Recombinant Activated Factor VII in Patients at High Risk of Bleeding

Currently, recombinant activated factor VII (rFVIIa) (NovoSeven) is indicated for the treatment of spontaneous and surgical bleeding in congenital haemophilia A and B patients with inhibitors to factors VIII (FVIII) and IX (FIX) >5 Bethesda units (BU) worldwide, and in patients with acquired haemophilia, congenital FVII deficiency and Glanzmann's thrombasthenia in Europe. Until April 2003, almost three-quarters of a milion doses of rFVIIa have been administered proving its efficacy and excellent safety record. According to results from initial clinical trials and a large number of case reports, the rFVIIa may be effective not only in treating haemophilia patients but also in treatment of bleeding in patients on oral anticoagulation or heparin, patients with liver diseases, von Willebrand disease (vWD), thrombocytopenia, various platelet defects, congenital or acquired deficiency of FVII, and in subjects without any pre-existing coagulopathy with diffuse life-threatening bleeding triggered by surgery or trauma. This review will briefly summarize rFVIIa mode of action in haemostasis, the current clinical experience with rFVIIa and focus on the alternative use of rFVIIa in patients at the high risk of bleeding in both spontaneous cases and clinical trials reports.

Allometric extrapolation of factors VII, VIII and IX clearance in children from adults

BACKGROUND

There are situations where a pharmacokinetic (PK) study may not be possible in children, especially in neonates and infants. Under these circumstances, one would like to extrapolate PK parameters from adults or older children to neonates and infants. Allometric scaling is a method which can be used for PK extrapolation from adults to children.

OBJECTIVES

The objective of this study was to evaluate the predictive performance of an allometric model for the prediction of clearance of three coagulation factors in children from adult clearance.

METHODS

Clearance values for three coagulation factors (rVIIa, rVIII and rIX) for adults and children were obtained from the literature. The allometric model was developed from adult data and then the model was used to predict clearance of the coagulation factors in individual child. The predicted clearance value was then compared with the observed clearance value in that child.

RESULTS

The results of the study indicated that the CL of the three coagulation factors tested in this study could be predicted with accuracy (≤30% prediction error) in most of the children from the allometric model developed from adults.

CONCLUSIONS

The study indicated that allometric scaling could be applied to predict the CL of coagulation factors in children from adults with accuracy. The predicted clearance can then be used to select a dose to initiate a clinical trial (pharmacokinetics, safety and efficacy) in children.

Plasma elimination kinetics for factor VII are independent of its activation to factor VIIa and complex formation with plasma inhibitors

The mechanism for the elimination of factor VII (FVII) from the circulation is unknown, just as it is unclear how activation of FVII to FVIIa and subsequent complex formation with antithrombin III (AT) or alpha2-macroglobulin (alpha2M) affects clearance. The possibility that the clearance mechanism involves activation and inhibitor complex formation as obligatory intermediate reactions is examined in this study. Human and murine sera were spiked with human FVIIa in the absence and presence of heparin and analysed for complex formation. Complex formation in vivo was studied after intravenous injection of (125)I-VIIa in mice; and the pharmacokinetics (PK) of human and murine FVIIa was studied in normal mice. Furthermore, comparative PK studies were performed with FVII, FVIIa, active site blocked FVIIa and a preformed FVIIa-AT complex in normal and alpha2M-deficient mice. The data demonstrated that FVIIa-AT complexes and to a much lesser extent FVIIa-alpha2M-complexes accumulated in vivo after FVIIa administration. FVIIa-AT accounted for about 50% of total FVIIa antigen left in the circulation after 3 hours. All FVII derivatives studied including FVII, FVIIa and FVIIa-AT were cleared with similar rates suggesting an elimination kinetics which is unaffected by FVII activation and subsequent inactivation by plasma inhibitors.

Evaluation of the safety and pharmacokinetics of a fast-acting recombinant FVIIa analogue, NN1731, in healthy male subjects

BACKGROUND

NN1731 is a recombinant activated factor VII (rFVIIa) analog with enhanced activity.

OBJECTIVES

This clinical trial aimed to assess the safety and pharmacokinetics of single doses of NN1731 in healthy male subjects.

METHODS

This was a randomized, placebo-controlled dose-escalation trial with four dose tiers (NN1731 5-30 microg kg(-1)). Eight subjects were randomized to either NN1731 (n = 6) or placebo (n = 2) in each tier.

RESULTS

No thromboembolic or serious adverse events were reported and no antibody formation towards NN1731 was detected. NN1731 was demonstrated to be pharmacologically active based on coagulation-related parameters (prothrombin fragment 1+2, activated partial thromboplastin time and prothrombin time). There were five mild/moderate adverse events in three subjects. The FVIIa activity of NN1731 after ascending single-dose administration of NN1731 fits well with a two-compartment model, indicating a bi-exponential decline with a rapid initial distribution of approximately 73% FVIIa activity (half-life = 20 min), followed by a less rapid terminal elimination phase eliminating the remaining 27% (half-life = 3 h). Dose proportionality in healthy male subjects at the dose levels investigated (5-30 microg kg(-1)) was supported by the FVIIa activity data.

CONCLUSIONS

Based on the results of this trial, NN1731 appears safe and well tolerated in healthy subjects at doses up to 30 microg kg(-1). No immunogenic or thromboembolic events were reported. The pharmacokinetic profile of NN1731 as measured by FVIIa activity appears to follow two-compartment pharmacokinetics characterized by an initial rapid distribution phase followed by a less rapid elimination phase.

Pharmacokinetics of Beriplex P/N prothrombin complex concentrate in healthy volunteers

Prothrombin complex concentrates (PCCs) are widely administered for emergency oral anticoagulation reversal and for coagulation defects in liver disease. Pharmacokinetic data may help to optimize treatment. The objective of this study was to characterize the pharmacokinetics of a PCC (Beriplex P/N) containing coagulation factors II (FII), VII (FVII), IX (FIX) and X (FX) and anticoagulant proteins C and S. Fifteen healthy volunteers received a single rapid 50 IU/kg infusion of PCC and underwent frequent blood sampling until 144 hours (h) after infusion. Coagulation factors and anticoagulant protein pharmacokinetic parameters were estimated by non-linear regression. The mean infusion rate of PCC was 7.9 ml/min, equivalent to 196.4 IU/min. By the earliest post-infusion sampling point at 5 minutes (min), plasma FIX concentration increased by a median of 73%. Median increases in FII, FVII and FX at 5 min were 122%, 62% and 158%, respectively. Proteins C and S also increased rapidly. The median terminal half-life of FIX was 16.7 h, FII 59.7 h, FVII 4.2 h and FX 30.7 h. The median in-vivo recovery of FIX was 1.57 %/IU/kg and that of the other three coagulation factors > 2 %/IU/kg. Plasma concentration of thrombogenicity marker D-dimer did not increase, and there was no clinical evidence of thrombosis. Through up to 12 weeks follow-up there were no laboratory findings indicating PCC-related viral exposure. Rapid PCC infusion produced prompt sustained increases in coagulation factors and anticoagulant proteins with no clinical evidence of thrombosis or viral transmission.

ReFacto and Advate: a single-dose, randomized, two-period crossover pharmacokinetics study in subjects with haemophilia A

ReFacto is a recombinant B-domain-deleted, monoclonal antibody-purified, solvent-detergent-treated factor VIII (BDDrFVIII) with no albumin added to the final formulation. Although ReFacto has been shown to be bioequivalent to a plasma-derived FVIII product (Hemophil-M) in a randomized, crossover pharmacokinetic (PK) study, the comparability of ReFacto with the full-length (complete sequence) recombinant FVIII (FLrFVIII, Advate) product has not been previously examined in this manner. The primary objective of this study was to compare the PKs of ReFacto with those of Advate in patients with severe haemophilia A. This was a third-party unblinded, randomized, multicentre, two-period crossover PKs study of ReFacto and Advate in subjects with severe haemophilia A (FVIII:C < or =1%). Blood samples were collected over a 48-h period after i.v. administration of each of the FVIII products. FVIII:C was determined using the chromogenic substrate assay (CSA) in a central laboratory. The plasma FVIII:C PK parameters of ReFacto and Advate were determined using non-compartmental analysis. Bioequivalence was assessed on maximum plasma concentration (C(max)) and the area under the plasma concentration vs. time curves (AUCs) using an anova. The two products were judged to be equivalent if the 90% confidence limits of the ratio of the geometric mean values of C(max) and AUCs fell within the interval of 80-125%. Results from this PKs comparison of two different rFVIII products, using chromogenic substrate assay to measure FVIII:C, showed that ReFacto and Advate are bioequivalent to each other.

A randomized, double-blind trial demonstrating bioequivalence of the current recombinant activated factor VII formulation and a new robust 25°C stable formulation

Recombinant activated factor VIIa (rFVIIa) is a well-established treatment for bleeding episodes in patients with congenital or acquired haemophilia A or B with inhibitors to factors VIII and IX and patients with FVII deficiency. The aim of this trial was to demonstrate bioequivalence between the currently marketed (rFVIIa/NovoSeven) and a new rFVIIa formulation (VII25) stable at up to 25 degrees C. Furthermore, short-term safety and tolerability of VII25 and pharmacokinetics of both formulations were investigated. In this single-centre, randomized, double-blind, two-way cross-over trial, healthy male subjects received one intravenous bolus injection of rFVIIa and one of VII25, both at 90 microg kg(-1), in a randomized order 2-3 weeks apart. Mean VII25/rFVIIa ratio for area under the plasma activity-time curve from time 0 to last quantifiable activity (primary bioequivalence endpoint), was 0.93, 90% confidence interval (CI) (0.89-0.96), within the predefined bioequivalence range (0.80-1.25). Secondary pharmacokinetic parameters were comparable between formulations. No serious adverse events were observed. Six mild or moderate treatment-emergent adverse events were reported in five subjects. Coagulation-related parameter profiles were similar between rFVIIa and VII25. No clinically abnormal changes were observed for laboratory parameters and no subjects developed FVIIa antibodies. This trial demonstrated bioequivalence between the currently available rFVIIa and VII25 stable at up to 25 degrees C. VII25's 'user-friendly' formulation removes the inconvenience of storing/transporting at 2-8 degrees C, and as the drug substance is the same, the activity and safety established for rFVIIa is maintained.

The Evidence for the Use of Recombinant Human Activated Factor VII in the Treatment of Bleeding Patients With Quantitative and Qualitative Platelet Disorders

There are increasing reports suggesting that high-dose recombinant human activated factor VII (rFVIIa) is effective in the treatment and prevention of bleeding in patients with quantitative and qualitative platelet disorders. These clinical observations are supported by evidence that FVIIa binds weakly to activated platelet surface and at high concentration improves thrombin generation. In experimental models, this improved thrombin generation enhances platelet adhesion in thrombocytopenic conditions and enhances adhesion and aggregation of platelets lacking glycoprotein IIbIIIa (integrin alpha(IIb)beta(3)), characteristic of the qualitative platelet disorder Glanzmann thrombasthenia (GT). There is a need for clinical trials to confirm the safety and efficacy of rFVIIa in patients with various quantitative and qualitative platelet defects, either by itself or in combination with other hemostatic agents such as platelet transfusion. Pending the availability of such data, rFVIIa may be considered in severe bleeding in thrombocytopenia and GT patients with platelet antibodies and refractory to platelet transfusions and other standard treatments. An international survey suggests that rFVIIa at about 90 microg/kg every 2 hours for 3 or more doses could be used for GT patients with severe bleeding, but confirmation by larger studies is needed. For GT patients undergoing surgery and for treatment and prevention of bleeding in thrombocytopenic patients, the optimal rFVIIa regimen remains to be defined.

The pharmacokinetics of coagulation factors

In this article, we provide a summary of the generally accepted approaches to the design and analysis of studies examining the pharmacokinetic (PK) profile of an infused coagulation factor in patients with a deficiency of one or more of these factors. Furthermore, we briefly review the known PK results for various commercially available coagulation factor preparations under single and continuous infusion.

Pharmacokinetics of recombinant activated factor VII in trauma patients with severe bleeding

INTRODUCTION

Recombinant activated factor VII (rFVIIa) has been used as adjunctive therapy in trauma patients with severe bleeding. However, its pharmacokinetics profile remains unknown.

METHODS

In two placebo-controlled studies in patients with blunt and penetrating trauma, the pharmacokinetics of rFVIIa given at an initial dose of 200 microg x kg-1 after transfusion of eight red blood cell units, followed by additional doses of 100 microg x kg-1, one and three hours later, have been studied, based on the FVII coagulant activity assay. Both non-compartment and population pharmacokinetic analyses were performed. A two-compartment, population pharmacokinetic model was used to estimate a population profile for the rFVIIa dosing regimen. Data are population means (percent coefficient of variation (CV)).

RESULTS

Based on the two-compartment population model, the estimated pharmacokinetic parameters were: clearance 40 (30% CV) ml x kg-1 x h-1; central volume of distribution 89 (32% CV) ml x kg-1; inter-compartmental clearance 24 ml x kg-1 x h-1; and peripheral compartment volume 31 ml x kg-1. Baseline FVII coagulant activity was estimated at 0.29 (39% CV) U x ml-1, initial half-life was 0.6 (34% CV) hours, and terminal half-life 2.4 (50% CV) hours. High intra- and inter-patient variability was noted in volume of distribution and clearance, which was in part correlated with the transfusion requirements as the single significant covariate. The non-compartmental analysis led to almost identical estimates of key parameters.

CONCLUSION

A high intra- and inter-patient variability was noted in the volume of distribution and clearance of rFVIIa in trauma patients with severe bleeding, mainly related with the transfusion requirements and thus blood loss and/or bleeding rate.

Recombinant Factor VIIa: A Review on Its Clinical Use

Recombinant activated factor VII (rFVIIa) (NovoSeven) is a novel hemostatic agent originally developed to treat bleeding episodes in hemophilic patients with inhibitors against coagulation factors VIII and IX. In recent years, rFVIIa has also been employed for the management of uncontrolled bleeding in a number of congenital and acquired hemostatic abnormalities. Based on a literature search including PubMed, references from reviews, and abstracts from the most important meetings on this topic, this review examines the current knowledge on therapy with rFVIIa, from the now well-standardized uses to the newer and less well-characterized clinical applications.

High-Dose Recombinant Factor VIIa Therapy in Hemophilia Patients With Inhibitors

Recombinant activated factor VII (rFVIIa; NovoSeven, Novo Nordisk, Bagsvaerd, Denmark) is well established as an effective hemostatic agent for the management and prophylaxis of hemorrhage in hemophilia patients with inhibitors. Treatment schedules usually involve multiple bolus doses of 90 to 120 microg/kg administered every 2 to 3 hours, but recent evidence suggests that the use of higher doses might be justified. Such high-dose regimens may overcome the rapid clearance rate observed in pediatric patients, and may be more convenient for patients with poor venous access. It has been suggested that individually tailored high-dose therapies might be beneficial in selected groups of patients, although careful monitoring of such patients is advised. Thrombelastography has demonstrated considerable success in this regard, allowing accurate assessment of both hemostatic efficacy and individual response to rFVIIa. To date, no safety issues associated with high-dose rFVIIa have been identified. However, it is hoped that further research will support these favorable observations and thus contribute towards more effective dose optimization of rFVIIa in hemophilic inhibitor patients.

Recombinant activated factor VIIa and hemostasis in critical care: a focus on trauma

In this article we describe the current use of recombinant activated factor VII (rFVIIa; NovoSeven) in trauma patients. Emphasis is placed on current uses as defined by key studies, efficacy data, and safety data. Most published studies in trauma patients are retrospective case studies and reports, although an international, double-blind, randomized, controlled, phase II study has been conducted that reported on the efficacy of rFVIIa in reducing the amount of blood products transfused in blunt trauma patients. That study demonstrated the efficacy and safety profile of this hemostatic agent as compared with placebo as adjunctive therapy in the management of severe bleeding associated with trauma. Further prospective, randomized, and placebo-controlled clinical trials will yield more information on the role of rFVIIa in the management of traumatic bleeding.

Recombinant activated factor VII in treatment of bleeding complications following hematopoietic stem cell transplantation

BACKGROUND

Bleeding is a common complication following hematopoietic stem cell transplantation (HSCT) and standard hemostatic treatment is often ineffective. We conducted a multicentre, randomized trial of the efficacy and safety of activated recombinant factor VII (rFVIIa, NovoSeven) in the treatment of bleeding following HSCT.

METHODS

100 patients with moderate or severe bleeding (52 gastrointestinal; 26 hemorrhagic cystitis; seven pulmonary; one cerebral; 14 other) were included from days +2 to +180 post-transplant (97 allogeneic; three autologous) to receive seven doses of rFVIIa (40, 80 or 160 microg kg(-1)) or placebo every 6 h. The primary efficacy endpoint was the change in bleeding score between the first administration and 38 h.

RESULTS

No significant effect of increasing rFVIIa dose was observed on the primary endpoint. A post hoc analysis comparing each rFVIIa dose with placebo showed that 80 microg kg(-1) rFVIIa improved the bleeding score at the 38 h time point (81% vs. 57%, P = 0.021). This effect was not seen at 160 microg kg(-1). There were no differences in transfusion requirements across dose groups. There was no trend in the type or number of severe adverse events observed. Six thromboembolic events were observed in the active treatment groups: three during, and three following the 96-h observation period.

CONCLUSIONS

Despite no overall effect of rFVIIa treatment on primary endpoint, post hoc analysis showed an improvement in the control of bleeding for 80 microg kg(-1) rFVIIa vs. standard hemostatic treatment. The heterogeneity of the population may have contributed to the lack of an increasing effect with increased dose. Further trials should focus upon identifying the patient populations that may benefit from treatment with rFVIIa.

A study of the pharmacokinetics and safety of recombinant activated factor VII in healthy Caucasian and Japanese subjects

In this randomized, placebo-controlled, double-blind, single-centre, dose escalation study, we report the first evaluation of the pharmacokinetics and safety of recombinant activated factor VII (rFVIIa) in healthy Caucasian and Japanese subjects. Thirty-two healthy subjects were stratified according to sex and ethnic group to receive single bolus intravenous injections of three different doses of rFVIIa (40, 80, 160 microg/kg rFVIIa) or placebo, each separated by a 7-day wash-out period. Blood samples were taken up to 24 h after dosing. The factor VII clotting activity appeared to be dose dependent, but independent of sex and ethnic group. Statistical analyses demonstrated no significant effect of dose, sex or ethnicity on the dose-normalized mean area under the plasma concentration-time curve AUC0-t, indicating dose proportionality. No serious adverse events or thromboembolic events were reported. Analyses of coagulation parameters did not suggest induction of systemic coagulation when dosing rFVIIa up to 160 microg/kg. In conclusion, the pharmacokinetics of rFVIIa in Caucasian and Japanese subjects are similar, and no safety issues were identified.

"Off-license" use of recombinant activated factor VII

Recombinant factor VIIa (rFVIIa) has been widely used in the treatment of bleeding episodes in haemophiliac patients with inhibitors. In haemostatic circles it has also been assessed in reversing oral anticoagulant therapy. Over the last few years, it has been used "off-label" in patients with uncontrolled bleeding due to haemostatic abnormalities due to trauma and/or massive blood loss, thrombocytopenia, platelet dysfunction or liver dysfunction. This review examines the proposed mechanism of action of rFVIIa in the context of current concepts of haemostasis and its pharmacological properties. The "off-license" use of rFVIIa is reviewed. The latter are reported mainly as case reports, case series. There is an overwhelming need for randomized controlled trials to assess rFVIIa's efficacy, dosing and safety in current "off-license" use.

Intestinal surgery with activated recombinant factor VII prophylaxis in patients with haemophilia A and high responding inhibitors

Five patients with severe haemophilia A and high responding inhibitors underwent laparoscopic or open surgery on the digestive tract (appendicectomy, cholecystectomy, partial colectomy, or haemorrhoidectomy) with recombinant activated factor VII (rFVIIa) prophylaxis. rFVIIa was administered at a dose of 92-127 mug/kg prior to surgery and then every 2 h for 18-56 h before increasing the dosing interval. One patient was switched to a continuous infusion after 48 h of rFVIIa boluses. rFVIIa treatment lasted between 5 and 14 days in four patients, with good or excellent efficacy (total dose, 3.13-9.28 mg/kg). The fifth patient, who underwent surgery for prolapsed haemorrhoids, bled on day 6 and day 10 after the procedure, despite a satisfactory prothrombin time and factor VII coagulant level. The rFVIIa dose regimen was increased after the second bleeding episode, then the bleeding rapidly ceased after this modification to the treatment regimen. The total dose of rFVIIa used was 12.65 mg/kg, and treatment lasted 17 days. Antifibrinolytic treatment was used concomitantly in all five patients. Clinical and biological tolerability was excellent, and no increase in the anti-factor VIII inhibitor titre was observed. These results suggest that rFVIIa prophylaxis is effective in haemophilia A patients with factor VIII inhibitors who are undergoing elective or emergency intestinal surgery. Further studies are required to optimize the dose regimen and treatment period according to the surgical indication and technique.

Pharmacokinetics of activated recombinant coagulation factor VII (NovoSevenR) in children vs. adults with haemophilia A

To establish the pharmacokinetic profile of activated recombinant coagulation factor VII (rFVIIa; NovoSeven in children with haemophilia A, and to compare it with the pharmacokinetic profile in adults with haemophilia A. Twelve children (2-12 years) received one single dose of rFVIIa 90 and 180 micrograms kg(-1) in randomized order separated by a washout period of 48 h to 1 month. Six adults (18-55 years) received a single dose of rFVIIa 90 micrograms kg(-1). The pharmacokinetic analyses were based on a non-compartmental method. In children, the plasma level of FVII increased proportionally with the dose. The total body clearance normalized for body weight was significantly faster in children than in adults (FVII:C, 58 vs. 39 mL kg(-1) h(-1) and FVIIa, 78 vs. 53 mL kg(-1) h(-1), P < 0.05). A trend towards a larger volume of distribution at steady-state in children than in adults was observed (P > 0.05). Dose proportionality was established for plasma concentrations of FVII in children with haemophilia A at the dose levels investigated (90 and 180 micrograms kg(-1) rFVIIa). Following administration of rFVIIa 90 micrograms kg(-1), significantly faster clearance was observed in children compared with adults, suggesting that higher doses of rFVIIa may be needed to achieve the same plasma levels as in adults.

The use of recombinant activated factor VII for controlling life-threatening bleeding in Dengue Shock Syndrome

To report the use of recombinant activated factor VII (rFVIIa) in controlling life-threatening bleeding episodes in patients with grades III and IV Dengue Hemorrhagic Fever (DHF), also known as Dengue Shock Syndrome. Fifteen patients (seven boys, eight girls), whose median age was 8 years, were enrolled in the study. They were divided into two groups. Group 1 included nine patients, mainly grade III, waiting for platelet concentrate, and group 2 included six patients, mainly grade IV, who had already received platelet concentrate with unresponsiveness. A single dose or repeated doses of 100 microg/kg rFVIIa was/were given at intervals of 4 h according to the bleeding symptoms. The median times from the onset of bleeding to rFVIIa initiation were 6.5 and 29.8 h in groups 1 and 2, respectively. Each patient received one to three doses. An effective response was found in eight patients (53.3%), including six patients in group 1 and two patients in group 2. They had complete cessation of bleeding without recurrence for 48 h. An ineffective response was found in seven patients (46.7%) including three patients in group 1 and four patients in group 2 for which the bleeding recurred (n = 2), temporarily slowed down (n = 3), continued (n = 1) or occurred at a new site (n = 1). These included three patients in profound shock 24-48 h before referral to comprehensive treatment centers, two patients receiving ibuprofen before hospitalization, one patient with extensive volume overloading, and one patient requiring surgical intervention to ligate the torn intercostal artery and vein. The platelet concentrate was promptly transfused to stop bleeding in patients with ineffective responses. The results revealed that the earlier initiation of rFVIIa in the mainly grade III DHF in group 1 yielded a higher effective response (66.7%) than the delayed initiation in the mainly grade IV DHF in group 2 (33.3%). Moreover, patients previously receiving ibuprofen or volume expander of low molecular weight dextran or urea-linked gelatin tended to have lower effective responses (28.6%) than patients without associated medication (75.0%). Ultimately, three of six patients with grade IV DHF died, while all nine patients with grade III DHF survived. Thus, the case-fatality rate in this study was 20%. No clinical evidence of thromboembolic complications was observed. rFVIIa seems to be effective in restoring hemostasis in a limited series of patients with Dengue Shock Syndrome exhibiting life-threatening bleeding episodes. Further study is warranted.

Recombinant activated factor VII in cardiac surgery

Adult cardiac surgery has an incidence of 1-1.25 million procedures per year. Overall costs are in the range of 50 billion US dollars per year and are increasing. Included in these costs is an increasing burden from the use of blood and blood products. The central haemostatic problems associated with cardiac surgery are impaired platelet function associated with pre-operative medication and cardiopulmonary bypass, consumption of platelets, dilution of coagulation proteins and triggering of fibrinolysis. Anecdotal data suggest that recombinant activated factor VII (rFVIIa) has a possible role in cardiac surgery, but randomized, controlled trials are required to confirm this potential. We have undertaken a prospective, randomized, placebo-controlled trial in adult cardiac surgery with a high risk of serious haemorrhage. Drug (rFVIIa) or placebo is given after cardiopulmonary bypass and following the administration of protamine. The primary endpoints of the study are use of blood and blood products. Secondary endpoints are blood loss, length of stay in the intensive care unit and in the hospital, and survival. This study will give us further information on the potential efficacy and safety of rFVIIa in cardiac surgery.

Factor XI deficiency

Factor XI (FXI) deficiency leads to an injury-related bleeding diathesis, which is notable for the variability in the bleeding tendency and the lack of a clear relationship between bleeding and FXI coagulant activity. Bleeding in this disorder occurs especially in areas of high fibrinolytic activity. Although a rare disorder, the frequency of FXI deficiency is high in certain populations, notably persons of Ashkenazi descent and the Basque population of Southern France. In these populations, five mutations of the FXI gene have been identified and a founder effect has been confirmed for three of these. This paper reviews the role of FXI in coagulation and documents factors known to modify the bleeding tendency. Treatment of surgical bleeding in patients with FXI deficiency is reviewed with emphasis on the combined use of recombinant activated factor VII (rFVIIa; NovoSeven(R), Novo Nordisk, Bagsvaerd, Denmark) and the antifibrinolytic agent, tranexamic acid.

Improved hemostasis with superactive analogs of factor VIIa in a mouse model of hemophilia A

It is currently debated whether the mechanism of action of therapeutic doses of recombinant factor VIIa (rFVIIa, Novo-Seven) relies on the tissue factor (TF)-independent activity of the enzyme. The present study was conducted to investigate the in vivo hemostatic effects of rFVIIa and 3 analogs thereof with superior intrinsic activity (FVIIaIIa, K337A-FVIIaIia, and M298Q-FVIIa) in mice with antibody-induced hemophilia A. A highly significant dose response was observed for the bleeding time and blood loss for each of the rFVIIa variants. The bleeding time and blood loss were normalized after administration of 10 mg/kg rFVIIa, 3 mg/kg K337A-FVIIaIia, and 3 mg/kg M298Q-FVIIa, indicating a potency of these FVIIa analogs 3-4 times above that of rFVIIa in FVIII-depleted mice. The different in vivo potencies of the various forms of FVIIa could not be explained by the pharmacokinetics. Histopathological evaluation of kidneys revealed no signs of treatment-related pathological changes even after treatment with the superactive variants. The fact that FVIIa analogs with enhanced intrinsic activity are more efficacious in the murine hemophilia A model strongly suggests that the TF-independent procoagulant activity of FVIIa contributes to its clinical hemostatic effect.

The evidence behind inhibitor treatment with recombinant factor VIIa

Over the past 10 years considerable use has been made of recombinant factor VIIa (rFVIIa) for the treatment of patients with inhibitors to coagulation factors. During this time, its place in the management of acute bleeds and surgery has become better defined. Although pharmacokinetic studies report the half-life of rFVIIa as 2.7 h, there is considerable intersubject variability. Moreover, rFVIIa is cleared more rapidly in children than in adults. Assays for the measurement of rFVIIa plasma levels are not readily available in clinical diagnostic laboratories, although there is evidence that plasma FVII:C levels, measured by a one-stage prothombin-based assay, reflect the plasma concentration of rFVIIa:C. The level of FVII:C required to achieve haemostasis in different clinical circumstances remains uncertain. In order to overcome the logistic difficulties of repeated frequent bolus injections, and potentially to minimise usage, administration of rFVIIa by continuous infusion has been reported. However, there is some uncertainty as to whether continuous infusion of rFVIIa has similar therapeutic efficacy to an equivalent total dose administered by bolus injections. The extensive clinical experience with rFVIIa in haemophilic patients with inhibitors has been recorded in descriptive accounts of the Compassionate Use Programme and the Emergency Use Study. On the basis of the apparent clinical efficacy and safety reported in these studies, prospective randomised trials of different dose regimens have been undertaken for the treatment of acute bleeds and surgery. These have helped to define the minimum dose needed to achieve haemostasis. There remains considerable uncertainty about the minimal effective dose and appropriate duration of therapy in different clinical circumstances. There is therefore a need for the development of evidence-based guidelines for the use of rFVIIa in bolus and continuous infusion regimens in different settings, and for the therapeutic value of measuring plasma concentrations of rFVIIa, to facilitate the optimal use of this product. Furthermore, additional randomised clinical trials will help ensure that rFVIIa is used in the most clinically and cost effective way.

Long-lasting antithrombotic effects of a single dose of human recombinant, active site-blocked factor VII: insights into possible mechanism(s) of action

Tissue factor (TF) is important in initiating intravascular thrombosis. We demonstrated that active-site blocked factor VII (FVIIai) inhibits intravascular thrombosis for at least 6 h following a single injection, despite FVIIai plasma half-life was approximately 45 min. The aims of the present study were: (a) to determine the duration of the antithrombotic effects of a single injection of FVIIai; and (b) to assess whether FVIIai prolonged effects can be explained by a slow dissociation rate from TF in the arterial wall. Cyclic flow variations (CFVs), obtained in stenotic rabbit carotid arteries with endothelial injury, were abolished by either FVIIai (100 micro g kg-1 min-1 for 10 min) or hirudin (1 mg kg-1). After CFVs were abolished, carotid blood flow velocity was recorded continuously for 24 h. CFVs restored in all hirudin-treated animals after 2.1 +/- 0.3 h, while they restored in only four of nine FVIIai-treated rabbits in 10.1 +/- 2.2 h. Five animals in this group did not show restoration of CFVs up to 24 h. Immunohistochemistry revealed that FVIIai was still bound to the arterial wall 24 h following its administration, despite at this time FVIIai plasma levels were undetectable. Prothrombin time and partial thromboplastin time did not change significantly. FVIIai exerts potent, long-lasting antithrombotic effects without affecting systemic hemostatic parameters; a possible mechanism is a slow dissociation rate of FVIIai from TF. These proprieties make FVIIai particularly attractive as an antithrombotic intervention.

A prospective study of recombinant activated factor VII administered by continuous infusion to inhibitor patients undergoing elective major orthopaedic surgery: a pharmacokinetic and efficacy evaluation

After surgery in haemophilia, haemostasis is difficult to maintain in the presence of an antifactor VIII antibody. This study assessed the pharmacokinetics of recombinant activated factor VII (rFVIIa) and its efficacy in securing post-operative haemostasis in haemophiliacs with inhibitors. Continuous infusion of rFVIIa was evaluated for elective major orthopaedic surgery in nine patients with neutralizing antibodies to FVIII and at high risk of bleeding. After an initial preoperative bolus of 90 micro g/kg, rFVIIa was infused at a fixed rate of 50 micro g/kg/h for a median of 20 d (range 7-20 d). The median plasma FVII coagulant activity (FVII:C) at 24 h, 72 h and 20 d after surgery was 38 IU/ml (range 22-169 IU/ml), 45 IU/ml (range 17-88 IU/ml) and 31 IU/ml (range 27-46 IU/ml) respectively. The median plasma FVIIa:C at the same time points was 51 (range 24-211), 63 (range 22-99) and 44 (range 28-76) IU/ml respectively. Median total rFVIIa clearance remained stable during the rFVIIa continuous infusion period and was 40 (range 9-70), 34 (range 17-86) and 48 (range 32-55)ml/kg/h at the end of 24 h, 72 h and 20 d infusion respectively. Post-operatively, there were bleeds in six patients, which settled readily after a single bolus of rFVIIa (60 micro g/kg). There was a good clinical outcome for all patients. These data indicate that rFVIIa infusion at 50 micro g/kg/h achieves continuous plasma FVII procoagulant activity in excess of 30 IU/ml (12-15 nmol/l) and provides adequate haemostatic control for inhibitor patients during major orthopaedic surgery.

Inhibitor treatment: state of the art

The treatment of hemophilic patients with inhibitors presents many challenges. Recombinant activated factor VII (rFVIIa; NovoSeven, Novo Nordisk, Copenhagen, Denmark) is a new therapeutic option for this patient population. Optimization of dosing regimens may be achieved by considering (1) individual pharmacokinetics (especially in the pediatric population); (2) high-dose bolus regimens; (3) continuous infusion (CI) including high-dose CI; (4) early treatment with NovoSeven in the course of a bleeding event; and (5) use of NovoSeven as a prophylactic therapy. The literature involving these issues is reviewed here. Institution of early therapy has been shown to decrease total NovoSeven requirement while increasing efficacy. Pediatric patients may require a higher dose of NovoSeven due to the higher clearance rate and shorter half-life demonstrated by this population. Therefore, the patient's age and/or individual pharmacokinetics and clearance rate should be considered when calculating doses and CI rates. High-dose NovoSeven has been shown to be effective in some patient populations without increased reported adverse events. Despite its short half-life, prophylactic use of NovoSeven has been reported in a small number of patients, with an apparent decrease in bleeding episodes experienced. There has been significant interest in administration of NovoSeven by CI, particularly in patients requiring prolonged treatment, and it has been shown to be successful, although the optimal target factor VII activity has yet to be established and some authors have recommended the use of concomitant antifibrinolytics.

Perioperative pharmacokinetics of factor VII concentrate during liver surgery in a patient with congenital factor VII deficiency: an individual mathematical model

A patient with congenital factor VII deficiency (baseline activity, 7%) underwent surgery for hepatocellular carcinoma. No literature reference was found concerning the management of this coagulation defect in patients requiring liver surgery. We report one such case, with special reference to the peri-operative management of factor VII replacement therapy and the pharmacokinetic behavior of factor VII. As a result of accidental suprahepatic vein lesion, a bleeding episode occurred. This was associated with an increase in factor VII clearance and volume of distribution values from 1.30 to 3.85 l/h, and from 6.51 to 13.2 l, respectively. After surgery, the patient continued to receive the concentrate every 8 h during the first nine post-operative days. No post-operative bleeding or thrombotic event was observed. The patient was discharged in good condition.

Inhibitor treatment: state of the art

The treatment of hemophilic patients with inhibitors presents many challenges. Recombinant activated factor VII (rFVIIa; NovoSeven, Novo Nordisk, Copenhagen, Denmark) is a new therapeutic option for this patient population. Optimization of dosing regimens may be achieved by considering (1) individual pharmacokinetics (especially in the pediatric population); (2) high-dose bolus regimens; (3) continuous infusion (CI) including high-dose CI; (4) early treatment with NovoSeven in the course of a bleeding event; and (5) use of NovoSeven as a prophylactic therapy. The literature involving these issues is reviewed here. Institution of early therapy has been shown to decrease total NovoSeven requirement while increasing efficacy. Pediatric patients may require a higher dose of NovoSeven due to the higher clearance rate and shorter half-life demonstrated by this population. Therefore, the patient's age and/or individual pharmacokinetics and clearance rate should be considered when calculating doses and CI rates. High-dose NovoSeven has been shown to be effective in some patient populations without increased reported adverse events. Despite its short half-life, prophylactic use of NovoSeven has been reported in a small number of patients, with an apparent decrease in bleeding episodes experienced. There has been significant interest in administration of NovoSeven by CI, particularly in patients requiring prolonged treatment, and it has been shown to be successful, although the optimal target factor VII activity has yet to be established and some authors have recommended the use of concomitant antifibrinolytics.

Pharmacokinetic evaluation of recombinant, activated factor VII in patients with inherited factor VII deficiency

BACKGROUND AND OBJECTIVES

Recombinant factor VIIa (rFVIIa) has been widely used in the treatment of bleedings occurring in hemophiliacs with inhibitors. Very few reports exist on the use of rFVIIa in patients with inherited FVII deficiency. Pharmacokinetic studies on rFVIIa have been performed exclusively in hemophiliacs, patients with cirrhosis or volunteers pretreated with acenocoumarol. The aim of this study was to evaluate the kinetics of rFVIIa in patients naturally deficient of FVII.

DESIGN AND METHODS

A single dose kinetic study with rFVIIa was performed in 5 patients affected by severe congenital deficiency of factor VII in order to evaluate the true kinetic parameters of rFVIIa without the interference of FVII. Two dosages, 15 and 30 microg/kg, were used in a crossover schedule. FVII:C and FVIIa concentration/time curves were analyzed by a model-independent method. Antithrombin (AT), prothombin fragment 1+2 (F1+2) and tissue factor pathway inhibitor (TFPI) were assayed.

RESULTS

No differences emerged between the dosages with respect to dose-independent parameters [total body clearance (CL), volume of distribution area (VdArea), mean residence time (MRT)]. No significant changes of AT, TFPI, and F1+2 were observed. Comparing the results with those of other studies performed in adult hemophiliacs, in patients affected by cirrhosis or in volunteers on oral anticoagulant therapy (OAT), CL and VdArea of rFVIIa were definitely higher and in vivo recovery was lower.

INTERPRETATION AND CONCLUSIONS

These findings suggest that the kinetics of rFVIIa are not dose-dependent. In the absence of FVII, the changes of VdArea and CL may be in agreement with a mechanism of competition between FVII and rFVIIa for tissue factor binding.

Pharmacokinetics of recombinant activated factor VII (rFVIIa)

Recombinant coagulation factor VIIa (NovoSeven, Novo Nordisk Pharmaceuticals, Inc., Princeton NJ, USA) is a new drug for treatment of bleeding in patients with hemophilia and inhibitors. The pharmacokinetic profiles of rFVIIa have been evaluated in healthy adult volunteers who were pretreated with acenocoumarol, in adult and pediatric patients with hemophilia A or B, and in adult patients with cirrhosis and a prolonged prothrombin time (PT). The clearance (CL) and half-life (t1/2) values of rFVIIa after bolus injection were in the same range in the adult populations studied: patients with hemophilia, patients with cirrhosis, and healthy volunteers. The volume of distribution at steady state (Vss), on the other hand, was slightly smaller in healthy adult volunteers than in patients with hemophilia. The pharmacokinetic profile of rFVIIa seems to be independent of bleeding or nonbleeding conditions in adult hemophilic patients; however, the patients in these studies did not suffer from major bleeding episodes. The values of CL and t1/2 were also dose independent in adult patients with hemophilia and in patients with cirrhosis. Pediatric patients with hemophilia had shorter t1/2 and higher CL values than the adults with hemophilia. The administration of rFVIIa by continuous infusion is still experimental and a number of practical issues remain to be resolved.

Distribution of the recombinant coagulation factor 125I-rFVIIa in rats

Recombinant human factor VIIa (rFVIIa; NovoSeven) is a two-chain activated clotting factor that is used in the treatment of haemophilia. The distribution of radioactivity in male and pregnant and non-pregnant female rats has been examined by whole-body autoradiography (WBA) after single intravenous doses of 125I-radiolabelled rFVIIa at a dosage level of ca. 0.1 mg/kg. Concentrations of radioactivity were highest in the blood and the highly perfused major thoracic and visceral organs and gonads. This distribution of radioactivity was generally similar in pregnant and non-pregnant females, and although radioactivity was concentrated in the foetal thyroid, it was present in other foetal tissues only at trace levels. Radioactivity in thyroid, urinary bladder and gastrointestinal tract of all rats was apparently associated with detached 125I-iodide. At early sacrifice times (up to 2 h), radioactivity was present in the bone marrow, but at later times (6-24 h) it was apparently associated with the mineralised bone structures. The quantitative distribution of total and trichloroacetic acid precipitable radioactivity in the tissues of rats also was studied after single intravenous doses of 125I-rFVIIa and 125I-rFVII, the non-activated single chain precursor of FVIIa, which is normally present in the circulation. These studies confirmed the WBA findings and showed that the tissue distribution of 125I-rFVII and 125I-rFVIIa was similar, indicating that the distribution of rFVIIa during therapy would be similar to that produced from endogenous FVII as a physiological response to vascular injury.