Andexanet alfa is a specific reversal agent for Factor Xa inhibitors (rivaroxaban, apixaban). Its mechanism of action differs from idarucizumab (dabigatran reversal) because andexanet alfa acts as:

• A A monoclonal antibody that binds and neutralises Factor Xa inhibitors in plasma
• B An activated Factor Xa analogue that regenerates the coagulation cascade independently
• C A catalytically inactive recombinant Factor Xa decoy protein that sequesters Factor Xa inhibitors ✓
• D A vitamin K epoxide reductase activator that replenishes clotting factor synthesis

Explanation

Andexanet alfa is a modified recombinant human Factor Xa protein that is catalytically inactive (Gla-domain deleted, active site serine mutated to alanine). It acts as a 'decoy' Factor Xa molecule: it binds Factor Xa inhibitors (rivaroxaban, apixaban, betrixaban, edoxaban) with high affinity, sequestering them away from native Factor Xa and restoring coagulation. In contrast, idarucizumab is a Fab fragment of a monoclonal antibody that directly binds and neutralises dabigatran (a direct thrombin inhibitor). Andexanet does not possess coagulation activity itself. It also sequesters low-molecular-weight heparins by binding antithrombin in a non-productive complex.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.