TY - JOUR
T1 - A highly sensitive thrombin generation assay for assessment of recombinant activated factor VII therapy in haemophilia patients with an inhibitor
AU - Livnat, Tami
AU - Martinowitz, Uri
AU - Zivelin, Ariella
AU - Rima, Dardik
AU - Kenet, Gili
PY - 2011/4
Y1 - 2011/4
N2 - Bypass agents are the common treatment for haemophilia patients who develop inhibitory antibodies. Laboratory assessment of the efficacy of bypassing agent therapy is a challenge. In the present work we modified the conditions triggering thrombin generation (TG) assay in order to find the most sensitive assay for detection of rFVIIa and its ana- logue NN1731 in haemophilic plasma. TG was measured in samples of normal plasma, plasma of haemophilia patient with inhibitors, as well as haemophilia induced plasma. Recalcification-induced TG was com- pared to tissue factor (TF) -induced TG in the presence and absence of rFVIIa and NN1731. Recalcification-induced TG (without TF) in haemophilic plasma yielded baseline flat curves, with increased TG as a consequence of spiking the plasma rFVIIa. Using our system, we observed both dose-dependence and time-dependence of rFVIIa effect on TG. Elevated concentrations of TF mask the difference between rFVIIa- treated and non-treated haemophilic plasma. NN1731 yielded normalisation of recalcification-induced TG curves (without TF) which may reflect high potency. In conclusion, we suggest that triggering TG by recalcification-only may be the most sensitive assay for determining the impact of bypassing agents in haemophilic plasma, and may serve as a caution surrogate safety marker in future studies.
AB - Bypass agents are the common treatment for haemophilia patients who develop inhibitory antibodies. Laboratory assessment of the efficacy of bypassing agent therapy is a challenge. In the present work we modified the conditions triggering thrombin generation (TG) assay in order to find the most sensitive assay for detection of rFVIIa and its ana- logue NN1731 in haemophilic plasma. TG was measured in samples of normal plasma, plasma of haemophilia patient with inhibitors, as well as haemophilia induced plasma. Recalcification-induced TG was com- pared to tissue factor (TF) -induced TG in the presence and absence of rFVIIa and NN1731. Recalcification-induced TG (without TF) in haemophilic plasma yielded baseline flat curves, with increased TG as a consequence of spiking the plasma rFVIIa. Using our system, we observed both dose-dependence and time-dependence of rFVIIa effect on TG. Elevated concentrations of TF mask the difference between rFVIIa- treated and non-treated haemophilic plasma. NN1731 yielded normalisation of recalcification-induced TG curves (without TF) which may reflect high potency. In conclusion, we suggest that triggering TG by recalcification-only may be the most sensitive assay for determining the impact of bypassing agents in haemophilic plasma, and may serve as a caution surrogate safety marker in future studies.
KW - Coagulation factors
KW - Factor VIII inhibitors
KW - Haemophilia A/B
KW - Haemophilia therapy
UR - http://www.scopus.com/inward/record.url?scp=79955429941&partnerID=8YFLogxK
U2 - 10.1160/TH10-08-0542
DO - 10.1160/TH10-08-0542
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C2 - 21225093
AN - SCOPUS:79955429941
SN - 0340-6245
VL - 105
SP - 688
EP - 695
JO - Thrombosis and Haemostasis
JF - Thrombosis and Haemostasis
IS - 4
ER -