Management of haemophilia A with inhibitors: A regional cross-talk

Advances in biopharmaceutical products for hemophilia

Hemophilia is caused by the deficiency of clotting factors due to a single genetic abnormality. Replacement therapies have evolved from plasma-derived to recombinant coagulation factor concentrates but continue to have certain limitations. Monoclonal antibodies are clinical prophylactic treatment options unaffected by inhibitors and have better compliance than coagulation factor concentrates for patients with hemophilia. Gene therapy is a breakthrough in hemophilia treatment, as it drives the hepatic expression of factor VIII or factor IX and requires only a single administration to enable long-term replacement treatment in adult patients. Furthermore, biopharmaceutical products that target new pathways unaffected by inhibitors, including tissue factor pathway inhibitors, activated protein C, and antithrombin, as well as pharmaceutical technology advances to reduce dosing frequency, have demonstrated promising clinical results. This review provides a comprehensive overview of these biopharmaceutical products and explores the future of hemophilia treatment.

Real-world insights into the management of hemophilia A in Italy: treatment patterns and healthcare resource utilization

PURPOSE

This real-world analysis described the Hemophilia A (HA) population in Italy, evaluating drug utilization and consumption of factor VIII (FVIII) products of patients under prophylaxis and on-demand therapy.

METHODS

From Jan-2017 to Jun-2022, male patients with HA were identified through prescriptions of FVIII products [extended half-life FVIII, standard half-life recombinant FVIII, and plasma-derived FVIII (EHL FVIII, SHL rFVIII, and pdFVIII, respectively)], or emicizumab or FVIII plus von Willebrand factor or HA-related hospitalization using administrative flows of Italian healthcare entities. Patients on treatment with FVIII products during 2021-2022 were stratified by treatment regimen (prophylaxis/on-demand). The mean annual consumption expressed in International Units (IU) of EHL FVIII and SHL FVIII in patients treated during 2021-2022 having at least 12-month follow-up were assessed.

RESULTS

Among included HA patients, 145 (39.5%) received EHL FVIII and 222 (60.5%) SHL FVIII. Of 165 patients on prophylaxis, 105 (64%) received an EHL FVIII and 60 (36%) an SHL FVIII. The mean annual consumption of FVIII was 336,700 IU (median 319,000 IU) for EHL FVIII and 440,267 IU (median 360,500 IU) for SHL FVIII. Specifically, for patients on EHL FVIII, the most common drugs were efmoroctocog alfa (N = 51) and damoctocog alfa pegol (N = 50), followed by turoctocog alfa pegol (N = 25) and rurioctocog alfa pegol (N = 19). Of 702 HA patients initially treated with FVIII products, 74 (10.5%) switched to emicizumab during follow-up.

CONCLUSION

These findings revealed an extensive use of EHL FVIII products, suggesting growing efforts from clinicians to optimize prophylactic strategies and achieve better bleeding protection.

Large deletions and small insertions and deletions in the factor VIII gene predict unfavorable immune tolerance induction outcome in people with severe hemophilia A and high-responding inhibitors

INTRODUCTION

Hemophilia A is an inherited bleeding disorder caused by pathogenic variants in the factor VIII gene (F8), which leads to factor VIII (FVIII) deficiency. Immune tolerance induction (ITI) is a therapeutic approach to eradicate alloantibodies (inhibitors) against exogenous FVIII in people with inherited hemophilia A. Few studies have evaluated the role of F8 variants on ITI outcome.

MATERIAL AND METHODS

We included people with severe hemophilia A (FVIII ˂ 1 international units/dL) and high-responding inhibitors (≥ 5 Bethesda units/mL lifelong) who underwent a first course of ITI. Socio-demographic, clinical and laboratory data were collected. ITI outcomes were defined as total, partial successes, and failure. Detection of intron 1 and 22 inversions was performed by polymerase-chain reaction, followed by F8 sequencing.

RESULTS

We included 168 people with inherited hemophilia A and high-responding inhibitors, median age 6 years at ITI start. Intron 22 inversion was the most prevalent variant (53.6 %), followed by nonsense (16.1 %), small insertion/deletion (11.3 %), and large deletion (10.7 %). In comparison with intron 22 inversion, the odds of ITI failure were 15.5 times higher (odds ratio [OR] 15.50; 95 % confidence interval [95 % CI] 4.59-71.30) and 4.25 times higher (95 % CI, 1.53-12.3) among carriers of F8 large deletions and small insertions and deletions, respectively.

CONCLUSION

F8 large deletions and small insertions/deletions predicted ITI failure after a first course of ITI in patients with severe hemophilia A and high-responding inhibitors. This is the first study to show F8 large deletions and small insertions/deletions as predictors of ITI failure.

Budget impact and cost-utility analysis of prophylactic emicizumab versus on-demand bypassing agents for adolescent severe haemophilia A patients with inhibitors in India

INTRODUCTION

Severe Haemophilia A patients with inhibitors are currently being treated with bypassing agents like activated prothrombin complex concentrates (aPCC) and recombinant factor VIIa. Emicizumab is a recombinant humanized monoclonal antibody, introduced to reduce the bleeding events, improve treatment adherence, and quality of life. However, cost-effectiveness and long-term sustainability of the intervention is not studied in a low middle income setting like India.

AIM

The primary objective of this study was to evaluate the cost-utility of Emicizumab compared to traditional bypassing agents in the treatment of severe haemophilia A patients with inhibitors in India. Secondary objective was to analyze the budgetary impact of introducing Emicizumab for this patient population from the perspective of public health system in India.

METHODS

Markov model was created to compare the prophylactic emicizumab therapy against bypassing agents for a hypothetical cohort of 10-year-old adolescents in India. The time horizon was 10 years and model built based on health system perspective. Cost utility was expressed as costs per quality-adjusted life-years (QALYs) gained. All costs were expressed as 2021 US dollars. Probabilistic sensitivity analysis was performed to check the robustness of the estimates.

RESULTS

Prophylactic emicizumab was a cost saving intervention with negative Incremental Cost Utility Ratio (ICUR) against recombinant factor VIIa of -853,573 USD (INR -63,109,773), and negative ICUR of -211,675 USD (INR -15,650,403) against APCC. The estimated total budget for treating all the severe Haemophilia A patients with inhibitors in India was USD 59,042,000 (INR 4,365,329,312) for 10 years' time horizon (per patient cost of USD 295,210 [INR 21,826,646.56]).

CONCLUSION

Prophylactic emicizumab therapy is a cost saving intervention when compared to both the bypassing agents as it is less costly and more effective for severe Haemophilia A patients with inhibitors in India.

The self-reactive FVIII T cell repertoire in healthy individuals relies on a short set of epitopes and public clonotypes

Non-mutated FVIII-specific CD4 T cell epitopes have been recently found to contribute to the development of inhibitors in patients with hemophilia A (HA), while auto-reactive CD4 T cells specific to FVIII circulate in the blood of healthy individuals at a frequency close to the foreign protein ovalbumin. Thus, although FVIII is a self-protein, the central tolerance raised against FVIII appears to be low. In this study, we conducted a comprehensive analysis of the FVIII CD4 T cell repertoire in 29 healthy donors. Sequencing of the CDR3β TCR region from isolated FVIII-specific CD4 T cells revealed a limited usage and pairing of TRBV and TRBJ genes as well as a mostly hydrophobic composition of the CDR3β region according to their auto-reactivity. The FVIII repertoire is dominated by a few clonotypes, with only 13 clonotypes accounting for half of the FVIII response. Through a large-scale epitope mapping of the full-length FVIII sequence, we identified 18 immunodominant epitopes located in the A1, A3, C1, and C2 domains and covering half of the T cell response. These epitopes exhibited a broad specificity for HLA-DR or DP molecules or both. T cell priming with this reduced set of peptides revealed that highly expanded clonotypes specific to these epitopes were responsible individually for up to 32% of the total FVIII repertoire. These FVIII T cell epitopes and clonotypes were shared among HLA-unrelated donors tested and previously reported HA patients. Our study highlights the role of the auto-reactive T cell response against FVIII in HA and its similarity to the response observed in healthy individuals. Thus, it provides valuable insights for the development of new tolerance induction and deimmunization strategies.

Factor VIII inhibitors in hemophilia A treated with emicizumab: longitudinal follow-up of outcomes

Background

Using emicizumab in lieu of immune tolerance induction (ITI) for patients with hemophilia A (HA) and factor (F)VIII inhibitors has been well described. However, decisions regarding ITI initiation, regimen, and preservation of tolerance remain to be elucidated.

Objectives

To study the course of FVIII inhibitors in patients with HA and a history of FVIII inhibitors receiving emicizumab prophylaxis.

Methods

Patients with HA, with and without FVIII inhibitors, initiating emicizumab prophylaxis were prospectively followed up in our center. All patients with current or previous inhibitors were included in this analysis. Plasma samples for FVIII inhibitor assays were obtained every 3 to 6 months or following FVIII exposure. Patients documented annual bleeding rate and any FVIII exposure days (EDs).

Results

Of 162 emicizumab-treated participants, 51 met the inclusion criteria. A decrease in annual bleeding rate was observed in all 51 participants followed up for a median of 3.3 years, with 31 breakthrough bleeding episodes reported in 22 of 51 participants. FVIII inhibitor level transiently increased following FVIII exposures in 5 of 15 failed ITI participants. Eight of 21 participants who did not undergo ITI were exposed to FVIII (1-2 EDs)), and 1 of these 8 participants demonstrated increased FVIII inhibitor levels after head trauma (following 1 ED). Among participants who underwent successful ITI, 8 of 15 patients were exposed to FVIII over a total of 13 EDs (1-2 ED(s) each) for traumatic breakthrough bleeds. In all these participants, inhibitor levels remained zero, indicating successful tolerance maintenance.

Conclusion

Our longitudinal follow-up of emicizumab-treated patients with HA and FVIII inhibitors shows that occasional exposure to FVIII may induce a transient anamnestic response. Nonetheless, no FVIII inhibitor recurrence was noted following FVIII exposures in patients who underwent successful ITI.

FVIII inhibitor surveillance in children with hemophilia A in Indonesia: a report from the Indonesian Pediatric Hematology-Oncology Working Group

Background

Factor VIII (FVIII) inhibitor diagnosis and surveillance in Indonesia are challenging owing to geographic conditions and the lack of laboratory facilities nationwide for inhibitor assays. This study aimed to determine the prevalence of FVIII inhibitors in children diagnosed with hemophilia A (HA) in Indonesia.

Methods

A cross-sectional study was conducted in 12 hospitals in eight provinces of Indonesia between 2020 and 2021. Factor VIII inhibitor screening was performed in a central hemostasis laboratory for all children with HA (≤18 yr) who had received a minimum of 10 exposure days to clotting factor concentrates. The FVIII inhibitor titer was determined using the Bethesda assay.

Results

Children (388) were enrolled in this study, including 219 (56.4%), 131 (33.8%), and 38 (9.4%) with severe, moderate, and mild HA, respectively. The prevalence of children who developed FVIII inhibitors was 37 out of 388 (9.6%). Factor VIII inhibitors were found in 25/219 (11.4%) severe, 11/131 (8.3%) moderate, and 1/38 (2.6%) children with mild HA. Thirteen children had low-titer inhibitors and 24 had high-titer inhibitors, with a median of 9.44 (1.48‒412.0) Bethesda Units. Among 13 children with low-titer inhibitors, eight underwent a confirmation test, of which five tested negative and were classified as transient. A significant difference in annual joint bleeding rate was found between patients with low and high inhibitor titers and those without inhibitors (P＜0.001).

Conclusion

Factor VIII inhibitor prevalence in Indonesia was relatively low. However, the risk factors that may contribute to FVIII inhibitor development among Indonesian patients require further study.