Martin Erika J, Nolte Melinda E, Kuhn Janice, Schmidt Nicole, Pfaff Nils, Brophy Donald F
Coagulation Advancement Laboratory, Department of Pharmacotherapy & Outcomes Sciences, Virginia Commonwealth University (VCU) School of Pharmacy, Richmond, VA, USA.
Department of Internal Medicine, Division of Hematology/Oncology, VCU School of Medicine, Richmond, VA, USA.
Haemophilia. 2021 Jul;27(4):690-698. doi: 10.1111/hae.14314. Epub 2021 Apr 29.
Tissue factor pathway inhibitor (TFPI) is an endogenous protein that inhibits the extrinsic (tissue factor) pathway and negatively regulates thrombin production during coagulation. Inhibiting TFPI may become a useful target for haemophilia drug development to allow greater thrombin generation without use of the intrinsic (contact) pathway.
The in vitro effects of befovacimab, a humanized TFPI neutralizing antibody, were studied in whole blood and plasma samples from patients with severe FVIII deficiency.
Blood and plasma obtained from participants was supplemented in vitro with befovacimab (0.5, 1, 5, 10 and 100 nM) or recombinant factor VIII (rFVIII) 5-, 10- and 40% and analysed using rotational thromboelastometry (ROTEM), thrombin generation assay (TGA) and the dilute prothrombin time (dPT) assay. The in vitro coagulation effects of befovacimab were compared to samples supplemented with rFVIII.
Befovacimab induced consistent pro-coagulant responses in ROTEM parameters including reduction in clotting times and increases in α-angle; induced reductions in dPT clotting time; and improvements in TGA parameters (reduced lag time and increased thrombin generation parameters). There was a modest concentration-dependent response generally from 0.5- to 10 nM, after which, the pharmacodynamic effect plateaued through the 100 nM concentration. Befovacimab concentrations of 5 to 10 nM showed pro-coagulant activity comparable to blood samples supplemented with rFVIII 10-40%.
Befovacimab has modest dose-response effects from 0.5 to 10 nM with minimal improvement with higher concentrations. In vitro befovacimab blood concentrations of 5 to 10 nM had pro-coagulant effects similar to blood supplemented with rFVIII 10- to 40%.
组织因子途径抑制剂（TFPI）是一种内源性蛋白质，可抑制外源性（组织因子）途径，并在凝血过程中对凝血酶的产生起负调节作用。抑制TFPI可能成为血友病药物开发的一个有用靶点，从而在不使用内源性（接触）途径的情况下实现更大程度的凝血酶生成。
研究人源化TFPI中和抗体贝伏西单抗在重度FVIII缺乏患者全血和血浆样本中的体外作用。
将参与者的血液和血浆在体外分别补充贝伏西单抗（0.5、1、5、10和100 nM）或重组因子VIII（rFVIII）5%、10%和40%，并使用旋转血栓弹力图（ROTEM）、凝血酶生成测定（TGA）和稀释凝血酶原时间（dPT）测定进行分析。将贝伏西单抗的体外凝血作用与补充rFVIII的样本进行比较。
贝伏西单抗在ROTEM参数中诱导了一致的促凝血反应，包括凝血时间缩短和α角增加；dPT凝血时间缩短；以及TGA参数改善（滞后时间缩短和凝血酶生成参数增加）。一般在0.5至10 nM之间有适度的浓度依赖性反应，之后，药效学效应在100 nM浓度时达到平台期。5至10 nM的贝伏西单抗浓度显示出与补充10%-40% rFVIII的血样相当的促凝血活性。
贝伏西单抗在0.5至10 nM之间有适度的剂量反应效应，更高浓度时改善作用最小。体外5至10 nM的贝伏西单抗血药浓度具有与补充10%-40% rFVIII的血液相似的促凝血作用。
