In vitro evaluation of factor IX as novel treatment for factor XI deficiency

Factor XI deficiency is associated with mild to moderate bleeding upon injury. Treatment of bleeding in patients can be a challenge due to the limited availability of factor XI concentrates that may also have thrombotic side effects, and the volume overload as a result of plasma transfusion. In our in vitro study, we established that recombinant factor IX concentrate Benefix(R) (Pfizer) was able to potently enhance thrombin generation in factor XI depleted plasma when coagulation was initiated via the extrinsic pathway. This was due to the contamination of Benefix(R) with very low amounts of factor IXa that compensated for the lack of factor XI in plasma. Our data suggest that bleeding due to factor XI deficiency or antithrombotic therapy targeting factor XI may be treated with certain factor IX concentrates, which should be investigated in future clinical studies.