Reversal of the Thrombin Generation Inhibitory Effect of Apixaban, Betrixaban, Edoxaban and Rivaroxaban by Andexanet Alpha may be Associated with Increased Thrombogenesis
Authors: Siddiqui Fakiha , Tafur Alfonso , Jeske Walter , Kouta Ahmed , Hoppensteadt Debra , Ramacciotti Eduardo , Fareed Jawed 
Published: June 2021

IntroductionCoagulation factor Xa recombinant, inactivated – ZhZo also known as Andexanet Alpha (AA, Portola Pharmaceuticals) is a recombinant modified version of human activated factor Xa which is devoid of enzymatic activity and developed to neutralize factor Xa inhibitors such as Apixaban, Betrixaban, Edoxaban and Rivaroxaban. This agent acts as a decoy receptor with the same affinity as factor Xa rendering them ineffective. Although AA is not an active procoagulant its use has been reported to result in thromboembolic events. It was hypothesized that AA may enhance thrombin generation in human plasma which may contribute to the reported thrombotic complications. To validate this, the reversal effect of AA was studied in thrombin generation assays with different oral factor Xa inhibitors.MethodsCitrated plasma samples (n=10) with normal clotting profiles as measured by PT and APTT were pooled to obtain citrated pooled plasma (CPP). Individual aliquots of CPP were supplemented with either saline or AA at a final concentration of 100 ug/ml. They were also tested in plasma samples supplemented with 1 ug/ml of Apixaban, Betrixaban, Edoxaban and Rivaroxaban. Factor Xa activity was measured using an amidolytic method. Thrombin generation studies were carried out using a calibrated automated thrombogram (CAT) ‐ thrombin generation assay (Diagnostica Stago, Paris, France). Parameters as peak thrombin (PT), area under the curve (AUC) and lag time (LT) were measured. The inhibitory effects of each of these agents were calculated and the reversal by AA was also calculated.ResultsSupplementation of AA to normal plasma resulted in an increased generation of thrombin in comparison to saline control. The peak thrombin levels was higher (40%), the AUC was also increased (15%) whereas the lag time was decreased (17%). No anti Xa activity was observed in the saline supplemented system with AA. At 1 ug/ml level all of the factor Xa inhibitors produced varying levels of the inhibition of PT (>75%) and AUC (>35%) which was associated with an increase in the LT. AA at 100 ug/ml to various factor Xa supplemented systems resulted in a reversal of the inhibitory effects restoring the thrombin generation profile. Notably the thrombin generation profile was stronger in comparison to the saline supplemented plasma. In terms of the AUC the LT and PT levels were comparable to saline. The factor Xa activity reversal profile varied with the specific agents, apixaban (22%), betrixaban (56%), edoxaban (28%) and rivaroxaban (49%) decrease rate.ConclusionsThese results suggest that AA is capable reversing anti Xa activity of different anticoagulants, but also enhancing thrombogenesis in both the saline and factor Xa inhibitor supplemented systems as evident by increased generation of thrombin. The relative degree of enhancement in different Xa inhibitors supplemented systems was product specific.Support or Funding InformationNone.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.