Fc-fusion technology and recombinant FVIII and FIX in the management of the hemophilias

Considerations for Glycoprotein Production

This chapter is intended to provide insights for researchers aiming to choose an appropriate expression system for the production of recombinant glycoproteins. Producing glycoproteins is complex, as glycosylation patterns are determined by the availability and abundance of specific enzymes rather than a direct genetic blueprint. Furthermore, the cell systems often employed for protein production are evolutionarily distinct, leading to significantly different glycosylation when utilized for glycoprotein production. The selection of an appropriate production system depends on the intended applications and desired characteristics of the protein. Whether the goal is to produce glycoproteins mimicking native conditions or to intentionally alter glycan structures for specific purposes, such as enhancing immunogenicity in vaccines, understanding glycosylation present in the different systems and in different growth conditions is essential. This chapter will cover Escherichia coli, baculovirus/insect cell systems, Pichia pastoris, as well as different mammalian cell culture systems including Chinese hamster ovary (CHO) cells, human endothelial kidney (HEK) cell lines, and baby hamster kidney (BHK) cells.

Congenital hemophilia A with low activity of factor XII: a case report and literature review

BACKGROUND

Congenital hemophilia A is a recessive inherited hemorrhagic disorder. According to the activity of functional coagulation factors, the severity of hemophilia A is divided into three levels: mild, moderate and severe. The first bleeding episode in severe and moderate congenital hemophilia A occurs mostly in early childhood and mainly involves soft tissue and joint bleeds. At present, there are limited reports on severe congenital hemophilia A with low factor XII (FXII) activity during the neonatal period.

CASE PRESENTATION

A 13-day-old neonate was admitted to the hospital with hematoma near the joints of both upper arms. Coagulation tests showed he had low activity of factor VIII (FVIII) and FXII. He was diagnosed with congenital hemophilia A and treated with human coagulation factor VIII (recombinant FVIII). Although the hematoma became smaller, FVIII activity was only increased to a certain extent and FXII activity decreased gradually. Unfortunately, the child responded poorly to recombinant human coagulation factor VIII and his guardian rejected prophylactic inhibitors and genetic testing and refused further treatment. Three months later, the child developed intracranial hemorrhage (ICH) due to low FVIII activity.

CONCLUSIONS

In hemophilia A, the presence of FVIII inhibitors, drug concentration and testing are three important aspects that must be considered when FVIII activity does not reach the desired level. Early positive disease treatment and prophylaxis can decrease the frequency of bleeding and improve quality of life. We recommend that pregnant women with a family history of hemophilia A undergo early prenatal and neonatal genetic testing.

Recombinant factor VIII Fc for the treatment of haemophilia A

Prophylaxis with factor VIII (FVIII) is the current therapeutic approach for people with haemophilia A. However, standard half-life (SHL) FVIII products must be injected frequently, imposing a substantial burden on the individual and making it difficult to tailor therapy according to patient need and lifestyle, which could impact adherence. Recombinant FVIII Fc fusion protein (rFVIIIFc; Elocta® , Sobi; Eloctate® , Sanofi) is a recombinant fusion protein that undergoes slower clearance from the body than SHL FVIII products. This pharmacokinetic property of rFVIIIFc allows prophylactic administration every 3-5 days, or once weekly in selected patients, with doses adjusted to patient needs and clinical outcomes. Higher FVIII levels can be achieved maintaining dosing frequency similar to that usually applied with SHL FVIII. This review provides a summary of recent data from the A-LONG, Kids A-LONG, ASPIRE and PUPs A-LONG studies and recently published real-world experience relevant to rFVIIIFc use in individualised regimens. The review also introduces ongoing studies of rFVIIIFc, including its use for induction of immune tolerance, and discusses some aspects to consider when switching patients to rFVIIIFc and managing ongoing treatment. In summary, rFVIIIFc is suitable for individualised prophylaxis regimens that can be tailored according to patient clinical needs and lifestyle.

Emerging benefits of Fc fusion technology in the context of recombinant factor VIII replacement therapy

Although the primary reason for recombinant factor VIII Fc fusion protein (rFVIIIFc) development was to reduce treatment burden associated with routine prophylaxis, new evidence suggests additional benefits of Fc fusion technology in the treatment of people with haemophilia A. Preclinical research has been utilized to characterize the potential immunomodulatory properties of rFVIIIFc, including an ability to reduce inflammation and induce tolerance to factor VIII. This has since been expanded into clinical research in immune tolerance induction (ITI) with rFVIIIFc, results of which suggest the potential for rapid tolerization in first‐time ITI patients and therapeutic benefit in patients undergoing rescue ITI. The potential for improved joint health through the anti‐inflammatory properties of rFVIIIFc has also been suggested. In addition, a new avenue of research into the role of rFVIIIFc in promoting bone health in patients with haemophilia A, potentially through reduced osteoclast formation, has yielded encouraging results that support further study. This review summarizes the existing preclinical and clinical studies of immunomodulation and tolerization with rFVIIIFc, as well as studies in joint and bone health, to elucidate the potential benefits of rFVIIIFc in haemophilia A beyond the extension of factor VIII half‐life.

Novel therapies and current clinical progress in hemophilia A

The evolution of hemophilia treatment and care is a fascinating one but has been fraught with many challenges at every turn. Over the last 50 years or so patients with hemophilia and providers have witnessed great advances in the treatment of this disease. With these advances, there has been a dramatic decrease in the mortality and morbidity associated with hemophilia. Even with the remarkable advancements in treatment, however, new and old challenges continue to plague the hemophilia community. The cost of factor replacement and the frequency of infusions, especially in patients with severe hemophilia on prophylaxis, remains a significant challenge for this population. Other challenges include obtaining reliable venous access, especially in younger patients, and the development of neutralizing alloantibodies (inhibitors). The development of extended half-life products, a bispecific antibody which mimics the coagulation function of factor VIII (FVIII) and inhibition of anticoagulation proteins such as antithrombin with antibodies, aptamers or RNA interference technology have offered novel therapeutic approaches to overcome some of these existing challenges. Additionally, ongoing gene therapy research offers a way to possibly cure hemophilia. These novel treatment tools in conjunction with the establishment of an increasing number of comprehensive hemophilia centers and worldwide advocacy efforts have continued to push the progress of hemophilia care to new frontiers. This review highlights and summarizes these novel therapeutic approaches and the current clinical progress of hemophilia A.

Pharmacokinetics and pharmacodynamics of SCT800, a new recombinant FVIII, in hemophilia A mice

AIM

SCT800 is a new third-generation recombinant FVIII agent that is undergoing promising preclinical study. This study aimed to investigate the pharmacokinetic and pharmacodynamic profiles of SCT800 in hemophilia A mice.

METHODS

After hemophilia A mice were intravenously injected with single dose of SCT800 (80, 180, and 280 IU/kg) or the commercially available product Xyntha (280 IU/kg), pharmacokinetics profiles were evaluated based on measuring plasma

FVIII

C. For pharmacodynamics study, dose-response curves of SCT800 and Xyntha (1-200 IU/kg) were constructed using a tail bleeding model monitoring both bleeding time and blood loss.

RESULTS

Pharmacokinetics profile analysis showed a dose independency of SCT800 ranging from 80 to 280 IU/kg and comparable pharmacokinetic profiles between SCT800 and Xyntha at the doses tested. Pharmacodynamics study revealed comparable ED50 values of SCT800 and Xyntha in the tail bleeding model: 14.78 and 15.81 IU/kg for bleeding time, respectively; 13.50 and 13.58 IU/kg for blood loss, respectively. Moreover, at the doses tested, the accompanying dose-related safety evaluation in the tail bleeding model showed lower hypercoagulable tendency and wider dosage range potential for SCT800 than Xyntha.

CONCLUSION

In hemophilia A mice, SCT800 shows comparable pharmacokinetics and pharmacodynamics to Xyntha at the doses tested, and possibly with better safety properties.