“Prevalence of Inhibitors in Hemophilia Patients and its Clinical Implications”: A Study of 276 Patients in Western India

Advances in Development of Drug Treatment for Hemophilia with Inhibitors

Patients with hemophilia A and B who have inhibitors face limited treatment options, because replacement therapy with clotting factor VIII or IX concentrates is ineffective, particularly for patients with high-titer inhibitors. Current mainstay therapies include immune tolerance induction (through frequent injections of clotting factor VIII or IX concentrates) to eradicate inhibitors and bypassing agents (such as recombinant activated clotting factor VII and activated prothrombin complex concentrates) for the prevention and treatment of bleeding episodes. The use of these agents typically requires intravenous injections and sometimes hospitalization, which can be burdensome for patients. More recently, emicizumab, a bispecific antibody that mimics the function of activated clotting factor VIII, has demonstrated favorable efficacy for prophylaxis in patients with hemophilia A and inhibitors, representing a promising new therapeutic strategy. Ongoing research aims to discover and develop easy-to-use nonfactor agents for managing hemophilia with inhibitors. This review summarizes the current understanding of the pathophysiology of inhibitor development in hemophilia, outlines existing treatment options, and discusses advancements in novel therapeutic biologics, including a recombinant activated clotting factor VII variant (marzeptacog alfa), a new bispecific antibody (Mim8), antitissue factor pathway inhibitor antibodies (concizumab and marstacimab), and small interfering RNA targeting antithrombin (fitusiran). All of these agents are administered subcutaneously, with some offering the convenience of less frequent dosing (e.g., weekly or monthly). These potential drug candidates may provide significant benefits for the prophylaxis or treatment of bleeding disorders in patients with hemophilia and inhibitors.

Evaluation of Safety and Efficacy of Emicizumab Prophylaxis in Egyptian Pediatric Patients with Hemophilia A

Objective

Hemophilia A (HA) is a hereditary X-linked bleeding disorder secondary to deficiency of the clotting factor VIII (FVIII). Emicizumab is a monoclonal antibody that replaces the function of the activated FVIII and prevents bleeding in HA patients. Emicizumab is expected to ameliorate bleeding risk in those patients together with subsequent complications. However, there is a scarcity of data about its safety and efficacy in patients with HA. We aimed to evaluate the safety and efficacy of emicizumab prophylaxis in Egyptian pediatric patients with HA.

Materials and Methods

A prospective cohort study was carried out with 88 HA patients who received emicizumab prophylaxis. Breakthrough bleeding episodes and the annualized bleeding rate (ABR) were reported for all patients before and after emicizumab prophylaxis. Also, all adverse events during prophylaxis were documented to evaluate the safety of emicizumab.

Results

Joint bleeds occurred in 94% of the patients. Among those patients, 58% had one target joint, 36.4% had more than one target joint, and 5.6% had no target joints. Furthermore, 17% of patients were positive for FVIII inhibitors. The median annualized joint bleeding rate was reduced remarkably after emicizumab prophylaxis (36 before versus 0 after emicizumab). The median ABR was 48 before emicizumab versus 0 after emicizumab. Eight patients experienced mild breakthrough bleeding episodes. The most common adverse events were local reactions at injection sites, headache, arthralgia, fever, and diarrhea.

Conclusion

Prophylaxis using emicizumab was associated with a significantly lower bleeding rate in HA patients with and without inhibitors. The majority of patients had zero bleeds with emicizumab prophylaxis.

Unearthing the genotype-inhibitor phenotype association in severe haemophilia A: A north Indian cohort study

INTRODUCTION

Various risk factors for inhibitor development in haemophilia A (HA) have been described but Indian data remains scanty.

AIM

We aimed to evaluate the genetic changes in Indian HA-patients that are associated with the development of inhibitors.

METHODS

All HA-patients with inhibitors who availed coagulation-laboratory services from January-2015 till December-2021 and had their samples preserved for DNA extraction were included in this study. An equal number of severity-matched HA patients without inhibitors were also included as controls. Intron 22 and intron 1 inversions in Factor VIII gene were identified using inverse-shifting-PCR. Inversion-negative patients were further assessed by targeted NGS, MLPA.

RESULTS

Thirty HA-patients with inhibitors were identified. All had severe-HA. Thirty severe-HA-patients without inhibitors were also included as controls. Intron 22 inversion (63.3%) and large deletions (15%) were the commonest variants identified. There was no difference in genetic variants in patients with low and high titre inhibitors. A3, A2 and C2 were the most common domains involved in inversion-negative patients with inhibitors. However, there was no significant difference in domain involvement among inversion-negative patients with and without inhibitors. Seven novel-variants were identified, including three large deletions, one large duplication and two nonsense variants in inhibitor-positive patients, and one frameshift variant in inhibitor-negative patient. After adjusting for clinical risk-factors, large deletions were independently associated with the presence of inhibitors [aOR:6.1 (1.41-56.3)].

CONCLUSION

Intron 22 inversions are the commonest variant in Indian patients with severe-HA. Large deletions predispose to inhibitor development independent of clinical risk factors.

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

INTRODUCTION

The development of inhibitors with factor VIII (FVIII) replacement therapy is one of the most common and challenging complications of haemophilia A (HA) treatment, jeopardising treatment efficacy and predisposing patients to high risks of morbidity and mortality. The management of patients with inhibitors is particularly challenging in countries where resources are limited.

AIM

To provide a comprehensive summary of the management of HA with inhibitors while focusing on differences in practice between Western and non-Western countries and how resource scarcity can impact HA management, leading to suboptimal outcomes in patients with inhibitors.

METHODS

Summary of key evidence and regional expert opinion.

RESULTS

We address, particularly, the diagnosis of and testing for inhibitors, as well as the epidemiology of inhibitors, including incidence, prevalence and disease burden. Secondly, we provide an overview of the current treatment landscape in HA with inhibitors regarding the eradication of inhibitors with immune tolerance induction and the treatment and prevention of bleeding with bypassing agents, non-factor replacement agents and other experimental therapies. This is complemented with insights from the authors around the applicability of, and challenges associated with, such therapies in their settings of practice.

CONCLUSIONS

We conclude by proposing some key steps towards bridging the gaps in the management of HA with inhibitors in resource-limited countries, including: (1) the collection of quality data that can inform healthcare reforms and policies; (2) improving disease knowledge among healthcare practitioners and patients with the aim of standardising disease management across centres and (3) working towards promoting equal access to HA care and therapies for everyone.

Inhibitor; An Uncommon But Vexing Challenge In North Indian Patients With Hemophilia A

Factor VIII replacement is the mainstay of treatment in hemophilia A but may lead to the development of inhibitors. While a vexing clinical problem, some observations suggest that the presence of inhibitors may not necessarily portend a higher bleeding risk. Our aim was to assess the prevalence and clinicopathological correlates of inhibitors in a well characterized cohort of Indian patients with HA patients. We retrospectively reviewed the clinical details and laboratory findings of consecutive hemophilia A patients attending a north-Indian tertiary-care center from 2010 to 2020. Among 592 patients with HA, inhibitors were detected in 35 patients (5.9%). Prevalence of inhibitors in moderate and severe hemophilia was 4.2% and 6.7%, respectively. Most patients with inhibitors had history of transfusion with factor VIII alone (54.3%) or a combination of factor VIII concentrate and other blood-products (42.9%). Intracranial bleed was significantly more frequent in patients with inhibitors compared to those without inhibitors (20% vs. 4.1%; p-0.001). Time dependent and immediately acting inhibitors were seen in 60% and 40% patients, respectively. High-titre (> 5 BU) and low-titre inhibitors (< 5 BU) were detected in 28 (80%) and 7 (20%) patients, respectively. Prevalence of inhibitors in our cohort was 5.9% and most had high-titre, time dependent inhibitors. These patients may have a higher risk of intracranial bleeding.