Factor XI Antisense Oligonucleotide for Venous Thrombosis

New England Journal of Medicine 372(17):1671 (2015) PMID 25901434

To the Editor: I would caution against concluding, on the basis of the study by Büller et al. (Jan. 15 issue),1 that reducing factor XI levels attenuates the risk of thrombosis without increasing the risk of bleeding. Factor XI deficiency selectively increases the risk of bleeding in tissues with high fibrinolytic activity, such as after dental surgery, tonsillectomy, or prostate surgery and in the postpartum state.2,3 Thrombin generated by the intrinsic pathway is primarily responsible for activating thrombin-activatable fibrinolysis inhibitor (TAFI). In the absence of factor XI and, thus, TAFI, a clot formed in tissues with high fibrinolytic activity . . .

DOI: 10.1056/NEJMc1503223