Safety, pharmacokinetics and efficacy of factor VIIa formulated with PEGylated liposomes in haemophilia A patients with inhibitors to factor VIII--an open label, exploratory, cross-over, phase I/II study

Thrombin generation for monitoring hemostatic therapy in hemophilia A: A narrative review

Patients with severe hemophilia A (HA) have an increased risk of spontaneous and trauma-related bleeding because of a congenital absence of factor VIII (FVIII). Most severe HA patients use prophylactic FVIII concentrate, the effect of which can be monitored with FVIII activity level measurement. However, FVIII activity level is less valuable in predicting the potential clinical bleeding risk. Some patients still experience breakthrough bleeds despite adequate FVIII trough levels, whereas others do not bleed with trough levels below threshold. This difference may be caused by inter-individual differences in pro- and anticoagulant factors, the so-called hemostatic balance. Thrombin generation assays (TGAs) measure the hemostatic balance as a whole. Thereby, the TGAs may be a better tool in the guidance and monitoring of treatment in HA patients. In addition, TGAs offer the opportunity to determine the response to bypassing agents and treatment with non-factor replacement therapy, in which FVIII activity assays are not suitable for monitoring. This review summarizes the current knowledge about monitoring different HA treatment modalities by TGA, as a single treatment option and when used in a concomitant fashion.

An overview on the investigation of nanomaterials' effect on plasma components: immunoglobulins and coagulation factor VIII, 2010-2020 review

FVIII and immunoglobulins (Igs) are the most prominent plasma proteins, which play a vital role in plasma hemostasis. These proteins have been implemented frequently in protein therapy. Therefore, their maintenance, durability, and stability are highly essential. Herein, various approaches to improve protein functions have been investigated, such as using recombinant protein replacement. In comparison, advances in nanotechnology have provided adequate context to boost biomaterial utilization. In this regard, the applications of various nanoparticles such as polymeric nanomaterials (PEG and PLGA), metal nanoparticles, dendrimers, and lipid based nanomaterials (liposomes and lipid nanoparticles) in stability and the functional improvement of antibodies and coagulation factor VIII (FVIII) have been reviewed from 2010 to 2020. Reviewing related articles has shown that not only can nanomaterials adequately protect the structure of proteins, but have also improved proteins' functions in some cases. For example, the high rate of FVIII instability has been successfully enhanced by bio-PEGylation. Also, utilizing PEGylated liposomes, using the PEG-lip technique for coating nanostructures, leads to FIIIV half-life prolongation. Hence, PEGylation had most impact on the stability of FVIII. Likewise, PEG-coated liposome nano-carriers also presented such a good effect on stability improvements for FVIII due to their ability to tune the immune system by reducing FVIII immunogenicity. Similarly, Ig PEGylation and conjugation to magnetic nanoparticles resulted in increased half-life and better purification of Igs, respectively, without any loss in structural or functional features. Consequently, metal-organic frameworks and recent hybrid systems have been introduced as promising nanomaterials in biomedical applications. As far as we know, this is the first study in this field, which considers the applications of nanoparticles for improving the storage and stability of antibodies and coagulation FVIII.

Safety assessment of a new nanoemulsion-based drug-delivery system reveals unexpected drug-free anticoagulant activity

Aim: A preclinical safety assessment of a novel nanoemulsion drug-delivery system, initially developed to improve the posology of efavirenz (EFV), was conducted with a specific focus on possible immunological and hematological complications. Materials & methods: Assessment of common acute toxicities, such as complement activation and cytokine secretion, was performed using validated assays known to have good correlation with in vivo end points. Results & conclusion: Compared with a standard aqueous solution of EFV, the EFV nanoemulsion showed no significant effect on immune cell function or phenotype. Prolongation of activated partial thromboplastin time was observed for EFV-loaded nanoemulsions (88% at 4 μg/ml) as well as unloaded nanoemulsions (52%) highlighting the potential for drug-free anticoagulant activity and warranting further investigation of the mechanism and utility of these materials.

Performing and interpreting individual pharmacokinetic profiles in patients with Hemophilia A or B: Rationale and general considerations

OBJECTIVES

In a separate document, we have provided specific guidance on performing individual pharmacokinetic (PK) studies using limited samples in persons with hemophilia with the goal to optimize prophylaxis with clotting factor concentrates. This paper, intended for clinicians, aims to describe how to interpret and apply PK properties obtained in persons with hemophilia.

METHODS

The members of the Working Party on population PK (PopPK) of the ISTH SSC Subcommittee on Factor VIII and IX and rare bleeding disorders, together with additional hemophilia and PK experts, completed a survey and ranking exercise whereby key areas of interest in the field were identified. The group had regular web conferences to refine the manuscript's scope and structure, taking into account comments from the external feedback to the earlier document.

RESULTS

Many clinical decisions in hemophilia are based on some form of explicit or implicit PK assessment. Individual patient PK profiles can be analyzed through traditional or PopPK methods, with the latter providing the advantage of fewer samples needing to be collected on any prophylaxis regimen, and without the need the for a washout period. The most useful presentation of PK results for clinical decision making are a curve of the factor activity level over time, the time to achieve a certain activity level, or related parameters like half-life or exposure (AUC). Software platforms have been developed to deliver this information to clinicians at the point of care. Key characteristics of studies measuring average PK parameters were reviewed, outlining what makes a credible head-to-head comparison among different concentrates. Large data collections of PK and treatment outcomes currently ongoing will advance care in the future.

CONCLUSIONS

Traditionally used to compare different concentrates, PK can support tailoring of hemophilia treatment by individual profiling, which is greatly simplified by adopting a PopPK/Bayesian method and limited sampling protocol.

Half-life extension technologies for haemostatic agents

The use of plasma-derived and recombinant coagulation factors for the treatment of haemophilia A and B is well established and permits patients to live a relatively normal life. In order to improve treatment options, several products are in development, which have a prolonged duration of action, thus enabling less frequent prophylactic dosing and aiming to reduce the burden of treatment. Several innovative approaches are being pursued to extend the half-life of factor VIIa, factor VIII and factor IX, utilising technologies such as Fc fusion, recombinant albumin fusion and addition of polyethyleneglycol (PEG) (PEGylation). These methods prolong the time in the circulation by reducing degradation and elimination. This review summarises the technologies and products in development and their stages of development, and also discusses their pros and cons.

Predicting dosing advantages of factor VIIa variants with altered tissue factor-dependent and lipid-dependent activities

BACKGROUND

Recombinant factor VIIa (rFVIIa) is an FX-cleaving coagulation enzyme licensed for the treatment of bleeding episodes in hemophiliacs with inhibitory antibodies. Even though the optimal dosing and comparative dose efficacy of rFVIIa remain poorly understood, genetic or chemical modifications of rFVIIa have been proposed, with the goal of achieving faster and longer hemostatic action. No ongoing trial is currently comparing rFVIIa variants with each other.

OBJECTIVES AND METHODS

We used mathematical modeling to compare the pharmacokinetics, dose-response (pharmacodynamics) and dose-effect duration (pharmacokinetics/pharmacodynamics) of rFVIIa variants to predict their optimal doses. The pharmacodynamic (PD) model of FXa generation by FVIIa in complexes with tissue factor (TF) and procoagulant lipids (PLs) was validated against published ex vivo and in vitro thrombin generation (TG) experiments. To compare variants' safety profiles, the highest non-thrombogenic doses were estimated from the clinical evidence reported for the licensed rFVIIa product.

RESULTS

The PD model correctly described the biphasic TF-dependent and PL-dependent dose response observed in TG experiments in vitro. The pharmacokinetic/PD simulations agreed with published ex vivo TG data for rFVIIa and the BAY 86-6150 variant, and explained the similar efficacies of a single dose of 270 μg kg(-1) (as reported in the literature) and repeated doses of 90 μg kg(-1) of unmodified rFVIIa. The duration of the simulated hemostatic effect after a single optimal dose was prolonged for rFVIIa variants with increased TF affinity or extended half-lives, but not for those with modulated PL activity.

CONCLUSIONS

Some modifications of the rFVIIa molecule may not translate into a prolonged hemostatic effect.

Nanoparticles and the blood coagulation system. Part I: benefits of nanotechnology

Nanotechnology is proven to provide certain benefits in drug delivery by improving solubility, increasing uptake to target sites and changing pharmacokinetics profiles of traditional drugs. Since properties of many materials change tremendously at the nanoscale levels, nanotechnology is also being explored in various industrial applications. As such, nanoparticles are rapidly entering various areas of industry, biology and medicine. The benefits of using nanotechnology for industrial and biomedical applications are often tempered by concerns about the safety of these new materials. One such area of concern includes their effect on the immune system. While nanoparticle interactions with various constituents of the immune system have been reviewed before, little attention was given to nanoparticle effects on the blood coagulation system. Nanoparticle interface with the blood coagulation system may lead to either benefits to the host or adverse reactions. This article reviews recent advances in our understanding of nanoparticle interactions with plasma coagulation factors, platelets, endothelial cells and leukocytes. Part I is focused on desirable interactions between nanoparticles and the coagulation system, and discusses benefits of using nanotechnology to intervene in coagulation disorders. Undesirable interactions posing safety concerns are covered in part II, which will be published in the June issue of Nanomedicine.

Molecular approaches for improved clotting factors for hemophilia

Hemophilia is caused by a functional deficiency of one of the coagulation proteins. Therapy for no other group of genetic diseases has seen the progress that has been made for hemophilia over the past 40 years, from a life expectancy in 1970 of ∼20 years for a boy born with severe hemophilia to essentially a normal life expectancy in 2013 with current prophylaxis therapy. However, these therapies are expensive and require IV infusions 3 to 4 times each week. These are exciting times for hemophilia because several new technologies that promise extended half-lives for factor products, with potential for improvements in quality of life for persons with hemophilia, are in late-phase clinical development.

Future of coagulation factor replacement therapy

Over a million patients worldwide currently suffer from hemophilia and other congenital clotting factor deficiencies. Patients affected with hemophilia A and B are treated by intravenous replacement therapy of factor VIII and factor IX, respectively. Current hemophilia treatments have favorably supported their efficacy, tolerability, and safety profiles. The onset of alloantibodies inactivating the infused coagulation factor is the main problem in hemophilia patients rendering replacement therapies ineffective; another disadvantage is the short half-life of the infused clotting factors with the need for multiple and frequent infusions to manage a bleeding episode. Now, the challenge in the management of hemophilia treatment is the prolongation of the half-life and reduction in the immunogenicity of recombinant clotting factors. The bioengineering strategies, previously applied successfully to other therapeutic proteins, encourage the current efforts to produce novel coagulation factors with more prolonged bioavailability, with increased potency and resistance to inactivation and potentially reduced immunogenicity.

New treatments in hemophilia: insights for the clinician

Hemophilia has evolved from an often fatal hereditary bleeding disorder to a disorder for which safe and effective treatment is available. However, there are several challenges remaining in the treatment of hemophilia. Prophylaxis to prevent bleeding is costly and requires frequent intravenous injections, which are cumbersome for patients. Venous access is often difficult to achieve, especially in small children where central venous lines may need to be implanted. Development of inhibitory antibodies makes treatment of acute bleeds difficult and prophylaxis in patients with inhibitors must also be better addressed. In order to improve treatment, new products are being developed, some of which are already in clinical trials. There are several approaches to prolonging half-lives such as PEGylation, Fc fusion and albumin fusion. Increased activity has been demonstrated in preclinical trials for factor IX and in a human trial with factor VII where the activity of the molecules has been increased by manipulation of the molecular composition. Additional approaches, including blockage of inhibitors of clotting, are also under investigation. Factor VIII and factor IX gene therapy have become a tangible possibility since phase I data recently have been published. Results are promising and there is hope that in the near future substantial progress will be made, perhaps making hemophilia the first genetic condition to be cured.

Molecular approaches for improved clotting factors for hemophilia

Hemophilia is caused by a functional deficiency of one of the coagulation proteins. Therapy for no other group of genetic diseases has seen the progress that has been made for hemophilia over the past 40 years, from a life expectancy in 1970 of ∼20 years for a boy born with severe hemophilia to essentially a normal life expectancy in 2013 with current prophylaxis therapy. However, these therapies are expensive and require IV infusions 3 to 4 times each week. These are exciting times for hemophilia because several new technologies that promise extended half-lives for factor products, with potential for improvements in quality of life for persons with hemophilia, are in late-phase clinical development.

Past, present and future of hemophilia: a narrative review

Over the past forty years the availability of coagulation factor replacement therapy has greatly contributed to the improved care of people with hemophilia. Following the blood-borne viral infections in the late 1970s and early 1980, caused by coagulation factor concentrates manufactured using non-virally inactivated pooled plasma, the need for safer treatment became crucial to the hemophilia community. The introduction of virus inactivated plasma-derived coagulation factors and then of recombinant products has revolutionized the care of these people. These therapeutic weapons have improved their quality of life and that of their families and permitted home treatment, i.e., factor replacement therapy at regular intervals in order to prevent both bleeding and the resultant joint damage (i.e. primary prophylaxis). Accordingly, a near normal lifestyle and life-expectancy have been achieved. The main current problem in hemophilia is the onset of alloantibodies inactivating the infused coagulation factor, even though immune tolerance regimens based on long-term daily injections of large dosages of coagulation factors are able to eradicate inhibitors in approximately two-thirds of affected patients. In addition availability of products that bypass the intrinsic coagulation defects have dramatically improved the management of this complication. The major challenges of current treatment regimens, such the short half life of hemophilia therapeutics with need for frequent intravenous injections, encourage the current efforts to produce coagulation factors with more prolonged bioavailability. Finally, intensive research is devoted to gene transfer therapy, the only way to ultimately obtain cure in hemophilia.

The use of PEGylated liposomes in the development of drug delivery applications for the treatment of hemophilia

Hemophilia A is a rare X-linked bleeding disorder caused by lack or dysfunction of coagulation factor VIII (FVIII). Hemophilia A is treated with replacement therapy, but frequent injections of the missing FVIII often lead to the formation of inhibitory antibodies. Patients who develop high levels of inhibitors must be treated with bypassing agents such as activated FVII (FVIIa). Both FVIII and FVIIa have short half-lives and require multiple injections. Long-acting forms of these proteins would therefore reduce the frequency of injections, improve patient compliance and reduce complications. In this article we present a new platform technology that produces long-acting forms of FVIII and FVIIa and improves the efficacy of hemophilia treatment. This technology is based on the binding of proteins/peptides to the outer surface of PEGylated liposomes (PEGLip). Binding is dependent on an amino acid consensus sequence within the proteins and is highly specific. At the same time, binding is non-covalent and does not require any modification of the therapeutic agent or its production process. Association of proteins with PEGLip results in substantial enhancements in their pharmacodynamic properties following administration. These improvements seem to arise from the association of formulated proteins with platelets prior to induction of coagulation.