T6SS-effector hunters uncover PIX: a novel delivery/marker domain

Gram-negative bacteria use the T6SS to eject effectors into prey cells, aided by delivery domains. Recently uncovered by Carobbi et al., a new delivery domain, PIX, allowed the identification of hundreds of new effectors. They are order- and function-specific and exclusively orphan effectors, raising novel questions in the field.

Excellent hemostatic control during cardiac surgery in a patient with hemophilia B treated with albutrepenonacog alfa (rIX-FP): A case report

Key Clinical Message

In hemophilia patients undergoing cardiac surgery, ROTEM® and Quantra® viscoelastic tests are useful to monitor perioperative hemostatic status and a single dose of rIX-FP is safe and avoids any hemorrhagic or thrombotic complication.

Abstract

Cardiac surgery poses a high hemostatic risk in patients with hemophilia. We present the first case of an adult patient with hemophilia B on treatment with albutrepenonacog alfa (rIX-FP) who underwent surgery for acute coronary syndrome. Treatment with rIX-FP made it possible to perform the surgery safely.

Oral tolerance to prevent anti-drug antibody formation in protein replacement therapies

Protein based therapeutics have successfully improved the quality of life for patients of monogenic disorders like hemophilia, Pompe and Fabry disease. However, a significant proportion of patients develop immune responses towards intravenously infused therapeutic protein, which can complicate or neutralize treatment and compromise patient safety. Strategies aimed at circumventing immune responses following therapeutic protein infusion can greatly improve therapeutic efficacy. In recent years, antigen-based oral tolerance induction has shown promising results in the prevention and treatment of autoimmune diseases, food allergies and can prevent anti-drug antibody formation to protein replacement therapies. Oral tolerance exploits regulatory mechanisms that are initiated in the gut associated lymphoid tissue (GALT) to promote active suppression of orally ingested antigen. In this review, we outline general perceptions and current knowledge about the mechanisms of oral tolerance, including tissue specific sites of tolerance induction and the cells involved, with emphasis on antigen presenting cells and regulatory T cells. We define several factors, such as cytokines and metabolites that impact the stability and expansion potential of these immune modulatory cells. We highlight preclinical studies that have been performed to induce oral tolerance to therapeutic proteins or enzymes for single gene disorders, such as hemophilia or Pompe disease. These studies mainly utilize a transgenic plant-based system for oral delivery of antigen in conjugation with fusion protein technology that favors the prevention of antigen degradation in the stomach while enhancing uptake in the small intestine by antigen presenting cells and regulatory T cell induction, thereby promoting antigen specific systemic tolerance.

Long-term correction of hemophilia B through CRISPR/Cas9 induced homology-independent targeted integration

CRISPR/Cas9-mediated site-specific insertion of exogenous genes holds potential for clinical applications. However, it is still infeasible because homologous recombination (HR) is inefficient, especially for non-dividing cells. To overcome the challenge, we report that a homology-independent targeted integration (HITI) strategy is used for permanent integration of high-specificity-activity Factor IX variant (F9 Padua, R338L) at the albumin (Alb) locus in a novel hemophilia B (HB) rat model. The knock-in efficiency reaches 3.66%, as determined by droplet digital PCR (ddPCR). The clotting time is reduced to a normal level four weeks after treatment, and the circulating factor IX (FIX) level is gradually increased up to 52% of the normal level over nine months even after partial hepatectomy, demonstrating the amelioration of hemophilia. Through primer-extension-mediated sequencing (PEM-seq), no significant off-target effect is detected. This study not only provides a novel model for HB but also identifies a promising therapeutic approach for rare inherited diseases.

A comparison of multiband and multiband multiecho gradient-echo EPI for task fMRI at 3 T

A multiband (MB) echo-planar imaging (EPI) sequence is compared to a multiband multiecho (MBME) EPI protocol to investigate differences in sensitivity for task functional magnetic resonance imaging (fMRI) at 3 T. Multiecho sampling improves sensitivity in areas where single-echo-EPI suffers from dropouts. However, It requires in-plane acceleration to reduce the echo train length, limiting the slice acceleration factor and the temporal and spatial resolution Data were acquired for both protocols in two sessions 24 h apart using an adapted color-word interference Stroop task. Besides protocol comparison statistically, we performed test-retest reliability across sessions for different protocols and denoising methods. We evaluated the sensitivity of two different echo-combination strategies for MBME-EPI. We examined the performance of three different data denoising approaches: "Standard," "AROMA," and "FIX" for MB and MBME, and assessed whether a specific method is preferable. We consider using an appropriate autoregressive model order within the general linear model framework to correct TR differences between the protocols. The comparison between protocols and denoising methods showed at group level significantly higher mean z-scores and the number of active voxels for MBME in the motor, subcortical and medial frontal cortices. When comparing different echo combinations, our results suggest that a contrast-to-noise ratio weighted echo combination improves sensitivity in MBME compared to simple echo-summation. This study indicates that MBME can be a preferred protocol in task fMRI at spatial resolution (≥2 mm), primarily in medial prefrontal and subcortical areas.

The important impact of dental care on haemostatic treatment burden in patients with mild haemophilia

BACKGROUND

Mild haemophilia (MH) is mainly characterized by haemorrhages secondary to surgery/invasive procedures or trauma. Haemostatic treatment in MH ranges from on demand to short prophylaxis according to the type of bleeding events and the basal clotting factor level. Oral surgery and dental extractions can represent a frequent haemostatic challenge in MH requiring appropriate treatment. However, only few studies on limited numbers of patients are available in the literature regarding the implications of dental management in patients with MH.

OBJECTIVES

The purpose of the study was to evaluate the impact of dental care on the burden of haemostatic treatment in patients affected by MH.

METHODS

We conducted a retrospective multicentre study evaluating adult patients with MH regularly examined at the Haemophilia Treatment Centres (HTCs) of the Saint-Luc University Hospital, Brussels (Belgium) and of Paolo Giaccone Hospital, Palermo (Italy). The population consisted of 107 male patients with MH, with a mean age of 39 years (range 18-81 years).

RESULTS

The majority of patients (86/107, 79%) needed at least one treatment within the study period, and 44% (38/86) of them received haemostatic therapy for dental care. Haemostatic therapy in our study varied from antifibrinolytic therapy alone and perioperative factor replacement to the absence of treatment at all. The great majority of oral interventions (27/42, 64%) were managed with clotting factor concentrate.

CONCLUSION

This study demonstrates that dental care currently represents a major reason for haemostatic treatments in patients with MH. Maintaining good oral health appears as a priority to minimize avoidable replacement therapy and optimize resources.

Molecular therapeutics of Hemophilia A and B

INTRODUCTION

Hemophilia A (HA) or B (HB) is an X-linked recessive disorder caused by a defect in the factor VIII (FVIII) or factor IX (FIX) gene which leads to the dysfunction of blood coagulation. Protein replacement therapy (PRT) uses recombinant proteins and plasma-derived products, which incurs high cost and inconvenience requiring routine intravenous infusions and life-time treatment. Understanding of detailed molecular mechanisms on FVIII gene function could provide innovative solutions to amend this disorder. In recent decades, gene therapeutics have advanced rapidly and a one-time cure solution has been proposed.

AREAS COVERED

This review summarizes current understanding of molecular pathways involved in blood coagulation, with emphasis on FVIII's functional role. The existing knowledge and challenges on FVIII gene expression, from transcription, translation, post-translational modification including glycosylation to protein processing and secretion, and co-factor interactions are deciphered and potential molecular interventions discussed.

EXPERT OPINION

This article reviews the potential treatment targets for HA and HB, including antibodies, small molecules and gene therapeutics, based on molecular mechanisms of FVIII biosynthesis, and further, assessing the pros and cons of these various treatment strategies. Understanding detailed FVIII protein synthesis and secretory pathways could provide exciting opportunities in identifying novel therapeutics to ameliorate hemophilia state.

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.

A multi-measure approach for assessing the performance of fMRI preprocessing strategies in resting-state functional connectivity

It is well established that head motion and physiological processes (e.g. cardiac and breathing activity) should be taken into consideration when analyzing and interpreting results in fMRI studies. However, even though recent studies aimed to evaluate the performance of different preprocessing pipelines there is still no consensus on the optimal strategy. This is partly due to the fact that the quality control (QC) metrics used to evaluate differences in performance across pipelines have often yielded contradictory results. Furthermore, preprocessing techniques based on physiological recordings or data decomposition techniques (e.g. aCompCor) have not been comprehensively examined. Here, to address the aforementioned issues, we propose a framework that summarizes the scores from eight previously proposed and novel QC metrics to a reduced set of two QC metrics that reflect the signal-to-noise ratio and the reduction in motion artifacts and biases in the preprocessed fMRI data. Using this framework, we evaluate the performance of three commonly used practices on the quality of data: 1) Removal of nuisance regressors from fMRI data, 2) discarding motion-contaminated volumes (i.e., scrubbing) before regression, and 3) low-pass filtering the data and the nuisance regressors before their removal. Using resting-state fMRI data from the Human Connectome Project, we show that the scores of the examined QC metrics improve the most when the global signal (GS) and about 17% of principal components from white matter (WM) are removed from the data. Finally, we observe a small further improvement with low-pass filtering at 0.20 Hz and milder variants of WM denoising, but not with scrubbing.

Gene therapy for hemophilia: Current status and laboratory consequences

Since the cloning and characterization of the factor VIII (FVIII) and factor IX genes in the mid-1980s, gene therapy has been perceived as having significant potential for the treatment of severe hemophilia. Now, some 35 years later, these proposals are close to being realized through the licensing of the first clinical gene therapy product. Adeno-associated viral vector-mediated gene therapy for hemophilia A and B has been extensively investigated in preclinical models over the past 20 years, and since 2011, there has been increasing evidence in early phase clinical trials that this therapeutic strategy can provide safe and effective rescue of the hemostatic phenotype in severe hemophilia. As the uptake of hemophilia gene therapy progresses, it is clear that many aspects of the gene therapy process require crucial laboratory support to ensure safe and effective outcomes from his new therapeutic paradigm. These laboratory contributions extend from evaluations of the gene therapy vehicle, assessments of the patient immune status for the vector, and ultimately the performance of assays to determine the hemostatic benefit of the gene therapy and potentially of its long-term safety on the host genome. As with many aspects of past hemophilia care, the safe and effective delivery of gene therapy will require an informed and coordinated contribution from laboratory science.

Adult lifetime cost of hemophilia B management in the US: payer and societal perspectives from a decision analytic model

AIMS

Hemophilia B (HB) is a rare congenital disorder characterized by bleeding-related complications which are managed by prophylactic or post-bleeding event ("on-demand") replacement of clotting factor IX (FIX). The standard of care for severe HB is life-long prophylaxis with standard half-life (SHL) or extended half-life (EHL) products given every 2-3 or 7-14 days, respectively. FIX treatment costs in the US have been investigated, but the lifetime costs of HB treatment have not been well characterized, particularly related to the impact of joint health deterioration and associated health resource utilization. We developed a decision-analytic model to explore outcomes, costs and underlying cost drivers associated with FIX treatment options over the lifetime of an adult with severe or moderately severe HB.

MATERIALS AND METHODS

With participation from clinicians, health technology assessment specialists and patient advocates, a Markov model was constructed to estimate bleeding events and costs associated with health states including "bleed into joint", "bleed not into joint", "no bleed" and "death". Sub-models of joint health were based on 0, 1, or ≥2 areas of chronic joint damage. US third-party payer and societal perspectives were considered with a lifetime horizon; sensitivity analyses tested the robustness of primary findings.

RESULTS

Total adult lifetime costs per patient with severe and moderately severe HB were $21,086,607 for SHL FIX prophylaxis, $22,987,483 for EHL FIX prophylaxis, and $20,971,826 for on-demand FIX treatment. For FIX prophylaxis, the cost of FIX treatment accounts for >90% of the total HB treatment costs.

CONCLUSIONS

This decision analytic model demonstrated significant economic burden associated with the current HB treatment paradigm.

Prevalence and Incidence of Non-neutralizing Antibodies in Congenital Hemophilia A- A Systematic Review and Meta-Analysis

Objectives: In hemophilia A the presence of non-neutralizing antibodies (NNAs) against Factor VIII (FVIII) may predict the development of neutralizing antibodies (inhibitors) and accelerate the clearance of administrated FVIII concentrates. This systematic review aimed to assess: (1) the prevalence and incidence of NNAs in patients with congenital hemophilia without inhibitors and (2) the association between NNAs and patient and treatment characteristics.

Methods: We conducted a search in MEDLINE, Embase, Web of Science and the Cochrane database. We included cross-sectional and longitudinal studies reporting on NNAs in patients with hemophilia A and B, who were inhibitor-negative at the start of the observation period. Data were extracted on: hemophilia type and severity, patient and treatment characteristics, NNA prevalence and incidence, NNA assays and inhibitor development. Two independent reviewers performed study selection, data extraction and risk of bias assessment, using adapted criteria of the Joanna Briggs Institute. Studies were classified as high-quality when ≥5/9 criteria were met. NNA assays were classified as high-quality when both quality criteria were met: (1) use of positive controls and (2) competition with FVIII to establish FVIII-specificity. We reported NNA prevalence and incidence for each study. The pooled NNA prevalence was assessed for well-designed studies in previously treated patients, employing high-quality NNA assays.

Results: We included data from 2,723 inhibitor-negative patients with hemophilia A, derived from 28 studies. Most studies were cross-sectional (19/28) and none reported on NNAs in hemophilia B. Study design was of high quality in 16/28 studies and the NNA assay quality was high in 9/28 studies. Various NNA assays were used, predominantly ELISA (18/28) with different cut-off values. We found a large variety in NNA prevalence (Range, 0–100%). The pooled NNA prevalence in high-quality studies was 25% (95% CI, 16–38%). The incidence of new NNA development was reported in one study (0.01 NNA per person-exposure day).

Conclusion: This systematic review identified studies that were heterogeneous in study design, patient population and NNA assay type, with NNA prevalence ranging from 0 to 100% in inhibitor-negative patients with hemophilia A. The pooled NNA prevalence was 25% in high-quality studies including only previously treated patients and performing high-quality NNA assays.

Therapeutic hFIX Activity Achieved after Single AAV5-hFIX Treatment in Hemophilia B Patients and NHPs with Pre-existing Anti-AAV5 NABs

Currently, individuals with pre-existing neutralizing antibodies (NABs) against adeno-associated virus (AAV) above titer of 5 are excluded from systemic AAV-based clinical trials. In this study we explored the impact of pre-existing anti-AAV5 NABs on the efficacy of AAV5-based gene therapy. AMT-060 (AAV5-human FIX) was evaluated in 10 adults with hemophilia B who tested negative for pre-existing anti-AAV5 NABs using a GFP-based assay. In this study, using a more sensitive luciferase-based assay, we show that 3 of those 10 patients tested positive for anti-AAV5 NABs. However, no relationship was observed between the presence of pre-treatment anti-AAV5 NABs and the therapeutic efficacy of AMT-060. Further studies in non-human primates (NHPs) showed that AAV5 transduction efficacy was similar following AMT-060 treatment, irrespective of the pre-existing anti-AAV5 NABs titers. We show that therapeutic efficacy of AAV5-mediated gene therapy was achieved in humans with pre-existing anti-AAV5 NABs titers up to 340. Whereas in NHPs circulating human factor IX (hFIX) protein was achieved, at a level therapeutic in humans, with pre-existing anti-AAV5 NABs up to 1030. Based on those results, no patients were excluded from the AMT-061 (AAV5-hFIX-Padua) phase IIb clinical trial (n = 3). All three subjects presented pre-existing anti-AAV5 NABs, yet had therapeutic hFIX activity after AMT-061 administration.

Variants in FIX propeptide associated with vitamin K antagonist hypersensitivity: functional analysis and additional data confirming the common founder mutations

One of the most common and unwanted side effects during oral anticoagulant therapy (OAT) is bleeding complications. In rare cases, vitamin K antagonist (VKA)-related bleeding events are associated with mutations affecting the F9 propeptide at amino acid position 37 due to a substitution of alanine to either valine or threonine. Based on our actual cohort of 18 patients, we update the knowledge on this rare phenotype and its origin. A founder mutation for both variants was reconfirmed by haplotype analysis of intronic and extragenic short tandem repeat (STR) polymorphisms with a higher prevalence in Switzerland than in other regions of Europe. Screening of healthy individuals for the presence of these F9 gene mutations did not identify any of these variants, thus proving the rare occurrence of this genotype. Furthermore, both variants were expressed in vitro and warfarin dose responses were studied. Our warfarin dose response analysis confirmed higher sensitivity of both variants to warfarin with the effect being more apparent for Ala37Thr. Thus, although F9 propeptide mutation-associated hypersensitivity to VKA is a rare phenomenon, awareness towards this bleeding phenotype is important to identify patients at risk.

Platelet-Targeted Gene Therapy for Hemophilia

Gene therapy is an attractive approach for disease treatment. Since platelets are abundant cells circulating in blood with the distinctive abilities of storage and delivery and fundamental roles in hemostasis and immunity, they could be a unique target for gene therapy of diseases. Recent studies have demonstrated that ectopic expression of factor VIII (FVIII) in platelets under control of the platelet-specific promoter results in FVIII storage together with its carrier protein von Willebrand factor (VWF) in α-granules and the phenotypic correction of hemophilia A. Importantly, the storage and sequestration of FVIII in platelets appears to effectively restore hemostasis even in the presence of functional-blocking inhibitory antibodies. This review summarizes studies on platelet-specific gene therapy of hemophilia A as well as hemophilia B.

A multianalytical approach to investigate the effect of nanofiltration on plasma-derived factor IX clinical lots

Plasma-derived proteins are a subset of relevant biotherapeutics also known as "well-characterized biologicals". They are enriched from plasma through several steps of physical and biochemical methodologies, reaching the regulatory accepted standards of safety, levels of impurities, activity and lot-to-lot consistency. Final products accepted for commercialization are submitted to tight analytical, functional and safety controls by a number of different approaches that fulfill the requirements of sensitivity and reliability. We report here the use of a multianalytical approach for the comparative evaluation of different lots of Factor IX isolated from plasma preparations and submitted or not to a step of nanofiltration. The approach include, among the other, proteomic techniques based on both MALDI-TOF and LC-MS Orbitrap mass spectrometry, circular dichroism for structural characterization, chromatographic and electrophoretic techniques, ELISA and functional assays based on clotting activity and binding to known anticoagulants. Comparative data obtained on two sets of nanofiltered and non-nanofiltered lots with different final activity show that the products have substantially overlapping profiles in terms of activity, contaminants, structural properties and protein content, suggesting that the proposed multianalytical approach is robust enough to be used for the routine validation of clinical lots.

The Prognostic Implications of FIX and FLO Patterns in Mucinous Colon Carcinomas

PURPOSE

Colon mucinous carcinomas (MUCs) have two morphological patterns: (i) glands lined by mucinous epithelium with direct contact to the stroma (FIX) and (ii) carcinoma cells floating in mucin (FLO). In this study, we evaluated the prognostic value of these patterns.

METHODS

Digital images were captured from the 38 MUC's tissue sections. A grid with 140 points was laid over the computer screen. Totally, 100 points, falling on tumor cells floating in mucin (FLO patterned cells) or on cells contacting stroma (FIX patterned cells), were counted. Tumors were grouped according to the median value of the FIX patterned cells. Cases with more than this value were grouped as FIX and less were grouped as FLO cases. The prognostic value of FIX and FLO pattern was evaluated.

RESULTS

The median for FIX patterned cells was 66%, and the cases with lower values than this were grouped as FLO (N = 18; 47.37%), while the rest were grouped as FIX cases. There was no significant difference between FIX and FLO cases for overall survival cases (p = 0.167). For FIX cases, 62.7 and 51.3% of the patients were alive at second and third years, while this was 78.9 and 72.4% for the FLO group, respectively.

CONCLUSIONS

This is the first study using a quantitative methodology depending on count pointing to evaluate FIX/FLO feature of MUCs to the best of our knowledge, although we could not observed any prognostic and clinicopathologic relationship statistically. This distinctive feature should be studied in larger cohorts with prognostic information, with a quantitative method, like the one that was applied in this study, in order to achieve strict conclusions.

Continuous prophylaxis with recombinant factor IX Fc fusion protein and conventional recombinant factor IX products: comparisons of efficacy and weekly factor consumption

BACKGROUND

Continuous prophylaxis for patients with hemophilia B requires frequent injections that are burdensome and that may lead to suboptimal adherence and outcomes. Hence, therapies requiring less-frequent injections are needed. In the absence of head-to-head comparisons, this study compared the first extended-half-life-recombinant factor IX (rFIX) product-recombinant factor IX Fc fusion protein (rFIXFc)-with conventional rFIX products based on annualized bleed rates (ABRs) and factor consumption reported in studies of continuous prophylaxis.

METHODS

This study compared ABRs and weekly factor consumption rates in clinical studies of continuous prophylaxis treatment with rFIXFc and conventional rFIX products (identified by systematic literature review) in previously-treated adolescents and adults with moderate-to-severe hemophilia B. Meta-analysis was used to pool ABRs reported for conventional rFIX products for comparison. Comparisons of weekly factor consumption were based on the mean, reported or estimated from the mean dose per injection.

RESULTS

Five conventional rFIX studies (injections 1 to >3 times/week) met the criteria for comparison with once-weekly rFIXFc reported by the B-LONG study. The pooled mean ABR for conventional rFIX was slightly higher than but comparable to rFIXFc (difference=0.71; p = 0.210). Weekly factor consumption was significantly lower with rFIXFc than in conventional rFIX studies (difference in means = 42.8-74.5 IU/kg/week [93-161%], p < 0.001).

CONCLUSION

Comparisons of clinical study results suggest weekly injections with rFIXFc result in similar bleeding rates and significantly lower weekly factor consumption compared with more-frequently-injected conventional rFIX products. The real-world effectiveness of rFIXFc may be higher based on results from a model of the impact of simulated differences in adherence.

Extravascular FIX and coagulation

This review summarizes the evidence that collagen IV binding is physiologically important, and that the extravascular compartment of FIX is composed of type IV collagen. As we have previously demonstrated, 7 days post-infusion, FIX_WT (BeneFIX) is able to control bleeding as well as the same dosage of Alprolix in hemophilia B mice, tested using the saphenous vein bleeding model (Alprolix is a chimeric FIX molecule joined at its C terminus to a Fc domain). Furthermore, we have shown that in hemophilia B mice, doses of BeneFIX or Alprolix (up to a dose of 150 IU/kg) have increased bleeding-control effectiveness in proportion to the dose up to a certain limit: higher doses are no more effective than the 150 IU/kg dose. These studies suggest that in hemophilia B mice, tested using the saphenous vein bleeding model, three things are true: first, extravascular FIX is at least as important for coagulation as is circulating FIX; second, measuring circulating levels of FIX may not be the best criterion for designing new “longer lasting” FIX molecules; and third, trough levels are less diagnostic for FIX therapy than they are for FVIII therapy.

Recombinant long-acting glycoPEGylated factor IX (nonacog beta pegol) in haemophilia B: assessment of target joints in multinational phase 3 clinical trials

BACKGROUND

The paradigm(™) 2 and 4 phase 3 clinical trials investigated the safety and efficacy of nonacog beta pegol, a recombinant glycoPEGylated factor IX (FIX) with extended half-life, in previously treated haemophilia B patients.

AIM

These post hoc analyses investigated the bleeding patterns in target joints.

METHODS

Patients randomized to 40 or 10 IU kg(-1) once weekly prophylaxis who had at least one target joint were included. Baseline demographics and disease-specific data were collected. Bleeding patterns were assessed, and an International Society on Thrombosis and Haemostasis (ISTH) definition of target joints was used.

RESULTS

A total of 67% and 8% of patients in the 40 and 10 IU kg(-1) arm, respectively, did not experience target joint bleeds during the paradigm(™) 2 trial. Twenty-four target joints were recorded in each prophylaxis arm at baseline. During the paradigm(™) 2 trial, no bleeds were reported in 17 (71%) and 7 (29%) target joints in the 40 and 10 IU kg(-1) arms respectively. All target joint bleeds in the 40 IU kg(-1) once weekly prophylaxis arm were controlled with a single injection of 40 IU kg(-1) nonacog beta pegol. By the latest ISTH definition, 90% and 58% of target joints in the 40 and 10 IU kg(-1) arms, respectively, were no longer considered target joints at the end of the paradigm(™) 2 trial. At the end of the paradigm(™) 4 extension trial, all target joints in the 40 IU kg(-1) arm were no longer considered target joints.

CONCLUSION

Routine prophylaxis with 40 IU kg(-1) once weekly nonacog beta pegol has the potential for effective management of target joint bleeds in haemophilia B patients.

Enhanced effect of inhibition of thrombin on endothelium in murine endotoxaemia: specific inhibition of thrombocytopenia

INTRODUCTION

In systemic endotoxaemia, bacterial lipopolysaccharide causes the rapid expression of tissue factor (TF) and disseminated intravascular coagulation and in animal models, anticoagulants limit pathology and promote survival. Recent studies have emphasised the importance of TF expressed by mononuclear cells for initiating thrombin generation during endotoxaemia and suggested that endothelial cell TF is of little relevance. However, the precise importance of endothelium for intravascular thrombin generation has not been established. In this study, we compared the effect of equivalent levels of hirudin tethered to either endothelium or platelets and monocytes.

MATERIALS AND METHODS

CD31-Hir-Tg mice express a vesicle-targeted, membrane-tethered hirudin fusion protein on endothelium, platelets and monocytes. Bone marrow chimeras between these mice and C57BL/6 were generated The level of intravascular hirudin expressed during endotoxaemia was quantified by inhibition studies using an anti-hirudin antibody and reference to the circulating thrombin anti-thrombin complexes generated in control mice given soluble hirudin.

RESULTS AND CONCLUSIONS

Antibody inhibition studies indicated that individual chimeras expressed similar levels of hirudin fusion protein on endothelium alone as on platelets and leukocytes combined and accordingly, the levels of thrombin anti-thrombin complexes and fibrinogen in each chimera were similar, indicating equivalent inhibition of thrombin generation. However, mice with hirudin on endothelium alone developed significantly less thrombocytopenia. These results suggest a hitherto unrecognized role of endothelium in thrombin-dependent platelet sequestration during endotoxaemia. The data have implications for the development of therapeutic strategies based on targeted anticoagulation to limit disseminated intravascular coagulation.

Fusion protein linkers: property, design and functionality

As an indispensable component of recombinant fusion proteins, linkers have shown increasing importance in the construction of stable, bioactive fusion proteins. This review covers the current knowledge of fusion protein linkers and summarizes examples for their design and application. The general properties of linkers derived from naturally-occurring multi-domain proteins can be considered as the foundation in linker design. Empirical linkers designed by researchers are generally classified into 3 categories according to their structures: flexible linkers, rigid linkers, and in vivo cleavable linkers. Besides the basic role in linking the functional domains together (as in flexible and rigid linkers) or releasing the free functional domain in vivo (as in in vivo cleavable linkers), linkers may offer many other advantages for the production of fusion proteins, such as improving biological activity, increasing expression yield, and achieving desirable pharmacokinetic profiles.