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Inhibitory Antibodies (inhibitory + antibody)
Selected AbstractsComparative immunogenicity of recombinant B domain-deleted porcine factor VIII and Hyate:C in hemophilia A mice presensitized to human factor VIIIJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 4 2004E. T. Parker Summary., Hyate is a commercial plasma-derived porcine factor (F)VIII concentrate that is used in the treatment of patients with inhibitory antibodies to FVIII. OBI-1 is a recombinant B domain-deleted form of porcine FVIII that is in clinical development for the same indication. Hemophilia A mice were presensitized with human FVIII to simulate clinical inhibitory antibody formation and then were randomized to receive OBI-1 or Hyate:C in a comparative immunogenicity trial. OBI-1 or Hyate:C were given in a series of four intravenous injections at weekly intervals at doses of 1, 10, or 100 U kg,1. Inhibitory antibodies to porcine FVIII were not detected by Bethesda assay in most of the mice given OBI-1 or Hyate:C at doses of 1 or 10 U kg,1, but were identified in 81% and 94% of mice given 100 U kg,1 of OBI-1 or Hyate:C, respectively. There was no significant difference between OBI-1 and Hyate:C in inhibitory antibody formation at any dose, although there was a trend toward a lower Bethesda titer in OBI-1-treated mice at 10 U kg,1 (P = 0.09). Total anti-FVIII antibodies to Hyate:C and OBI-1 were also measured by ELISA using immobilized purified plasma-derived porcine FVIII and OBI-1, respectively, as antigens. At the 10 and 100 U kg,1 doses, the mean anti-FVIII response was higher in Hyate:C-treated-mice than in OBI-1-treated mice (P = 0.02 and P = 0.004, respectively). The results using this model suggest that OBI-1 may be less immunogenic and safer than Hyate:C in FVIII inhibitor patients. [source] Evaluation of pharmacokinetics, efficacy and safety of Immunate® solvent detergent in previously treated patients with severe haemophilia AHAEMOPHILIA, Issue 1 2007L. NEMES Summary., Immunate® Solvent Detergent (S/D) is a plasma derived, purified, human factor VIII (FVIII) , von Willebrand factor (VWF) complex subjected to two virus inactivation/removal processes: S/D and vapor heat treatment. This prospective, multicentre, three-part clinical study evaluated the pharmacokinetics (in comparison to the predecessor product Immunate®), efficacy and safety of Immunate® S/D in 56 previously treated patients with severe haemophilia A. Subjects received Immunate® S/D on-demand, as a prophylactic regimen or both. The results of the pharmacokinetic population demonstrate that Immunate® and Immunate® S/D were equivalent with respect to the FVIII , and to the retrospectively VWF , parameters assessed. A total of 623 bleeding episodes were reported in 47/56 subjects. The duration of prophylaxis ranged from 0.1--5.2 months with a total of 175.6 months. The median number of bleeds per month in subjects on prophylaxis was 0 (range 0--10). Ninety-six percent of bleeding episodes were rated as having an excellent or good response. For most bleeding episodes (89%), subjects required only one infusion with a mean dose of 29.6 IU kg,1. No FVIII inhibitory antibodies were observed in any subject. No related serious adverse events were reported. Thus, the introduction of S/D treatment did not alter the PK characteristics and function of VWF and FVIII molecules of Immunate® S/D which is effective and safe for treatment of bleeding episodes, management of surgical procedures, and prophylaxis. [source] Health economics of treating haemophilia A with inhibitorsHAEMOPHILIA, Issue 2005C. KNIGHT Summary., Haemophilia is a rare, inherited blood disorder in which blood clotting is impaired such that patients suffer from excessive internal and external bleeding. At present there is no cure for haemophilia A and patients require expensive, life-long treatment involving clotting factor replacement therapy. Treatment costs are perceived to be higher for patients who have developed inhibitory antibodies to factor VIII, the standard therapy for haemophilia A. However, initial cost analyses suggest that clotting factor therapy with alternative haemostatic agents, such as recombinant activated factor VII or activated prothrombin complex concentrate, is no more expensive for the majority of haemophilia A patients with inhibitors than for those without inhibitors. With the availability of effective alternative haemostatic agents, orthopaedic surgery for haemophilia A patients with inhibitors is now a clinical option, and initial cost analyses suggest this may be a cost-effective treatment strategy for patients with inhibitors whose quality of life (QoL) is severely impaired by joint arthropathy. In an era of finite healthcare resourcing it is important to determine whether new treatments justify higher unit costs compared with standard therapies and whether such higher costs are justified from an individual perspective in terms of improved QoL, and from a societal perspective in terms of improved productivity and reduced overall healthcare costs. This paper examines current data on the health economics of treating haemophilia A patients with inhibitors, focusing on the overall costs of clotting factor replacement therapy and the cost consequences of joint replacement. [source] FEIBA®: mode of actionHAEMOPHILIA, Issue 2004P. L. Turecek Summary., FEIBA®(factor eight inhibitor bypassing activity) has a history of more than 30 years of successful use in controlling bleeding in haemophilic patients who have developed inhibitory antibodies against factor (F)VIII or FIX. Recently it was shown that FEIBA® contains the proenzymes of the prothrombin complex factors, prothrombin, FVII, FIX and FX, but only very small amounts of their activation products, with the exception of FVIIa, which is contained in FEIBA® in greater amounts. FEIBA® controls bleeding by induction and facilitation of thrombin generation, a process for which FV is crucial. A number of biochemical in vitro and in vivo studies have shown that FXa and prothrombin play a critical role in the activity of FEIBA®. Consequently, they are considered to be key components of this product. The prothrombinase complex has been found to be a major target site for FEIBA®. Apart from prothrombin and FXa, FEIBA® contains other proteins of the prothrombin complex, which could also facilitate haemostasis in haemophilia patients with inhibitors. [source] Comparative immunogenicity of recombinant B domain-deleted porcine factor VIII and Hyate:C in hemophilia A mice presensitized to human factor VIIIJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 4 2004E. T. Parker Summary., Hyate is a commercial plasma-derived porcine factor (F)VIII concentrate that is used in the treatment of patients with inhibitory antibodies to FVIII. OBI-1 is a recombinant B domain-deleted form of porcine FVIII that is in clinical development for the same indication. Hemophilia A mice were presensitized with human FVIII to simulate clinical inhibitory antibody formation and then were randomized to receive OBI-1 or Hyate:C in a comparative immunogenicity trial. OBI-1 or Hyate:C were given in a series of four intravenous injections at weekly intervals at doses of 1, 10, or 100 U kg,1. Inhibitory antibodies to porcine FVIII were not detected by Bethesda assay in most of the mice given OBI-1 or Hyate:C at doses of 1 or 10 U kg,1, but were identified in 81% and 94% of mice given 100 U kg,1 of OBI-1 or Hyate:C, respectively. There was no significant difference between OBI-1 and Hyate:C in inhibitory antibody formation at any dose, although there was a trend toward a lower Bethesda titer in OBI-1-treated mice at 10 U kg,1 (P = 0.09). Total anti-FVIII antibodies to Hyate:C and OBI-1 were also measured by ELISA using immobilized purified plasma-derived porcine FVIII and OBI-1, respectively, as antigens. At the 10 and 100 U kg,1 doses, the mean anti-FVIII response was higher in Hyate:C-treated-mice than in OBI-1-treated mice (P = 0.02 and P = 0.004, respectively). The results using this model suggest that OBI-1 may be less immunogenic and safer than Hyate:C in FVIII inhibitor patients. [source] Sustained delivery of therapeutic concentrations of human clotting factor IX , a comparison of adenoviral and AAV vectors administered in uteroTHE JOURNAL OF GENE MEDICINE, Issue 1 2002Holm Schneider Abstract Background Prenatal somatic gene therapy has been considered for genetic disorders presenting with morbidity at birth. Haemophilia is associated with an increased risk of catastrophic perinatal bleeding complications such as intracranial haemorrhage, which could be prevented by gene transfer in utero. Prenatal gene therapy may be more promising than postnatal treatment, as the fetus may be more amenable to uptake and integration of therapeutic DNA and the immaturity of its immune system may permit life-long immune tolerance of the transgenic protein, thus avoiding the dominant problem in haemophilia treatment, the formation of inhibitory antibodies. Methods Adenovirus serotype 5-derived or AAV serotype 2-derived vectors carrying human clotting factor IX (hfIX) cDNA or a reporter gene were administered intramuscularly, intraperitoneally or intravascularly to late-gestation mouse fetuses. Both vector types were evaluated with respect to the kinetics of hfIX delivery to the systemic circulation and possible immune responses against the vector or the transgene product. Results Mice treated in utero by intramuscular injection of an adenoviral vector carrying hfIX cDNA exhibited high-level gene expression at birth and therapeutic , albeit continuously decreasing , plasma concentrations of hfIX over the entire 6 months of the study. Adenoviral vector spread to multiple organs was detected by polymerase chain reaction (PCR). Intramuscular, intraperitoneal or intravascular application of AAV vectors carrying hfIX cDNA led to much lower plasma concentrations of hfIX shortly after birth, which appeared to decline during the first month of life but stabilized in some of the mice at detectable levels. No signs of immune responses were found, either against the different viral vectors or against hfIX. Conclusion This study demonstrates for the first time that sustained systemic delivery of a therapeutic protein can be achieved by prenatal gene transfer. It thus shows the feasibility of gene therapy in utero and provides a basis for considering this concept as a preventive therapeutic strategy for haemophilia and perhaps also for other plasma protein deficiencies. Copyright © 2002 John Wiley & Sons, Ltd. [source] Time course of serum inhibitory activity for facilitated allergen,IgE binding during bee venom immunotherapy in childrenCLINICAL & EXPERIMENTAL ALLERGY, Issue 9 2009E-M Varga Summary Background Immunotherapy for bee venom allergy is effective and provides long-term protection. Venom-specific IgG4 levels are increased but with no correlation with clinical improvement. Following grass pollen immunotherapy, elevation of antigen-specific IgG4 is accompanied by increases in IgG-dependent serum inhibitory activity for IgE-facilitated binding of allergen,IgE complexes to B cells. As this ,functional' assay of inhibitory antibodies may be more predictive of clinical efficacy, we investigated the time course of serum inhibitory activity for IgE-facilitated antigen binding during venom immunotherapy (VIT) in children and following 2 years of VIT withdrawal. Methods Ten bee venom-allergic children (mean age: 9.3 years; m/f, 7/3) with moderate to severe allergic reactions to bee stings received VIT. A separate group of seven children (mean age: 14 years; m/f, 5/2) were investigated 2 years after VIT withdrawal. Ten age- and gender-matched children served as non-allergic controls. Allergen-specific serum IgG4 and IgE levels were measured by ELISA at baseline, after 2 years of VIT and 2 years after VIT withdrawal. Serum inhibitory activity was assessed using the facilitated-allergen binding (FAB) assay. Results Sera obtained during VIT significantly inhibited allergen,IgE binding to B-cells (pre-treatment=104±23%; 2 years=46±15%; P<0.001) when compared with sera obtained after treatment withdrawal and sera from normal controls. In parallel to FAB inhibition during VIT, significantly higher IgG4 levels were noted after immunotherapy (pre-treatment=8.6±2.3 AU; 2 years=26.7±3.5 AU; P<0.001) compared with those observed after withdrawal and in the controls. In contrast, progressively lower IgE concentrations were observed compared with pre-treatment (44±7 AU) in sera obtained after 2 years of VIT (25±5 AU; P<0.01) and 2 years following the withdrawal of VIT (10±3 AU; P<0.05). Conclusions In contrast to grass pollen immunotherapy, the persistent decline in venom-specific IgE levels, rather than serum inhibitory activity for FAB, may be more relevant for long-term clinical efficacy of VIT. [source] Incidence of inhibitors in a cohort of 838 males with hemophilia A previously treated with factor VIII concentratesJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 12 2006C. L. KEMPTON Summary.,Background:,Development of an inhibitory antibody to factor VIII is currently the most serious complication of hemophilia A treatment. The rate of inhibitor development in those that have been previously treated with factor concentrates is poorly defined. Understanding the baseline rate of inhibitor development in the population of previously treated patients (PTPs) is important when evaluating the effect of exposure to new factor replacement products on inhibitor formation. Objectives:,To determine the rate of inhibitor development in PTPs with hemophilia A. Methods:,A cohort of males with hemophilia A who had data collected on four or more occasions prior to 30 March 2003, as part of the Center for Disease Control and Prevention's Universal Data Collection Project, were eligible for inclusion in the cohort. Patients were included in the cohort if they had at least two Bethesda assay measurements and did not have an inhibitor prior to or at the start of the study period. The overall incidence rate was estimated as the number of verified incident inhibitor cases divided by the total follow-up time in years multiplied by 1000 (cases per 1000 person-years). Results:,A total of 838 patients were included in the study. The overall incidence rate was calculated to be 2.14 cases per 1000 person years. All incident cases had more than 50 exposure days prior to inhibitor development. Conclusions:,Given the low rate of inhibitor development in PTPs with hemophilia A, small, non-randomized studies are inadequate to determine the rate of inhibitor development after exposure to novel products. Ongoing, standardized, postmarketing surveillance is needed to determine if novel factor products pose an increased risk of inhibitor development. [source] | ||||||||||