Combination of FVIII and by-passing agent potentiates in vitro thrombin production in haemophilia A inhibitor plasma.
The by-passing agents, recombinant activated factor VII (rFVIIa) and activated prothrombin complex concentrate (APCC), are important tools in the treatment of patients with haemophilia A and high-responding inhibitory antibodies. It has been observed clinically that in some patients undergoing immune tolerance induction the bleeding frequency decreases, hypothetically caused by a transient haemostatic effect of infused FVIII not measurable ex vivo. We evaluated how by-passing agents and factor VIII (FVIII) affect thrombin generation (TG) in vitro using plasma from 11 patients with severe haemophilia A and high titre inhibitors. Samples were spiked with combinations of APCC, rFVIIa and five different FVIII products. Combination of APCC and FVIII showed a synergistic effect in eliciting TG (P<0·005) for four FVIII products. When rFVIIa and FVIII were combined the interaction between the preparations was found to be additive. APCC and rFVIIa were then combined without FVIII, resulting in an additive effect on thrombin production. Each product separately increased TG above baseline. In conclusion, the amount of thrombin formed in vitro by adding a by-passing agent, was higher in the presence of FVIII. Our findings support the use of FVIII in by-passing therapy to optimize the haemostatic effect.
Department for Coagulation Disorders, Lund University, Skåne University Hospital, Malmö, Sweden. jenny.klintman@med.lu.se
Jenny
J
Klintman
Jan
J
Astermark
Erik
E
Berntorp
D001323:Autoantibodies / Q000097:blood; D001779:Blood Coagulation Factors / Q000008:administration & dosage / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004357:Drug Synergism; D005169:Factor VIII / Q000037:antagonists & inhibitors / Q000276:immunology / Q000494:pharmacology*; D015942:Factor VIIa / Q000008:administration & dosage / Q000494:pharmacology; D006467:Hemophilia A / Q000097:blood* / Q000276:immunology; D006801:Humans; D066298:In Vitro Techniques; D011994:Recombinant Proteins / Q000008:administration & dosage / Q000494:pharmacology; D013917:Thrombin / Q000096:biosynthesis*
D001323:Autoantibodies; D001779:Blood Coagulation Factors; D011994:Recombinant Proteins; C025667:prothrombin complex concentrates; D005169:Factor VIII; C103587:recombinant FVIIa; D015942:Factor VIIa; D013917:Thrombin