Favorable pharmacokinetics in hemophilia B for nonacog beta pegol versus recombinant factor IX-Fc fusion protein: A randomized trial

Six-Year, Real-World Use of Prophylaxis with Recombinant Factor IX-Albumin Fusion Protein (rIX-FP) in Persons with Hemophilia B: A Single-Center Retrospective-Prospective Study

Background: Extended half-life (EHL) factor IX (FIX) concentrates allow for prophylaxis with prolonged dosing intervals and high bleeding protection in persons with hemophilia B. Long-term real-world studies are lacking. Methods: In a retrospective-prospective study, the six-year use of prophylaxis with the EHL recombinant FIX-albumin fusion protein (rIX-FP) was analyzed, comparing outcomes with previous standard half-life (SHL) FIX in patients already on prophylaxis. Results: Prophylaxis with rIX-FP was prescribed in 15 patients (10 severe, 5 moderate; follow-up: 57 ± 17 months). Based on a pharmacokinetic assessment and clinical needs, the first regimen was 47 ± 7 IU/Kg every 9 ± 2 days. All but one patient remained on rIX-FP prophylaxis, adjusting infusion frequency and/or dose; the last prescribed frequency was ≥10 days in 10/13 patients, being reduced in seven and increased in four vs. the first regimen. The weekly FIX dose was unchanged; FIX trough levels were >5% in all patients. The annual infusion number and FIX IU/Kg significantly decreased (~60%) in eight patients previously on SHL FIX prophylaxis, with similar concentrate costs. Very low bleeding rates (most traumatic bleeds and the last quartile of the infusion interval), improved orthopedic and pain scores, unchanged HEAD-US scores and problem joints, and high treatment adherence (>90%) and satisfaction were registered. Conclusions: Personalized, carefully adjusted rIX-FP regimens contribute to the diffusion and optimization of prophylaxis in persons with severe and moderate hemophilia B, with long-term favorable bleeding, joint, and patient-reported outcomes.

Biodistribution of recombinant factor IX, extended half-life recombinant factor IX Fc fusion protein, and glycoPEGylated recombinant factor IX in hemophilia B mice

Extended half-life recombinant FIX (rFIX) molecules have been generated to reduce the dosing burden and increase the protection of patients with hemophilia B. Clinical pharmacology studies with recombinant factor IX Fc fusion protein (rFIXFc) report a similar initial peak plasma recovery to that of rFIX, but with a larger volume of distribution. Although the pegylation of N9-GP results in a larger plasma recovery, there is a smaller volume of distribution, suggesting less extravasation of the latter drug. In this study, we set out to compare the biodistribution and tissue localization of rFIX, rFIXFc, and glycoPEGylated rFIX in a hemophilia B mouse model. Radiolabeled rFIX, rFIXFc, and rFIX-GP were employed in in vivo single-photon emission computed tomography imaging (SPECT/CT), microautoradiography (MARG), and histology to assess the distribution of FIX reagents over time. Immediately following injection, vascularized tissues demonstrated intense signal irrespective of FIX reagent. rFIX and rFIXFc were retained in joint and muscle areas through 5 half-lives, unlike rFIX-GP (assessed by SPECT). MARG and immunohistochemistry showed FIX agents localized at blood vessels among tissues, including liver, spleen, and kidney. Microautoradiographs, as well as fluorescent-labeled images of knee joint areas, demonstrated retention over time of FIX signal at the trabecular area of bone. Data indicate that rFIXFc is similar to rFIX in that it distributes outside the plasma compartment and is retained in certain tissues over time, while also retained at higher plasma levels. Overall, data suggest that Fc fusion does not impede the extravascular distribution of FIX.

Efficacy of rFIXFc versus N9-GP Prophylaxis in Patients with Hemophilia B: Matching-Adjusted Indirect Comparison of B-LONG and PARADIGM 2 Trials

Purpose

For patients with hemophilia B, extended half-life factor IX (FIX) products are available for prophylaxis and for treating bleeds. Different methods are used to extend the half-lives of recombinant FIX Fc fusion protein (rFIXFc) and nonacog beta pegol (N9-GP). This affects their biodistribution and plasma FIX levels, although differences do not always correlate with clinical outcomes. A matching-adjusted indirect comparison (MAIC) of prophylaxis with rFIXFc and N9-GP was performed, based on licensed dosing in the European Union.

Patients and Methods

Combined rFIXFc data from the weekly and individualized interval prophylaxis arms of the B-LONG clinical trial, and N9-GP data from the 40 IU/kg once-weekly prophylaxis arm of PARADIGM 2 were used in a MAIC. Individual patient data for rFIXFc (n=87) were matched to aggregated data for N9-GP (n=29). Estimated annualized bleeding rates (ABRs) for rFIXFc were recalculated using a Poisson regression model with adjustment for over-dispersion, and compared with ABRs reported for N9-GP, using incidence rate ratios (IRRs) with 95% confidence interval (CI).

Results

There was no evidence of significant differences in estimated ABRs between prophylaxis with rFIXFc and N9-GP. Analysis of pooled rFIXFc weekly and interval-adjusted dosing compared with N9-GP 40 IU/kg once weekly produced estimated ABRs of 2.59 versus 2.51 (IRR 1.03; 95% CI 0.56-1.89), as well as 1.34 versus 1.22 (IRR 1.10; 95% CI 0.42-2.91) and 1.13 versus 1.29 (IRR 0.88; 95% CI 0.47-1.63) for overall, spontaneous, and traumatic bleeding events, respectively.

Conclusion

The study did not reveal any significant differences in the efficacy of rFIXFc and N9-GP prophylaxis. Given differences in trough levels (rFIXFc dosing was targeted to achieve a trough 1-3 IU/dL above baseline versus a reported estimated N9-GP mean trough of 27.3 IU/dL), interpreting plasma FIX levels as potential surrogate efficacy markers requires consideration of compound-specific pharmacokinetic profiles.

Current factor IX replacement options for hemophilia B and the challenges ahead

INTRODUCTION

Therapy for hemophilia B is aimed at replacing the congenital deficiency of coagulation factor IX (FIX). For replacement therapy, several FIX concentrates derived from donated human plasma or engineered by recombinant DNA technology are currently commercially available. The use of these products is well established and permit patients a relatively normal life. To further improve treatment efficacy, recombinant FIX products with a prolonged half-life have been developed, allowing relaxed prophylactic dosing and reducing treatment burden.

AREAS COVERED

In this review, we explore the current FIX replacement options for hemophilia B patients by analyzing the outcomes of their main clinical trials. We cover advances in the FIX molecules with extended half-life (EHL). Published literature on products for replacement of hemophilia B was retrieved using PubMed with no temporal limits.

EXPERT OPINION

The recent introduction of recombinant EHL FIX products has represented a major advance in the therapeutic management of hemophilia B patients, permitting both a reduction of treatment burden and improving patients' compliance to prophylaxis and, ultimately, quality of life.

Regulatory Considerations Toward Orphan Drug Designation and Orphan Drug Exclusivity in the United States and European Union: Structural Similarity, Clinical Superiority/Significant Benefit, and Case Studies

The U.S. Food and Drug Administration and European Commission have developed successful orphan drug legislation to promote the research, development, and marketing approval of drugs to treat rare diseases. Central to these regulations are the concepts of structural similarity and clinical superiority/significant benefit to achieve orphan drug exclusivity. However, differences in health authority expectations remain regarding the qualification for an orphan drug designation, defining structural similarity, and demonstrating clinical superiority/significant benefit. These differences can create sponsor company uncertainty regarding the approvability of products (e.g., blocking risk by an existing orphan product) and divergent orphan drug decisions among health authorities. A comprehensive assessment of current regulations, case studies in exclusivities, and recommendations for improvement are presented.

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, pharmacokinetics, and pharmacodynamics of a next-generation subcutaneously administered coagulation factor IX variant, dalcinonacog alfa, in previously treated hemophilia B patients

BACKGROUND

Dalcinonacog alfa (DalcA), a next-generation, recombinant human factor IX (FIX) variant, was developed using a rational design approach for increased procoagulant activity and longer duration of action to be administered subcutaneously (SC) for prophylaxis of hemophilia B bleeding episodes.

OBJECTIVES

To investigate the safety, pharmacokinetics (PK), and pharmacodynamics (PD) of DalcA.

METHODS

This multicenter, phase 1/2a study (NCT03186677) was conducted in 11 males aged 12 to 65 years with severe hemophilia B. In cohort 1, subjects received intravenous (IV) 75 IU/kg BeneFIX and DalcA. Cohorts 2 and 3 had DalcA IV 75 IU/kg and SC 75 IU/kg or 150 IU/kg. Cohort 4 was omitted. Cohort 5 received daily SC 150 IU/kg DalcA for 6 days and cohort 6 received IV 75 IU/kg and daily SC 150 IU/kg DalcA for 9 days. Blood sampling was performed for chemistry, hematology, PK, PD, and anti-drug antibody measurement. Subjects were monitored for safety endpoints for 30 days postdosing.

RESULTS

DalcA demonstrated a 24-fold greater potency over BeneFIX and longer mean residence time (33.8 h). SC bioavailability 8.2% to 20.3%, beta half-life 53.9 to 106.9 h and Tmax 24 to 48 h. A median 15.7% FIX activity level (interquartile range, 14.9%-16.6%) was reached after 6 daily doses. Neutralizing antibodies to ISU304, but not wild-type FIX, occurred in two cousins.

CONCLUSIONS

The data demonstrated that DalcA achieved protective FIX activity levels between 11% and 18%, corresponding to a reduced chance of spontaneous bleeds. Based on the results, a phase 2b trial to assess the safety and efficacy of 28 daily SC doses of DalcA was performed.

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.

2021 clinical trials update: Innovations in hemophilia therapy

Therapies engineered to prolong clotting factor protein circulation time, manipulate the balance of pro-coagulant and anti-coagulant proteins, or introduce new genetic material to enable endogenous factor protein production dominate the clinical trial landscape of hemophilia. The availability of clotting factor concentrates and the establishment of primary prophylaxis have dramatically improved health outcomes for hemophilia patients. But, the burden of hemostatic therapy remains significant, and many barriers to consistent longitudinal use of prophylaxis exist. Several types of emerging therapeutics including engineered factor concentrates, substitutive therapies, rebalancing therapies, and gene transfer/editing all aim to reduce the challenges of current hemophilia treatment. Emerging treatment options may reduce treatment frequency or need for intravenous administration. They may also introduce new challenges in laboratory assessment of hemostasis. These novel therapies must not introduce significant new health risks and continue to support similar or improved outcomes. The potential ramifications of rebalancing the coagulation cascade, particularly in a stress or inflammatory state, or introduction of new genetic material are not trivial. The focus of this review is to provide an overview of active and recently completed clinical trials as well as emerging preclinical data investigating new therapeutic possibilities for hemophilia patients and potentially other rare bleeding disorders.

Preclinical evaluation of a next-generation, subcutaneously administered, coagulation factor IX variant, dalcinonacog alfa

Introduction

The rapid clearance of factor IX necessitates frequent intravenous administrations to achieve effective prophylaxis for patients with hemophilia B. Subcutaneous administration has historically been limited by low bioavailability and potency. Dalcinonacog alfa was developed using a rational design approach to be a subcutaneously administered, next-generation coagulation prophylactic factor IX therapy.

Aim

This study aimed to investigate the pharmacokinetic, pharmacodynamic, and safety profile of dalcinonacog alfa administered subcutaneously in hemophilia B dogs.

Methods

Two hemophilia B dogs received single-dose daily subcutaneous dalcinonacog alfa injections for six days. Factor IX antigen and activity, whole blood clotting time, and activated partial thromboplastin time were measured at various time points. Additionally, safety assessments for clinical adverse events and evaluations of laboratory test results were conducted.

Results

There was an increase in plasma factor IX antigen with daily subcutaneous dalcinonacog alfa. Bioavailability of subcutaneous dalcinonacog alfa was 10.3% in hemophilia B dogs. Daily subcutaneous dosing of dalcinonacog alfa demonstrated the effects of bioavailability, time to maximal concentration, and half-life by reaching a steady-state activity sufficient to correct severe hemophilia to normal, after four days.

Conclusion

The increased potency of dalcinonacog alfa facilitated the initiation and completion of the Phase 1/2 subcutaneous dosing study in individuals with hemophilia B.

Pharmacokinetics for haemophilia treaters: Meaning of PK parameters, interpretation pitfalls, and use in the clinic

Replacement therapy with concentrates of factor VIII or IX remains the gold standard for severe haemophilia management. The recent development of clotting factor products with extended half-life, widely available on the market since 2 years, facilitates adherence, improves considerably the patients' quality of life, and simplifies the management of breakthrough bleedings or surgery. These molecules have also brought to the limelight the concepts of optimization and personalization of anti-haemophilic prophylaxis. Pharmacokinetics (PK) is one of the tools that can help haematologists to adapt in a more objective and precise manner the prophylaxis regimen to each individual patient's specific needs. For many years, clinicians at haemophilia centres have been using some simple PK parameters, such as recovery and residual level. However, recently, they have been confronted with an important number of new PK parameters they were not familiar with, but that can be used to improve patient management. Due to the accumulation of PK data and their relative complexity, it is now necessary to analyse the relevance of the different PK parameters relative to haemophilia specificities, and also to know their limits to better use them.

Population Pharmacokinetic Modeling Of On-Demand And Surgical Use Of Nonacog Beta Pegol (N9-GP) And rFIXFc Based Upon The paradigm 7 Comparative Pharmacokinetic Study

Aim/objective

Understanding pharmacokinetic (PK) differences between standard and extended half-life (EHL) products is important, particularly for factor IX (FIX), where differences are more significant than for factor VIII. Two single-dose PK trials showed N9-GP achieves higher FIX levels and greater area-under-the-curve than pdFIX, rFIX, and rFIXFc through higher recovery and longer terminal half-life. In paradigm 7, N9-GP demonstrated consistently favorable PK characteristics compared with rFIXFc. Collins et al explored population PK differences between N9-GP and pdFIX/rFIX based upon paradigm 1 data. This analysis uses population PK models based upon the paradigm 7 trial.

Methods

15 patients (21-65 years) with hemophilia B received single 50-IU/kg doses of N9-GP and rFIXFc ≥21 days apart. A population PK model developed from single-dose PK profiles simulated plasma FIX activity following dosing for surgery and on-demand treatment of bleeds. Simulations explored doses and frequencies required to sustain target World Federation of Hemophilia (WFH) factor activity levels.

Results

PK profiles of N9-GP and rFIXFc were described by one- and three-compartment models, respectively. Simulations predicted significantly reduced dosing frequency and consumption for N9-GP than rFIXFc. For severe bleeds, a single N9-GP dose (80 IU/kg) is sufficient to maintain WFH-recommended FIX levels, whereas multiple rFIXFc doses are required. For surgery, redosing in the first week with N9-GP is modeled at day 6 vs rFIXFc dosing at 6, 30, 54, 78, and 126 hrs. For life-threatening bleeds, N9-GP is required at days 0, 3, 6, 13, and 18 vs rFIXFc redosing after 6 hrs with 10 additional doses at 24-, 48-, and 72 hr intervals.

Conclusion

PK modeling approaches based upon direct comparative studies offer insights into PK differences between EHL FIX products. Model simulations show N9-GP may allow on-demand treatment and perioperative management with 55-75% fewer injections and 65-74% lower overall factor concentrate consumption than rFIXFc.