most important genetic factor for warfarin maintenance dose among Ghanaians.

Cost-effectiveness of pharmacogenetic-guided dosing of warfarin in the United Kingdom and Sweden.

We aimed to assess the cost-effectiveness of pharmacogenetic-guided dosing of warfarin in patients with atrial fibrillation (AF) in the United Kingdom and Sweden. Data from EU-PACT, a randomized controlled trial in newly diagnosed AF patients, were used to model the incremental costs per quality-adjusted life-year (QALY) gained by pharmacogenetic-guided warfarin dosing versus standard treatment over a lifetime horizon. Incremental lifetime costs were £26 and 382 Swedish kronor (SEK) and incremental QALYs were 0.0039 and 0.0015 in the United Kingdom and Sweden, respectively. The corresponding incremental cost-effectiveness ratios (ICERs) were £6 702 and 253 848 SEK per QALY gained. The ICER was below the willingness-to-pay threshold of £20 000 per QALY gained in 93% of the simulations in the United Kingdom and below 500 000 SEK in 67% of the simulations in Sweden. Our data suggest that pharmacogenetic-guided dosing of warfarin is a cost-effective strategy to improve outcomes of patients with AF treated with warfarin in the United Kingdom and in Sweden.

[Comparison of Empiric and Pharmacogenetic Approaches in Assessment of Efficacy of Anticoagulant Therapy].

We compared pharmacogenetic (PG) and standard approaches to selection of individual dose of warfarin on 2 groups of patients each comprising 17 persons. In the group with PG selection we took into consideration the result of preliminary genotyping of polymorphisms of VKORC1 and CYP2C9 genes known to be associated with individual warfarin dose. Control of warfarin therapy was carried out during 6 months, number of measurements of international normalized ratio (INR) exceeded 500. Dosing based on knowledge of genotype allowed to achieve therapeutic effect 5 days earlier than with traditional selection of individual dose (p=0.023). Number of INR values above 3.5 indicative of increased risk of bleeding was lower at PG compared with standard approach (3.1 and 7.7%, respectively, p=0.03). Carriers of *2 and/or *3 of CYP2C9 associated with lowering of activity of this cytochrome had greater lability of INR values during course of therapy with warfarin.

Universal versus genotype-guided use of direct oral anticoagulants in atrial fibrillation patients: a decision analysis.

AIM: This study aims to compare clinical and economic outcomes of CYP2C9 and VKORC1 genotype-guided (PG-DOAC) versus universal use of direct oral anticoagulant (DOAC) for stroke prevention in patients with atrial fibrillation (AF). METHODS: Outcomes of oral anticoagulation therapy were simulated using life-long Markov modeling. In PG-DOAC, patients with genotype of high or low warfarin sensitivity were treated with DOAC, and patients with normal warfarin sensitivity genotype received warfarin. RESULTS: Expected quality-adjusted life-years (QALYs) and cost of DOAC were higher than PG-DOAC. Incremental cost per QALY (ICER) of DOAC versus PG-DOAC was 314,129 USD/QALY, exceeding willingness-to-pay threshold (50,000 USD/QALY). CONCLUSION: Using individual genotype to guide the use of DOAC versus warfarin appears to be the preferred strategy.

Prevalence of genetic polymorphisms of CYP2C9 and VKORC1 - implications for warfarin management and outcome in Croatian patients with acute stroke.

BACKGROUND: Data on the prevalence of CYP2C9 and VKORC1 genes and their influence on anticoagulant effect and warfarin dose in stroke patients are scarce. The aim of this study was to determine the occurrence and significance of these gene polymorphisms and to establish pharmacogenetic algorithm to estimate the dose of introduction. Also, the goal was to determine tailored safety and intensity of anticoagulation response depending on the allelic variants and their impact on the clinical outcome in acute stroke patients in Croatia. METHODS: A total of 106 consented acute stroke patients were tested for CYP2C9 2, 3 and VKORC1 1173C>T gene polymorphisms. We estimated the dose of introduction and monitored anticoagulant effect obtained by INR values, time to reach stable dose, stable maintenance dose, time spent within the therapeutic/supratherapeutic INR range, occurrence of dosage side effects and clinical outcome depending on genotypes. RESULTS: We found that 83% of stroke patients in our study were carriers of multiple allelic variants. The predicted initial dose correlated with the stable warfarin maintenance dose (p=0.0311) and we correctly estimated the dose for 81.5% of 61.3% of study patients who required higher/lower doses than average. Warfarin dosage complications were slightly more frequent among the carriers of CYP2C9 2, 3 compared to the carriers of VKORC1 1173T alleles (68. 9% versus 62.5%), but their occurrence did not affect the final clinical outcome. CONCLUSION: Our data indicated rapid and safe anticoagulation achieved by using pharmacogenetically-predicted warfarin dose in high-risk acute stroke patients without increasing the risk of warfarin dosage complications in an elderly population.

Pharmacogenetic-guided dosing of coumarin anticoagulants: algorithms for warfarin, acenocoumarol and phenprocoumon.

Coumarin derivatives, such as warfarin, acenocoumarol and phenprocoumon are frequently prescribed oral anticoagulants to treat and prevent thromboembolism. Because there is a large inter-individual and intra-individual variability in dose-response and a small therapeutic window, treatment with coumarin derivatives is challenging. Certain polymorphisms in CYP2C9 and VKORC1 are associated with lower dose requirements and a higher risk of bleeding. In this review we describe the use of different coumarin derivatives, pharmacokinetic characteristics of these drugs and differences amongst the coumarins. We also describe the current clinical challenges and the role of pharmacogenetic factors. These genetic factors are used to develop dosing algorithms and can be used to predict the right coumarin dose. The effectiveness of this new dosing strategy is currently being investigated in clinical trials.

Genetic, clinical and behavioural determinants of vitamin K-antagonist dose--explored through multivariable modelling and visualization.

Vitamin K antagonists (VKA) are highly effective anticoagulants but their use is hampered by multiple interactions with food and medicine and a narrow therapeutic range. The large variation in dose requirements has led to the development of several dosing algorithms based on pharmacogenetic and clinical variables. In contrast, evidence about the influence of behavioural (i.e. diet and exercise) and socio-psychological factors is sparse. To investigate the impact of pharmacogenetic, clinical, behavioural and socio-psychological factors on maintenance dose of VKA. In a cross-sectional study, we interviewed 250 consecutive patients from an anticoagulant clinic and subsequently measured pharmacogenetic and anthropometric variables. Statistical analyses were carried out using linear regression and multivariable models with visualization features. In both types of analyses, the strongest determinants of VKA dose were polymorphisms in the VKORC1 and CYP2C9 genes and age. Half of the variation in VKA dose could be explained by a linear regression model including four variables, while a multivariable model with 20 pharmacogenetic and clinical variables explained 60%. A multivariable model including 94 predictor variables was not notably better regarding predictive performance, but visualization of this model offered information about the correlation structure between predictor variables. The strongest determinants of VKA dose are well-known pharmacogenetic variables and age. The variables describing health-related behaviour and socio-psychological factors are strongly inter-correlated and not useful in dosing algorithms.