Coagulation assays for assessing the bypassing of factor Xa direct oral anticoagulants using VMX-C001

Factor (F)Xa direct oral anticoagulants (DOACs) require rapid reversal in patients with serious bleeding or needing urgent surgery/interventions. VMX-C001 is a recombinant human FX variant under development as an FXa DOAC bypassing agent.

This study aimed to develop and evaluate the sensitivity of 2 modified commercially available coagulation assays-dilute prothrombin time (dPT) and dilute Russell viper venom time (dRVVT)-to assess coagulation with FXa DOACs with/without VMX-C001.

Citrated platelet-poor plasma samples were obtained from healthy volunteers. Assay evaluation was performed using undiluted and 2.5× diluted plasma for dPT and 3× and 4× diluted plasma for dRVVT in the absence and presence of apixaban (100 or 250 ng/mL) and/or VMX-C001 (30 μg/mL). Additionally, dPT/dRVVT were measured in plasma spiked in vitro with apixaban, edoxaban, or rivaroxaban (0-1600 ng/mL) in the absence and presence of VMX-C001 (15-60 μg/mL), andexanet (50-200 μg/mL), or 4-factor prothrombin complex concentrates (0.25-0.50 IU/mL). In vivo assay evaluation used plasma samples from healthy subjects administered apixaban or rivaroxaban and from nursing home residents receiving FXa DOAC treatment.

Both modified dPT and dRVVT assays were highly sensitive to FXa DOACs, showing dose-dependent prolongation of clotting time, which was fully restored when VMX-C001 or andexanet (higher concentrations) was present in the plasma. Using both assays, clotting time from healthy subjects and nursing home residents receiving FXa DOACs correlated strongly with plasma drug concentrations.

dPT and dRVVT assays can serve as surrogate end points in studies of VMX-C001 and can also be used to monitor FXa DOAC anticoagulation.