Benefits of rIX-FP prophylaxis in patients with Haemophilia B: real-world evidence from a Spanish reference centre

Standard FIX prophylaxis for PWHB require frequent injections, which has led to the development of extended half-life products like rIX-FP (albutrepenonacog alfa) that has shown good efficacy in clinical studies. This ambispective study aims to report a real-world experience with rIX-FP in a Spanish centre with PWHB who switched from SHL-FIX or began prophylaxis with rIX-FP. Five PWHB were included in this study, Four PTP switched to rIX-FP with prophylaxis every 7 days whilst one PUP started with an every-14-days regimen. 3 PTPs extended their dosing intervals to every 14 days or every 21 days. In all PTPs, median annualized spontaneous and joint bleeding rates were maintained at 0.00 and median (range) of ABR was 0.92 (0.00-2.77) after switch to rIX-FP. Mean trough level with previous product was 3.68% (SD = 2.06), while it was 7.08% (SD = 3) with all rIX-FP dosing intervals. After switching to rIX-FP, all PTP reduced their annual infusion rate between 50 and 84% and their annual FIX consumption by 61% (59-67%). This is the first reported real-world experience with albutrepenonacog alfa in a small cohort in Spain and demonstrates good bleeding control together with a reduction of the infusion rate, factor consumption and higher through factor level than previous treatment.

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.

External quality assessment for one-stage and chromogenic factor IX assays in samples containing Alprolix (rFIXFc) or Idelvion (rIX-FP) and evidence that UK National External Quality Assessment Scheme for blood coagulation samples are commutable with patient samples

INTRODUCTION

There may be clinically relevant differences between results of different FIX assays in samples containing extended half life FIX concentrates requiring regular surveillance of assay results through proficiency testing exercises. Control materials used in proficiency testing must be commutable, that is have the same inter-assay properties as those demonstrated by authentic clinical samples when measured by different analytical methods.

METHODS

We assessed relationships between results with different FIX assays and commutability of UK National External Quality Assessment Scheme (NEQAS) materials containing rIX-FP (Idelvion) or rFIXFc (Alprolix) by comparing results obtained using widely used one-stage and chromogenic assays during a proficiency testing exercise with results obtained when analysing a series of individual patient samples using the same assay systems. NEQAS samples prepared by addition of either Idelvion or Alprolix to FIX deficient plasma were sent to 76 haemophilia centres in Europe. A total of 18 Idelvion and 22 Alprolix patient samples were assayed in a single centre. Two chromogenic and two one-stage assays were compared.

RESULTS

The pattern of results obtained for NEQAS samples and patient samples was similar. In all cases, the NEQAS sample data point was within the scatter of patient sample data in plots of patient sample results showing one-stage assay results using Synthasil or Actin FS plotted against chromogenic assay results with Biophen or Rox chromogenic FIX kits.

CONCLUSION

This indicates that the NEQAS samples containing Idelvion or Alprolix were commutable and therefore suitable for use in proficiency testing exercises.

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.

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.

Long-term safety and efficacy of rIX-FP prophylaxis with extended dosing intervals up to 21 days in adults/adolescents with hemophilia B

BACKGROUND

An international, multicenter extension study evaluated recombinant fusion protein linking recombinant coagulation factor IX (FIX) with recombinant human albumin (rIX-FP) in hemophilia B (FIX ≤ 2%) patients previously enrolled in a phase III study or who initiated rIX-FP prophylaxis following surgery.

OBJECTIVES

To investigate the long-term safety and efficacy of rIX-FP prophylaxis in adult previously treated patients (PTPs) with hemophilia B.

METHODS

Male PTPs were treated with a 7- (35-50 IU/kg), 10- or 14-day regimen (50-75 IU/kg). Patients ≥18 years who were well-controlled on a 14-day regimen for ≥6 months could switch to a 21-day regimen (100 IU/kg).

RESULTS

A total of 59 patients (aged 13-63 years) participated in the study. Following a single dose of 100 IU/kg rIX-FP, in patients eligible for the 21-day regimen, the mean terminal half-life was 143.2 hours. Mean steady-state FIX trough activity levels ranged from 22% with the 7-day regimen to 7.6% with the 21-day regimen. Median (Q1, Q3) annualized spontaneous bleeding rates were 0.00 (0.00, 1.67), 0.28 (0.00, 1.10), 0.37 (0.00, 1.68), and 0.00 (0.00, 0.45) for the 7-, 10-, 14-, and 21-day regimens, respectively. Comparable efficacy was demonstrated for both the 14- and 21-day regimens compared to the 7-day regimen. Overall, 96.5% of bleeding episodes were treated successfully with 1 to 2 rIX-FP infusions. No patients developed an inhibitor and treatment was well tolerated.

CONCLUSIONS

rIX-FP extended interval prophylaxis provides dosing flexibility and, in selected patients, a 21-day regimen may provide an alternative option to minimize treatment burden and individualize treatment.

Transforming the treatment for hemophilia B patients: update on the clinical development of recombinant fusion protein linking recombinant coagulation factor IX with recombinant albumin (rIX-FP)

Recombinant fusion protein linking recombinant coagulation factor IX with recombinant albumin (rIX-FP; Idelvion®(†)) is an innovative new treatment designed to extend the half-life of factor IX (FIX) and ease the burden of care for hemophilia B patients. The rIX-FP clinical development program - PROLONG-9FP - is in its advanced phases, with pivotal studies in previously treated adults, adolescents, and pediatrics now completed. Across all age groups studied, rIX-FP has demonstrated a markedly improved pharmacokinetic profile compared with plasma-derived and recombinant FIX treatments, with a 30-40% higher incremental recovery, an approximately 5-fold longer half-life, a lower clearance, and a greater area under the curve. rIX-FP has been very well tolerated with an excellent safety profile. In the pivotal studies, there have been no reports of FIX inhibitors or antidrug antibodies, and few treatment-related adverse events have been observed. Prophylactic regimens of rIX-FP administered once weekly to once every 14 days have been highly effective. When used for surgical prophylaxis, a single infusion of rIX-FP has been sufficient to maintain hemostasis, even during major orthopedic surgery. An ongoing study is now enrolling previously untreated patients and evaluating the possibility of extending the dosing interval to every 21 days. There is little doubt that rIX-FP will transform the treatment of hemophilia B.

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

A global phase 3 study evaluated the pharmacokinetics, efficacy and safety of a recombinant fusion protein linking coagulation factor IX with albumin (rIX-FP) in 27 previously treated male children (1–11 years) with severe and moderately severe haemophilia B (factor IX [FIX] activity ≤2 IU/dl). All patients received routine prophylaxis once every seven days for up to 77 weeks, and treated any bleeding episodes on-demand. The mean terminal half-life of rIX-FP was 91.4 hours (h), 4.3-fold longer than previous FIX treatment and clearance was 1.11 ml/h/kg, 6.4-fold slower than previous FIX treatment. The median (Q1, Q3) annualised spontaneous bleeding rate was 0.00 (0.00, 0.91) and was similar between the <6 years and ≥6 years age groups, with a weekly median prophylactic dose of 46 IU/kg. In addition, patients maintained a median trough level of 13.4 IU/dl FIX activity on weekly prophylaxis. Overall, 97.2% of bleeding episodes were successfully treated with one or two injections of rIX-FP (95% CI: 92% to 99%), 88.7% with one injection, and 96% of the treatments were rated effective (excellent or good) by the Investigator. No patient developed FIX inhibitors and no safety concerns were identified. These results indicate that rIX-FP is safe and effective for preventing and treating bleeding episodes in children with haemophilia B with weekly prophylaxis. Routine prophylaxis with rIX-FP at treatment intervals of up to 14 days are currently being investigated in children with severe and moderately severe haemophilia B. Clinicaltrials.gov (NCT01662531)

Emerging drugs for the treatment of hemophilia A and B

INTRODUCTION

Replacement therapy with clotting factor concentrates is the most appropriate and effective way to treat bleedings of Hemophilia A&B to prevent chronic arthropathy. Unfortunately, the short half-life (HL) of FVIII/IX concentrates obliges the patients to receive frequent infusions, a big concern for children. The development of inhibitors in about 30-45% of hemophilia A and in 3-5% of hemophilia B patient is the major adverse event of replacement therapy.

AREAS COVERED

In the last few years, new rFIX have been developed with HL. New rFVIII concentrates are displaying small increase of PK characteristics. The new bio-engineering methods allowed the production of molecules fused with Fc fragment of IgG or Albumin or linked to PEG. A new approach to improve hemostasis is represented by Mab against TFPI and small RNA interfering with Antithrombin synthesis. Another innovative drug seems to be the new bi-specific antibody which mimics FVIII function in linking FXa and FX to tenase production.

EXPERT OPINION

The emerging drugs for hemophilia treatment seem to be very promising. The extended half-life will improve the adherence of patients to therapy. Accurate post-marketing surveillance studies will be necessary to check the efficacy, safety and immunogenicity of these new molecules.