We propose to develop a personalized pharmacogenetic approach including the major genetic markers of warfarin (coumadin) dosing and patients' age and weight. The known genetic determinants include several functional and common polymorphisms in CYP2C9 and VKORC1 genes, which explain the low-end of warfarin dosing range and mostly occur in patients of Caucasian and Chinese origins. We identified a new VKORC1 polymorphism that is specifically indicative of the high dose requirements and is dominant over the dose-reducing effect of the known CYP2C9 and VKORC1 markers. This marker is significantly over-represented in Jews of Ethiopian origin, but is also common in Ashkenazis, it is also linked to the VKORC1 genetic markers characteristic of the Afro-American population (published in Blood 2007, 109:2477-80). This information prompts the development of a more inclusive and universal diagnostic approach to the individualized warfarin therapy.

The present study aims at evaluation of our novel pharmacogenetic model for predicting warfarin (coumadin) dose response on the basis of patient's genetic markers of warfarin sensitivity and resistance, and other patient specific factors. To this end, we proposes to re-evaluate our previously developed pharmacogenetic model in stabilized warfarin treated patients (N=200) and then to implement it in a prospective study of patients new on warfarin as compared to the "traditionally" treated patients (N=500).