Building the foundation for a community-generated national research blueprint for inherited bleeding disorders: research priorities to transform the care of people with hemophilia

BACKGROUND

Decades of research have transformed hemophilia from severely limiting children's lives to a manageable disorder compatible with a full, active life, for many in high-income countries. The direction of future research will determine whether exciting developments truly advance health equity for all people with hemophilia (PWH). National Hemophilia Foundation (NHF) and American Thrombosis and Hemostasis Network conducted extensive inclusive all-stakeholder consultations to identify the priorities of people with inherited bleeding disorders and those who care for them.

RESEARCH DESIGN AND METHODS

Working group (WG) 1 of the NHF State of the Science Research Summit distilled the community-identified priorities for hemophilia A and B into concrete research questions and scored their feasibility, impact, and risk.

RESULTS

WG1 defined 63 top priority research questions concerning arthropathy/pain/bone health, inhibitors, diagnostics, gene therapy, the pediatric to adult transition of care, disparities faced by the community, and cardiovascular disease. This research has the potential to empower PWH to thrive despite lifelong comorbidities and achieve new standards of wellbeing, including psychosocial.

CONCLUSIONS

Collaborative research and care delivery will be key to capitalizing on current and horizon treatments and harnessing technical advances to improve diagnostics and testing, to advance health equity for all PWH.

Screening for inattention, hyperactivity and impulsivity in children with haemophilia: A quality improvement intervention

INTRODUCTION

Children with haemophilia have been reported with increased rates of inattention (IN) and hyperactivity/impulsivity (HI) and, therefore, are particularly vulnerable to poor social and academic outcomes.

AIM

To examine the benefit of utilizing a formal screening process for IN/HI in children with haemophilia during comprehensive clinic visits using a quality improvement approach.

METHODS

At a single haemophilia treatment centre, screening for psychosocial issues was expanded and formalised to include (1) the Conners 3^rd Edition (Conners3) screening tool for IN/HI symptoms administered during the standard psychosocial assessment (SPA) by the social worker and school advocacy coordinator, (2) formal pathways to diagnosis and intervention as indicated including psychology consultation, psychological testing, or referral to community-based mental health professionals, and in-person advocacy assistance in the patient's community school.

RESULTS

Forty-four patients, age 9.9 ± 4.8 years (range 3-16) were targeted. The initial screening approach was modified to improve the communication with caretakers during assessments and streamline diagnostic pathways if no, moderate or significant behavioural concerns were identified. Eleven patients had pre-existing mental health diagnoses. Thirteen of the remaining 33 patients (39.4%) received a new mental health diagnosis, ADHD in 8/33 (24.2%). Of the total cohort, 54.5% were found to have a mental health diagnosis. The rate of ADHD (29.5%) was significantly higher than reported in the general population.

CONCLUSION

The described process, developed through a QI approach, allowed formal and objective screening for IN/HI, streamlined a pathway to diagnosis and intervention, and identified undiagnosed disabilities in children with haemophilia improving their access to services.

Gene Therapy and Hemophilia: Where Do We Go from Here?

Gene therapy for hemophilia using adeno-associated virus (AAV) derived vectors can reduce or eliminate patients' disease-related complications and improve their quality of life. Broad implementation globally will lead to societal gains and foster health equity. Several vector products each for factor IX (FIX) or factor VIII (FVIII) deficiency are in advanced clinical development. Safety data are reassuring. Efficacy data for up to 8 and 5 years, respectively, vary considerably among vector types and among individuals, but indicate significant reduction in bleeds and factor use. Products will soon be approved for marketing. This review highlights the relevant considerations for implementation of hemophilia gene therapy, specifically across a broad range of socioeconomic backgrounds globally, based on recent publications and our own experience. We address the current efficacy and safety data and relevant aspects of vector immunology. We then discuss pertinent implementation steps including pre-implementation and readiness assessments, considerations on cost, cost-effectiveness and payment models, approaches to education and informed consent, and the operational needs as well as the need for monitoring of health outcomes and implementation outcomes. To prevent a lag or complete lack of establishing access to this life-changing therapy option for all patients with hemophilia worldwide, adaptable pathways supported by collaborative and international efforts of all stakeholders are needed.

Haemophilia gene therapy-Update on new country initiatives

INTRODUCTION

Gene therapy is emerging as a potential cure for haemophilia. Gene therapy is a one-time treatment that can elevate factor levels for many years and minimize or eliminate the need for clotting factor concentrate (CFC) replacement therapy. However, there is a paucity of reports on gene therapy efforts in countries outside of North America or Europe, especially in low-and-middle-income countries (LMIC). All indications are that gene therapy will be one of standard care treatments for haemophilia in the future. Still, it may not be accessible to many countries due to various barriers and challenges. At the same time, each country may formulate solutions that may be used globally.

AIM

To summarize the approaches taken to establish haemophilia gene therapy in Japan, China, India, South Africa, and Brazil, and to describe the US-initiated multi-LMIC haemophilia gene therapy development program to include Peru, Vietnam, Thailand, Nepal, and Sri Lanka.

METHODS

A review of related published information or as accessible by each country's author.

RESULTS

Different starting conditions, differing input and level of support from the multitude of stakeholders, and strong leadership have led to various approaches for facilitating research and developing needed infrastructure and regulatory and financing models. Gene therapy programs are at various stages of development and include both adeno-associated viral and lentiviral vectors.

CONCLUSION

Global partnerships and collaboration, exchange of knowledge and experience, and alignment of processes across borders will promote further progress towards global access to gene therapy for haemophilia.

Quality of life in a large multinational haemophilia B cohort (The B-Natural study) - Unmet needs remain

Introduction

The B‐Natural study is a multicentre, multinational, observational study of haemophilia B (HB) designed to increase understanding of clinical manifestations, treatment and quality of life (QoL).

Aim

To characterise and compare QoL in HB across disease severity groups and individuals with inhibitors to identify gaps in treatment.

Methods

A total of 224 individuals from 107 families were enrolled from a total of 24 centres in North America (n = 16), Europe (n = 7) and Asia (n = 1). Of these, 68 (30.4%) subjects had severe (<1 IU/dL), median age 15.6 years, 114 (50.9%) moderate (1–5 IU/dL), age 13.3 years, and 42 (18.8%) mild (>5–< 40 IU/dL), age 12.1 years, disease. Twenty‐nine participants had inhibitors or a history of inhibitors. Three versions of the EQ‐5D instrument were used as a measure of QoL: proxy (ages 4–7), youth (ages 8–15) and self (age 16+). Each instrument included a visual analogue scale ranging from 100 (best health) to 0 (worst health) to assess current day's health (EQ VAS). Range‐of‐motion (ROM) for elbows, knees and ankles was assessed using a four‐point scale, from which a composite score was calculated.

Results

In all severity groups, a proportion of subjects showed less than optimal QoL. The majority of the mild and moderate severe participants reported a normal EQ‐5D health profile (79% and 72%, respectively), whereas about half (47%) of the severe participants and only 13% of the inhibitor participants reported this profile.

Conclusion

The B‐Natural study reveals impacted QoL in all disease severities of HB including those with inhibitors. Unmet needs remain and include nonsevere HB.

Limited sampling strategies for accurate determination of extended half-life factor VIII pharmacokinetics in severe haemophilia A patients

BACKGROUND

Extended half-life (EHL) factor VIII (FVIII) products may decrease the burden of prophylactic treatment in haemophilia A by reducing infusion frequency. However, these products still exhibit wide inter-patient variability and benefit from pharmacokinetic (PK) tailoring.

OBJECTIVE

Identify limited sampling strategies for rFVIIIFc, an EHL FVIII product, that produce accurate estimates of PK parameters and relevant troughs.

METHODS

We performed a limited sampling analysis on simulated populations of adults, adolescents, and children based on published population PK data. Sampling strategies were evaluated by comparing the error in estimates of half-life, clearance, and trough levels, to a full 6-sample design. Furthermore, we assessed the impact of incorporating knowledge about prior doses, and the day of the PK study within the regimen. We also evaluated the potential inappropriate dose adjustment rate (IDAR) among the modelled sampling strategies.

RESULTS

Many sampling strategies, including several 2-sample designs, accurately predicted the PK and exposure measures (median absolute error <10%). When samples are only collected during a single visit (i.e., predose + peak), inclusion of prior dose information reduces median half-life error from >20% to ~5% for adults/adolescents. In this same scenario, appropriate scheduling of the PK study decreases likelihood of unmeasurable predose samples, reducing median error on the 72-h trough from 25% to <12% in the youngest population.

CONCLUSIONS

The PK of rFVIIIFc can be accurately estimated using only peak and trough samples, provided that knowledge of prior doses is incorporated and the PK study is planned on an appropriate day within the dosing regimen.

Natural history study of factor IX deficiency with focus on treatment and complications (B-Natural)

INTRODUCTION

Haemophilia B (HB) is less well studied than haemophilia A (HA); despite similarities between the two inherited bleeding disorders, important differences remain that require further research.

AIM

B-Natural is a multi-centre, prospective, observational study of HB, designed to increase understanding of clinical manifestations, treatment, quality-of-life (QoL), inhibitor development, immune tolerance induction (ITI) outcome, renal function and create a biorepository for future investigations.

METHODS

Participants include sibling pairs/groups without a current/history of inhibitors and singletons or siblings with a current/history of inhibitors followed for six months. Demographics, medical, social history and treatment were recorded. A physical examination including joint range of motion (ROM) was performed; QoL was assessed. Samples were collected for F9 gene mutation, HLA typing, non-inhibitory antibodies and renal function testing.

RESULTS

Twenty-four centres enrolled 224 individuals from 107 families including 29 with current/history of inhibitors. Of these, 68, 30.4%, had severe (<1% FIX level of normal); 114, 50.9%, moderate (1%-5%); and 42, 18.8%, mild (>5-<40%) disease. At enrolment, 53.1% had 50 + exposure days to exogenous FIX. Comparison of joint scores showed significant (P < .05) differences between those with severe (with/without inhibitors), and those with moderate/mild disease. The majority with severe disease, 80.0% with current/history of inhibitors and 64.3% of those without, were treated with prophylaxis.

CONCLUSION

B-Natural provides data supporting an increased understanding of HB and its impact throughout life. The need for optimal disease control to normalize physical and psychosocial outcomes is underscored, and further analyses will contribute to an increased understanding of critical issues in HB.

Hemophilia gene therapy-New country initiatives

Gene therapy is an opportunity for haemophilia patients to receive a one-time treatment and have lasting factor levels for years or decades instead of dependence on repeated administration within short intervals and on sustained supply of drug. Great strides have been made in the development of gene therapy for haemophilia in the last decade. Adeno-associated virus (AAV) vector-mediated gene transfer in haemophilia A and B has entered the phase III trial stage. Gene transfer by lentiviral vector or gene editing technologies using factor VIII (FVIII) or IX (FIX) genes are now entering clinical evaluation. It is expected that the first FVIII and FIX gene therapy products will soon be approved and distributed in major markets. Global access to gene therapy is a critical goal. This review presents new and ongoing efforts towards this goal in countries other than North America and Europe. In Japan, researchers, regulators and funders have established a promising gene therapy development platform for multiple diseases including haemophilia. Decades of scientific and clinical research in haemophilia gene therapy in China have led to a recently registered clinical trial of AAV-mediated gene therapy for haemophilia B. Other countries are in earlier phases of building gene therapy programmes or participate in international trials. A phase 2 feasibility trial of AAV-mediated FIX gene therapy in low- and middle-income countries aims to demonstrate that gene therapy could become available in resource-constrained socio-economic settings. The different strategies for establishing gene therapy provide opportunities for closing the global gap in haemophilia care.

Gene therapy for haemophilia

BACKGROUND

Haemophilia is a genetic disorder characterized by spontaneous or provoked, often uncontrolled, bleeding into joints, muscles and other soft tissues. Current methods of treatment are expensive, challenging and involve regular administration of clotting factors. Gene therapy for haemophilia is a curative treatment modality currently under investigation. This is an update of a published Cochrane Review.

OBJECTIVES

To evaluate the safety and efficacy of gene therapy for treating people with haemophilia A or B.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis & Genetic Disorders Group's Coagulopathies Trials Register, compiled from electronic database searches and handsearching of journals and conference abstract books. We also searched the reference lists of relevant articles and reviews. Date of last search: 17 April 2020.

SELECTION CRITERIA

Eligible trials include randomised or quasi-randomised clinical trials, including controlled clinical trials comparing gene therapy (with or without standard treatment) with standard treatment (factor replacement) or other 'curative' treatment such as stem cell transplantation for individuals with haemophilia A or B of all ages who do not have inhibitors to factor VIII or IX.

DATA COLLECTION AND ANALYSIS

No trials of gene therapy for haemophilia matching the inclusion criteria were identified.

MAIN RESULTS

No trials of gene therapy for haemophilia matching the inclusion criteria were identified.

AUTHORS' CONCLUSIONS

No randomised or quasi-randomised clinical trials of gene therapy for haemophilia were identified. Thus, we are unable to determine the safety and efficacy of gene therapy for haemophilia. Gene therapy for haemophilia is still in clinical investigation and there is a need for well-designed clinical trials to assess the long-term feasibility, success and risks of gene therapy for people with haemophilia.

Platelet Transfusions in the PICU: Does Disease Severity Matter?

OBJECTIVES

Pediatric intensivists frequently prescribe platelet transfusions to critically ill children, but there are limited data on platelet transfusion practice and platelet transfusion-related outcomes in the PICU. In this study, we evaluated the current platelet transfusion practice and platelet transfusion-related outcomes in the PICU.

DESIGN

Institutional review board-approved, retrospective cohort study from January 2010 to March 2016.

SETTING

Tertiary-level PICU.

PATIENTS

Children less than 19 years old who received platelet transfusions in the PICU.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Thirty-six percent (1,547/4,339) of platelet transfusions in the institution were given to 2.4% of PICU patients (232/9,659). The patients who received a platelet transfusion (platelet transfusions, n = 232) compared with those who did not receive platelets (no platelet transfusions, n = 9,427) were younger, had similar gender distribution, had a higher median Pediatric Risk of Mortality-3 score, and stayed longer in the PICU. Fifty percent of platelet transfusions were prescribed prophylactically for thrombocytopenia to patients without extracorporeal membrane oxygenation support. The mortality was higher for platelet transfusions group (30% vs 2.3%) with an 18 times increased unadjusted odds of mortality when compared with no platelet transfusion group (odds ratio, 18.2; 95% CI, 13.3-24.8; p < 0.0001). In a multiple logistic regression analysis, the predicted probability of dying for platelet transfusion group compared with no platelet transfusion group depended on the median Pediatric Risk of Mortality-3 score. Patients who received platelet transfusion versus no platelet transfusion have increased odds of dying at lower median Pediatric Risk of Mortality-3 scores, but decreased odds of dying at higher median Pediatric Risk of Mortality-3 scores.

CONCLUSIONS

This PICU cohort demonstrates that the odds or predicted probability of dying change in patients who received platelet transfusions based on underlying disease severity measured by Pediatric Risk of Mortality-3 score compared with patients who did not receive platelet transfusions. A large, prospective trial is required to confirm this association and determine whether to consider underlying disease severity in estimating risks and benefits of prophylactic platelet transfusions in critically ill children.

Gene therapy for haemophilia

BACKGROUND

Haemophilia is a genetic disorder characterized by spontaneous or provoked, often uncontrolled, bleeding into joints, muscles and other soft tissues. Current methods of treatment are expensive, challenging and involve regular administration of clotting factors. Gene therapy has recently been prompted as a curative treatment modality. This is an update of a published Cochrane Review.

OBJECTIVES

To evaluate the safety and efficacy of gene therapy for treating people with haemophilia A or B.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis & Genetic Disorders Group's Coagulopathies Trials Register, compiled from electronic database searches and handsearching of journals and conference abstract books. We also searched the reference lists of relevant articles and reviews.Date of last search: 18 August 2016.

SELECTION CRITERIA

Eligible trials include randomised or quasi-randomised clinical trials, including controlled clinical trials comparing gene therapy (with or without standard treatment) with standard treatment (factor replacement) or other 'curative' treatment such as stem cell transplantation for individuals with haemophilia A or B of all ages who do not have inhibitors to factor VIII or IX.

DATA COLLECTION AND ANALYSIS

No trials of gene therapy for haemophilia were found.

MAIN RESULTS

No trials of gene therapy for haemophilia were identified.

AUTHORS' CONCLUSIONS

No randomised or quasi-randomised clinical trials of gene therapy for haemophilia were identified. Thus, we are unable to determine the safety and efficacy of gene therapy for haemophilia. Gene therapy for haemophilia is still in its nascent stages and there is a need for well-designed clinical trials to assess the long-term feasibility, success and risks of gene therapy for people with haemophilia.

Efficacy and safety of eculizumab in children and adolescents with paroxysmal nocturnal hemoglobinuria

BACKGROUND

Paroxysmal nocturnal hemoglobinuria (PNH) is rare in children, but represents a similarly serious and chronic condition as in adults. Children with PNH frequently experience complications of chronic hemolysis, recurrent thrombosis, marrow failure, serious infections, abdominal pain, chronic fatigue, and decreased quality of life with reduced survival. The terminal complement inhibitor eculizumab is proven to be effective and safe in adults and approved by the FDA for treatment of PNH.

PROCEDURE

This 12-week, open-label, multi-center phase I/II study evaluated pharmacokinetics, pharmacodynamics, efficacy, and safety in seven children with PNH 11-17 years of age. Eculizumab was intravenously administered at 600 mg weekly for 4 weeks, 900 mg in week 5, and 900 mg every 2 weeks thereafter (http://clinicaltrials.gov NCT00867932).

RESULTS

Eculizumab therapy resulted in complete and sustained inhibition of hemolysis in all participants with a reduction of lactate dehydrogenase to normal levels. All hematological parameters stabilized. No definitive, study drug-related adverse events were observed. Only one severe SAE of hospitalization due to aplastic anemia occurred, which was not study drug-related.

CONCLUSION

Eculizumab appears to be a safe and effective therapy for children with PNH.

Diagnosis and treatment of pediatric acquired aplastic anemia (AAA): an initial survey of the North American Pediatric Aplastic Anemia Consortium (NAPAAC)

BACKGROUND

Randomized clinical trials in pediatric aplastic anemia (AA) are rare and data to guide standards of care are scarce.

PROCEDURE

Eighteen pediatric institutions formed the North American Pediatric Aplastic Anemia Consortium to foster collaborative studies in AA. The initial goal of NAPAAC was to survey the diagnostic studies and therapies utilized in AA.

RESULTS

Our survey indicates considerable variability among institutions in the diagnosis and treatment of AA. There were areas of general consensus, including the need for a bone marrow evaluation, cytogenetic and specific fluorescent in situ hybridization assays to establish diagnosis and exclude genetic etiologies with many institutions requiring results prior to initiation of immunosuppressive therapy (IST); uniform referral for hematopoietic stem cell transplantation as first line therapy if an HLA-identical sibling is identified; the use of first-line IST containing horse anti-thymocyte globulin and cyclosporine A (CSA) if an HLA-identical sibling donor is not identified; supportive care measures; and slow taper of CSA after response. Areas of controversy included the need for telomere length results prior to IST, the time after IST initiation defining a treatment failure; use of hematopoietic growth factors; the preferred rescue therapy after failure of IST; the use of specific hemoglobin and platelet levels as triggers for transfusion support; the use of prophylactic antibiotics; and follow-up monitoring after completion of treatment.

CONCLUSIONS

These initial survey results reflect heterogeneity in diagnosis and care amongst pediatric centers and emphasize the need to develop evidence-based diagnosis and treatment approaches in this rare disease.

PG4KDS: a model for the clinical implementation of pre-emptive pharmacogenetics

Pharmacogenetics is frequently cited as an area for initial focus of the clinical implementation of genomics. Through the PG4KDS protocol, St. Jude Children's Research Hospital pre-emptively genotypes patients for 230 genes using the Affymetrix Drug Metabolizing Enzymes and Transporters (DMET) Plus array supplemented with a CYP2D6 copy number assay. The PG4KDS protocol provides a rational, stepwise process for implementing gene/drug pairs, organizing data, and obtaining consent from patients and families. Through August 2013, 1,559 patients have been enrolled, and four gene tests have been released into the electronic health record (EHR) for clinical implementation: TPMT, CYP2D6, SLCO1B1, and CYP2C19. These genes are coupled to 12 high-risk drugs. Of the 1,016 patients with genotype test results available, 78% of them had at least one high-risk (i.e., actionable) genotype result placed in their EHR. Each diplotype result released to the EHR is coupled with an interpretive consult that is created in a concise, standardized format. To support-gene based prescribing at the point of care, 55 interruptive clinical decision support (CDS) alerts were developed. Patients are informed of their genotyping result and its relevance to their medication use through a letter. Key elements necessary for our successful implementation have included strong institutional support, a knowledgeable clinical laboratory, a process to manage any incidental findings, a strategy to educate clinicians and patients, a process to return results, and extensive use of informatics, especially CDS. Our approach to pre-emptive clinical pharmacogenetics has proven feasible, clinically useful, and scalable.

Developments in the treatment of hemophilia B: focus on emerging gene therapy

Hemophilia B is a genetic disorder that is characterized by a deficiency of clotting factor IX (FIX) and excessive bleeding. Advanced understanding of the pathophysiology of the disease has led to the development of improved treatment strategies that aim to minimize the acute and long-term complications of the disease. Patients with hemophilia B are ideal candidates for gene therapy, mostly because a small increase in protein production can lead to significantly decreased bleeding diathesis. Although human clotting FIX was cloned and sequenced over 30 years ago, progress toward achieving real success in human clinical trials has been slow, with long-term, therapeutically relevant gene expression only achieved in one trial published in 2011. The history of this extensive research effort has revealed the importance of the interactions between gene therapy vectors and multiple arms of the host immune system at multiple stages of the transduction process. Different viral vector systems each have unique properties that influence their ability to deliver genes to different tissues, and the data generated in several clinical trials testing different vectors for hemophilia have guided our understanding toward development of optimal configurations for treating hemophilia B. The recent clinical success implementing a novel adeno-associated virus vector demonstrated sufficient FIX expression in patients to convert a severe hemophilia phenotype to mild, an achievement which has the potential to profoundly alter the impact of this disease on human society. Continued research should lead to vector designs that result in higher FIX activity at lower vector doses and with reduced host immune responses to the vector and the transgene product.

The impact of quality and duration of enoxaparin therapy on recurrent venous thrombosis in children

BACKGROUND

Venous thromboembolism (VTE) and recurrent venous thromboembolism (rVTE) are rare, but significant problems in pediatrics. Current recommendations for anticoagulant therapy arise from adult literature, and there is little data on clinical outcomes following therapeutic low-molecular-weight heparin in children.

METHOD

All patients <19 years of age that were diagnosed with a VTE or right atrial thrombus via standard imaging methods at St. Jude Children's Research Hospital were retrospectively identified from January 2004 through August 2008. Demographic characteristics, coexisting clinic conditions, description of anticoagulant therapy, and record of rVTE were chronicled following a comprehensive chart review. Descriptive statistics of clinical characteristics and anticoagulation are presented.

RESULTS

Venous thrombosis was identified in 149 children with 21% (31/149) developing a rVTE. Coexisting clinical conditions were identified in 93% of children at initial diagnosis with 48% (71/149) of patients having a coexisting malignancy. Seventy-seven percent (114/149) of children received anticoagulant therapy with UFH (10/114) or enoxaparin (104/114). Neither duration of enoxaparin therapy (>6, 3-6, <3 months) (P = 0.61), nor quality of therapy (≥75% of time on anticoagulation spent with an anti-FXa of 0.5-1.0 U/ml) (P = 1.0) were found to be protective against rVTE.

CONCLUSION

Anticoagulation with enoxaparin based on adult literature may be suboptimal in preventing rVTE in pediatric populations. Future prospective randomized controlled trials in pediatrics using clinical outcomes with anticoagulant therapy are urgently needed.

Adenovirus-associated virus vector-mediated gene transfer in hemophilia B

BACKGROUND

Hemophilia B, an X-linked disorder, is ideally suited for gene therapy. We investigated the use of a new gene therapy in patients with the disorder.

METHODS

We infused a single dose of a serotype-8-pseudotyped, self-complementary adenovirus-associated virus (AAV) vector expressing a codon-optimized human factor IX (FIX) transgene (scAAV2/8-LP1-hFIXco) in a peripheral vein in six patients with severe hemophilia B (FIX activity, <1% of normal values). Study participants were enrolled sequentially in one of three cohorts (given a high, intermediate, or low dose of vector), with two participants in each group. Vector was administered without immunosuppressive therapy, and participants were followed for 6 to 16 months.

RESULTS

AAV-mediated expression of FIX at 2 to 11% of normal levels was observed in all participants. Four of the six discontinued FIX prophylaxis and remained free of spontaneous hemorrhage; in the other two, the interval between prophylactic injections was increased. Of the two participants who received the high dose of vector, one had a transient, asymptomatic elevation of serum aminotransferase levels, which was associated with the detection of AAV8-capsid-specific T cells in the peripheral blood; the other had a slight increase in liver-enzyme levels, the cause of which was less clear. Each of these two participants received a short course of glucocorticoid therapy, which rapidly normalized aminotransferase levels and maintained FIX levels in the range of 3 to 11% of normal values.

CONCLUSIONS

Peripheral-vein infusion of scAAV2/8-LP1-hFIXco resulted in FIX transgene expression at levels sufficient to improve the bleeding phenotype, with few side effects. Although immune-mediated clearance of AAV-transduced hepatocytes remains a concern, this process may be controlled with a short course of glucocorticoids without loss of transgene expression. (Funded by the Medical Research Council and others; ClinicalTrials.gov number, NCT00979238.).

Severe thrombocytopenia with iron deficiency anemia

Although severe thrombocytopenia has been reported among children with iron deficiency anemia, the presence of both anemia and thrombocytopenia can suggest serious or malignant bone marrow dysfunction, requiring further work-up. This paper reviews the management and outcomes of patients with the diagnosis of iron deficiency anemia presenting with severe thrombocytopenia. The authors present 4 pediatric patients with iron deficiency anemia and severe thrombocytopenia at initial presentation. Charts were reviewed after approval by the institutional review boards at both St. Jude Children's Research Hospital and LeBonheur Children's Medical Center in Memphis, Tennessee. All 4 patients' hemoglobin concentrations and platelet counts normalized within 1 to 3 weeks of initiating iron supplementation, suggesting that in such patients iron supplementation can obviate the need for invasive diagnostic procedures. In addition, these patients all had a platelet "overshoot" phenomenon during iron therapy prior to normalization of platelet counts, the mechanism of which is still unknown. The literature exploring the mechanism behind the current clinical findings is reviewed.

Heparin induced thrombocytopenia and re-thrombosis associated with warfarin and fondaparinux in a child

An 11-year-old female developed heparin induced thrombocytopenia (HIT) with thrombosis during therapy for lower extremity deep vein thrombosis and pulmonary embolism. Transition from bivalirudin, a direct thrombin inhibitor (DTI), to warfarin resulted in extensive re-thrombosis, and fondaparinux therapy similarly failed. She was then treated with argatroban, and transitioned successfully to warfarin after 9 weeks. The risk of re-thrombosis was ultimately reduced by allowing time for the thrombogenic potential to abate. The argatroban/warfarin transition was monitored with chromogenic factor X levels. This case highlights several difficult problems in pediatric thrombosis.

TERC and TERT gene mutations in patients with bone marrow failure and the significance of telomere length measurements

Dyskeratosis congenita (DC) is a rare inherited form of bone marrow failure (BMF) caused by mutations in telomere maintaining genes including TERC and TERT. Here we studied the prevalence of TERC and TERT gene mutations and of telomere shortening in an unselected population of patients with BMF at our medical center and in a selected group of patients referred from outside institutions. Less than 5% of patients with BMF had pathogenic mutations in TERC or TERT. In patients with BMF, pathogenic TERC or TERT gene mutations were invariably associated with marked telomere shortening (<< 1st percentile) in peripheral blood mononuclear cells (PBMCs). In asymptomatic family members, however, telomere length was not a reliable predictor for the presence or absence of a TERC or TERT gene mutation. Telomere shortening was not pathognomonic of DC, as approximately 30% of patients with BMF due to other causes had PBMC telomere lengths at the 1st percentile or lower. We conclude that in the setting of BMF, measurement of telomere length is a sensitive but nonspecific screening method for DC. In the absence of BMF, telomere length measurements should be interpreted with caution.

Beta-thalassemia intermedia due to compound heterozygosity for two beta-globin gene promoter mutations, including a novel TATA box deletion

An 8-year-old African-American boy had a clinical history consistent with mild beta-thalassemia intermedia with moderate anemia, microcytosis, reticulocytosis, and splenomegaly. He was asymptomatic and did not require transfusion. At age 4 years, hemoglobin (Hb) electrophoresis showed Hb A = 37.8%, Hb A(2) = 5.0%, and Hb F = 56.1%. At age 8 years, he was diagnosed to be a compound heterozygote for two beta-globin gene promoter mutations, the relatively common nucleotide (nt) -88 C --> T mutation from the cap site, and a novel two-nucleotide (AA) deletion between nt -29 and -26 within the TATA box of the beta-globin gene. His mother and 14-year-old brother were simple heterozygotes for this novel (AA) deletion. Both heterozygotes had normal Hb level, borderline microcytosis, and elevated Hb A(2).

Hydroxyurea therapy for management of secondary erythrocytosis in cyanotic congenital heart disease

Secondary erythrocytosis in cyanotic congenital heart disease (CCHD) causes substantial morbidity because of complications of hyperviscosity, including stroke and chronic end organ damage. Phlebotomy provides temporary improvement but leads to iron deficiency and can actually increase blood viscosity. We describe the successful use of hydroxyurea (hydroxycarbamide) in four patients with uncorrected CCHD and symptomatic secondary erythrocytosis. In all patients, hydroxyurea improved symptoms of hyperviscosity. Substantial decreases in the red blood cell (RBC) count were observed, along with increases in the mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH), leading to only modest declines in the circulating hemoglobin concentration. Two patients experienced transient mild myelosuppression, which promptly resolved with dose reduction of hydroxyurea. Hydroyxurea provides a novel and useful therapeutic approach to reduce hyperviscosity from secondary erythrocytosis in patients with CCHD, while preserving oxygen carrying capacity and avoiding iron depletion by phlebotomy.