Impact of Factor × Mutations on the Activity of Edoxaban

Edoxaban is a direct inhibitor of factor Xa (FXa), and its efficacy as an oral anti-coagulant agent is less likely to be affected by food intake or drug-drug interaction. This profile of edoxaban suggests a good compliance in clinical use.However it is not clear whether genetic variations of FX influence the efficacy of edoxaban.

To investigate the possible inter-patient variability in the efficacy of edoxaban stemming from SNPs in the FX gene, we characterized the enzyme activity of FXa derived from wild type FX (FX-WT) and from FX with two known mutations, A152T (FX-A152T) and G192R (FX-G192R). The impact of FX mutations were also tested on the pharmacological activity of edoxaban.

Among known FX SNPs in the NCBI dbSNP database, two non-synonymous SNPs are located inside mature FX, rs3211772 (allele frequency: 0.006) and rs3211783 (allele frequency: 0.022), corresponding to A152T and G192R. The former located inside the light chain and the latter located inside the activation peptide of FX. We selected these two SNPs and examined whether they might influence on the efficacy of edoxaban. We prepared recombinant FX proteins of FX-WT, FX-A152T and FX-G192R. We measured the enzyme activities of these FXa and the anti-FXa and anticoagulant effects of edoxaban on these FXa. Recombinant FX proteins were activated with Russell's viper venom factor × activator and FXa activity was measured using a chromogenic substrate S-2222. Prothrombin time (PT) and activated partial thromboplastin time (aPTT) were measured using FX-deficient plasma supplemented with recombinant FX proteins with a coagulometer CA-50.

Km values of FX-WT, FX-A152T and FX-G192R FXa were 0.55, 0.53 and 0.54 nM, respectively, Vmax of FX-WT, FX-A152T and FX-G192R FXa were 21.0, 21.8 and 21.4 mOD/min, respectively. PTs of plasma containing these mutations were 25.2 (FX-WT), 24.2 (FX-A152T) and 24.1 (FX-G192R) seconds. aPTTs of plasma containing the mutated FXs were 76.7 (FX-WT), 77.3 (FX-A152T) and 72.6 (FX-G192R) seconds. These data indicated that these mutations do not affect the basal FXa catalytic activity and coagulation activity. The Ki values of edoxaban for the mutated Fxas, the concentrations of edoxaban required to double the PT (PTCT2) and aPTT (aPTTCT2) in plasma containing the mutated FXs did not affected by two FX mutarions (Table 1).

These data demonstrated that those mutations have no impact on the anticoagulant activity of edoxaban.

Two FX mutations, A152T and G192R, do not affect the basal FXa catalytic activity and coagulation activity. Edoxaban acts equally on FX-WT, FX-A152T and FX-G192R. It is suggested that edoxaban has little inter-patient variability stemming from SNPs in FX gene.

Noguchi:Daiichi Sankyo Co., Ltd.: Employment. Takahashi:Daiichi Sankyo Co., Ltd.: Employment. Ishihara: Daiichi Sankyo Co., Ltd.: Employment. Morishima:Daiichi Sankyo Co., Ltd.: Employment. Shibano:Daiichi Sankyo Co., Ltd.: Employment.