PROTECT VIII Kids: BAY 94-9027 (PEGylated Recombinant Factor VIII) safety and efficacy in previously treated children with severe haemophilia A

A post hoc analysis of PROTECT VIII kids assessing long-term efficacy and safety of damoctocog alfa pegol in adolescents with severe haemophilia A

INTRODUCTION

The safety and efficacy of the extended half-life factor VIII (FVIII) product damoctocog alfa pegol (BAY 94-9027, Jivi®) has been demonstrated in the PROTECT VIII Kids study (NCT01775618), where male previously-treated patients (PTPs) aged <12 years old with severe haemophilia A and ≥ 50 exposure days (EDs) were treated prophylactically. The PROTECT VIII Kids extension study assessed the long-term safety and efficacy of damoctocog alfa pegol in the same population.

AIM

To evaluate the long-term impact of damoctocog alfa pegol in a post hoc subgroup analysis of adolescent patients in the PROTECT VIII Kids study and its extension from 12th birthday onwards.

METHODS

The current analysis included PTPs aged ≥12 years old, who remained in the extension for ≥6 months following their 12th birthday. The observation period was defined as the time from 12th birthday to the end of the extension period; all data from this birthday were included whether in the main study or extension phase. The main efficacy variable was annualised bleeding rate (ABR) and the main safety variable was the frequency of inhibitor development.

RESULTS

This subgroup analysis comprised 25 patients. Median observation time after 12th birthday was 3.2 years. Median total/joint/spontaneous ABRs in the observation period were 1.7/0.7/0.3, respectively. Safety findings were consistent with those reported for the overall study population; no confirmed FVIII inhibitors or anti-drug antibodies were reported.

CONCLUSIONS

Damoctocog alfa pegol is efficacious with a favourable safety profile in adolescents with haemophilia A, supporting its long-term use in children and adolescents.

Pegylation, a Successful Strategy to Address the Storage and Instability Problems of Blood Products: Review 2011-2021

Conjugation of polyethylene glycol (PEGylation) to blood proteins and cells has emerged as a successful approach to address some of the issues attributed to the storage of blood products, including their short half-life and instability. In this regard, this review study aims to compare the influence of different PEGylation strategies on the quality of several blood products like red blood cells (RBCs), platelets, plasma proteins, i.e., albumin, coagulation factor VIII, and antibodies. The results indicated that conjugating succinimidyl carbonate methoxyPEG (SCmPEG) to platelets could improve blood transfusion safety by preventing these cells from being attached to low-load hidden bacteria in blood products. Moreover, coating of 20 kD succinimidyl valerate (SVA)-mPEG to RBCs was able to extend the half-life and stability of these cells during storage, as well as immune camouflage their surface antigens to prevent alloimmunisation. As regards albumin products, PEGylation improved the albumin stability, especially during sterilization, and there was a relationship between the molecular weight (MW) of PEG molecules and the biological half-life of the conjugate. Although coating antibodies with short-chain PEG molecules could enhance their stabilities, these modified proteins were cleared from the blood faster. Also, branched PEG molecules enhanced the retention and shielding of the fragmented and bispecific antibodies. Overall, the results of this literature review indicate that PEGylation can be considered a useful tool for enhancing the stability and storage of blood components.

Cases of less-than-expected FVIII activity in previously treated patients during post-marketing surveillance of N8-GP

INTRODUCTION

Turoctocog alfa pegol (N8-GP) is a glycoPEGylated, extended half-life (EHL), human recombinant factor VIII (FVIII) approved for the treatment and prevention of bleeding episodes in patients with haemophilia A. Since its launch in August 2019, > 800 patients have been treated worldwide.

AIM

To present data from identified post-marketing cases of less-than-expected FVIII activity in previously treated patients (PTPs) without inhibitors after switching to N8-GP.

METHODS

The post-marketing safety database was searched using keywords such as 'coagulation FVIII level decreased'. Identified cases reported prior to 13 October 2021 were included in this report. Cases in which patients had FVIII inhibitors were excluded.

RESULTS

Here we report 14 cases of less-than-expected FVIII activity. Details varied greatly amongst the cases. At presentation, FVIII activity ranged from 1% (15 min post-dose) to 51% (2 days post-dose). Seven patients experienced bleeding episodes after switching to N8-GP with heterogeneity in bleeding presentations. Six out of seven patients who were tested for anti-PEG IgG and/or IgM antibodies were positive. In all known cases, FVIII activity returned to the expected range when switched to an alternative FVIII replacement product.

CONCLUSION

In conclusion, the 14 reported cases of less-than-expected FVIII activity, without presence of detectable FVIII inhibitors, presented with heterogenous characteristics, and wide variations in FVIII activity and anti-PEG antibody titre. FVIII activity returned to the expected range after switching to alternative FVIII products. In line with WFH guidelines, monitoring of FVIII activity can ensure FVIII activity in the expected range. The safety surveillance of N8-GP continues.

Report on 4 cases with decreased recovery due to neutralizing antibodies specific for PEGylated recombinant factor VIII

BACKGROUND

The immunogenicity, safety, and efficacy of recombinant factor VIII (rFVIII) have gained increasing interest after the introduction of extended half-life products with various modifications of the rFVIII molecule, such as covalent attachment of polyethylene glycol (PEG). Anti-PEG antibodies may be associated with a temporary reduction of FVIII recovery, but according to previous studies, they usually disappear after continuous dosing. Anti-PEG antibodies with an inhibitory capacity have never been demonstrated in patients treated with PEGylated rFVIII products.

OBJECTIVES

To routinely switch from standard half-life to PEGylated extended half-life rFVIII products in patients with hemophilia A.

METHODS

From December 2022 until May 2023, 83 adults with hemophilia A attending Oslo Haemophilia Comprehensive Care Centre received a test dose with a PEGylated rFVIII product to switch treatment. Four patients presented with decreased recovery without the presence of an FVIII inhibitor. Accordingly, we performed a variant inhibitor test utilizing different rFVIII concentrates as a source of FVIII and enzyme-linked immunosorbent assay to search for anti-PEG antibodies.

RESULTS

We found inhibitory anti-PEG/anti-PEGylated rFVIII antibodies in 4 patients (5%), both persistent and transient, explaining the impaired recovery. The patients had neutralizing anti-PEG antibodies prior to the first dosing of PEGylated rFVIII. We demonstrated neutralizing antibodies (mainly immunoglobuline G) specific for PEG and all 3 commercially available PEGylated rFVIII products.

CONCLUSION

The number of patients with inhibitory anti-PEG antibodies was significant, and the presence of inhibitors against PEGylated rFVIII emphasizes the importance of individual monitoring when switching FVIII concentrates to ensure safety and efficacy of the treatment.

Immunogenicity of Therapeutic Biological Modalities - Lessons from Hemophilia A Therapies

The introduction and development of biologics such as therapeutic proteins, gene-, and cell-based therapy have revolutionized the scope of treatment for many diseases. However, a significant portion of the patients develop unwanted immune reactions against these novel biological modalities, referred to as immunogenicity, and no longer benefit from the treatments. In the current review, using Hemophilia A (HA) therapy as an example, we will discuss the immunogenicity issue of multiple biological modalities. Currently, the number of therapeutic modalities that are approved or recently explored to treat HA, a hereditary bleeding disorder, is increasing rapidly. These include, but are not limited to, recombinant factor VIII proteins, PEGylated FVIII, FVIII Fc fusion protein, bispecific monoclonal antibodies, gene replacement therapy, gene editing therapy, and cell-based therapy. They offer the patients a broader range of more advanced and effective treatment options, yet immunogenicity remains the most critical complication in the management of this disorder. Recent advances in strategies to manage and mitigate immunogenicity will also be reviewed.

Longitudinal observations of TFPI levels in paediatric Haemophilia A patients

INTRODUCTION

Inhibition of tissue factor pathway inhibitor (TFPI) is a potential new mode of action to achieve haemostasis in haemophilia A and B patients.

AIM

Knowledge about potential developmental changes of TFPI levels during childhood are a prerequisite to translate adult doses of TFPI inhibitors to doses in paediatric patients.

METHODS

In this study we present longitudinal data for total TFPI concentrations (TFPI-T) and TFPI activity (TFPI-A) from 48 paediatric Haemophilia A patients in the age range from 3 to 18 years (2-12 observations per patient).

RESULTS

TFPI-T and TFPI-A tend to decrease over age during childhood. Lowest values were observed between 12 and <18 years. On average, TFPI-T and TFPI-A were lower in adolescent haemophilia patients than in adult haemophilia patients.

CONCLUSION

In summary, the presented information on TFPI levels in children adds to the current knowledge of developmental haemostasis and it can be helpful in evaluating how children respond to haemophilia treatment including the new class of anti-TFPI compounds.

Immunogenicity of Current and New Therapies for Hemophilia A

Anti-drug antibody (ADA) development is a significant complication in the treatment of several conditions. For decades, the mainstay of hemophilia A treatment was the replacement of deficient coagulation factor VIII (FVIII) to restore hemostasis, control, and prevent bleeding events. Recently, new products have emerged for hemophilia A replacement therapy, including bioengineered FVIII molecules with enhanced pharmacokinetic profiles: the extended half-life (EHL) recombinant FVIII products. However, the main complication resulting from replacement treatment in hemophilia A is the development of anti-FVIII neutralizing alloantibodies, known as inhibitors, affecting approximately 25–30% of severe hemophilia A patients. Therefore, the immunogenicity of each FVIII product and the mechanisms that could help increase the tolerance to these products have become important research topics in hemophilia A. Furthermore, patients with inhibitors continue to require effective treatment for breakthrough bleedings and procedures, despite the availability of non-replacement therapy, such as emicizumab. Herein, we discuss the currently licensed treatments available for hemophilia A and the immunogenicity of new therapies, such as EHL-rFVIII products, compared to other products available.

The safety and efficacy of N8-GP (turoctocog alfa pegol) in previously untreated pediatric patients with hemophilia A

N8-GP (turoctocog alfa pegol) is a recombinant, glycoPEGylated, extended half-life, factor VIII replacement product. Here, we examined the immunogenicity, safety, and efficacy of N8-GP in previously untreated patients (PUPs). pathfinder6 is an ongoing, open-label, phase 3 trial that enrolled PUPs with severe hemophilia A and were aged <6 years. The primary end point was the incidence of factor VIII inhibitors (≥0.6 Bethesda units [BU]). Eighty patients received ≥1 N8-GP dose and were included in this analysis; ≥50 patients had ≥50 exposure days to N8-GP. The inhibitor incidence was 29.9% (14.9% high-titer [>5 BU]). Sixty-five patients received N8-GP prophylaxis for an average of 2.17 years with a median annualized bleeding rate (interquartile range) of 1.42 (0.76; 3.13) and a 90.5% hemostatic success rate. Temporarily decreased incremental recovery (IR), defined as ≥2 consecutive measurements of IR <0.6 (IU/dL)/(IU/kg) but no inhibitors, was observed in 17 patients within 5 exposure days to N8-GP and had a strong temporal correlation with anti-polyethylene glycol immunoglobulin G antibody titers. IR returned within the expected range with continued N8-GP dosing. During the period of decreased IR, hemostatic response was similar to that of the overall trial population, and no hypersensitivity related to N8-GP or unexpected new adverse events were reported. N8-GP prophylaxis was efficacious for the prevention and treatment of bleeding episodes in PUPs with severe hemophilia A. The inhibitor incidence was 29.9%. All patients with temporarily decreased IR continuing on N8-GP dosing returned within the expected range and had no evident lack of efficacy. This trial was registered at www.clinicaltrials.gov as #NCT02137850.

An Update on Laboratory Diagnostics in Haemophilia A and B

Haemophilia A (HA) and B (HB) are X-linked hereditary bleeding disorders caused by lack of activity of coagulation factors VIII (FVIII) or IX (FIX), respectively. Besides conventional products, modern replacement therapies include FVIII or FIX concentrates with an extended half-life (EHL-FVIII/FIX). Two main strategies for measuring plasma FVIII or FIX activity are applied: the one-stage clotting assay (OSCA) and the chromogenic substrate assay (CSA), both calibrated against plasma (FVIII/FIX) standards. Due to the structural modifications of EHL-FVIII/FIX, reagent-dependent assay discrepancies have been described when measuring the activity of these molecules. Assay discrepancies have also been observed in FVIII/FIX gene therapy approaches. On the other hand, nonfactor replacement by the bispecific antibody emicizumab, a FVIIIa-mimicking molecule, artificially shortens activated partial thromboplastin time–based clotting times, making standard OSCAs inapplicable for analysis of samples from patients treated with this drug. In this review, we aim to give an overview on both, the currently applied and future therapies in HA and HB with or without inhibitors and corresponding test systems suitable for accompanying diagnostics.

PEGylated Recombinant Human Growth Hormone Jintrolong® Exhibits Good Long-Term Safety in Cynomolgus Monkeys and Human Pediatric Growth Hormone Deficiency Patients

Jintrolong^® is a long-acting PEGylated recombinant human growth hormone (PEG-rhGH) developed for weekly injection in patients with pediatric growth hormone deficiency (PGHD). Although PEG modification of therapeutic proteins is generally considered safe, concerns persist about the potential for adverse vacuolation in tissues with long-term exposure to PEG-included therapies, particularly in children. We assessed the safety of Jintrolong^® in cynomolgus monkeys with an examination of vacuolation in the brain choroid plexus (CP) and reported long-term clinical safety data obtained from children with PGHD. The toxicity of Jintrolong^® was assessed following the 52-week administration with doses at 0.3, 1, or 3 mg/kg/week. The levels of vacuolation of CP in animals were dose-dependent and at least partially reversible after a 104- or 157-week recovery period. Vacuolation in the CP epithelium did not lead to obvious subcellular structural or cell functional abnormalities. Compared with the clinical dose of 0.2 mg/kg/week Jintrolong^® in PGHD patients, exposure in monkeys under NOAEL 3 mg/kg/week exhibited safety margins greater than 120.5, the predicted minimum dose to induce vacuolation in monkeys is equivalent to 1.29 mg/kg/week in humans, which is 6.45-fold higher than the clinical dose. The safety data acquired in clinical trials for Jintrolong^® were also analyzed, which included phase III (360 patients), phase IV (3,000 patients) of 26-week treatment, and a follow-up study with treatment lasting for 3 years. There was no statistically significant difference in the incidence of adverse reactions between the Jintrolong^® group and the daily rhGH control group (no PEG), and no new adverse effects (AE) were observed in the Jintrolong^® group at the clinical therapeutic dose of 0.2 mg/kg/week.

Advances in the management of haemophilia: emerging treatments and their mechanisms

Mainstay haemophilia treatment, namely intravenous factor replacement, poses several clinical challenges including frequent injections due to the short half-life of recombinant factors, intravenous administration (which is particularly challenging in those with difficult venous access), and the risk of inhibitor development. These impact negatively upon quality of life and treatment compliance, highlighting the need for improved therapies. Several novel pharmacological therapies developed for haemophilia aim to rebalance the clotting cascade and potentially circumvent the aforementioned challenges. These therapies utilise a range of different mechanisms, namely: the extension of the circulating half-life of standard recombinant factors; the mimicking of factor VIII cofactor activity; rebalancing of coagulation through targeting of natural anticoagulants such as antithrombin and tissue factor pathway inhibitor; and inducing the production of endogenous factors with gene therapy. These therapies carry the potential of revolutionising haemophilia treatment by alleviating the current challenges presented by mainstay factor replacement. This review will provide an overview of the key trial findings related to novel therapies based on the mechanisms described above.

The Role of Physiotherapy in the New Treatment Landscape for Haemophilia

The physiotherapist plays an essential role for people with haemophilia, an inherited bleeding disease responsible for musculoskeletal complications. Yet, with the advent of new and advanced therapies, the medical landscape is changing, and physiotherapy must adapt alongside. This paper considers whether there will still be a need for physiotherapy in the era of advanced therapies, and discusses ways in which services should evolve to complement emerging treatment paradigms for haemostasis in people with haemophilia. Ultimately, physiotherapy will remain an important element of care, even for people with little joint damage and low risks in the era of the new mild phenotype. However, competencies will need to evolve, and physiotherapists in both primary care and specialist treatment centres should work with haematology colleagues to develop more sensitive tools for detecting early joint changes. Physiotherapists will also play a crucial role in counselling and physically coaching, monitoring the musculoskeletal status of people with haemophilia who have transitioned to new treatments.

PROTECT VIII kids extension study: Long-term safety and efficacy of BAY 94-9027 (damoctocog alfa pegol) in children with severe haemophilia A

Introduction

BAY 94‐9027 (damoctocog alfa pegol; an extended half‐life PEGylated recombinant factor VIII [FVIII]) demonstrated efficacy and safety in previously treated paediatric patients (PTPs) aged <12 years with severe haemophilia A in the PROTECT VIII Kids study (NCT01775618).

Aim

To evaluate the long‐term safety of BAY 94‐9027 in PTPs aged <12 years at enrolment.

Methods

In the PROTECT VIII Kids study, boys <12 years with severe haemophilia A were enrolled in two age cohorts (6–<12 years and <6 years) and treated prophylactically twice weekly, every 5 days or every 7 days, with BAY 94‐9027 for ≥50 exposure days (EDs). Patients who had completed ≥50 EDs and ≥6 months in the main study or 12‐week safety expansion study were eligible to participate in the extension. Primary safety variable was frequency of inhibitor development; main efficacy variable was annualised bleeding rate (ABR).

Results

Of 73 PTPs from the main/expansion studies, 59 (81%) entered the extension phase for a median (range) duration of 5.0 (0.4–5.9) years. Overall, 39 patients completed ≥5 years of treatment. No patients developed FVIII inhibitors/anti‐PEG antibodies, and two patients aged <6 years discontinued. Median ABR for total bleeds was 1.5 (<6 years) and 1.9 (6–<12 years). Total ABR improved in the extension vs. the main study. In the last 12 months of treatment, median spontaneous ABR was 0.0 in both age groups.

Conclusions

BAY 94‐9027 showed long‐term safety and efficacy for the prevention and treatment of bleeds in younger and older paediatric patients with severe haemophilia A.

Recombinant FVIIIFc Versus BAY 94-9027 for Treatment of Patients with Haemophilia A: Comparative Efficacy Using a Matching Adjusted Indirect Comparison

Introduction

Prophylaxis with recombinant factor VIII (rFVIII) is the current standard of care for haemophilia A. Several approaches have been used to extend the half-life of rFVIII to improve prophylaxis outcomes. An indirect comparison of pivotal clinical trial data was performed to evaluate the relative efficacy of two extended half-life therapies approved for the prophylactic treatment of haemophilia A: recombinant FVIII–IgG₁ Fc domain fusion protein (rFVIIIFc) and pegylated rFVIII (BAY 94-9027).

Methods

Matching-adjusted indirect comparison (MAIC) was conducted to compare the rFVIIIFc individualised prophylaxis arm of the A-LONG phase III clinical trial (n = 117) and the BAY 94-9027 approved dosing regimens of the PROTECT VIII phase II/III study (n = 110). Following matching for baseline characteristics, mean annualised bleeding rate (ABR) and the proportion of patients with zero bleeds were compared for rFVIIIFc and BAY 94-9027. Additional supportive analyses comparing rFVIIIFc individualised prophylaxis and the individual prophylaxis regimens included in the PROTECT VIII group (twice weekly, and every 5 and 7 days [Q5D and Q7D]) were conducted.

Results

Mean ABR was lower in the rFVIIIFc individualised prophylaxis group versus the BAY 94-9027 pooled prophylaxis population (3.0 versus 4.9), providing a clinically relevant and statistically significant difference (mean difference [MD] − 1.9; 95% confidence interval [CI] − 3.5 to − 0.4). A statistically significant difference in ABR was also observed for rFVIIIFc compared with BAY 94-9027 Q7D (3.2 versus 6.4; MD − 3.3; 95% CI − 6.4 to − 0.2). The difference in the proportion of patients with zero bleeds between rFVIIIFc (46.5%) and BAY 94-9027 pooled prophylaxis population (38.2%) was not statistically significant (odds ratio 1.4; 95% CI 0.8 to 2.5).

Conclusions

This indirect treatment comparison indicates a statistically significant and clinically relevant difference in ABR favouring individualised prophylaxis with rFVIIIFc versus BAY 94-9027 prophylaxis. The proportion of patients with zero bleeds was numerically greater with rFVIIIFc treatment but did not achieve statistical significance.

PROTECT VIII Kids: BAY 94-9027 (PEGylated Recombinant Factor VIII) safety and efficacy in previously treated children with severe haemophilia A

INTRODUCTION

BAY 94-9027, a site-specifically PEGylated, B-domain-deleted recombinant factor VIII (FVIII) with extended half-life, demonstrated efficacy for bleed prevention and treatment in previously treated adolescents and adults with severe haemophilia A.

AIM

To assess BAY 94-9027 in children with severe haemophilia A.

METHODS

In the two-part PROTECT VIII Kids study, boys <12 years with <1% FVIII and >50 exposure days (EDs) to FVIII were enrolled in two cohorts (<6 years; 6-<12 years) and treated with BAY 94-9027 prophylaxis twice-weekly, every 5 days, or every 7 days at physician discretion for ≥50 EDs (Part 1) or twice-weekly for 12-weeks (Part 2). Annualized bleeding rate (ABR) was a primary efficacy endpoint; FVIII inhibitor development was the primary safety variable.

RESULTS

At study completion, 25 patients had been treated twice-weekly, 28 in the every-5-day group, and 8 in the every-7-day group. Median ABR for all bleeds was 2.9 (Part 1) and 2.4 (Part 2) and similar in younger and older patients; median ABR for joint bleeds was 0 for both cohorts. In the last 90 days' treatment, median ABR was 0 for younger and older patients (Part 1). Of 149 reported bleeds, 93% were treated with ≤2 infusions. Twelve patients, the majority <6 years (n = 11), discontinued due to apparent loss of efficacy or hypersensitivity. No FVIII inhibitors developed.

CONCLUSIONS

In PROTECT VIII Kids, which allowed tailoring of prophylaxis to individual clinical response, BAY 94-9027 was efficacious for bleed prevention and treatment in previously treated children with severe haemophilia A.