Safety, pharmacokinetics and efficacy of factor VIIa formulated with PEGylated liposomes in haemophilia A patients with inhibitors to factor VIII - an open label, exploratory, cross-over, phase I/II study

Recombinant activated factor VIIa (FVIIa) is a bypassing agent used to treat bleeding episodes in haemophilia patients with inhibitors to factor VIII (FVIII) and factor IX. The pharmacological effect of FVIIa is short‐lived and therefore with the recommended dose of 90 μg kg−1, a bleeding episode is treated with multiple injections. A long‐acting form of FVIIa that can ensure adequate haemostasis with a single infusion, without increasing the thrombotic risk, would therefore be beneficial. PEGylated liposomes (PEGLip) have been shown to bind FVIIa and to improve haemostatic efficacy in preclinical experiments. In the present phase I/II clinical trial, we assessed the safety and efficacy of PEGLip‐formulated FVIIa in severe haemophilia A patients (FVIII ≤ 1%) with inhibitors to FVIII. Each patient received one prophylactic infusion of standard FVIIa and one prophylactic infusion of PEGLip‐formulated FVIIa. The order of the infusions was randomized and the two infusions were separated by a ten‐day washout period. Efficacy assessed by thromboelastography revealed that PEGLip‐FVIIa induced significantly shorter clotting times and produced higher clot firmnesses than standard FVIIa. Thrombin generation assays showed that PEGLip‐FVIIa induced faster thrombin generation and higher peak levels of thrombin than standard FVIIa. These effects lasted up to 5 h postinfusion. Measurements of D‐dimer, prothrombin fragment 1 + 2 and fibrinogen showed no significant differences between the PEGLip‐FVIIa and standard FVIIa treatments. PEGLip‐FVIIa therefore showed improved haemostatic efficacy without increased risk of thrombosis and may be further developed for the treatment for bleeding episodes in haemophilia patients with inhibitors.