The use of recombinant activated factor VII in platelet disorders: a critical review of the literature

Recombinant activated factor VII in a patient with intracranial hemorrhage and severe thrombocytopenia

Hemorrhage in patients with hematologic malignancies is often difficult to manage as many of these patients also have coagulopathy and thrombocytopenia of varying severity. Recombinant factor VIIa is a FDA-approved agent for management of bleeding in hemophilia patients with inhibitors. Use of recombinant FVIIa has also been used as a last resort in various clinical settings such as trauma, alveolar hemorrhage, gastrointestinal bleeding, and intracranial hemorrhage for control of bleeding with variable outcomes. This paper presents a case of recombinant FVIIa administration in a patient with multiple myeloma and profound transfusion refractory thrombocytopenia suffering from traumatic subdural hematoma.

Learning the Ropes of Platelet Count Regulation: Inherited Thrombocytopenias

Inherited thrombocytopenias (IT) are a group of hereditary disorders characterized by a reduced platelet count sometimes associated with abnormal platelet function, which can lead to bleeding but also to syndromic manifestations and predispositions to other disorders. Currently at least 41 disorders caused by mutations in 42 different genes have been described. The pathogenic mechanisms of many forms of IT have been identified as well as the gene variants implicated in megakaryocyte maturation or platelet formation and clearance, while for several of them the pathogenic mechanism is still unknown. A range of therapeutic approaches are now available to improve survival and quality of life of patients with IT; it is thus important to recognize an IT and establish a precise diagnosis. ITs may be difficult to diagnose and an initial accurate clinical evaluation is mandatory. A combination of clinical and traditional laboratory approaches together with advanced sequencing techniques provide the highest rate of diagnostic success. Despite advancement in the diagnosis of IT, around 50% of patients still do not receive a diagnosis, therefore further research in the field of ITs is warranted to further improve patient care.

Therapeutic doses of recombinant factor VIIa in hemophilia generates thrombin in platelet-dependent and -independent mechanisms

BACKGROUND

In hemophilia bypass therapy, a platelet-dependent mechanism is believed to be primarily responsible for recombinant factor VIIa (rFVIIa)'s hemostatic effect. rFVIIa may also possibly interact with other cells through its binding to endothelial cell protein C receptor (EPCR) or cell surface phospholipids.

OBJECTIVES

We aim to investigate the relative contribution of platelet-dependent and platelet-independent mechanisms in rFVIIa-mediated thrombin generation in hemophilic conditions at the injury site.

METHODS

Platelets were depleted in acquired and genetic hemophilia mice using anti-platelet antibodies. The mice were subjected to the saphenous vein injury, and the hemostatic effect of pharmacological concentrations of rFVIIa was evaluated by measuring thrombin generation at the injury site.

RESULTS

Administration of anti-mouse CD42 antibodies to mice depleted platelets by more than 95%. As expected, hemophilia mice, compared with wild-type mice, generated only a small fraction of thrombin at the injury site. The depletion of platelets in hemophilia mice further reduced thrombin generation. However, when pharmacological doses of rFVIIa were administered to hemophilia mice, substantial amounts of thrombin were generated even in the platelet-depleted hemophilia mice. No differences in thrombin generation were detected among FVIII-/- , EPCR-deficient FVIII-/- , and EPCR-overexpressing FVIII-/- mice depleted of platelets or not. Evaluation of platelets by flow cytometry as well as immunoblot analysis showed no detectable expression of EPCR.

CONCLUSIONS

Our data suggest that pharmacological concentrations of rFVIIa generate thrombin in hemophilia in both platelet-dependent and platelet-independent mechanisms.

Factor VIIa administration in traumatic brain injury: an AAST-MITC propensity score analysis

BACKGROUND

Recombinant factor VIIa (rFVIIa) has been used off-label as an adjunct in the reversal of warfarin therapy and management of hemorrhage after trauma. Only a handful of these reports are rigorous studies, from which results regarding safety and effectiveness have been mixed. There remains no clear consensus as to the role of rFVIIa in traumatic brain injury (TBI).

METHODS

Eleven level 1 trauma centers provided clinical data and head CT scans of patients with a Glasgow Coma Scale (GCS) score of ≤13 and radiographic evidence of TBI. A propensity score (PS) to receive rFVIIa in those surviving ≥2 days was calculated for each patient based on patient demographics, comorbidities, physiology, Injury Severity Score, admission GCS score, and treatment center. Patients receiving rFVIIa within 24 hours of admission were matched to patients who did not receive rFVIIa for outcomes assessment. Subgroup analysis evaluated patients with primary head injury with PS matching.

RESULTS

There were 4284 patient observations; 129 received rFVIIa. Groups were comparable after matching. No differences in mortality or morbidity were found. Improvement in GCS score from admission to discharge was less among those receiving rFVIIa (5.5 vs. 2.4; P value 0.001); however, there was no difference in average GCS score at discharge. No significant differences in outcomes were identified in patients with isolated TBI receiving rFVIIa.

DISCUSSION

rFVIIa in early management of TBI is not associated with a decreased risk of mortality or morbidity, and may negatively impact recovery and functional status at discharge in the severely injured patient with polytrauma.

LEVEL OF EVIDENCE

Level III.

STUDY TYPE

Therapeutic/care management.

Evidence supporting the use of recombinant activated factor VII in congenital bleeding disorders

BACKGROUND

Recombinant activated factor VII (rFVIIa, NovoSeven) was introduced in 1996 for the treatment of hemophilic patients with antibodies against coagulation factor VIII or IX.

OBJECTIVE

To review the evidence supporting the use of rFVIIa for the treatment of patients with congenital bleeding disorders.

PATIENTS AND METHODS

English-language databases were searched in September 2009 for reports of randomized controlled trials (RCTs) evaluating the ability of rFVIIa to restore hemostasis in patients with congenital bleeding disorders.

RESULTS

Eight RCTs involving 256 hemophilic patients with antibodies against coagulation factors, also known as inhibitors, were identified. The evidence supporting the use of rFVIIa in these patients was weak with regard to dose, clinical setting, mode of administration, efficacy, and adverse events, given the limited sample size of each RCT and the heterogeneity of the studies.

CONCLUSION

The authors suggest that rFVIIa therapy in hemophilic patients with inhibitors should be based on the individual's ability to generate thrombin and form a clot, and not on the patient's weight alone. Therefore, assays for thrombin generation, such as whole-blood thromboelastography, have the potential to significantly improve the treatment of these patients.