Antidotal Effects of Non-Specific Reversal Agents On Anticoagulant-Induced Inhibition of Thrombin Generation.
Authors: Pillitteri Daniele , Pilgrimm-Thorp Ann-Kathrin , Krause Manuela , Scholz Thomas , Schwerdtfeger Rainer , Behrendt Tanja , Kirchmaier Carl 
Published: October 2019

Abstract
Abstract 2273

Introduction
Reversal of pharmacologic anticoagulation is an issue that arises when an anticoagulated patient has a major bleeding or when an emergency surgery needs immediate correction of coagulation. However, the new oral anticoagulants (NOAC) Rivaroxaban (anti-FXa) and Dabigatran (anti-FIIa) lack specific antidotes and only limited data is available regarding the antidotal effect of non-specific haemostatic agents. Therefore, in this ex vivo study reversal of anticoagulant activity after the administration of either 20mg Rivaroxaban or 150mg Dabigatran was tested in vitro using two different PCC (Beriplex®, Cofact®), aPCC (FEIBA®; factor eight inhibitor bypassing activity) or rFVIIa (NovoSeven®) at various concentrations.

Patients and Method

Subjects
10 healthy caucasian subjects (female: n=5; male: n=5) were first randomized to receive either 20 mg Rivaroxaban or 150 mg Dabigatran in one oral dose. The patients had to abide a 7-day wash-out period before administration of the respective second drug.

Methods
Citrated venous blood was taken right before (T0) and 2 hours after administration (T2) of either Dabigatran or Rivaroxaban. The potential of 4 commercially available haemostatic agents to reverse the anticoagulant effect of the NOACs was evaluated.
• Beriplex: 0.25; 0.5 (corresp. to 25 U/kg); 1; 2 U/mL
• Cofact: 0.25; 0.5 (corresp. to 25 U/kg); 1; 2 U/mL
• FEIBA:0.25; 0.5; 1 (corresp. to 80 U/kg); 2 U/mL
• NovoSeven: 1.25; 2.5; 5; 10 μg/mL (a dose of 90–100 μg/kg corresponds to a plasma level of about 2 μg/mL)
Thrombin generation using Calibration Automated Thrombinography (CAT) was the primarily applied assay, along with the parameters aPTT, PT, thrombin time, Rivaroxaban- and Dabigatran levels and Ecarin time. Parameters of interest concerning the thrombin generation assay (TGA) were the endogenous thrombin potential (ETP), Peak (maximum reaction velocity) and Lag time (LT; length of the latent phase). Thrombin generation in platelet poor plasma was initiated by adding 1 pM tissue factor and 4 μM phospholipids.

Results
2 hours after administration (T2), Rivaroxaban showed remarkable inhibitory effects on the investigated TGA parameters ETP, Peak and Lag time, with a more pronounced inhibitory effect on the Peak. In contrast, Dabigatran at T2 only showed a slight effect on ETP and no effect on the Peak whereas LT was significantly prolonged (fourfold).
Rivaroxaban-induced inhibition of ETP and Peak were reversed by FEIBA in a concentration dependent manner with an over-correction for the two highest concentrations (1 and 2 U/mL). Cofact and rFVIIa restored ETP dose-dependently and both reached baseline T0 at their highest concentrations. Compared to FEIBA, rFVIIa and Cofact only had a slight but dose-dependent effect on the Peak. Interestingly, the other PCC, Beriplex, did not show any reversal effects on ETP and Peak.
Regarding Rivaroxaban-prolonged LT all concentrations of rFVIIa and FEIBA were responsible for a significant LT-reduction close to baseline, whereas both PCCs did not correct prolonged LT.
Regarding Dabigatran, all doses of rFVIIa, Cofact and FEIBA reduced the LT, with a more pronounced and dose-dependent effect of Cofact and FEIBA. For Beriplex only a slight reduction in LT was observed.

Conclusion
FEIBA and rFVIIa showed significant reversal of anticoagulant activity already at low therapeutic concentrations for both anticoagulants in TGA. Surprisingly, regarding both investigated PCCs, only Cofact showed an antidotal effect on TGA parameters, especially in higher therapeutic concentrations (1 and 2 U/mL). Considering that the main difference between the two PCCs is that Beriplex contains small amounts of heparin and Cofact does not, it is conceivable that this may explain the observed differences in TGA. Further clinical validation is needed.

Disclosures:
No relevant conflicts of interest to declare.