Pharmacologic Factor XI/XIa Inhibitors: What the Laboratory Hematologist Needs to Know.

Inhibitors of the protease factor XIa (FXIa) and its zymogen factor XI (FXI) represent a promising new class of anticoagulants that aim to offer safer alternatives to traditional therapies. With their potential to reduce thrombosis without a dose-dependent increase in bleeding, FXIa inhibitors are currently undergoing rigorous phase 3 testing. This article reviews unmet needs in anticoagulation therapy, explains the role of FXI in distinguishing hemostasis from thrombosis, describes FXI/FXIa inhibitors and their effects on coagulation tests, and provides insights into ongoing clinical trials. Our goal is to equip laboratory hematologists with the knowledge to understand these novel agents.