What is Anti-Xa (Anti-Factor Xa)?

From the Guidelines

Anticoagulation therapy with anti-factor Xa inhibitors, such as rivaroxaban, apixaban, and edoxaban, is recommended for the prevention and treatment of venous thromboembolism and atrial fibrillation, with a focus on minimizing bleeding risks and ensuring therapeutic efficacy, as supported by the most recent guidelines 1.

Key Considerations

• The use of anti-factor Xa inhibitors has been extensively studied, with recent guidelines providing recommendations on their use in various clinical settings, including the prevention and treatment of venous thromboembolism and atrial fibrillation 1.
• The International Society on Thrombosis and Haemostasis recommends describing anticoagulant medications by their route of administration and specific targets, such as oral factor Xa inhibitors 1.
• The development of antidotes for anti-factor Xa inhibitors, such as andexanet alfa, is ongoing, with the goal of providing a rapid reversal option in cases of serious bleeding or urgent interventions 1.

Clinical Applications

• Anti-factor Xa inhibitors are used for the prevention and treatment of venous thromboembolism, with rivaroxaban being more effective than enoxaparin in preventing VTE after total hip or knee replacement surgery 1.
• These inhibitors are also used for the prevention of acute ischemic stroke in patients with atrial fibrillation, with apixaban, dabigatran, edoxaban, and rivaroxaban being commonly used options 1.
• The choice of anti-factor Xa inhibitor depends on various factors, including the patient's renal function, bleeding risk, and specific clinical condition being treated.

Monitoring and Reversal

• Monitoring of anti-factor Xa activity is not routinely recommended, but may be considered in certain patient populations, such as those with renal impairment or severe obesity 1.
• The development of antidotes for anti-factor Xa inhibitors is an active area of research, with andexanet alfa being a promising option for rapid reversal in cases of serious bleeding or urgent interventions 1.

From the FDA Drug Label

Apixaban is a selective inhibitor of FXa. It does not require antithrombin III for antithrombotic activity. Apixaban inhibits free and clot-bound FXa, and prothrombinase activity. The Rotachrom Heparin chromogenic assay was used to measure the effect of apixaban on FXa activity in humans during the apixaban development program. A concentration-dependent increase in anti-FXa activity was observed in the dose range tested and was similar in healthy subjects and patients with AF.

Ant Xa activity is a key aspect of apixaban's mechanism of action. Apixaban works by inhibiting FXa, which in turn decreases thrombin generation and thrombus development. The anti-FXa activity of apixaban can be measured using the Rotachrom Heparin chromogenic assay, and it has been shown to increase in a concentration-dependent manner. 2

From the Research

Ant Xa Inhibitors

• Ant Xa inhibitors, such as rivaroxaban and apixaban, are used to prevent and treat deep vein thrombosis (DVT) and pulmonary embolism (PE) 3, 4.
• Rivaroxaban is a direct factor Xa inhibitor that has been shown to be effective in the treatment of DVT and PE, as well as in the prevention of recurrent venous thromboembolism (VTE) 3.
• Apixaban is also a direct factor Xa inhibitor that has been compared to rivaroxaban in terms of efficacy and safety in the treatment of VTE, with some studies suggesting that apixaban may have a lower risk of major bleeding 5, 6.

Efficacy and Safety

• The efficacy and safety of rivaroxaban and apixaban have been compared in several studies, with results suggesting that apixaban may have a lower risk of major bleeding and a trend towards lower risk of recurrent VTE 5, 6.
• A systematic review and meta-analysis of observational studies found that apixaban was associated with a significantly lower risk of major bleeding compared to rivaroxaban for the treatment of VTE 6.
• However, another study found that rivaroxaban was associated with a lower rate of major bleeding compared to enoxaparin-VKA in patients with DVT or PE 3.

Clinical Use

• Rivaroxaban and apixaban are both used in clinical practice for the prevention and treatment of VTE, as well as for stroke prevention in patients with non-valvular atrial fibrillation 4, 5.
• The choice between rivaroxaban and apixaban may depend on individual patient factors, such as renal function and bleeding risk 4, 5.
• Further studies are needed to fully understand the efficacy and safety of these medications in different patient populations and clinical settings 7, 6.