Optimal treatment strategies for hemophilia: achievements and limitations of current prophylactic regimens

Physical Activity Monitoring and Acceptance of a Commercial Activity Tracker in Adult Patients with Haemophilia

Physical activity (PA) is highly beneficial for people with haemophilia (PWH), however, studies that objectively monitor the PA in this population are scarce. This study aimed to monitor the daily PA and analyse its evolution over time in a cohort of PWH using a commercial activity tracker. In addition, this work analyses the relationship between PA levels, demographics, and joint health status, as well as the acceptance and adherence to the activity tracker. Twenty-six PWH were asked to wear a Fitbit Charge HR for 13 weeks. According to the steps/day in the first week, data were divided into two groups: Active Group (AG; ≥10,000 steps/day) and Non-Active Group (NAG; <10,000 steps/day). Correlations between PA and patient characteristics were studied using the Pearson coefficient. Participants' user experience was analysed with a questionnaire. The 10,000 steps/day was reached by 57.7% of participants, with 12,603 (1525) and 7495 (1626) being the mean steps/day of the AG and NAG, respectively. In general, no significant variations (p > 0.05) in PA levels or adherence to wristband were produced. Only the correlation between very active minutes and arthropathy was significant (r = -0.40, p = 0.045). Results of the questionnaire showed a high level of satisfaction. In summary, PWH are able to comply with the PA recommendations, and the Fitbit wristband is a valid tool for a continuous and long-term monitoring of PA. However, by itself, the use of a wristband is not enough motivation to increase PA levels.

TAFI deficiency causes maladaptive vascular remodeling after hemophilic joint bleeding

Excessive vascular remodeling is characteristic of hemophilic arthropathy (HA) and may contribute to joint bleeding and the progression of HA. Mechanisms for pathological vascular remodeling after hemophilic joint bleeding are unknown. In hemophilia, activation of thrombin-activatable fibrinolysis inhibitor (TAFI) is impaired, which contributes to joint bleeding and may also underlie the aberrant vascular remodeling. Here, hemophilia A (factor VIII-deficient; FVIII-deficient) mice or TAFI-deficient mice with transient (antibody-induced) hemophilia A were used to determine the role of FVIII and TAFI in vascular remodeling after joint bleeding. Excessive vascular remodeling and vessel enlargement persisted in FVIII-deficient and TAFI-deficient mice, but not in transient hemophilia WT mice, after similar joint bleeding. TAFI-overexpression in FVIII-deficient mice prevented abnormal vessel enlargement and vascular leakage. Age-related vascular changes were observed with FVIII or TAFI deficiency and correlated positively with bleeding severity after injury, supporting increased vascularity as a major contributor to joint bleeding. Antibody-mediated inhibition of uPA also prevented abnormal vascular remodeling, suggesting that TAFI's protective effects include inhibition of uPA-mediated plasminogen activation. In conclusion, the functional TAFI deficiency in hemophilia drives maladaptive vascular remodeling in the joints after bleeding. These mechanistic insights allow targeted development of potentially new strategies to normalize vascularity and control rebleeding in HA.

Inherited Moderate Factor X Deficiency Presenting as Cardiac Tamponade

Factor X deficiency is a rare bleeding disorder that varies in the severity of its clinical manifestations. The symptoms of this disorder can occur at any age, although most severe cases appear in childhood. The rarity of this condition has not allowed for the establishment of evidence‐based management guidelines, and thus, individuals afflicted with factor X deficiency are treated based on limited literature and the opinions of clinicians with extensive experience. In this case report, we discuss a unique presentation of a 38-year-old male who was found to have cardiac tamponade as a result of his newly diagnosed inherited moderate factor X deficiency. This was discovered by obtaining a factor X activity assay and confirmed with genetic testing which demonstrated a missense variant on the factor X gene on chromosome 13. His management involved correction of his factor X deficiency with fresh frozen plasma, a pericardiocentesis, and placement of a pericardial window. He has been asymptomatic and without hemorrhagic episodes for the 10 months following his discharge.

Correction of bleeding in experimental severe hemophilia A by systemic delivery of factor VIII-encoding mRNA

The treatment or prevention of bleeding in patients with hemophilia A relies on replacement therapy with different factor VIII (FVIII)-containing products or on the use of by-passing agents, i.e., activated prothrombin complex concentrates or recombinant activated factor VII. Emerging approaches include the use of bispecific anti-factor IXa/factor X antibodies, anti-tissue factor pathway inhibitor antibodies, interfering RNA to antithrombin, and activated protein C-specific serpins or gene therapy. The latter strategies are, however, hampered by the short clinical experience and potential adverse effects including the absence of tight temporal and spatial control of coagulation and the risk of uncontrolled insertional mutagenesis. Systemic delivery of mRNA allows endogenous production of the corresponding encoded protein. Thus, injection of erythropoietin-encoding mRNA in a lipid nanoparticle formulation resulted in increased erythropoiesis in mice and macaques. Here, we demonstrate that a single injection of in vitro transcribed B domain-deleted FVIII-encoding mRNA to FVIII-deficient mice enables endogenous production of pro-coagulant FVIII. Circulating FVIII:C levels above 5% of normal levels were maintained for up to 72 h, with an estimated half-life of FVIII production of 17.9 h, and corrected the bleeding phenotype in a tail clipping assay. The endogenously produced FVIII did however exhibit low specific activity and induced a potent neutralizing IgG response upon repeated administration of the mRNA. Our results suggest that the administration of mRNA is a plausible strategy for the endogenous production of proteins characterized by poor translational efficacy. The use of alternative mRNA delivery systems and improved FVIII-encoding mRNA should foster the production of functional molecules and reduce their immunogenicity.

Fixed doses of N8-GP prophylaxis maintain moderate-to-mild factor VIII levels in the majority of patients with severe hemophilia A

BACKGROUND

N8-GP is an extended half-life recombinant factor VIII developed for prophylaxis and treatment of bleeds in patients with hemophilia A.

OBJECTIVE

To assess pharmacokinetic (PK) characteristics of N8-GP in previously treated patients with severe hemophilia A, model the time spent at hemophilia thresholds of ≥1 and ≤5 IU/dL (moderate) or >5 IU/dL (mild) FVIII levels during N8-GP prophylaxis, and investigate the relationship between N8-GP half-life and von Willebrand factor (vWF).

METHODS

PK assessments were obtained from patients with severe hemophilia A (FVIII < 1 IU/dL) participating in 4 clinical trials: pathfinder 1 (20-60 years); pathfinder 2 (12-17 and ≥18 years); pathfinder 5 (0-11 years), and pathfinder 7 (25-71 years). All PK profiles were assessed after washout and considered single-dose PK profiles. Pre- and postdose FVIII activity at steady state was measured at all visits.

RESULTS

From 69 patients, 108 PK profiles of N8-GP 50 IU/kg were assessed. Adults/adolescents received 50 IU/kg every 4 days, achieving mean trough levels of 3.0 IU/dL (95% confidence interval, 2.6-3.5, adults) and 2.7 IU/dL (1.8-4.0, adolescents). Children received 60 IU/kg twice weekly, leading to mean trough levels of 1.2 IU/dL (0.8-1.6, 0- to 5-year-olds) and 2.0 IU/dL (1.5-2.7, 6- to 11-year-olds). PK modeling predicted children dosed every 3 days and adults/adolescents dosed every 3 to 4 days would maintain FVIII levels >5 and >1 IU/dL for >80% and 100% of the time, respectively. N8-GP half-life correlated linearly with von Willebrand factor levels in adults/adolescents, less in children.

CONCLUSIONS

Prophylaxis with fixed intervals (Q4D/twice weekly) and fixed weight-based dosing (50/60 IU/kg) ensured >1 IU/dL FVIII trough levels in both adults and children.

Hindfoot malalignment in adults with haemophilic ankle arthropathy: The importance of early detection and orthotic treatment

INTRODUCTION

Haemophilic arthropathy (osteoarthritis secondary to haemophilia) of the ankle may result in painful hindfoot malalignment.

PURPOSE

To analyse hindfoot alignment in subjects with haemophilic arthropathy of the ankle and evaluate the response (improvement of pain, function and alignment) to the orthotic treatment prescribed in patients with malalignment.

METHODS

The study included 163 patients with haemophilia, all of them over 16 years of age. Hindfoot alignment and footprint were analysed in patients with and without haemophilic arthropathy of the ankle (as determined by the Pettersson score). Response to the use of an orthosis was evaluated at 6 months by means of the AOFAS Ankle-Hindfoot Scale.

RESULTS

Fifty-six (59.5%) patients with haemophilic arthropathy presented with concomitant  hindfoot malalignment. The most common abnormality was a valgus alignment combined with a neutral footprint. In 14 cases, valgus was associated with a pes planus or a pes cavus. Only 5 patients without haemophilic arthropathy (7.2%) presented with some form of malalignment. The differences between the groups were statistically significant. The probability of having malalignment increased with the degree of arthropathy. Patients with haemophilic arthropathy and malalignment were treated with an orthosis, with insoles as the most commonly used alternative (86%). Such treatment significantly improved patients' pain and function-related scores on the AOFAS Ankle-Hindfoot Scale.

CONCLUSION

Given the high rates of valgus malalignment in subjects with haemophilic arthropathy of the ankle, and the good response rates obtained following individualised orthotic treatment, it seems reasonable to routinely evaluate hindfoot alignment in this group of patients.

Dose tailoring of human cell line-derived recombinant factor VIII simoctocog alfa: Using a limited sampling strategy in patients with severe haemophilia A

AIMS

The use of factor VIII (FVIII) prophylaxis in haemophilia A is considered the standard of care, particularly in children. Despite adjustment of doses for body weight and/or age, a large pharmacokinetic (PK) variability between patients has been observed. PK-tailored prophylaxis may help clinicians adjust coagulation factor FVIII activity (FVIII:C) to the desired level, which may differ in individual patients. The objective was to develop a population PK model for simoctocog alfa based on pooled clinical trial data and to develop a Bayesian estimator to allow PK parameters in individual patients to be estimated using a reduced number of blood samples.

METHODS

PK data from 86 adults and 29 children/adolescents with severe haemophilia A were analysed. The FVIII data measured using 2 different assays (chromogenic and the 1-stage clotting assay) were fit to separate develop population PK models using nonlinear mixed-effect models. A Bayesian estimator was then developed to estimate the time above the threshold of 1%.

RESULTS

The PK data for chromogenic and the 1-stage clotting assays were both best described by a 2-compartment models. Simulations demonstrated good predictive capacity. The limited sampling strategy using blood sample at 3 and 24 hours allowed an accurate estimation of the time above the threshold of 1% FVIII:C (mean bias 0.01 and 0.11, mean precision 0.18 and 0.45 for 2 assay methods).

CONCLUSION

In this study, we demonstrated that a Bayesian approach can help to reduce the number of samples required to estimate the time above the threshold of 1% FVIII:C with good accuracy.

Hemophilia in a Changing Treatment Landscape

The mainstay of hemophilia management has been the regular, prophylactic infusion of missing coagulation factors VIII/IX. This approach is limited by the need for frequent intravenous infusions, high cost, limited availability, and the development of inhibitory antibodies to factors VIII/IX. Numerous recent breakthroughs are addressing many of these limitations. These include the development of extended half-life factors that require less frequent infusions and the development of various novel agents that can be given subcutaneously and infrequently, including FVIII-mimetic antibody and downregulators of natural anticoagulants. Finally, gene therapy is set to offer patients a possibility for a cure.

Bleed volume of experimental knee haemarthrosis correlates with the subsequent degree of haemophilic arthropathy

BACKGROUND

Haemophilic arthropathy is the main morbidity of haemophilia. The individual pathological response to the same number of clinically evident joint bleeds is highly variable; thus, it remains unknown if certain joint bleeding characteristics are critical for the development of arthropathy.

AIM

To study the relation between bleed volume and subsequent development of arthropathy, we aimed to develop quantitative in vivo imaging of active joint bleeds in a mouse model of haemophilia.

METHODS

Haemophilia A (F8-KO) and wild-type (WT) mice were IV-dosed with a micro-CT blood pool contrast agent prior to an induced knee haemarthrosis or sham procedure. The mice were micro-CT scanned five times the following 2 days to characterise and quantify the induced haemarthrosis in vivo. On Day 14, the mice were euthanized and pathological changes evaluated by histology and micro-CT. Additionally, bleeding characteristics in vehicle-treated F8-KO mice were compared with those of recombinant FVIII (rFVIII)-treated F8-KO mice.

RESULTS

F8-KO mice had a significantly larger bleed volume than WT mice at all scan time points. The bleed volume 12 hours after induction of haemarthrosis correlated with the subsequent degree of arthropathy. Presence of µCT-detectable bone pathology was associated with a significantly increased bleed volume among F8-KO mice. rFVIII treatment significantly reduced bleed volume in F8-KO mice.

CONCLUSION

Quantitative in vivo contrast-enhanced micro-CT imaging can be used to characterize and quantify joint bleeds in a mouse model of haemophilic arthropathy. The bleed volume correlates with the subsequent degree of arthropathy.

New therapies for hemophilia

Hemophilia A (HA) and hemophilia B (HB) are the most common severe bleeding disorders. Replacement therapy, providing the missing coagulation factor, has been the mainstay of treatment both prophylactically and to treat bleeding. Despite widespread availability of safe and effective replacement therapy, patients with HA and HB continue to experience a tremendous burden of treatment, breakthrough bleeding, and progressive joint disease, as well as high rates of inhibitor development. These remaining challenges are now being addressed by incredible advances in bioengineering. Recombinant bioengineering has led to replacement therapies with easier modes of administration, decreased immunogenicity, increased efficacy, and extended half-lives. Emicizumab, a bispecific antibody that acts as a substitutive therapy for HA, has been approved for patients with and without inhibitors. Novel compounds are in development to exploit the natural balance of hemostasis by targeting the natural anticoagulants protein C, protein S, tissue factor pathway inhibitor, and antithrombin. The substitution and rebalancing therapies provide an opportunity for steady-state hemostatic control without exposure to immunogenic clotting factor proteins. As such, they may have broader applications outside those being investigated in the clinical trial programs.

Emicizumab (ACE910): Clinical background and laboratory assessment of hemophilia A

Congenital hemophilia A, a relatively common and sometimes life-threatening bleeding disorder, is caused by inherited deficiency of clotting factor (F) VIII. The adoption of an appropriate medical and environmental prophylaxis is critical for long-term management of hemophilia because it will considerably reduce the number of both mild and severe bleeding episodes. Among the many therapeutic options that have become available over the past decades, ACE910 (also known as emicizumab) is a bispecific immunoglobulin G antibody characterized by its unique ability to bind FIX or FIXa on one arm and FX on the other, thus abrogating FVIII activity in vivo. Several phase I to III clinical trials have now been published, confirming the clinical efficacy and relative safety of this new agent for long-term prophylaxis of hemophilia A, especially those patients having FVIII inhibitors. The recent regulatory clearance of ACE910 in many countries will hence impose additional challenges to clinical laboratories because the panel of available tests will need to address the emerging issue of monitoring patients treated with this novel anti-hemophilic agent by using conventional as well as innovative approaches. Therefore, this article is aimed to provide an update on clinical background and challenges of laboratory assessment in hemophilia A patients undergoing ACE910 administration.

Emicizumab: Review of the literature and critical appraisal

INTRODUCTION

Emicizumab-kywh (ACE910) is a recombinant, humanized, asymmetric bispecific antibody that functions to bring activated FIX (FIXa) and zymogen FX into an appropriate steric conformation to medicate the activation of FX to FXa thereby mimicking the cofactor function of FVIIIa.

AIM

The objective of this manuscript was to review the development and potential role for emicizumab in the treatment of patients with haemophilia A with and without inhibitors.

METHODS

A Cochrane Library and PubMed (MEDLINE) search focusing on emicizumab in haemophilia was conducted.

RESULTS

In total, 37 citations were retrieved and serve as the database for the literature reviewed herein. Once-weekly subcutaneous injection of emicizumab at three dose levels has been shown to be effective as prophylaxis to prevent bleeding in a majority haemophilia A patients with inhibitors to FVIII. Likewise, prevention of bleeding was also observed in more than two thirds of patients without inhibitors to FVIII. One antidrug antibody to emicizumab has been reported in over 600 treated patients, two have developed thromboembolic events and three thrombotic microangiopathy. These thrombotic complications have occurred in conjunction with FVIII-bypassing agents, and none have been observed following recommendations from the manufacturer regarding concomitant use of bypassing agents. The median annual treated bleeding rates were decreased in patients with as well as those without an inhibitor to FVIII.

CONCLUSION

The principal advantage of emicizumab is subcutaneous administration and effectiveness irrespective of the presence of inhibitors. Emicizumab could conceivably represent a new epoch in the treatment of people with haemophilia A.

Joint Mobility and Physical Function of Danish Hemophilia Patients: A Three-Wave Panel Study Spanning 24 Years

BACKGROUND

The positive effects of factor treatment of hemophilia are well established, but the long-term outcomes are not well documented. This panel study evaluated changes in bleeding frequency, joint mobility, physical function, and symptoms in Danish patients with moderate to severe hemophilia A or B over 24 years.

METHODS

Three anonymous surveys were conducted in 1988, 2001, and 2012 targeting Danish patients with moderate to severe hemophilia, and the study participants, respectively, were 128, 156, and 164 male patients with hemophilia (PWH). The number of bleeding episodes, the use of factor concentrate, comorbidities, joint mobility, physical function, and symptoms were evaluated by means of self-reporting. Trends over time were analyzed using ordinal and multinomial logistic-regression models controlling for age group.

RESULTS

The proportion of PWH in the oldest age group (55-88 years) increased from 4% in 1988 to 18% in 2012. In 1988, a high risk of bleeding episodes was primarily found in the age group of 16-34 years. In 2012, a high risk was primarily found in the age group of 35-54 years. Joint mobility and physical function increased significantly from 1988 to 2012 but showed a noticeable decrement in the older age groups, even in 2012. Pain in the extremities, anxiety, and depression decreased significantly, but back pain increased. No significant changes were found for 7 other symptoms.

CONCLUSIONS

Significant improvements in joint mobility and physical function have occurred over the last 24 years, but PWH > 35 years still experience a decline in these areas with age. This decline underscores the importance of life-long treatment and continuous rehabilitation of PWH.

Bioengineered molecules for the management of haemophilia: Promise and remaining challenges

Recombinant DNA technology has led to accelerating introduction of novel therapeutics for the treatment of haemophilia. This technology has driven the development of recombinant clotting factors, extended half-life clotting factors, alternative biologics to promote haemostasis and enabled the launch of the gene therapy era for haemophilia. At the core of this technology is the ability to study the structure and function of the native molecules and to apply rational bioengineering to overcome limitations to the existing therapies. Through the study of haemophilia-causing mutations, site-directed mutagenesis, detailed structural models and a wide repertoire of animal models, new bioengineering strategies are helping overcome some of the remaining limitations and challenges of traditional clotting factor concentrates. Some of these bioengineering strategies are now being partnered with improvements in vectorology leading to the first wave of successful gene therapy approaches. This study will review past and present bioengineered molecules that are advancing care for haemophilia as well as novel approaches that promise to continue to improve care and outcomes for patients with haemophilia.

[Efficacy of short-term full-dose prophylaxis in adult Chinese patients with severe hemophilia A]

OBJECTIVE

To investigate the efficacy of short-term full-dose prophylaxis in adult Chinese patients with severe hemophilia A.

METHODS

Thirteen adult Chinese patients with severe hemophilia A receiving on-demand or low-dose prophylaxis underwent ultrasound examination of the target joints and evaluation of Hemophilia Joint Health Score (HJHS). The data of annual bleeding episodes in the period of on-demand or low-dose prophylaxis were collected retrospectively from the patients, and the changes in bleeding and joint condition (ultrasound findings of the target joints and HJHS) were observed during short-term full-dose prophylaxis. The activity intensity of the patients was assessed using the IPAQ questionnaire, and the 72 h FⅧ trough activity was measured during full-dose prophylaxis.

RESULTS

The median age of the 13 patients was 26.0 (20.5-29.0) years. For full-dose prophylaxis, the patients received a median therapeutic dose of 31.0 (29.1-33.0) IU/kg, administered for 3 times per week; the median 72 h FⅧ trough activity of patients was 1.7% (1.3-3.4%). During the follow-up period for 3 months, the annual bleeding rates (ABR) and annual joint bleeding rates (AJBR) decreased significantly in all the patients (P=0.001 and 0.001, respectively), but zero bleeding was achieved in only 4 patients (30.8%) and zero joint bleeding in 7 patients (53.8%); 9 patients (69.2%) still experienced breakthrough bleeding. The damage severity of target joints assessed by ultrasound and HJHS in 6 patients (46.2%)was worse than before and no obvious progression of target joints damage was found in 7 patients (53.8%). Compared with the patients without progression, the patients with worsened joint damage had poorer baseline joint condition, higher bleeding frequencies before and during the follow-up, a higher intensity of physical activity, and a lower baseline FⅧ activity.

CONCLUSIONS

At present, although short-term full-dose prophylaxis can significantly reduce the bleeding and partially prevent the progression of joint damage, it is not yet possible to achieve the goal of zero bleeding for all adult patients with severe hemophilia A in China, nor can it completely prevent further joint damage. For adult patients with different clinical bleeding phenotypes, joint conditions and physical activity intensity, individualized therapy involving additional evaluation methods should be implemented, and physiotherapy and surgical intervention can be considered when necessary.

GlycoPEGylated recombinant factor IX for hemophilia B in context

Decisions over hemophilia treatment selection and switching involve balancing many clinical and patient-related factors. The current standard of care for patients with hemophilia B is prophylaxis with plasma-derived or recombinant factor IX (rFIX) concentrates. However, several extended half-life (EHL) rFIX products have recently been developed to improve treatment convenience and clinical outcomes for these patients. Nonacog beta pegol, an rFIX product that combines the FIX protein with a 40 kDa polyethylene glycol moiety, has been evaluated in 115 previously treated patients with hemophilia B (including 25 children) in the paradigm clinical trial program. FIX activity levels and pharmacokinetics were monitored throughout these trials and showed that nonacog beta pegol offers significant pharmacological improvements over standard FIX products. Once-weekly prophylaxis with nonacog beta pegol 40 IU/kg resulted in fewer bleeds in all patients (median annualized bleeding rate of 1.0 across all ages), resolved 90% of target joints, and improved health-related quality of life. No patients developed FIX inhibitors, and there were no thromboembolic events or unexpected safety concerns. Nonacog beta pegol was also safe and effective in the perioperative setting. These findings show that nonacog beta pegol is highly effective, while also offering more convenient dosing than standard FIX products. Nonacog beta pegol represents a significant advance in the current context of treatment for hemophilia B, offering effective management across several treatment modalities and settings, and potentially easing the treatment burden for patients of all ages. Meanwhile, the development of novel treatment strategies, such as gene therapy, anti-tissue factor pathway inhibitor antibodies, and RNA interference therapy, may provide patients with additional therapeutic options, which would require reassessment of the role of EHL products in the future.

Practical aspects of extended half-life products for the treatment of haemophilia

Haemophilia A and haemophilia B are congenital X-linked bleeding disorders caused by deficiency of coagulation factor VIII (FVIII) and IX (FIX), respectively. The preferred treatment option for patients with haemophilia is replacement therapy. For patients with severe disease, prophylactic replacement of coagulation factor is the treatment of choice; this has been shown to reduce arthropathy significantly, reduce the frequency of bleeds and improve patients' quality of life. Prophylaxis with standard recombinant factor requires regular intravenous infusion at least two (FIX) to three (FVIII) times a week. Recombinant FVIII and FIX products with an extended half-life are in development, or have been recently licensed. With reported mean half-life extensions of 1.5-1.8 times that of standard products for FVIII and 3-5 times that of standard products for FIX, these products have the potential to address many of the unmet needs of patients currently treated with standard factor concentrates. For example, they may encourage patients to switch from on-demand treatment to prophylaxis and improve the quality of life of patients receiving prophylaxis. Indeed, extended half-life products have the potential to reduce the burden of frequent intravenous injections, reducing the need for central venous lines in children, promote adherence, improve outcomes, potentially allow for more active lifestyles and, depending on the dosing regimen, increase factor trough levels. Members of the Zürich Haemophilia Forum convened for their 19th meeting to discuss the practicalities of incorporating new treatments into the management of people with haemophilia. This review of extended half-life products considers their introduction in haemophilia treatment, including the appropriate dose and schedule of infusions, laboratory monitoring, patient selection, safety considerations, and the economic aspects of care.

The benefits of prophylaxis in patients with hemophilia B

INTRODUCTION

The health benefits of prophylactic dosing regimens for clotting factor therapy in patients with hemophilia include reduced joint damage and improved quality of life; as such, prophylaxis is recommended in treatment guidelines. However, many patients with hemophilia B are treated on demand, and prophylaxis has been utilized less frequently than in hemophilia A. Areas covered: This review discusses the opportunities and evidence for prophylaxis in hemophilia B, in the context of treatment guidelines and with regard to factor IX (FIX) replacement therapies, including long-acting recombinant FIX (rFIX). Expert commentary: Long-acting rFIX concentrates may increase uptake of and adherence to prophylaxis regimens through attainment of higher trough levels with longer dosing intervals. In this new era of hemophilia B treatment, physicians may be able to achieve better clinical outcomes for their patients and reconsider treatment goals. Maintaining higher FIX trough levels will undoubtedly have long-term benefits for patients, such as preserving joint function. The long-acting rFIX concentrates support robust prophylaxis regimens and offer physician's flexibility in treating patients to best suit their needs, whether to enable an active lifestyle, to achieve higher trough levels for better bleed protection, or simply to decrease the burden of treatment by reducing injection frequency.

Advances and innovations in haemophilia treatment

Haemophilia is a rare disease for which the approved therapeutic options have remained virtually unchanged for 50 years. In the past decade, however, there has been an explosion of innovation in the treatment options that are either in development or have been approved for haemophilia, including engineered clotting factors and an extensive pipeline of new approaches and modalities. Several of these new modalities, especially gene therapy, demonstrate proof of principle in haemophilia but could have broader applications. These advances, in combination with better diagnostics, are now enabling clinicians to improve the standard of care for people with haemophilia. The different mechanisms of action and modifications used in these therapies have implications for their safe and efficacious use, which must be balanced with their therapeutic utility. This Review focuses on the biological aspects of the most advanced and innovative approaches for haemophilia treatment and considers their future use.

Usefulness of chromogenic assays for potency assignment and recovery of plasma-derived FVIII and FIX concentrates or their recombinant long acting therapeutic equivalents with potential application in treated pediatric hemophiliac patients

On demand and prophylaxis usage of FVIII/ FIX concentrates for the therapeutic management of hemophilia has greatly changed quality of life, and healthy life span of affected patients. Availability of recombinant therapeutic FVIII and FIX products, and of their long-acting variants, further improves the treatment constraints, and progressively permits to hemophiliacs to have an almost normal way of life. Unlimited amounts of recombinant or engineered substitutive products become available, and open new avenues for extending the benefits of prophylaxis to all hemophiliac patients, not only in economically advanced territories, but also in emerging and developing countries, worldwide. Pharmacokinetics of injected products can be variable among treated patients, and dependent on age. In addition, patient medical status, existing diseases, and the nature of joint damages can impact protective effect of substitutive products, and risks associated to way of life and activity. Product requirements and half-life of infused products are therefore patient specific. Monitoring recoveries of injected products thus provide useful information for the most appropriate treatment adjustment. FVIII and FIX measurements in plasma of treated patients helps to establish the optimal interval between injections for each treated patient, and the overall therapeutic cost. Due to the high variability from reagent to reagent, and the different behavior from plasma derived products, clotting methods are not ideal for recombinant and long-acting products. They require to be performed only in association with a drug specific calibrator. They are not recommended for patients' survey, due to the high variety of reagents available. Chromogenic assays (2-stage methods) offer a standard reactivity to all available FVIII or FIX products in drugs, whether the way they are obtained, or in plasma. In a subset of treated patients, inhibitory antibodies to FVIII or FIX develop and can be measured with inhibition assays (Bethesda units), or by Elisa. Unfortunately, FVIII or FIX substitutive therapies cannot be used in patients with inhibitors, and alternative clinical management is requested, such as the use of FEIBA or FVIIa for their bypassing activity. A new treatment is being introduced in the form of a bispecific antibody (Emicizumab) targeted to both FIXa and FX, and which allows activating FX by FIXa without the need for FVIII. Some chromogenic assays (Biophen FVIII), designed with human proteins, offer the possibility to measure the activity and recovery of this new drug. Chromogenic methods are then useful for establishing potency of therapeutic products or monitoring recovery and kinetics in treated patients, through plasma measurements. Availability of International Standards for FVIII and FIX, in concentrates or plasma, allows harmonization of assay results.

Tailored frequency-escalated primary prophylaxis for severe haemophilia A: results of the 16-year Canadian Hemophilia Prophylaxis Study longitudinal cohort

BACKGROUND

Severe haemophilia A has high morbidity, and treatment, while effective, is very expensive. We report the 16-year follow-up of the Canadian Hemophilia Prophylaxis Study, which examined the effectiveness of tailored frequency-escalated primary prophylaxis with a focus on health outcomes within the domains of body structures and functions, and activities and participation (according to the WHO International Classification of Functioning, Disability and Health [WHO-ICF] framework) and a view to reducing consumption of costly clotting factor, which accounts for more than 90% of the cost of care of severe haemophilia.

METHODS

In this longitudinal study, boys with severe haemophilia A from 12 Canadian centres were enrolled at age 1·0-2·5 years. They were treated with standard half-life recombinant factor VIII (SHL-rFVIII), beginning as once-weekly prophylaxis with 50 IU/kg and escalating in frequency (with accompanying dose adjustments) in response to breakthrough bleeding as determined by the protocol. The primary endpoint for this analysis was joint health, as measured by the modified Colorado Child Physical Examination Scores (CCPES) at study end. All analyses were done by intention to treat. The trial is complete, and is registered with ClinicalTrials.gov, number NCT01085344.

FINDINGS

Between June 26, 1997, and Jan 30, 2007, 56 boys were enrolled. They were followed for a median of 10·2 years (to a maximum of 16·1 years). Median rFVIII usage was about 3600 IU/kg per year. The median end-of-study CCPES physical examination score was 1 (IQR 1-3; range 0-12) for the left ankle and 1 (1-2; 0-12) for the right ankle, with all other joints having a median score of 0. No treatment-related safety events occurred over the duration of the study, including central venous catheter infections. The median annualised index joint bleeding rate was 0·95 per year (IQR 0·44-1·35; range 0·00-13·43), but 17 (30%) patients had protocol-defined unacceptable breakthrough bleeding at some point during the study.

INTERPRETATION

Tailored frequency-escalated prophylaxis leads to very little arthropathy and very good health outcomes within the WHO-ICF domains, and only uses a moderate amount of expensive clotting factor as compared with standard prophylaxis protocols. Some sequelae of bleeding were observed in our cohort, and future studies should consider a more stringent protocol of escalation.

FUNDING

This study was initially funded by grants from the Medical Research Council of Canada/Pharmaceutical Manufacturers Association of Canada Partnership Fund and the Bayer/Canadian Blood Services/Hema-Quebec Partnership Fund. Subsequent renewals were funded by Bayer.

Practical Implications of Factor IX Gene Transfer for Individuals with Hemophilia B: A Clinical Perspective

Gene therapy for severe hemophilia is on the cusp of entering clinical practice. However, there is limited clinical experience in this area given that gene transfer is a relatively recent technology. Therefore, this clinical perspective article will review the evidence supporting gene therapy in this field, examine ways to open a dialogue about gene therapy with patients in the clinic setting, and present a case of a participant in a recent clinical trial of gene therapy for hemophilia. Clinical trials in hemophilia using adeno-associated virus (AAV) vectors to transfer functional factor IX (FIX) have reported increases in FIX activity to functional levels, reduced bleed frequency, and a lessening or abrogation of the need for costly FIX replacement. The safety profile of AAV-mediated gene therapy also appears positive, with manageable, asymptomatic increases in liver enzymes being the most commonly described adverse event. Examining a clinical case in hemophilia B more closely, gene transfer decreased annualized bleeds from six (unknown or spontaneous) bleeds before treatment to three (spontaneous) bleeds after treatment alongside a 55% reduction in FIX replacement. The participant experienced an increase in traumatic bleeds after treatment, which appears to reflect increased physical activity and early prophylaxis discontinuation. After the gene transfer, the participant considered his hemophilia to be "cured," which emphasizes the need to manage patient expectations, particularly regarding activity levels and bleed risk in the immediate post-treatment period. Gene therapy for hemophilia has the potential to transform the lives of affected individuals and is likely to create a new class of hemophilia patient who has shifted from a severe to a mild phenotype. Despite having a mild phenotype, these individuals may retain a legacy of increased bleed risk and joint damage from their years with severe hemophilia and will need different clinical management compared to a more typical individual with mild hemophilia.

Muscle function deterioration in patients with haemophilia: Prospective experience from Costa Rica

INTRODUCTION

In haemophilia, recurrent joint bleeds are responsible for the development of chronic joint damage, because blood induces biochemical changes in joint structures. Joint degeneration is a long process, and structural damage is often preceded by joint dysfunction, which is represented by quantitative and qualitative changes in the contraction pattern of muscles around the joints. Muscle function in patients with haemophilia is still poorly investigated.

AIM

The aim of this 2-year prospective study was to assess the changes in muscle function of lower limbs in a group of patients affected with haemophilia in San José, Costa Rica.

METHODS

Muscle function of lower limbs was assessed by means of surface electromyography (sEMG) accomplished at study enrolment and after 2 years of follow-up. Gluteus medius, vastus medialis, biceps femoris, gastrocnemius and tibialis anterior were examined. All patients underwent concurrent clinical examination using Haemophilia Joint Health Score (HJHS).

RESULTS

Sixty patients aged 2-43 years with severe haemophilia underwent clinical and sEMG evaluation. Thirty-two patients (53%) had target joints. sEMG parameters were altered in all patients and were not correlated to the presence of target joints and/or an abnormal HJHS. Muscle function deterioration was observed after 2 years of follow-up despite an unmodified HJHS.

CONCLUSIONS

Muscle function of lower limbs as detected by means of sEMG was impaired in patients with haemophilia irrespective of the presence of overt joint damage. sEMG is a simple and sensitive assessment tool able to detect muscle dysfunction and so favouring the implementation of early rehabilitation therapy.

Long-term tolerability, immunogenicity and efficacy of Nuwiq® (human-cl rhFVIII) in children with severe haemophilia A

INTRODUCTION

Nuwiq^® (human-cl rhFVIII, simoctocog alfa) is a 4th generation recombinant human FVIII, without chemical modification or fusion with any other protein, produced in a human cell line.

AIM/METHODS

This study (GENA-13) was an extension of the GENA-03 study in which previously treated children aged 2-12 years with severe haemophilia A received Nuwiq^® prophylaxis for ≥6 months. GENA-13 examined long-term tolerability, immunogenicity and efficacy of Nuwiq^® prophylaxis in children.

RESULTS

Of 59 patients enrolled in GENA-03, 49 continued Nuwiq^® prophylaxis in GENA-13 for a median (range) of 30.0 (9.5-52.0) months. No patient withdrew due to drug-related adverse events or developed inhibitors. Only 2 of 20 518 infusions were associated with possibly related adverse events (dyspnoea, fever). The estimated annualized bleeding rate (ABR) was 0.67 (95% CI: 0.44, 1.02) for spontaneous and 2.88 (95% CI: 1.86, 4.46) for all bleeds. Younger children (2-5 years) had lower ABRs than children aged 6-12 years. Annualized bleeding rates were reduced in GENA-13 vs GENA-03, especially for spontaneous bleeds in younger children (71% reduction; ABR ratio 0.29 [95% CI: 0.11, 0.74]). Nuwiq^® efficacy was rated as excellent/good in the treatment of 83.0% of 305 evaluated breakthrough bleeds. Surgical prophylaxis with Nuwiq^® was rated as excellent for all 17 assessed procedures.

CONCLUSION

Long-term treatment with Nuwiq^® for the prevention of bleeds in children with severe haemophilia A was well tolerated, effective and reduced spontaneous bleeding by up to 70% compared with GENA-03.

Optimization of prophylaxis for hemophilia A

Background & aims

Prophylactic injections of factor VIII reduce the incidence of bleeds and slow the development of joint damage in people with hemophilia. The aim of this study was to identify optimal person-specific prophylaxis regimens for children with hemophilia A.

Methods

Analytic and numerical methods were used to identify prophylaxis regimens which maximize the time for which plasma factor VIII concentrations exceed a threshold, maximize the lowest plasma factor VIII concentrations, and minimize risk of bleeds.

Results

It was demonstrated analytically that, for any injection schedule, the regimen that maximizes the lowest factor VIII concentration involves sharing doses between injections so that all of the trough concentrations in a prophylaxis cycle are equal. Numerical methods were used to identify optimal prophylaxis schedules and explore the trade-offs between efficacy and acceptability of different prophylaxis regimens. The prophylaxis regimen which minimizes risk of bleeds depends on the person’s pattern of physical activity and may differ greatly from prophylaxis regimens that optimize pharmacokinetic parameters. Prophylaxis regimens which minimize risk of bleeds also differ from prophylaxis regimens that are typically prescribed. Predictions about which regimen is optimal are sensitive to estimates of the effects on risk of bleeds of factor VIII concentration and physical activity.

Conclusion

The methods described here can be used to identify optimal, person-specific prophylaxis regimens for children with hemophilia A.

Gene therapy for hemophilia

Individuals with the inherited bleeding disorder hemophilia have achieved tremendous advances in clinical outcomes through widespread implementation of prophylactic replacement with safe and efficacious factor VIII and IX. However, despite this therapeutic approach, bleeds still occur, some with serious consequence, joint disease has not been eradicated, and patients have not yet been liberated from the need for regular intravenous infusions. The shift from protein replacement to gene replacement is offering great hope to achieve durable levels of plasma factor activity levels high enough to remove the risk for recurrent joint bleeding. For the first time, clinical trial results are showing promise for "curative" correction of the bleeding phenotype.

A contemporary look at FVIII inhibitor development: still a great influence on the evolution of hemophilia therapies

INTRODUCTION

The development of inhibitors against factor VIII (FVIII) replacement therapy remains the most important challenge for clinicians in the treatment of hemophilia patients. This review focusses on risk factors and management of FVIII inhibitors, particularly in light of SIPPET study findings and subsequent analyses. Areas covered: A brief history and evolution of hemophilia therapies is provided, including an overview of conventional and new (including investigational) therapeutic approaches for the treatment of hemophilia. The SIPPET study, the first randomized clinical trial to demonstrate a lower incidence of inhibitors in previously untreated patients treated with plasma-derived FVIII products compared with recombinant FVIII products, has generated much debate. We review the SIPPET trial and reactions, in addition to preliminary observations from a single center's experience, the cost impact of inhibitors, recent findings from SIPPET subanalyses, and inhibitor development in previously-treated patients. Expert commentary: Despite recent advances in potential new treatment options for hemophilia, conventional factor replacement concentrates currently remain the cornerstone of treatment. It is paramount that clinicians familiarize themselves with the findings from the SIPPET trial and substudies, in order to better inform their patients and families on inhibitor risk factors and to aid the treatment decision-making process.

Low incidence of factor VIII inhibitors in previously untreated patients with severe haemophilia A treated with octanate® : Final report from a prospective study

INTRODUCTION

Octanate^® is a human, plasma-derived, von Willebrand factor-stabilized coagulation factor VIII (FVIII) concentrate with demonstrated haemostatic efficacy in previously treated patients with haemophilia A.

AIM

This prospective, open-label study aimed to assess the immunogenicity of octanate^® in previously untreated patients (PUPs).

METHODS

The study monitored development of FVIII inhibitors in 51 PUPs. Tolerability, viral safety, FVIII recovery and efficacy of octanate^® for the prevention and treatment of bleeds and in surgical procedures were also assessed.

RESULTS

Five (9.8%) of the 51 patients developed inhibitors during the study, 4 of which (7.8%) were high titre. Three inhibitor cases (5.9%) were considered clinically relevant; 2 were transient inhibitors that disappeared during regular octanate^® treatment without a change in dose or treatment frequency. Amongst 45 patients with FVIII:C <1% at baseline and who received ≥20 exposure days (EDs) or had <20 EDs but developed an inhibitor, inhibitor incidence was 11.1% (6.7% clinically relevant). All clinically relevant inhibitors developed within 20 EDs of on-demand treatment. No inhibitors developed in PUPs receiving prophylaxis. All patients who developed inhibitors had either intron 22 inversions or large deletions. Irrespective of the reason for administration, haemostatic efficacy was rated as "excellent" in 99.6% of all infusions (4700 of 4717 infusions), and no complications were reported in 23 surgical procedures. Mean incremental in vivo recovery was 2.0%/IU/kg (±0.7) and 1.9%/IU/kg (±0.5) for the first and second assessments, respectively. Tolerability was rated "very good" in 99.9% of infusions.

CONCLUSION

In PUPs with severe haemophilia A, octanate^® demonstrated haemostatic efficacy with a low rate of inhibitor development.

Validation of the Brazilian version of the VERITAS-Pro scale to assess adherence to prophylactic regimens in hemophilia

INTRODUCTION

Prophylaxis is the treatment of choice for patients with severe hemophilia. Low adherence may limit the effectiveness of the prophylactic regimen, thereby compromising outcomes.

OBJECTIVE

The objective of this study was to validate the Brazilian version of the VERITAS-Pro prophylaxis adherence scale, originally an American questionnaire that can be answered by the individual responsible for prophylaxis as well as by an observer.

METHODS

The scale has 24 questions divided into six subscales: Routine, Dosage, Plan, Remember, Skip and Communicate. Participants were recruited at a blood center in southeastern Brazil for validation and reliability analyses. Validation measures included the results obtained using analog visual scales of adherence, interval between medication dispensed by the treatment center pharmacy and the percentage of recommended doses administered and infusions registered in the patients' logs.

RESULTS

The study included 32 individuals responsible for prophylaxis and five observers. The internal consistency was very good for the VERITAS-Pro total score, excellent for the Remember, Skip and Communicate subscales, good for the Dosage subscale, and acceptable for the Routine and Plan subscales. Twelve participants answered the questionnaire on more than one occasion to evaluate reproducibility. The intraclass correlation coefficient was excellent. Regarding convergent validity, the VERITAS-Pro scores were moderately correlated with the global adherence scale and with infusion log records, but showed a weak correlation with pharmacy dispensation records.

CONCLUSION

The Brazilian version of VERITAS-Pro is a valid and reliable instrument, enabling the understanding of specific factors related to non-adherence and allowing targeted interventions for proper treatment.

A new modeling approach allowing prediction and comparison of the long-term outcomes of treatments for hemophilia B

Aim: To develop a modeling approach to compare clinical outcomes of nonacog beta pegol to a standard-acting factor IX (FIX) product. Methods: Regression analysis linked FIX activity to bleed rates. Pharmacokinetic parameters were used to estimate FIX activity over time. The probability of bleeds was estimated for both treatment arms. A Markov model estimated the presence of target joints and annualized bleed rates (ABRs). Results: Higher FIX activity showed reduced ABRs (p < 0.001). Target joints resulted in higher bleed rates (p < 0.001). When FIX activity levels and bleed risks were applied to the Markov model, ABRs for nonacog beta pegol and its comparator were 2.40 and 6.36, respectively. Conclusion: This model provides a starting point for assessing the added value of new FIX products.