Innovations in RNA therapy for hemophilia.

Given the shortcomings of current factor-, nonfactor-, and adeno-associated virus gene-based therapies, the recent advent of RNA-based therapeutics for hemophilia is changing the fundamental approach to hemophilia management. From small interfering RNA therapeutics that knockdown clot regulators antithrombin, protein S, and heparin cofactor II, to CRISPR/Cas9 gene editing that may personalize treatment, improved technologies have the potential to reduce bleeds and factor use and avoid inhibitor formation. These novel agents, some in preclinical studies and others in early phase trials, have the potential to simplify treatment and improve hemostasis and quality of life. Furthermore, because these therapies arise from manipulation of the coagulation cascade and thrombin generation and its regulation, they will enhance our understanding of hemostasis and thrombosis and ultimately lead to better therapies for children and adults with inherited bleeding disorders. What does the future hold? With the development of novel preclinical technologies at the bench, there will be fewer joint bleeds, debilitating joint disease, orthopedic surgery, and improved physical and mental health, which were not previously possible. In this review, we identify current limitations of treatment and progress in the development of novel RNA therapeutics, including messenger RNA nanoparticle delivery and gene editing for the treatment of hemophilia.

Multiyear Factor VIII Expression after AAV Gene Transfer for Hemophilia A.

BACKGROUND: The goal of gene therapy for patients with hemophilia A is to safely impart long-term stable factor VIII expression that predictably ameliorates bleeding with the use of the lowest possible vector dose. METHODS: In this phase 1-2 trial, we infused an investigational adeno-associated viral (AAV) vector (SPK-8011) for hepatocyte expression of factor VIII in 18 men with hemophilia A. Four dose cohorts were enrolled; the lowest-dose cohort received a dose of 5 × 1011 vector genomes (vg) per kilogram of body weight, and the highest-dose cohort received 2 × 1012 vg per kilogram. Some participants received glucocorticoids within 52 weeks after vector administration either to prevent or to treat a presumed AAV capsid immune response. Trial objectives included evaluation of the safety and preliminary efficacy of SPK-8011 and of the expression and durability of factor VIII. RESULTS: The median safety observation period was 36.6 months (range, 5.5 to 50.3). A total of 33 treatment-related adverse events occurred in 8 participants; 17 events were vector-related, including 1 serious adverse event, and 16 were glucocorticoid-related. Two participants lost all factor VIII expression because of an anti-AAV capsid cellular immune response that was not sensitive to immune suppression. In the remaining 16 participants, factor VIII expression was maintained; 12 of these participants were followed for more than 2 years, and a one-stage factor VIII assay showed no apparent decrease in factor VIII activity over time (mean [±SD] factor VIII activity, 12.9±6.9% of the normal value at 26 to 52 weeks when the participants were not receiving glucocorticoids vs. 12.0±7.1% of the normal value at >52 weeks after vector administration; 95% confidence interval [CI], -2.4 to 0.6 for the difference between matched pairs). The participants had a 91.5% reduction (95% CI, 88.8 to 94.1) in the annualized bleeding rate (median rate, 8.5 events per year [range, 0 to 43.0] before vector administration vs. 0.3 events per year [range, 0 to 6.5] after vector administration). CONCLUSIONS: Sustained factor VIII expression in 16 of 18 participants who received SPK-8011 permitted discontinuation of prophylaxis and a reduction in bleeding episodes. No major safety concerns were reported. (Funded by Spark Therapeutics and the National Heart, Lung, and Blood Institute; ClinicalTrials.gov numbers, NCT03003533 and NCT03432520.).

Observational cohort study of long-term outcomes of liver transplantation in haemophilia.

INTRODUCTION: Gene therapy is now a reality for individuals with haemophilia, yet little is known regarding the quality-of-life impact of factor correction. As few data exist, and recognizing the analogy to liver transplantation (OLTX), we identified OLTX+ and OLTX- men in the ATHNdataset to compare post-OLTX factor VIII and IX on quality of life (QoL) by Haem-A-QoL and PROMIS-29. METHODS: OLTX- were matched to OLTX+ by age, race, and haemophilia type and severity. Deidentified demographic data, including post-transplant factor levels, genotype and target joint disease were analysed by descriptive statistics. Haem-A-Qol and PROMIS-29 were compared in OLTX+ and OLTX- by student's t-test and univariate regression models. RESULTS: Of 86 people with haemophilia A (HA) or haemophilia B (HB) cared for at 10 haemophilia treatment centers (HTCs), 21 (24.4%) OLTX+ and 65 (75.6%) OLTX- were identified. OLTX+ and OLTX- had a similar frequency of target joint disease (p = .806), HA genotypes, null versus non-null (p = .696), and HIV infection (p = .316). At a median 9.2 years post-OLTX, median FVIII, .63 IU/mL [IQR 0.52-0.97] and FIX, .91 IU/mL [IQR .63-1.32], Haem-A-QoL, PROMIS-29, and HOT scores were comparable. Severe HA/HB had lower post-OLTX 'dealing with haemophilia' scores (p = .022) and higher 'sports and leisure' (p = .010) and 'view of yourself' scores (p = .024) than OLTX+ non-severe participants. Non-caucasian OLTX+ had significantly lower scores in sports and leisure (p = .042), future expectations (p = .021) and total score (p = .010). CONCLUSION: Nine years after OLTX, QoL is comparable to OLTX-, but significantly better in OLTX+ with severe than non-severe disease and in caucasians than non-caucasians.

BIVV001 Fusion Protein as Factor VIII Replacement Therapy for Hemophilia A.

BACKGROUND: Factor VIII replacement products have improved the care of patients with hemophilia A, but the short half-life of these products affects the patients' quality of life. The half-life of recombinant factor VIII ranges from 15 to 19 hours because of the von Willebrand factor chaperone effect. BIVV001 (rFVIIIFc-VWF-XTEN) is a novel fusion protein designed to overcome this half-life ceiling and maintain high sustained factor VIII activity levels. Data are lacking on the safety and pharmacokinetics of single-dose BIVV001. METHODS: In this phase 1-2a open-label trial, we consecutively assigned 16 previously treated men (18 to 65 years of age) with severe hemophilia A (factor VIII activity, <1%) to receive a single intravenous injection of recombinant factor VIII at a dose of 25 IU per kilogram of body weight (lower-dose group) or 65 IU per kilogram (higher-dose group). This injection was followed by a washout period of at least 3 days. The patients then received a single intravenous injection of BIVV001 at the same corresponding dose of either 25 IU or 65 IU per kilogram. Adverse events and pharmacokinetic measurements were assessed. RESULTS: No inhibitors to factor VIII were detected and no hypersensitivity or anaphylaxis events were reported up to 28 days after the injection of single-dose BIVV001. The geometric mean half-life of BIVV001 was three to four times as long as that of recombinant factor VIII (37.6 hours vs. 9.1 hours in the lower-dose group and 42.5 vs. 13.2 hours in the higher-dose group); the area under the curve (AUC) for product exposure was six to seven times as great in the two dose groups (4470 hours vs. 638 hours × IU per deciliter in the lower-dose group and 12,800 hours vs. 1960 hours × IU per deciliter in the higher-dose group). After the injection of BIVV001 in the higher-dose group, the mean factor VIII level was in the normal range (≥51%) for 4 days and 17% at day 7, which suggested the possibility of a weekly interval between treatments. CONCLUSIONS: In a small, early-phase study involving men with severe hemophilia A, a single intravenous injection of BIVV001 resulted in high sustained factor VIII activity levels, with a half-life that was up to four times the half-life associated with recombinant factor VIII, an increase that could signal a new class of factor VIII replacement therapy with a weekly treatment interval. No safety concerns were reported during the 28-day period after administration. (Funded by Sanofi and Sobi; ClinicalTrials.gov number, NCT03205163.).

Prevalence and risk factors for hepatocellular carcinoma in individuals with haemophilia in the era of direct-acting antiviral agents: A national inpatient sample study.

BACKGROUND: Hepatocellular carcinoma (HCC) is a major complication of chronic hepatitis C virus (HCV) infection. Among haemophilic (H) men, HCV is the leading cause of liver disease. Direct-acting antiviral agents (DAA) reduce HCV viral load, but impact on HCC is unknown. METHODS: This was a retrospective study of adult H and nonhaemophilic (NH) male discharges, with and without HCC, identified by ICD-10 codes in the National Inpatient Sample (NIS) database, 2016-2018, with DAA availability. Analyses included discharge-level weights to reflect national estimates. Categorical variables were assessed by Rao-Scott chi-square and continuous variables by weighted simple linear regression. HCC correlates were determined by weighted multivariable logistic regression. RESULTS: Among 7,674,969 adult male discharges, 3730 H (.04%) were identified in 2016-2018, of whom 10.06% had HCV and 1.07% had HCC, significantly higher than NH (1.22% and .27%, respectively) all P < .001. Annual HCC rates were similar during the 3-year period (2016-2018) in H and NH. Among H, HCC is associated with older age and higher rates of HCV, HBV, NASH, end-stage liver disease, and Charlson comorbidity (CCI), each P < .001. Among HCC, H were younger and more likely HIV+, each P < .001, but less likely alcoholic (P = .018) or hyperlipidaemic (P = .008) compared to NH. In multivariable regression, risk factors for HCC among H included NASH (OR 21.6), HCV (OR 3.96), CCI (OR1.54), all P < .001, while HIV and hyperlipidaemia were protective. CONCLUSION: From 2016 to 2018, HCC rates did not change significantly in haemophilia discharges. NASH, HCV, and CCI are significant risks for HCC in haemophilia during the DAA-era.

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.

Factor VIII concentrate dosing with lean body mass, ideal body weight and total body weight in overweight and obesity: A randomized, controlled, open-label, 3 × 3 crossover trial.

INTRODUCTION: Obesity alters the pharmacokinetic (PK) properties of drugs making it difficult to determine the appropriate dose when administering weight-based medications. Alternative descriptors of body weight, such as lean body mass (LBM) and ideal body weight (IBW), are sometimes used in these situations. METHODS: We performed a single-centre, randomized, controlled, open-label, 3 × 3 crossover trial to determine whether recombinant factor VIII (rFVIII) dosing based on LBM and IBW achieves a targeted FVIII recovery with better precision than based on total body weight (TBW) in overweight and obese, adult males with haemophilia A. Participants were randomized to 1 of 6 possible FVIII concentrate dosing sequence scenarios (TBW, LBM and IBW). Recombinant FVIII was administered on 3 separate weeks following a washout period of at least 72 hours. RESULTS: A total of 19 participants were randomized and completed the study. FVIII recovery was lower at 30 minutes post-rFVIII infusion in LBM vs TBW and IBW vs TBW-based dosing, mean difference -0.38 (95% CI: -0.56, -0.20) and -0.28 (95% CI: -0.47, -0.10) IU/dL per IU/kg, respectively. In LBM vs TBW and IBW vs TBW-based dosing, there was a non-significant increase in the proportion of participants with a targeted FVIII recovery of 2.00 ± 0.20 IU/dl per IU/kg, OR = 1.93 (95% CI: 0.44, 8.55) and OR = 3.65 (0.80, 16.72), respectively. DISCUSSION: Based on our study's findings, overweight and obese patients with haemophilia A may benefit from an individualized PK analysis using LBM and IBW to determine the most accurate, and potentially cost-effective, method of achieving targeted FVIII recovery.

Quality of periprocedural care in patients with von Willebrand disease.

INTRODUCTION: While it has been shown that haemophilia patients receiving care at Haemophilia Treatment Centres (HTCs) experience decreased morbidity and mortality, little research has been done on the outcomes of patients with von Willebrand disease (VWD). AIM: To compare the quality of periprocedural care received by patients with VWD at HTCs and non-HTCs. METHODS: We performed a retrospective chart review on all adult VWD patients undergoing an invasive procedure from 2015 to 2017. Quality of periprocedural care was measured using the following surrogate outcomes: periprocedural VWD-specific therapy use per 2007 National Heart, Lung, and Blood Institute (NHLBI) guidelines, procedural estimated blood loss (EBL), and post-procedure bleeding. Comparisons were performed according to the setting of care at the time of the invasive procedure, HTC versus non-HTC. RESULTS: There were 668 invasive procedures performed on 305 patients, of which 8.2% were HTC cases. Non-type 1 VWD was more likely in HTC cases. VWD-specific therapy was used per NHLBI guidelines in 100% of HTC cases compared with 10.6% of non-HTC cases. Procedural EBL > = 100 ml was more likely to occur in HTC differences cases (OR = 2.34; 95% CI, 1.05 to 5.25). There was no difference in post-procedure bleeding between the two groups (OR = 1.26, 95% CI, .20- 7.86). CONCLUSION: Despite widespread periprocedural use of VWD-specific therapy outside established guidelines at non-HTCs, there was no difference in periprocedural bleeding. Possible explanations include diagnostic error, in disease severity and procedure types, and dataset limitations. Additional studies are needed to investigate this further and compare other patient care outcomes between HTCs and non-HTCs.

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.

Long-Term Follow-Up of the First in Human Intravascular Delivery of AAV for Gene Transfer: AAV2-hFIX16 for Severe Hemophilia B.

Adeno-associated virus (AAV) vectors are a leading platform for gene-based therapies for both monogenic and complex acquired disorders. The success of AAV gene transfer highlights the need to answer outstanding clinical questions of safety, durability, and the nature of the human immune response to AAV vectors. Here, we present longitudinal follow-up data of subjects who participated in the first trial of a systemically delivered AAV vector. Adult males (n = 7) with severe hemophilia B received an AAV2 vector at doses ranging from 8 × 1010 to 2 × 1012 vg/kg to target hepatocyte-specific expression of coagulation factor IX; a subset (n = 4) was followed for 12-15 years post-vector administration. No major safety concerns were observed. There was no evidence of sustained hepatic toxicity or development of hepatocellular carcinoma as assessed by liver transaminase values, serum α-fetoprotein, and liver ultrasound. Subjects demonstrated persistent, increased AAV neutralizing antibodies (NAbs) to the infused AAV serotype 2 (AAV2) as well as all other AAV serotypes tested (AAV5 and AAV8) for the duration of follow-up. These data represent the longest available longitudinal follow-up data of subjects who received intravascular AAV and support the preliminary safety of intravascular AAV administration at the doses tested in adults. Data demonstrate, for the first time, the persistence of high-titer, multi-serotype cross-reactive AAV NAbs for up to 15 years post- AAV vector administration. Our observations are broadly applicable to the development of AAV-mediated gene therapy.

Targeting of Antithrombin in Hemophilia A or B with RNAi Therapy.

BACKGROUND: Current hemophilia treatment involves frequent intravenous infusions of clotting factors, which is associated with variable hemostatic protection, a high treatment burden, and a risk of the development of inhibitory alloantibodies. Fitusiran, an investigational RNA interference (RNAi) therapy that targets antithrombin (encoded by SERPINC1), is in development to address these and other limitations. METHODS: In this phase 1 dose-escalation study, we enrolled 4 healthy volunteers and 25 participants with moderate or severe hemophilia A or B who did not have inhibitory alloantibodies. Healthy volunteers received a single subcutaneous injection of fitusiran (at a dose of 0.03 mg per kilogram of body weight) or placebo. The participants with hemophilia received three injections of fitusiran administered either once weekly (at a dose of 0.015, 0.045, or 0.075 mg per kilogram) or once monthly (at a dose of 0.225, 0.45, 0.9, or 1.8 mg per kilogram or a fixed dose of 80 mg). The study objectives were to assess the pharmacokinetic and pharmacodynamic characteristics and safety of fitusiran. RESULTS: No thromboembolic events were observed during the study. The most common adverse events were mild injection-site reactions. Plasma levels of fitusiran increased in a dose-dependent manner and showed no accumulation with repeated administration. The monthly regimen induced a dose-dependent mean maximum antithrombin reduction of 70 to 89% from baseline. A reduction in the antithrombin level of more than 75% from baseline resulted in median peak thrombin values at the lower end of the range observed in healthy participants. CONCLUSIONS: Once-monthly subcutaneous administration of fitusiran resulted in dose-dependent lowering of the antithrombin level and increased thrombin generation in participants with hemophilia A or B who did not have inhibitory alloantibodies. (Funded by Alnylam Pharmaceuticals; ClinicalTrials.gov number, NCT02035605 .).

Hemophilia B Gene Therapy with a High-Specific-Activity Factor IX Variant.

BACKGROUND: The prevention of bleeding with adequately sustained levels of clotting factor, after a single therapeutic intervention and without the need for further medical intervention, represents an important goal in the treatment of hemophilia. METHODS: We infused a single-stranded adeno-associated viral (AAV) vector consisting of a bioengineered capsid, liver-specific promoter and factor IX Padua (factor IX-R338L) transgene at a dose of 5×1011 vector genomes per kilogram of body weight in 10 men with hemophilia B who had factor IX coagulant activity of 2% or less of the normal value. Laboratory values, bleeding frequency, and consumption of factor IX concentrate were prospectively evaluated after vector infusion and were compared with baseline values. RESULTS: No serious adverse events occurred during or after vector infusion. Vector-derived factor IX coagulant activity was sustained in all the participants, with a mean (±SD) steady-state factor IX coagulant activity of 33.7±18.5% (range, 14 to 81). On cumulative follow-up of 492 weeks among all the participants (range of follow-up in individual participants, 28 to 78 weeks), the annualized bleeding rate was significantly reduced (mean rate, 11.1 events per year [range, 0 to 48] before vector administration vs. 0.4 events per year [range, 0 to 4] after administration; P=0.02), as was factor use (mean dose, 2908 IU per kilogram [range, 0 to 8090] before vector administration vs. 49.3 IU per kilogram [range, 0 to 376] after administration; P=0.004). A total of 8 of 10 participants did not use factor, and 9 of 10 did not have bleeds after vector administration. An asymptomatic increase in liver-enzyme levels developed in 2 participants and resolved with short-term prednisone treatment. One participant, who had substantial, advanced arthropathy at baseline, administered factor for bleeding but overall used 91% less factor than before vector infusion. CONCLUSIONS: We found sustained therapeutic expression of factor IX coagulant activity after gene transfer in 10 participants with hemophilia who received the same vector dose. Transgene-derived factor IX coagulant activity enabled the termination of baseline prophylaxis and the near elimination of bleeding and factor use. (Funded by Spark Therapeutics and Pfizer; ClinicalTrials.gov number, NCT02484092 .).

Traumatic injury results in prolonged circulation of ultralarge von Willebrand factor and a reduction in ADAMTS13 activity.

BACKGROUND: Increases in plasma von Willebrand Factor (VWF) levels, accompanied by decreases in the metalloprotease ADAMTS13, have been demonstrated soon after traumatic injury while downstream effects remain unclear. STUDY DESIGN AND METHODS: A cohort of 37 injured trauma patients from a randomized control trial investigating the use of prehospital plasma transfusion were analyzed for activity and antigen levels of ADAMTS13 and VWF at 0 and 24 hours after admission. Relevant clinical data were abstracted from the medical records. Trauma patient plasma was analyzed via agarose gel electrophoresis to evaluate the effects of injury on VWF multimer composition compared to healthy controls. RESULTS: von Willebrand factor levels were elevated at presentation (189% [110%-263%] vs. 95% [74%-120%]), persisting through 24 hours (213% [146%-257%] vs. 132% [57%-160%]), compared to healthy controls. Ultralarge VWF (UL-VWF) forms were elevated in trauma patients at both 0 and 24 hours, when compared to pooled normal plasma (10.0% [8.9%-14.3%] and 11.3% [9.1%-21.2%], respectively, vs. 0.6%). Circulating plasma ADAMTS13 activity was decreased at 0 hours (66% [47%-86%] vs. 100% [98%-100%]) and at 24 hours (72.5% [56%-87.3%] vs. 103% [103%-103%]) in trauma patients. ADAMTS13 activity independently predicted the development of coagulopathy and correlated with international normalized ratio, thromboelastography values, injury severity, and blood product transfusion. CONCLUSION: Traumatic injury is associated with acute coagulopathy that is characterized by increased UL-VWF multimers and reduction in ADAMTS13, which correlates with blood loss, transfusion requirement, and injury severity. These findings suggest the potential for future trials targeting ADAMTS13 repletion to enhance clearance of VWF multimers.

Emicizumab prophylaxis in patients with haemophilia A with and without inhibitors.

INTRODUCTION: Emicizumab is a bispecific monoclonal antibody that mimics factor VIII (FVIII) by binding to factors IXa and X to promote hemostasis in haemophilia A (HA) and HA with inhibitors (HA-I). As emicizumab differs biochemically from FVIII, there is interest in its real-world haemostatic efficacy. AIM: To describe real-world patient experience with emicizumab by retrospective chart review. METHODS: We reviewed medical records of patients cared for at the Hemophilia Center of Western PA, who initiated emicizumab following its licensure, and on whom bleeding events and factor use were available. Comparisons between groups were done by Student's t test for continuous data and by chi-square or Fisher's exact test for discrete data. RESULTS: A total of 42 patients whose charts were reviewed included 18 (42.9%) with HA and 24 (52.1%) with HA-I. Groups were similar in age, 17 (40.5%) <18 years, race, and haemophilia severity, and initiated weekly subcutaneous emicizumab 1.5 mg/kg, following 4-week induction. Fourteen (33.3%) experienced at least one breakthrough bleed, of which 11 (44.0%) were joint bleeds, with an annualized bleed rate (ABR), 0.9 ± 0.3, not different between groups, P = .251. Surgical procedures were performed in 10 (23.8%), of whom 4 (40.0%) had postoperative bleeding and one developed postoperative thrombosis in association with FEIBA despite emicizumab discontinuation 1 month preoperatively. Local skin reactions occurred in three and headache in one. Overall, 85.0% of those who rated their health indicated it was improved. DISCUSSION: Despite breakthrough bleeds and postoperative thrombosis associated with emicizumab, most HA and HA-I experienced improved health.

The impact of extended half-life factor concentrates on prophylaxis for severe hemophilia in the United States.

With licensure of extended half-life (EHL) factor products and the changing landscape of available hemophilia products, patients and providers have options for less treatment-intense prophylaxis. The impact of these products in clinical practice to date remains understudied. We aimed to quantify the use of EHL products in prophylaxis in the US using the ATHN-dataset, a database of 145 ATHN-affiliated hemophilia treatment centers (HTCs). Further, we aimed to quantify the impact of EHL on key hemophilia indicators including annualized bleed rates (ABRs), hemophilia joint health scores (HJHS) and quality of life (QOL) metrics. The use of EHL vs standard half-life (SHL) products in severe hemophilia was compared between June 2018 and March 2019 using the ATHN-dataset. A cohort of patients was also recruited from seven participating HTCs in order to compare ABR, HJHS and QOL between product classes. By March 2019 the number of individuals with severe Hemophilia A (SHA) receiving EHLs remained relatively stable (28.4%), whereas the number of prescribed non-factor products increased to 7.1%, with a diminishing majority of patients (64.0%) continuing to receive SHLs. The majority of patients with severe hemophilia B (SHB) received treatment with EHLs including 57.5% by March 2019. There was a trend toward lower ABR with use of EHLs in SHA and SHB, although this did not result in improved HJHS nor QOL. EHL use in the United States in severe hemophilia continues to increase, although at a slower rate in SHA with the availability of non-factor therapy. The impact of the EHL therapies in clinical practice should continue to be examined prospectively.

The national blueprint for future factor VIII inhibitor clinical trials: NHLBI State of the Science (SOS) Workshop on factor VIII inhibitors.

INTRODUCTION: Inhibitor formation is a major complication of haemophilia for which clinical trials are planned. Despite emerging novel haemostatic agents, challenges of rare disease trials are limited subjects and lack of an organized research organization with strategic resources and partnerships. AIM: The charge to Working Group 1 was to establish scientific priorities and innovative implementation strategies to conduct inhibitor prevention and eradication trials. To determine feasibility of trial design and strategic resources and partnerships to be leveraged, two clinical trial concepts were considered. RESULTS: For the Inhibitor Prevention Trial, we considered adaptive design with early stopping rules, dynamic randomization and Master Protocol models to reduce sample size; and registries to provide concurrent controls and natural history data. For the Inhibitor Eradication Trial using gene therapy, an adaptive design was considered in a small number of subjects, and, if safe and meeting regulatory requirements, enrolment would be expanded. A Haemophilia Clinical Trials Group (HCTG) infrastructure was envisioned, with uniform procedures and standardized outcomes, data collection and assays, within which trial concepts would be developed, vetted and prioritized by a Steering Committee, and submitted to NIH and other research sponsors for review and funding. Mechanistic studies would be embedded within the trials, early stage investigators trained and mentored, and the research infrastructure established within the haemophilia centre (HTC) network and supported by partnerships with foundations, community, federal partners and industry. CONCLUSION: The success of inhibitor trials will depend on innovative trial design and an organized HCTG research infrastructure, leveraged through community partnerships.

Incidence and risk factors for hepatocellular cancer in individuals with haemophilia: A National Inpatient Sample Study.

INTRODUCTION: Among haemophilic (H) men, hepatitis C virus (HCV) is the leading cause of liver disease and mortality, but demographics and risks of hepatocellular carcinoma (HCC) in H are not well known. METHODS: Adult discharges in H and non-haemophilic (NH) men, with and without HCC were identified in the National Inpatient Sample (NIS) between 1998 and 2014, using ICD-9 codes. Analyses included NIS-provided discharge-level weights to reflect national estimates. Categorical variables were assessed by Rao-Scott chi-square and continuous variables by weighted simple linear regression. HCC predictors were determined by weighted multivariable logistic regression. RESULTS: Of 18 098 H, 144 (0.79%) had HCC between 1998 and 2014. Adjusted rates of HCC increased 3.0-fold in H vs 1.7-fold in NH (P = 0.484). Among HCV+, HCC rates adjusted for HIV, increased 2.2-fold in H vs 1.7-fold in NH (P = 0.740), while among HIV+, HCC increased 1.4-fold in H vs 0.2-fold in NH (P = 0.448). Among those with HCC, H were older than NH (P < 0.001), Caucasian (P = 0.006), platelet transfusion recipients (P < 0.001), with greater comorbidity (P < 0.001) and mortality (P < 0.006). H with HCC also had greater rates of HCV and HIV (each P < 0.001), lower rates of alcoholism and hyperlipidemia (each P < 0.001), and similar rates of HBV (P = 0.866), smoking (P = 0.507) and obesity (P = 0.502). In multivariable logistic regression, HCV was a strong predictor for HCC in haemophilia, (OR: 15.42, 95% CI: 8.75-27.16). DISCUSSION: Haemophilic men have increasing rates of HCC, similar to men without haemophilia. HCV is the major predictor of HCC in haemophilia. Future trends in HCC will depend on the impact of newer HCV antiviral therapy.

Platelet VIII pack evades immune detection.

In this issue of Blood, Chen et al demonstrate that platelets expressing factor VIII (FVIII) shield FVIII from immune detection. In the naive FVIII null hemophilia A (HA) mouse, platelet-derived VIII prevents both a primary and memory anti-FVIII immune response, and together with total body irradiation, suppresses anti-FVIII immune response.

Clinical and laboratory variability in a cohort of patients diagnosed with type 1 VWD in the United States.

von Willebrand disease (VWD) is the most common inherited bleeding disorder, and type 1 VWD is the most common VWD variant. Despite its frequency, diagnosis of type 1 VWD remains the subject of debate. In order to study the spectrum of type 1 VWD in the United States, the Zimmerman Program enrolled 482 subjects with a previous diagnosis of type 1 VWD without stringent laboratory diagnostic criteria. von Willebrand factor (VWF) laboratory testing and full-length VWF gene sequencing was performed for all index cases and healthy control subjects in a central laboratory. Bleeding phenotype was characterized using the International Society on Thrombosis and Haemostasis bleeding assessment tool. At study entry, 64% of subjects had VWF antigen (VWF:Ag) or VWF ristocetin cofactor activity below the lower limit of normal, whereas 36% had normal VWF levels. VWF sequence variations were most frequent in subjects with VWF:Ag <30 IU/dL (82%), whereas subjects with type 1 VWD and VWF:Ag ≥30 IU/dL had an intermediate frequency of variants (44%). Subjects whose VWF testing was normal at study entry had a similar rate of sequence variations as the healthy controls (14%). All subjects with severe type 1 VWD and VWF:Ag ≤5 IU/dL had an abnormal bleeding score (BS), but otherwise BS did not correlate with VWF:Ag. Subjects with a historical diagnosis of type 1 VWD had similar rates of abnormal BS compared with subjects with low VWF levels at study entry. Type 1 VWD in the United States is highly variable, and bleeding symptoms are frequent in this population.

Prophylactic rtPA in the Prevention of Line-associated Thrombosis and Infection in Short Bowel Syndrome.

BACKGROUND: Central venous access devices (CVADs) are essential for total parenteral nutrition administration in patients with short bowel syndrome (SBS). They are, however, fraught with complications including infection and venous thromboembolism (VTE), which increases associated morbidity and mortality in this population. There is evidence linking the development of CVAD-associated thrombosis and line-related infection. Thus, it has been postulated that prevention of catheter-related clot formation could minimize the risk of infection originating from the catheter. Recombinant tissue plasminogen activator (rtPA, alteplase), lyses clots by binding plasmin-bound fibrin in a clot and cleaving plasminogen to plasmin; moreover, it is widely used to clear occluded CVADs. METHODS: Prophylactic rtPA lock therapy in children with SBS was evaluated as a single site pilot study to minimize line-associated VTE, infection, need for line replacement, and hospitalization at the Children's Hospital of Pittsburgh of University of Pittsburgh Medical Center. rtPA lock therapy was administered by parents/caregivers on a weekly basis over a 6-month time period in place of heparin lock therapy. Comparisons were made between line-associated complications in the cohort in the 6 months before study versus during the study period. RESULTS: Six out of 8 subjects completed the study over a 1-year time period. As a group, subjects experienced a significant decrease in the number of line-associated bloodstream infections from a mean of 1.9 infections in the 6 months before the study to a mean of 0.5 infections (P = 0.025). There was no change in the need for line replacement amongst subjects while on study. The primary outcome of VTE was not found in the cohort, and it is unclear whether rtPA lock therapy contributed to the lack of thrombosis development. Given the success of rtPA in this pilot study in reducing bloodstream infections, further investigation or rtPA lock therapy in patients with SBS is warranted.