Replacement
therapy with
factor VIII (FVIII) and
factor IX (FIX) is routinely used in
haemophilia patients with
haemophilia A and B, respectively, while recombinant activated FVII (
rFVIIa) has proven to induce haemostasis in
haemophilia patients with inhibitors. To evaluate the effect of therapeutic intervention in patients with residual factor activities, the effects of increasing concentrations of
rFVIIa or
NN1731 on
thrombin generation and platelet activation were measured in a cell-based model system mimicking severe, moderate and mild
haemophilia A or B. Purified monocytes stimulated to express
tissue factor and non-activated platelets from peripheral blood of healthy donors were incubated with a mixture of purified human
coagulation factors in the absence or presence of increasing concentrations of FVIII or FIX. Sub-samples were analysed for
thrombin activity and platelet activation measured as exposure of
P-selectin by flow cytometry. Dose-dependent increases in
thrombin generation and platelet activation were observed following increasing concentrations of
rFVIIa or
NN1731 in both
haemophilia A- and B-like conditions. At 25 nm
rFVIIa, which nears the peak levels in patient plasma after 90 microg kg(-1) intravenous dosing, the effects on maximum
thrombin generation rate (maxTG) at 1-10% FVIII were comparable to those at 100% and 200% FVIII in the absence of
rFVIIa. Normalization of maxTG required 500 nm
rFVIIa and 25 nm
NN1731 or 25-100 nm
rFVIIa and 5 nm
NN1731 in severe or moderate/mild
haemophilia A and
haemophilia B, respectively. This suggests that
NN1731 holds its promise as a future bypassing agent for
haemophilia patients with and without inhibitors.