We report the largest international study on Glanzmann thrombasthenia (GT), an inherited bleeding disorder where defects of the ITGA2B and ITGB3 genes cause quantitative or qualitative defects of the ...alpha IIb beta 3 integrin, a key mediator of platelet aggregation. Sequencing of the coding regions and splice sites of both genes in members of 76 affected families identified 78 genetic variants (55 novel) suspected to cause GT. Four large deletions or duplications were found by quantitative real-time PCR. Families with mutations in either gene were indistinguishable in terms of bleeding severity that varied even among siblings. Families were grouped into type I and the rarer type II or variant forms with residual alpha IIb beta 3 expression. Variant forms helped identify genes encoding proteins mediating integrin activation. Splicing defects and stop codons were common for both ITGA2B and ITGB3 and essentially led to a reduced or absent alpha IIb beta 3 expression; included was a heterozygous c.1440-13_c.1440-1del in intron 14 of ITGA2B causing exon skipping in seven unrelated families. Molecular modeling revealed how many missense mutations induced subtle changes in alpha IIb and beta 3 domain structure across both subunits, thereby interfering with integrin maturation and/or function. Our study extends knowledge of GT and the pathophysiology of an integrin. Glanzmann thrombasthenia (GT) is a rare inherited bleeding syndrome given by mutations in the ITGA2B and ITGB3 genes that encode the alpha IIb beta 3 integrin that mediates platelet aggregation. Here, we have expanded the mutation spectrum in GT by screening ITGA2B and ITGB3 in 76 families and defining subtle changes in integrin structure leading to absent or aberrant integrin expression. Reference is also made to defects in genes involved in alpha IIb beta 3 activation and variant GT-like syndromes.
ABSTRACT
We report the largest international study on Glanzmann thrombasthenia (GT), an inherited bleeding disorder where defects of the ITGA2B and ITGB3 genes cause quantitative or qualitative ...defects of the αIIbβ3 integrin, a key mediator of platelet aggregation. Sequencing of the coding regions and splice sites of both genes in members of 76 affected families identified 78 genetic variants (55 novel) suspected to cause GT. Four large deletions or duplications were found by quantitative real‐time PCR. Families with mutations in either gene were indistinguishable in terms of bleeding severity that varied even among siblings. Families were grouped into type I and the rarer type II or variant forms with residual αIIbβ3 expression. Variant forms helped identify genes encoding proteins mediating integrin activation. Splicing defects and stop codons were common for both ITGA2B and ITGB3 and essentially led to a reduced or absent αIIbβ3 expression; included was a heterozygous c.1440‐13_c.1440‐1del in intron 14 of ITGA2B causing exon skipping in seven unrelated families. Molecular modeling revealed how many missense mutations induced subtle changes in αIIb and β3 domain structure across both subunits, thereby interfering with integrin maturation and/or function. Our study extends knowledge of GT and the pathophysiology of an integrin.
Glanzmann thrombasthenia (GT) is a rare inherited bleeding syndrome given by mutations in the ITGA2B and ITGB3 genes that encode the αIIbβ3 integrin that mediates platelet aggregation. Here, we have expanded the mutation spectrum in GT by screening ITGA2B and ITGB3 in 76 families and defining subtle changes in integrin structure leading to absent or aberrant integrin expression. Reference is also made to defects in genes involved in αIIbβ3 activation and variant GT‐like syndromes.
Standard treatment for Glanzmann thrombasthenia, a severe inherited bleeding disorder, is platelet transfusion. Recombinant factor VIIa is reported to be effective in Glanzmann thrombasthenia with ...platelet antibodies and/or refractoriness to platelet transfusions. We aimed to evaluate recombinant factor VIIa effectiveness and safety for the treatment and prevention of surgical bleeding in patients, with or without platelet antibodies and/or refractoriness, using data from the Glanzmann Thrombasthenia Registry, an international, multicenter, observational, post-marketing study of rFVIIa. Between 2007 and 2011, 96 patients were treated for 206 surgical procedures (minor 169, major 37). History of platelet antibodies was present in 43 patients, refractoriness in 23, antibodies+refractoriness in 17, while 47 had no confirmed antibodies/refractoriness. Treatments analyzed included antifibrinolytics, recombinant factor VIIa, recombinant factor VIIa+antifibrinolytics, platelets±antifibrinolytics and recombinant factor VIIa+platelets±antifibrinolytics. The most frequent treatment for minor procedures was recombinant factor VIIa+antifibrinolytics (n=65), and for major procedures, recombinant factor VIIa+platelets±antifibrinolytics (n=13). In patients without antibodies/refractoriness, recombinant factor VIIa, either alone or with antifibrinolytics, and platelets±antifibrinolytics were rated 100% effective for minor and major procedures. The effectiveness of treatment for minor procedures in patients with antibodies and refractoriness was 88.9% for recombinant factor VIIa, 100% for recombinant factor VIIa+antifibrinolytics, 66.7% for platelets±antifibrinolytics and 100% for recombinant factor VIIa+platelets±antifibrinolytics. One of four adverse events reported for surgery was considered recombinant factor VIIa-treatment-related (non-fatal thromboembolic event in an adult female receiving recombinant factor VIIa+platelets+antifibrinolytics). For all patients, regardless of platelet antibody or refractoriness status, recombinant factor VIIa, administered with or without platelets (±antifibrinolytics), provided effective hemostasis with a low frequency of adverse events in surgical procedures in Glanzmann thrombasthenia patients. This trial was registered at clinicaltrials.gov identifier: 01476423.
Abstract Introduction The value and challenges of long-term prophylaxis (LTP) in adolescents and young adults need further characterisation. Aim To determine the proportions of adolescents and young ...adults with severe or moderately severe haemophilia in France under LTP and treatment on demand (OD). Methods Patients 15 to 25 years old with haemophilia A or B, factor VIII/IX ≤ 2% and no current inhibitor could be included if they had been under factor VIII/IX treatment at least 12 months and kept a treatment and bleeding diary. Results LTP was administered to 169/212 patients (79.7%) and OD treatment to 40/212 patients (18.9%). The most frequent reasons for initiating LTP were joint bleeding, target joints and frequent bleeds; whereas OD treatment was most often selected on the basis of mild bleeding phenotype or because of constraints on LTP. The mean annual bleed rate (ABR) in the OD group (6.33) was higher than in the LTP group (3.07, p < 0.001). Mean ABR did not differ significantly between age strata (15
–
18, > 18
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21 and > 21
–
25 years), but was significantly higher for patients with severe haemophilia (4.02) as compared to those with moderate haemophilia (1.97, p = 0.002). No significant difference was observed in mean ABR for joint bleeds between the LTP and OD groups. Physician reported LTP compliance was good or excellent in 97.0% of patients. Conclusion LTP is the predominant factor VIII/IX treatment among adolescents and young adults with severe or moderately severe haemophilia in France. LTP was associated with low ABR and high compliance.
Induction of heme oxygenase-1, a stress-inducible enzyme with anti-inflammatory activity, reduces the immunogenicity of therapeutic factor VIII in experimental hemophilia A. In humans, heme ...oxygenase-1 expression is modulated by polymorphisms in the promoter of the heme oxygenase-1-encoding gene (HMOX1). We investigated the relationship between polymorphisms in the HMOX1 promoter and factor VIII inhibitor development in severe hemophilia A. We performed a case-control study on 99 inhibitor-positive patients and 263 patients who did not develop inhibitors within the first 150 cumulative days of exposure to therapeutic factor VIII. Direct sequencing and DNA fragment analysis were used to study (GT)n polymorphism and single nucleotide polymorphisms located at -1135 and -413 in the promoter of HMOX1. We assessed associations between the individual allele frequencies or genotypes, and inhibitor development. Our results demonstrate that inhibitor-positive patients had a higher frequency of alleles with large (GT)n repeats (L: n≥30), which are associated with lesser heme oxygenase-1 expression (odds ratio 2.31; 95% confidence interval 1.46-3.66; P<0.001. Six genotypes (L/L, L/M, L/S, M/M, M/S and S/S) of (GT)n repeats were identified (S: n<21; M: 21≤n<30). The genotype group including L alleles (L/L, L/M and L/S) was statistically more frequent among inhibitor-positive than inhibitor-negative patients, as compared to the other genotypes (33.3% versus 17.1%) (odds ratio 2.21, 95% confidence interval 1.30-3.76; P<0.01). To our knowledge, this is the first association identified between HMOX1 promoter polymorphism and development of anti-drug antibodies. Our study paves the way towards modulation of the endogenous anti-inflammatory machinery of hemophilia patients to reduce the risk of inhibitor development.
We report the largest international study on Glanzmann thrombasthenia (GT), an inherited bleeding disorder where defects of the ITGA2B and ITGB3 genes cause quantitative or qualitative defects of the ...alphaIIbbeta3 integrin, a key mediator of platelet aggregation. Sequencing of the coding regions and splice sites of both genes in members of 76 affected families identified 78 genetic variants (55 novel) suspected to cause GT. Four large deletions or duplications were found by quantitative real-time PCR. Families with mutations in either gene were indistinguishable in terms of bleeding severity that varied even among siblings. Families were grouped into type I and the rarer type II or variant forms with residual alphaIIbbeta3 expression. Variant forms helped identify genes encoding proteins mediating integrin activation. Splicing defects and stop codons were common for both ITGA2B and ITGB3 and essentially led to a reduced or absent alphaIIbbeta3 expression; included was a heterozygous c.1440-13_c.1440-1del in intron 14 of ITGA2B causing exon skipping in seven unrelated families. Molecular modeling revealed how many missense mutations induced subtle changes in alphaIIb and beta3 domain structure across both subunits, thereby interfering with integrin maturation and/or function. Our study extends knowledge of GT and the pathophysiology of an integrin.
Clinical trial data are scarce for the use of prophylaxis in people with non-severe haemophilia A. The HAVEN 6 study aims to assess safety and efficacy of emicizumab prophylaxis in people with ...non-severe haemophilia A without factor VIII (FVIII) inhibitors.
HAVEN 6 is a multicentre, open-label, single-arm, phase 3 study taking place in 22 specialty clinics and hospitals in Europe, North America, and South Africa. Eligible participants were people of all ages weighing at least 3 kg with a diagnosis of moderate (FVIII activity ≥1%-≤5%) or mild (FVIII >5%-<40%) haemophilia A without FVIII inhibitors requiring prophylaxis as assessed by the treating physician. Participants received subcutaneous emicizumab 3 mg/kg of bodyweight once weekly for 4 weeks, followed by the participant's choice of maintenance dose: 1·5 mg/kg once weekly, 3 mg/kg every 2 weeks, or 6 mg/kg every 4 weeks. Safety was the primary objective of the study. Safety endpoints included adverse events, serious adverse events, and adverse events of special interest including thromboembolic events and thrombotic microangiopathies. The primary efficacy endpoint was the annualised bleed rate for treated bleeds. Analyses were done for participants who received at least one dose of emicizumab. This study is registered with ClinicalTrials.gov, number NCT04158648, and is active but not recruiting.
Between Feb 10, 2020, and Aug 31, 2021, we assigned 73 people to treatment. 72 participants received at least one dose of emicizumab (51 moderate 71%; 21 mild 29%; 69 male 96%; three female 4%; and 61 White 85%). Median age was 23·5 years (IQR 12·0-36·0); median follow-up was 55·6 weeks (IQR 52·3-61·6) weeks. At baseline, 24 participants (33%) had target joints and 37 (51%) were receiving FVIII prophylaxis. 60 participants (83%) had at least one adverse event; the most common adverse events were headache (in 12 participants 17%), injection-site reaction (12 17%), and arthralgia (11 15%). 15 (21%) had at least one emicizumab-related adverse event; no adverse events led to treatment withdrawal, modification, or interruption. Eight participants (11%) reported ten serious adverse events in total, none emicizumab-related. There were no deaths or thrombotic microangiopathies. One participant had grade 1 thrombosed haemorrhoids (classified as a thromboembolic event), unrelated to emicizumab. The annualised bleed rate was 0·9 (95% CI 0·55-1·52) for treated bleeds. 48 participants (67%) had no treated bleeds. All-bleed annualised bleed rates were 10·1 (95% CI 6·93-14·76) from 24 weeks pre-study and 2·3 (1·67-3·12) on-study after a median follow-up of 55·6 weeks.
These data show efficacy and a favourable safety profile of emicizumab in people with non-severe haemophilia A without FVIII inhibitors who warrant prophylaxis, confirming emicizumab as a valuable treatment option in this population.
F Hoffmann-La Roche.
In the present study, we have analyzed the T cell receptor (TCR) repertoires of CD4+ T cells isolated from peripheral blood of 10 inhibitor-positive patients with severe hemophilia A. The ...distribution of complementarity determining region (CDR3) lengths of the beta chain of the TCRs was analyzed by spectratyping prior to and following in vitro stimulation of the cells with human factor VIII (FVIII). The repertoires of CD4+ T cells of patients were perturbed when compared to those of healthy blood donors. The perturbations of T cell repertoires were heterogeneous among patients with respect to the number and the nature of V-beta (BV) families that exhibited expansion following incubation with FVIII. Some patients showed alterations in one or two BV families, others exhibited more perturbed repertoires affecting 5 to 8 of the 14 BV families tested. Alterations of BV2, BV5 and/or BV9 were consistently found after incubation of CD4+ T cells in the presence of FVIII in 80% of the patients. These findings indicate that the presence of FVIII inhibitors in patients with severe hemophilia A is associated with measurable perturbations of the CD4+ T cell repertoire that results from oligoclonal expansion of FVIII-specific cells and may be relevant for the design of strategies aimed at modulating the anti-FVIII immune responses by T cell-targeted therapy
The therapeutic field of in utero transplantation of stem cells, into human fetuses, has developed since 1988 with the hope of improved probability of engraftment and tolerance, due to immune ...immaturity of the host. Fifteen years later, it is possible to evaluate the results that we and others have obtained in the treatment of several fetal diseases. Seven fetal patients have been treated in Lyon: In 2 cases, pregnancy termination was induced by the in utero injection; in the 5 other cases, engraftment was obtained and repeatedly documented with presence of donor HLA antigens and/or Y chromosome in recipients. In the 2 patients with combined immunodeficiency disease, a sustained reconstitution of immunity was obtained as a result of the transplant but other complications occurred thereafter. In patients with thalassemia major, Niemann-Pick disease or hemophilia, a very partial and very transitory benefit was only obtained. Approximately 33 other patients with immunodeficiencies, hemoglobinopathies or inborn errors of metabolism have been treated worldwide, over the last 13 years, with a comparable method, using parental or fetal stem cells transplanted in utero. Successful treatment has usually been recorded in immunodeficiencies, and insufficient results have been obtained in the other cases. This form of treatment can therefore be recommended after prenatal diagnosis of combined immunodeficiency but additional research is required to improve the degree of engraftment, the lack of resistance of the host and the 'space' available for hematopoiesis in the other conditions.
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