New therapies using nonfactor products for patients with hemophilia and inhibitors

Fitusiran prophylaxis in people with hemophilia A or B who switched from prior BPA/CFC prophylaxis: the ATLAS-PPX trial

ABSTRACT

Fitusiran, a subcutaneous investigational small interfering RNA therapeutic, targets antithrombin to rebalance hemostasis in people with hemophilia A or B (PwHA/B), irrespective of inhibitor status. This phase 3, open-label study evaluated the efficacy and safety of fitusiran prophylaxis in males aged ≥12 years with hemophilia A or B, with or without inhibitors, who received prior bypassing agent (BPA)/clotting factor concentrate (CFC) prophylaxis. Participants continued their prior BPA/CFC prophylaxis for 6 months before switching to once-monthly 80 mg fitusiran prophylaxis for 7 months (onset and efficacy periods). Primary end point was annualized bleeding rate (ABR) in the BPA/CFC prophylaxis and fitusiran efficacy period. Secondary end points included spontaneous ABR (AsBR) and joint ABR (AjBR). Safety and tolerability were assessed. Of 80 enrolled participants, 65 (inhibitor, n = 19; noninhibitor, n = 46) were eligible for ABR analyses. Observed median ABRs were 6.5 (interquartile range [IQR], 2.2-19.6)/4.4 (IQR, 2.2-8.7) with BPA/CFC prophylaxis vs 0.0 (IQR, 0.0-0.0)/0.0 (IQR, 0.0-2.7) in the corresponding fitusiran efficacy period. Estimated mean ABRs were substantially reduced with fitusiran by 79.7% (P = .0021) and 46.4% (P = .0598) vs BPA/CFC prophylaxis, respectively. Forty-one participants (63.1%) experienced 0 treated bleeds with fitusiran vs 11 (16.9%) with BPAs/CFCs. Median AsBR and AjBR were both 2.2 with BPA/CFC prophylaxis and 0.0 in the fitusiran efficacy period. Two participants (3.0%) experienced suspected or confirmed thromboembolic events with fitusiran. Once-monthly fitusiran prophylaxis significantly reduced bleeding events vs BPA/CFC prophylaxis in PwHA/B, with or without inhibitors, and reported adverse events were generally consistent with previously identified risks of fitusiran. This trial was registered at www.ClinicalTrials.gov as #NCT03549871.

Non-clotting factor therapies for preventing bleeds in people with congenital hemophilia A or B

BACKGROUND

Management of congenital hemophilia A and B is by prophylactic or on-demand replacement therapy with clotting factor concentrates. The effects of newer non-clotting factor therapies such as emicizumab, concizumab, marstacimab, and fitusiran compared with existing standards of care are yet to be systematically reviewed.

OBJECTIVES

To assess the effects (clinical, economic, patient-reported, and adverse outcomes) of non-clotting factor therapies for preventing bleeding and bleeding-related complications in people with congenital hemophilia A or B compared with prophylaxis with clotting factor therapies, bypassing agents, placebo, or no prophylaxis.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group's Coagulopathies Trials Register, electronic databases, conference proceedings, and reference lists of relevant articles and reviews. The date of the last search was 16 August 2023.

SELECTION CRITERIA

Randomized controlled trials (RCTs) evaluating people with congenital hemophilia A or B with and without inhibitors, who were treated with non-clotting factor therapies to prevent bleeds.

DATA COLLECTION AND ANALYSIS

Two review authors independently reviewed studies for eligibility, assessed risk of bias, and extracted data for the primary outcomes (bleeding rates, health-related quality of life (HRQoL), adverse events) and secondary outcomes (joint health, pain scores, and economic outcomes). We assessed the mean difference (MD), risk ratio (RR), 95% confidence interval (CI) of effect estimates, and evaluated the certainty of the evidence using GRADE.

MAIN RESULTS

Six RCTs (including 397 males aged 12 to 75 years) were eligible for inclusion. Prophylaxis versus on-demand therapy in people with inhibitors Four trials (189 participants) compared emicizumab, fitusiran, and concizumab with on-demand therapy in people with inhibitors. Prophylaxis using emicizumab likely reduced annualized bleeding rates (ABR) for all bleeds (MD -22.80, 95% CI -37.39 to -8.21), treated bleeds (MD -20.40, 95% CI -35.19 to -5.61), and annualized spontaneous bleeds (MD -15.50, 95% CI -24.06 to -6.94), but did not significantly reduce annualized joint and target joint bleeding rates (AjBR and AtjBR) (1 trial; 53 participants; moderate-certainty evidence). Fitusiran also likely reduced ABR for all bleeds (MD -28.80, 95% CI -40.07 to -17.53), treated bleeds (MD -16.80, 95% CI -25.80 to -7.80), joint bleeds (MD -12.50, 95% CI -19.91 to -5.09), and spontaneous bleeds (MD -14.80, 95% CI -24.90 to -4.71; 1 trial; 57 participants; moderate-certainty evidence). No evidence was available on the effect of bleed prophylaxis using fitusiran versus on-demand therapy on AtjBR. Concizumab may reduce ABR for all bleeds (MD -12.31, 95% CI -19.17 to -5.45), treated bleeds (MD -10.10, 95% CI -17.74 to -2.46), joint bleeds (MD -9.55, 95% CI -13.55 to -5.55), and spontaneous bleeds (MD -11.96, 95% CI -19.89 to -4.03; 2 trials; 78 participants; very low-certainty evidence), but not target joint bleeds (MD -1.00, 95% CI -3.26 to 1.26). Emicizumab prophylaxis resulted in an 11.31-fold increase, fitusiran in a 12.5-fold increase, and concizumab in a 1.59-fold increase in the proportion of participants with no bleeds. HRQoL measured using the Haemophilia Quality of Life Questionnaire for Adults (Haem-A-QoL) physical and total health scores was improved with emicizumab, fitusiran, and concizumab prophylaxis (low-certainty evidence). Non-serious adverse events were higher with non-clotting factor therapies versus on-demand therapy, with injection site reactions being the most frequently reported adverse events. Transient antidrug antibodies were reported for fitusiran and concizumab. Prophylaxis versus on-demand therapy in people without inhibitors Two trials (208 participants) compared emicizumab and fitusiran with on-demand therapy in people without inhibitors. One trial assessed two doses of emicizumab (1.5 mg/kg weekly and 3.0 mg/kg bi-weekly). Fitusiran 80 mg monthly, emicizumab 1.5 mg/kg/week, and emicizumab 3.0 mg/kg bi-weekly all likely resulted in a large reduction in ABR for all bleeds, all treated bleeds, and joint bleeds. AtjBR was not reduced with either of the emicizumab dosing regimens. The effect of fitusiran prophylaxis on target joint bleeds was not assessed. Spontaneous bleeds were likely reduced with fitusiran (MD -20.21, 95% CI -32.12 to -8.30) and emicizumab 3.0 mg/kg bi-weekly (MD -15.30, 95% CI -30.46 to -0.14), but not with emicizumab 1.5 mg/kg/week (MD -14.60, 95% CI -29.78 to 0.58). The percentage of participants with zero bleeds was higher following emicizumab 1.5 mg/kg/week (50% versus 0%), emicizumab 3.0 mg/kg bi-weekly (40% versus 0%), and fitusiran prophylaxis (40% versus 5%) compared with on-demand therapy. Emicizumab 1.5 mg/kg/week did not improve Haem-A-QoL physical and total health scores, EQ-5D-5L VAS, or utility index scores (low-certainty evidence) when compared with on-demand therapy at 25 weeks. Emicizumab 3.0 mg/kg bi-weekly may improve HRQoL measured by the Haem-A-QoL physical health score (MD -15.97, 95% CI -29.14 to -2.80) and EQ-5D-5L VAS (MD 9.15, 95% CI 2.05 to 16.25; 1 trial; 43 participants; low-certainty evidence). Fitusiran may result in improved HRQoL shown as a reduction in Haem-A-QoL total score (MD -7.06, 95% CI -11.50 to -2.62) and physical health score (MD -19.75, 95% CI -25.76 to -11.94; 1 trial; 103 participants; low-certainty evidence). The risk of serious adverse events in participants without inhibitors also likely did not differ following prophylaxis with either emicizumab or fitusiran versus on-demand therapy (moderate-certainty evidence). Transient antidrug antibodies were reported in 4% (3/80) participants to fitusiran, with no observed effect on antithrombin lowering. A comparison of the different dosing regimens of emicizumab identified no differences in bleeding, safety, or patient-reported outcomes. No case of treatment-related cancer or mortality was reported in any study group. None of the included studies assessed our secondary outcomes of joint health, clinical joint function, and economic outcomes. None of the included studies evaluated marstacimab.

AUTHORS' CONCLUSIONS

Evidence from RCTs shows that prophylaxis using non-clotting factor therapies compared with on-demand treatment may reduce bleeding events, increase the percentage of individuals with zero bleeds, increase the incidence of non-serious adverse events, and improve HRQoL. Comparative assessments with other prophylaxis regimens, assessment of long-term joint outcomes, and assessment of economic outcomes will improve evidence-based decision-making for the use of these therapies in bleed prevention.

Icaritin Sensitizes Thrombin- and TxA2-Induced Platelet Activation and Promotes Hemostasis via Enhancing PLCγ2-PKC Signaling Pathways

BACKGROUND

 Vascular injury results in uncontrollable hemorrhage in hemorrhagic diseases and excessive antithrombotic therapy. Safe and efficient hemostatic agents which can be orally administered are urgently needed. Platelets play indispensable roles in hemostasis, but there is no drug exerting hemostatic effects through enhancing platelet function.

METHODS

 The regulatory effects of icaritin, a natural compound isolated from Herba Epimedii, on the dense granule release, thromboxane A2 (TxA2) synthesis, α-granule release, activation of integrin αIIbβ3, and aggregation of platelets induced by multiple agonists were investigated. The effects of icaritin on tail vein bleeding times of warfarin-treated mice were also evaluated. Furthermore, we investigated the underlying mechanisms by which icaritin exerted its pharmacological effects.

RESULTS

 Icaritin alone did not activate platelets, but significantly potentiated the dense granule release, α-granule release, activation of integrin αIIbβ3, and aggregation of platelets induced by thrombin and U46619. Icaritin also shortened tail vein bleeding times of mice treated with warfarin. In addition, phosphorylated proteome analysis, immunoblotting analysis, and pharmacological research revealed that icaritin sensitized the activation of phospholipase Cγ2 (PLCγ2)-protein kinase C (PKC) signaling pathways, which play important roles in platelet activation.

CONCLUSION

 Icaritin can sensitize platelet activation induced by thrombin and TxA2 through enhancing the activation of PLCγ2-PKC signaling pathways and promote hemostasis, and has potential to be developed into a novel orally deliverable therapeutic agent for hemorrhages.

Clot Waveform Analysis for Monitoring Hemostasis

Clot waveform analysis (CWA) is a recently developed global coagulation assessment, based on the continuous observation of changes in light transmittance, absorbance, or light scattering that occurs as fibrin formed in a plasma sample during routine clotting tests such as activated partial thromboplastin time (aPTT) and prothrombin time (PT). CWA can utilize qualitative waveform patterns as well as sensitive quantitative parameters and can be used as a simple method to assess global hemostasis, and can be applied to various challenging clinical situations. Although not all coagulation analyzers currently in use are able to provide CWA, the number of analyzers available to do so is increasing, as the usefulness of this process has become more widely recognized. CWA can be based on the coagulation mechanism of aPTT, an intrinsic trigger, and this has been reported in many studies, including diagnosis and treatment of patients with hemophilia, disseminated intravascular coagulation, and monitoring of anticoagulants and thrombosis. CWA using trace amounts of tissue factors also has the potential to expand the applications of this technology. Recently, there have been reports of the combined evaluation of fibrinolytic dynamics. Among the existing global coagulation assays, CWA may prove to be the easiest to standardize in clinical practice. However, more extensive testing using standardized methods in various clinical settings is needed to determine the true role of CWA in the evaluation of hemostasis and thrombosis in the future.

Phase 3 Trial of Concizumab in Hemophilia with Inhibitors

BACKGROUND

Concizumab is an anti-tissue factor pathway inhibitor monoclonal antibody designed to achieve hemostasis in all hemophilia types, with subcutaneous administration. A previous trial of concizumab (explorer4) established proof of concept in patients with hemophilia A or B with inhibitors.

METHODS

We conducted the explorer7 trial to assess the safety and efficacy of concizumab in patients with hemophilia A or B with inhibitors. Patients were randomly assigned in a 1:2 ratio to receive no prophylaxis for at least 24 weeks (group 1) or concizumab prophylaxis for at least 32 weeks (group 2) or were nonrandomly assigned to receive concizumab prophylaxis for at least 24 weeks (groups 3 and 4). After a treatment pause due to nonfatal thromboembolic events in three patients receiving concizumab, including one from the explorer7 trial, concizumab therapy was restarted with a loading dose of 1.0 mg per kilogram of body weight, followed by 0.2 mg per kilogram daily (potentially adjusted on the basis of concizumab plasma concentration as measured at week 4). The primary end-point analysis compared treated spontaneous and traumatic bleeding episodes in group 1 and group 2. Safety, patient-reported outcomes, and pharmacokinetics and pharmacodynamics were also assessed.

RESULTS

Of 133 enrolled patients, 19 were randomly assigned to group 1 and 33 to group 2; the remaining 81 were assigned to groups 3 and 4. The estimated mean annualized bleeding rate in group 1 was 11.8 episodes (95% confidence interval [CI], 7.0 to 19.9), as compared with 1.7 episodes (95% CI, 1.0 to 2.9) in group 2 (rate ratio, 0.14 [95% CI, 0.07 to 0.29]; P<0.001). The overall median annualized bleeding rate for patients receiving concizumab (groups 2, 3, and 4) was 0 episodes. No thromboembolic events were reported after concizumab therapy was restarted. The plasma concentrations of concizumab remained stable over time.

CONCLUSIONS

Among patients with hemophilia A or B with inhibitors, the annualized bleeding rate was lower with concizumab prophylaxis than with no prophylaxis. (Funded by Novo Nordisk; explorer7 ClinicalTrials.gov number, NCT04083781.).

Reclassifying hemophilia to include the definition of outcomes and phenotype as new targets

Hemophilia is classified into mild, moderate, and severe based on coagulation factor activity levels. Factor replacement and prophylaxis regimens in persons with hemophilia have helped to reduce bleeding and its related complications. With several newer treatments, some already approved and others soon to be, there may be a need to consider health-related quality of life in addition to bleed prevention as the goals of providing comprehensive care to persons with hemophilia. In this article, we discussed the reasons why such an approach may be relevant and call for the International Society of Thrombosis and Haemostasis to revisit the current classification of hemophilia.

The use of infrared thermography for non-invasive detection of bleeding and musculoskeletal abnormalities in patients with hemophilia: an observational study

BACKGROUND

In patients with hemophilia (PwH), bleeding often occurs in joints and muscles, and early detection of hemorrhage is important to prevent the onset and progression of mobility impairment. Complex-Image analysis such as ultrasonography, computed tomography, and magnetic resonance imaging are used to detect bleeding. On the other hand, no simple and rapid method to detect the active bleeding has been reported. Local inflammatory responses occur when blood leaks from damaged vessels, and the temperature at the site of active bleeding could be expected to increase in these circumstances, leading to an increase in surrounding skin temperature. Therefore, the purpose of this study was to investigate whether the measurement of skin temperature using infrared thermography (IRT) can be used as a diagnostic aid to detect active bleeding.

METHODS

Fifteen PwH (from 6 to 82 years old) complaining of discomfort such as pain were examined. Thermal images were obtained simultaneously at the affected sides and comparable unaffected sides. The average skin temperature of the affected side and of the unaffected side were measured. The temperature differences were calculated by subtracting the average skin temperature at the unaffected side from the affected side.

RESULTS

In eleven cases with active bleeding, the skin temperature at the affected side was more than 0.3 °C higher (0.3 °C to 1.4 °C) compared to the unaffected side. In two cases without active bleeding, there were no significant differences in skin temperature between the affected and unaffected sides. In two cases with previous rib or thumb bone fracture, the skin temperature at the affected side was 0.3 °C or 0.4 °C lower than that of the unaffected side, respectively. In two cases with active bleeding in which longitudinal evaluation was conducted, the difference in skin temperature decreased after hemostatic treatment.

CONCLUSION

The analysis of skin temperature deference using IRT was a useful supportive tool to readily assess musculoskeletal abnormalities and bleeding in PwH as well as to determine the success of the hemostatic treatment.

Antithrombin lowering in hemophilia: a closer look at fitusiran

Thrombin is a key enzyme in the maintenance of normal hemostatic function and is the central product of an interconnected set of simultaneously occurring cellular and proteolytic events. Antithrombin (AT) is a natural anticoagulant that downregulates different components of the clotting process, particularly thrombin generation. In good health, well-regulated hemostasis is the result of a balance between procoagulant and anticoagulant elements. Cumulative understanding of the regulation of thrombin generation and its central role in hemostasis and bleeding disorders has led to the clinical development of therapeutic strategies that aim to rebalance hemostasis in individuals with hemophilia and other coagulation factor deficiencies to improve bleeding phenotype. The aim of this review is to discuss the rationale for AT lowering in individuals with hemophilia, with a focus on fitusiran, its mechanism of action, and its potential as a prophylactic therapy for individuals with hemophilia A or B, with or without inhibitors. Fitusiran is an investigational small, interfering RNA therapeutic that targets and lowers AT. It is currently in phase III clinical trials and results have shown its potential to increase thrombin generation, leading to enhanced hemostasis and improved quality of life while reducing the overall treatment burden.

Hemophilia A: Emicizumab monitoring and impact on coagulation testing

Hemophilia A is an X-linked recessive bleeding disorder characterized by absent or ineffective coagulation factor VIII, a condition that could result in a severe and potentially life-threatening bleed. Although the current standard of care involves prophylactic replacement therapy of factor VIII, the development of neutralizing anti-factor VIII alloantibody inhibitors often complicates such therapeutic treatment. Emicizumab (Hemlibra®), a novel recombinant therapeutic agent for patients with hemophilia A, is a humanized asymmetric bispecific IgG4 monoclonal antibody designed to mimic activated factor VIII by bridging factor IXa and factor X thus effecting hemostasis. Importantly, this drug eliminates the need for factor VIII and complications associated with inhibitor generation. Emicizumab has been approved for use in several countries including the United States and Japan for prophylaxis of bleeding episodes in hemophilia A with and without FVIII inhibitors. Therapy is also approved in the European Union for routine prophylaxis of bleeds in hemophilia A with inhibitors or severe hemophilia A without inhibitors. Unfortunately, emicizumab therapy presents unique challenges for routine and specialty coagulation tests currently used to monitor hemophilia A. In this review, hemophilia A is presented, the biochemistry of factor VIII is discussed, and the impact of the therapeutic agent emicizumab is highlighted.

Decrease in in vivo coagulant potential of emicizumab in a patient with hemophilia A and inhibitor complicated with infectious mononucleosis

Emicizumab prophylaxis significantly reduces bleeding episodes in patients with hemophilia A (PwHA). There is little information on coagulant potentials in emicizumab-treated PwHA with infection, however. We encountered an emicizumab-treated PwHA with inhibitor, complicated with Epstein-Barr virus-associated infectious mononucleosis (IM) in phase 1/2 study (ACE001JP/ACE002JP). Although it was a typical clinical course of IM, activated partial thromboplastin time was mildly prolonged but rotational thromboelastometry revealed severely impaired coagulant potential. The blood concentration of emicizumab decreased moderately in the low concentration range, resulting in an increased risk of bleeding and possibly leading to severe ileocecal bleeds requiring coil embolization. The blood concentrations of factors IX/X little decreased and antiemicizumab antibodies did not develop, however. After the influence by IM resolved, his coagulant potentials gradually recovered with the recovery of emicizumab concentration, and parameters by global coagulation assays improved. An IM case for emicizumab-treated PwHA may need to monitor using global coagulation assays.

Hepatitis C Virus Infections in Patients with Hemophilia: Links, Risks and Management

Haemophilia is a rare, hereditary bleeding disorder. Clotting factor concentrates were a revolutionary treatment which changed the life of people with haemophilia. However, early generation of clotting factor concentrates, without viral inactivation procedures in the manufacturing process, led to an increased risk of transmission of blood-borne viral infections, mainly due to hepatitis C virus and human immunodeficiency virus. As only 20% of HCV-infected patients clear the infection naturally, chronic HCV infection constitutes a serious health problem and a major cause of chronic liver disease in this group of patients. Fortunately, the use of viral inactivation procedures in the plasma-derived factor concentrates manufacturing process and the availability of alternative treatment options, led to a significant reduction of transfusion-associated viral infections. The advent of multiple, orally administrated, highly effective direct-acting antivirals (DAAs) is changing the natural history of HCV infection in patients with haemophilia as these drugs have an excellent safety profile and achieve very high sustained virological response rates, similar to the general population. Eradication of HCV-infection in patients with haemophilia is feasible via micro-elimination projects.

Updates on Novel Non-Replacement Drugs for Hemophilia

Over the last decade, the world of hemophilia has experienced an unprecedented therapeutic advance, thanks to the progress in bioengineering technologies, leading to the introduction of drugs with novel mechanisms of action based on restoring thrombin generation or coagulation factor VIII mimicking. Apart from the bispecific monoclonal antibody emicizumab, already approved for patients with severe hemophilia A with and without inhibitors, novel non-replacement drugs designed to reduce the treatment burden of patients with hemophilia A or B with or without inhibitors are undergoing evaluation in clinical trials. Thanks to their innovative mechanism of action and subcutaneous administration, these drugs promise to provide effective bleeding protection together with improved adherence and improve health-related quality of life for patients with hemophilia. On the other hand, rare thromboembolic events have been reported with some of these drugs and warrant continuous post-marketing surveillance and investigation of predisposing factors, although the overall safety profile of most of these drugs is good. Finally, new challenges need to be faced in the clinical and laboratory monitoring of the hemostatic status in patients treated with these innovative therapies. In this review, we provide an update on the available data on novel non-replacement drugs currently undergoing evaluation in clinical trials for patients with hemophilia.

Multiple criteria decision analysis for therapeutic innovations in a hemophilia care center: A pilot study of the organizational impact of innovation in hemophilia care management

Background

Several innovative drugs liable to lead to changes in healthcare organization are or soon will be available for the management of hemophilia. Analyzing their implementation can shed further light on healthcare decision-making, to anticipate changes and risk of breakdown in the patient’s care pathway.

Methods

Multiple criteria decision analysis (MCDA), based on ISPOR recommendations, was used to assess the organizational impact of innovation in hemophilia care management. The MCDA process designed for this specific context involved ten French experts in hemophilia care management (physicians, nurses, pharmacist, physiotherapist and psychologist) in the hemophilia care center of Chambéry, in the Rhône-Alpes Region of France. This pilot study involved seven steps: (i) defining the decision problem; (ii) selecting and structuring criteria; (iii) assessing the relative weight of each criterion with software-assisted simulation based on pairwise comparisons of different organizational change scenarios; (iv) measuring the performance of the selected innovations; (v) scoring alternatives; (vi) calculating aggregate scores; (vii) discussion. The endpoint was to determine the expected overall organizational impact on a 0–100 scale.

Results

Seven organizational criteria were selected. "Acceptability for patient/caregiver/association" was the most heavily weighted. Factor VIII by subcutaneous route obtained the highest aggregate score: i.e., low impact on care organization (88.8 out of 100). The innovation with strongest organizational impact was gene therapy (27.3 out of 100).

Conclusion

This approach provided a useful support for discussion, integrating organizational aspects in the treatment decision-making process, at healthcare team level. The study needs repeating in a few years’ time and in other hemophilia centers.

Monoclonal antibodies used for the management of haematological disorders

INTRODUCTION

Monoclonal antibodies Ab (MoAb) are increasingly becoming part of therapeutic armamentarium for haematologists and haemato-oncologists. This review brings together commonly used antibodies in one place for brevity and novel understanding.

AREAS COVERED

Pubmed and Scopus databases were explored focusing on MoAb in clinical haematological practice. Emphasis was given to current review articles. The data base was searched from 1997 till present. 24 different antibodies, most of which are in use were discussed. Antibodies are used for diverse conditions i.e. malignant and benign haematological conditions, treatment at various phases of stem cell transplantation. These antibodies were used both alone or in combination with various chemotherapy, targeted small molecules or as immunoconjugates. Some of the side effect profiles of these antibodies were common and some were unique. Unusual infections or organ dysfunctions were noted. Improved function of antibodies by protein engineering is also advancing rapidly. Dosage, frequency and route of administration depended on the convenience and condition for which the antibody is used.

EXPERT OPINION

: MoAbs are increasingly used in haematology practice either alone or in combination with other types of therapy for improved out come in various haematological conditions.

A preliminary application of a haemophilia value framework to emerging therapies in haemophilia

INTRODUCTION

Emergence of new therapies are anticipated to improve clinical outcomes and quality of life of persons with haemophilia. Challenges in conducting randomized clinical trials in rare diseases have resulted in a lack of direct head-to-head comparisons to support value-based decision-making between different treatments.

METHODS

We conducted a literature review for new and emerging haemophilia A and B therapies (extended half-life [EHL] replacement factor, non-replacement therapies [NRT], and gene therapies [GT]) to identify differentiating patient-centred outcomes defined previously in a haemophilia value framework. Since the literature included all publication types (e.g., surveys, modelling studies, commentaries/reviews), collected data were assigned level of evidence scores.

RESULTS

Across different classes of therapies, bleeding was determined as the most frequently reported differentiating outcome, with EHL, NRT, and GT each demonstrating an advantage over comparator replacement therapies. EHL therapies for haemophilia A and B and NRT for haemophilia A showed good representation across Tier 1 outcomes (health status achieved/retained), while more publications were identified with Tier 2 (process of recovery) outcomes for NRT than EHL or GT. In Tier 3 (sustainability of health), frequency of breakthrough bleeds represented a differentiating outcome for EHL (both haemophilia A and B), NRT (haemophilia A only), and GT (haemophilia B only), whereas sustained good health was differentiating for most comparisons.

CONCLUSIONS

We demonstrate the utility of the haemophilia value framework as a common core outcome set for effectively comparing therapies. Application of this framework will serve as a useful decision-making tool for patients, clinicians, and within health technology assessments.

KEY POINTS OF CONSIDERATION

With the emergence of high-cost, paradigm changing treatments across multiple areas of medicine, we, the haemophilia community, need to be equipped to meet the growing demands for more rigorous evidence-based value assessments using the tools expected by assessors. The traditional access toolbox needs to evolve to meet the paradigm shift in treatment options. Value can no longer be defined by annualized bleed rates alone. To realize the full impact of new therapies, we need to utilize tools, such as a value framework, to organize evidence, identify data gaps, and assess patient-defined, meaningful outcomes across a multi-faceted dimension. The haemophilia value framework is an effective tool for organizing the available evidence and identifying gaps in the evidence. This can be used for assessing the value of emerging therapies in haemophilia utilizing data generated through randomized clinical trials and real world evidence generation. This is a call for incorporating the Value Framework into official submissions to authorities, as it captures a broader range of outcomes, including patient meaningful outcomes, in ways that better assess the potential benefits of new therapies.

Long-term efficacy and safety of subcutaneous concizumab prophylaxis in hemophilia A and hemophilia A/B with inhibitors

Despite current treatments, there remains an unmet need for patients with hemophilia. The main parts of two phase 2 trials established clinical proof-of-concept for once-daily, subcutaneous concizumab prophylaxis in patients with hemophilia A/B with inhibitors (HAwI/HBwI; explorer4) and severe hemophilia A without inhibitors (HA; explorer5,). Here, we present results from extension parts of these trials, included to evaluate longer-term safety and efficacy. Both trials included main (≥24 weeks) and extension parts (52-102 weeks), with patients receiving 0.15 mg/kg concizumab with potential dose escalation to 0.20 or 0.25 mg/kg if they experienced ≥3 treated spontaneous bleeds within 12 weeks. Endpoints included annualized bleeding rate (ABR), adverse events (AEs), and anti-drug antibody (ADA) occurrence. Thromboembolic events were AEs of special interest. Thirty-six patients with HA, 15 with HAwI and 10 with HBwI were exposed to concizumab. Estimated ABRs during the main+extension parts at last dose level were 4.8 (95% confidence interval [CI]: 3.2-7.2) and 6.4 (95% CI: 4.1-9.9) in explorer4 and explorer5, respectively (spontaneous ABRs were 1.8 [95% CI: 1.2-2.6] and 2.1 [95% CI: 1.3-3.3]). Most AEs were mild, with no deaths, events leading to withdrawal or thromboembolic events. ADAs developed in 25% of patients and were low titer and transient with no observed clinical effect in most cases. Results of the main+extension parts of these trials were consistent with the main parts. Ongoing phase 3 trials will further evaluate concizumab as a once-daily, subcutaneous treatment across hemophilia subtypes. Trials registered at www.clinicaltrials.gov (NCT03196284; NCT03196297).

Prophylactic emicizumab for hemophilia A in the Asia‐Pacific region: A randomized study (HAVEN 5)

Background

Methods

Results

Conclusion

Cardiovascular disease in hereditary haemophilia: The challenges of longevity

The development of effective and safe treatments has significantly increased the life expectancy of persons with haemophilia (PWH). This has been accompanied by an increase in the comorbidities of ageing including cardiovascular disease, which poses particular challenges due to the opposing risks of bleeding from haemophilia and antithrombotic treatments versus thrombosis. Although mortality secondary to coronary artery disease in PWH is less than in the general population, the rate of atherosclerosis appears similar. The prevalence of atrial fibrillation in PWH and risk of secondary thromboembolic stroke are not well established. PWH can be safely supported through acute coronary interventions but data on the safety and efficacy of long‐term antithrombotics are scarce. Increased awareness and research on cardiovascular disease in PWH will be crucial to improve primary prevention, acute management, secondary prevention and to best support ageing PWH.

Targeting hypercoagulation to alleviate Alzheimer's disease progression in metabolic syndrome

INTRODUCTION

Metabolic Syndrome (MetS) constitutes an important risk factor for Alzheimer's disease (AD); however, the mechanism linking these two disorders has not been completely elucidated. Hence, hypercoagulation may account for the missing hallmark connecting MetS and AD. The present review proposes how hemostatic imbalance triggered in MetS advances in the context of AD. MetS causes interruption of insulin signaling and inflammation, inciting insulin resistance in the brain. Subsequently, neuroinflammation and brain endothelial dysfunction are prompted that further intensify the exorbitant infiltration of circulating lipids and platelet aggregation, thereby causing hypercoagulable state, impairing fibrinolysis and eventually inducing prothrombic state in the brain leading to neurodegeneration.

OBJECTIVE

This study aims to understand the role of hypercoagulation in triggering the progression of neurodegeneration in MetS. It also offers a few interventions to prevent the progression of AD in MetS targeting hypercoagulation.

METHODS

Literature studies based on MetS related neurodegeneration, the impact of coagulation on aggravating obesity and AD via the mechanisms of BBB disruption, neuroinflammation, and hypofibrinolysis.

CONCLUSION

The present paper proposes the hypothesis that hypercoagulation might amplify MetS associated insulin resistance, neuroinflammation, BBB disruption, and amyloid beta accumulation which eventually leads to AD.

Overcoming the challenges of treating hemophilia in resource-limited nations: a focus on medication access and adherence

BACKGROUND

Hemophilia is a high cost low volume disease. Resource limited nations (RLN) usually spend very little on health budget and most of it is spent in dealing with common ailments. Clotting products constitute more than 90% of the total cost of hemophilia care. The manner in which these products can be made accessible for persons with hemophilia (PWH) and how its continuous supply and distribution can be maintained and improved is described in this review.

AREAS COVERED

Number of PWH in the Resource Limited Nations (RLN); minimum amount of concentrate required to keep a PWH relatively free of bleeds; the different products available for management of PWH; means and ways to minimize and optimize the concentrate usage and purchase on a budget; nonfactor therapy; ways and means to improve the management and allow better quality concentrates in higher quantities for PWH in those countries; adherence as a challenge for RLN country and ways to manage them. The time covered is from 1980s till date. Pubmed was searched mainly for review articles with the key words hemophilia, RLN, concentrate access, alternative therapy. Cross references from these reviews as well as some of the abstracts from international conferences were read.

EXPERT OPINION

Developing a patient's society and a bleeding disorder registry are the two most important actions toward ensuring adequate treatment material for PWH in RLN. Government should allocate a budget for hemophilia care depending on the number of PWH diagnosed and future projection of increased numbers of PWH. Population based product requirement may not work initially as only 10-20% of PWH in such a country has been diagnosed hence initial requirement of concentrates should be directed to these patients. Meanwhile efforts should be made to diagnose new cases. Antenatal diagnosis centers should offer antenatal diagnosis and prevent birth of severe hemophilia children. Self sufficiency in plasma based concentrates should be planned and aimed. A national tendering committee can get a good price on the concentrates on global tendering with annual rate contracts (prevents outdating). Avoiding wastage by outdating of the products in large denomination vials will help. Hoarding concentrates in unreasonable amounts should be avoided through good supply chain management. Regular physiotherapy, proper use of optimum amounts of concentrate will reduce per PWH consumption of the factor concentrates. Plasma derived intermediate purity factors, first/second generation recombinant clotting factors are safe and relatively cheaper as well as effective. Also concentrates which are close to their expiry date (>3 < 6 months) are equally effective and cheap. With proper supply chain management such products can be included in the portfolio. Primary prophylaxis with low/ intermediate dose of the concentrates is a cost-effective way to manage the patients and this also reduces inhibitor development. Adherence to therapy is not yet an important issue for RLN countries but will become one in future. With advancement and improvement the country can access alternative non factor concentrates and other newer products.

MRI predicts 5-year joint bleeding and development of arthropathy on radiographs in hemophilia

Magnetic resonance imaging (MRI) is considered as the reference standard to assess early joint changes in hemophilia. However, the clinical relevance of MRI findings is still unknown. The aim of this prospective study was to assess the predictive value of MRI for 5-year joint bleeding and progression of arthropathy in patients with hemophilia. Both knees and ankles of patients with hemophilia and absent or limited arthropathy on radiographs were assessed by using MRI and radiographs. MRI scans were scored according to the International Prophylaxis Study Group MRI score for hemophilic arthropathy. Patients were followed up for 5 years, including assessment of joint bleeding and repeated radiographic assessment. Associations between baseline MRI findings with 5-year bleeding and progression of arthropathy were expressed as odds ratios (OR), adjusted for severity of disease and joint bleeding history. Baseline assessment included 104 joints of 26 patients with hemophilia (median age, 21 years). Four ankles with severe joint changes were excluded. Follow-up was available for 96 (92%) of 104 joints. During 5 years of follow-up, bleeding was reported for 36% of joints. Five-year bleeding was significantly increased in joints with synovial hypertrophy at 80% vs 27% in joints without synovial hypertrophy (OR, 10.1; 95% confidence interval, 3.4-31.3). In joints with normal baseline radiographs, any osteochondral or synovial changes on MRI were associated with radiographic changes 5 years later (positive predictive value, 75%; negative predictive value, 98%). Joints with synovial hypertrophy on MRI had a significantly higher chance of 5-year bleeding. All MRI changes, except effusion, were strong predictors for development of arthropathy on radiographs.

Laboratory monitoring of hemophilia A treatments: new challenges

Monitoring factor VIII (FVIII) activity has traditionally been complicated by discrepancies between assays for the various sorts of FVIII molecules. The advent of novel nonfactor therapies (emicizumab, fitusiran, and anti-tissue factor pathway inhibitor antibodies) in hemophilia A poses a new level of difficulty on the laboratory monitoring of these patients. To use the correct assays and for a proper interpretation of their results, it is pertinent to understand the mode of action of these nonfactor agents. Furthermore, the biochemical consequences for the different types of activity assays (whether it be specific FVIII activity assays or global coagulation assays) should be taken into account as well. In this review, these aspects will be discussed. In addition, the use of various animal models to estimate FVIII-equivalence of the nonfactor therapies will be presented.

Optimizing language for effective communication of gene therapy concepts with hemophilia patients: a qualitative study

BACKGROUND

For communities of people living with hemophilia and other genetic conditions, gene therapy could represent a paradigm shift in treatment strategies. As investigational therapeutic modalities such as gene therapy become more widely used and discussed, there is a critical need for all stakeholders to communicate using a lexicon that is intelligible, accurate, consistent, and representative of novel treatments. In doing so, expectations can be more carefully managed and potential risks, benefits, and limitations better understood. In recognition of this need, a first-ever study of gene therapy lexicon was conducted using established methods of market research and linguistic analysis.

METHODS

Ninety-four participants representing hematologists, nurses, caregivers, and people with hemophilia A, in six countries (US, UK, Spain, Germany, France, Italy) took part in a series of in-depth interviews, face-to-face focus groups, an advisory board meeting, and online group interviews to develop, refine, and test verbal, written, and pictorial language concepts through a three-phase iterative process. Sessions were conducted in local languages using detailed discussion guides. Feedback from participants was captured using real-time instant-response dial testing to measure moment-by-moment emotional responses to language stimuli. Semiquantitative analysis of the responses informed selection of preferred language concepts for final testing, and qualitative discussion explored preference rationale. Participants also completed polling and forced rank and choice written exercises.

RESULTS

Study feedback showed that the hemophilia community has preferences around consistent lexicon to describe hemophilia and its management. Expert linguistic analysis of feedback from the three phases enabled agreement of a consensus lexicon of vocabulary and an optimized summary narrative for talking about gene therapy amongst people affected by hemophilia A. Preferences were largely consistent across audiences and countries, although some country-specific recommendations were made. A representative summary phrase was agreed: "Gene therapy is being studied in clinical trials with the aim to allow the body to produce factor VIII protein on its own".

CONCLUSIONS

The use of preferred language across different stakeholders increases understanding and comfort during discussions of novel and complex therapeutic modalities such as gene therapy. Consistent use of community-informed lexicon minimizes miscommunication and facilitates informed decision-making regarding potential future treatment opportunities.

microRNAs as Novel Therapeutics in Cancer

Simple Summary

Over the last few years, we have witnessed incredible advancements in anti-tumor drug development. microRNAs, a class of small non-coding RNAs dysregulated in all cancers, have been recently elected as candidate therapeutics for treating a variety of diseases, including cancer. The scope of this review is to give some insight into the role of the most relevant microRNAs in cancer. We will focus on examining their biological role in tumor development while also providing a broad overview of microRNAs as therapeutics. There is a dedicated focus on the different methods available for microRNA delivery in addition to the efforts being made to increase the specificity of these delivery methods. Finally, we discuss the ongoing clinical trials that are using microRNAs for cancer treatment.

Abstract

In the last 20 years, the functional roles for miRNAs in gene regulation have been well established. MiRNAs act as regulators in virtually all biological pathways and thus have been implicated in numerous diseases, including cancer. They are particularly relevant in regulating the basic hallmarks of cancer, including apoptosis, proliferation, migration, and invasion. Despite the substantial progress made in identifying the molecular mechanisms driving the deregulation of miRNAs in cancer, the clinical translation of these important molecules to therapy remains in its infancy. The paucity of vehicles available for the safe and efficient delivery of miRNAs and ongoing concerns for toxicity remain major obstacles to clinical application. Novel formulations and the development of new vectors have significantly improved the stability of oligonucleotides, increasing the effectiveness of therapy. Furthermore, the use of specific moieties for delivery in target tissues or cells has increased the specificity of treatment. The use of new technologies has allowed small but important steps toward more specific therapeutic delivery in tumor tissues and cells. Although a long road remains, the path ahead holds great potential. Currently, a few miRNA drugs are under investigation in human clinical trials with promising results ahead.

Ex Vivo Prediction of Comprehensive Coagulation Potential Using Simulated Blood Concentrations of Emicizumab in Patients with Acquired Hemophilia A

INTRODUCTION

 Emicizumab prophylaxis improves coagulation function in congenital hemophilia A, regardless of inhibitor presence. We recently reported that emicizumab enhanced the coagulant potentials, ex vivo, in plasmas from patients with acquired hemophilia A (PwAHAs) at diagnosis. However, coagulant effects of emicizumab in PwAHAs during the clinical course remain unclear.

AIM

 To assess ex vivo coagulant effects of emicizumab in PwAHAs during the clinical course.

METHODS/RESULTS

 Blood samples were obtained from 14 PwAHAs on (median) days 0 and 6 during a severe-bleeding phase, and days 27 and 59 during a reduced-bleeding phase with elevated endogenous factor VIII (FVIII) and decreased inhibitor titers. If administered a single dose of 3 or 6 mg/kg, or two doses at 6 mg/kg followed by 3 mg/kg, estimated plasma emicizumab concentrations (10/5/2.5, 20/10/5, and 30/15/7.5 µg/mL on days 0-7/30/60, respectively) could be used to represent potential changes, based on the half-life (T _1/2: ∼30 days). Emicizumab concentrations that covered maximum plasma concentrations of each dosage were used for spiking on day 0. Ex vivo addition of estimated emicizumab to PwAHA's plasma containing endogenous FVIII and/or inhibitor, without and with recombinant (r)FVIIa administration during immunosuppressive therapy, increased the calculated Ad|min1| values, assessed by clot waveform analysis, and their coagulant potentials were below normal levels. Rotational thromboelastometry revealed that ex vivo emicizumab addition resulted in the further improvement of coagulant potentials in whole bloods when combined with rFVIIa administration.

CONCLUSION

 Based on ex vivo and in vitro data, emicizumab has the potential to be effective in clinical situations for PwAHAs.

Predicted coagulation potential using an in vitro simulated model of emicizumab prophylaxis and immune tolerance induction therapy in hemophilia A patients with inhibitor

Emicizumab reduces bleeding in hemophilia A patients with inhibitor (HA-inh). A combination of immune tolerance induction therapy (ITI) and emicizumab prophylaxis may provide additional benefits, but coagulation potential during this treatment remains unknown. We assessed coagulation potentials in simulated ITI models in vitro using modified-clot waveform analysis. Factor (F)VIII-deficient plasma preincubated with anti-A2 and anti-C2 monoclonal antibodies was reacted with emicizumab (50 µg/mL) (emicizumab-HA-plasma), then spiking bypassing agents (BPAs): activated prothrombin complex concentrates (aPCC 1.3 IU/mL; 50 IU/kg), recombinant factor (rF)VIIa (2.2 µg/mL; 90 µg/kg), and FVIIa/FX (1.5 µg/mL; 60 µg/kg), and/or FVIII (100, 200 IU/dL). Coagulation potentials in emicizumab-HA-plasma (10 BU/mL) remained within the normal range when BPA and FVIII were both present. In emicizumab-HA-plasma (1 BU/mL) with BPA and FVIII (200 IU/dL), they were near or beyond the normal range, but those with a half concentration of rFVIIa based on the half-life in blood were within the normal range. In samples without inhibitor, coagulation potentials with combined BPA and FVIII were far beyond the normal range but with FVIII (100 IU/dL) and rFVIIa at half concentration they remained within the normal range. These results may provide information on the feasibility of concurrent ITI under emicizumab prophylaxis.

Outcome measures in Haemophilia: Beyond ABR (Annualized Bleeding Rate)

Options for management of haemophilia are increasing rapidly with completely novel therapeutic approaches that cannot be compared using traditional factor assays. In addition, as prophylaxis regimens have improved, bleeding rates have decreased, and consequently, it is difficult to show an impact of novel therapies on rates of spontaneous bleeding. There is currently an urgent need for a panel of outcome measures to compare therapies that are dissimilar in many essential ways. Conventional objective outcome measures including joint physical examination and joint imaging continue to hold a central importance. Factor assays are essential for evaluation of products derived from native factor genes, but are not applicable to some extended half-life factors or non-factor bypassing agents. Global assays including thrombin generation and chromogenic assays of factor X activation are under investigation for their usefulness in haemophilia assessment. Bleeding rate is a conventional subjective patient-reported outcome that, while decreasing in frequency, is indispensable as an outcome given that the primary manifestation of haemophilia is bleeding. Other patient-reported outcomes such as pain intensity and interference, health-related quality of life and activities and participation are increasingly important to distinguish superior outcomes in comparative trials. This review of outcome measures for haemophilia presents examples of existing outcome measures with an emphasis on their strengths and limitations.

Origins, Development, Current Challenges and Future Directions with Activated Prothrombin Complex Concentrate for the Treatment of Patients with Congenital Haemophilia with Inhibitors

Congenital haemophilia A (HA) is caused by deficiency of coagulation factor VIII (FVIII) activity, leading to spontaneous or traumatic bleeding events. While FVIII replacement therapy can treat and prevent bleeds, approximately 30% of patients with severe HA develop inhibitor antibodies that render FVIII replacement therapy ineffective. The bypassing agents (BPAs), activated prothrombin complex concentrate (aPCC) and recombinant activated FVII, first approved in 1977 and 1996, respectively, act to generate thrombin independent of pathways that involve factors IX and VIII. Both may be used in patients with congenital haemophilia and inhibitors (PwHIs) for the treatment and prevention of acute bleeds and quickly became standard of care. However, individual patients respond differently to different agents. While both agents are approved for on-demand treatment and perioperative management for patients with congenital haemophilia with inhibitors, aPCC is currently the only BPA approved worldwide for prophylaxis in PwHI. Non-factor therapies (NFTs) have a mechanism of action distinct from BPAs and have reported higher efficacy rates as prophylactic regimens. Nonetheless, treatment challenges remain with NFTs, particularly regarding the potential for synergistic action on thrombin generation with concomitant use of other haemostatic agents, such as BPAs, for the treatment of breakthrough bleeds and in perioperative management. Concomitant use of NFTs with other haemostatic agents could increase the risk of adverse events such as thromboembolic events or thrombotic microangiopathy. This review focuses on the origins, development and on-going role of aPCC in the evolving treatment landscape in the management of PwHI.

Understanding Early Hemophilic Arthropathy in Children and Adolescents Through MRI T2 Mapping

BACKGROUND

Persons with hemophilia experience hemarthrosis, which can lead to cartilage degeneration, causing physical impairment. MRI T₂ mapping has the potential to be used as a tool to evaluate early arthropathic changes and cartilage degeneration in patients with hemophilia.

PURPOSE

To assess the value of MRI-T₂ mapping as a tool for investigating the cartilage status of children and adolescents with hemophilic arthropathy.

STUDY TYPE

Prospective, cross-sectional.

SUBJECTS

Twenty-eight boys with hemophilia (aged 5-17 years) and 23 healthy boys (aged 7-17 years).

FIELD STRENGTH/SEQUENCES

A multiecho spin-echo T₂ -weighted gradient echo sequence was used on a 3.0T magnet.

ASSESSMENT

MRI-T₂ maps of ankle (tibia-talus) (n = 19) or knee (femur-tibia) (n = 9) cartilage were assessed in hemophilia and healthy groups. An anatomically-based MRI score was also assigned to each ankle/knee.

STATISTICAL TESTS

Pearson's correlation coefficient (r), linear regression, intraclass correlation coefficient (ICC), and analysis of variance (ANOVA) test.

RESULTS

Negative associations between age and ankle/knee cartilage T₂ relaxation times were found in hemophilia (r = -0.72 [P = 0.03] to -0.55 [P = 0.01]) and healthy (r = -0.84 [P < 0.001] to -0.55 [P = 0.20]) groups. There were nonsignificant associations between ankle cartilage T₂ relaxation times and MRI scores (r = -0.15 [P = 0.54] to 0.31 [P = 0.19]).

DATA CONCLUSION

Results of this clinical investigation emphasize the potential importance of MRI-T₂ maps as a tool to understand the functional status of cartilage in children and adolescents with hemophilic arthropathy, while holding promise for the detection of early cartilage degeneration prior to macroscopic characterization by conventional MRI. MRI-T₂ mapping may provide novel information that is not reflected in the anatomically-based MRI scoring system.

LEVEL OF EVIDENCE

3 TECHNICAL EFFICACY STAGE: 2.

Emicizumab-Induced Seronegative Full-House Lupus Nephritis in a Child

Hemophilia A (HA) is a serious inherited bleeding disorder resulting from a deficiency of coagulation factor VIII (FVIII). Replacement therapy with intravenous infusion of FVIII can be associated with treatment failure in approximately one-third of patients secondary to the development of neutralizing alloantibodies (inhibitor). Emicizumab is a recombinant, humanized, bispecific monoclonal antibody that binds factor IXa and factor X and mimics FVIII. It has been licensed in many countries for the treatment of patients with HA with and without inhibitors with a favorable efficacy and safety profile. A 7-year-old child with severe HA and FVIII inhibitors, refractory to immune tolerance therapy, developed hematuria with nephrotic-range proteinuria after the first dose of emicizumab and subsequently also after a second dose 6 weeks later, which was associated with mild and transient leukopenia. Renal biopsy revealed a pattern of a full-house lupus nephritis. The patient fully and spontaneously recovered between 2 weeks after symptoms onset. In this report, we provide insights on a new and so far unreported renal complication associated to emicizumab treatment. Although emicizumab offers significant benefits for patient with HA, clinicians should be aware of this rare and potential serious renal adverse effect.

Serpins, New Therapeutic Targets for Hemophilia

Hemostasis is a tightly regulated process characterized by a finely tuned balance between procoagulant and anticoagulant systems. Among inherited hemostatic conditions, hemophilia is one of the most well-known bleeding disorders. Hemophilia A (HA) and B (HB) are due to deficiencies in coagulation factor VIII (FVIII) or FIX, respectively, leading to unwanted bleeding. Until recently, hemophilia treatment has consisted of prophylactic replacement therapy using plasma-derived or recombinant FVIII in cases of HA or FIX in cases of HB. Because FVIII and FIX deficiencies lead to an imbalance between procoagulant and anticoagulant systems, a recent upcoming strategy implies blocking of endogenous anticoagulant proteins to compensate for the procoagulant factor deficit, thus restoring hemostatic equilibrium. Important physiological proteins of the anticoagulant pathways belong to the serpin (serine protease inhibitor) family and, recently, different experimental and clinical studies have demonstrated that targeting natural serpins could decrease bleeding in hemophilia. Here, we aim to review the different, recent studies demonstrating that blocking serpins such as antithrombin, protein Z-dependent protease inhibitor, and protease nexin-1 or modifying a serpin like α1-antitrypsin could rebalance coagulation in hemophilia. Furthermore, we underline the potential therapeutic use of serpins for the treatment of hemophilia.

Emicizumab Augments Thrombus Formation in Whole Blood from Patients with Hemophilia A under High Shear Flow Conditions

BACKGROUND

 Emicizumab is a bispecific antibody to factor (F) IXa and FX that mimics the FVIIIa cofactor function. Emicizumab prophylaxis markedly decreases bleeding episodes in patients with hemophilia A (PwHAs), irrespective of the presence of FVIII inhibitors. However, thrombotic microangiopathy (TMA) was reported when repeated high doses of activated prothrombin complex concentrates (aPCC) were concomitantly used with emicizumab. Although bypassing agents (BPAs) are vital in the hemostatic treatment for PwHAs with inhibitors, the mechanism of emicizumab-related TMA remains unclear.

AIM

 To assess the risk of excessive thrombus formation associated with BPAs and emicizumab under high shear conditions.

METHODS

 Perfusion flow-chamber experiments under high shear conditions were performed using whole blood from PwHAs in the presence of emicizumab without or together with FVIII or BPAs ex vivo.

RESULTS

 Emicizumab (100 μg/mL) added ex vivo to whole blood from PwHAs improved defective thrombus formation in a similar manner to that observed with the addition of recombinant FVIII at the early phase, while FVIII continued to be important at the later stages. aPCC (1.2 U/mL equivalent to 100 U/kg) or recombinant FVIIa (1.1 µg/mL; equivalent to 90 µg/kg) together with emicizumab further promoted platelet interactions and fibrin formation ex vivo but did not induce excessive thrombus formation.

CONCLUSION

 Emicizumab enhanced thrombin generation at local sites and improved defective hemostasis in whole blood from PwHAs under high shear conditions. Simple concomitant use of BPAs with emicizumab did not mediate excessive thrombus formation and remains an option for hemostatic management of emicizumab-treated PwHAs with inhibitors.

Reduced-intensity, risk factor-stratified immunosuppression for acquired hemophilia A: single-center observational study

Immunosuppressive therapy (IST) is administered to patients with acquired hemophilia A (AHA) to eradicate autoantibodies against coagulation factor VIII (FVIII). Data from registries previously demonstrated that IST is often complicated by adverse events, in particular infections. This pilot study was set out to assess the feasibility of reduced-intensity, risk factor–stratified IST. We followed a single-center consecutive cohort of twenty-five patients with AHA receiving IST according to a new institutional treatment standard. Based on results from a previous study, GTH-AH 01/2020, patients were stratified into “poor risk” (FVIII < 1 IU/dl or inhibitor ≥ 20 Bethesda units (BU)/ml) or “good risk” (FVIII ≥ 1 IU/dl and inhibitor < 20 BU/ml). Outcomes were compared between the current cohort and the GTH registry as a historic control (n = 102). Baseline characteristics of the cohort were not different from the historic control. Partial remission, defined as FVIII recovered to > 50 IU/dl, was achieved by 68% of patients after a median time of 112 days, which was lower and significantly later than in the historic control (hazard ratio: 1.8, 95% confidence interval 1.2–2.8). Complete remission, overall survival, and frequency of fatal infections were not different. Grade 3 and 4 infections were more frequent. The impact of risk factors that was observed in the historic cohort was no longer apparent, as partial and complete remission and overall survival were similar in “good risk” and “poor risk” patients. In conclusion, reduced-intensity, risk factor–stratified IST is feasible in AHA but did not decrease the risk of infections and mortality in this cohort.

Laboratory testing in hemophilia: Impact of factor and non-factor replacement therapy on coagulation assays

The advent of extended half-life (EHL) recombinant clotting factors and innovative non-factor replacement therapeutics, such as emicizumab, offers several advantages over existing products for the prophylactic treatment of people living with hemophilia (PwH). These include low annual bleeding rates with less frequent dosing, higher trough plasma concentrations, and a more convenient route of administration. However, increasing use of these therapies poses challenges to clinicians and coagulation laboratories due to the lack of standardized assays for monitoring of hemostatic parameters, and the potential for misinterpretation of test results, which may jeopardize patient safety. Definitive diagnosis of hemophilia and treatment monitoring is reliant on demonstrating factor VIII (FVIII; hemophilia A) or factor IX (FIX; hemophilia B) deficiency using a functional coagulation assay. The most frequently used assays are based on activated partial thromboplastin time, using a one-stage or two-stage process. While one-stage and chromogenic assays have performed well with human-derived FVIII and FIX and full-length recombinant products, EHL recombinant factors are heterogeneous in structure and mode of action and therefore show wide variation in activity levels between different one-stage assays, and between one-stage and chromogenic assays. In the context of the recommended stepwise approach for laboratory diagnosis of hemophilia, we examine the diagnostic challenges associated with the use of EHL factors and novel non-factor therapeutics and consider the optimal diagnostic approach in PwH who are receiving these treatments. Ultimately, accurate diagnostic solutions are a prerequisite for personalized therapy to minimize treatment burden and improve quality of life in PwH.

Role of Small Intestine and Gut Microbiome in Plant-Based Oral Tolerance for Hemophilia

Fusion proteins, which consist of factor VIII or factor IX and the transmucosal carrier cholera toxin subunit B, expressed in chloroplasts and bioencapsulated within plant cells, initiate tolerogenic immune responses in the intestine when administered orally. This approach induces regulatory T cells (Treg), which suppress inhibitory antibody formation directed at hemophilia proteins induced by intravenous replacement therapy in hemophilia A and B mice. Further analyses of Treg CD4+ lymphocyte sub-populations in hemophilia B mice reveal a marked increase in the frequency of CD4+CD25-FoxP3-LAP+ T cells (but not of CD4+CD25+FoxP3+ T cells) in the lamina propria of the small but not large intestine. The adoptive transfer of very small numbers of CD4+CD25-LAP+ Treg isolated from the spleen of tolerized mice was superior in suppression of antibodies directed against FIX when compared to CD4+CD25+ T cells. Thus, tolerance induction by oral delivery of antigens bioencapsulated in plant cells occurs via the unique immune system of the small intestine, and suppression of antibody formation is primarily carried out by induced latency-associated peptide (LAP) expressing Treg that likely migrate to the spleen. Tolerogenic antigen presentation in the small intestine requires partial enzymatic degradation of plant cell wall by commensal bacteria in order to release the antigen. Microbiome analysis of hemophilia B mice showed marked differences between small and large intestine. Remarkably, bacterial species known to produce a broad spectrum of enzymes involved in degradation of plant cell wall components were found in the small intestine, in particular in the duodenum. These were highly distinct from populations of cell wall degrading bacteria found in the large intestine. Therefore, FIX antigen presentation and Treg induction by the immune system of the small intestine relies on activity of a distinct microbiome that can potentially be augmented to further enhance this approach.

Bispecific Antibodies and Advances in Non-Gene Therapy Options in Hemophilia

Regular prophylaxis has markedly improved the treatment for patients with hemophilia A, especially after the introduction of highly purified factor VIII (FVIII) concentrates. However, frequent intravenous infusions and the development of FVIII inhibitors remain as unsolved difficulties. To overcome these unmet needs, a bispecific antibody mimicking activated FVIII has been developed in Japan. This bispecific antibody, emicizumab, recognizes activated factor IX (FIXa) and activated factor X (FXa), and promotes FIXa-catalyzed activation of FX in the absence of FVIII. Emicizumab initially reacts with FIXa generated by the action of factor VIIa/tissue factor complexes. Subsequently, thrombin generation is enhanced in the presence of higher amounts of FIXa derived from FXIa-dependent mechanisms. Hence, emicizumab-driven FXa and thrombin generation is maintained by a FXI activation loop in the intrinsic coagulation pathway. Reactions downstream of emicizumab are regulated by natural anticoagulants including activated protein C, antithrombin, and tissue factor pathway inhibitor. Phase 3 studies (HAVEN 1-4 and HOHOEMI studies) demonstrated a remarkable reduction in bleeding rates together with a high percentage of patients with zero treated bleeds irrespective of the presence of inhibitors. In general, emicizumab proved to be well tolerated, although isolated thromboembolic and thrombotic microangiopathic complications were observed in the HAVEN 1 studies, and 3 out of a total of 400 patients developed neutralizing antidrug antibodies. In addition, several questions remain to be discussed with respect to open-use clinical practice, including when to start treatment, how to monitor therapy, and optimum dosage for surgical procedures and immune tolerance induction.

Single-domain antibodies targeting antithrombin reduce bleeding in hemophilic mice with or without inhibitors

Novel therapies for hemophilia, including non-factor replacement and in vivo gene therapy, are showing promising results in the clinic, including for patients having a history of inhibitor development. Here, we propose a novel therapeutic approach for hemophilia based on llama-derived single-domain antibody fragments (sdAbs) able to restore hemostasis by inhibiting the antithrombin (AT) anticoagulant pathway. We demonstrated that sdAbs engineered in multivalent conformations were able to block efficiently AT activity in vitro, restoring the thrombin generation potential in FVIII-deficient plasma. When delivered as a protein to hemophilia A mice, a selected bi-paratopic sdAb significantly reduced the blood loss in a model of acute bleeding injury. We then packaged this sdAb in a hepatotropic AAV8 vector and tested its safety and efficacy profile in hemophilic mouse models. We show that the long-term expression of the bi-paratopic sdAb in the liver is safe and poorly immunogenic, and results in sustained correction of the bleeding phenotype in hemophilia A and B mice, even in the presence of inhibitory antibodies to the therapeutic clotting factor.

Antithrombin inhibition using nanobodies to correct bleeding in hemophilia

In this issue of EMBO Molecular Medicine, Barbon et al describe a new approach to rebalancing coagulation in patients with hemophilia (PWH) through targeted inhibition of anticoagulant antithrombin (AT) (Barbon et al, 2020). In contrast to previous studies that used RNA interference (RNAi) therapy to reduce AT levels (Sehgal et al, 2015; Pasi et al, 2017), the authors utilized llama‐derived single‐domain antibodies (sdAbs or nanobodies) to inhibit AT activity (Fig 1). These engineered sdAbs successfully restored thrombin generation in hemophilic plasma and corrected bleeding phenotype in a murine hemophilia model. Furthermore, long‐term AAV8‐mediated hepatic expression of the sdAb was well tolerated and associated with a sustained correction in bleeding in hemophilia A and B mice. Collectively, these exciting data uncover a novel AT‐targeting approach that may be useful as an alternative therapy for restoring normal hemostasis in PWH.

Prediction of the haemostatic effects of bypassing therapy using comprehensive coagulation assays in emicizumab prophylaxis-treated haemophilia A patients with inhibitors

In emicizumab prophylaxis, the concomitant therapy using bypassing agents (BPAs) is required for breakthrough bleeding and invasive procedures with attention to thrombotic complications. To predict coagulant effects of BPAs in emicizumab-treated patients with haemophilia A (PwHA) with inhibitor (PwHAwI), blood samples from emicizumab-treated PwHAwI (n = 8) and PwHA without inhibitor (n = 2) in phase 1/2 and HAVEN 1 study, spiked with activated prothrombin complex concentrates (aPCC) or recombinant factor VIIa (rFVIIa) ex vivo, and blood samples from emicizumab-treated PwHAwI-receiving BPAs were analysed by Ca²⁺ -triggered rotational thromboelastometry (ROTEM) and ellagic acid/tissue factor-triggered clot waveform analysis (CWA). Spiked aPCC, corresponded to 10-100 U/kg, markedly shortened ROTEM parameters beyond the normal range, while spiked rFVIIa, corresponded to 90-270 μg/kg, shortened them within near-normal range. Each of the spiked BPA-improved adjusted maximum coagulation velocity of CWA to within or near the normal range. In blood samples at post-infusion of aPCC (44-73 U/kg) or rFVIIa (79-93 μg/kg), the parameters of both assays improved to approximately the normal range. Taken together, ex vivo results of spiking tests in ROTEM and CWA, except aPCC spiking test in ROTEM, were relatively consistent with in vivo ones, and could usefully predict the coagulant effects of concomitant bypassing therapy for emicizumab-treated PwHAwI.

Pharmacokinetics, immunogenicity, safety, and preliminary efficacy of subcutaneous turoctocog alfa pegol in previously treated patients with severe hemophilia A (alleviate 1)

BACKGROUND

The current standard of care for patients with hemophilia A is regular prophylaxis with factor VIII (FVIII) administered intravenously. Interest in subcutaneous (s.c.) administration, to potentially increase convenience, reduce the treatment burden and improve compliance, is increasing.

OBJECTIVES

Evaluate the pharmacokinetics (PK), immunogenicity, safety, and preliminary efficacy of s.c. administration of turoctocog alfa pegol (s.c. N8-GP) in adult or adolescent previously treated patients (PTPs) with severe hemophilia A (alleviate 1; NCT02994407).

PATIENTS/METHODS

In part A, 24 PTPs received a single dose of s.c. N8-GP (12.5, 25, 50, or 100 IU/kg) with 6 patients per cohort. PK modelling of data from part A supported a suitable dose for part B. Part B comprised a multiple dose trial in 26 PTPs; patients <60 kg received 2000 IU and patients ≥60 kg received 4000 IU s.c. N8-GP daily for 3 months.

RESULTS

Single-dose s.c. N8-GP supported dose linearity. Daily prophylaxis with s.c. N8-GP appeared well tolerated and efficacious, achieving a mean trough FVIII activity close to 10% at steady state. Five patients developed anti-N8-GP binding antibodies after 42 to 91 exposure days, one of whom developed an inhibitor to FVIII. Anti-N8-GP antibody appearance was associated with a decline in FVIII plasma activity in four of the five patients. Five patients reported a total of nine treatment-requiring bleeding episodes during prophylaxis.

CONCLUSIONS

Subcutaneous administration of N8-GP is associated with a high incidence of antibodies in PTPs with severe hemophilia A. Further clinical development of s.c. N8-GP has been suspended.

Paradigm shift for the treatment of hereditary haemophilia: Towards precision medicine

Patients with haemophilia A (HA) or B (HB) experience spontaneous limb- or life-threatening bleedings which are prevented by regular prophylactic intravenous infusions of the deficient coagulation factor (FVIII or FIX). Prophylaxis with subcutaneous long-acting non-factor products that improve in vivo thrombin generation is now under intensive investigation (concizumab, fitusiran) or successfully employed (emicizumab) in haemophilia patients. Both haemophilia patients with/without inhibitors take advantage of non-factor products employed alone. In those who also need bypassing agents (or FVIII concentrates) for breakthrough bleeds, thromboembolic events and/or thrombotic microangiopathy may occur. By enhancing thrombin generation, prothrombotic mutations co-segregating with FVIII/FIX gene mutations may trigger thrombotic episodes in HA patients carrying acquired thrombogenic factors (e.g. venous catheters). A thorough knowledge of individual needs increasingly contributed to improve comprehensive care and personalize treatments in haemophilia. Integrating genomics, lifestyle and environmental data is expected to be key to: 1) identify which haemophilia patients are less likely to benefit from a given intervention; 2) define optimal dosing and scheduling of bypassing agents (or FVIII) to employ in combination with non-factor products; 3) establish tests to monitor in vivo thrombin generation; 4) improve communication and deliver results to individuals. As individual outcomes will be improved and the risk of adverse events minimized, non-factor products will come into wider use within the haemophilia community, and patients will hopefully have no more risks of breakthrough bleeds. The risks of a normal life for a "former haemophilia patient" is likely to change the treatment landscape and the structure of haemophilia Centers.

Management of bleeding and invasive procedures in haemophilia A patients with inhibitor treated with emicizumab (Hemlibra® ): Proposals from the French network on inherited bleeding disorders (MHEMO), the French Reference Centre on Haemophilia, in collaboration with the French Working Group on Perioperative Haemostasis (GIHP)

INTRODUCTION

Emicizumab (Hemlibra^® ) recently became available and requires an adaptation for managing bleeding, suspected bleeding and emergency or scheduled invasive procedures in haemophilia A patients with inhibitor. This implicates a multidisciplinary approach and redaction of recommendations for care that must be regularly adapted to the available data.

AIM

The following text aims to provide a guide for the management of people with haemophilia A with inhibitor treated with emicizumab in case of bleeding or invasives procedures.

METHODS

The French network on inherited bleeding disorders (MHEMO), the French Reference Centre on Haemophilia (CRH), in collaboration with the French Working Group on Perioperative Haemostasis (GIHP) have been working together to make proposals for the management of these situations.

RESULTS

Haemostatic treatment and other medications should be given stepwise, according to the severity and location of the bleeding or the risk of bleeding of the procedure as well as the haemostatic response obtained at each step in order to ensure an optimal benefit/risk ratio.

CONCLUSION

The lack of data means that it is only possible to issue proposals rather than recommendations.