Pharmacokinetics, efficacy and safety of BAX326, a novel recombinant factor IX: a prospective, controlled, multicentre phase I/III study in previously treated patients with severe (FIX level <1%) or moderately severe (FIX level ≤2%) haemophilia B

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.

International consensus recommendations on the management of people with haemophilia B

Haemophilia B is a rare X-linked genetic deficiency of coagulation factor IX (FIX) that, if untreated, can cause recurrent and disabling bleeding, potentially leading to severe arthropathy and/or life-threatening haemorrhage. Recent decades have brought significant improvements in haemophilia B management, including the advent of recombinant FIX and extended half-life FIX. This therapeutic landscape continues to evolve with several non-factor replacement therapies and gene therapies under investigation. Given the rarity of haemophilia B, the evidence base and clinical experience on which to establish clinical guidelines are relatively sparse and are further challenged by features that are distinct from haemophilia A, precluding extrapolation of existing haemophilia A guidelines. Due to the paucity of formal haemophilia B-specific clinical guidance, an international Author Group was convened to develop a clinical practice framework. The group comprised 15 haematology specialists from Europe, Australia, Japan, Latin America and North America, covering adult and paediatric haematology, laboratory medicine and biomedical science. A hybrid approach combining a systematic review of haemophilia B literature with discussion of clinical experience utilized a modified Delphi format to develop a comprehensive set of clinical recommendations. This approach resulted in 29 recommendations for the clinical management of haemophilia B across five topics, including product treatment choice, therapeutic agent laboratory monitoring, pharmacokinetics considerations, inhibitor management and preparing for gene therapy. It is anticipated that this clinical practice framework will complement existing guidelines in the management of people with haemophilia B in routine clinical practice and could be adapted and applied across different regions and countries.

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.

Clotting factor concentrates for preventing bleeding and bleeding-related complications in previously treated individuals with haemophilia A or B

BACKGROUND

The hallmark of severe hemophilia (A or B) is recurrent bleeding into joints and soft tissues with progressive joint damage, despite on-demand treatment. Prophylaxis has long been used, but not universally adopted, because of medical, psychosocial, and cost controversies.

OBJECTIVES

To determine the effectiveness of clotting factor concentrate prophylaxis in managing previously-treated individuals with hemophilia A or B.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group's Coagulopathies Trials Register, compiled from electronic database searches and handsearching of journals and conference abstract books. In addition, we searched MEDLINE and Embase and online trial registries. Most recent search of Group's Coagulopathies Trials Register: 24 February 2021.

SELECTION CRITERIA

Randomised controlled trials (RCTs) and quasi-RCTs evaluating people with hemophilia A or hemophilia B, who were previously treated with clotting factor concentrates to manage their hemophilia.

DATA COLLECTION AND ANALYSIS

Two authors independently reviewed trials for eligibility, assessed risk of bias and extracted data. The authors used the GRADE criteria to assess the certainty of the evidence.

MAIN RESULTS

Ten trials (including 608 participants) were eligible for inclusion. Eight of the trials (477 participants) had arms comparing two or more prophylactic regimens to one another and four of the trials (n = 258) compared prophylaxis to on-demand treatment (two trials had multiple arms and were included in both comparisons). Comparison of two or more prophylactic regimens For trials comparing one prophylaxis regimen to another, given the heterogeneity of the data, none of the data were pooled for this comparison. Considering the individual trials, three trials reported the primary outcome of joint bleeding, and none showed a dfference between dosing regimens (low-certainty evidence). For the secondary outcome of total bleeding events, prophylaxis with a twice-weekly regimen of FIX likely results in reduced total bleeds compared to a once-a-week regimen of the same dose, mean difference (MD) 11.2 (5.81 to 16.59) (one trial, 10 participants, low-certainty evidence). Transient low-titer anti-FVIII inhibitors were reported in one of the trials. Blood-transmitted infections were not identified. Other adverse events reported include hypersensitivity, oedema, and weight gain. These were, however, rare and unrelated to study drugs (very low-certainty evidence). Comparison of prophylactic and on-demand regimens Four of the trials (258 participants) had arms that compared prophylaxis to on-demand treatment. Prophylaxis may result in a large decrease in the number of joint bleeds compared to on-demand treatment, MD -30.34 (95% CI -46.95 to -13.73) (two trials, 164 participants, low-certainty evidence). One of these trials (84 participants) also reported the long-term effects of prophylaxis versus on-demand therapy showing improved joint function, quality of life, and pain; but no differences between groups in joint structure when assessed by magnetic resonance imaging (MRI). In one trial (84 participants) validated measures for joint health and pain assessment showed that prophylaxis likely improves joint health compared to an on-demand regimen with an estimated change difference of 0.94 points (95% CI 0.23 to 1.65) and improves total pain scores, MD -17.20 (95% CI -27.48 to -6.92 (moderate-certainty evidence). Two trials (131 participants) reported that prophylaxis likely results in a slight increase in adverse events, risk ratio 1.71 (1.24 to 2.37) (moderate-certainty evidence). No inhibitor development and blood-transmitted infections were identified. Overall, the certainty of the body of evidence was judged to be low because of different types of bias that could have altered the effect.   AUTHORS' CONCLUSIONS: There is evidence from RCTs that prophylaxis, as compared to on-demand treatment, may reduce bleeding frequency in previously-treated people with hemophilia. Prophylaxis may also improve joint function, pain and quality of life, even though this does not translate into a detectable improvement of articular damage when assessed by MRI.  When comparing two different prophylaxis regimens, no significant differences in terms of protection from bleeding were found. Dose optimization could, however, result in improved efficacy. Given the heterogeneity of the data, pooled estimates were not obtained for most comparisons.  Well-designed RCTs and prospective observational controlled studies with standardised definitions and measurements are needed to establish the optimal and most cost-effective treatment regimens.

Safety, Immunogenicity, and Hemostatic Efficacy of Nonacog Gamma in Patients With Severe or Moderately Severe Hemophilia B: A Continuation Study

This phase 3, prospective, open-label, multicenter, continuation study (NCT01286779) investigated the use of a recombinant factor IX (FIX), nonacog gamma (BAX 326, RIXUBIS^®) in patients with severe or moderately severe hemophilia B. The study population included 85 patients transitioning from a phase 1/3 pivotal study (NCT01174446), a pediatric study (NCT01488994), and 30 newly recruited patients, naïve to nonacog gamma. Patients received nonacog gamma as prophylaxis treatment (standard, modified or PK-tailored) or on-demand, as determined by the investigator. Treatment was assessed for safety, immunogenicity, hemostatic efficacy and consumption. In this study, after ≥100 exposure days, nonacog gamma resulted in no treatment-related serious adverse events, and no patients developed inhibitory antibodies to FIX. Nonacog gamma was efficacious at controlling bleeding episodes, with an 89.1% overall hemostatic efficacy rating of excellent or good, and 56% of bleeds resolved with one infusion. The annualized bleeding rate was considerably lower during prophylactic treatment (median ABR of 1.3 in 108 patients) than during on-demand treatment (median ABR of 16.5 in 13 patients). These results show that in previously treated patients and nonacog gamma-naïve patients, long-term use of nonacog gamma had acceptable safety and tolerability, and was efficacious as a prophylactic treatment for the management of bleeding episodes.

NCT01286779, EudraCT: 2010-022726-33

Phase 3 Clinical Trial: Perioperative Use of Nonacog Gamma, a Recombinant Factor IX, in Previously Treated Patients With Moderate/Severe Hemophilia B

Hemostatic management is essential for ensuring the safety of patients with hemophilia during surgery. This phase 3, prospective, uncontrolled trial, evaluated hemostatic efficacy, consumption, and safety of a recombinant factor IX concentrate, nonacog gamma (BAX 326, Rixubis^® [Baxalta US Inc., a Takeda company, Lexington, MA, USA]), in intraoperative and postoperative settings in previously treated patients (PTPs) with severe or moderately severe hemophilia B undergoing elective surgery (N = 38 surgeries; 21 major, 17 minor). Predefined preoperative hemostatic factor IX levels (80-100% of normal for major and 30-60% for minor surgeries) were maintained for each patient. Intraoperative efficacy was rated as “excellent” or “good” for all surgeries. Postoperative hemostatic efficacy on day of discharge was rated as “excellent,” “good,” and “fair,” respectively, for 29 (76.3%), 7 (18.4%), and 2 (5.3%) surgical procedures. All adverse events were considered unrelated to study drug; most frequently reported was mild procedural pain (9 patients). No thrombotic events, severe allergic reactions, or inhibitor formation were observed. Nonacog gamma was well tolerated and effective for intraoperative and postoperative hemostatic management of PTPs with hemophilia B.

NCT01507896, EudraCT: 2011-000413-39

The Cost-effectiveness of Gene Therapy for Severe Hemophilia B: Microsimulation Study from the United States Perspective

Adeno-associated virus (AAV)-mediated gene therapy is a novel treatment promising to reduce morbidity associated with hemophilia. While multiple clinical trials continue to evaluate efficacy and safety, limited cost-effectiveness data have been published. This study compared the potential cost-effectiveness of AAV-mediated factor IX(FIX)-Padua gene therapy for severe hemophilia B patients in the United States (US) to on-demand FIX replacement and primary FIX prophylaxis, using either standard or extended half-life FIX products. A microsimulation Markov model was constructed and transition probabilities between health states and utilities were informed by published data. Costs were aggregated using a micro-costing approach. An 18-years-old till death time-horizon from the perspective of a third-party payer in the US was conducted. Gene therapy was more cost-effective than both alternatives considering a $150,000/QALY threshold. The price for gene therapy was assumed $2,000,000 in the base-case scenario, yet one of the one-way sensitivity analyses was conducted using observed manufacturing, administration and five-year follow-up cost of $87,198 for AAV-mediated gene therapy vector as derived from the manufacturing facility and clinical practice at St. Jude Children's Research Hospital. One-way sensitivity analyses showed 10/102 scenarios in which gene therapy was not cost-effective compared to alternative treatments. Notably, gene therapy remained cost-effective in a hypothetical scenario in which we estimated that the discounted factor concentrate price was 20% of the wholesale acquisition cost in the US. Probabilistic sensitivity analysis estimated gene therapy cost-effective at 92% of simulations considering $150,000/QALY threshold. In conclusion, based on detailed simulation inputs and assumptions, gene therapy was more cost-effective than on-demand treatment and prophylaxis for patients with severe hemophilia B.

Safety and effectiveness of Rixubis in patients with hemophilia B: a real-world, prospective, postmarketing surveillance study in South Korea

Background

Rixubis (recombinant factor IX, nonacog gamma) is indicated for the control and prevention of bleeding episodes, perioperative management, and routine prophylaxis in hemophilia B patients. This real-world, postmarketing surveillance study aimed to evaluate the safety and effectiveness of Rixubis in adult and pediatric hemophilia B patients in South Korea.

Methods

This prospective, observational, multicenter study (clinicaltrials.gov identifier NCT029 22231) was conducted in hemophilia B patients between April 2015 and April 2019, who were observed for up to 6 months after the initiation of Rixubis treatment. Safety was evaluated based on the number and severity of adverse events (AEs) and serious AEs (SAEs). Hemostatic effectiveness was assessed by physicians and patients by using a four-point scale and rated as excellent, good, fair, or no response based on treatment type.

Results

In all, 58 patients were enrolled from four centers by seven physicians during the study period. The safety and effectiveness analysis sets included 57 and 54 patients, respectively. Overall, 11 AEs were reported in eight patients (14.0%), of which three were SAEs and occurred in three patients (5.3%). All 11 AEs were reported as unexpected and mild in severity, with no anaphylactic reaction, and 10 AEs (90.9%) resolved. The majority of AEs (10) were unrelated to Rixubis. Of the 142 hemostatic effectiveness assessments, 123 (86.6%) were reported as good or excellent.

Conclusion

Rixubis demonstrated an acceptable safety and effectiveness profile in the treatment of bleeding, perioperative management, and prophylaxis in hemophilia B patients in a real-world setting in South Korea.

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.

Systematic review and analysis of efficacy of recombinant factor IX products for prophylactic treatment of hemophilia B in comparison with rIX-FP

Aims: Prophylaxis with standard-acting recombinant factor IX (rFIX) in hemophilia B patients requires frequent injections. Extended half-life (EHL) products allow for prolonged dosing intervals, and so reduce this treatment burden. Three technologies are employed to extend the half-life of FIX; glycopegylation, Fc-fusion, and albumin fusion. rIX-FP is a novel albumin fusion protein, which allows for a prolonged dosing interval of up to 14 days. A systematic review and indirect statistical comparison was performed to evaluate the efficacy of both EHL and standard-acting rFIX products compared with rIX-FP in Phase III trials for prophylaxis in adult hemophilia B patients. Materials and methods: A systematic search was conducted in both EMBASE and PubMed to identify Phase III trials of prophylactic rFIX treatment in previously treated hemophilia B patients aged ≥12 years (FIX ≤2%). Annualized bleeding rate (ABR), spontaneous ABR (AsBR), and joint ABR (AjBR) data were extracted from each study. A z-test was performed using the mean of each parameter, and the mean difference in outcome between studies was calculated. Results: Seven articles investigating six rFIX products were identified. Median ABR, AsBR, and AjBR ranged from 0-3.0, 0-1.0, and 0-1.1 (means = 0.8-4.26, 0.13-2.6, and 0.34-2.85), respectively. rIX-FP achieved the lowest median and mean values in all three parameters. Z-tests showed that mean ABR was significantly lower for rIX-FP 7-day prophylaxis compared with the majority of standard-acting and other EHL rFIX products. Limitations: The low number of appropriate trials available for comparison limits the quantity of data available for comparison, and restricts the use of methods of adjustment for variance in study design or patient characteristics. However, these limitations are shared with similar analyses published in this field. Conclusion: This indirect comparison of Phase III trials indicates that rIX-FP efficacy compares favorably vs other rFIX products for prophylaxis in hemophilia B.

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.

The benefits of prophylaxis in patients with hemophilia B

INTRODUCTION

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

Advances and innovations in haemophilia treatment

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

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

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

Trenonacog alfa for prophylaxis, on-demand and perioperative management of hemophilia B

INTRODUCTION

Current treatment for hemophilia B involves replacing the missing coagulation factor IX (FIX) with either plasma-derived or recombinant (r) FIX. Trenonacog alfa is the third normal half-life rFIX that has been granted FDA approval. Area covered: In this review, the authors examine trenonacog alfa for the treatment of hemophilia B including prophylaxis, on-demand and perioperative hemostasis. They compare the PK profile to nonacog alfa and evaluate the drug's efficacy and safety from published studies. Expert opinion: Trenonacog alfa appears to be an effective and safe treatment option for patients with hemophilia B with a PK profile similar to that of nonacog alfa. Despite the advent of extended half-life rFIX and other novel therapeutic approaches, normal half-life rFIX products, including trenonacog alfa, are likely to continue to have a place in hemophilia B treatment for at least the immediate future while the new landscape takes shape, particularly in countries that cannot afford the newer treatments.

Economic Burden of Illness among Persons with Hemophilia B from HUGS Vb: Examining the Association of Severity and Treatment Regimens with Costs and Annual Bleed Rates

OBJECTIVES

To determine US societal burden of illness, including direct and indirect costs and annual bleed rate (ABR), for persons with hemophilia B (HB), a rare and debilitating genetic disorder, and to examine associations of hemophilia severity and treatment regimens with costs and ABR.

METHODS

From 2009 to 2014, the Hemophilia Utilization Group Studies Part Vb collected prospective data from 10 US hemophilia treatment centers. Participants with HB completed initial surveys on sociodemographic characteristics, clinical characteristics, and treatment patterns. During the 2-year follow-up, participants reported bleeding episodes, work absenteeism, and caregiver time quarterly. These data were used to calculate ABR and indirect costs. Direct costs were calculated using 1-year clinical chart records and 2-year dispensing records.

RESULTS

Of the 148 participants, 112 with complete medical records and one or more follow-up survey were included. Total mean annual per-person costs were $85,852 (median $20,160) for mild/moderate HB, $198,733 (median $147,891) for severe HB, and $140,240 (median $63,617) for all participants without inhibitors (P < 0.0001). Mean ABR for participants with severe HB on prophylaxis (5.5 ± 7.9 bleeds/y) was almost half that of those treated episodically. Clotting factor and indirect costs accounted for 85% and 9% of total costs, respectively. Compared with episodic treatment, prophylaxis use was associated with 2.5-fold higher clotting factor costs (P < 0.01), low but significantly more missed parental workdays (P < 0.0001) and clinician (P < 0.001) or nursing visits (P < 0.0001), less part-time employment and unemployment, and lower hospitalizations costs (P = 0.17) and ABR (P < 0.0001).

CONCLUSIONS

HB is associated with high economic burden, primarily because of clotting factor costs. Nevertheless, prophylaxis treatment leads to clinical benefits and may reduce other nonfactor costs.

Continuous prophylaxis with recombinant factor IX Fc fusion protein and conventional recombinant factor IX products: comparisons of efficacy and weekly factor consumption

BACKGROUND

Continuous prophylaxis for patients with hemophilia B requires frequent injections that are burdensome and that may lead to suboptimal adherence and outcomes. Hence, therapies requiring less-frequent injections are needed. In the absence of head-to-head comparisons, this study compared the first extended-half-life-recombinant factor IX (rFIX) product-recombinant factor IX Fc fusion protein (rFIXFc)-with conventional rFIX products based on annualized bleed rates (ABRs) and factor consumption reported in studies of continuous prophylaxis.

METHODS

This study compared ABRs and weekly factor consumption rates in clinical studies of continuous prophylaxis treatment with rFIXFc and conventional rFIX products (identified by systematic literature review) in previously-treated adolescents and adults with moderate-to-severe hemophilia B. Meta-analysis was used to pool ABRs reported for conventional rFIX products for comparison. Comparisons of weekly factor consumption were based on the mean, reported or estimated from the mean dose per injection.

RESULTS

Five conventional rFIX studies (injections 1 to >3 times/week) met the criteria for comparison with once-weekly rFIXFc reported by the B-LONG study. The pooled mean ABR for conventional rFIX was slightly higher than but comparable to rFIXFc (difference=0.71; p = 0.210). Weekly factor consumption was significantly lower with rFIXFc than in conventional rFIX studies (difference in means = 42.8-74.5 IU/kg/week [93-161%], p < 0.001).

CONCLUSION

Comparisons of clinical study results suggest weekly injections with rFIXFc result in similar bleeding rates and significantly lower weekly factor consumption compared with more-frequently-injected conventional rFIX products. The real-world effectiveness of rFIXFc may be higher based on results from a model of the impact of simulated differences in adherence.

Long-term safety and efficacy of extended-interval prophylaxis with recombinant factor IX Fc fusion protein (rFIXFc) in subjects with haemophilia B

The safety, efficacy, and prolonged half-life of recombinant factor IX Fc fusion protein (rFIXFc) were demonstrated in the Phase 3 B-LONG (adults/adolescents ≥12 years) and Kids B-LONG (children <12 years) studies of subjects with haemophilia B (≤2 IU/dl). Here, we report interim, long-term safety and efficacy data from B-YOND, the rFIXFc extension study. Eligible subjects who completed B-LONG or Kids B-LONG could enrol in B-YOND. There were four treatment groups: weekly prophylaxis (20-100 IU/kg every 7 days), individualised prophylaxis (100 IU/kg every 8-16 days), modified prophylaxis (further dosing personalisation to optimise prophylaxis), and episodic (on-demand) treatment. Subjects could change treatment groups at any point. Primary endpoint was inhibitor development. One hundred sixteen subjects enrolled in B-YOND. From the start of the parent studies to the B-YOND interim data cut, median duration of rFIXFc treatment was 39.5 months and 21.9 months among adults/adolescents and children, respectively; 68/93 (73.1 %) adults/adolescents and 9/23 (39.1 %) children had ≥100 cumulative rFIXFc exposure days. No inhibitors were observed. Median annualised bleeding rates (ABRs) were low in all prophylaxis regimens: weekly (≥12 years: 2.3; <6 years: 0.0; 6 to <12 years: 2.7), individualised (≥12 years: 2.3; 6 to <12 years: 2.4), and modified (≥12 years: 2.4). One or two infusions were sufficient to control 97 % (adults/adolescents) and 95 % (children) of bleeding episodes. Interim data from B-YOND are consistent with data from B-LONG and Kids B-LONG, and confirm the long-term safety of rFIXFc, absence of inhibitors, and maintenance of low ABRs with prophylactic dosing every 1 to 2 weeks.

Population pharmacokinetics of a new long-acting recombinant coagulation factor IX albumin fusion protein for patients with severe hemophilia B

Essentials The new recombinant factor IX (FIX) albumin fusion protein (rIX-FP) has a prolonged half-life. A population pharmacokinetic (PK) model was based on FIX activity levels of hemophilia B patients. The model was used to simulate different dosing scenarios of rIX-FP to help guide dosing. The population PK model supported prolonged dosing of rIX-FP with intervals of up to 2 weeks. Click to hear Prof.Makris's presentation on new treatments in hemophilia SUMMARY: Background The recombinant fusion protein linking recombinant coagulation factor IX with recombinant albumin (rIX-FP; Idelvion® ) exhibits a longer half-life than plasma-derived factor IX (FIX) and the commercially available recombinant FIX products. Objectives (i) Characterize the population pharmacokinetics (PK) of rIX-FP in hemophilia B patients, (ii) identify covariates that are potential determinants of rIX-FP PK variability and (iii) simulate different dosing scenarios of rIX-FP following single and steady-state dosing. Patients/Methods A population PK model was developed based on FIX activity levels of 104 patients who had received treatment with rIX-FP. Patients were aged 1-65 years with FIX activity ≤ 2 IU dL-1 . PK sampling was performed for up to 14 days (336 h). Results Simulation of a single intravenous infusion of rIX-FP (25-75 IU kg-1 ) predicted that the median trough exogenous FIX activity levels would remain > 5 IU dL-1 for up to 16 days in adolescents/adults aged ≥ 12 years, up to 12 days in children aged 6 to < 12 years, and up to 9.5 days in children aged < 6 years. For steady-state dosing, the median trough exogenous FIX activity levels were maintained at > 5 IU dL-1 for the duration of the dosing interval for the 25, 35 and 40 IU kg-1 weekly regimens and for 75 IU kg-1 every 14 days in adolescents/adults, and for the 35 and 40 IU kg-1 weekly regimens in children. Conclusion The population PK model developed here correlates well with observed clinical data and supports prolonged dosing of rIX-FP with intervals of up to 2 weeks.

Advances in the clinical management of inhibitors in hemophilia A and B

Inhibitors to factor (F)VIII or FIX are the most serious and challenging complication of hemophilia treatment, increasing morbidity and mortality because bleeds no longer respond to standard clotting factor replacement therapy. For patients with high-titer inhibitors, immune tolerance induction achieved through regular factor exposure is the only proven therapy capable of Inhibitor eradication and is almost always indicated for inhibitors of recent onset. Bypassing therapy is used to treat and prevent bleeding, but neither of the two currently available bypassing agents has the predictable hemostatic efficacy of factor replacement in hemophilia patients without inhibitors. Major research efforts are focused on the development of new, more potent therapies for the management of patients with inhibitors.

How I use bypassing therapy for prophylaxis in patients with hemophilia A and inhibitors

Inhibitor development poses a significant challenge in the management of hemophilia because once an inhibitor is present, bleeding episodes can no longer be treated with standard clotting factor replacement therapy. Consequently, patients with inhibitors are at increased risk for difficult-to-control bleeding and complications, particularly arthropathy and physical disability. Three clinical trials in patients with inhibitors have demonstrated that prophylaxis with a bypassing agent reduces joint and other types of bleeding and improves health-related quality of life compared with on-demand bypassing therapy. In hemophilia patients without inhibitors, the initiation of prophylaxis with factor (F) VIII or FIX prior to the onset of recurrent hemarthroses can prevent the development of joint disease. Whether this is also true for bypassing agent prophylaxis remains to be determined.

Titrating haemophilia B phenotypes using siRNA strategy: evidence that antithrombotic activity is separated from bleeding liability

Haemophilia A and B are characterised by a life-long bleeding predisposition, and several lines of evidence suggest that risks of atherothrombotic events may also be reduced. Establishing a direct correlation between coagulation factor levels, thrombotic risks and bleeding propensity has long been hampered by an inability to selectively and specifically inhibit coagulation factor levels. Here, the exquisite selectivity of gene silencing combined with a gene knockout (KO) approach was used to define the relative contribution of factor IX (fIX) to thrombosis and primary haemostasis in the rat. Using a lipid nanoparticle (LNP) formulation, we successfully delivered fIX siRNAs to the liver by intravenous administration. The knockdown (KD) of target gene mRNA was achieved rapidly (within 24 hour post-siRNA dosing), sustained (maintained for at least 7 days post dosing) and not associated with changes in mRNA expression levels of other coagulation factors. We found that intermediate levels of liver fIX mRNA silencing (60-95 %) translating into a 50-99 % reduction of plasma fIX activity provided protection from thrombosis without prolonging the cuticle bleeding time. Over 99 % inhibition of fIX activity was required to observe increase in bleeding, a phenotype confirmed in fIX KO rats. These data provide substantial evidence of a participation of fIX in the mechanisms regulating thrombosis prior to those regulating primary haemostasis, therefore highlighting the potential of fIX as a therapeutic target. In addition, hepatic mRNA silencing using LNP-encapsulated siRNAs may represent a promising novel approach for the chronic treatment and prevention of coagulation-dependent thrombotic disorders in humans.

Nonacog gamma, a novel recombinant factor IX with low factor IXa content for treatment and prophylaxis of bleeding episodes

Nonacog gamma is a new recombinant factor IX to treat factor IX deficiency. It is indicated for control of bleeding episodes, perioperative management and routine prophylaxis to prevent or reduce the frequency of bleeding episodes in adults and children with hemophilia B. Nonacog gamma was first approved in the USA in June 2013 under the trade name RIXUBIS followed by market approvals in Australia and the EU in 2014, and marketing authorization decision is pending in Japan. Nonacog gamma is derived from a recombinant Chinese hamster ovary cell line using a state of the art biotechnological manufacturing process. Recombinant factor IX is produced by Baxter's protein-free fermentation technology, which was first developed for ADVATE. The product is purified and formulated in the absence of any human or animal-derived protein. Nonacog gamma was characterized both in comprehensive in vitro and in vivo non-clinical studies as well as in an extensive clinical trial program.

Switching to recombinant factor IX Fc fusion protein prophylaxis results in fewer infusions, decreased factor IX consumption and lower bleeding rates

In the phase 3 B-LONG [Recombinant Factor IX Fc Fusion Protein (rFIXFc) in Subjects with Haemophilia B] study, rFIXFc dosed every 1-2 weeks was safe and efficacious in previously treated subjects with haemophilia B. To date, there are no evaluations of transitioning from conventional to long-acting factor IX (FIX) prophylaxis. This post-hoc analysis of B-LONG subjects compared prophylaxis with other FIX products and rFIXFc. Pre- and on-study data were analysed to assess dosing regimen, weekly FIX consumption and annualized bleeding rates (ABRs). Population pharmacokinetics models were used to generate FIX activity profiles with rFIXFc and recombinant FIX prophylaxis. Thirty-nine subjects, previously treated prophylactically, were evaluated. Prior to study, most subjects (69·2%) received twice-weekly FIX infusions; on study, subjects infused rFIXFc once every 1-2 weeks with c. 30-50% reductions in weekly consumption. On-study estimated mean ABRs were lower than pre-study estimated mean ABRs. Models predicted that rFIXFc administered 50 iu/kg weekly and 100 iu/kg every 10 d would maintain steady-state FIX trough levels ≥1 iu/dl in 95·4% and 89·2% of subjects, respectively. These results indicate that patients receiving rFIXFc prophylaxis can markedly reduce infusion frequency and FIX consumption, have a greater likelihood of maintaining FIX activity >1 iu/dl and experience fewer bleeding episodes compared with prior FIX prophylaxis.

Patient and parent preferences for characteristics of prophylactic treatment in hemophilia

INTRODUCTION

New longer-acting factor products will potentially allow for less frequent infusion in prophylactic treatment of hemophilia. However, the role of administration frequency relative to other treatment attributes in determining preferences for prophylactic hemophilia treatment regimens is not well understood.

AIM

To identify the relative importance of frequency of administration, efficacy, and other treatment characteristics among candidates for prophylactic treatment for hemophilia A and B.

METHOD

An Internet survey was conducted among hemophilia patients and the parents of pediatric hemophilia patients in Australia, Canada, and the US. A monadic conjoint task was included in the survey, which varied frequency of administration (three, two, or one time per week for hemophilia A; twice weekly, weekly, or biweekly for hemophilia B), efficacy (no bleeding or breakthrough bleeding once every 4 months, 6 months, or 12 months), diluent volume (3 mL vs 2.5 mL for hemophilia A; 5 mL vs 3 mL for hemophilia B), vials per infusion (2 vs 1), reconstitution device (assembly required vs not), and manufacturer (established in hemophilia vs not). Respondents were asked their likelihood to switch from their current regimen to the presented treatment. Respondents were told to assume that other aspects of treatment, such as risk of inhibitor development, cost, and method of distribution, would remain the same.

RESULTS

A total of 89 patients and/or parents of children with hemophilia A participated; another 32 were included in the exercise for hemophilia B. Relative importance was 47%, 24%, and 18% for frequency of administration, efficacy, and manufacturer, respectively, in hemophilia A; analogous values were 48%, 26%, and 21% in hemophilia B. The remaining attributes had little impact on preferences.

CONCLUSION

Patients who are candidates for prophylaxis and their caregivers indicate a preference for reduced frequency of administration and high efficacy, but preferences were more sensitive to administration frequency than small changes in annual bleeding rate.

Recombinant factor IX (BAX326) in previously treated paediatric patients with haemophilia B: a prospective clinical trial

A newly developed recombinant factor IX (BAX326(1) ) was investigated for prophylactic use in paediatric patients aged <12 years with severe (FIX level <1%) or moderately severe (FIX level 1-2%) haemophilia B. The aim of this prospective clinical trial was to assess the safety, haemostatic efficacy and pharmacokinetic profile of BAX326 in previously treated paediatric patients. BAX326 was administered as prophylaxis twice a week for a period of 6 months, and on demand for treatment of bleeds. Safety was assessed by the occurrence of related AEs, thrombotic events and immunologic assessments. Efficacy was evaluated by annualized bleeding rate (ABR), and by treatment response rating (excellent, good, fair, none). PK was assessed over 72 h. None of the 23 treated paediatric subjects had treatment-related SAEs or AEs. There were no thrombotic events, inhibitory or specific binding antibodies against FIX, rFurin or CHO protein. Twenty-six bleeds (19 non-joint vs. 7 joint bleeds) occurred (mean ABR 2.7 ± 3.14, median 2.0), of which 23 were injury-related. Twenty subjects (87%) did not experience any bleeds of spontaneous aetiology. Haemostatic efficacy of BAX326 was excellent or good for >96% of bleeds (100% of minor, 88.9% of moderate and 100% of major bleeds); the majority (88.5%) resolved after 1-2 infusions. Longer T1/2 and lower IR were observed in younger children (<6 years) compared to those aged 6 to 12 years. BAX326 administered as prophylactic treatment as well as for controlling bleeds is efficacious and safe in paediatric patients aged <12 years with haemophilia B.

BAX326 (RIXUBIS): a novel recombinant factor IX for the control and prevention of bleeding episodes in adults and children with hemophilia B

Hemophilia B management has improved considerably since the introduction of high-purity plasma-derived factor IX (pdFIX) products in the early 1990s. Recombinant FIX (rFIX) was introduced more recently and has potential safety advantages over the older blood-based products. Until recently, only one such product, nonacog alfa (BeneFIX(®), Pfizer, Inc.), has been available. However, a new rFIX product, BAX326 (RIXUBIS, Baxter Healthcare Corp.), has now been approved by the US Food and Drug Administration. BAX326 undergoes rigorous virus elimination and purification steps during manufacture, and has low activated FIX activity, which confers low thrombogenic potential in humans. Preclinical studies showed promising pharmacokinetic and safety profiles, and these early findings have since been expanded in a series of prospective, multicenter, clinical studies. Foremost among these is a pivotal phase I/III study of BAX326 and its use in routine prophylaxis or on-demand treatment in patients aged 12-65 years with severe (FIX level <1%) or moderately severe (FIX level ≤2%) hemophilia B. This study confirmed the pharmacokinetic equivalence of BAX326 and nonacog alfa, and showed a significant reduction in annualized bleeding rate with BAX326 prophylaxis compared with on-demand treatment (79% versus historic controls; p < 0.001). The hemostatic efficacy of BAX326 was rated as 'excellent' or 'good' in 96% of bleeds. BAX326 was also associated with statistically significant and clinically meaningful improvements in physical health-related quality of life. Results are similarly encouraging in a pediatric study in children aged up to 12 years and in a study in hemophilia B patients undergoing surgery. A further study showed safe transition, with no inhibitor formation in any patient, from treatment with a pdFIX product to BAX326. Overall, the safety profile of BAX326 in clinical trials has been strong, with no inhibitor or specific antibody formation, thrombosis, or treatment-related serious adverse events or anaphylaxis.

The role of Rixubis™ in the treatment of hemophilia B

Hemophilia B is an inherited coagulopathy caused by the partial or complete deficiency of factor (F) IX. Factor replacement therapy, involving the intravenous infusion of plasma-derived or recombinant (r) FIX concentrate, is the cornerstone of treatment, used to control and prevent bleeding episodes. Although several plasma-derived FIX products are available, until recently, only a single rFIX concentrate was on the market. The aim of this paper is to review the pharmacokinetics, hemostatic efficacy, and safety of Rixubis™ (Baxter Healthcare Corporation, CA, USA), a newly licensed rFIX product.

Recombinant factor IX: discrepancies between one-stage clotting and chromogenic assays

New and modified recombinant factor IX (rFIX) products are in development and accurate potency estimation is important to ensure the consistency of production and efficacy of these therapeutics. Collaborative study data obtained during the replacement of the 3rd International Standard (IS) for FIX concentrate suggested that there was a discrepancy between potency estimates for rFIX using clotting and chromogenic methods, when the rFIX candidate was measured against the plasma-derived FIX (pdFIX) IS. This study explores potential chromogenic and one-stage clotting method discrepancies in more detail. Five batches each of rFIX and pdFIX were assayed against the 4th IS FIX concentrate (a pdFIX) by activated partial thromboplastin time (APTT) one-stage clotting assay and specific functional chromogenic assay. The potency of rFIX by chromogenic assay was consistently around 70% of the one-stage clotting potency (average 78 and 108 IU mL(-1) respectively). These differences were not observed with pdFIX, which had similar potencies (average 96 IU mL(-1) ) by each assay method. In addition, different APTT reagents yielded different potency estimates for rFIX when assayed against the pdFIX IS, with a variation of up to 23%. In all cases, the differences were largely resolved when a rFIX reference was used as the standard. This study highlights some of the challenges associated with assay of rFIX products in the laboratory and that careful consideration needs to be given to the choice of reference material used. This is especially important with the imminent arrival of new and modified rFIX products.

Efficacy and safety of a recombinant factor IX (Bax326) in previously treated patients with severe or moderately severe haemophilia B undergoing surgical or other invasive procedures: a prospective, open-label, uncontrolled, multicentre, phase III study

Haemostatic management of haemophilia B patients undergoing surgery is critical to patient safety. The aim of this ongoing prospective trial was to investigate the haemostatic efficacy and safety of a recombinant factor IX (rFIX) (Bax326) in previously treated subjects (12-65 years, without history of FIX inhibitors) with severe or moderately severe haemophilia B, undergoing surgical, dental or other invasive procedures. Haemostatic efficacy was assessed according to a predefined scale. Blood loss was compared to the average and maximum blood loss predicted preoperatively. Haemostatic FIX levels were achieved peri- and postoperatively in 100% of subjects (n = 14). Haemostasis was 'excellent' intraoperatively in all patients and postoperatively in those without a drain, and 'excellent' or 'good' at the time of drain removal and day of discharge in those with a drain employed. Following the initial dose, the mean FIX activity level rose from 6.55% to 107.58% for major surgeries and from 3.60% to 81.4% for minor surgeries. Actual vs. predicted blood loss matched predicted intraoperative blood loss but was equal to or higher than (but less than 150%) the maximum predicted postoperative blood loss reflecting the severity of procedure and FIX requirements. There were no related adverse events, severe allergic reactions or thrombotic events. There was no evidence that BAX326 increased the risk of inhibitor or binding antibody development to FIX. BAX326 was safe and effective for peri-operative management of 14 subjects with severe and moderately severe haemophilia B.

Preclinical safety and efficacy of a new recombinant FIX drug product for treatment of hemophilia B

Baxter has developed a new recombinant factor IX (rFIX) drug product (BAX326) for treating patients with hemophilia B, or congenital FIX deficiency. An extensive preclinical program evaluated the pharmacokinetics, efficacy, and safety of BAX326 in different species. The efficacy of BAX326 was tested in three mouse models of primary pharmacodynamics: tail-tip bleeding, carotid occlusion, and thrombelastography. The pharmacokinetics was evaluated after a single intravenous bolus injection in mice, rats, and macaques. Toxicity was assessed in rats and macaques, safety pharmacology in rabbits and macaques, and immunogenicity in mice. BAX326 was shown to be efficacious in all three primary pharmacodynamic studies (P ≤ 0.0076). Hemostatic efficacy was dose related and similar for the three lots tested. Pharmacokinetic results showed that rFIX activity and rFIX antigen concentrations declined in a bi-phasic manner, similar to a previously licensed rFIX product. BAX326 was well tolerated in rabbits and macaques at all dose levels; no thrombogenic events and no adverse clinical, respiratory, or cardiovascular effects occurred. BAX326 was also shown to have a similar immunogenicity profile to the comparator rFIX product in mice. These results demonstrate that BAX326 has a favorable preclinical safety and efficacy profile, predictive of a comparable effect to that of the previously licensed rFIX in humans.