Question: Which genes are involved in patient response to warfarin?

Context:
We identified ORM1 as another polymorphic gene affecting warfarin dose requirements. ORM1 *S carriers require lower maintenance doses to achieve and maintain an optimal level of anticoagulation.
Detecting genetic polymorphism of CYP2C9 and VKORC1 could guide clinical use of warfarin to reduce the risk of adverse reactions including bleeding in patients receiving chronic anticoagulation therapy
The genes encoding for cytochrome P450 (CYP) 2C9 (CYP2C9) and vitamin K epoxide reductase complex subunit 1 (VKORC1) are the major genetic determinants of warfarin pharmacokinetics and pharmacodynamics, respectively.
Numerous studies have demonstrated significant contributions of these genes to warfarin dose requirements. The CYP2C9 gene has also been associated with bleeding risk with warfarin. The CYP4F2 gene influences vitamin K availability and makes minor contributions to warfarin dose requirements
There are other genetic polymorphisms that may further explain the response to warfarin. The VKORC1 genotype is an important determinant of response to warfarin in Chinese, but some genetic variants found in other ethnic groups that have a large effect on warfarin response and dosing are not commonly found in Chinese
the alleles rs1799853 (*2) and rs1057910 (*3) of the CYP2C9 gene, as well as rs9923231 of the VKORC1 gene were associated with warfarin dose required to achieve anticoagulation with INR of 2-3.
Polymorphisms in the genes encoding the cytochrome P450 2C9 enzyme (CYP2C9) and the vitamin K epoxide reductase (VKORC1) are known to contribute to variability in sensitivity to coumarins.
VKORC1 and CYP2C9 polymorphisms are important factors that influence warfarin dose response in Sudanese patients
he response to the anticoagulant drug warfarin is greatly affected by genetic polymorphisms in the VKORC1 and CYP2C9 genes.
The HDA-based assays demonstrated a clinically acceptable performance for genotyping the VKORC1 -1639G>A SNP and two SNPs (430C>T and 1075A>C) for the CYP2C9 enzyme (CYP2C9*2 and CYP2C9*3), all of which are relevant in warfarin pharmacogenentics.
Genetic variability in the VKORC1 and CYP2C9 genes is associated with increased warfarin sensitivity
CYP2C9 and VKORC1 polymorphisms known to affect warfarin response
genetic variants of VKORC1, CYP2C9, CYP4F2, and EPHX1 were found to be significant predictor variables for the maintenance dose of warfarin, explaining 26.6% of dose variability.
CYP2C9 was the most important gene determining initial anticoagulant control, whereas VKORC1 was more important for stable anticoagulation. Novel associations with some clinical outcomes were found with single nucleotide polymorphisms in the cytochrome 450 genes CYP2C18 and CYP2C19, which were independent of the associations observed with CYP2C9 and in genes encoding CYP3A5, protein S and clotting factor V, although the variability explained by these genes was small.
VKORC1 -1639 G>A polymorphism, body weight, age, and serum albumin were found to affect the inter-individual variabilit
the CYP2C9 and VKORC1 genes have been demonstrated to be determinants of warfarin response.
On the basis of these observations, the Food and Drug Administration (FDA) approved a labeling change for warfarin that includes the genetic information of VKORC1 and CYP2C9 as factors influencing interindividual variability in warfarin dosing. T
the two key genes of interest, the cytochrome P450 2C9 gene, CYP2C9, and the vitamin K epoxide reductase complex 1 gene, VKORC1, on warfarin response
The influence of CYP2C9 and VKORC1 genotypes on warfarin dose requirements has been consistently demonstrated in diverse racial and ethnic patient groups in observational studies and randomized clinical trials.
genetic factors influencing drug pharmacokinetics (CYP2C9) and pharmacodynamic response (VKORC1). In particular, the discovery of polymorphisms in the VKORC1 gene that strongly impact oral anticoagulant dose has heightened expectations that genetic testing
Our data suggest that CYP2C9 genotype, age and body size are important determinants of warfarin dose requirements in African-Americans. Our data further suggest that the VKORC1 G6853C polymorphism alone may not be useful for predicting warfarin dose requirements in this racial group.
A strong association was found between genetic polymorphisms in six genes, including VKORC1, CYP2C9, PROC, EPHX1, GGCX, and ORM1, and interindividual variability in the anticoagulant effect of warfarin; the strongest predictors were VKORC1 and CYP2C9.
Three of six VKORC1 SNPs were found to be very strongly associated with the average warfarin dose required to achieve the target international normalised ratio (INR; p<0.0001)
These results are of considerable clinical interest and confirm recently published results regarding the role of these two genes in modifying warfarin metabolism and maintenance dosage. The consistent findings regarding the role of VKORC1 and CYP2C9 in warfarin metabolism and maintenance dosage represent a clinically useful proof of principal for the use of pharmacogenomic information in medicine and may lead to improved understanding of warfarin's actions.
Clinical studies showed an increased plasma level of S-warfarin, decreased clearance of S-warfarin, increased frequency of bleeding, and prolongation of hospitalization in patients with variant CYP2C9 alleles.

Answer: The following genes have been associated with patient response to warfarin: CYP2C9, VKORC1, ORM1, CYP4F2, EPHX1, CYP2C18, CYP2C19, CYP3A5, protein S, clotting factor V, PROC, GGCX.
Exact answer: CYP2C9, VKORC1, ORM1, CYP4F2, EPHX1, CYP2C18, CYP2C19, CYP3A5, protein S, clotting factor V, PROC, GGCX