A factor VIIIa-mimetic bispecific antibody, Mim8, ameliorates bleeding upon severe vascular challenge in hemophilia A mice

Joint health and pain in the changing hemophilia treatment landscape

INTRODUCTION

Hemophilia is an inherited bleeding disorder. Bleeding, and in particular joint hemorrhage results in chronic arthropathy and disability. Acute and chronic pain are frequent and limit activity and participation and result in decreased health-related quality of life. Remarkable progress has been made in the diagnosis and treatment of hemophilia but bleeding continues to prove recalcitrant to currently available treatments and joint disease remains problematic. Physiotherapy and pain management are mainstays of current multidisciplinary integrated care of people with hemophilia (PWH). The focus of this review is on preservation of joint health in the era of new and innovative therapies.

AREAS COVERED

A search of the PubMed Central was conducted on 1 February 2024 using the MeSH Major Topic terms identified as keywords for the manuscript. This review will highlight what is known and unknown about joint bleeding and arthropathy, including insights on pain as a related complication.

EXPERT OPINION

Recent advances in therapeutic interventions aimed at promoting healthy joints in PWH will be discussed, including both the pharmacological treatment landscape and related strategies to promote joint health.

Recent Advances in Gene Therapy for Hemophilia: Projecting the Perspectives

One of the well-known X-linked genetic disorders is hemophilia, which could be hemophilia A as a result of a mutation in the F8 (factor VIII) gene or hemophilia B as a result of a mutation in the F9 (factor IX) gene, leading to insufficient levels of the proteins essential for blood coagulation cascade. In patients with severe hemophilia, factor VIII or factor IX activities in the blood plasma are considerably low, estimated to be less than 1%. This is responsible for spontaneous or post-traumatic bleeding episodes, or both, leading to disease complications and death. Current treatment of hemophilia relies on the prevention of bleeding, which consists of expensive lifelong replacement infusion therapy of blood plasma clotting factors, their recombinant versions, or therapy with recombinant monoclonal antibodies. Recently emerged gene therapy approaches may be a potential game changer that could reshape the therapeutic outcomes of hemophilia A or B using a one-off vector in vivo delivery and aim to achieve long-term endogenous expression of factor VIII or IX. This review examines both traditional approaches to the treatment of hemophilia and modern methods, primarily focusing on gene therapy, to update knowledge in this area. Recent technological advances and gene therapeutics in the pipeline are critically reviewed and summarized. We consider gene therapy to be the most promising method as it may overcome the problems associated with more traditional treatments, such as the need for constant and expensive infusions and the presence of an immune response to the antibody drugs used to treat hemophilia.

In vivo LNP-CRISPR Approaches for the Treatment of Hemophilia

Hemophilia is a genetic disorder that is caused by mutations in coagulation factor VIII (hemophilia A) or IX (hemophilia B) genes resulting in blood clotting disorders. Despite advances in therapies, such as recombinant proteins and products with extended half-lives, the treatment of hemophilia still faces two major limitations: the short duration of therapeutic effect and production of neutralizing antibodies against clotting factors (inhibitor). To overcome these limitations, new hemophilia treatment strategies have been established such as gene therapy, bispecific antibody, and rebalancing therapy. Although these strategies have shown promising results, it is difficult to achieve a permanent therapeutic effect. Advances in the clustered regularly interspaced short palindromic repeat (CRISPR) technology have allowed sustainable treatment by correcting mutated genes. Since genome editing generates irreversible changes in host genome, safety must be ensured by delivering target organs. Therefore, the delivery tool of the CRISPR system is crucial for safe, accurate, and efficient genome editing. Recently, non-viral vector lipid nanoparticles (LNPs) have emerged as safer tools for delivering CRISPR systems than other viral vectors. Several previous hemophilia pre-clinical studies using LNP-CRISPR showed that sufficient and sustainable therapeutic effects, which means that LNP-CRISPR-mediated genome-editing therapy can be a valid option for the treatment of hemophilia. In this paper, we summarize the latest advancements in the successful treatment of hemophilia and the potential of CRISPR-mediated genome-editing therapy using LNPs.

Exploring nonreplacement therapies' impact on hemophilia and other rare bleeding disorders

The management of hemophilia, von Willebrand disease (VWD), and rare coagulation disorders traditionally relied on replacement therapies, such as factor concentrates, to address clotting factor deficiencies. However, in recent years, the emergence of nonreplacement therapies has shown promise as an adjunctive approach, especially in hemophilia, and also for patients with VWD and rare bleeding disorders. This review article offers an overview of nonreplacement therapies, such as FVIII-mimicking agents and drugs aimed at rebalancing hemostasis by inhibiting natural anticoagulants, particularly in the management of hemophilia. The utilization of nonreplacement therapies in VWD and rare bleeding disorders has recently attracted attention, as evidenced by presentations at the International Society on Thrombosis and Haemostasis 2023 Congress. Nonreplacement therapies provide alternative methods for preventing bleeding episodes and enhancing patients' quality of life, as many of them are administered subcutaneously and allow longer infusion intervals, resulting in improved quality of life and comfort for patients.

FRONTIER1: a partially randomized phase 2 study assessing the safety, pharmacokinetics, and pharmacodynamics of Mim8, a factor VIIIa mimetic

BACKGROUND

Mim8 (denecimig) is a factor VIII (FVIII) mimetic bispecific antibody in development for the treatment of hemophilia. Data from the phase 1 part of FRONTIER1 (EudraCT: 2019-000465-20, NCT04204408, and NN7769-4513) suggested that Mim8 was well tolerated in healthy participants and exhibited pharmacokinetic (PK) properties consistent with dose proportionality.

OBJECTIVES

The partially randomized, phase 2, multiple ascending dose (MAD) part of FRONTIER1 aimed to evaluate the safety, PK, pharmacodynamics (PD), and exploratory efficacy of Mim8 in participants with hemophilia A with or without FVIII inhibitors.

METHODS

The MAD part of FRONTIER1 consisted of 42 participants, assigned to 5 cohorts, with participants in cohorts 3 and 4 randomized 1:1 to dosing weekly or every 4 weeks, respectively. Four of the 42 participants (9.5%) had FVIII inhibitors prior to study enrolment. The primary endpoint was treatment-emergent adverse events (TEAEs). PK and PD were evaluated by Mim8 plasma concentration and thrombin generation, respectively. Exploratory efficacy was assessed via the number of treated bleeds. Safety and PD parameters were also evaluated from an exploratory cohort treated with emicizumab.

RESULTS

Mim8 was well tolerated, with 1 serious TEAE (anxiety-related chest pain) deemed unrelated to Mim8. There was no dose dependency on the number, causality, type, or severity of TEAEs. PK/PD properties supported weekly to monthly dosing approaches, and few participants experienced treated bleeds beyond the lowest dose cohort (1 in cohorts 2 and 3, and 3 in cohort 5).

CONCLUSION

These data support the continued clinical development of Mim8, and FRONTIER1 has proceeded onto an extension phase.

Benefits and risks of non-factor therapies: Redefining haemophilia treatment goals in the era of new technologies

INTRODUCTION

Over the last decades progress in haemophilia treatment has been remarkable and prophylaxis with clotting factor concentrates in haemophilia A and B has been established as the standard of care in individuals with haemophilia and a severe bleeding phenotype. Besides clotting factor products with prolonged half-life non-factor therapies were developed which enable prophylaxis via subcutaneous administration. Factor VIIIa mimetics like emicizumab facilitate the coagulation pathway and are used in routine clinical practice for indivdiduals with haemophilia A. Rebalancing therapeutic agents like fitusiran, concizumab, marstacimab and serpin PC block the anticoagulant pathway and clinical trials using these products in individuals with haemophilia A and B are ongoing.

AIM AND METHODS

A narrative review to asess the benefits and risks of non-factor therapies taking in to account re-defined haemophilia treatment goals.

RESULTS

Prophylaxis for prevention of bleeds using non-factor products by subcutaneous administration is effective and results in reductions of bleeding episodes in individuals with haemophilia A or B with and without inhibitors. The treatment with emicizumab showed tolerable safety both in clinical trials and long-term real-world observations with few thrombotic events. In some clinical trials with rebalancing therapies (fitusiran and concizumab) thrombotic events occurred. Monitoring of the haemostatic function of novel therapies especially with concomitant haemostatic treatment is not yet established.

CONCLUSION

With the advent of novel therapeutic agents including factor concentrates with ultra-long half-life and improved FVIIIa mimetics aimed at raising the bar of protection into the non-hemophilic range redefinition of haemophilia treatment goals is eagerly needed.

Nothing short of a revolution: Novel extended half-life factor VIII replacement products and non-replacement agents reshape the treatment landscape in hemophilia A

Hemophilia A, an X-linked genetic disorder, is characterized by a deficiency or dysfunction of clotting Factor VIII. The treatment landscape has substantially changed by introducing novel extended half-life factor VIII (EHL-FVIII) replacement therapies such as efanesoctocog Alfa and non-factor replacement therapy such as emicizumab. These agents signal a shift from treatments requiring multiple weekly infusions to advanced therapies with long half-lives, offering superior protection against bleeding and improving patient adherence and quality of life. While EHL-FVIII treatment might lead to inhibitor development in some patients, non-factor replacement therapy carries thrombotic risks. Therefore, ongoing research and the generation of robust clinical evidence remain vital to guide the selection of optimal and cost-effective first-line therapies for hemophilia A patients.

Design and engineering of bispecific antibodies: insights and practical considerations

Bispecific antibodies (bsAbs) have attracted significant attention due to their dual binding activity, which permits simultaneous targeting of antigens and synergistic binding effects beyond what can be obtained even with combinations of conventional monospecific antibodies. Despite the tremendous therapeutic potential, the design and construction of bsAbs are often hampered by practical issues arising from the increased structural complexity as compared to conventional monospecific antibodies. The issues are diverse in nature, spanning from decreased biophysical stability from fusion of exogenous antigen-binding domains to antibody chain mispairing leading to formation of antibody-related impurities that are very difficult to remove. The added complexity requires judicious design considerations as well as extensive molecular engineering to ensure formation of high quality bsAbs with the intended mode of action and favorable drug-like qualities. In this review, we highlight and summarize some of the key considerations in design of bsAbs as well as state-of-the-art engineering principles that can be applied in efficient construction of bsAbs with diverse molecular formats.

Thrombin generation on vascular cells in the presence of factor VIII and/or emicizumab

BACKGROUND

The effect of factor VIII (FVIII) or emicizumab on thrombin generation is usually assessed in assays using synthetic phospholipids. Here, we assessed thrombin generation at the surface of human arterial cells (aortic endothelial cells [hAECs] and aortic vascular smooth muscle cells [hVSMCs]).

OBJECTIVES

To explore the capacity of hAECs (resting or stimulated) and hVSMCs to support thrombin generation by FVIII or emicizumab.

METHODS

Primary hVSMCs and hAECs were analyzed for tissue factor (TF)-activity and antigen, phosphatidylserine (PS)-exposure, tissue factor pathway inhibitor (TFPI)-content and thrombomodulin expression. Cells were incubated with FVIII-deficient plasma spiked with FVIII, emicizumab, activated prothrombin complex concentrate (APCC) or combinations thereof.

RESULTS

TF activity and PS-exposure were present on both hVSMCs and hAECs. In contrast, thrombomodulin and TFPI were expressed on hAECs, while virtually lacking on hVSMCs, confirming the procoagulant nature of hVSMCs. Tumor necrosis factor α-mediated stimulation of hAECs increased not only TF antigen, TF activity, and PS-exposure but also TFPI and thrombomodulin expression. As expected, FVIII and emicizumab promoted thrombin generation on nonstimulated hAECs and hVSMCs, with more thrombin being generated on hVSMCs. Unexpectedly, FVIII and emicizumab increased thrombin generation to a lesser extent on stimulated hAECs compared with nonstimulated hAECs. Finally, adding emicizumab to FVIII did not further increase thrombin generation, whereas the addition of emicizumab to APCC resulted in exaggerated thrombin generation.

CONCLUSION

Tumor necrosis factor stimulation of hAECs increases both pro- and anticoagulant activity. Unexpectedly, the increased anticoagulant activity is sufficient to limit both FVIII- and emicizumab-induced thrombin generation. This protective effect disappears when emicizumab is combined with APCC.

Targeting higher factor VIII levels for prophylaxis in haemophilia A: a narrative review

INTRODUCTION

The standard of care in severe haemophilia A is prophylaxis, which has historically aimed for a factor VIII (FVIII) trough level of ≥1%. However, despite prophylactic treatment, people with haemophilia remain at risk of bleeds that have physical and quality of life implications, and that impact everyday life.

AIM

The aim of this review was to evaluate evidence supporting the relationship between targeting higher FVIII activity levels with prophylaxis and improved outcomes in people with haemophilia A.

METHODS

We conducted a narrative review that defined the unmet needs and treatment goals in people with haemophilia A, evaluated evidence to support targeting higher FVIII activity levels, and highlighted therapies that may support higher and sustained FVIII activity levels and improved outcomes for people with haemophilia A.

RESULTS

Despite recent advances in treatment, unmet needs remain, and people with haemophilia continue to experience joint and functional impairment, acute and chronic pain, and poor mental health. All these negatively impact their health-related quality of life. Evidence suggests that FVIII activity levels of up to 50% may be needed to achieve a near-zero joint bleed rate. However, achieving high FVIII activity levels with current standard and extended half-life (EHL) FVIII replacement therapies is associated with a high treatment burden. Innovative treatment options may provide high sustained FVIII activity levels and improved patient outcomes.

CONCLUSION

Evidence suggests that FVIII activity levels in people with haemophilia A should be sustained at higher levels to improve joint and patient outcomes and enable progression towards health equity.

A next generation FVIII mimetic bispecific antibody, Mim8, the impact on non-factor VIII related haemostasis assays

INTRODUCTION AND AIMS

Mim8 is a next generation bispecific antibody developed for the treatment of haemophilia A (HA). Mim8 has an increased potency compared to first generation molecules. The impact on Mim8 on non-FVIII measuring haemostasis assays was assessed in plasma containing Mim8.

METHODS

Congenital severe HA plasma was spiked with increasing concentrations of Mim8 (0-20 μg/mL). 28 routine and specialist haemostasis assays were used to measure activities. These included tests for prothrombin time (PT), fibrinogen, thrombin, D-dimer, anti-Xa, heparin induced thrombocytopenia (HIT), clotting factors II-XII, factor XIII, von Willebrand factor (VWF), thrombophilia and DRVVT.

RESULTS AND CONCLUSIONS

Less than 10 % difference was calculated between plasma without Mim8 and plasma spiked to 15 μg/mL Mim8 in all assays except thrombin time (-10.5%), APTT-based factor IX, XI and XII, Werfen VWF:RCo (10.6%) and Siemens LA1 (-26.4%) and LA2 (-16.9%). At the expected therapeutic steady state levels of Mim8 (5-8 μg/mL), less than 10% difference was calculated for thrombin time and Werfen VWF:RCo. APTT-based assays of FIX, XI and XII are significantly elevated in the presence of Mim8 and should not be performed. A chromogenic FIX assay could be used to accurately measure FIX activity in the presence of Mim8. There was some interference in the DRVVT method we used so local assessment of other DRVVT methods is advised. Differences in all other tests would not be predicted to affect patient management.

Computational design of N-linked glycans for high throughput epitope profiling

Efficient identification of epitopes is crucial for drug discovery and design as it enables the selection of optimal epitopes, expansion of lead antibody diversity, and verification of binding interface. Although high-resolution low throughput methods like x-ray crystallography can determine epitopes or protein-protein interactions accurately, they are time-consuming and can only be applied to a limited number of complexes. To overcome these limitations, we have developed a rapid computational method that incorporates N-linked glycans to mask epitopes or protein interaction surfaces, thereby providing a mapping of these regions. Using human coagulation factor IXa (fIXa) as a model system, we computationally screened 158 positions and expressed 98 variants to test experimentally for epitope mapping. We were able to delineate epitopes rapidly and reliably through the insertion of N-linked glycans that efficiently disrupted binding in a site-selective manner. To validate the efficacy of our method, we conducted ELISA experiments and high-throughput yeast surface display assays. Furthermore, x-ray crystallography was employed to verify the results, thereby recapitulating through the method of N-linked glycans a coarse-grained mapping of the epitope.

Novel therapeutics and emerging technology in haemostasis and thrombosis: highlights from the British society for haemostasis and thrombosis annual meeting

The 2023 annual meeting of the British Society for Haemostasis and Thrombosis (BSHT) was held in Birmingham, United Kingdom. The theme of this year's meeting was novel therapeutics and emerging technology. Here, the exciting research presented at the meeting is discussed.

Sensitive Lateral Flow Immunoassay Based on Specific Peptide and Superior Oxidase Mimics with a Universal Dual-Mode Significant Signal Amplification

Rapid and sensitive antigen detection using a lateral flow immunoassay (LFIA) is crucial for diagnosing infectious diseases due to its simplicity, speed, and user-friendly features. However, it remains a critical issue to explore specific biorecognition elements and powerful signal amplification. In this study, taking SARS-CoV-2 as a proof of concept, a specific peptide, WFLNDSELIML, binding to the SARS-CoV-2 spike (S) antigen was identified by a nonamplified biopanning method, which exhibited high affinity to the target, with a dissociation constant of 9.29 ± 1.55 nM. Molecular docking analysis reveals that this peptide binds to the N-terminal domain of the SARS-CoV-2 S antigen. Then, using this peptide as a capture probe and angiotensin-converting enzyme 2 as a detection probe, a peptide-based lateral flow immunoassay (pLFIA) for the sensitive detection of the SARS-CoV-2 S antigen without any antibody was developed, for which a polydopamine nanosphere (PDA)@MnO2 nanocomposite with excellent oxidase-like activity was used as a colorimetric label, exhibiting dual-mode remarkable signal amplification of natural melanin and on-demand nanozyme catalytic enhancement. The PDA@MnO2-based pLFIA is capable of detecting the SARS-CoV-2 S antigen with a limit of detection of 8.01 pg/mL, which is 18.7 times lower than that of a conventional pLFIA tagged with gold nanoparticles. Additionally, the as-proposed PDA@MnO2-based pLFIA can detect up to 150 transduction units/mL SARS-CoV-2 pseudoviruses spiked in saliva samples. Given the outstanding analytical performance, the proposed PDA@MnO2-based pLFIA may offer a reliable option for the rapid diagnosis of SARS-CoV-2.

Mim8, a novel factor VIIIa mimetic bispecific antibody, shows favorable safety and pharmacokinetics in healthy adults

Background

Mim8 (denecimig) is a novel activated coagulation factor VIII-mimetic bispecific antibody that assembles with activated coagulation FIX and FX on the platelet membrane surface.

Objectives

The FRONTIER1 (NCT04204408, NN7769-4513) single ascending dose and the 4882 pharmacokinetic (PK) studies (NCT05127473, NN7769-4882) examined the safety, tolerability, PK, and pharmacodynamics (PD) of Mim8 in healthy adult males.

Methods

The FRONTIER1 single ascending dose study consisted of 6 cohorts, each with 6 participants who received a single subcutaneous (s.c.) dose of Mim8 and 2 participants who received a placebo. The 4882 PK study had 11 arms, each with 6 participants who received a single s.c. dose of Mim8. The primary endpoint for both studies was treatment-emergent adverse events. Other safety assessments included relative changes in D-dimer, prothrombin fragments 1 and 2, fibrinogen, and platelets. The PK and PD were assessed using Mim8 plasma concentration and activated partial thromboplastin clotting time and thrombin generation, respectively.

Results

Mim8 was well tolerated, and there were no severe treatment-emergent adverse events. The PK properties of Mim8 in both studies were consistent with dose-proportionality. The terminal half-life of Mim8 after a single dose was approximately 1 month, and maximum plasma concentration was reached after 10 days.

Conclusion

The PK and PD profiles suggest that Mim8 is suitable as a long-acting FVIIIa-mimetic bispecific antibody for hemophilia A prophylaxis.

Efficacy/effectiveness and safety of emicizumab prophylaxis of people with hemophilia A: a systematic review and meta-analysis

BACKGROUND

Emicizumab is a monoclonal antibody approved for prophylaxis against bleeds for people with hemophilia A (PwHA). A systematic review was conducted evaluating the efficacy/effectiveness and the safety of emicizumab as prophylaxis for PwHA compared to prophylaxis with factor VIII (FVIII) or bypassing agents (BPA), respectively in patients without and with inhibitors.

RESEARCH DESIGN AND METHODS

Database-directed search strategies were performed in Aug/26/2022 and updated in Mar/16/2023. Studies evaluating the prophylaxis with emicizumab versus prophylaxis with FVIII or BPA in PwHA without or with inhibitors, respectively, were selected by two independent reviewers. Data were extracted by two independent reviewers. Annualized bleeding rates for total treated bleeding events (ABR-all) were evaluated by meta-analysis. The quality of studies and certainty of evidence were assessed.

RESULTS

A total of 11 studies were included. The standard mean differences for ABR-all were -0.6 (95%CI -1.0 to -0.2, p-value = 0.0002), among PwHA without inhibitors, and -1.7 (95%CI -2.4 to -0.9, p-value <0.00001), among PwHA with inhibitors. However, there was moderate heterogeneity in both meta-analyses. The most frequent adverse event was injection site reaction.

CONCLUSIONS

Emicizumab prophylaxis was superior in reducing the ABR-all when compared with prophylaxis with FVIII or BPA.

A graph-based machine learning framework identifies critical properties of FVIII that lead to hemophilia A

Introduction: Blood coagulation is an essential process to cease bleeding in humans and other species. This mechanism is characterized by a molecular cascade of more than a dozen components activated after an injury to a blood vessel. In this process, the coagulation factor VIII (FVIII) is a master regulator, enhancing the activity of other components by thousands of times. In this sense, it is unsurprising that even single amino acid substitutions result in hemophilia A (HA)-a disease marked by uncontrolled bleeding and that leaves patients at permanent risk of hemorrhagic complications. Methods: Despite recent advances in the diagnosis and treatment of HA, the precise role of each residue of the FVIII protein remains unclear. In this study, we developed a graph-based machine learning framework that explores in detail the network formed by the residues of the FVIII protein, where each residue is a node, and two nodes are connected if they are in close proximity on the FVIII 3D structure. Results: Using this system, we identified the properties that lead to severe and mild forms of the disease. Finally, in an effort to advance the development of novel recombinant therapeutic FVIII proteins, we adapted our framework to predict the activity and expression of more than 300 in vitro alanine mutations, once more observing a close agreement between the in silico and the in vitro results. Discussion: Together, the results derived from this study demonstrate how graph-based classifiers can leverage the diagnostic and treatment of a rare disease.

In vitro effects of combining Mim8 with factor VIII, FVIIa, and activated prothrombin complex concentrates in thrombin generation assays

BACKGROUND

Mim8 is a novel antifactor IXa/antifactor X bispecific antibody in clinical development for prophylactic treatment of hemophilia A with and without inhibitors. Patients treated with Mim8 may need supplementary bleed treatment under certain conditions such as surgery or major trauma.

OBJECTIVES

This study aimed to better understand the response of Mim8 in thrombin generation assays (TGAs) alone or in combination with other hemostatic proteins.

METHODS

We used TGAs with different activators (tissue factor (TF) and activated factor XI) to better understand the similarities and differences between the mode of action of Mim8 and factor VIII (FVIII). Following this, we investigated the effects of mixing Mim8 with the main bleed treatment options for persons with hemophilia A with or without inhibitors: FVIII, activated factor VII (FVIIa), and activated prothrombin complex concentrates (aPCC).

RESULTS

The results indicated that for patients without inhibitors, Mim8 does not interfere with FVIII's mode of action. For patients with inhibitors, Mim8 mixed with aPCC results in a strong synergistic effect causing thrombin generation far exceeding the normal levels. Contrary to this, mixing Mim8 with FVIIa results in a more controlled additive effect, visible only when using TF as a trigger, which does not exceed the normal level of thrombin generation.

CONCLUSION

These findings support the use of approved clinical doses of FVIIa for bleed treatment of patients with FVIII inhibitors treated with Mim8. Additionally, the findings suggest that concomitant use of FVIII and Mim8 is safe for managing breakthrough bleeds.

New directions to develop therapies for people with hemophilia

INTRODUCTION

The past few decades have seen a tremendous advancement in the management of hemophilia. Whether it is improved methods to attenuate critical viruses, recombinant bioengineering with decreased immunogenicity, extended half-life replacement therapies to mitigate the burden of repeated infusion treatments, novel nonreplacement products to avoid the drawback of inhibitor development with its attractive subcutaneous administration and then the introduction of gene therapy, the management has trodden a long way.

AREAS COVERED

This expert review describes the progress in the treatment of hemophilia over the years. We discuss, in detail, the past and current therapies, their benefits, drawbacks, along with relevant studies leading to approval, efficacy and safety profile, ongoing trials, and future prospects.

EXPERT OPINION

The technological advances in the treatment of hemophilia with convenient modes of administration and innovative modalities offer a chance for a normal existence of the patients living with this disease. However, it is imperative for clinicians to be aware of the potential adverse effects and the need for further studies to establish causality or chance association of these events with novel agents. Thus, it is crucial for clinicians to engage patients and their families in informed decision-making and tailor individual concerns and necessities.

The effect of a next generation factor VIII mimetic bispecific antibody (Mim8) on assays of factor VIII activity and thrombin generation

BACKGROUND

Mim8 is a next generation bispecific antibody developed for the prophylactic treatment of hemophilia A. The sensitivity of activated plasma thromboplastin time (APTT), assays measuring factor VIII activity (FVIII:C) and thrombin generation to plasma containing Mim8 was assessed.

METHODS

Congenital severe hemophilia A plasma was spiked with Mim8 at 0 μg/mL to 20 μg/mL. APTT was measured with 4 reagents, one-stage FVIII with 9 reagents, and chromogenic FVIII with 6 assays. Thrombin generation was assessed in a low tissue factor system.

RESULTS

At 1-μg/mL Mim8, the APTT was shortened to within normal limits and one-stage FVIII:C was >1.00 IU/mL with all APTT reagents. Modified one-stage assays calibrated with Mim8 reference material calibrated recovered within 20% of the target Mim8 concentration with most APTT reagents. Factor VIII:C of bovine only chromogenic assays was <0.04 IU/mL at all Mim8 concentrations. Factor VIII:C of human only chromogenic assay was >4.00 IU/mL at 20-μg/mL Mim8. Factor VIII:C of hybrid bovine FX, human FIXa chromogenic assays ranged from 0.076 to >3.00 IU/mL at 20-μg/mL Mim8. Normal thrombin generation was restored at 5-μg/mL Mim8.

CONCLUSIONS

APTT-based assays are sensitive to Mim8 and should not be performed in the presence of the drug. Chromogenic assays containing human proteins or hybrid human/bovine proteins demonstrated variable sensitivity to Mim8. Bovine only chromogenic assays were largely insensitive to the presence of Mim8. Thrombin generation normalized at increased Mim8 concentrations. Modified one-stage and chromogenic assays could be used to quantify the Mim8 concentration in plasma.

Hemophilia a patients with inhibitors: Mechanistic insights and novel therapeutic implications

The development of coagulation factor VIII (FVIII) inhibitory antibodies is a serious complication in hemophilia A (HA) patients after FVIII replacement therapy. Inhibitors render regular prophylaxis ineffective and increase the risk of morbidity and mortality. Immune tolerance induction (ITI) regimens have become the only clinically proven therapy for eradicating these inhibitors. However, this is a lengthy and costly strategy. For HA patients with high titer inhibitors, bypassing or new hemostatic agents must be used in clinical prophylaxis due to the ineffective ITI regimens. Since multiple genetic and environmental factors are involved in the pathogenesis of inhibitor generation, understanding the mechanisms by which inhibitors develop could help identify critical targets that can be exploited to prevent or eradicate inhibitors. In this review, we provide a comprehensive overview of the recent advances related to mechanistic insights into anti-FVIII antibody development and discuss novel therapeutic approaches for HA patients with inhibitors.

Early stage clinical trials for the treatment of hemophilia A

INTRODUCTION

Hemophilia A is a severe bleeding disorder affecting about 1 in 5,000 males. The gold standard for prophylaxis and treatment of acute bleeding has been factor (F) VIII concentrate. A multitude of treatment modalities are now available and under clinical investigation.

AREAS COVERED

This review discusses ongoing/recently completed early-phase clinical trials registered on ClinicalTrials.gov in patients with hemophilia A through April 2022. These new pipeline therapies are focused on addressing the safety and efficacy of new factor-related products, non-factor related products, and gene therapy options for hemophilia.

EXPERT OPINION

Current standard of care effectively prevents and treats acute bleeding and has significantly improved the quality of life in hemophilia. The biggest challenges in the improvement of care are treatment-related burden and the burden of cost in developing countries. New drugs under development are likely to enter practice by the end of this decade and address many of the unmet needs particularly of those with severe disease. Data is limited in unique populations (e.g. congenital/inherited FVIII inhibitors, non-severe hemophilia A, women/girls with hemophilia and children) which are important areas for future research; additional clinical trials and long-term outcome data are necessary prior to incorporating these new therapies in our treatment arsenal.

Immunotherapeutic progress and application of bispecific antibody in cancer

Bispecific antibodies (bsAbs) are artificial antibodies with two distinct antigen-binding sites that can bind to different antigens or different epitopes on the same antigen. Based on a variety of technology platforms currently developed, bsAbs can exhibit different formats and mechanisms of action. The upgrading of antibody technology has promoted the development of bsAbs, which has been effectively used in the treatment of tumors. So far, 7 bsAbs have been approved for marketing in the world, and more than 200 bsAbs are in clinical and preclinical research stages. Here, we summarize the development process of bsAbs, application in tumor treatment and look forward to the challenges in future development.

Minor structural changes, major functional impacts: posttranslational modifications and drug targets

Posttranslational modifications (PTMs) are essential mechanisms that provide chemical diversity to proteins. The additional functional and structural elements can be introduced to exceed the primary amino acid composition. PTMs impact key biological and physiological processes including cell signaling, metabolism, protein degradation and influences interactions with other macromolecules. However, characterization of the structural and functional signatures of modified proteins has been historically limited. Since defects in PTMs are linked to numerous disorders and diseases, PTMs and their modifying enzymes are considered as potential drug targets. This has fueled new initiatives to determine how PTMs affect protein structure and function. In this review, I summarize some of the major, well-studied protein PTMs and related drug targets. Since PTMs are widely used for therapeutic targets or disease markers, highlighting structural changes after PTM provides new frontiers in understanding the detailed mechanism and related drug developments.

Patient blood management and patient safety

PURPOSE OF REVIEW

The particular fields within patient blood management (PBM) and patient safety reviewed here include novel insights into bleeding therapy, autologous cell salvage, and perioperative anemia therapy.

RECENT FINDING

World Health Organization has published that implementation of PBM is important but has not yet been performed in all hospitals. Two antibodies that mimic the function of FVIII, Emicizumab, and Mim8 have been developed. Tranexamic acid (TXA) has been investigated further in patients with hip surgery and shows reduction of bleeding. Thrombocytopenia in patients undergoing cardiac surgery is a particular concern that has been investigated in another trial. The use of autologous cell salvage was updated in form of a review and meta-analysis. And last but not least, intravenous iron in preoperative anemia therapy can reduce the number of transfusions, but especially iron carboxymaltose can cause hypophosphatemia.

SUMMARY

PBM should be further implemented in more hospitals. Emicizumab and Mim8 are indicated in acquired hemophilia or hemophilia A with inhibitors. TXA was confirmed to reduce bleeding. Autologous cell salvage is state of the art to reduce transfusion requirements in major cardiac and noncardiac surgery. Serum phosphate concentrations should be monitored after administration of intravenous iron compounds.

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.

Structural insights into blood coagulation factor VIII: Procoagulant complexes, membrane binding, and antibody inhibition

Advances in structural studies of blood coagulation factor VIII (FVIII) have provided unique insight into FVIII biochemistry. Atomic detail models of the B domain-deleted FVIII structure alone and in complex with its circulatory partner, von Willebrand factor (VWF), provide a structure-based rationale for hemophilia A-associated mutations which impair FVIII stability and increase FVIII clearance rates. In this review, we discuss the findings from these studies and their implications toward the design of a recombinant FVIII with improved circulatory half-life. Additionally, we highlight recent structural studies of FVIII bound to inhibitory antibodies that have refined our understanding of FVIII binding to activated platelet membranes and formation of the intrinsic tenase complex. The combination of bioengineering and structural efforts to understand FVIII biochemistry will improve therapeutics for treating hemophilia A, either through FVIII replacement therapeutics, immune tolerance induction, or gene therapy approaches.

A novel next-generation FVIIIa mimetic, Mim8, has a favorable safety profile and displays potent pharmacodynamic effects: Results from safety studies in cynomolgus monkeys

BACKGROUND

Mim8 is a novel, next-generation factor VIIIa mimetic in development for subcutaneous prophylactic treatment of patients with hemophilia A with and without inhibitors. In vitro and in vivo models indicate that Mim8 has a distinct hemostatic potential.

OBJECTIVES

To test the nonclinical safety and pharmacodynamics of Mim8.

METHODS

The Mim8 nonclinical safety program in cynomolgus monkeys consisted of three studies of 4-26 weeks in duration with Mim8 doses ranging from 0.3-60 mg/kg/week intravenously or subcutaneously. After sacrifice, macroscopic and microscopic pathological examinations were performed.

RESULTS

Mim8 was well tolerated with no noteworthy clinical observations. No signs of excessive coagulation or pathological macroscopic or microscopic findings were observed at doses 0.3-3 mg/kg/week subcutaneous. Thrombosis-related findings were detected during histopathological examination in a small proportion of animals (16%) receiving doses ranging 6-20 mg/kg/week. Dose-dependent increases in factor X (FX) and factor IX (FIX) concentrations were observed. Shortening of activated partial thromboplastin time (APTT) and increased thrombin generation under ex vivo hemophilia A-like conditions were observed at all Mim8 dose levels.

CONCLUSIONS

Thrombosis-related findings observed at doses above 6 mg/kg/week Mim8 may have been exaggerated pharmacological reactions to a procoagulant compound in normocoagulant animals. Increases in FX and FIX concentrations could be because of a half-life prolongation due to binding to Mim8, but were limited at clinically relevant exposure levels. Subcutaneous administration of up to 3 mg/kg/week (several fold greater than expected clinical exposure) for 26 weeks resulted in relevant pharmacodynamic effects, observed in thrombin generation and APTT, with no signs of thrombi or excessive coagulation activation.

Therapeutic and technological advancements in haemophilia care: Quantum leaps forward

INTRODUCTION

Recent technological innovations in haemophilia have advanced at an astounding pace, including gene therapy programmes and bioengineered molecules for prophylaxis, products that reduce treatment burden through half-life extension, unique mechanisms of action, and subcutaneous administration. Additional technological advancements have emerged that are anticipated to further transform haemophilia care.

AIM

Review new and emerging haemophilia therapies, including replacement and bypassing products, digital applications, utilisation of big data, and personalised medicine.

METHODS

Data were obtained from peer-reviewed presentations/publications, and ongoing studies in haemophilia, ultrasonography, and artificial intelligence (AI).

RESULTS

Available treatments include new recombinant factors VIII (FVIII) and IX (FIX), extended half-life FVIII/IX products, a new FVIIa product for inhibitor patients, and a FVIIIa-mimetic. Several novel therapeutics are in clinical trials, including FVIIIa mimetics and inhibitors of naturally-occurring anticoagulants. Ongoing gene therapy trials suggest that a single vector infusion using an optimised construct can produce factor activity that reduces bleeding to near zero for years. Today, persons with haemophilia (PwH) approach a lifespan comparable to that of the general population, presenting treatment challenges for age-related co-morbidities. Technological innovations have broadened beyond therapeutics to include large database analyses utilising remote data collection with handheld devices, and to tailor AI applications. Current development efforts include patient-performed ultrasonography, algorithms for scan interpretation, and point-of-care haemostatic testing devices.

CONCLUSIONS

We have entered a golden age for haemophilia treatment and care with wide-ranging advancements targeting improved quality of life (QoL). Future-focused efforts by clinical and patient communities may provide equitable access and care for people impacted by haemophilia worldwide.

Impact of novel hemophilia therapies around the world

Hemophilia A and B are hereditary bleeding disorders, characterized by factor VIII or IX deficiencies, respectively. For many decades, prophylaxis with coagulation factor concentrates (replacement therapy) was the standard‐of‐care approach in hemophilia. Since the 1950s, when prophylaxis started, factor concentrates have been improved with virus inactivation and molecule modification to extend its half‐life. The past years have brought an intense revolution in hemophilia care, with the development of nonfactor therapy and gene therapy. Emicizumab is the first and only nonreplacement agent to be licensed for prophylaxis in people with hemophilia A, and real‐world data show similar efficacy and safety from the pivotal studies. Other nonreplacement agents and gene therapy have ongoing studies with promising results. Innovative approaches, like subcutaneous factor VIII and lipid nanoparticles, are in the preclinical phase. These novel agents, such as extended half‐life concentrates and emicizumab, have been available in resource‐constrained countries through the constant efforts of the World Federation of Haemophilia Humanitarian Aid Program. Despite the wide range of new approaches and therapies, the main challenge remains the same: to guarantee treatment for all. In this article, we discuss the evolution of hemophilia care, global access to hemophilia treatment, and the current and future strategies that are now under development. Finally, we summarize relevant new data on this topic presented at the ISTH 2021 virtual congress.

Managing Severe Hemophilia A in Children: Pharmacotherapeutic Options

Hemophilia A is the most common severe inherited bleeding disorder in males. Initial treatment strategies focused on the use of factor concentrates to prevent joint bleeding and the development of long-term crippling arthropathy. The current standard of care has evolved from regular replacement of factor VIII concentrates which has significantly improved the quality of life for those with severe disease to include and consider novel therapies that augment or bypass the hemostatic pathway (ie, emicizumab, Mim8). Other pipeline therapies that suppress specific natural anticoagulant pathways (ie, antithrombin, TFPI) to reestablish hemostatic balance are under Phase 3 trial investigation. These novel therapeutics have allowed providers more variety in dosing regimens and ease of administration while also maintaining effective bleeding prevention. The possibility of "curative" gene therapy is under exploration, with ongoing clinical trials in adult males.