Increased volume of distribution for recombinant activated factor VII and longer plasma-derived factor VII half-life may explain their long lasting prophylactic effect.

INTRODUCTION: Prophylaxis with plasma-derived or recombinant activated factor VII is beneficial in severe factor VII deficiency. To understand why prophylactic treatment with both products is efficacious, we conducted a pharmacokinetic study. MATERIALS AND METHODS: Ten factor VII deficient patients were treated with either recombinant activated (20 µg/kg) or plasma-derived (25 IU/kg) factor VII in a cross-over design. Pharmacokinetic parameters were analyzed through activated factor VII activity, factor VII clotting activity, and factor VII antigen levels on depicted time points. RESULTS: Factor VII activity half-lifes, determined by non-compartmental and one-compartmental analysis (results in brackets), were shorter for recombinant activated (1.4h; 0.7h) than for plasma-derived factor VII (6.8h; 3.2h); both recombinant activated (5.1h; 2.1h and plasma-derived factor VII (5.8h; 3.2h) resulted in longer half-lives of factor VII antigen. Activated factor VII half-lives (based on activated factor VII activity levels) were significantly higher compared to factor VII clotting activity (1.6h; 0.9h). Volumes of distribution were significantly higher for activated factor VII (236 ml/kg; 175 ml/kg, measured by activated factor VII) as compared to plasma-derived factor VII (206 ml/kg; 64 ml/kg, measured by factor FVII activity), suggesting a plasma- and extracellular fluid distribution for recombinant activated factor VII. CONCLUSIONS: Recombinant activated factor VII showed significantly shorter half-lifes than plasma-derived factor VII. Volumes of distribution were significantly higher for treatment with recombinant activated factor VII. The longer half-life for plasma-derived factor VII, compared to recombinant activated factor VII, and the increased volume of distribution for recombinant activated factor VII, compared to plasma-derived factor VII may further elucidate the beneficial effect of prophylactic treatment of both products.

Pharmacodynamics of recombinant activated factor VII and plasma-derived factor VII in a cohort of severe FVII deficient patients.

Recombinant activated factor VII (rFVIIa) and plasma-derived factor VII (pdFVII) are used to prevent bleedings in severe FVII deficient patients, despite their short half-lifes. It is suggested that FVII levels of 15-20 IU/dL are sufficient to maintain hemostasis. We analyzed the pharmacodynamic effects of FVII substitution therapy in the Nijmegen Hemostasis Assay (NHA) that simultaneously measures thrombin and plasmin generation. Ten severe FVII deficient patients were treated with 20 µg/kg rFVIIa or 25 IU/kg pdFVII in a cross-over design. Thrombin generation lag-time (TG-LT) was identified as an effect-response parameter. Pharmacodynamic analysis using a maximum effect model showed 50% reduction of the TG-LT effect at ~2 IU/dL FVII activity for both rFVIIa and pdFVII. The FVII activity to obtain TG-LT comparable to the upper limit of normal range in healthy controls (4 min) was given by the effective concentration (ECnormal), showing sufficient hemostasis at 3-4 IU/dL FVII activity. No association was seen between FVII activity and other thrombin or plasmin generation parameters as measured by NHA. In conclusion, 3-4 IU/dL FVII activity seems sufficient to maintain hemostasis in patients with severe FVII deficiency during prophylaxis. These data may suggest a potential value for measurement of TG-LT in the monitoring of FVII(a) therapy.

Prophylactic effect of recombinant factor VIIa in factor VII deficient patients.

Inherited factor VII (FVII) deficiency is a rare autosomal recessive disorder associated with a bleeding tendency. We describe three patients with congenital FVII deficiency who have been treated with activated recombinant factor VII (rVIIa). Two patients had novel mutations and were treated prophylactically with 1.2 mg rVIIa two to three times a week. Patients 1 and 2 had a severe bleeding tendency. The frequency and severity of bleeding decreased by treatment with rVIIa compared with similar treatment with plasma-derived FVII. The third patient with a moderate bleeding phenotype was treated on demand and showed no change in the frequency of bleeding upon treatment with rVIIa or plasma products. The beneficial effect of rVIIa cannot be explained by the rVIIa half-lives. Pharmacokinetical analysis showed rVIIa activity half-lives of 35, 50 and 54 min for patients 1, 2 and 3, respectively. In conclusion, prophylactic treatment of FVII deficient patients with rVIIa appears to be applicable, safe and successful, although the mechanism of action remains to be elucidated.