Identification of VKORC1 genotype leading to resistance to tecarfarin.

Abstract

International audienceThe VKORC1 gene codes for the VKORC1 enzyme that is responsible for the reduction of vitamin K epoxide into vitamin K. VKORC1 enzyme is the target of vitamin K antagonists (VKA). The use of VKA in human medicine is difficult because of inter-individual variability in VKA requirements. This variability is partly due to basic physiological parameters but also to genetic polymorphisms in CYP2C9 involved in VKA metabolism. Tecarfarin, a new VKA, was developed to avoid the CYP2C9-dependent metabolism. This molecule is metabolized by carboxylesterases. Nevertheless, genetic variations in the VKORC1 gene are also associated with inter-individual variability in VKA requirements. This study was performed to estimate the benefit of using tecarfarin versus traditional VKA in human patient carrier for hVKORC1 mutation. Wild type hVKORC1 and its spontaneous mutants were expressed in Pichia pastoris and susceptibility to tecarfarin was assessed by the in vitro determination of inhibition constants. Among the 14 mutated VKORC1 proteins analyzed in this study, 6 mutations (i.e., A26P, A41S, V54L, H68Y, I123N, and Y139H) led to resistant to traditional VKAs, while only 4 mutations (i.e., A26P, V54L, I123N, and Y139H) led to resistant to tecarfarin. Compared to other VKAs, a clear benefit of tecarfarin is observed for the mutants A26P, A41S, H68Y, and I123N and an absence of benefit for the mutant Y139H. Finally, tecarfarin is particularly inefficient on V54L-VKORC1