A variant of recombinant factor VIIa with enhanced procoagulant and antifibrinolytic activities in an in vitro model of hemophilia.
OBJECTIVE
Recombinant factor VIIa (rFVIIa, NovoSeven) has proven efficacy in treating bleeding in hemophilia patients with inhibitors. A rFVIIa analog with mutations V158D/E296V/M298Q (NN1731) exhibits increased procoagulant activity in in vitro and in vivo models. The aim of this work was to define the effects of NN1731 toward factor X activation, platelet activation, thrombin generation, and fibrin clot formation and stability.


RESULTS
In a cell-based in vitro model of hemophilia, rFVIIa and NN1731 similarly increased factor X activation on tissue factor-bearing cells; however, NN1731 exhibited 30-fold higher factor Xa generation on platelets than similar rFVIIa concentrations. NN1731-mediated thrombin generation depended on platelet activation, but NN1731 did not directly activate platelets. NN1731 produced 4- to 10-fold higher maximal thrombin generation rates than equal rFVIIa concentrations. Both rFVIIa and NN1731 shortened clotting times in the absence of factors IX and VIII; however, NN1731 did so at 50-fold lower concentrations than were required of rFVIIa. In fibrinolytic conditions, both rFVIIa and NN1731 increased fibrin formation and stability; however, NN1731 was effective at 50-fold lower concentrations than were required of rFVIIa.


CONCLUSIONS
By increasing factor Xa generation, NN1731 promotes the formation of thrombin and a stable clot to a greater degree than rFVIIa.
Allen
Geoffrey A
GA
Department of Pediatrics, University of North Carolina, Chapel Hill, NC, USA.
Persson
Egon
E
Campbell
Robert A
RA
Ezban
Mirella
M
Hedner
Ulla
U
Wolberg
Alisa S
AS
D000933:Antifibrinolytic Agents / Q000494:pharmacology; D001792:Blood Platelets / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D015942:Factor VIIa / Q000494:pharmacology*; D005170:Factor X / Q000378:metabolism*; D006467:Hemophilia A / Q000097:blood* / Q000188:drug therapy*; D006801:Humans; D066298:In Vitro Techniques; D007963:Leukocytes, Mononuclear / Q000187:drug effects / Q000502:physiology; D015539:Platelet Activation / Q000187:drug effects*; D011994:Recombinant Proteins; D012680:Sensitivity and Specificity; D013917:Thrombin / Q000502:physiology
D000933:Antifibrinolytic Agents; D011994:Recombinant Proteins; D005170:Factor X; D015942:Factor VIIa; D013917:Thrombin