Observational study of recombinant factor VIII-Fc, rFVIIIFc, in hemophilia A

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 profiling of anti-factor VIII antibodies in Japanese patients with congenital hemophilia A during factor VIII replacement and immune-tolerance induction therapy

When patients with hemophilia A develop factor VIII (FVIII) inhibitors, FVIII replacement therapy becomes ineffective. Although immune-tolerance induction (ITI) therapy has been used to eradicate inhibitors, treatment is unsuccessful in approximately 30% of cases. However, the mechanism behind treatment failure remains unclarified. We retrospectively examined the longitudinal profiles of immunoglobulin G (IgG) subclasses and/or the inhibitory activities of FVIII in plasma samples from 14 Japanese patients with congenital hemophilia A during hemostatic, FVIII replacement, and/or ITI therapies. In five patients, an increase in IgG4 was observed simultaneously with a decrease in IgG1 when the patient had a history of relatively high FVIII inhibitor titers, reflecting an apparent change in humoral immunity. In addition, we examined the reactivity and specificity of the patients' anti-FVIII IgG1 and IgG4 to FVIII domains by immunoblotting. Under our experimental conditions, plasma from three patients with historically higher inhibitor titers appeared to have high titers of antibodies against the A2-a2 domain, which did not necessarily correlate with ITI failure. These observations may improve scientific understanding of the immune response to infused FVIII in patients with hemophilia A.

Efmoroctocog Alfa: A Review in Haemophilia A

Efmoroctocog alfa (Elocta®, Eloctate®, Eloctate™), an extended half-life (EHL) recombinant factor VIII (rFVIII)-Fc fusion protein, is approved for the treatment and prophylaxis of bleeding in patients with haemophilia A. The efficacy of efmoroctocog alfa in the prevention and treatment of bleeding in previously treated patients (PTPs) and previously untreated patients (PUPs) with severe haemophilia A has been demonstrated in phase III studies; this includes its use in the perioperative setting (in PTPs). Furthermore, the effectiveness of efmoroctocog alfa in clinical practice has been confirmed in numerous real-world studies; compared with conventional, standard half-life (SHL) FVIII products, prophylaxis with this EHL FVIII product achieved similar or reduced bleeding rates with fewer injections. Efmoroctocog alfa was generally well tolerated; inhibitors occurred in approximately one-third of PUPs in a phase III study. Efmoroctocog alfa is an established and effective EHL FVIII replacement therapy for the management of haemophilia A. Compared with SHL FVIII products, EHL FVIII products such as efmoroctocog alfa have the potential to optimise prophylactic outcomes by decreasing the burden of treatment or increasing the level of bleed protection.

Hemophilia A (Factor VIII Deficiency)

Remarkable changes are occurring in the diagnosis and management of individuals with hemophilia A. Genetic testing, including next-generation sequencing, enables family planning, carrier testing, and prenatal diagnosis. Musculoskeletal ultrasound examination facilitates the early detection of acute bleeds and joint disease in clinic, enabling more rapid bleed resolution and treatment planning. Novel therapies offer simpler weekly or monthly administration, some by subcutaneous injection, with better compliance and quality of life, as well as fewer bleeds. Gene therapy provides a 1-time phenotypic "cure" that is cost effective, but may be complicated by waning levels, vector immune responses, and hepatotoxicity.