40K glycoPEGylated, recombinant FVIIa: 3-month, double-blind, randomized trial of safety, pharmacokinetics and preliminary efficacy in hemophilia patients with inhibitors

Site-directed mutagenesis of tissue factor pathway inhibitor-binding exosite D60A on factor VII results in a new factor VII variant with lower coagulant activity

Background

Recombinant factor (F)VIIa (rFVIIa) has been approved by the US Food and Drug Administration for the treatment of hemophilia A and B with inhibitors and congenital FVII deficiency. Moreover, the investigational uses of rFVIIa are becoming of interest since it can be used to treat various clinical bleeding conditions. However, there is evidence showing that rFVIIa is a potent procoagulant agent that potentially leads to an increased risk of thrombotic complications.

Objectives

To design a new rFVII with lower coagulant activity that could potentially be used as an alternative hemostatic agent aiming to minimize the risk of thrombogenicity.

Methods

D60A was introduced into the F7 sequence by polymerase chain reaction-based mutagenesis. Wild type (WT) and D60A were generated in human embryonic kidney 293T cells by stable transfection. FVII coagulant activities were determined by amidolytic cleavage of the FVIIa-specific substrate, 2-step FXa generation, thrombin generation (TG), and clot-based assays.

Results

WT and D60A demonstrated similar FVIIa amidolytic activity. However, D60A showed approximately 50% activity on FX activation and significantly longer lag time in the TG assay than that shown by WT. The clotting time produced by D60A spiked in FVII-deficient plasma was significantly prolonged than that of WT. Additionally, the ex vivo plasma half-lives of WT and D60A were comparable.

Conclusion

D60A demonstrated lower coagulant activities, most likely due to the weakening of FX binding, leading to impaired FX activation and delayed TG and fibrin formation. Considering that a plasma FVII level of 15% to 25% is adequate for normal hemostasis, D60A is a molecule of interest for future development of an rFVII with a lesser extent of thrombogenicity.

Efficacy and safety evaluation of eptacog beta (coagulation factor VIIa [recombinant]-jncw) for the treatment of hemophilia A and B with inhibitors

INTRODUCTION

Bypassing agents (BPAs) are used to treat acute bleeding episodes, manage bleeding during perioperative care, and prophylactically minimize bleed occurrence in persons with hemophilia A or B with inhibitors (PwHABI). However, the effectiveness of BPAs that have been prescribed for the last several decades can be variable, motivating the development of a new recombinant activated factor VII, eptacog beta.

AREAS COVERED

This review covers key eptacog beta findings from phase 1b and phase 3 (PERSEPT) clinical trials, which formed the basis for its regulatory approval to treat PwHABI ages 12 and older. Descriptions of eptacog beta structure and glycosylation profile, mechanism of action, preclinical study results, and cost analyses are also presented.

EXPERT OPINION

PwHABI have had only two options for bleed treatment for the past several decades. With its distinct glycosylation profile, eptacog beta offers a novel therapy aiming to improve upon BPAs currently in use, providing an option with more than one dosing regimen and a rapid response that allows most bleeds to be treated with just one dose. This has become particularly important given the use of subcutaneous medications (e.g., emicizumab) for prophylaxis of bleeding. Clinicians should consider eptacog beta as a BPA for all PwHABI.

Subcutaneous engineered factor VIIa marzeptacog alfa (activated) in hemophilia with inhibitors: Phase 2 trial of pharmacokinetics, pharmacodynamics, efficacy, and safety

BACKGROUND

Marzeptacog alfa (activated) (MarzAA), a novel recombinant activated human factor VII (FVIIa) variant, was developed to provide increased procoagulant activity, subcutaneous (SC) administration, and longer duration of action in people with hemophilia.

OBJECTIVES

To investigate if daily SC administration of MarzAA in subjects with inhibitors can provide effective prophylaxis.

METHODS

This multicenter, open-label phase 2 trial (NCT03407651) enrolled men with severe congenital hemophilia with an inhibitor. All subjects had a baseline annualized bleeding rate (ABR) of ≥12 events/year. Subjects received a single 18 μg/kg intravenous dose of MarzAA to measure 24-hour pharmacokinetics (PK) and pharmacodynamics (PD), single 30 μg/kg SC dose to measure 48-hour PK/PD, then daily SC 30 μg/kg MarzAA for 50 days. If spontaneous bleeding occurred, the dose was sequentially escalated to 60, 90, or 120 μg/kg, with 50 days at the final effective dose without spontaneous bleeding to proceed to a 30-day follow-up. The primary end point was reduction in ABR. Secondary end points were safety, tolerability, and antidrug antibody (ADA) formation.

RESULTS

In the 11 subjects, the mean ABR significantly reduced from 19.8 to 1.6, and the mean proportion of days with bleeding significantly reduced from 12.3% to 0.8%. Of a total of 517 SC doses, six injection site reactions in two subjects were reported. No ADAs were detected. One fatal unrelated serious adverse event occurred: intracerebral hemorrhage due to untreated hypertension.

CONCLUSIONS

The data demonstrated that MarzAA was highly efficacious for prophylactic treatment in patients with inhibitors by significantly decreasing bleed frequency and duration of bleeding episodes.

Mitigation of T-cell dependent immunogenicity by reengineering factor VIIa analogue

Vatreptacog alfa (VA), a recombinant activated human factor VII (rFVIIa) variant with 3 amino acid substitutions, was developed to provide increased procoagulant activity in hemophilia patients with inhibitors to factor VIII or factor IX. In phase 3 clinical trials, changes introduced during the bioengineering of VA resulted in the development of undesired anti-drug antibodies in some patients, leading to the termination of a potentially promising therapeutic protein product. Here, we use preclinical biomarkers associated with clinical immunogenicity to validate our deimmunization strategy applied to this bioengineered rFVIIa analog. The reengineered rFVIIa analog variants retained increased intrinsic thrombin generation activity but did not elicit T-cell responses in peripheral blood mononuclear cells isolated from 50 HLA typed subjects representing the human population. Our algorithm, rational immunogenicity determination, offers a broadly applicable deimmunizing strategy for bioengineered proteins.

The evolution of factor VIIa in the treatment of bleeding in haemophilia with inhibitors

The use of activated factor VII (FVIIa) for the treatment of bleeding events in haemophilia patients with inhibitors was first reported over 30 years ago. Since then clinical trials, registries, case series, real‐world experience and an understanding of its mechanism of action have transformed what was originally a scientific curiosity into one of the major treatments for inhibitor patients, with innovative therapeutic regimens, dose optimization and individualized care now widely practiced. Given current understanding and use, it might be easy to forget the years of clinical research that led up to this point; in this review, we lay out changes based on broad eras of rFVIIa use. These eras cover the original uncertainty associated with dosing, efficacy and safety; the transformation of care ushered in with its widespread use; and the optimization and individualization of patient care and the importance of specialized support provided by haemophilia treatment centres. Today with the introduction of novel prophylactic agents such as emicizumab, we once again find ourselves dealing with the uncertainties of how best to utilize rFVIIa and newer investigational variants such as marzeptacog alfa and eptacog beta; we hope that the experiences of the past three decades will serve as a guide for this new era of care.

Establishment of an HPLC-based method to identify key proteases of proteins in vitro

Given that the biological functions of proteins may decrease or even be lost due to degradation by proteases, it is of great significance to identify potential proteases that degrade protein drugs during systemic circulation. In this work, we describe a method based on high-performance liquid chromatography (HPLC) to identify key proteases that degrade therapeutic proteins in blood, including endopeptidases and exopeptidases. Here, the degradation of proteins was detected by competition with standard substrates of proteases and is shown as the relative residue rate. Four protein drugs were subjected to this method, and the results suggested that growth hormone was degraded by aminopeptidase N and kallikrein-related peptidase 5, pertuzumab was hardly degraded by the proteases, factor VII was degraded by carboxypeptidase B, neprilysin, dipeptidyl peptidase-4 and peptidyl dipeptidase A, and fibrinogen was degraded by carboxypeptidase B and kallikrein-related peptidase 5, findings consistent with the literature. The results were confirmed by microscale thermophoresis; additionally, activity detection in vitro substantiated that the degradation of factor VII decreased its activity. We demonstrate that this method can be used to identify key proteases of proteins with high accuracy, precision and durability.

Safety of recombinant coagulation factors in treating hemophilia

INTRODUCTION

During the last decade, new FVIII/IX concentrates have been developed for the treatment of patients affected by hemophilia A/B. Significant progress has been achieved regarding their half-life, but the old issue of immunogenicity and new concerns about safety need to be addressed.

AREAS COVERED

After the implementation of virucidal methods, both plasma-derived and recombinant clotting factor concentrates achieved a very safe profile. The development of anti-FVIII antibodies is the major adverse event of replacement therapy with both FVIII concentrates. Furthermore, the new extended half-life concentrates, protein fused or pegylated, raised some concerns about their side effects.

EXPERT OPINION

The treatment of hemophilia A with inhibitors by induction of immunotolerance and using by-passing concentrates, improved the quality of life of patients but did not allow them to have a life expectancy like that of patients without inhibitors. The new humanized monoclonal antibody (MAb) ACE910, mimicking FVIII function, seems to be able to reduce the bleedings of hemophilia A patients with inhibitors. The post-marketing surveillance will clarify if the adverse events observed during the phase III clinical trials and compassionate use were due to the association with a Prothrombin activated complex concentrate or to the prothrombotic effect of the drug itself.

The future of bypassing agents for hemophilia with inhibitors in the era of novel agents

Bypassing agents are presently the standard of care for the treatment of bleeding episodes in patients with hemophilia and high-titer inhibitors and are also used for bleed prevention. Only two bypassing agents are available to patients, and these products trace their lineage to the 1970s (activated prothrombin complex concentrates) and the 1980s (recombinant factor VIIa). Given the limited repertoire of available products, clinicians have relied on experience, empirical observation, registry data and individualized care to improve clinical outcomes on a case-by-case basis. Research over the past two decades has culminated in a greatly improved understanding of human coagulation; resulting from this, new products have been developed that offer treatment options and mechanisms of actions that differ from current bypassing agents. The most advanced in clinical development is emicizumab, a bispecific antibody that mimics the function of FVIIIa in the intrinsic Xase complex and is indicated for once-weekly or every-other-week prophylactic dosing in inhibitor patients. Other non-traditional products in clinical development include fitusiran and antibodies directed against tissue factor pathway inhibitor. As non-factor-based therapies become more widely utilized over time, the use of bypassing agents may be expected to decrease; however, bypassing agents will remain essential for the foreseeable future. As such, clinical development of bypassing agents continues, with some products (e.g. eptacog beta) under regulatory review. In this review we examine the optimal use of bypassing agents and their mechanism of action. We also discuss newer products and how these might theoretically be administered in conjunction with traditional bypassing agents.

Bypassing agent prophylaxis in people with hemophilia A or B with inhibitors

BACKGROUND

People with hemophilia A or B with inhibitors are at high risk of bleeding complications. Infusion of bypassing agents, such as recombinant activated FVII (rFVIIa) and plasma-derived activated prothrombin complex concentrate, are suggested as alternative therapies to factor VIII (haemophilia A) or IX (haemophilia B) for individuals who no longer respond to these treatments because they develop inhibitory antibodies. The ultimate goal of treatment is to preserve the individual's joints, otherwise destroyed by recurrent bleeds.

OBJECTIVES

To assess the effects of bypassing agent prophylaxis to prevent bleeding in people with hemophilia A or B and inhibitors.

SEARCH METHODS

We searched for relevant studies from the Cystic Fibrosis and Genetic Disorders Group's Coagulopathies Trials Register, comprising of references identified from comprehensive electronic database searches and handsearches of relevant journals and abstract books of conference proceedings. We also searched trial registries (16 February 2017) and bibliographic references of retrieved studies were reviewed for potential articles to be included in the review.Date of the last search of the Cochrane Cystic Fibrosis and Genetic Disorders Coagulopathies Trials Register: 12 December 2016.

SELECTION CRITERIA

We included randomized and quasi-randomized controlled studies (cross-over or parallel design) evaluating the effect of prophylaxis treatment with bypassing agents compared with on-demand treatment, or studies evaluating the effects of high-dose compared with low-dose prophylaxis in males of any age with hemophilia with inhibitors.

DATA COLLECTION AND ANALYSIS

Two authors independently selected studies and extracted data and assessed the risk of bias according to standard Cochrane criteria. They assessed the quality of the evidence using the GRADE criteria.

MAIN RESULTS

We included four randomized studies (duration 7 to 15 months) involving 116 males. Risk of bias was judged to be high in two studies due to the open-label study design and in one study due to attrition bias.Two studies compared on-demand treatment to prophylaxis with bypassing agents. In one study (34 males) prophylaxis significantly reduced mean overall bleeding rates, MD - 7.27 (95% CI -9.92 to -4.62) (low quality evidence), mean number of overall bleeding events per month, MD -1.10 (95% CI -1.54 to -0.66), mean number of hemarthrosis, MD -6.60 (95% CI -9.32 to -3.88) (low quality evidence) and mean number of joints that had hemarthrosis, MD -0.90 (95% CI -1.36 to -0.44). The meta-analysis did not conclusively demonstrate significant benefit of prophylaxis on health-related quality of life as measured by Haem-A-QoL score, EQ-5D total score and utility score, EQ-5D VAS and SF-36 physical summary and mental summary score (low quality evidence for all health-related quality of life analyses).The remaining two studies compared dose regimens. The results from one study (22 males) did not conclusively demonstrate benefit or harm of high-dose versus low-dose recombinant activated factor VIIa (rFVIIa) as a prophylaxis for overall bleeding rate, MD -0.82 (95% CI -2.27 to 0.63) (moderate quality evidence), target joint bleeding rate, MD -3.20 (95% CI -7.23 to 0.83) (moderate quality evidence) and serious adverse events, RR 9.00 (95% CI, 0.54 to 149.50) (moderate quality evidence).The overall quality of evidence was moderate to low due to imprecision from limited information provided by studies with small sample sizes and incomplete outcome data in one study.

AUTHORS' CONCLUSIONS

The evidence suggests that prophylaxis with bypassing agents may be effective in reducing bleeding in males with hemophilia with inhibitors. However, there is a lack of evidence for the superiority of one agent over the other or for the optimum dosage regimen. Further studies are needed to evaluate the benefits and harms of prophylaxis treatment on health-related quality of life, as well as the effects of dose of bypassing agents on the outcomes.

Safety and efficacy of recombinant activated coagulation factor VII in congenital hemophilia with inhibitors in the home treatment setting: A review of clinical studies and registries

Self-administration of factor and bypassing agents by persons with hemophilia in the home setting is recommended to facilitate earlier intervention after bleeding episodes. The objective of this review was to summarize recombinant activated coagulation factor VII (rFVIIa) safety and efficacy data from clinical trials and patient registries documenting use in the home treatment setting in people with congenital hemophilia with inhibitors (CHwI). A total of 16 studies and registries were identified for inclusion; 14 evaluated on-demand treatment of acute bleeding episodes (865 patients, 9024 bleeding episodes) and 2 evaluated use for secondary prophylaxis (108 patients, 42,861 prophylaxis days). In the on-demand studies, efficacy was consistently high (81%-96%), and thrombotic events were uncommon (n = 3). In the secondary prophylaxis studies, rFVIIa was associated with a 45% to 59% reduction in bleeding episodes and no thrombotic events. These data support the clinical practice of administering rFVIIa in patients in the home treatment setting after initiation under a physician's care.

Hemophilia and inhibitors: current treatment options and potential new therapeutic approaches

The immune response to infused factor concentrates remains a major source of morbidity and mortality in the treatment of patients with hemophilia A and B. This review focuses on current treatment options and novel therapies currently in clinical trials. After a brief review of immune tolerance regimens, the focus of the discussion is on preventing bleeding in patients with hemophilia and inhibitors. Recombinant factor VIIa and activated prothrombin complex concentrates are the mainstays in treating bleeds in patients with inhibitors. Both agents have been shown to reduce bleeding episodes to a similar degree when infused prophylactically; however, individual patients may respond better to one agent over the other at any given time. The international immune tolerance trial revealed that a high-dose factor VIII regimen provided significantly better bleeding protection than the low-dose regimen. Given the high cost of treatment and the potential for a high-dose immune tolerance regimen to prevent bleeding in some patients, we discuss how we treat patients to maximize the prevention of bleeds while minimizing cost. Novel approaches to treatment of these patients are in development. These include agents that mimic factor VIII or augment thrombin generation by bypassing the inhibitor, as well as agents that inhibit the natural anticoagulants.

New and Emerging Agents for the Treatment of Hemophilia: Focus on Extended Half-Life Recombinant Clotting Proteins

Hemophilia A and B are X-linked disorders caused by deficient or defective clotting factor VIII (FVIII) or IX factor (FIX) proteins, and characterized by spontaneous or traumatic bleeding into joints and muscles. Previous use of plasma and plasma-derived clotting factors that lacked appropriate viral inactivation steps in manufacturing led to significant morbidity associated with transfusion-transmitted HIV and hepatitis C virus (HCV). The development of recombinant proteins revolutionized their treatment, and, with no new HIV or HCV infection via clotting proteins for nearly 30 years, greatly improved their lifespan, which now approaches that of the general population, and with the same risks for aging complications. Novel long-acting factor proteins are being licensed to extend FVIII and FIX half-life, thereby reducing infusion frequency and potentially bleed frequency and associated morbidity. Further, novel therapeutics which take advantage of new technologies, including siRNA, monoclonal antibody, and small peptide inhibition technologies, have the potential to simplify treatment and improve outcomes for those with inhibitors.

Recombinant factor VIIa concentrate versus plasma-derived concentrates for treating acute bleeding episodes in people with haemophilia and inhibitors

BACKGROUND

In people with haemophilia, therapeutic clotting agents might be recognised as a foreign protein and induce anti-factor VIII antibodies, known as 'inhibitors'. Drugs insensitive to such antibodies, either recombinant or plasma-derived, are called factor VIII 'by-passing' agents and used for treatment of bleeding in people with inhibitors.

OBJECTIVES

To determine the clinical effectiveness of recombinant factor VIIa concentrate compared to plasma-derived concentrates for treating acute bleeding episodes in people with haemophilia and inhibitors.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Coagulopathies Trials Register which comprises references identified from comprehensive electronic database searches and handsearches of relevant journals and abstract books of conference proceedings.Date of the most recent search of the Group's Coagulopathies Trials Register: 23 September 2015.

SELECTION CRITERIA

Randomised and quasi-randomised controlled clinical trials comparing recombinant factor VIIa concentrate to human plasma-derived concentrates (high-dose human or recombinant factor VIII or factor IX concentrate; non-activated prothrombin complex concentrates; activated prothrombin complex concentrates) in people with haemophilia. Comparisons with animal-derived products were excluded.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed the trials (eligibility and risk of bias) and extracted data. No combined meta-analyses were performed due to the unavailability of outcomes and comparisons common to the included trials.

MAIN RESULTS

A total of 15 trials were identified, two of which (with data for a total of 69 participants) were eligible for analysis. Both trials showed methodological flaws and did not show superiority of one treatment over the other. Both the treatments showed that recombinant factor VIIa and activated prothrombin complex concentrate appeared to have a similar haemostatic effect in both trials, without increasing thromboembolic risk.

AUTHORS' CONCLUSIONS

Based on the separate analysis of the two available randomised trials, recombinant factor VIIa and activated prothrombin complex concentrate were found to be similar in efficacy and safety. However, there is a need for further, well-designed, adequately-powered, randomised controlled trials to assess the relative benefits and risks of using recombinant factor VIIa compared to human plasma-derived concentrates in people with haemophilia with inhibitors. It is advisable that researchers in the field define commonly agreed objective outcome measures in order to enable the pooling of their results, thus increasing the power of comparisons. To date, data could not be combined in a formal meta-analysis. For the same reason reporting concordant and discordant pairs in cross-over trials is recommended.

Half-life extension technologies for haemostatic agents

The use of plasma-derived and recombinant coagulation factors for the treatment of haemophilia A and B is well established and permits patients to live a relatively normal life. In order to improve treatment options, several products are in development, which have a prolonged duration of action, thus enabling less frequent prophylactic dosing and aiming to reduce the burden of treatment. Several innovative approaches are being pursued to extend the half-life of factor VIIa, factor VIII and factor IX, utilising technologies such as Fc fusion, recombinant albumin fusion and addition of polyethyleneglycol (PEG) (PEGylation). These methods prolong the time in the circulation by reducing degradation and elimination. This review summarises the technologies and products in development and their stages of development, and also discusses their pros and cons.

Recombinant factor VIIa analog in the management of hemophilia with inhibitors: results from a multicenter, randomized, controlled trial of vatreptacog alfa

BACKGROUND

Vatreptacog alfa, a recombinant factor VIIa (rFVIIa) analog with three amino acid substitutions and 99% identity to native FVIIa, was developed to improve the treatment of hemophilic patients with inhibitors.

OBJECTIVES

To confirm the safety and assess the efficacy of vatreptacog alfa in treating bleeding episodes in hemophilic patients with inhibitors.

PATIENTS AND METHODS

In this international, multicenter, randomized, double-blind, active-controlled, crossover, confirmatory phase III trial (adept(™) 2) in patients with hemophilia A or B and inhibitors, bleeds were randomized 3 : 2 to treatment with vatreptacog alfa (one to three doses at 80 μg kg(-1) ) or rFVIIa (one to three doses at 90 μg kg(-1) ). Treatment failures after three doses of trial product (TP) were managed according to the local standard of care.

RESULTS

In the 72 patients enrolled, 567 bleeds were treated with TP. Both vatreptacog alfa and rFVIIa gave 93% effective bleeding control at 12 h. Vatreptacog alfa was superior to rFVIIa in secondary efficacy outcomes, including the number of doses used to treat a bleed and sustained bleeding control 24-48 h after the first dose. Eight patients (11%) developed antibodies against vatreptacog alfa, including four with cross-reactivity against rFVIIa and one with an in vitro neutralizing effect to vatreptacog alfa.

CONCLUSIONS

This large randomized controlled trial confirmed the well-established efficacy and safety profile of rFVIIa, and showed that vatreptacog alfa had similar or better efficacy than rFVIIa. However, because of the development of anti-drug antibodies, a positive benefit-risk profile is unlikely to be achieved with vatreptacog alfa.

Predicting dosing advantages of factor VIIa variants with altered tissue factor-dependent and lipid-dependent activities

BACKGROUND

Recombinant factor VIIa (rFVIIa) is an FX-cleaving coagulation enzyme licensed for the treatment of bleeding episodes in hemophiliacs with inhibitory antibodies. Even though the optimal dosing and comparative dose efficacy of rFVIIa remain poorly understood, genetic or chemical modifications of rFVIIa have been proposed, with the goal of achieving faster and longer hemostatic action. No ongoing trial is currently comparing rFVIIa variants with each other.

OBJECTIVES AND METHODS

We used mathematical modeling to compare the pharmacokinetics, dose-response (pharmacodynamics) and dose-effect duration (pharmacokinetics/pharmacodynamics) of rFVIIa variants to predict their optimal doses. The pharmacodynamic (PD) model of FXa generation by FVIIa in complexes with tissue factor (TF) and procoagulant lipids (PLs) was validated against published ex vivo and in vitro thrombin generation (TG) experiments. To compare variants' safety profiles, the highest non-thrombogenic doses were estimated from the clinical evidence reported for the licensed rFVIIa product.

RESULTS

The PD model correctly described the biphasic TF-dependent and PL-dependent dose response observed in TG experiments in vitro. The pharmacokinetic/PD simulations agreed with published ex vivo TG data for rFVIIa and the BAY 86-6150 variant, and explained the similar efficacies of a single dose of 270 μg kg(-1) (as reported in the literature) and repeated doses of 90 μg kg(-1) of unmodified rFVIIa. The duration of the simulated hemostatic effect after a single optimal dose was prolonged for rFVIIa variants with increased TF affinity or extended half-lives, but not for those with modulated PL activity.

CONCLUSIONS

Some modifications of the rFVIIa molecule may not translate into a prolonged hemostatic effect.