A multiplex assay to detect variations in the CYP2C9, VKORC1, CYP4F2 and APOE genes involved in acenocoumarol metabolism

Acenocoumarol Pharmacogenetic Dosing Algorithm versus Usual Care in Patients with Venous Thromboembolism: A Randomised Clinical Trial

Patients with venous thromboembolism (VTE) require immediate treatment with anticoagulants such as acenocoumarol. This multicentre randomised clinical trial evaluated the effectiveness of a dosing pharmacogenetic algorithm versus a standard-of-care dose adjustment at the beginning of acenocoumarol treatment. We included 144 patients with VTE. On the day of recruitment, a blood sample was obtained for genotyping (CYP2C9*2, CYP2C9*3, VKORC1, CYP4F2, APOE). Dose adjustment was performed on day 3 or 4 after the start of treatment according to the assigned group and the follow-up was at 12 weeks. The principal variable was the percentage of patients with an international normalised ratio (INR) within the therapeutic range on day 7. Thirty-four (47.2%) patients had an INR within the therapeutic range at day 7 after the start of treatment in the genotype-guided group compared with 14 (21.9%) in the control group (p = 0.0023). There were no significant differences in the time to achieve a stable INR, the number of INRs within the range in the first 6 weeks and at the end of study. Our results suggest the use of a pharmacogenetic algorithm for patients with VTE could be useful in achieving target INR control in the first days of treatment.

Clinical and genetic factors influencing acenocoumarol dosing: a cross-sectional study

: Coumadin oral anticoagulants are widely used in multiple clinical scenarios. Their narrow therapeutic range and a dosing strategy based on 'a posteriori' algorithms, pose them as an interesting group for prediction modelling research. Extensive literature explaining the association between clinical and genetic variables with the dose of warfarin have been published. Limited information exists regarding these factors and acenocoumarol dosing. The aim of the study is to explain through clinical/genetic variables, the weekly dose of acenocoumarol necessary for achieving stable anticoagulation status. We performed a cross-sectional study enrolling adults under treatment with acenocoumarol with at least three consecutive INRs between 2 and 3. To explain the association between demographic, clinical and genotype data (VKORC1, CYP2C9 and CYP4F2) and the mean weekly dose of acenocoumarol, we performed a multiple linear regression model. In our cohort, a higher age, the presence of atrial fibrillation, chronic renal failure and VKORC1 haplotype A were associated with a lower mean weekly dose of acenocoumarol. On the other side, a higher weight was associated with a higher weekly dose. Amongst anticoagulated adult patients, VKORC1 genotype and baseline clinical factors can explain acenocoumarol dosing, and therefore, help clinicians while deciding the initial anticoagulant dose.

Whole Blood PCR Amplification with Pfu DNA Polymerase and Its Application in Single-Nucleotide Polymorphism Analysis

AIMS

Point-of-care genetic analysis may require polymerase chain reaction (PCR) to be carried out on whole blood. However, human blood contains natural inhibitors of PCR such as hemoglobin, immunoglobulin G, lactoferrin, and proteases, as well as anticoagulant agents, including EDTA and heparin that can reduce whole blood PCR efficiency. Our purpose was to develop a highly specific, direct whole blood single-nucleotide polymorphism (SNP) analysis method based on allele-specific (AS) PCR that is mediated by Pfu DNA polymerase and phosphorothioate-modified AS primers.

RESULTS

At high Mg(2+) concentrations, Pfu DNA polymerase efficiently amplified genomic DNA in a reaction solution containing up to 14% whole blood. Among the three anticoagulants tested, Pfu DNA polymerase showed the highest activity with sodium citrate. Meanwhile, Triton X-100 and betaine inhibited Pfu DNA polymerase activity in whole blood PCR, whereas trehalose had virtually no effect. These findings provided for the development of a low-cost, simple, and fast direct whole blood genotyping method that uses Pfu DNA polymerase combined with phosphorothioate AS primers for CYP2C9*3 and VKORC1(-1639) loci.

CONCLUSIONS

With its high DNA amplification efficiency and tolerance of various blood conditions, Pfu DNA polymerase can be used in clinical laboratories to analyze SNPs in whole blood samples.

Efficiency and effectiveness of the use of an acenocoumarol pharmacogenetic dosing algorithm versus usual care in patients with venous thromboembolic disease initiating oral anticoagulation: study protocol for a randomized controlled trial

Background

Hemorrhagic events are frequent in patients on treatment with antivitamin-K oral anticoagulants due to their narrow therapeutic margin. Studies performed with acenocoumarol have shown the relationship between demographic, clinical and genotypic variants and the response to these drugs. Once the influence of these genetic and clinical factors on the dose of acenocoumarol needed to maintain a stable international normalized ratio (INR) has been demonstrated, new strategies need to be developed to predict the appropriate doses of this drug. Several pharmacogenetic algorithms have been developed for warfarin, but only three have been developed for acenocoumarol. After the development of a pharmacogenetic algorithm, the obvious next step is to demonstrate its effectiveness and utility by means of a randomized controlled trial. The aim of this study is to evaluate the effectiveness and efficiency of an acenocoumarol dosing algorithm developed by our group which includes demographic, clinical and pharmacogenetic variables (VKORC1, CYP2C9, CYP4F2 and ApoE) in patients with venous thromboembolism (VTE).

Methods and design

This is a multicenter, single blind, randomized controlled clinical trial. The protocol has been approved by La Paz University Hospital Research Ethics Committee and by the Spanish Drug Agency. Two hundred and forty patients with VTE in which oral anticoagulant therapy is indicated will be included. Randomization (case/control 1:1) will be stratified by center. Acenocoumarol dose in the control group will be scheduled and adjusted following common clinical practice; in the experimental arm dosing will be following an individualized algorithm developed and validated by our group. Patients will be followed for three months. The main endpoints are: 1) Percentage of patients with INR within the therapeutic range on day seven after initiation of oral anticoagulant therapy; 2) Time from the start of oral anticoagulant treatment to achievement of a stable INR within the therapeutic range; 3) Number of INR determinations within the therapeutic range in the first six weeks of treatment.

Discussion

To date, there are no clinical trials comparing pharmacogenetic acenocoumarol dosing algorithm versus routine clinical practice in VTE. Implementation of this pharmacogenetic algorithm in the clinical practice routine could reduce side effects and improve patient safety.

Trial registration

Eudra CT. Identifier: 2009-016643-18.