A factor VIIIa-mimetic bispecific antibody, Mim8, ameliorates bleeding upon severe vascular challenge in hemophilia A mice.

Hemophilia A is a bleeding disorder resulting from deficient factor VIII (FVIII), which normally functions as a cofactor to activated factor IX (FIXa) that facilitates activation of factor X (FX). To mimic this property in a bispecific antibody format, a screening was conducted to identify functional pairs of anti-FIXa and anti-FX antibodies, followed by optimization of functional and biophysical properties. The resulting bispecific antibody (Mim8) assembled efficiently with FIXa and FX on membranes, and supported activation with an apparent equilibrium dissociation constant of 16 nM. Binding affinity with FIXa and FX in solution was much lower, with equilibrium dissociation constant values for FIXa and FX of 2.3 and 1.5 µM, respectively. In addition, the activity of Mim8 was dependent on stimulatory activity contributed by the anti-FIXa arm, which enhanced the proteolytic activity of FIXa by 4 orders of magnitude. In hemophilia A plasma and whole blood, Mim8 normalized thrombin generation and clot formation, with potencies 13 and 18 times higher than a sequence-identical analogue of emicizumab. A similar potency difference was observed in a tail vein transection model in hemophilia A mice, whereas reduction of bleeding in a severe tail-clip model was observed only for Mim8. Furthermore, the pharmacokinetic parameters of Mim8 were investigated and a half-life of 14 days shown in cynomolgus monkeys. In conclusion, Mim8 is an activated FVIII mimetic with a potent and efficacious hemostatic effect based on preclinical data.

Recombinant FXIII (rFXIII-A2) Prophylaxis Prevents Bleeding and Allows for Surgery in Patients with Congenital FXIII A-Subunit Deficiency.

Recombinant factor XIII-A2 (rFXIII-A2) was developed for prophylaxis and treatment of bleeds in patients with congenital FXIII A-subunit deficiency. mentor™2 (NCT00978380), a multinational, open-label, single-arm, multiple-dosing extension to the pivotal mentor™1 trial, assessed long-term safety and efficacy of rFXIII-A2 prophylaxis in eligible patients (patients with severe [<0.05 IU/mL] congenital FXIII subunit A deficiency) aged ≥6 years. Patients received 35 IU/kg rFXIII-A2 (exact dosing) every 28 ± 2 days for ≥52 weeks. Primary endpoint was safety (adverse events including immunogenicity); secondary endpoints were rate of bleeds requiring FXIII treatment, haemostatic response after one 35 IU/kg rFXIII-A2 dose for breakthrough bleeds and withdrawals due to lack of rFXIII-A2 efficacy. Steady-state pharmacokinetic variables were also summarized. Elective surgery was permitted during the treatment period. Sixty patients were exposed to rFXIII-A2; their median age was 26.0 years (range: 7.0-77.0). rFXIII-A2 was well tolerated without any safety concerns. No non-neutralizing or neutralizing antibodies (inhibitors) against FXIII were detected. Mean annualized bleeding rate (ABR) was 0.043/patient-year. Mean spontaneous ABR was 0.011/patient-year. No patients withdrew due to lack of efficacy. Geometric mean FXIII trough level was 0.17 IU/mL. Geometric terminal half-life was 13.7 days. rFXIII-A2 prophylaxis provided sufficient haemostatic coverage for 12 minor surgeries without the need for additional FXIII therapy; eight procedures were performed within 7 days of the patient's last scheduled rFXIII-A2 dose, and four were performed 10 to 21 days after the last dose.

Predicting the outcomes of using longer-acting prophylactic factor VIII to treat people with severe hemophilia A: a hypothetical decision analysis.

Essentials No randomized trials have compared long-acting factor VIII (FVIII) with currently used products. A comparison was undertaken using a decision model to predict FVIII use and number of bleeds. In the base case, longer acting FVIII reduced factor use by 17% while resulting in similar bleeds. The value of longer acting FVIII will be largely determined by existing regimens and unit price. Click to hear Prof. Makris's presentation on new treatments in hemophilia SUMMARY: Background Recently, factor VIII (FVIII) products with longer half-lives, such as recombinant FVIII Fc fusion protein (rFVIIIFc), have become available. Use of longer-acting FVIII products will largely depend on effectiveness and cost; no direct evaluations have compared these parameters between conventional and longer-acting FVIII therapies. Objectives To present a hypothetical decision analysis, combining evidence from multiple sources to estimate bleeding frequency, resource use and cost of longer-acting prophylactic products, such as rFVIIIFc, vs. conventional recombinant FVIII (rFVIII). Patients/Methods The decision model used published pharmacokinetic parameters, bleeding frequency vs. time information below a 1-IU dL-1 FVIII trough level, and adherence. Prophylactic treatment scenarios were modelled for a hypothetical patient with severe hemophilia A (<1 IU/dL) receiving rFVIIIFc or rFVIII. Results Infusing twice weekly with rFVIIIFc 42.7 IU kg-1 per dose required less clotting factor than infusing every 56 h with rFVIII 33.75 IU kg-1 per dose; annual bleeding rates were similar. Base case analysis suggested that total FVIII costs were equated when rFVIIIFc cost 1.18 times more per IU than rFVIII, assuming similar adherence. Other modelled scenarios produced similar results, although differences in FVIII consumption were particularly sensitive to assumptions regarding frequency and dose of the rFVIII and rFVIIIFc regimens. For example, decreasing rFVIII from 33.75 IU kg-1 to 30 IU kg-1 per dose decreased the price factor to 1.05. Conclusions Longer-acting FVIII products may reduce FVIII consumption and infusion frequency without compromising hemostatic effect; this should be considered along with other factors (e.g. adherence and underlying FVIII regimen) when evaluating a suitable price for these agents.

Recombinant B domain deleted porcine factor VIII for the treatment of bleeding episodes in adults with acquired hemophilia A.

Hemophilia A is an inherited deficiency of clotting factor VIII (FVIII) often complicated by inhibitor development (CHAWI) in which neutralizing antibodies block the therapeutic benefit of replacement therapy. Inhibitors to FVIII can also be seen in an auto-immune disease known as acquired hemophilia A (AHA). 'Bypassing' therapies have been shown to provide hemostasis but dosing must be done empirically because current assays cannot measure objective markers of treatment efficacy and safety. A recombinant porcine sequence factor VIII (r-pFVIII) has been developed for the management of AHA. Preclinical, Phase I and Phase II clinical research studies in CHAWI subjects showed therapeutic potential and safety of this agent. A Phase II/III study in AHA with serious bleeding episodes shows a positive response in all subjects after administration. Based on current preclinical and clinical trial data, r-pFVIII should become the first line of treatment in the management of hemorrhage in patients with AHA.

[Laboratory monitoring of efficiency of different approaches to the therapy of patients with inhibitor form of haemophilia A].

Revealing of inhibitors form of hemophilia A form patients of hemophilia in Republic of Uzbekistan was studied and peculiarities of this form of hemophilia also was studied. Shown, that revealing of inhibitors form from 405 patients of hemophilia A was 7,7%. Shown that from patients with inhibitors form more patients with low titr of inhibitors (77,1%). In patients with high titr of inhibitors in high degree was more heavy degree of hemophilia A, in patients with low titr of inhibitors more heavy form and heavy form of hemophilia A was in equal degree. Shown, that Cogenait drug and plasmapheresis in Pph-3 - Pph-5 regime render equal effect in reducing of inhibitor titr.

[Post-tonsillectomy haemorrhage treatment with activated factor VII]. / Ukontrollabel blødning efter tonsillektomi behandlet med aktiveret faktor VII.

Tonsillectomy is a common procedure in otorhinolaryngology and postoperative haemorrhage is a well-known complication. In this case, a 34 year-old male with obstructive sleep apnoea and no coagulation defects was operated; 30 minutes after the operation he presented with primary post operative haemorrhage and surgical haemostasis was not possible. After one hour of secondary surgery tranexamacid 1 g and phytomenadione 10 mg was given, but the diffuse bleeding continued until recombinant factor VIIa 96 mg/kg was administered.

[Long-term prophylaxis in congenital haemophilia with inhibitors - experiences with rFVIIa]. / Langzeitprophylaxe bei kongenitaler Hämophilie mit Hemmkörpern - Erfahrungen mit rFVIIa.

A major challenge in the treatment of haemophilia patients is the development of autoantibodies against factor VIII. These patients are at particular risk if spontaneous bleedings or traumata occur or if surgery is necessary. In case of an unsuccessful immune tolerance therapy with high i.v. doses of factor VIII, treatment with recombinant factor VIIa or activated prothrombin complex should be considered. This article summarises data of three patients with severe haemophila A due to an inversion of intron 22 in the FVIII gen. All three patients had autoantibodies against FVIII. The therapy of these patients with rFVIIIa was safe and effective. Furthermore a prophylactic therapy with rFVIIa (at an individual dose of 180-270 microg/kg body weight) reduced the number of spontaneous bleedings in joints and muscles as well as in other locations significantly. The reduced rate of spontaneous bleedings improved the mobility and the quality of life in the young patients studied.

Intrinsic stability and functional properties of disulfide bond-stabilized coagulation factor VIIIa variants.

BACKGROUND: The utility of purified coagulation factor (F)VIII for treatment of hemophilia A is limited in part by its instability following activation by thrombin, which is caused by spontaneous dissociation of the A2 domain from the activated FVIII (FVIIIa) heterotrimer. To prevent this A2 domain dissociation in FVIIIa, we previously engineered a cysteine pair (C664-C1826) in recombinant FVIII that formed a disulfide bond cross-linking the A2 domain in the heavy chain to the A3 domain in the light chain. This engineered disulfide bond resulted in a more stable FVIIIa. AIMS: Here, we characterize the functional parameters of C664-C1828 FVIII and of a new disulfide bond-stabilized FVIII (C662-C1828 FVIII). METHODS: In order to assess whether these FVIII variants might be good candidates for a new therapeutic agent to treat hemophilia A, we investigated a variety of functional parameters that might affect the in vivo properties of the variants, including half-life of disulfide bond-stabilized FVIII and FVIIIa and the potency of these FVIIIa molecules in the FXase complex. RESULTS: Both disulfide bond-stabilized variants had improved affinity for von Willebrand factor (VWF). In studies of FX activation by purified FIXa and FVIIIa, C662-C1828 FVIIIa had normal activity while C664-C1826 FVIIIa had reduced activity. Both C664-C1826 FVIIIa and C662-C1828 FVIIIa were inactivated by activated protein C (APC) but the rates of inactivation were different. CONCLUSION: Overall, the specific location of the disulfide bridge between the A2 and A3 domains appears to affect functional properties of FVIIIa. In summary, introduction of engineered interdomain disulfides results in FVIIIa variants that resist spontaneous loss of activity while retaining susceptibility to APC proteolytic inactivation and maintaining VWF binding.

Intracranial haemorrhage in a boy with severe haemophilia A and factor VIII inhibitor.

BACKGROUND: This report describes the case of a boy with severe haemophilia A and factor VIII inhibitor who suffered subarachnoid haemorrhage at age 7 years, followed by bleeding in the right cerebellar hemisphere and an epidural haematoma at age 12 years. METHOD: The patient received intensive replacement treatment leading to reversal of neurological signs and symptoms and resorption of haematomas, as demonstrated by CT scans.

Recombinant activated Factor VII in major surgery and trauma patients: a response.

The review article by Wilson et al. (Expert Opin. Drug Saf., 2005) on recombinant activated Factor VII (rFVIIa) offers some valuable insights into the ongoing exploration of this agent in the management of uncontrolled bleeding--an area of high unmet clinical need. This editorial highlights that the chosen citation of Riou et al. (Shock, 2004), in reference to two parallel studies conducted in trauma patients with blunt and penetrating injury, was both a report of an early analysis of the data, and was only one of several abstracts on these studies published in 2004. The authors of this editorial believe that the inclusion of the other published abstracts in this series would have provided a more comprehensive and balanced overview of recombinant activated Factor VII.

[A spontaneous haemarthros in a postpartal woman: a case of acquired haemophilia A]. / Een spontane gewrichtsbloeding bij een vrouw post partum: een geval van verworven hemofilie A.

A woman aged 35 years presented with a haemarthros of the left elbow 6 months after her first parturition due to acquired haemophilia A. The bleeding episodes were mild and treated with recombinant activated factor VII. Because of the mild bleeding tendency and the chance of spontaneous remission it was decided to withhold immunosuppressive treatment. During the course of one year, the factor VIII level and the activated partial thromboplastin time (APTT) normalized and the autoantibodies disappeared. Four years after her first parturition, she had an uncomplicated pregnancy and the postpartum period was uneventful. Up to fourteen months postpartum, there are no signs of recurrence of the acquired haemophilia A. Acquired haemophilia A post partum usually presents in the first 3 months post partum. Frequently presenting symptoms are haemorrhages post partum, menorrhagia, soft-tissue haemorrhages and haemorrhages during surgical procedures. As a rule, the haemorrhages are slight. The titers of blocking antibodies are low in comparison with the titers in congenital haemophilia A.

Coagulation blockade prevents sepsis-induced respiratory and renal failure in baboons.

Sepsis-induced tissue factor (TF) expression activates coagulation in the lung and leads to a procoagulant environment, which results in fibrin deposition and potentiates inflammation. We hypothesized that preventing initiation of coagulation at TF-Factor VIIa (FVIIa) complex would block fibrin deposition and control inflammation in sepsis, thereby limiting acute lung injury (ALI) and other organ damage in baboons. A model of ALI was used in which adult baboons were primed with killed Escherichia coli (1 x 10(9) CFU/kg), and bacteremic sepsis was induced 12 h later by infusion of live E. coli at 1 x 10(10) CFU/kg. Animals in the treatment group were given a competitive inhibitor of TF, site-inactivated FVIIa (FVIIai), intravenously at the time of the infusion of live bacteria and monitored physiologically for another 36 h. FVIIai dramatically protected gas exchange and lung compliance, prevented lung edema and pulmonary hypertension, and preserved renal function relative to vehicle (all p < 0.05). Treatment attenuated sepsis-induced fibrinogen depletion (p < 0.01) and decreased systemic proinflammatory cytokine responses, for example, interleukin 6 (p < 0.01). The protective effects of TF blockade in sepsis-induced ALI were confirmed by using tissue factor pathway inhibitor. The results show that TF-FVIIa complex contributes to organ injury in septic primates in part through selective stimulation of proinflammatory cytokine release and fibrin deposition.

Recombinant human factor VIIa in the management of amyloid-associated factor X deficiency.

Factor X deficiency is an important complication of amyloidosis. It is associated with severe bleeding that is difficult to control with plasma or prothrombin complex concentrates. Splenectomy ameliorates the factor X deficiency, but achieving satisfactory haemostasis for this operation is problematic. We report that a new clotting concentrate, recombinant factor VIIa, readily controls bleeding and makes splenectomy feasible.

In vivo studies of activated porcine factor VIII.

The haemostatic effectiveness of activated FVIII was compared to that of non-activated FVIII in a cross-over study in a canine model of haemophilia. Activation of FVIII in porcine concentrate was achieved by the addition of 3 x 10(-5) IU thrombin per ml of concentrate, which gave consistent increases in 1-stage FVIII activity of 13- to 14-fold and slow decay. The haemostatic effect was monitored by measurements of the cuticle bleeding time 10 and 45 min after infusion and there were no consistent differences between the activated and non-activated concentrates. One-stage factor VIII assays on plasmas 5 min after infusion showed identical mean values for activated and non-activated concentrates, indicating that most of the higher activity observed in vitro had disappeared rapidly from the circulation. These results suggest that controlled activation of FVIII by thrombin, which increases its activity in 1-stage assays, is unlikely to be of therapeutic benefit. For therapeutic concentrates which may contain small amounts of activated FVIII, the 1-stage assay may be an unreliable guide to their therapeutic effect.