Background: A specific antidote namely andexanet alfa (AA) is approved for the management of bleeding complications with apixaban and rivaroxaban. The dosing regimen of andexanet alfa ranges from 400 – 800 mg bolus followed by 4 – 8 mg/min for up to two hours. This dosing regimen is projected to result in a circulating concentration of 75 – 150 ug/ml.
Aims: This study is designed to compare the neutralization efficacy of andexanet alfa for various factor Xa inhibitors in clot-based and anti-Xa assays.
Methods: Stock solutions of each of the agents were prepared at 1mg/ml and working concentrations at 100 and 10 ug/ml. Each of the factor Xa inhibitor was supplemented in plasma in the concentration range of 0 – 1 ug/ml. The neutralization profile of AA was studied at 100ug/ml and 200ug/ml and saline was used as a control. The IC50 for the Xa inhibitory activity were calculated for the control drugs and after supplementation with AA.
Results: Apixaban and edoxaban exhibited similar inhibitory profiles in the anti-Xa assays, where as rivaroxaban and betrixaban exhibited much higher IC50s. AA effectively neutralized the anticoagulant effects of all agents at both the 100 and 200 ug/ml, however the neutralization profile in the clot based was not proportional to the anti-Xa effects. At 200ug/ml only betrixaban was completely neutralized whereas all the other agents were partially neutralized. The order of neutralization at 200ug/ml was betrixaban > rivaroxaban > apixaban > edoxaban.
Conclusions: These studies show that the neutralization profiles of various Xa agents by AA exhibit differential characteristic response for each of the individual agent. These results indicate that individual dosing based on clinical endpoints for each agent rather than the neutralization of anti-Xa activity measurement may be more relevant to the clinical outcome.
To cite this abstract in AMA style:Siddiqui F, Tafur A, Hoppensteadt D, Bontekoe E, Jeske W, Lewis B, Iqbal O, Fareed J. Differences in the Clot Based and Amidolytic Anti-Xa Assays for the Neutralization Profile of Apixaban, Betrixaban, Edoxaban and Rivaroxaban [abstract]. Res Pract Thromb Haemost. 2021; 5 (Suppl 1). https://abstracts.isth.org/abstract/differences-in-the-clot-based-and-amidolytic-anti-xa-assays-for-the-neutralization-profile-of-apixaban-betrixaban-edoxaban-and-rivaroxaban/. Accessed September 23, 2021.
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ISTH Congress Abstracts - https://abstracts.isth.org/abstract/differences-in-the-clot-based-and-amidolytic-anti-xa-assays-for-the-neutralization-profile-of-apixaban-betrixaban-edoxaban-and-rivaroxaban/