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Inhibitor Development (inhibitor + development)
Selected AbstractsMild haemophilia: a disease with many faces and many unexpected pitfallsHAEMOPHILIA, Issue 2010K. PEERLINCK Summary., Despite major advances in diagnosis and treatment, the management of patients with mild haemophilia (MH) remains a major challenge. Mild haemophilia is defined by factor levels between 0.05 and 0.40 IU mL,1. The bleeding associated with mild haemophilia is most frequently episodic, occurring during surgery or following trauma. Spontaneous bleeding is rare. Diagnosis is sometimes delayed because of insensitivity of screening clotting assays or discrepancies in factor VIII activity as measured by different assays. The treatment of choice in mild haemophilia A is desmopressin, which typically induces a 2,6-fold increase of factor VIII over baseline. However, desmopressin has its limitations in this setting such as the occurrence of tachyphylaxis and failure to respond in an undetermined proportion of patients. Factors underlying poor biological response or magnitude of response to desmopressin are incompletely understood. Inhibitor development in mild haemophilia is particularly distressing. This complication arises at an older age in this patient group because of infrequent need for factor VIII replacement. Inhibitors in mild haemophilia patients often cross-react with endogenous factor VIII resulting in severe spontaneous bleeding frequently in a postoperative setting. Intensive perioperative use of factor VIII and some specific mutations induce a particularly high risk for inhibitor development, but risk factors are incompletely understood. For reasons of the older age of the patients, treatment of bleeding with bypassing agents may cause major thrombotic complications. Data on therapeutic options for inhibitor eradication in patients with mild haemophilia are particularly scarce. With increased life-expectancy for all haemophilia patients, the group of elderly patients with mild haemophilia requiring major surgery will further increase. Prevention of inhibitors, particularly in this patient group, should be a major topic of interest in both clinic and research. [source] Current challenges of pharmacovigilance in bleeding disorders: converting the burden to benefitHAEMOPHILIA, Issue 2 2010R. LASSILA Summary., Safety surveillance studies have proven essential in research and development of new biological therapies for bleeding disorders as well as other diseases. Although product safety regarding HIV, hepatitis, and other blood-borne infections is currently excellent, potential new infectious agents require continued vigilant monitoring. Inhibitor development is the most common serious side effect of haemophilia replacement therapy. Several aetiological factors associated with inhibitors have been identified, but their true impact is still largely unknown. Moreover, whether plasma-derived and recombinant factor products differ in their immunogenic profiles is an unresolved issue. Coagulation factor products under development and those currently on the market require uniform, long-term surveillance. The European Haemophilia Safety Surveillance (EUHASS) project was recently established to meet these goals. The pharmaceutical industry and clinicians face common challenges complying with these requirements. In rare diseases like haemophilia, obtaining adequate patient numbers poses a challenge. Another challenge is a lack of methods for assessing disease severity, a surprising deficiency in the era of modern medical and laboratory technology. National and international registries can be used to gather required safety surveillance information. Simultaneously, clinicians benefit from well-organized registry data in their daily practice and harmonize the quality of comprehensive haemophilia care by homogeneous follow-up platforms. Experience with such registries comes, for example, from Europe (PEDNET), the USA (CDC/UDC), the UK (UKHCDO), and Sweden (Malmö). It is important to commit to future pharmacovigilance efforts, aiming at high-quality safety surveillance programmes at both the pharmaceutical research community and clinical levels. [source] Inhibitor development in patients receiving recombinant factor VIII (Recombinate rAHF/Bioclate®): a prospective pharmacovigilance studyHAEMOPHILIA, Issue 5 2004B. M. Ewenstein Summary., Clinical trials to date have not been adequately powered to assess comparatively infrequent events such as inhibitor development in previously treated patients (PTPs). Comprehensive large-scale pharmacovigilance studies can be useful for this purpose. We prospectively collected inhibitor development reports worldwide among recipients of Recombinate rAHF recombinant factor VIII (rFVIII), also formerly distributed under the product name Bioclate®, for the entire postlicensure period from 1993 through 2002. To determine level of exposure to rFVIII we also compiled the Recombinate rAHF/Bioclate International Units (IU) distributed annually. To estimate inhibitor incidence separately for previously untreated or minimally treated patients (PUPs) with 1,50 exposure days and PTPs with >50 exposure days, we used haemophilia A incidence and prevalence data and pooled mean annual rFVIII consumption per PUP and PTP from international multicentre prospective clinical trials. Documented inhibitor cases totalled 89, and the total quantity of Recombinate rAHF/Bioclate rFVIII distributed was 6.48 ×109 IU. No lot association or other clustering of inhibitor events was evident in PTPs. The incidence of all reported inhibitors, expressed as a percentage of patients treated, was 11.9% (CI: 5.05,28.0%) for PUPs when compared with 0.123% (CI: 0.030,0.512%) for PTPs. The rates for high-titre inhibitors (>5 BU) only were 5.96% (CI: 3.00,11.8%) for PUPs and 0.0554% (CI: 0.0113,0.271%) for PTPs. Thus, incidence rates for both all inhibitors and high-titre inhibitors in PTPs were 1% of the corresponding rates in PUPs. Data from prospective PUP clinical trials involving intensive active monitoring suggest that true inhibitor incidence may be approximately twice that estimated in this pharmacovigilance study. Nevertheless, inhibitor development in PTPs receiving Recombinate rAHF/Bioclate is infrequent. [source] Mild haemophilia: a disease with many faces and many unexpected pitfallsHAEMOPHILIA, Issue 2010K. PEERLINCK Summary., Despite major advances in diagnosis and treatment, the management of patients with mild haemophilia (MH) remains a major challenge. Mild haemophilia is defined by factor levels between 0.05 and 0.40 IU mL,1. The bleeding associated with mild haemophilia is most frequently episodic, occurring during surgery or following trauma. Spontaneous bleeding is rare. Diagnosis is sometimes delayed because of insensitivity of screening clotting assays or discrepancies in factor VIII activity as measured by different assays. The treatment of choice in mild haemophilia A is desmopressin, which typically induces a 2,6-fold increase of factor VIII over baseline. However, desmopressin has its limitations in this setting such as the occurrence of tachyphylaxis and failure to respond in an undetermined proportion of patients. Factors underlying poor biological response or magnitude of response to desmopressin are incompletely understood. Inhibitor development in mild haemophilia is particularly distressing. This complication arises at an older age in this patient group because of infrequent need for factor VIII replacement. Inhibitors in mild haemophilia patients often cross-react with endogenous factor VIII resulting in severe spontaneous bleeding frequently in a postoperative setting. Intensive perioperative use of factor VIII and some specific mutations induce a particularly high risk for inhibitor development, but risk factors are incompletely understood. For reasons of the older age of the patients, treatment of bleeding with bypassing agents may cause major thrombotic complications. Data on therapeutic options for inhibitor eradication in patients with mild haemophilia are particularly scarce. With increased life-expectancy for all haemophilia patients, the group of elderly patients with mild haemophilia requiring major surgery will further increase. Prevention of inhibitors, particularly in this patient group, should be a major topic of interest in both clinic and research. [source] Postmarketing surveillance study of KOGENATE® Bayer with Bio-Set® in patients with haemophilia A: evaluation of patients' satisfaction after switch to the new reconstitution systemHAEMOPHILIA, Issue 1 2010N. VIDOVIC Summary., KOGENATE® Bayer (rFVIII-FS) with Bio-Set® is designed to prevent patient contact with exposed needles during recombinant factor VIII reconstitution. This postmarketing surveillance study evaluated patient satisfaction before and after switching to the new Bio-Set reconstitution method. Male children and adults with haemophilia A were enrolled from nine European countries. A preference questionnaire was administered to patients after Bio-Set training and at the end of the observation period (,20 exposure days or 3 months). Physician assessments of patient compliance and satisfaction were conducted at the end of the observation period. Patients (N = 306) received a mean ± SD of 28 ± 23 infusions of rFVIII-FS with Bio-Set. A majority of patients (82%) preferred the Bio-Set method, with domain scores for ease of use, safety from needlesticks, and speed of reconstitution being highest after training and at the end of the observation period. The Bio-Set method received higher mean scores than previous reconstitution methods for worry/safety and ease/confidence domains at both time points. Physician-reported patient compliance with the Bio-Set method was similar or greater compared with the previous method for 94% of the patients, with physicians reporting that 92% of the patients were satisfied or very satisfied with Bio-Set. Thirteen adverse events (AEs) occurred in nine patients, and five serious AEs occurred in five patients; none was related to rFVIII-FS. No de novo or recurrent inhibitor development was observed during the observation period. rFVIII-FS with Bio-Set was well tolerated and well accepted by haemophilia A patients, which may improve treatment compliance. [source] Forum on: the role of recombinant factor VIII in children with severe haemophilia AHAEMOPHILIA, Issue 2 2009M. FRANCHINI Summary., The development of recombinant FVIII (rFVIII) products, fuelled by the need for improved safety of treatment arising from the dramatic widespread blood-borne virus transmission in the 1970,1980s revolutionized the care of children with haemophilia A over the last two decades. The larger availability of perceived safer replacement therapy associated with the introduction of rFVIII products reassured the haemophilia community and there was a strong push in some Western countries to treat haemophilic children only with rFVIII. Moreover, this significantly contributed in the 1990s to the diffusion outside Northern Europe of prophylactic regimens implemented at an early age to prevent bleeding and the resultant joint damage (i.e. primary prophylaxis), together with the possibility of home treatment. These changes led to a substantial improvement of the quality of life of haemophilic children and of their families. The general agreement that primary prophylaxis represents the first-choice treatment for haemophilic children has been recently supported by two randomized controlled trials carried out with rFVIII products, providing evidence on the efficacy of early prophylaxis over on-demand treatment in preserving joint health in haemophilic children. However, the intensity and optimal modalities of implementation of prophylaxis in children, in particular with respect to the issue of the venous access, are still debated. A number of studies also supports the role of secondary prophylaxis in children, frequently used in countries in which primary prophylaxis was introduced more recently. With viral safety now less than an issue and with the more widespread use of prophylaxis able to prevent arthropathy, the most challenging complication of replacement therapy for children with haemophilia remains the risk of inhibitor development. Despite conflicting data, there is no evidence that the type of FVIII concentrate significantly influences the complex multifactorial process leading to anti-FVIII alloantibodies, whereas other treatment-related factors are likely to increase (early intensive treatments due to surgery or severe bleeds) or reduce (prophylaxis) the risk. Although the optimal regimen is still uncertain, eradication of anti-FVIII antibodies by immune tolerance induction (ITI), usually with the same product administered at inhibitor detection, should be the first-choice treatment for all patients with recent onset inhibitors. This issue applies particularly to children, as most patients undergo ITI at an early age, when inhibitors usually appear. The availability of a stable and long-lasting venous access represents a leading problem also in this setting. These and other topics concerning rFVIII treatment of haemophilic children were discussed in a meeting held in Rome on 27 February 2008 and are summarized in this report. [source] Safety and efficacy of a plasma-derived monoclonal purified factor VIII concentrate during 10 years of follow-upHAEMOPHILIA, Issue 6 2007E. P. MAUSER-BUNSCHOTEN Summary., In 1995, AAFACT®, a new monoclonal purified factor VIII concentrate (FVIII), derived from human plasma, was introduced in the Netherlands. The monoclonal purification based production process includes a viral inactivation step by solvent/detergent treatment. Products manufactured according to this procedure, for example Hemofil M® are used worldwide. The aim of the present study was to assess inhibitor development in a large cohort of previously treated patients (PTPs) who were followed up for 10 years. In addition, efficacy, HIV and hepatitis C virus (HCV) transmission, and allergic reactions were monitored. All 165 patients with severe haemophilia A (FVIII < 1%) known at the van Creveldkliniek who ever used AAFACT® during the period from October 1995 to September 2005 were included. Two of them were previously untreated patients (PUPs) and two others had <50 exposure days. Data on FVIII consumption, number of exposures, bleedings and hospitalization days were collected from start of AAFACT® until last clinical and laboratory evaluation while on this product. At the end of follow-up, 91 patients were still using this plasma-derived FVIII. Median age at start of follow-up was 26 years (range 1,52). None of the patients reported lack of efficacy. Median FVIII consumption per patient during follow-up was 2058 IU kg,1 bodyweight per year, and median number of exposures was 148 per year. During 1029 patient-years of follow-up, one inhibitor was diagnosed in a previously treated patient PTP. This patient developed high titre inhibitor following surgery for which he, during 1 week, had been treated with continuous infusion with recombinant FVIII. No inhibitor occurred during 68 cases of surgery using continuous infusion with AAFACT®. No viral transmissions or other adverse events occurred during 10 years of follow-up; AAFACT® appeared to be an effective and safe FVIII product. [source] Reformulated BeneFix®: efficacy and safety in previously treated patients with moderately severe to severe haemophilia BHAEMOPHILIA, Issue 3 2007T. LAMBERT Summary. BeneFix®, the only recombinant factor IX (FIX), has been reformulated. The reformulation involves a change in diluent and allows for more concentrated infusions of recombinant FIX. A double-blind, randomized, pharmacokinetic (PK) crossover study demonstrated that reformulated BeneFix was bioequivalent to original BeneFix and follow-up PK evaluation after 6 months of treatment demonstrated the PK stability of reformulated BeneFix after multiple exposures. Favourable efficacy and safety profiles, consistent with those already well-established for original BeneFix, were observed: 81.1% of haemorrhages resolved with only a single infusion; 85.3% of initial treatment response ratings were Excellent or Good; more than half of the subjects using reformulated BeneFix for routine prophylaxis (11 of 17, 64.7%) had no spontaneous haemorrhages during their 6,12 month course of prophylactic treatment, with an overall spontaneous bleeding rate of 0.72 year,1; and for the single surgical procedure (knee washing), treatment was rated Useful. In addition, there was no FIX inhibitor development, allergic-type manifestations, or thrombogenic complications with more than 1100 infusions (nearly 5.2 million IUs) administered in this trial. All efficacy and safety outcomes from this study were achieved with more concentrated recombinant protein infusions than that possible with original BeneFix, and utilization of the 2000 IU per vial dosage strength, newly introduced with the reformulated product, was high (>62%). The reformulation of BeneFix allows smaller delivery volumes and an increased choice of dosage strengths without altering the PK properties (including incremental recovery and half-life) or the established efficacy and safety profile of recombinant FIX. [source] Continuous infusion of factor concentrates in children with haemophilia A in comparison with bolus injectionsHAEMOPHILIA, Issue 3 2006C. BIDLINGMAIER Summary., Although the concept of continuous infusion (CI) of factor concentrates is well known, prospective paediatric data are rare. We present a prospective open-labelled non-randomized study focusing on safety, efficacy and factor VIII (FVIII) usage compared with bolus injections (BI) in children. In 43 consecutive patients (0.5,17 years; median: 9.6) undergoing different operations, CI was started with an initial FVIII-bolus of 70 IU kg,1 bodyweight, followed by a median infusion rate of 4.4 IU kg,1 h,1 (range: 2.8,9.5) dose adjusted for daily FVIII levels (target: 60,80%). No direct serious adverse events occurred; however, two out of 43 patients, both from the group of four patients with less than 20 exposure days (ED) before starting CI, developed a high-responding inhibitor. Two CI patients showed mild thrombophlebitis or rash. Infusion rates needed to achieve adequate FVIII levels were highly predictable and could be reduced because of decreasing FVIII clearance. Bleeding, requiring additional boli, was observed in eight out of 43 patients. Therapy duration and factor usage of CI were influenced by the procedure, but not by the product used or thrombophilia. Twelve of these CI patients were compared with 12 contemporary consecutive age- and procedure-matched BI patients. Compared with BI patients, CI patients saved 30% FVIII (812.9 vs. 563.2 IU kg,1, P < 0.006). We conclude that CI forms a safe and effective method for perioperative care in children and reduces factor usage. Because of the unknown risk of inhibitor development, we will use CI only in patients beyond 20 ED. [source] Inhibitor development in patients receiving recombinant factor VIII (Recombinate rAHF/Bioclate®): a prospective pharmacovigilance studyHAEMOPHILIA, Issue 5 2004B. M. Ewenstein Summary., Clinical trials to date have not been adequately powered to assess comparatively infrequent events such as inhibitor development in previously treated patients (PTPs). Comprehensive large-scale pharmacovigilance studies can be useful for this purpose. We prospectively collected inhibitor development reports worldwide among recipients of Recombinate rAHF recombinant factor VIII (rFVIII), also formerly distributed under the product name Bioclate®, for the entire postlicensure period from 1993 through 2002. To determine level of exposure to rFVIII we also compiled the Recombinate rAHF/Bioclate International Units (IU) distributed annually. To estimate inhibitor incidence separately for previously untreated or minimally treated patients (PUPs) with 1,50 exposure days and PTPs with >50 exposure days, we used haemophilia A incidence and prevalence data and pooled mean annual rFVIII consumption per PUP and PTP from international multicentre prospective clinical trials. Documented inhibitor cases totalled 89, and the total quantity of Recombinate rAHF/Bioclate rFVIII distributed was 6.48 ×109 IU. No lot association or other clustering of inhibitor events was evident in PTPs. The incidence of all reported inhibitors, expressed as a percentage of patients treated, was 11.9% (CI: 5.05,28.0%) for PUPs when compared with 0.123% (CI: 0.030,0.512%) for PTPs. The rates for high-titre inhibitors (>5 BU) only were 5.96% (CI: 3.00,11.8%) for PUPs and 0.0554% (CI: 0.0113,0.271%) for PTPs. Thus, incidence rates for both all inhibitors and high-titre inhibitors in PTPs were 1% of the corresponding rates in PUPs. Data from prospective PUP clinical trials involving intensive active monitoring suggest that true inhibitor incidence may be approximately twice that estimated in this pharmacovigilance study. Nevertheless, inhibitor development in PTPs receiving Recombinate rAHF/Bioclate is infrequent. [source] Home management of haemophiliaHAEMOPHILIA, Issue 2 2004J. M. Teitel Summary., The demonstrated benefits of home care for haemophilia include improved quality of life, less pain and disability, fewer hospitalizations, and less time lost from work or school. Although reduced mortality has not been demonstrated, the substantial increase in longevity since the early 1980s correlates with the introduction of home treatment and prophylaxis programmes. These programmes must be designed and monitored by haemophilia treatment centres (HTC), which are staffed with professionals with broad and complementary expertise in the disease and its complications. In return, patients and their families must be willing to accept the reciprocal responsibilities that come from administering blood products or their recombinant equivalents at home. Patients with inhibitors to factors VIII or IX pose special challenges, but these complications do not obviate participation in home care programmes. Home care was an essential prerequisite to the introduction of effective prophylactic factor replacement therapy. Prophylaxis offers significant improvements in quality of life, but requires a substantial commitment. The use of implantable venous access devices can eliminate some of the difficulty and discomfort of peripheral venous access in small children, but brings additional risks. The future holds the promise of factor concentrates for home use that have longer half-lives, or can be administered by alternate routes. Knowledge of patient genotypes may allow treatments tailored to avoid complications such as inhibitor development. Gene therapy trials, which are currently ongoing, will ultimately lead to gene-based treatments as a complement to traditional protein-based therapy. [source] The epidemiology of inhibitors in haemophilia A: a systematic reviewHAEMOPHILIA, Issue 4 2003J. Wight Summary., This paper emphasizes the importance of distinguishing between the prevalence, incidence and cumulative incidence of inhibitors in haemophilia A. Incidence and cumulative incidence data will include patients with transient inhibitors or whose inhibitors have been eliminated by treatment. As these will not be included in prevalence data, prevalence studies will tend to give rise to lower figures than incidence studies. As a result, the most accurate estimates of the true risk of inhibitor development comes from prospective studies of newly diagnosed haemophiliacs who are tested regularly for the presence of inhibitors. This paper reports a systematic review of the best available evidence relating to the epidemiology of inhibitors in haemophilia A. Cohort studies, registry data reporting incidence or prevalence of inhibitors in patients with haemophilia A, and prospective studies of factor VIII (FVIII) in the treatment of previously untreated patients which reported the development of inhibitors as an outcome, were included in the review. The overall prevalence of inhibitors in unselected haemophiliac populations was found to be 5,7%. The cumulative risk of inhibitor development varied (0,39%). Incidence and prevalence were substantially higher in patients with severe haemophilia. Studies of patients using a single plasma-derived FVIII (pdFVIII) preparation reported lower inhibitor incidence than those using multiple pdFVIII preparations or single recombinant FVIII preparations. Incidence data should be used to estimate the likely demand for treatments aimed at eliminating inhibitors, whereas the best estimates of the overall burden to the National Health Service (NHS) of treating bleeding episodes in patients with continuing inhibitors will come from prevalence studies. [source] Lack of evidence for increased inhibitor incidence in patients switched from plasma-derived to recombinant factor VIIIHAEMOPHILIA, Issue 4 2001I. Scharrer De novo inhibitor development is a rare event in PTPs switched from pdFVIII to rFVIII. Based on previously published data of clinical studies a change in FVIII product is unlikely to provoke inhibitor formation. [source] Safety and efficacy of a new recombinant FVIII formulated with sucrose (rFVIII,FS) in patients with haemophilia A: a long-term, multicentre clinical study in JapanHAEMOPHILIA, Issue 3 2001A. Yoshioka The recombinant full-length FVIII product Kogenate® has been reformulated using sucrose (rFVIII,FS) instead of human serum albumin as a stabiliser in purification and formulation. The in vivo recovery, haemostatic efficacy, and safety of rFVIII,FS were investigated in 20 previously treated patients with severe or moderate haemophilia A for , 24 weeks. In vivo recoveries of 73.5 ± 16.3%, 78.4 ± 16.1%, and 82.8 ± 23.9% after the initial infusion of 50 IU kg,1 rFVIII,FS and at weeks 12 and 24, respectively, showed no significant changes over time. A total of 1115 infusions (mean dose 24.1 ± 8.4 IU kg,1) were included in the analysis of haemostatic efficacy. One (80.5%) or two (8.2%) infusions achieved adequate haemostasis in 88.7% of all bleeding episodes, and haemostatic efficacy was judged ,excellent' or ,good' in 749 of 764 episodes (98.0%). The haemostatic efficacy was judged as ,excellent' or ,good' in 924 of 1115 (82.9%) infusions. Twenty-one adverse events were observed in 12 patients in the total 1541 infusions included in the safety analysis. Causality with respect to rFVIII,FS could not be ruled out in three events in one HIV-negative patient: elevated CD4(%), decreased CD8(%), and elevated CD4/CD8 ratio. No FVIII inhibitor development was observed in any patient. ELISA assay testing for antibodies to rFVIII, baby hamster kidney cell (BHK) protein, and murine IgG were all negative. These results show that rFVIII,FS is a safe and effective for long-term treatment of patients with haemophilia A. [source] Recombinant factor IX (BeneFix®) by adjusted continuous infusion: a study of stability, sterility and clinical experienceHAEMOPHILIA, Issue 2 2001P. Chowdary The safety and efficacy of adjusted continuous infusion (CI) of recombinant factor IX (FIX; BeneFix®) was assessed in vitro and in a clinical study. BeneFix® was reconstituted at 100 IU mL,1 with or without unfractionated heparin (4 U mL,1) and stored at either 4 °C or room temperature. Reconstituted BeneFix® retained at least 90% activity over 14 days if stored at 4 °C but stability was reduced at room temperature. BeneFix® reconstituted in a sterile pharmacy was free of bacterial contamination. Six patients with haemophilia B received seven CIs of BeneFix® to cover routine surgery and severe bleeding episodes. The CIs lasted between 3 and 10 days. In all cases, haemostasis was excellent and the desired therapeutic FIX level was easily maintained. No thrombotic episodes or inhibitor development occurred but two patients developed thrombophlebitis at the infusion site when heparin was not added to the infusion. BeneFix® is not currently licensed for CI and we suggest that studies to enable licensing should be established as soon as possible. [source] Analysis of cytokine genes polymorphism as markers for inhibitor development in haemophilia AINTERNATIONAL JOURNAL OF IMMUNOGENETICS, Issue 2 2010D. Chaves Summary Antibodies that block factor VIII (FVIII) activity appear in some haemophilia A patients treated with FVIII replacement therapy and severely impaired treatment. To date, the mechanisms that lead to this immune response are unknown. In this work, haplotypes of cytokine interleukin 10 (IL-10) gene have been associated with the presence of FVIII inhibitors in a group of Brazilian haemophilia A patients. The coexistence of a haplotype defining high IL-10 synthesis and one defining an intermediate production of cytokines is found to be associated with the group of patients who have a history of inhibitor development. Additionally, the coexistence of haplotypes defining high and low IL-10 syntheses is strongly associated with the group of negative inhibitors. These results have shown that the simple association considering only the presence or the absence of a haplotype and the development of inhibitors in haemophilia A is not sufficient. Data obtained in this work sustain the idea that the genetic studies may partly explain why only approximately 25% of haemophilia A patients develop FVIII inhibitors. Other genetic issues and details of the protein replacement therapy should be considered to measure the chances of a patient to develop anti-FVIII antibodies. [source] In non-severe hemophilia A the risk of inhibitor after intensive factor treatment is greater in older patients: a case,control studyJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 10 2010C. L. KEMPTON Summary.,Background:,Twenty-five percent of new anti-factor VIII (FVIII) antibodies (inhibitors) that complicate hemophilia A occur in those with mild and moderate disease. Although intensive FVIII treatment has long been considered a risk factor for inhibitor development in those with non-severe disease, its strength of association and the influence of other factors have remained undefined. Objective:,To evaluate risk factors for inhibitor development in patients with non-severe hemophilia A. Methods:,Information on clinical and demographic variables and FVIII genotype was collected on 36 subjects with mild or moderate hemophilia A and an inhibitor and 62 controls also with mild or moderate hemophilia A but without an inhibitor. Results:,Treatment with FVIII for six or more consecutive days during the prior year was more strongly associated with inhibitor development in those , 30 years of age compared with those < 30 years of age [adjusted odds ratio (OR) 12.62; 95% confidence interval (CI), 2.76,57.81 vs. OR 2.54; 95% CI, 0.61,10.68]. Having previously received < 50 days of FVIII was also not statistically associated with inhibitor development on univariate or multivariate analysis. Conclusions:,These findings suggest that inhibitor development in mild and moderate hemophilia A varies with age, but does not vary significantly with lifetime FVIII exposure days: two features distinct from severe hemophilia A. [source] Impact of polymorphisms of the major histocompatibility complex class II, interleukin-10, tumor necrosis factor-, and cytotoxic T-lymphocyte antigen-4 genes on inhibitor development in severe hemophilia AJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 12 2009A. PAVLOVA Summary.,Background: Approximately 25% of severe hemophilia A (HA) patients develop antibodies to factor VIII protein. Patients: In the present case-controlled cohort study, 260 severely affected, mutation-type-matched HA patients were studied for association of human leukocyte antigen (HLA) class II molecules and polymorphisms in the genes encoding interleukin-10 (IL-10), tumor necrosis factor-, (TNF-,) and cytotoxic T-lymphocyte antigen-4 (CTLA-4) and development of inhibitors. Results: Our results demonstrate a higher frequency of DRB1*15 and DQB1*0602 alleles as well as of the haplotype DRB1*15/DQB1*0602 in inhibitor patients [odds ratio (OR) 1.9; P < 0.05]. In TNF-,, the A allele of the ,308G>A polymorphism was found with higher frequency in the inhibitor cohort (0.22 vs. 0.13, OR 1.80). This finding was more pronounced for the homozygous A/A genotype (OR 4.7). For IL-10, the ,1082G allele was observed more frequently in patients with inhibitors (0.55 vs. 0.43; P = 0.008). The functional cytokine phenotype was determined for the first time, on the basis of the genetic background, and this showed that 12% of patients with inhibitors were high-TNF-,/high-IL-10 producers, as compared with 3% of non-inhibitor patients (OR 4.4). A trend for a lower frequency of the A allele of the CT60 polymorphism in CTLA-4 was found in inhibitor patients (0.42 vs. 0.50). Conclusions: In conclusion, the reported data clearly highlighted the participation of HLA molecules in inhibitor formation in a large cohort of patients. The higher frequencies of the ,308G>A polymorphism in TNF-, and ,1082A>G in IL-10 in inhibitor patients confirmed the earlier published data. The CT60 single-nucleotide polymorphism in CTLA-4 is of apparently less importance. [source] Factor VIII gene (F8) mutations as predictors of outcome in immune tolerance induction of hemophilia A patients with high-responding inhibitorsJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 11 2009A. COPPOLA Summary.,Background:, Immune tolerance induction (ITI) is the only therapeutic approach that can eradicate factor VIII (FVIII) inhibitors in patients with hemophilia A. Predictors of ITI outcome are still debated, and the role of F8 gene mutations in this is not well established. Objectives: To investigate the relationship between F8 genotype and ITI outcome in patients with severe hemophilia A and high-responding inhibitors. Patients and Methods:F8 mutations were identified in 86 patients recruited as part of the Italian ITI registry (the PROFIT study). ITI outcome was centrally reviewed according to the following definitions: success (undetectable inhibitor and normal FVIII pharmacokinetics), partial success (inhibitor titer < 5 BU mL,1 and/or abnormal FVIII pharmacokinetics), and failure. Results:F8 mutations known to be associated with a high risk of inhibitor development (large deletions, inversions, nonsense mutations and splice site mutations) were found in 70 patients (81%); among these, the intron 22 inversion was present in 49 patients (57%). In 16 patients (19%) lower-risk F8 defects (small insertions/deletions and missense mutations) were identified. The latter group of patients showed a significantly higher ITI success rate than those carrying high-risk mutations [13/16 (81%) vs. 33/70 (47%); risk ratio 1.7, 95% confidence interval (CI) 1.1,2.1, P = 0.01]. On multivariate analysis, the mutation risk class remained a significant predictor of success [adjusted odds ratio (OR) 6.2, 95% CI 1.1,36.0, P = 0.04], as were inhibitor titer at ITI start (< 5 BU mL,1, OR 11.8, 95% CI 3.5,40.2, P < 0.001), and peak titer during ITI (< 100 BU mL,1, OR 11.4, 95% CI 3.2,40.8, P < 0.001). Conclusions: ITI success is influenced by F8 genotype. This knowledge should contribute to the stratification of prognosis, and to the clinical choices made for ITI in patients with high-responding inhibitors. [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] More on: intensive factor VIII exposure and inhibitor development in mild hemophilia AJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 4 2004M. D. Carcao [source] Immune reconstitution inflammatory syndrome (IRIS) as a cause for inhibitor development in hemophiliaJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 1 2004S. Werwitzke No abstract is available for this article. [source] Engineering the catalytic domain of human protein tyrosine phosphatase , for structure-based drug discoveryACTA CRYSTALLOGRAPHICA SECTION D, Issue 12 2006Artem G. Evdokimov Protein tyrosine phosphatases (PTPs) play roles in many biological processes and are considered to be important targets for drug discovery. As inhibitor development has proven challenging, crystal structure-based design will be very helpful to advance inhibitor potency and selectivity. Successful application of protein crystallography to drug discovery heavily relies on high-quality crystal structures of the protein of interest complexed with pharmaceutically interesting ligands. It is very important to be able to produce protein,ligand crystals rapidly and reproducibly for as many ligands as necessary. This study details our efforts to engineer the catalytic domain of human protein tyrosine phosphatase , (HPTP,-CD) with properties suitable for rapid-turnaround crystallography. Structures of apo HPTP,-CD and its complexes with several novel small-molecule inhibitors are presented here for the first time. [source] Efficacy and inhibitor development in previously treated patients with haemophilia A switched to a B domain-deleted recombinant factor VIII , clarification of Kogenate inhibitor dataBRITISH JOURNAL OF HAEMATOLOGY, Issue 1 2005Peter Larson No abstract is available for this article. [source] A Macrophage Cell Model for Selective Metalloproteinase Inhibitor DesignCHEMBIOCHEM, Issue 13 2008Faith E. Jacobsen Abstract The desire to inhibit zinc-dependent matrix metalloproteinases (MMPs) has, over the course of the last 30 years, led to the development of a plethora of MMP inhibitors that bind directly to the active-site metal. With one exception, all of these drugs have failed in clinical trials, due to many factors, including an apparent lack of specificity for MMPs. To address the question of whether these inhibitors are selective for MMPs in a biological setting, a cell-based screening method is presented to compare the relative activities of zinc, heme iron, and non-heme iron enzymes in the presence of these compounds using the RAW264.7 macrophage cell line. We screened nine different zinc-binding groups (ZBGs), four established MMP inhibitors (MMPis), and two novel MMP inhibitors developed in our laboratory to determine their selectivities against five different metalloenzymes. Using this model, we identified two nitrogen donor compounds,2,2,-dipyridylamine (DPA) and triazacyclononane (TACN),as the most selective ZBGs for zinc metalloenzyme inhibitor development. We also demonstrated that the model could predict known nonspecific interactions of some of the most commonly used MMPis, and could also give cross-reactivity information for newly developed MMPis. This work demonstrates the utility of cell-based assays in both the design and the screening of novel metalloenzyme inhibitors. [source] | |||||||||||||