Long-acting recombinant fusion protein linking coagulation factor IX with albumin (rIX-FP) in children. Results of a phase 3 trial

Trenonacog alfa safety, efficacy, and pharmacokinetics in previously treated pediatric hemophilia B

Background

Trenonacog alfa is a recombinant factor IX approved for adolescents and adults with hemophilia B.

Objectives

The aim of this study was to assess the pharmacokinetics (PK), efficacy as prophylaxis, control of bleeding episodes, and safety of trenonacog alfa in previously treated participants aged <12 years with severe or moderately severe hemophilia B and no current or history of inhibitors.

Methods

The study had 3 phases: (1) PK evaluation after a single infusion of 75 ± 5 IU/kg, (2) treatment phase in which participants received trenonacog alfa prophylaxis 35 to 75 IU/kg for 50 exposure days, and (3) a continuation phase in which prophylaxis could be administered for ≥50 additional exposure days.

Results

The PK of trenonacog alfa was comparable between adolescents and adults except for higher clearance, shorter mean residence time and elimination half-life, and lower incremental recovery. Prophylaxis resulted in a median annualized bleeding rate of 0.86 (mean = 2.34) for the combined treatment and continuation phases; 33.3% of participants had zero bleeds; and 83.7% of bleeds treated resolved with 1 or 2 infusions. One adverse event was possibly related to trenonacog alfa, a nonserious hypersensitivity reaction leading to early study termination. The efficacy and safety of trenonacog alfa for prophylaxis and bleeding treatment in previously treated pediatric participants were consistent with those reported for adults and adolescents. There appeared to be no clinically important differences between the results for participants aged <6 years and those aged 6 to <12 years.

Conclusion

Trenonacog alfa is a suitable option for the management of pediatric persons with hemophilia B.

Intracranial hemorrhage in an infant leads to the diagnosis and treatment of severe hemophilia B: a case report

BACKGROUND

Hemophilia B is a rare bleeding disorder in males, characterized by a deficiency in coagulation factor IX (FIX). Replacement of FIX with a recombinant FIX (rFIX) fusion protein, to sustain therapeutic plasma levels, is recommended as both treatment and prophylaxis to prevent bleeding episodes, particularly intracranial hemorrhage (ICH).

CASE PRESENTATION

This case report outlines the management of ICH in a 7-month-old infant with severe hemophilia B, following an accidental trauma-related event, resulting in a thin compound fracture of the left occiput. FIX levels were extremely low (˂1.0%) and large deletions of the coagulation F9 gene (including exons 1-6) were identified. Intensive treatment with a rFIX fusion protein conjugated to the immunoglobulin Fc fragment (rFIXFc) continued for 18 days before hospital discharge. A continuous regimen of weekly rFIXFc infusions was implemented. Thirty days after initiating rFIXFc therapy, neutralizing antibodies or FIX inhibitors (common in patients with large F9 gene deletions) were observed, causing a diffuse skin rash. Such allergic reactions typically indicate progression to potentially serious nephrotic syndrome. A unique immunotolerance regimen of oral oxatomide and intravenous hydrocortisone was started to proactively prevent allergic reactions in this patient during rFIXFc prophylaxis. Even though low titers of the inhibitor (0.6-1.0 Bethesda units) were observed occasionally during subsequent follow-up, there were no signs of further allergies or development of nephrotic syndrome.

CONCLUSION

This is an uncommon case in which rFIXFc was continued despite the appearance of an allergic reaction and the development of FIX inhibitors. Subsequent allergic reactions were prevented with a combination of oral oxatomide and intravenous hydrocortisone given prior to prophylactic rFIXFc. Further studies are recommended to determine the usefulness of this combination with rFIX therapy.

Factor IX stimulants in preclinical and early phase trials for hemophilia B treatment

INTRODUCTION

Hemophilia B is a X-linked rare inherited bleeding disorder characterized by coagulation factor IX (FIX) deficiency. Therapy for hemophilia B is aimed at replacing the FIX deficiency by means of several plasma-derived or recombinant FIX products. The recent availability of recombinant FIX concentrates with a prolonged FIX half-life represented a great technological advance, permitting more spaced drug infusions and reducing treatment burden among hemophilia B patients.

AREAS COVERED

This review summarizes the main preclinical and phase 1/2 studies investigating the innovative hemostatic products for hemophilia B replacement therapy.

EXPERT OPINION

The significant recent technological advantages in the treatment of hemophilia B has led to the development of innovative FIX products aimed at further extending FIX half-life and using increasingly effective and convenient modes of administration. These novel hemostatic agents, currently in the preclinical or early clinical phase of development, carry the potential of improving patients' health status and quality of life. Continuous research is anyway needed to offer such patients a concrete chance of conducting a normal existence, like to non-affected age-matched individuals.

Nonacog beta pegol prophylaxis in children with hemophilia B: safety, efficacy, and neurodevelopmental outcomes for up to 8 years

Background

Nonacog beta pegol (N9-GP) is an extended half-life PEGylated factor (F)IX product with established efficacy and short-term safety in persons with hemophilia B (HB). Long-term safety has been evaluated for polyethylene glycol exposure but not N9-GP.

Objectives

To assess safety, neurodevelopmental, and efficacy outcomes of children with HB receiving N9-GP prophylaxis across 2 open-label, single-arm, phase 3 studies: paradigm5 (previously treated patients [PTPs]) and paradigm6 (previously untreated patients [PUPs]) in this interim analysis.

Methods

PTPs (aged ≤12 years) and PUPs (aged <6 years) with severe/moderate (≤2% FIX level) HB were recruited to N9-GP prophylaxis (40 IU/kg once weekly) in paradigm5 and paradigm6, respectively. Safety assessments included FIX inhibitor incidence, adverse events, neurocognitive and neurologic outcomes, polyethylene glycol concentration in plasma, and medical events of special interest. Efficacy endpoints included bleeds, N9-GP hemostatic effect, and FIX consumption.

Results

Overall, 25 patients in paradigm5 and 50 patients in paradigm6 received N9-GP and were followed for up to 8 and 6 years, respectively. No inhibitory antibodies were reported in PTPs; 4 of the 50 PUPs developed inhibitors. Extensive evaluation revealed no neurocognitive or neurologic concerns with N9-GP use in children during the study period. Across both studies, few adverse events were reported as possibly related to N9-GP. High hemostatic response rate, high treatment adherence, low annualized bleeding rates, and no new target joints were reported.

Conclusion

These data provide the longest follow-up for an extended half-life FIX and confirm the long-term efficacy of N9-GP prophylaxis in children with HB with no observed neurocognitive or neurologic safety concerns.

Switching and increasing prophylaxis regimen with a genetically recombinant fusion of coagulation factor IX and albumin in haemophilia B: a case report

PURPOSE OF REVIEW

We present a case of a boy diagnosed in 2007 with severe haemophilia B [factor IX (FIX) concentration < 1%] at age of 9 months. He was initially treated with recombinant FIX concentrates, but changes in regimens were frequent due to spontaneous hemarthros. In 2013, he entered a phase III trial (NCT01662531) and received rIX-FP, IDELVION at 50 IU/kg once a week. Although the boy was safely maintained with this regimen (2015-2017), the number of hemarthros increased after he started to play football. Thus, rIX-FP regimen was modified (40 IU/kg twice/week) to optimize therapy. This modification was efficient on maintaining patient's thought levels (33%), helped during his fully incorporation at school and social life, and significantly improved synovial hypertrophy. In the last year, the boy has not suffered any bleeding episode and his joint situation improved significantly, which allowed reducing doses to weekly recommended doses.

RECENT FINDINGS

FIX replacement therapies with intravenous plasma-derived FIX (pdFIX) or standard half-life recombinant FIX (rFIX) concentrates are hampered by the relatively short terminal elimination half-life (t1/2) of these substances (around 17-34 h), resulting in the need for frequent infusions (e.g. once every 3 or 4 days) to maintain protective FIX levels. In the past years, the first genetically recombinant fusion of rFIX with another protein - a recombinant human albumin - was developed (albutrepenonacog-alfa or rIX-FP; IDELVION) as a strategy to extend the t1/2 of rFIX-FP (around 95 h).

SUMMARY

We provide information about the difficult management of a patient with a major bleeding haemorrhagic phenotype, which caused serious limitations in the patient's daily life, impacting his quality of life at his young age, and how the switch to IDELVION allowed the situation to improve considerably.

Extended half-life factor IX prophylaxis up to every 21 days in hemophilia B: a longitudinal analysis of the efficacy and safety in selected adult patients

Background

Extended half-life factor IX (FIX) products have revolutionized prophylactic treatment for patients with hemophilia B as patients maintain protective FIX levels with minimal occurrence of spontaneous bleeding. rIX-FP is an extended half-life FIX product that allows prolonged dosing intervals.

Objectives

To assess individualized and prolonged prophylactic dosing interval up to 21 days in adult patients (≥18 years) with hemophilia B in the rIX-FP clinical trial program.

Methods

Patients who were included in the PROLONG-9FP phase III study or who received rIX-FP during surgery could continue into an extension study for long-term assessment. Patients began 7-day prophylaxis with rIX-FP, and after 6 months, they could extend dosing intervals to every 14 days. In the extension study, adult patients could switch to a 21-day regimen if well-controlled on a 14-day regimen.

Results

Eleven patients transitioned from a 7-day prophylaxis regimen to a 14-day regimen and finally to a 21-day regimen, 5 of whom were treated on demand at enrollment. Patients who switched to the 21-day regimen had a median annualized spontaneous bleeding rate of 0.0 across all regimens. The median observed FIX activity remained >5 IU/dL until day 21 after a single 100-IU/kg dose of rIX-FP. After 6 months on the 21-day regimen, 2 patients switched back to a 14-day regimen. No inhibitors, anaphylactic reactions, or thromboembolic events occurred.

Conclusion

Patients who are well controlled on a once-weekly regimen might extend their treatment interval to 14 days, and in adult patients, further extension to up to 21 days (100 IU/kg) may be considered.

Clinical experience of switching patients with severe hemophilia to rVIII-SingleChain or rIX-FP

OBJECTIVE

Prophylaxis treatment is the current standard of care for patients with severe hemophilia. Factor concentrates with improved pharmacokinetics have offered more options for individualizing treatment. The treatment focus may be on increased protection, aiming for higher trough factor levels or longer dosing intervals to reduce the burden of hemophilia. Both aspects can have long-term effects on joint health. Products, such as rVIII‑SingleChain and rIX-FP have been developed to reduce the treatment burden for patients with hemophilia and optimize prophylactic efficacy. The objective of this report is to provide a summary of the clinical experience of different Hemophilia Treatment Centers in managing the switch to rVIII-SingleChain or rIX-FP in patients with hemophilia.

METHODS

This report summarizes a selection of patient cases presented at the 3rd Alliance for Coagulation Academy Meeting in October 2020. The cases from the participating centers provide examples of the clinical experience in managing patients' switch to rVIII-SingleChain and rIX‑FP, including which types of patients are suitable for switching, and practical steps in managing a switch.

RESULTS

It is important to take into consideration the physical and social fulfillment of the patient when deciding to switch to rVIII-SingleChain or rIX-FP. The physician plays an important role in the motivation of patients as they understand not only the patient's needs but the potential benefits of the new treatment.

CONCLUSION

The selected patient cases reported here demonstrate that patients may wish to switch factor products for a variety of reasons; therefore, it is critical to understand why patients switch and what they expect from switching.

Real-World Use of Albutrepenonacog Alfa, A Recombinant Coagulation Factor IX Albumin Fusion Protein, for Personalized Prophylaxis in Japanese Individuals With Hemophilia B: A Case Series

Currently, the mainstay of disease management for hemophilia B, a hemorrhagic disease caused by a congenital deficiency or molecular abnormalities of blood coagulation factor IX (FIX), is prophylaxis using FIX concentrate. On-demand injections of FIX concentrate may also be required, even during prophylaxis, when a patient with hemophilia B is bleeding. Albutrepenonacog alfa (rFIX-FP) is a human albumin fusion gene recombinant FIX, which is administered once every seven, 14, or 21 days, depending on patient preferences and symptoms. Studies have demonstrated its efficacy and safety in a range of patients; however, to date, reports of real-world experiences of the use of rFIX-FP in Japan are limited. We present a case series of three Japanese individuals with moderately severe (FIX activity 1 to <2%) or severe (FIX activity <1%) hemophilia B who benefited from prophylaxis using rFIX-FP in our clinical practice setting. We highlighted the good effectiveness of rFIX-FP in a patient with moderately severe hemophilia B who required prophylaxis due to joint bleeding, which was causing deterioration of his left ankle joint, as well as in a patient with severe hemophilia B and atherothrombotic cerebral infarction, whose trough level had to be ≥5% for concomitant use of an antiplatelet drug, and in a patient with severe hemophilia B who was working in nursing care, which involved heavy labor and night shifts, and who had previously been treated with on-demand FIX concentrate. In all three cases, rFIX-FP improved disease symptoms, and the patients were able to maintain steady states of therapy due to the treatment characteristics of rFIX-FP, which stabilizes FIX at high trough levels.

Long-term prophylaxis: what are our options and how to define success?

Currently, we are at an enviable place in hemophilia treatment. Although full prophylaxis with standard half-life recombinant or plasma-derived factor concentrates has been definitively shown to be inadequate for full protection against bleeding and arthropathy, a number of novel therapies with improved hemostatic enhancement are clinically available or in promising clinical trials. In order to compare outcomes among a number of very efficacious therapies, it is necessary to have sensitive tools employed in long-term follow-up for several years for participants with no or minimal joint disease. The tool kit must be comprehensive, with outcomes of bleeding, factor level restoration or hemostatic capacity, joint structure, joint function, pain, quality of life, and patient satisfaction. This article reviews the history of prophylaxis, the promise of emerging therapies, and the sensitive tools used to assess long-term efficacy for joint structure and function.

IDELVION: A Comprehensive Review of Clinical Trial and Real-World Data

Hemophilia B is a bleeding disorder caused by a deficiency of coagulation factor IX (FIX). Treatment with FIX replacement products can increase FIX activity levels to minimize or prevent bleeding events. However, frequent dosing with standard-acting FIX products can create a high treatment burden. Long-acting products have been developed to maintain bleed protection with extended dosing intervals. Recombinant factor IX–albumin fusion protein (rIX-FP) is a long-acting product indicated for the treatment and prophylaxis of bleeding events and perioperative management in adult and pediatric patients. This review outlines data from all previously treated patients in the Prophylaxis and On-Demand Treatment using Longer Half-Life rIX-FP (PROLONG-9FP) clinical trial program and summarizes real-world data evaluating the use of rIX-FP in routine clinical practice. In the PROLONG-9FP program, rIX-FP demonstrated effective hemostasis in all patients at dose regimens of up to 21 days in patients aged ≥ 18 years and up to 14 days in patients aged < 12 years. rIX-FP has a favorable pharmacokinetic profile and an excellent safety and tolerability profile. Extended dosing intervals with rIX-FP led to high levels of adherence and reduced consumption compared with other FIX therapies. Data from real-world practice are encouraging and reflect the results of the clinical trials.

Prophylaxis in children with haemophilia in an evolving treatment landscape

INTRODUCTION

For children with haemophilia, early initiation of prophylaxis is crucial to prevent life-threatening bleeds and maintain joint health throughout life. Options for prophylaxis have recently increased from replacement therapy with standard or extended half-life coagulation factor products to include other haemostasis products, such as the non-replacement therapy emicizumab.

AIM

To review key factors that determine the choice of prophylaxis in young children.

METHODS

Key clinical questions on the implementation of prophylaxis for haemophilia in children were identified and PubMed was searched for evidence supporting guidance on the implementation of prophylaxis.

RESULTS

The results of the literature search and the practical experience of the authors were used to build consensus on when to start prophylaxis, the pros and cons of the products available to guide the choice of product, and practical aspects of starting prophylaxis to guide the choice of regimen.

CONCLUSIONS

In this era of increasing therapeutic choices, available information about the range of treatment options must be considered when initiating prophylaxis in young children. Parents or care givers must be sufficiently informed to allow informed shared decision making. Although plentiful data and clinical experience have been gathered on prophylaxis with clotting factor replacement therapy, its use in young children brings practical challenges, such as the need for intravenous administration. In contrast, our relatively brief experience and limited data with subcutaneously administered non-replacement therapy (i.e., emicizumab) in this patient group imply that starting emicizumab prophylaxis in young children requires careful consideration, despite the more convenient route of administration.

Expert opinion paper on the treatment of hemophilia B with albutrepenonacog alfa

Introduction: Current guidelines recommend prophylactic treatment of hemophilia B with the missing coagulation factor IX, either with standard half-life or extended half-life products. Extended half-life products have half-lives three to six times longer than the former, allowing a reduction in the number of weekly injections and therefore, potentially impacting on treatment adherence and quality of life. Albutrepenonacog alfa is an extended half-life fusion protein of coagulation factor IX with recombinant human albumin, indicated for both on-demand and prophylactic treatment for bleeding in patients with hemophilia B of all ages.Areas covered: The authors review the clinical and pharmacokinetic characteristics of albutrepenonacog alfa, as well as the available information regarding trough levels and real-world evidence. Given the availability of other factor IX products in the market, indirect comparisons of clinical and pharmacokinetic characteristics are presented.Expert opinion: The authors exhibit their expert opinion on which patient profiles are candidates for prophylactic treatment with albutrepenonacog alfa, and on the management of patients in terms of dosing, regimens of administration and protocols for switching the treatment.

Efficacy of rFIXFc versus rIX-FP for the Treatment of Patients with Hemophilia B: Matching-Adjusted Indirect Comparison of B-LONG and PROLONG-9FP Trials

Purpose

In patients with hemophilia B, treatment with extended half-life (EHL) recombinant factor IX allows for longer dosing intervals while providing equal or superior bleeding protection compared with standard half-life products. This enables flexible, individualized treatment schedules, which reduce the burden of prophylaxis and improve patient outcomes. This analysis compared the efficacy of recombinant factor IX Fc fusion protein (rFIXFc) and recombinant factor IX albumin fusion protein (rIX-FP), two EHL therapies approved for prophylaxis and treatment of bleeding in hemophilia B.

Patients and Methods

Matching-adjusted indirect treatment comparison (MAIC) was used to adjust the between-treatment differences in baseline characteristics. Individual patient data for rFIXFc (B-LONG) were matched to aggregated data for rIX-FP (PROLONG-9FP) followed by statistical comparison for estimated annualized bleeding rate (ABR) using a Poisson regression model with adjustment for over dispersion. Data were analyzed according to treatment regimen prior to study entry: prior prophylaxis (rFIXFc, n=48; rIX-FP, n=40) or prior episodic treatment (n=43 and n=19, respectively). Relative treatment effects are presented as incidence rate ratios (IRR) with 95% confidence intervals (CI).

Results

After adjustment for baseline characteristics, estimated ABR observed for rFIXFc and rIX-FP was not significantly different in patients on prior prophylaxis (1.87 versus 1.58; IRR 1.18, 95% CI 0.67–2.10) or prior episodic (2.25 versus 2.22; IRR 1.01 95% CI 0.40–2.57) regimens.

Conclusion

This MAIC analysis shows that the estimated ABR for rFIXFc-treated patients from B-LONG was similar to that of rIX-FP-treated patients from PROLONG-9FP and, therefore, indicates that the two EHL therapies provide similar efficacy when used as prophylaxis for patients with hemophilia B. Trough levels differ between the two products (1–3% [targeted] versus 20% [observed], respectively), suggesting that trough level is not a surrogate indicator when ABR is used as a criterion for clinical efficacy when comparing these FIX products in hemophilia B.

In silico comparison of pharmacokinetic properties of three extended half-life factor IX concentrates

Purpose

Pharmacokinetic (PK) differences between the extended half-life (EHL) factor IX (FIX) concentrates for hemophilia B exist, which may influence hemostatic efficacy of replacement therapy in patients. Therefore, we aimed to evaluate the PK properties of three EHL-FIX concentrates and compare them to a standard half-life (SHL) recombinant FIX (rFIX) concentrate.

Methods

Activity-time profiles of PEGylated FIX (N9-GP), FIX linked with human albumin (rIX-FP), FIX coupled to human IgG1 Fc-domain (rFIXFc), and SHL rFIX were simulated for 10,000 patients during steady-state dosing of 40 IU/kg once weekly (EHL-FIX) and biweekly (rFIX) using published concentrate specific population PK models.

Results

Half-lives were respectively 80, 104, and 82 h for N9-GP, rIX-FP, and rFIXFc versus 22 h for rFIX. Between the EHL concentrates, exposure was different with area under the curve (AUC) values of 78.5, 49.6, and 12.1 IU/h/mL and time above FIX target values of 0.10 IU/mL of 168, 168, and 36 h for N9-GP, rIX-FP, and rFIXFc, respectively. N9-GP produced the highest median in vivo recovery value (1.70 IU/dL per IU/kg) compared with 1.18, 1.00, and 1.05 IU/dL per IU/kg for rIX-FP, rFIXFc, and rFIX, respectively.

Conclusions

When comparing EHL products, not only half-life but also exposure must be considered. In addition, variation in extravascular distribution of the FIX concentrates must be taken into account. This study provides insight into the different PK properties of these concentrates and may aid in determination of dosing regimens of EHL-FIX concentrates in real-life.

Tissue distribution of rIX-FP after intravenous application to rodents

BACKGROUND

Hemophilia B is caused by coagulation factor IX (FIX) deficiency. Recombinant fusion protein linking coagulation FIX with recombinant albumin (rIX-FP; Idelvion® ) is used for replacement therapy with an extended half-life. A previous quantitative whole-body autoradiography (QWBA) study investigating the biodistribution of rIX-FP indicated equal biodistribution, but more prolonged tissue retention compared with a marketed recombinant FIX product.

OBJECTIVES

To complete and confirm the QWBA study data by directly measuring rIX-FP protein and activity levels in tissues following intravenous (i.v.) administration to normal rats and FIX-deficient (hemophilia B) mice.

METHODS

After i.v. administration of rIX-FP at a dose of 2000 IU/kg, animals were euthanized at specific time points up to 72 hours postdosing. Subsequently, plasma and various tissues, which were selected based on the previous QWBA results, were harvested and analyzed for FIX antigen levels using an ELISA (both species) or an immunohistochemistry method (mice only), as well as for FIX activity levels (mice only) using a chromogenic assay.

RESULTS

In rats, rIX-FP distributed extravascularly into all tissues analyzed (ie, liver, kidney, skin and knee) with peak antigen levels reached between 1 and 7 hours postdosing. In hemophilia B mice, rIX-FP tissue distribution was comparable to rats. FIX antigen levels correlated well with FIX activity readouts.

CONCLUSIONS

Our results confirm QWBA data showing that rIX-FP distributes into relevant target tissues. Importantly, it was demonstrated that rIX-FP available in tissues retains its functional activity and can thus facilitate its therapeutic activity at sites of potential injury.

Clinical, pharmacokinetic and economic analysis of the first switch to an extended half-life factor IX (albutrepenonacog alfa, rFIX-FP) in Spain

Extended half-life of factor IX (FIX) demonstrated clinical benefit and lower treatment burden than standard half-life FIX products in clinical trials. We analysed the impact in efficacy, pharmacokinetics (PKs) and costs of the switch from nonacog alfa (rFIX) to albutrepenonacog alfa (rFIX-FP) in the first patient with haemophilia B (HB) treated in Spain outside clinical trials. A 7-year-old boy presented with HB with poor venous access and repetition infections using rFIX, which was switched to rFIX-FP. Prophylaxis was adjusted by PKs using WAPPS-Hemo tailoring from 100 IU/kg/week of rFIX to 80 IU/kg/3 weeks of rFIX-FP. Comparing 6 months before, rFIX-FP reduced 68.5% FIX consumption/kg and 58.3% infusion frequency, but total costs/weight showed a slight increase. Ratio of half-life between rFIX and rFIX-FP was 3.4–3.7. This case report revealed that switch to rFIX-FP decreased frequency and FIX consumption, without adverse events and bleeds.

Nonacog beta pegol (N9-GP) in hemophilia B: First report on safety and efficacy in previously untreated and minimally treated patients

BACKGROUND/OBJECTIVE

We report the first analysis of an extended half-life recombinant factor IX, nonacog beta pegol (N9-GP), in previously untreated patients (PUPs) and minimally treated patients with hemophilia B.

METHODS

Paradigm 6 (Safety and Efficacy of Nonacog Beta Pegol [N9-GP] in Previously Untreated Patients With Haemophilia B) is a multicenter, open-label, single-arm, phase 3 trial. Main inclusion criteria were males aged < 6 years, with hemophilia B with factor IX (FIX) activity ≤ 2%, who were previously untreated or with ≤ 3 exposure days (EDs) to FIX-containing products. Patients received N9-GP 40 IU/kg once weekly (prophylaxis) or individualized dosing (preprophylaxis). Bleeds were treated with N9-GP 40 IU/kg (80 IU/kg if severe). The primary end point was incidence of anti-FIX inhibitory antibodies (inhibitors). Secondary end points included safety outcomes and annualized bleeding rate (ABR).

RESULTS

At data cutoff (August 31, 2018), 38 patients had been screened, and 37 had received N9-GP (median age, 1.0 years [range, 0-4]). Total in-trial EDs amounted to 2833, representing ~ 65 patient-years. Two (6.1%) of 33 "at-risk" patients (patients with ≥ 10 EDs plus patients who developed inhibitors) developed high-titer inhibitors and were withdrawn. No other safety concerns, including thromboembolic events, were identified. In the prophylaxis group (n = 28), 67.9% were bleed free; all bleeds (n = 15) were treated with one N9-GP injection; and overall, spontaneous, and traumatic ABRs were low (median ABRs of 0.0, 0.0, and 0.0, respectively; modeled mean ABRs of 0.31, 0.08, and 0.23, respectively). Estimated mean FIX trough activity was 15.0%.

CONCLUSION

We report an inhibitor incidence of 6.1%, which is within the expected range for PUPs with hemophilia B. No other safety concerns were identified; moreover, N9-GP provided effective hemostatic coverage.

Budget impact analysis of extended half-life recombinant factor IX (rFIXFc) in the treatment of haemophilia B

Introduction

Prophylaxis with factor IX (FIX) concentrates, produced by recombinant DNA technology (rFIX) or human plasma-derived concentrates, is the treatment of choice for haemophilia B (HB); rFIX covalently fused to the Fc domain of human immunoglobulin G1 (rFIXFc) allows for prophylaxis/treatment with one infusion every 7-14 days. The purpose of this study is to quantify the financial impact of prophylaxis with rFIXFc vs. other approved rFIX and reimbursed for treatment of HB in Italy.

Methods

The number of patients was estimated according to Italian epidemiological data and use of rFIX. Dose and frequency of administration used for weekly prophylaxis were those recommended in the Summary of Product Characteristics (SPC), while clinical trials and literature data were used to calculate bleeding rates and management. Drug costs were calculated using regional ex-factory net prices. In the model, a reference scenario (Reference) vs. an alternative scenario (Alternative) were created to account for introduction of rFIXFc, estimating an increasing trend of the market share of rFIXFc in a 3-year timeframe. The analysis was developed in the perspective of the National Health Service and included healthcare costs related to rFIX for prophylaxis and resolution of bleeding events.

Results

The model estimated an overall cumulative expenditure (years 1-3) of €209,453,646 for the Reference and €207,465,568 for Alternative scenarios, with calculated cumulative savings of €1,988,068.

Conclusions

The increasing use of rFIXFc as a substitute for other rFIX concentrates in the treatment of HB can represent a financially viable choice for the Italian National Health Service while ensuring effective control of bleeding.

High adherence to prophylaxis regimens in haemophilia B patients receiving rIX-FP: Evidence from clinical trials and real-world practice

Introduction

Adherence to prophylaxis regimens is essential for bleed prevention in haemophilia but remains a challenge due to the need for frequent infusions.

Aim

To evaluate patient adherence to prophylaxis regimens with a long‐acting recombinant factor IX (rIX‐FP; IDELVION^®) in clinical studies and real‐world practice.

Methods

In two phase 3 clinical studies, patients with haemophilia B (FIX ≤2%) recorded their dose, dosing frequency and rIX‐FP consumption in an e‐diary. Adherence to prescribed prophylaxis regimens was assessed in all patients and to prescribed dose in patients ≥12 years only. Additionally, adherence to rIX‐FP prophylaxis regimens in real‐world practice was captured.

Results

In clinical studies, 94.9% (n = 56/59) of patients ≥12 years and 100% (n = 27) of paediatric patients received ≥80% of the expected number of infusions for their assigned prophylaxis schedule. Overall, mean adherence rate was 95.5% across all prophylaxis regimens in patients ≥12 years and 97.9% with a 7‐day regimen in paediatric patients. In patients ≥12 years, 85.7% (n = 54/63) were dose adherent, defined as receiving within 10% of their prescribed dose ≥80% of the time. In real‐world practice, adherence was observed in 100% (n = 14 and n = 15, respectively) of patients in two haemophilia treatment centres and 57.1% (n = 4/7) of patients in a third centre; non‐adherence (n = 3/7) was linked to insurance‐related and parental issues.

Conclusion

In clinical studies, patients with haemophilia B had high adherence rates to rIX‐FP prophylaxis regimens with a variety of dosing intervals, enabling them to achieve very low bleeding rates. High adherence may also be achievable in real‐world practice.

The availability of new drugs for hemophilia treatment

INTRODUCTION

A number of new FVIII/IX concentrates enriched the portfolio of products available for the treatment of hemophilia A/B patients. Due to the large inter-patient variability, accurate tailoring of the therapy became essential to improve patients' adherence, clinical outcomes, and cost/effectiveness ratio. Recently, non-replacement therapies have taken the limelight and succeeded in decreasing the bleedings of patients.

AREAS COVERED

The PK characteristics, efficacy, and safety of the new rFVIII and rFIX concentrates and of non-replacement therapy, are reported in detail in the published clinical trials.

EXPERT OPINION

Outstanding improvements of rFIX concentrates' pharmacokinetics and pharmacodynamics have allowed to reduce the bleedings in hemophilia B patients, in order to increase their adherence to prophylaxis and quality of life. Less significant are the effects of pegylation or Fc fusion on the pharmacokinetics of the new rFVIII concentrates. The new non-replacement therapy is achieving the favor of many treaters and patients, in particular those with Factor VIII inhibitors. Great attention must be paid to the dangerous synergy of APCC and emicizumab, responsible for some fatal events during the clinical trials and compassionate use of this drug. So far, replacement therapy should be the standard of care for hemophilia patients without inhibitors or difficulties in venous access.

Switching patients in the age of long-acting recombinant products?

Introduction: Prophylaxis with factor replacement therapy is the gold standard for the treatment of hemophilia, but this often requires frequent infusions. A number of long-acting factor products have been developed to reduce the burden on patients. Areas covered: This is an overview of information presented at two symposia held at the World Federation of Hemophilia and International Society on Thrombosis and Haemostasis - Scientific and Standardization Committee annual meetings. The pharmacokinetic, safety and efficacy data for long-acting recombinant products are reviewed, with a focus on recombinant factor IX albumin fusion protein (rIX-FP) and rVIII-SingleChain. This overview also provides a guide for managing a patient's switch to long-acting products. Expert opinion: Long-acting products may allow patients to maintain or decrease bleeding rates whilst increasing their dosing interval, which may in turn reduce the burden on patients and caregivers. When switching patients to long-acting products health-care professionals should provide balanced and thorough education to the patient, whilst supporting their emotional well-being. Regimens should address patients' needs and goals but should also be guided by clinical phenotype and pharmacokinetic assessment. Follow-up should assess safety concerns, bleeding rates, joint health and the impact of the regimen on patients' lifestyle.

Long-term safety and sustained efficacy for up to 5 years of treatment with recombinant factor IX Fc fusion protein in subjects with haemophilia B: Results from the B-YOND extension study

INTRODUCTION

Recombinant factor IX Fc fusion protein (rFIXFc) has demonstrated efficacy for treatment of haemophilia B in the Phase 3 B-LONG and Kids B-LONG studies. However, long-term rFIXFc safety and efficacy data have not yet been reported.

AIM

To report long-term rFIXFc safety and efficacy in subjects with haemophilia B.

METHODS

B-YOND (NCT01425723) was an open-label extension for eligibl previously treated subjects who completed B-LONG or Kids B-LONG. Subjects received ≥1 treatment regimen: weekly prophylaxis (WP), individualized interval prophylaxis (IP), modified prophylaxis or episodic treatment. Subjects could switch regimens at any time. The primary endpoint was inhibitor development.

RESULTS

Ninety-three subjects from B-LONG and 27 from Kids B-LONG (aged 3-63 years) were enrolled. Most subjects received WP (B-LONG: n = 51; Kids B-LONG: n = 23). For subjects from B-LONG, median (range) treatment duration was 4.0 (0.3-5.4) years and median (range) number of exposure days (EDs) was 146 (8-462) EDs. Corresponding values for paediatric subjects were 2.6 (0.2-3.9) years and 132 (50-256) EDs. No inhibitors were observed (0 per 1000 subject-years; 95% confidence interval, 0-8.9) and the overall rFIXFc safety profile was consistent with prior studies. Annualized bleed rates remained low and extended-dosing intervals were maintained for most subjects. Median dosing interval for the IP group was approximately 14 days for adults and adolescents (n = 31) and 10 days for paediatric subjects (n = 5).

CONCLUSIONS

B-YOND results confirm the long-term (up to 5 years, with cumulative duration up to 6.5 years) well-characterized safety and efficacy of rFIXFc treatment for haemophilia B.

Real-World Utilisation and Bleed Rates in Patients with Haemophilia B Who Switched to Recombinant Factor IX Fusion Protein (rIX-FP): A Retrospective International Analysis

Introduction

Despite the well-documented benefits of prophylaxis, treatment burden is still a barrier to adherence in patients with haemophilia. An extended half-life fusion protein linking recombinant FIX (rFIX) with human albumin (rIX-FP) has been developed for the treatment of patients with haemophilia B and is indicated for dosing up to every 14 days. This analysis evaluated real-world outcomes in patients switching to rIX-FP from the previous FIX product in Italy, Belgium and the UK.

Methods

Anonymised chart data were collected from the pre-existing medical records of patients with haemophilia B between May and September 2018. Patients were included in the analysis if they had been treated with rIX-FP for ≥ 8 weeks. Data were compared between rIX-FP and the patient’s prior FIX product.

Results

Twenty-three HTCs from Italy (n = 13), Belgium (n = 3) and the UK (n = 7) provided data for 84 male patients, 92.8% of which had severe haemophilia B. The majority of patients were previously on prophylactic regimens with their prior FIX product (Italy, 44/49; Belgium, 7/10; UK, 22/25). The switch to prophylaxis with rIX-FP led to reductions in mean annualised bleeding rate of 94.3% in Italy, 93.9% in Belgium and 67.7% in the UK compared with prior FIX prophylaxis. Overall, 41% of patients experienced zero spontaneous bleeds prior to switching, compared with 88% following the switch to rIX-FP. The majority of patients had a reduction in dosing frequency following the switch, with 98.6% of patients dosing once weekly or less frequently compared with 9.6% of patients dosing at this frequency with their prior FIX. Mean weekly FIX consumption was reduced compared with prior FIX prophylaxis.

Conclusion

This retrospective review of real-world evidence demonstrated that switching to rIX-FP from prior FIX was associated with improved haemostatic efficacy and reduced factor consumption in patients with haemophilia B from Italy, Belgium and the UK.

While clinical trials provide robust evidence as to the effectiveness and safety of a new drug, they are tightly controlled and so may not reflect some of the issues that may be discovered in clinical practice. Therefore, real-world analyses are important to determine how a product performs in patients in everyday settings. This study looked at the use of an extended half-life fusion protein linking recombinant FIX (rFIX) with human albumin (rIX-FP), which was designed to allow longer dosing intervals, in patients with haemophilia B in Italy, Belgium and the UK, and compared this with the patients’ previous FIX product. Anonymous patient chart data were collected from participating centres and analysed in terms of bleeding rate, factor usage and dosing frequency for rIX-FP and previous FIX product. The results showed that after switching to rIX-FP, patients experienced lower bleeding rates, lower factor usage and less frequent dosing regimens compared with their previous FIX product. This is the first analysis to assess the real-world clinical benefits of switching to prophylaxis with rIX-FP from a prior FIX product in Italy, Belgium and the UK. This study further strengthens the results seen in clinical trials with rIX-FP, confirming that the effective bleeding prevention demonstrated in clinical trials is consistent with that seen in patients in real-world clinical practice.

Using pharmacokinetics for tailoring prophylaxis in people with hemophilia switching between clotting factor products: A scoping review

The objective of this scoping review is to summarize the current use of pharmacokinetics for tailoring prophylaxis in hemophilia patients switching between clotting factor products. Patients with hemophilia may require switching of clotting factor concentrates due to a variety of factors, but there have been perceived risks associated with switching, such as inhibitor development or suboptimal protection due to inadequate dosing while titrating treatment. Studies that look at patients switching from one clotting factor concentrate to another are categorized in terms of their primary and/or secondary objectives, notably biosimilarity and comparative pharmacokinetic studies and inhibitor development studies. Research on how best to switch concentrates with respect to dosing regimen are lacking, and currently a trial-and-error approach is used for dosing the new factor concentrate. In the future, studies looking at the predictability of pharmacokinetics (PK) of a new factor concentrate based on individual PK knowledge of the original factor concentrate may offer clinical benefit by providing a safer switching approach and protocol.

Performance of a recombinant fusion protein linking coagulation factor IX with recombinant albumin in one-stage clotting assays

Essentials Performance of the one-stage clotting (OSC) assay varies with the clotting activator used. Recombinant FIX-albumin fusion protein (rIX-FP) was reliably monitored with most OSC reagents. rIX-FP shows comparable reagent-dependent variability to other rFIX products in the OSC assay. Actin® FS and kaolin-based reagents underestimated rIX-FP activity by around 50% in the OSC assay. SUMMARY: Background Measuring factor IX activity (FIX:C) with one-stage clotting (OSC) assays, based on the activated partial thromboplastin time (APTT), is the current mainstay of diagnostic techniques for hemophilia B. Assessing the performance of new recombinant FIX (rFIX) products in OSC assays is essential, as APTT reagents from different manufacturers yield different potency estimates for rFIX. Objectives To evaluate the extent to which choice of reagent composition influences rFIX potency measurements of recombinant FIX-albumin fusion protein (rIX-FP, IDELVION) activity in OSC assays. Methods rIX-FP was added to FIX-deficient plasma, and FIX:C was assessed centrally and locally in a multicenter international field study with a variety of commercial OSC APTT reagents. Paired sample analysis of clinical samples was performed to compare values of FIX:C from local and central laboratories. In-house bioanalytical investigations with spiked samples were conducted to compare the APTT-reagent dependent variability of rIX-FP with unmodified rFIX and rFIX Fc fusion protein (rFIXFc). Results Central and local assessments of FIX:C from 10 countries and 21 participating centers showed comparable results to those from the central laboratory across the majority of 18 different APTT reagents from both clinical and spiked samples. There was a consistent underestimation of rIX-FP activity of ≈ 50% with OSC assays using Actin FS or kaolin-based APTT reagents. In the bioanalytical study, rIX-FP showed comparable variability in OSC assays to unmodified rFIX and rFIXFc. Conclusions rIX-FP activity can be accurately measured by the use of OSC assays with the majority of commercial reagents. Actin FS or kaolin-based reagents will probably lead to a 50% underestimation of activity.

Health-related quality of life in paediatric haemophilia B patients treated with rIX-FP

INTRODUCTION

Frequent infusions and bleeds can impact on the health-related quality of life (HRQoL) of paediatric haemophilia B patients. rIX-FP (IDELVION^® ) is a fusion protein linking recombinant factor IX with recombinant albumin, and is associated with low bleeding rates with a weekly regimen, which could improve HRQoL.

AIMS

To measure the effect of rIX-FP prophylaxis on the HRQoL of paediatric patients and treatment satisfaction in their caregivers using the Haemo-QoL and Hemo-SAT_P questionnaires, respectively.

METHODS

At baseline and end-of-study (EOS), patients 4-11 years old participating in the PROLONG-9FP program answered the Haemo-QoL questionnaire and gave information on their socio-demographic data and physical activity. Caregivers completed the Hemo-Sat_P . Minimal important differences (MID) (|Cohen's d| > 0.5) between baseline and EOS and the number of responders (patients with meaningful subject-level improvements over time) at EOS were calculated.

RESULTS

Twenty patients (age group I: 4-7 years old [n = 12]; age group II: 8-12 years old [n = 8]) completed the Haemo-QoL questionnaire at baseline. MIDs were found in age group I representing improvement for "physical health" (d = -0.547) domain; 60% of patients were responders for "physical health." In age group II, MIDs were seen in most domains; 71.4% patients were responders in "total score." In caregivers, improvements were seen for most domains of the Hemo-Sat_P with a small effect size. Fewer patients missed school when treated with rIX-FP and 94.1% patients maintained their physical activity level.

CONCLUSION

Prophylaxis with rIX-FP led to substantial improvements in HRQoL in paediatric patients and treatment satisfaction in caregivers.

Updates in clinical trial data of extended half-life recombinant factor IX products for the treatment of haemophilia B

Whilst the global prevalence of haemophilia B is less than that of haemophilia A, rapid and remarkable innovations have been made in the development of haemophilia B therapies in the last decade. The most recent developments are the evolution of extended half-life haemophilia B replacement therapies which are designed to reduce the treatment burden associated with prophylactic infusion of factor IX (FIX) to prevent bleeding in haemophilia B participants. Clinical development programmes have culminated in the completion of three phase III studies on extended half-life (EHL) recombinant FIX (rFIX) products and subsequent approval and registration of these in many countries around the world. Current data from the three EHL rFIX clinical studies indicate that these products have acceptable safety profiles with no allergic reactions, thromboembolic phenomena or neutralizing antibodies when given to previously treated adolescent and adults for the prevention of bleeds, for the treatment of bleeds and in the perisurgical haemostasis use. Studies in previously untreated paediatric participants are currently ongoing. The EHL rFIX products have the potential impact to reduce the treatment burden associated with prophylactic infusion of replacement FIX, to treat and prevent bleeds in participants with haemophilia B and to improve the participant's health-related quality of life. The impact of EHL rFIX is likely to be modified by current development of other haemophilia B therapy such as antitissue factor pathway inhibitors and haemophilia B gene therapy. In this review, we aim to provide an update on the safety and efficacy data from the three EHL rFIX clinical studies and to consider their roles in the face of novel haemophilia B therapy currently evolving.

The benefits of prophylaxis in patients with hemophilia B

INTRODUCTION

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

Prophylactic versus on-demand treatments for hemophilia: advantages and drawbacks

INTRODUCTION

Early long-term prophylaxis is the standard of care to prevent joint bleeding and chronic arthropathy in patients with severe hemophilia. Areas covered: Despite the obvious prophylaxis advantages upon the clinical outcomes, there are still several drawbacks to be addressed for the optimal patients' compliance. Frequency of treatment due to short half-life of conventional FVIII and FIX concentrates, difficult venous access, adherence to the prescribed therapy and costs may represent significant critical issues. The development of inhibitors also makes replacement therapy ineffective, preventing patients from receiving long-term prophylaxis. This paper will review these drawbacks and the tools to overcome these limitations, mainly thanks to the use of extended half-life products and the development of novel non-conventional therapeutic approaches. Expert commentary: The use of extended half-life products may help in reducing the burden of the frequent intravenous administration and in better tailoring an individualized prophylaxis. The development of novel therapeutic approaches, like the bi-specific antibody mimicking the coagulation function of FVIII or inhibition of anticoagulant proteins may facilitate prophylaxis treatment not only in patients with inhibitors, but also in severe hemophilia patients without inhibitors. Exciting opportunities are emerging for improving prophylaxis in hemophilia.

Extended Half-Life Factor VIII and Factor IX Preparations

In the last couple of years, several extended half-life factor VIII and factor IX preparations were intensively studied and gained approval. In order to extend half-lives, techniques like fusion to protein conjugates (Fc part of IgG₁ or albumin), chemical modification (PEGylation), and protein sequence modification are implemented. With these techniques, it is possible to extend half-lives of factor IX products 4- to 6- fold, while half-life extension of factor VIII products is limited to 1.5- to 2-fold due to their interaction with von Willebrand factor. Nevertheless, both extended half-life factor VIII and IX products have improved and facilitated prophylactic factor replacement therapy in hemophilia A and B, respectively. Extended half-life factor concentrates pose challenges to coagulation laboratories because accurate therapy monitoring is not possible with all factor activity assays currently used.

Outcome of Clinical Trials with New Extended Half-Life FVIII/IX Concentrates

The development of a new generation of coagulation factors with improved pharmacokinetic profile will change the paradigm of treatment of persons with hemophilia (PWH). The standard treatment in PWH is represented by regular long-term prophylaxis that, given intravenously twice or thrice weekly, is associated with a not-negligible burden on patients' quality of life. The availability of drugs with improved pharmacokinetic profile may improve prophylaxis feasibility and protection against bleeding episodes. This article summarizes the main results obtained from clinical trials with modified factor VIII (FVIII) and factor IX (FIX) molecules. Published literature on new molecules for replacement treatment in hemophilia A and B was retrieved using PubMed search, and all ongoing clinical trials have been researched via www.clinicaltrials.gov. Such new molecules are usually engineered to have a longer plasma half-life than that which has been obtained by chemical modification (i.e., conjugation with polyethylene glycol, PEG) or by creating recombinant fusion proteins. Results from phase I/III studies in previously treated adults and children are now available for the vast majority of new products, including the results of their use in a surgical setting. On the contrary, trials involving previously untreated patients are still ongoing for all and results not yet available.