The new in anticoagulation: factor XI inhibitors.

Haemostasis and thrombosis are closely linked, so that any anticoagulant strategy available today that reduces the thrombotic risk inevitably increases the bleeding risk. However, epidemiological and experimental evidence suggests that inhibiting the contact pathway-the first phase of the intrinsic coagulation pathway-and especially factor XI (FXI) achieves the objective of preventing thrombosis with minimal interference on the haemostatic process. Several pharmacological strategies that act by inhibiting FXI are being studied in clinical trials. Specifically, Phase 2 clinical trials in patients undergoing major orthopaedic surgery, end-stage renal disease, atrial fibrillation (AF), and acute coronary syndrome have shown promising results, allowing clinical research to advance into Phase 3 clinical trials. FXI inhibitors will not necessarily replace currently available direct oral anticoagulants: this would appear too ambitious as of today. However, it is possible to hypothesize that FXI inhibitors are a useful addition to our therapeutic armamentarium in contexts where current anticoagulants have failed or have not been adequately tested, as well as in categories of patients who are at a high risk of bleeding even with current direct oral anticoagulants.