Current opinion on inhibitor treatment options

Factor X inhibitor: a fulminant presentation and fatal course of a rare syndrome in a 59-year-old male

Factor X inhibitors are rare. The few cases documented in the literature have occurred after viral prodromes, in association with cancer, or after exposure to antibiotics. Acquired factor X deficiencies are also rare and their etiology is largely unknown. We report a new case of a factor X inhibitor and review prior cases of both factor X inhibitors and non-amyloidosis-related acquired factor X deficiencies.

Current difficulties and recent advances in bypass therapy for the management of hemophilia with inhibitors: a new and practical formulation of recombinant factor VIIa

Bypassing agents are the mainstay of treatment for patients with hemophilia with high-titer inhibitors. Whereas the availability of these agents has greatly advanced the management of bleeding episodes in this population, timely administration of bypassing agents continues to be hampered by a number of practical limitations, including the need for refrigerated storage of the agent and its reconstitution at room temperature prior to administration, among others. In this review, the importance of early treatment of bleeds and factors that influence this more timely therapeutic approach are highlighted, together with the advantages offered by the use of a new formulation of recombinant activated factor VII that permits improved storage and portability, potentially optimizing timely bypassing agent administration.

The use of PEGylated liposomes in the development of drug delivery applications for the treatment of hemophilia

Hemophilia A is a rare X-linked bleeding disorder caused by lack or dysfunction of coagulation factor VIII (FVIII). Hemophilia A is treated with replacement therapy, but frequent injections of the missing FVIII often lead to the formation of inhibitory antibodies. Patients who develop high levels of inhibitors must be treated with bypassing agents such as activated FVII (FVIIa). Both FVIII and FVIIa have short half-lives and require multiple injections. Long-acting forms of these proteins would therefore reduce the frequency of injections, improve patient compliance and reduce complications. In this article we present a new platform technology that produces long-acting forms of FVIII and FVIIa and improves the efficacy of hemophilia treatment. This technology is based on the binding of proteins/peptides to the outer surface of PEGylated liposomes (PEGLip). Binding is dependent on an amino acid consensus sequence within the proteins and is highly specific. At the same time, binding is non-covalent and does not require any modification of the therapeutic agent or its production process. Association of proteins with PEGLip results in substantial enhancements in their pharmacodynamic properties following administration. These improvements seem to arise from the association of formulated proteins with platelets prior to induction of coagulation.

A clinical cardiology perspective of thrombophilias

Thrombophilias, an inherited and/or acquired predisposition to vascular thrombosis beyond hemostatic needs are common in cardiovascular medicine and include systemic disorders such as coronary atherosclerosis, atrial fibrillation, exogenous obesity, metabolic syndrome, collagen vascular disease, human immunodeficiency virus, blood replacement therapy and several commonly used medications. A contemporary approach to patients with suspected thrombophilias, in addition to a very selective investigation for gain-of-function and loss-of-function gene mutations affecting thromboresistance, must consider prevalent diseases and management decisions encountered regularly by cardiologists in clinical practice. An appropriate recognition of common disease states as thrombophilias will also stimulate platforms for much needed scientific investigation.

Polyphosphate as a general procoagulant agent

BACKGROUND

Polyphosphate is secreted by activated platelets and we recently showed that it accelerates blood clotting, chiefly by triggering the contact pathway and promoting factor (F) V activation.

RESULTS

We now report that polyphosphate significantly shortened the clotting time of plasmas from patients with hemophilia A and B and that its procoagulant effect was additive to that of recombinant FVIIa. Polyphosphate also significantly shortened the clotting time of normal plasmas containing a variety of anticoagulant drugs, including unfractionated heparin, enoxaparin (a low molecular weight heparin), argatroban (a direct thrombin inhibitor) and rivaroxaban (a direct FXa inhibitor). Thromboelastography revealed that polyphosphate normalized the clotting dynamics of whole blood containing these anticoagulants, as indicated by changes in clot time, clot formation time, alpha angle, and maximum clot firmness. Experiments in which preformed FVa was added to plasma support the notion that polyphosphate antagonizes the anticoagulant effect of these drugs via accelerating FV activation. Polyphosphate also shortened the clotting times of plasmas from warfarin patients.

CONCLUSION

These results suggest that polyphosphate may have utility in reversing anticoagulation and in treating bleeding episodes in patients with hemophilia.

Cost and effectiveness of treatments for mild-to-moderate bleeding episodes in haemophilia patients with inhibitors in Korea

First-line treatment for mild-to-moderate bleeding episodes in patients with haemophilia and inhibitors in Korea is currently activated prothrombin complex concentrate (aPCC) with recombinant activated factor VII (rFVIIa) as second-line therapy or as a last resort. The aim of this study was to estimate the cost and effectiveness of aPCC vs. rFVIIa for treating mild-to-moderate bleeds in inhibitor patients from the Korean reimbursement authorities' perspective. Clinical outcomes and resource utilization data (number of doses, average dose, number of outpatient visits, inpatient stays, ambulance transport and concomitant medications) were collected from an observational study involving four Korean paediatric haemophilia centres. Cost-effectiveness was modelled using a decision analysis approach and sensitivity analyses undertaken. rFVIIa was a more effective haemostatic therapy (87.1% efficacy in bleed resolution) than aPCC (64.0%). rFVIIa effected more rapid haemostasis, resolving bleeding in a mean of 6.6 h vs. 25.2 h for aPCC. Fewer rFVIIa doses were required per bleed vs. aPCC (means 1.7 and 2.3). Mean total direct medical costs from bleed initiation to cessation were estimated at Korean Won (KRW)12 460 thousand (US$12 311) for rFVIIa given as first-line therapy and KRW18 304 thousand (US$18 085) for aPCC given as first-line therapy. Sensitivity analyses confirmed the cost-effectiveness of rFVIIa vs. aPCC given as first-line therapy. In Korea, use of rFVIIa as first-line therapy for treatment of mild-to-moderate bleeding episodes in inhibitor patients is both clinically effective and cost-effective compared with initial aPCC treatment. rFVIIa should be considered as the first-line treatment for mild-to-moderate bleeding episodes in patients with haemophilia and inhibitors in Korea.

Prothrombin complex concentrate (Beriplex P/N) in severe bleeding: experience in a large tertiary hospital

Introduction

Major blood loss can often be life-threatening and is most commonly encountered in the settings of surgery and trauma. Patients receiving anticoagulant therapy are also at increased risk of bleeding. We investigated the use of a prothrombin complex concentrate (PCC; Beriplex P/N, CSL Behring, Marburg, Germany) to treat severe bleeding in a variety of settings: cardiac surgery, warfarin therapy and other surgery.

Methods

Thirty consecutive patients who had received PCC were identified from blood transfusion records. For cardiac surgery and warfarin reversal, PCC was administered in accordance with hospital protocols. PCC was administered to cardiac and other surgical patients responding poorly to recognized blood products, whereas it was administered first-line to patients with life-threatening bleeds and requiring warfarin reversal, in accordance with British Committee for Standards in Haematology guidelines. We conducted a retrospective analysis of patient records in order to ascertain PCC dose, use of other blood products and response to PCC (clotting screen results before and after PCC administration, haemostasis achievement, and survival).

Results

Six patients (20%) were excluded because of inadequate documentation (n = 5) or acquired haemophilia (n = 1). Therefore, 24 patients were included in the analysis: coronary artery bypass graft (n = 5), mitral/aortic valve replacement (n = 2), other surgery (n = 9) and warfarin reversal (n = 8). Most patients (83.3%) received no more than 1500 IU of Beriplex P/N 500. Considerable reduction in administration of other blood products was seen during the 24 hours after PCC administration. Partial or complete haemostasis was achieved in 14 out of 18 cases (77.8%). In total, 12 out of 24 patients (50%) died during the study; two-thirds of the deaths were considered unrelated to bleeding. No thrombotic complications or adverse drug reactions were observed.

Conclusion

This study emphasizes the value of PCC in reversing the effects of oral anticoagulant therapy in bleeding patients. It also demonstrates the potential value of PCC in controlling bleeding in patients undergoing cardiac and other surgical procedures. The use of PCC in bleeding patients without hereditary or anticoagulation-related coagulopathy is novel, and further investigation is warranted. In the future, it may be possible to use PCC as a substitute for fresh frozen plasma in this setting; adequate documentation is crucial for all blood products.

Platelet-delivered factor VIII provides limited resistance to anti-factor VIII inhibitors

BACKGROUND

Gene therapy strategies directed at expressing factor (F)VIII in megakaryocytes has potential advantages in the treatment of hemophilia A. Among these is that platelet (p) FVIII may be effective in the presence of circulating anti-FVIII inhibitors.

OBJECTIVE

We examined in a murine transgenic model whether pFVIII could correct the coagulation defect in FVIII(null) mouse in the presence of circulating inhibitors.

METHODS

FVIII(null) mice that were transgenic for pFVIII (pFVIII/FVIII(null)) were compared with FVIII(null) mice receiving infused FVIII in a FeCl(3) carotid injury model in the presence of anti-FVIII inhibitors.

RESULTS

After injury, pFVIII/FVIII(null) mice were significantly more resistant to circulating inhibitors than after plasma FVIII correction in both an acute and chronic models of inhibitor exposure even although in the chronic model, significant amounts of inhibitor were stored within the platelets. Furthermore, bleeding in the pFVIII mice in the presence of inhibitors was not as a result of the development of thrombocytopenia.

CONCLUSION

In FVIII(null) mice, pFVIII provides improved, but limited, protection in the presence of inhibitors of approximately 6-fold greater Bethesda Units per mL relative to infused FVIII. Our findings differ from a recent report using a tail-clip exsanguination assay on the degree of efficacy of pFVIII in the presence of inhibitors. We propose that this difference in outcome is as a result of the sensitivity of the tail-vein exsanguination model to low levels of pFVIII.

Evidence-based use of recombinant FVIIa (NovoSeven, NiaStase) for the treatment of hemophilia with inhibitors in children and adolescents

Children and adolescents comprise a significant proportion of the hemophilia population, including those patients who have developed inhibitors to factor VIII or FIX. We examine the use of rFVIIa for the treatment of bleeding episodes and the prevention of bleeding in children and adolescents with hemophilia A and B with inhibitors, focusing on registry data and recent clinical trial results. Based on this review of the literature, we conclude that recombinant FVIIa is safe and effective for use in controlling bleeding in these patient populations.