Evaluation of Nonacog Beta Pegol Long-term Safety in the Immune-deficient Rowett Nude Rat (Crl:NIH-Foxn1rnu)

Normal Neurodevelopment and Fertility in Juvenile Male Rats Exposed to Polyethylene Glycol Following Dosing With PEGylated rFIX (Nonacog Beta Pegol, N9-GP): Evidence from a 10-Week Repeat-Dose Toxicity Study

N9-GP/Rebinyn®/Refixia® is an approved PEGylated (polyethylene glycol-conjugated) recombinant human factor IX intended for prophylactic and/or on-demand treatment in adults and children with haemophilia B. A juvenile neurotoxicity study was conducted in male rats to evaluate effects on neurodevelopment, sexual maturation, and fertility following repeat-dosing of N9-GP. Male rats were dosed twice weekly from Day 21 of age with N9-GP or vehicle for 10 weeks, followed by a dosing-free recovery period for 13 weeks and terminated throughout the dosing and recovery periods. Overall, dosing N9-GP to juvenile rats did not result in any functional or pathological effects, as measured by neurobehavioural/neurocognitive tests, including motor activity, sensory function, learning and memory as well as growth, sexual maturation, and fertility. This was further supported by the extensive histopathologic evaluation of brain tissue. Exposure and distribution of polyethylene glycol was investigated in plasma, choroid plexus, cerebrospinal fluid, and brain sections. PEG did not cross the blood brain barrier and PEG exposure did not result in any effects on neurodevelopment. In conclusion, dosing of N9-GP to juvenile rats did not identify any effects on growth, sexual maturation and fertility, clinical and histological pathology, or neurodevelopment related to PEG exposure and supports the prophylactic use of N9-GP in children.

Polyethylene glycol 20 kDa-induced vacuolation does not impair phagocytic function of human monocyte-derived macrophages

Conjugation to polyethylene glycol (PEG) is commonly used to enhance drug delivery and efficacy by extending the half-life of the drug molecule. This has important implications for reducing treatment burden in diseases that require chronic prophylaxis, such as hemophilia. Clearance of PEG molecules with high molecular weights (≥ 40 kDa) has been reported to cause cellular vacuolation in mammals. Rurioctocog alfa pegol (PEGylated recombinant coagulation factor VIII) contains a 20-kDa PEG. This study investigated the effects of exposure to 20-kDa PEG (10 μg/ml to 10 mg/ml) on the morphology and function of human monocyte-derived macrophages (MDMs) in vitro. Exposure to PEG for 24 hours was associated with significant vacuolation only at concentrations of 1 mg/ml or more, which far exceed the levels associated with clinically relevant doses of rurioctocog alfa pegol. Immunofluorescence staining of PEG was detected in the cytoplasm of MDMs, indicating uptake into the cells. No impairment of MDM phagocytic activity (ability to ingest fluorescently labeled Escherichia coli) was observed with 24-hour exposure to PEG, even at concentrations associated with significant vacuolation. Furthermore, PEG exposure did not have significant effects on cytokine secretion in resting or lipopolysaccharide-stimulated MDMs, or on the expression of cell surface markers in stimulated MDMs. Cell viability was not affected by 24-hour exposure to PEG. In conclusion, vacuolation of human MDMs after exposure to 20-kDa PEG only occurred with PEG concentrations far in excess of those equivalent to clinically relevant doses of rurioctocog alfa pegol and did not affect MDM viability or functionality. Together, these results support the concept that PEG-mediated vacuolation is an adaptive cellular response rather than a toxic effect.

CTLA4-Ig prevents development of neutralizing antibody formation after continuous treatment with human FVIII in HA rats

INTRODUCTION

Immunogenicity causing development of anti-drug antibodies (ADAs) are major challenges in the treatment of haemophilia, as well as other diseases where proteins are used for treatment. Furthermore, it is a complication for preclinical testing of such therapies in animal models.

AIM

To investigate if the immunosuppressive drug CTLA4 immunoglobulin (CTLA4-Ig) can induce tolerance in haemophilia A (HA) rats receiving recombinant human coagulation factor VIII (rhFVIII) treatment.

METHODS

Two different prophylactic rhFVIII compounds were given intravenously to HA rats for 4 weeks. Both rhFVIII compounds were co-administered with commercially available CTLA4-Ig or human IgG subclass 4 (hIgG4) as control, and blood samples were collected. To functionally test if pharmacological efficacy was retained, rats were subjected to a bleeding experiment under anaesthesia at end of study.

RESULTS

The mean inhibitory level after 4 weeks in rats receiving rhFVIII and hIgG4 was 85.7 BU for octocog alfa and 37.4 BU for rurioctocog alfa pegol. In contrast, co-administration with CTLA4-Ig during rhFVIII therapy prevented the formation of ADAs (both binding and inhibitory) in 14/14 rats receiving octocog alfa and in 7/7 rats receiving rurioctocog alfa pegol. Moreover, we were able to show that the pharmacological efficacy of rhFVIII was preserved.

CONCLUSION

In a rat model with spontaneous bleeding, co-administration of CTLA4-Ig with rhFVIII prevented antibody formation. No FVIII antibodies were detected, demonstrating that CTLA4-Ig co-administration can be applicable as a method to prevent immunogenicity, when evaluating human proteins in preclinical systems permitting continuous pharmacokinetic and pharmacodynamic assessment.

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

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

Steady-State Plasma Concentrations of Polyethylene Glycol (PEG) are Reached in Children and Adults During Once-Weekly Prophylactic Treatment with Nonacog Beta Pegol (N9-GP)

Background

Nonacog beta pegol (N9-GP, Refixia^®, Rebinyn^®) is a human recombinant coagulation factor IX (rFIX) conjugated to a 40-kDa polyethylene glycol (PEG) moiety. PEGylation significantly prolongs the circulation half-life compared with conventional FIX replacement treatments, resulting in higher FIX levels. Although there is extensive clinical experience with PEGylated molecules, the potential for abnormal and/or indefinite PEG accumulation during long-term treatment and the hypothetical impact on long-term safety is still under discussion.

Aim

The aim of this study was to examine plasma PEG concentrations in children, adolescents and adults undergoing once-weekly intravenous prophylactic treatment with N9-GP for up to 6.5 years.

Methods

Plasma samples were collected as part of the PARADIGM clinical development programme (PARADIGM 2/4 [NCT01333111 and NCT01395810] and PARADIGM 5 [NCT01467427]). Proton nuclear magnetic resonance (¹H-NMR) was used to measure plasma PEG concentrations.

Results

Steady-state plasma PEG concentrations were reached approximately 6 months after initiation of weekly prophylactic treatment with 40 IU/kg N9-GP. Mean steady-state plasma PEG concentrations were 5.6 μg/mL in children ≤ 12 years old at enrolment (PARADIGM 5) and 5.3 μg/mL in adolescents/adults > 12 years old (PARADIGM 2/4). Plasma PEG concentrations tended to be lower in younger children < 7 years old (mean 4.6 μg/mL). There was a correlation between plasma PEG and FIX activity levels in all age groups.

Conclusion

PEG steady-state plasma levels were maintained for up to 6.5 years during continuous prophylactic treatment and PEG levels correlated with FIX activity. Apart from the initial increase to steady state, no further systemic PEG accumulation was observed.

Nonclinical Safety Assessment of a Long-Acting Recombinant PEGylated Factor Eight (BAY 94-9027) With a 60 kDa PEG

BAY 94-9027 (Jivi) is a site-specifically PEGylated human B-domain-deleted (BDD) recombinant factor VIII (FVIII), with a 60 kDa branched PEG molecule attached. The nonclinical safety of BAY 94-9027 was evaluated in a toxicology program that included 2 weeks intravenous (IV) toxicity studies in rats and rabbits, a juvenile toxicity study in rats as well as a 26-week chronic study in rats. Doses of 75, 750, or 2250 IU/kg given every other day for 2 weeks did not elicit any findings related to BAY 94-9027. Specifically, no thrombus formation or histological changes such as cellular vacuolation were seen. In the chronic toxicity study, 40, 400, and 1200 IU/kg of BAY 94-9027 given twice weekly did not induce adverse effects related to BAY 94-9027, and no tissue vacuolation was observed. There was no PEG detected in choroid plexus or other areas of the brain, cerebrospinal fluid or in spleen or kidneys. These results were supported by toxicity studies in rats and rabbits treated with PEG 60 kDa attached to the maleimide linker (PEG-60-Mal-Cys). No findings related to PEG-60-Mal-Cys were seen. These results demonstrate the safety of BAY 94-9027 for long-term use.

GlycoPEGylated recombinant factor IX for hemophilia B in context

Decisions over hemophilia treatment selection and switching involve balancing many clinical and patient-related factors. The current standard of care for patients with hemophilia B is prophylaxis with plasma-derived or recombinant factor IX (rFIX) concentrates. However, several extended half-life (EHL) rFIX products have recently been developed to improve treatment convenience and clinical outcomes for these patients. Nonacog beta pegol, an rFIX product that combines the FIX protein with a 40 kDa polyethylene glycol moiety, has been evaluated in 115 previously treated patients with hemophilia B (including 25 children) in the paradigm clinical trial program. FIX activity levels and pharmacokinetics were monitored throughout these trials and showed that nonacog beta pegol offers significant pharmacological improvements over standard FIX products. Once-weekly prophylaxis with nonacog beta pegol 40 IU/kg resulted in fewer bleeds in all patients (median annualized bleeding rate of 1.0 across all ages), resolved 90% of target joints, and improved health-related quality of life. No patients developed FIX inhibitors, and there were no thromboembolic events or unexpected safety concerns. Nonacog beta pegol was also safe and effective in the perioperative setting. These findings show that nonacog beta pegol is highly effective, while also offering more convenient dosing than standard FIX products. Nonacog beta pegol represents a significant advance in the current context of treatment for hemophilia B, offering effective management across several treatment modalities and settings, and potentially easing the treatment burden for patients of all ages. Meanwhile, the development of novel treatment strategies, such as gene therapy, anti-tissue factor pathway inhibitor antibodies, and RNA interference therapy, may provide patients with additional therapeutic options, which would require reassessment of the role of EHL products in the future.

Practical aspects of extended half-life products for the treatment of haemophilia

Haemophilia A and haemophilia B are congenital X-linked bleeding disorders caused by deficiency of coagulation factor VIII (FVIII) and IX (FIX), respectively. The preferred treatment option for patients with haemophilia is replacement therapy. For patients with severe disease, prophylactic replacement of coagulation factor is the treatment of choice; this has been shown to reduce arthropathy significantly, reduce the frequency of bleeds and improve patients' quality of life. Prophylaxis with standard recombinant factor requires regular intravenous infusion at least two (FIX) to three (FVIII) times a week. Recombinant FVIII and FIX products with an extended half-life are in development, or have been recently licensed. With reported mean half-life extensions of 1.5-1.8 times that of standard products for FVIII and 3-5 times that of standard products for FIX, these products have the potential to address many of the unmet needs of patients currently treated with standard factor concentrates. For example, they may encourage patients to switch from on-demand treatment to prophylaxis and improve the quality of life of patients receiving prophylaxis. Indeed, extended half-life products have the potential to reduce the burden of frequent intravenous injections, reducing the need for central venous lines in children, promote adherence, improve outcomes, potentially allow for more active lifestyles and, depending on the dosing regimen, increase factor trough levels. Members of the Zürich Haemophilia Forum convened for their 19th meeting to discuss the practicalities of incorporating new treatments into the management of people with haemophilia. This review of extended half-life products considers their introduction in haemophilia treatment, including the appropriate dose and schedule of infusions, laboratory monitoring, patient selection, safety considerations, and the economic aspects of care.

Scientific and Regulatory Policy Committee Points to Consider: Histopathologic Evaluation in Safety Assessment Studies for PEGylated Pharmaceutical Products

Colorless, intracytoplasmic vacuoles occur in multiple tissues in animals following repeated administration of polyethylene glycol (PEG)-conjugated molecules. The extent of vacuolation depends on physical characteristics and molecular backbone of the PEG and the dose, product, drug target/pharmacology, and duration of exposure. The collective experience gathered from multiple nonclinical toxicology studies of PEGylated biopharmaceuticals indicates that in general, PEG-related vacuolation is not associated with demonstrable cell and tissue damage or dysfunction and is reversible with sufficient duration of drug-free periods. Existing data are insufficient to predict whether nonclinical animal species differ in their sensitivity to develop PEG-associated vacuoles; however, recent data suggest that there may be species differences. Recent comprehensive reviews have addressed the basic challenges in developing PEGylated pharmaceutical products, including general reference to and description of PEG-associated tissue findings. These manuscripts have identified gaps in our current understanding of PEG-associated vacuolation, including the lack of a widely accepted standardized histological terminology and criteria to record and grade the severity of vacuolation as well as insufficient knowledge regarding the nature of the contents of these vacuoles. The goal of this article is to help address some of the gaps identified above by providing points to consider, including a pictorial review of PEG-associated microscopic findings, when evaluating and reporting the extent, severity, and significance (adversity or lack of adversity) of PEG-associated cytoplasmic vacuolation in safety assessment studies.

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Polyethylene Glycol Exposure with Antihemophilic Factor (Recombinant), PEGylated (rurioctocog alfa pegol) and Other Therapies Indicated for the Pediatric Population: History and Safety

Polyethylene glycol (PEG) is an inert, water soluble polymer, used for decades in pharmaceuticals. Although PEG is considered safe, concerns persist about the potential adverse effects of long-term exposure to PEG-containing therapies, specifically in children, following the introduction of PEGylated recombinant factor products used for the treatment of hemophilia. Given the absence of long-term surveillance data, and to evaluate the potential risk, we estimated PEG exposure in the pediatric population receiving PEGylated therapies with pediatric indications administered intravenously or intramuscularly. We used a range of pediatric weights and doses based on prescribing information (PI) or treatment guidelines. PIs and reporting websites were searched for information about adverse events (AEs). For a child weighing 50 kg on the highest prophylactic dose of a FVIII product, the range of total PEG exposure was 40–21,840 mg/year; for factor IX (FIX) products, the range was 13–1342 mg/year; and for other products, the range was 383–26,743 mg/year, primarily as a derivative excipient. No AE patterns attributable to PEG were found for any of these products, including potential renal, neurological, or hepatic AEs. Our analyses suggest the pediatric population has had substantial exposure to PEG for several decades, with no evidence of adverse consequences.

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.

Magnetic Resonance and Ultrastructural Characterization of PEGylation-associated Vacuolation in Nonclinical Models

Conjugation with polyethylene glycol (PEG) is a strategy for improving the pharmaceutical properties of therapeutic proteins. In nonclinical studies of PEGylated compounds, microscopic tissue vacuolation is often observed, characterized ultrastructurally in this report by lysosomal distension. Although PEGylation-associated vacuolation appears to be of limited toxicologic concern when alternative therapies are limited, the risk-benefit considerations may be impacted by uncertainty about reversibility, lack of methods for monitoring PEG accumulation in vivo without biopsy, and the variability in tissues affected depending on species studied. We demonstrate the use of magnetic resonance spectroscopy (MRS) to measure PEG concentrations at multiple time points in vivo in the kidney with comparison to PEG concentrations ex vivo in body fluids and tissue extracts using nuclear magnetic resonance (NMR) spectroscopy. Furthermore, we demonstrate the use of these techniques to study distribution and elimination of PEG in a dog model of PEGylation-associated vacuolation. This report suggests that MRS could be further investigated as a feasible imaging-based method for monitoring PEG accumulation in a clinical setting in conjunction with NMR quantitation of PEG in plasma and urine.

Long-Term Safety of PEGylated Coagulation Factor VIII in the Immune-Deficient Rowett Nude Rat

Turoctocog alfa pegol (N8-GP) is a glycoPEGylated human recombinant factor VIII for the treatment of hemophilia A. The safety profile of rFVIII, and polyethylene glycols (PEG) technology, is well-established. Conducting long-term toxicity studies in animals using human proteins can be complicated by anti-drug antibody (ADA) development. To evaluate long-term safety of N8-GP, 26- and 52-week toxicity studies were conducted in immune-deficient rats dosed intravenously every fourth day with 0, 50, 150, 500, or 1200 IU/kg N8-GP. Observations included clinical observations, body weight, ophthalmoscopy, hematology, chemistry, coagulation, urinalysis, toxicokinetics, antibody analysis, and macroscopic/microscopic organ examination. Immunohistochemical staining examined the distribution of PEG in the brain. No adverse test item-related findings were seen and PEG was not detected in the brain. Exposure was confirmed for ~75% of the animals dosed with 500 and 1200 IU/kg N8-GP; the high lower limit of quantification of the bioanalysis assay prevented confirmation of exposure in the lower doses. A small number of animals developed ADAs, and the proportion of animals surviving until scheduled termination was >80%. N8-GP was well tolerated, and the immune-deficient rat proved suitable for testing long-term toxicity of human proteins that are immunogenic in animals.