Deciphering conundrums of adeno-associated virus liver-directed gene therapy: focus on hemophilia

Adeno-associated virus gene therapy has been the subject of intensive investigation for monogenic disease gene addition therapy for more than 25 years, yet few therapies have been approved by regulatory agencies. Most have not progressed beyond phase 1/2 due to toxicity, lack of efficacy, or both. The liver is a natural target for adeno-associated virus since most serotypes have a high degree of tropism for hepatocytes due to cell surface receptors for the virus and the unique liver sinusoidal geometry facilitating high volumes of blood contact with hepatocyte cell surfaces. Recessive monogenic diseases such as hemophilia represent promising targets since the defective proteins are often synthesized in the liver and secreted into the circulation, making them easy to measure, and many do not require precise regulation. Yet, despite initiation of many disease-specific clinical trials, therapeutic windows are often nonexistent, resulting in excess toxicity and insufficient efficacy. Iterative progress built on these attempts is best illustrated by hemophilia, with the first regulatory approvals for factor IX and factor VIII gene therapies eventually achieved 25 years after the first gene therapy studies in humans. Although successful gene transfer may result in the production of sufficient transgenic protein to modify the disease, many emerging questions on durability, predictability, reliability, and variability of response have not been answered. The underlying biology accounting for these heterogeneous responses and the interplay between host and virus is the subject of intense investigation and the subject of this review.

Three-year outcomes of valoctocogene roxaparvovec gene therapy for hemophilia A

BACKGROUND

Valoctocogene roxaparvovec transfers a human factor VIII (FVIII) coding sequence into hepatocytes of people with severe hemophilia A to provide bleeding protection.

OBJECTIVE

Present 3-year efficacy and safety in the multicenter, open-label, single-arm, phase 3 GENEr8-1 trial.

METHODS

GENEr8-1 enrolled 134 adult males with severe hemophilia A who were receiving FVIII prophylaxis. Efficacy endpoints included annualized bleeding rate (ABR), annualized FVIII utilization (AFU), FVIII activity (chromogenic substrate assay; imputed as 1 IU/dL at baseline and 0 IU/dL after discontinuation), and the Haemophilia-Specific Quality of Life Questionnaire for Adults (Haemo-QOL-A). Safety was assessed by adverse events (AEs).

RESULTS

At week 156, 131/134 participants remained on study; overall, 17/134 resumed prophylaxis. Mean (standard deviation [SD]) treated ABR decreased from 4.8 (6.5) bleeds/year at baseline to 0.8 (SD, 2.3; P <0.0001) bleeds/year during post-prophylaxis (prophylaxis cessation to last follow-up) and 0.97 (SD, 3.48) bleeds/year during year 3. AFU decreased 96.8% from baseline post-prophylaxis and 94.2% during year 3. At week 156, mean and median FVIII activity were 18.4 (SD, 30.8) and 8.3 IU/dL, respectively. FVIII activity decrease was lower between years 2‒3 than 1‒2. At the end of year 3, clinically meaningful improvements in Haemo-QOL-A Total Score were observed (mean change from baseline, 6.6; 95% confidence interval, 4.24‒8.87; P <0.0001). Mild alanine aminotransferase elevations remained the most common AE during year 3 (23.7% of participants). A serious AE of B-cell acute lymphoblastic leukemia was considered unrelated to treatment.

CONCLUSIONS

Hemostatic efficacy was maintained, and safety remained unchanged from previous years.

Evaluation of an e-Learning Program for Community Pharmacists for Dispensing Emicizumab (Hemlibra) in France: Nationwide Cross-Sectional Study

BACKGROUND

Since June 2021, patients with hemophilia A with antifactor VIII inhibitors and those with severe hemophilia A without antifactor VIII inhibitors treated with Hemlibra have had to choose between a community or hospital pharmacy. The French reference center for hemophilia developed the HEMOPHAR e-learning program for community pharmacists for dispensing emicizumab.

OBJECTIVE

This study aims to evaluate the efficiency and safety of this new care pathway by assessing the HEMOPHAR e-learning program.

METHODS

The methodology is based on Kirkpatrick's model for evaluating the immediate reaction of trained community pharmacists (level 1), their level of acquired knowledge (level 2), and their professional practice after 3 months of dispensation (level 3).

RESULTS

The HEMOPHAR e-learning program reached a large audience, with 67% (337/502) of the eligible community pharmacists following it. The immediate reaction was overall satisfying. High rates of engagement were reported with 63.5% (214/337) to 73.3% (247/337) of completed training modules, along with high rates of success with quizzes of 61.5% (174/337) to 95.7% (244/337). We observed that 83.9% (193/230) of the community pharmacists needed less than 2 attempts to pass the quiz of the module related to professional practice, while the other quizzes required more attempts. Advice on compliance and drug interactions were most frequently provided to patients by the community pharmacists.

CONCLUSIONS

This study suggests ways to improve the training of community pharmacists and to optimize coordination with treatment centers. This study also reports on the feasibility of switching to a community pharmacy in a secure pharmaceutical circuit, including in the context of a rare bleeding disease.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05449197; https://clinicaltrials.gov/study/NCT05449197.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

RR2-10.2196/43091.

FRONTIER1: a partially randomized phase 2 study assessing the safety, pharmacokinetics, and pharmacodynamics of Mim8, a factor VIIIa mimetic

BACKGROUND

Mim8 (denecimig) is a factor VIII (FVIII) mimetic bispecific antibody in development for the treatment of hemophilia. Data from the phase 1 part of FRONTIER1 (EudraCT: 2019-000465-20, NCT04204408, and NN7769-4513) suggested that Mim8 was well tolerated in healthy participants and exhibited pharmacokinetic (PK) properties consistent with dose proportionality.

OBJECTIVES

The partially randomized, phase 2, multiple ascending dose (MAD) part of FRONTIER1 aimed to evaluate the safety, PK, pharmacodynamics (PD), and exploratory efficacy of Mim8 in participants with hemophilia A with or without FVIII inhibitors.

METHODS

The MAD part of FRONTIER1 consisted of 42 participants, assigned to 5 cohorts, with participants in cohorts 3 and 4 randomized 1:1 to dosing weekly or every 4 weeks, respectively. Four of the 42 participants (9.5%) had FVIII inhibitors prior to study enrolment. The primary endpoint was treatment-emergent adverse events (TEAEs). PK and PD were evaluated by Mim8 plasma concentration and thrombin generation, respectively. Exploratory efficacy was assessed via the number of treated bleeds. Safety and PD parameters were also evaluated from an exploratory cohort treated with emicizumab.

RESULTS

Mim8 was well tolerated, with 1 serious TEAE (anxiety-related chest pain) deemed unrelated to Mim8. There was no dose dependency on the number, causality, type, or severity of TEAEs. PK/PD properties supported weekly to monthly dosing approaches, and few participants experienced treated bleeds beyond the lowest dose cohort (1 in cohorts 2 and 3, and 3 in cohort 5).

CONCLUSION

These data support the continued clinical development of Mim8, and FRONTIER1 has proceeded onto an extension phase.

Low-dose emicizumab prophylaxis in patients with severe hemophilia A: a retrospective study bringing new hope for our patients

BACKGROUND

Low-dose emicizumab can potentially offer a cost-effective treatment option in persons with hemophilia A, especially in developing countries.

OBJECTIVES

To compare the efficacy and safety of low-dose emicizumab with those on low-dose factor (F)VIII prophylaxis via chart review.

METHODS

After ethics approval, chart data of 2 groups of patients were reviewed: group 1 (low-dose emicizumab, n = 10; 3 mg/kg monthly without a loading dose) and group 2 (low-dose FVIII prophylaxis, n = 10; 10-20 IU/kg of FVIII concentrates twice a week). Outcomes were target joints, annual bleeding rate, annual joint bleeding rate, Hemophilia Joint Health Score, nonactivated thromboelastometry-rotational thromboelastometry clotting time, plasma emicizumab levels, and direct costs of treatment.

RESULTS

All outcome measures were significantly better in the low-dose emicizumab group than in the low-dose FVIII prophylaxis group. For nonactivated thromboelastometry-rotational thromboelastometry, median values after 6 months in the low-dose emicizumab group were comparable with values seen in patients with mild hemophilia, while the values in the low-dose FVIII prophylaxis group were similar to those of patients with moderate hemophilia. The direct cost of low-dose emicizumab was found to be approximately US $6000 and that for low-dose recombinant FVIII prophylaxis used in our study was US $6282 (the cost may range from US $3432 to $7920 depending on the type of factor) when compared to approximately US $15 000 for standard-dose emicizumab.

CONCLUSION

Low-dose emicizumab offers a cost-effective treatment option and can improve access in developing countries. These findings need to be confirmed in a larger and better-controlled study.

Clinical Analysis and Mental Health Survey of Hemophilia Carriers: a Cross-sectional Study

OBJECTIVE

Hemophilia carriers (HCs), who are heterozygous for mutations in the clotting factor VIII/clotting factor IX gene (F8 or F9), may have a wide range of clotting factor levels, from very low, similar to afflicted males, to the upper limit of normal, and may experience mental health issues. The purpose of this study was to provide genetic information on mothers of hemophilia patients and to understand the clotting factor activity and phenotype of HCs. Additionally, we aimed to investigate the mental health status of HCs in China.

METHODS

A total of 127 hemophilia mothers, including 93 hemophilia A (HA) mothers and 34 hemophilia B (HB) mothers, were enrolled in this study. Long distance PCR, multiplex PCR, and Sanger sequencing were used to analyze mutations in F8 or F9. Coagulation factor activity was detected by a one-stage clotting assay. The Symptom Checklist 90 (SCL-90, China/Mandarin version) was given to HCs at the same time to assess their mental health.

RESULTS

A total of 90.6% of hemophilia mothers were diagnosed genetically as carriers, with inversion in intron 22 and missense mutations being the most common mutation types in HA and HB carriers, respectively. The median clotting factor level in carriers was 0.74 IU/mL (ranging from 0.09 to 1.74 IU/mL) compared with 1.49 IU/mL (ranging from 0.93 to 1.89 IU/mL) in noncarriers, of which 14.3% of HCs had clotting factor levels of 0.40 IU/mL or below. A total of 53.8% (7/13) of HA carriers with low clotting factor levels (less than 0.50 IU/mL) had a history of bleeding, while none of the HB carriers displayed a bleeding phenotype. The total mean score and the global severity index of the SCL-90 for surveyed HCs were 171.00 (±60.37) and 1.78 (±0.59), respectively. A total of 67.7% of the respondents had psychological symptoms, with obsessive-compulsive disorder being the most prevalent and severe. The pooled estimates of all nine factors were significantly higher than those in the general population (P<0.05).

CONCLUSIONS

The detection rate of gene mutations in hemophilia mothers was 90.6%, with a median clotting factor level of 0.74 IU/mL, and 14.3% of HCs had a clotting factor level of 0.40 IU/mL or below. A history of bleeding was present in 41.2% of HCs with low clotting factor levels (less than 0.50 IU/mL). Additionally, given the fragile mental health status of HCs in China, it is critical to develop efficient strategies to improve psychological well-being.

Partial Splenic Embolization in a Patient with Hemophilia A and Severe Thrombocytopenia: A Case Report

We report a patient with hemophilia A who underwent partial splenic embolization (PSE) for severe thrombocytopenia secondary to portal hypertension-induced splenomegaly, resulting in a stable long-term quality of life. The patient was diagnosed with hemophilia A and unfortunately contracted human immunodeficiency virus (HIV), hepatitis B virus (HBV), and hepatitis C virus (HCV) from blood products. He subsequently developed progressive splenomegaly due to portal hypertension from chronic HCV, resulting in severe thrombocytopenia. PSE was performed because he had occasional subcutaneous bleeding and needed to start interferon (IFN) and ribavirin (RBV) treatment for curing his HCV infection at that time. His platelet counts increased, and no serious adverse events were observed. Currently, he continues to receive outpatient treatment, regular factor VIII (FVIII) replacement therapy for hemophilia A, and antiretroviral therapy for HIV infection. Vascular embolization has been reported to be an effective and minimally invasive treatment for bleeding in hemophilia patients. PSE also provided him with a stable quality of life without the side effects of serious infections and thrombocytopenia relapses. We conclude that PSE is a promising therapeutic option for patients with hemophilia A.

Whole F8 gene sequencing identified pathogenic structural variants in the remaining unsolved patients with severe hemophilia A

BACKGROUND

No F8 genetic abnormality is detected in approximately 1% to 2% of patients with severe hemophilia A (HA) using conventional genetic approaches. In these patients, deep intronic variation or F8 disrupting genomic rearrangement could be causal.

OBJECTIVES

The study aimed to identify the causal variation in families with a history of severe HA for whom genetic investigations failed.

METHODS

We performed whole F8 gene sequencing in 8 propositi. Genomic rearrangements were confirmed by Sanger sequencing of breakpoint junctions and/or quantitative polymerase chain reaction.

RESULTS

A structural variant disrupting F8 was found in each propositus, so that all the 815 families with a history of severe HA registered in our laboratory received a conclusive genetic diagnosis. These structural variants consisted of 3 balanced inversions, 3 large insertions of gained regions, and 1 retrotransposition of a mobile element. The 3 inversions were 105 Mb, 1.97 Mb, and 0.362 Mb in size. Among the insertions of gained regions, one corresponded to the insertion of a 34 kb gained region from chromosome 6q27 in F8 intron 6, another was the insertion of a 447 kb duplicated region from chromosome 9p22.1 in F8 intron 14, and the last one was the insertion of an Xq28 349 kb gained in F8 intron 5.

CONCLUSION

All the genetically unsolved cases of severe HA in this cohort were due to structural variants disrupting F8. This study highlights the effectiveness of whole F8 sequencing to improve the molecular diagnosis of HA when the conventional approach fails.

Immune tolerance promotion by LSEC-specific lentiviral vector-mediated expression of the transgene regulated by the stabilin-2 promoter

Liver sinusoidal endothelial cells (LSECs) are specialized endocytic cells that clear the body from blood-borne pathogens and waste macromolecules through scavenger receptors (SRs). Among the various SRs expressed by LSECs is stabilin-2 (STAB2), a class H SR that binds to several ligands, among which endogenous coagulation products. Given the well-established tolerogenic function of LSECs, we asked whether the STAB2 promoter (STAB2p) would enable us to achieve LSEC-specific lentiviral vector (LV)-mediated transgene expression, and whether the expression of this transgene would be maintained over the long term due to tolerance induction. Here, we show that STAB2p ensures LSEC-specific green fluorescent protein (GFP) expression by LV in the absence of a specific cytotoxic CD8+ T cell immune response, even in the presence of GFP-specific CD8+ T cells, confirming the robust tolerogenic function of LSECs. Finally, we show that our delivery system can partially and permanently restore FVIII activity in a mouse model of severe hemophilia A without the formation of anti-FVIII antibodies. Overall, our findings establish the suitability of STAB2p for long-term LSEC-restricted expression of therapeutic proteins, such as FVIII, or to achieve antigen-specific immune tolerance in auto-immune diseases.

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.

The spectrum of neutralizing and non-neutralizing anti-FVIII antibodies in a nationwide cohort of 788 persons with hemophilia A

Objectives

Anti-factor VIII (FVIII) antibodies have been reported to exhibit both neutralizing and non-neutralizing characteristics. This is the first study investigating the full spectrum of FVIII-specific antibodies, including non-neutralizing antibodies, very-low titer inhibitors, and inhibitors, in a large nationwide population of persons with hemophilia A of all severities.

Methods

All persons with hemophilia A (mild (FVIII > 5-40 IU/dL)/moderate [FVIII 1-5 IU/dL)/severe (FVIII < 1 IU/dL)] with an available plasma sample who participated in the sixth Hemophilia in the Netherlands study between 2018 and 2019 were included. The presence of anti-FVIII antibodies of the immunoglobulin A, M, and G isotypes and IgG subclasses, along with antibody titer levels, were assessed using direct-binding ELISAs. FVIII specificity was assessed using a competition-based ELISA approach. The inhibitor status was determined using the Nijmegen ultra-sensitive Bethesda assay (NusBA) and the Nijmegen Bethesda assay (NBA).

Results

In total, 788 persons with hemophilia A (336 (42.6%) mild, 123 (15.6%) moderate, 329 (41.8%) severe hemophilia) were included. The median age was 45 years (IQR 24-60), and the majority (50.9%) had over 150 exposure days to FVIII concentrates. Within our population, 144 (18.3%) individuals had non-neutralizing FVIII-specific antibodies, 10 (1.3%) had very low-titer inhibitors (NusBA positive; NBA negative), and 13 (1.6%) had inhibitors (both NusBA and NBA positive). IgG1 was the most abundant FVIII-specific antibody subclass, and the highest titer levels were found for IgG4. In individuals without a reported history of inhibitor development, no clear differences were observed in antibody patterns between those who were minimally or highly exposed to FVIII concentrates. IgG4 subclass antibodies were only observed in persons with a reported history of FVIII inhibitor or in those with a currently detected (very low-titer) inhibitor.

Conclusion

In this cross-sectional study, we identified non-neutralizing antibodies in a relatively large proportion of persons with hemophilia A. In contrast, in our population, consisting of persons highly exposed to FVIII concentrates, (very low-titer) inhibitors were detected only in a small proportion of persons, reflecting a well-tolerized population. Hence, our findings suggest that only a small subpopulation of non-neutralizing FVIII-specific antibodies is associated with clinically relevant inhibitors.

The effectiveness and safety of octocog alfa in patients with hemophilia A: up to 7-year follow-up of the real-world AHEAD international study

Background

Real-world data assessing treatment outcomes in patients with hemophilia A in routine clinical practice are limited.

Objective

To evaluate the effectiveness and safety of octocog alfa in patients with moderate/severe hemophilia A receiving treatment in clinical practice.

Design

The international Antihemophilic Factor Hemophilia A Outcome Database study is an observational, noninterventional, prospective, multicenter study.

Methods

This planned interim data read-out was conducted following 7 years of observation of patients receiving octocog alfa (cut-off, 30 June 2020). The primary endpoint was joint health status, assessed by the Gilbert Score. Secondary endpoints included annualized bleeding rates (ABRs), Hemophilia Joint Health Score (HJHS), health-related quality of life, consumption, and safety. This post hoc analysis stratified data by hemophilia severity at baseline [moderate, factor VIII (FVIII) 1-5%; severe, FVIII <1%].

Results

Of the 711 patients in this analysis, 582 (82%) were receiving prophylaxis with octocog alfa at enrollment, and 498 (70%) had severe disease. Median Gilbert Scores were higher with on-demand therapy versus prophylaxis and scores were comparable in moderate and severe disease. In patients receiving prophylaxis, there was an improvement in HJHS Global Gait Score over 7 years of follow-up overall and in patients with severe disease. ABRs and annualized joint bleeding rates were low across all 7 years. An ABR of zero was reported in 34-56% of prophylaxis patients versus 20-40% in the on-demand group. ABRs were similar in severe and moderate disease. In total, 13/702 (1.9%) patients experienced 18 treatment-related adverse events.

Conclusion

These data demonstrate the long-term effectiveness and safety of octocog alfa in patients with moderate and severe hemophilia A, especially in those receiving prophylaxis. The high number of patients receiving on-demand treatment experiencing zero bleeds could be due to selection bias within the study, with patients with less severe disease more likely to be receiving on-demand treatment.

Trial registration

ClinicalTrials.gov: NCT02078427.

Patient perspective on living with mild hemophilia in Germany: results from a nationwide survey

Introduction

The disease burden and bleeding risk of patients with mild hemophilia may be underestimated. Their health-related quality of life (QoL) may be negatively impacted by insufficient treatment and bleed-related joint damage connected to a potentially delayed diagnosis.

Aim

This study aims to gain information on the care reality and QoL of patients aged ≥12 years with mild hemophilia in Germany.

Methods

An anonymous cross-sectional patient survey using standardized questionnaires was conducted in a validated electronic patient-reported outcome system. Medical specialists, hemophilia centers, patient organizations, and support groups across Germany invited the patients.

Results

A total of 43 patients (35 patients with hemophilia A, 5 patients with hemophilia B, and 3 patients for whom the information was missing) with a median age of 33 years were analyzed. The median age at diagnosis was 6.0 years (interquartile range [IQR] 2.0-15.0), and the median factor activity was 14.0% (IQR 12.0-25.0). Nearly 85% of the patients received factor concentrates in the past, and the most common reasons for the treatment were surgery or joint bleeding (each 65.6%). Half of the patients who provided feedback experienced complications during bleeding episodes. Prophylactic treatment with factor concentrates was rare (10.3%). The patients had minor problems regarding their health status.

Conclusion

Bleeding complications and joint bleeding, in particular, may be highly underestimated in patients with mild hemophilia, highlighting a medical need in this population. Patients with a potential benefit from prophylaxis need to be identified. Mild hemophilia has a negative impact on patients' QoL. Hemophilia centers satisfied the patients' needs. Further research is needed to address the current lack of awareness and improve adequate treatment in the future.

De Novo Noninversion Variants Implicated in Sporadic Hemophilia A: A Variant Origin and Timing Study

Sporadic hemophilia A (HA) enables the persistence of HA in the population. F8 gene inversion originates mainly in male germ cells during meiosis. To date, no studies have shown the origin and timing of HA sporadic noninversion variants (NIVs); herein, we assume that HA-sporadic NIVs are generated as a de novo variant. Of the 125 registered families with HA, 22 were eligible for inclusion. We conducted a linkage analysis using F8 gene markers and amplification refractory mutation system-quantitative polymerase chain reaction to confirm the origin of the sporadic NIVs (~0% mutant cells) or the presence of a mosaic variant, which requires further confirmation of the origin in the parent. Nine mothers, four maternal grandmothers, and six maternal grandfathers were confirmed to be the origin of sporadic NIVs, which most likely occurred in the zygote within the first few cell divisions and in single sperm cells, respectively. Three mothers had mosaic variants, which most likely occurred early in postzygotic embryogenesis. All maternal grandparents were free from sporadic NIV. In conclusion, F8 NIVs in sporadic HA were found to be caused primarily by de novo variants. Our studies are essential for understanding the genetic pathogenesis of HA and improving current genetic counseling.

Effectiveness of emicizumab in preventing bleeding events in severe and moderate hemophilia A: A single-center experience in Bangladesh

Emicizumab is a monoclonal antibody that bridges activated factor IX (FIX) and factor X (FX) to replace the function of missing activated factor VIII (FVIII) in hemophilia A patients irrespective of FVIII inhibitor status. This study assessed the effectiveness of emicizumab in preventing bleeding episodes in patients with hemophilia A. This observational study included patients with moderate to severe hemophilia A who were undergoing episodic FVIII replacement therapy. The primary endpoint was the difference in annualized bleeding rates (ABR) and the secondary endpoint was the difference in Hemophilia Joint Health Score (HJHS) before and after emicizumab prophylaxis. A total of 30 male hemophilia patients were included, the mean age was 16.7 (SD: ±8.1) years, and most of them had moderate hemophilia A [63.3%]. Before prophylaxis, the median ABR was 48 (interquartile range [IQR]: 35-60), and 93.3% of patients had ABR greater than eight, whereas after prophylaxis the median ABR decreased significantly (median [IQR]: 0 [0.0-0.4], p < 0.001), and 56.7% had zero bleeds. ABR was not significantly different in patient with and without FVIII inhibitors. The HJHS scores significantly improved after prophylaxis (10 vs. 2.5, p < 0.001). The bleeding events were reduced significantly (23 vs. 0.0, p < 0.001), and zero new target joints were reported after prophylaxis. Most of the patients [93.3%] did not face any serious adverse events after prophylaxis. Emicizumab prophylaxis was associated with a significantly lower rate of bleeding events among participants with hemophilia A, regardless of inhibitor status.

A bispecific antibody NXT007 exerts a hemostatic activity in hemophilia A monkeys enough to keep a nonhemophilic state

BACKGROUND

Emicizumab, a factor (F) VIIIa-function mimetic bispecific antibody (BsAb) to FIXa and FX, has become an indispensable treatment option for people with hemophilia A (PwHA). However, a small proportion of PwHA still experience bleeds even under emicizumab prophylaxis, as observed in the long-term outcomes of clinical studies. A more potent BsAb may be desirable for such patients.

OBJECTIVES

To identify a potent BsAb to FIXa and FX, NXT007, surpassing emicizumab by in vitro and in vivo evaluation.

METHODS

New pairs of light chains for emicizumab's heavy chains were screened from phage libraries, and subsequent antibody optimization was performed. For in vitro evaluation, thrombin generation assays were performed with hemophilia A plasma. In vivo hemostatic activity was evaluated in a nonhuman primate model of acquired hemophilia A.

RESULTS

NXT007 exhibited an in vitro thrombin generation activity comparable to the international standard activity of FVIII (100 IU/dL), much higher than emicizumab, when triggered by tissue factor. NXT007 also demonstrated a potent in vivo hemostatic activity at approximately 30-fold lower plasma concentrations than emicizumab's historical data. In terms of dose shift between NXT007 and emicizumab, the in vitro and in vivo results were concordant. Regarding pharmacokinetics, NXT007 showed lower in vivo clearance than those shown by typical monoclonal antibodies, suggesting that the Fc engineering to enhance FcRn binding worked well.

CONCLUSION

NXT007, a potent BsAb, was successfully created. Nonclinical results suggest that NXT007 would have a potential to keep a nonhemophilic range of coagulation potential in PwHA or to realize more convenient dosing regimens than emicizumab.

Interim analyses of the multinational real-world prospective cohort HEM-POWR study evaluating the effectiveness and safety of damoctocog alfa pegol in patients with hemophilia A

OBJECTIVES

To assess effectiveness and safety of damoctocog alfa pegol in interim analyses of the ongoing real-world hemophilia A HEM-POWR study.

METHODS

HEM-POWR (NCT03932201) is a multinational Phase 4 prospective observational study. The primary objective was annualized bleeding rate (ABR) in previously treated patients (PTPs) with hemophilia A. Secondary objectives included adverse events and number of affected joints.

RESULTS

At data cut-off (August 17, 2022), the safety analysis set included 268 patients and the full analysis set (FAS) included 161 patients. The most common dosing regimen during observation period was prophylaxis (FAS = 158/161, 98.1%) every 3-4 days (twice weekly; FAS = 78/158, 49.4%) and a median (min, max) infusion dose of 37.5 (10, 72) IU/kg. PTPs receiving prophylactic damoctocog alfa pegol have fewer infusions compared with prior treatment. Median total ABR (Q1, Q3) was 0.0 (0.0, 1.8) and mean total ABR (SD) was 2.4 (8.2). The proportion of patients with no affected joints increased between initial visit and follow-up. No FVIII inhibitors, treatment-related adverse events, or deaths were reported.

CONCLUSIONS

Damoctocog alfa pegol shows effectiveness and acceptable safety, as well as consistent utilization, in real-world PTPs with hemophilia A, including in patients with non-severe hemophilia and those with a history of inhibitors. Please see video for a summary of this study.

Arthropathy on X-rays in 363 persons with hemophilia: long-term development, and impact of birth cohort and inhibitor status

Background

Arthropathy following repeated bleeding is common in persons with hemophilia. Since the introduction of prophylaxis, treatment has intensified and joint health has improved. However, data on the long-term development of arthropathy are still scant.

Objectives

To evaluate long-term arthropathy development since the introduction of prophylaxis according to birth cohort, hemophilia severity, and inhibitor status.

Methods

This single-center historic cohort study included persons with severe and moderate hemophilia A and hemophilia B born between 1935 and 2005. Arthropathy on X-rays was evaluated using the Pettersson score. Patient and joint characteristics were studied per birth cohort (<1970, 1970-1980, 1981-1990, and >1990) and compared according to hemophilia severity. The distribution of affected joints and cumulative incidence of arthropathy were analyzed. The association of Pettersson score with birth cohort and inhibitor characteristics was explored using multivariable regression analyses adjusted for age at evaluation.

Results

In total, 1064 X-rays of 363 patients were analyzed. Of persons with severe hemophilia (n = 317, 87.3%), 244 (77.0%) developed arthropathy. Prophylaxis was started at younger ages over time, from a median of 18 to 2.1 years, and concomitantly, arthropathy decreased in consecutive birth cohorts. Ankles were most commonly affected in 188 of 258 (72.9%) patients. Persons with moderate hemophilia (n = 46, 12.7%) had a lower risk of arthropathy (27/46 [58.7%]), but a reduction over time was less pronounced. In the multivariable analyses, birth cohort and age at evaluation were predictors for the development of arthropathy, while inhibitor status showed no association.

Conclusion

The development and severity of arthropathy have decreased over the past decades. However, patients have remained at risk for developing arthropathy, especially in their ankles.

Long-term outcomes with emicizumab in hemophilia A without inhibitors: results from the HAVEN 3 and 4 studies

Background

Emicizumab, a bispecific monoclonal antibody, bridges activated factor (F) IX and FX, mimicking the function of missing or deficient activated FVIII in people with hemophilia A (HA).

Objectives

To evaluate the long-term efficacy and safety of emicizumab prophylaxis in people with HA without FVIII inhibitors in the HAVEN 3 and 4 studies.

Methods

HAVEN 3 and 4 were phase 3 open-label studies. Participants received emicizumab maintenance doses of 1.5 mg/kg every week or 3 mg/kg every 2 weeks (HAVEN 3), or 6 mg/kg every 4 weeks (HAVEN 4). Long-term efficacy and safety were assessed.

Results

A total of 151 and 40 individuals without FVIII inhibitors received emicizumab in HAVEN 3 and 4, respectively. At the last patient, last visit dates (May 12, 2022 [HAVEN 3] and June 29, 2022 [HAVEN 4]), the median (range) duration of emicizumab exposure across the 2 studies was 248.1 (6.1-287.1) weeks. The mean (95% CI) annualized bleed rate for treated bleeds was 2.0 (0.23-7.15) for weeks 1 to 24, decreasing to 0.9 (0.01-5.28) by weeks 217 to 240. Overall, 188 (98.4%) participants experienced ≥1 adverse event (AE), with 185 treatment-related AEs in 71 (37.2%) participants. Forty-four (23.0%) participants reported a serious AE. Two thromboembolic events were reported, which were deemed unrelated to emicizumab by the investigator. No thrombotic microangiopathies were reported.

Conclusion

With nearly 5 years of emicizumab exposure across the HAVEN 3 and 4 studies in people with HA without inhibitors, these data indicate continued bleed control with no new safety signals observed during long-term follow-up.

Balancing anticoagulation and hemostasis in an infant with severe hemophilia A during cardiac transplantation: Review of the literature and development of a surgical protocol

Hemophilia A is a disorder resulting in a deficiency of clotting factor VIII that can lead to life-threatening bleeding. Evidence-based guidelines for surgical interventions like cardiac surgery are limited. Anticoagulation is necessary for cardiac bypass, thus risk of bleeding in a patient with hemophilia is increased and requires careful attention to maintain hemostasis. We report the first infant with severe hemophilia A and dilated cardiomyopathy who underwent successful cardiac transplantation, and review the literature on previous cardiac transplant cases in congenital hemophilia. To ensure safe and effective management, a multidisciplinary approach was used to develop the surgical protocol for transplant.

Platelet-targeted gene therapy induces immune tolerance in hemophilia and beyond

Blood platelets have unique storage and delivery capabilities. Platelets play fundamental roles in hemostasis, inflammatory reactions, and immune responses. Beyond their functions, platelets have been used as a target for gene therapy. Platelet-targeted gene therapy aims to deliver a sustained expression of neo-protein in vivo by genetically modifying the target cells, resulting in a cure for the disease. Even though there has been substantial progress in the field of gene therapy, the potential development of immune responses to transgene products or vectors remains a significant concern. Of note, multiple preclinical studies using platelet-specific lentiviral gene delivery to hematopoietic stem cells in hemophilia have demonstrated promising results with therapeutic levels of neo-protein that rescue the hemorrhagic bleeding phenotype and induce antigen-specific immune tolerance. Further studies using ovalbumin as a surrogate protein for platelet gene therapy have shown robust antigen-specific immune tolerance induced via peripheral clonal deletions of antigen-specific CD4- and CD8-T effector cells and induction of antigen-specific regulatory T (Treg) cells. This review discusses platelet-targeted gene therapy, focusing on immune tolerance induction.

A case study on using an intrauterine foley catheter to reduce postpartum bleeding in a patient with hemophilia

Case of a pregnant patient suffering from severe hemophilia A who had effective uterine foley tamponade to treat postpartum hemorrhage.

Pharmacokinetics and coagulation biomarkers in children and adults with hemophilia A receiving emicizumab prophylaxis every 1, 2, or 4 weeks

Background

Emicizumab is a bispecific antibody that bridges activated factor (F)IX and FX, mimicking the function of missing activated FVIII and thus improving hemostasis in people with hemophilia A. The efficacy and safety of emicizumab were demonstrated in 4 phase III clinical trials (HAVEN 1-4).

Objectives

Here, we describe pharmacokinetics (PKs), pharmacodynamics (PDs), and exploratory safety biomarkers in HAVEN 1 to 4.

Methods

Participants received emicizumab at a loading dose of 3 mg/kg weekly for 4 weeks, followed by maintenance doses of 1.5 mg/kg weekly, 3 mg/kg every 2 weeks, or 6 mg/kg every 4 weeks. PKs, PDs, and safety biomarkers were assessed in samples collected at regular intervals during the trials.

Results

Emicizumab plasma trough concentrations increased during the loading dose period, reaching a mean of 52.9 μg/mL (SD, 13.6 μg/mL) at week 5, and were sustained at 42.1 to 52.3 μg/mL thereafter with maintenance dosing. Activated partial thromboplastin time shortened following the first emicizumab dose. Mean FVIII-like activity and thrombin generation peak height increased to 25.2 IU/dL (SD, 6.9 IU/dL) and 115.2 nM (SD, 42.5 nM) at week 5, with levels sustained at 17 to 23 IU/dL and >116 nM thereafter, respectively. Emicizumab did not notably affect FIX or FX plasma antigen levels, prothrombin time, or concentrations of exploratory safety markers of coagulation activation (D-dimer, prothrombin fragment 1 + 2, and fibrinogen).

Conclusion

In HAVEN 1 to 4, emicizumab demonstrated sustained PKs and PDs and improved coagulation parameters without affecting safety biomarkers.

Patients with moderate hemophilia A and B with a severe bleeding phenotype have an increased burden of disease

BACKGROUND

Patients with moderate hemophilia express varying bleeding phenotypes.

OBJECTIVES

To assess the burden of disease in patients with moderate hemophilia and a mild or severe phenotype incorporating the thrombin generation profile.

METHODS

This sub-study of the 6th Hemophilia in the Netherlands study, analyzed data of adults with moderate hemophilia A or B. Patient characteristics and information on bleeding tendency, joint status, and quality of life were obtained from electronic patient files and self-reported questionnaires. A severe bleeding phenotype was defined as an annual bleeding rate ≥5, an annual joint bleeding rate ≥3, and/or the use of secondary/tertiary prophylaxis, and a mild phenotype vice versa. TG was measured with the Nijmegen Hemostasis Assay.

RESULTS

This study included 116 patients: 21% had a severe phenotype of whom 46% used prophylaxis. Patients with a severe phenotype treated on demand reported a higher median annual bleeding rate (7), annual joint bleeding rate (3), and more frequently an impaired joint (77%) than patients with a severe phenotype on prophylaxis (2; 0; 70%) or patients with a mild phenotype (0; 0; 47%). Furthermore, patients with a severe phenotype treated on demand experienced a more decreased quality of life. Despite similar factor activity levels, patients with a severe phenotype had a lower thrombin peak height and thrombin potential (0.7%; 0.06%) than patients with a mild phenotype (21.3%; 46.8%).

CONCLUSION

Patients with moderate hemophilia and a severe phenotype treated on demand displayed a high burden of disease as well as a low thrombin generation profile advocating them toward more intensive prophylactic treatment.

Mice possess a more limited natural antihuman factor VIII antibody repertoire than humans that is produced disproportionately by marginal zone B cells

BACKGROUND

One-third of patients with severe hemophilia A develop neutralizing antibodies to the factor VIII (FVIII) protein in response to intravenous replacement therapy. Patients may also generate natural, nonneutralizing antibodies to FVIII before FVIII exposure. These patients are at increased risk of developing neutralizing antibodies to FVIII. However, natural anti-FVIII antibodies are also present in healthy human donors.

OBJECTIVES

To further characterize the natural antihuman (h) FVIII antibody repertoire in mice and humans.

METHODS

An in-house ELISA was developed using a purified polyclonal immunoglobulin (Ig) standard to quantify anti-hFVIII Ig in cell culture supernatant or plasma from mice (wild-type and FVIII-/-) and adult human donors.

RESULTS

All naïve wild-type and FVIII-/- mice, as well as healthy human donors, possess natural anti-hFVIII antibodies. Mice only have natural anti-hFVIII IgM, which is present in germ-free mice, suggesting that they are germline encoded. Although murine marginal zone B cells (MZBs) contribute 44% to all circulating natural IgM, they contribute disproportionately to the anti-hFVIII IgM repertoire (82%). This naturally occurring murine MZB-derived IgM is not B-domain specific and is reduced by intravenously administered hFVIII, suggesting that it may form immune complexes immediately upon hFVIII administration. Natural anti-hFVIII antibodies of IgG, IgM, and IgA isotypes can be detected in adult human donors. There were increased levels of B-domain-favoring anti-hFVIII IgG in 14% of healthy donors, which were markedly different from the rest of the "low-titer" population.

CONCLUSIONS

There is a preponderance of natural anti-hFVIII antibodies in both mice and healthy adult human donors.

Hybrid human-porcine factor VIII proteins partially escape the inhibitory effects of anti-factor VIII inhibitor alloantibodies having A2 or C2 domain specificity

INTRODUCTION

Porcine factor (pF)VIII has low cross-reactivity with anti-human (h)FVIII inhibitor alloantibodies. Clinical trials of pFVIII in congenital haemophilia A patients with inhibitor (PwHA-I) are in progress. Most polyclonal anti-hFVIII inhibitors recognize its A2 and/or C2 domain(s), and recombinant human-porcine hybrid (hp)FVIII proteins may escape neutralization by these inhibitors.

AIM

To evaluate the ability of hpFVIII to limit the anti-FVIII activity of inhibitor alloantibodies.

METHODS

Three hybrid proteins were created by substituting the hFVIII A2, C2 domain or both with the corresponding domains of pFVIII [termed hp(A2), hp(C2) and hp(A2/C2), respectively]. The reactivity of these hybrids was assessed by one-stage clotting assays (OSA), thrombin generation assays (TGA) and rotational thromboelastometry (ROTEM) by adding them to FVIII-deficient samples.

RESULTS

OSA demonstrated that the hybrid proteins avoided neutralization by anti-FVIII A2 or C2 monoclonal antibodies (mAb) and polyclonal inhibitor-antibodies (polyAb) from PwHA-I. In TGA, thrombin generation with hp(A2) and hp(A2/C2) was not attenuated in the presence of patient IgG recognizing anti-A2 domain. In contrast, that with hFVIII and hp(C2) was suppressed by this IgG to levels equivalent to those of FVIII-deficient plasma. With anti-A2/C2 polyAb, the activity of hp(A2/C2) was unaffected. ROTEM demonstrated that the addition of hp(A2) or hp(A2/C2) to anti-A2 polyAb shortened clot times/clot formation times, whilst hFVIII or hp(C2) were ineffective. Similarly with anti-A2/C2 polyAb, hp(A2/C2) restored coagulation potential to a greater extent than hp(A2) and hp(C2).

CONCLUSION

Hybrid FVIII proteins containing porcine FVIII A2 and/or C2 domain(s) could support effective therapy in PwHA-I by avoiding neutralization.

Surgical Experience from the STASEY Study of Emicizumab Prophylaxis in People with Hemophilia A with Factor VIII Inhibitors

Background  Guidelines surrounding emicizumab prophylaxis and perioperative treatment for people with hemophilia A (PwHA) with factor (F)VIII inhibitors undergoing surgeries are limited. The phase IIIb multicenter, single-arm STASEY study evaluated safety and tolerability of emicizumab prophylaxis in PwHA aged ≥12 years with FVIII inhibitors. This analysis assesses surgeries during study conduct, associated hemophilia medications, and postoperative bleeds (treated and untreated). Methods  PwHA with FVIII inhibitors received emicizumab 3.0 mg/kg/week for 4 weeks, then 1.5 mg/kg/week until 2 years. Surgeries were managed and documented by treating physicians. Bleeds and treatments were recorded by physicians and participants. Results  Forty-six participants had ≥1 on-study surgery, 37 underwent 56 minor surgeries, and 13 underwent 22 major surgeries. Four participants underwent both minor and major surgeries. Of 18 (81.8%) and 4 (18.2%) major surgeries managed with/without additional hemostatic medication, 33.3 and 25.0% were associated with a treated postoperative bleed, respectively. Of 24 (42.9%) and 32 (57.1%) minor surgeries managed with/without additional hemostatic medication, 15.6 and 25.0% were associated with a treated postoperative bleed, respectively. Recombinant activated FVII was the most common medication for prophylaxis and bleed treatment. There were no thrombotic microangiopathies (TMAs). One hypertrophic clot, considered unrelated to emicizumab, occurred following tooth extraction. Conclusion  In this challenging population with a high bleeding risk, major surgeries were performed in PwHA receiving emicizumab with/without additional hemostatic medication. Postoperative bleeds occurred following 59.1% of major surgeries; 53.8% were treated. No arterial/venous thrombotic events or TMAs occurred due to concomitant emicizumab and bypassing agents. Trial registration  This trial is registered at ClinicalTrials.gov (NCT03191799).

Emicizumab Prophylaxis in Patients with Severe Hemophilia A: Insights from A Resource Limited Country

METHODS

In this prospective study, severe HA patients were recruited from January 2022 to June 2023. Inhibitor positive and inhibitor negative patients with annual bleeding rate (ABR) 8 or greater and past histories of bleeding like intra-cranial, intra-abdominal, and pseudo-tumors were included. Emicizumab loading dose was 3 mg/kg in the first 4 weeks, and the maintenance dose was started at week 5 at 6 mg/kg/month. Patients' detailed bleeding history and demographics were recorded. The five-level EuroQol five-dimensional questionnaire (EQ-5D-5L) was used to evaluate patients' HRQoL. Furthermore, Hemophilia Joint Health Score (HJHS) and Functional Independence score in Hemophilia (FISH) were applied for the assessment of joints at different time points. Results were analyzed by SPSS version 21.

RESULTS

A total of 36 HA male patients with the mean age of 19.7 ± 14.42 years were recruited in the study; among them, 19 patients were inhibitor positive, while 17 were negative. Patients clinically presented with bleeding symptoms which included: hemarthrosis 95%, GI bleeding 13.8%, and bruises and gums bleeding 13.8%. Significant reduction was observed in the bleeding episodes after the therapeutic intervention, and joints assessment and Euro-Quality-of-life Visual Analog Scale showed a significant improvement in health after treatment. Similarly, there was a remarkable reduction in bleeding episodes and improved quality of life among HA patients. The ABR decreased from 53.6% episodes per year prior to treatment to 2.4% during Emicizumab therapy. Prior to initiating Emicizumab therapy, participants exhibited an average FISH score of 16 and HJHS score of 10, indicating moderate limitations due to joint-related issues. After treatment, the mean FISH score improved to 9 and HJHS score to 4 reflecting a substantial enhancement in participants' ability to perform daily activities (P < 0.057).

CONCLUSION

Our results showed that HA patients on prophylactic treatment with Emicizumab were less restricted and had improved quality of life due to marked decrease in bleeding episodes which resulted in improved health and social lives. In addition, it was well tolerated, and no participant discontinued treatment because of adverse events.

NXT007-mediated hemostatic potential is suppressed by activated protein C-catalyzed inactivation of activated factor V

Background

Activated protein C (APC) inactivates activated factor (F) V (FVa) and FVIIIa. NXT007, an emicizumab-based engineered therapeutic bispecific antibody, enhances the coagulation potential of FVIII-deficient plasma (FVIIIdef-plasma) to near normal levels. However, little is known about the effect of APC-induced inactivation in NXT007-mediated hemostatic function.

Objectives

To investigate the contribution of APC-mediated reactions to NXT007-driven hemostasis.

Methods

In pooled normal plasma (PNP) or FVIIIdef-plasma spiked with NXT007 (10 μg/mL), effects of APC (0-16 nM) were measured using a thrombin generation assay (TGA). The direct effects of APC on cofactor activity of NXT007 or FVIIIa in a FXa generation assay were also measured. The FVdef-plasma and FV Leiden plasma (FVLeiden plasma) were preincubated with 2 anti-FVIII monoclonal antibodies (termed FVIII-depleted), and the APC effect in the presence of NXT007 in FVIII-depleted FVdef-plasma with the addition of exogenous FV (7.5-30 nM) or FVIII-depleted FVLeiden plasma was investigated.

Results

The APC dose-dependent suppression effect in TGA of FVIIIdef-plasma spiked with NXT007 was similar to that of PNP. FXa generation with NXT007 was not impaired by the addition of APC, suggesting that the APC-induced reaction in TGA with NXT007 was attributed to the direct inactivation of FVa. The addition of APC to FVIII-depleted FVdef-plasma, along with NXT007 and various FV concentrations, showed a similar attenuation to PNP. The NXT007-driven thrombin generation in FVIII-depleted FVLeiden plasma was suppressed by APC, similar to the reaction in native FVLeiden plasma.

Conclusion

NXT007 did not impair APC-mediated downregulation of FVa in FVIIIdef-plasmas, regardless of the presence of FV mutation with APC resistance.

Personalized Prophylaxis with myPKFiTCE: A Real-World Cost-Effectiveness Analysis in Haemophilia A Patients

Background and Objectives: This study aimed to assess the effectiveness and costs associated with pharmacokinetics-driven (PK) prophylaxis based on the myPKFiT® device in patients affected by hemophilia A (HA) in Italy. Materials and Methods: An observational retrospective study was conducted in three Italian hemophilia centers. All patients with moderate or severe HA, aged ≥ 18 years, capable of having PK estimated using the myPKFiT device, and who had had a clinical visit between 1 November 2019 and 31 March 2022 were included. Differences in clinical, treatment, health resources, and cost data were assessed comparing post-PK prophylaxis with pre-PK. The incremental cost-effectiveness ratio (ICER) was estimated as cost (EUR) per bleed avoided. Results: The study enrolled 13 patients with HA. The mean annual bleeding rate decreased by -1.45 (-63.80%, p = 0.0055) after the use of myPKFiT®. Overall, the consumption of FVIII IU increased by 1.73% during follow-up compared to the period prior the use of the myPKFiT. Prophylaxis based on the myPKFiT resulted in an ICER of EUR 5099.89 per bleed avoided. Conclusions: The results of our study support the idea that the use of PK data in clinical practice can be associated with an improvement in the management of patients, as well as clinical outcomes, with a reasonable increase in costs.

Induction of long-term tolerance to a specific antigen using anti-CD3 lipid nanoparticles following gene therapy

Development of factor VIII (FVIII) inhibitors is a serious complication in the treatment of hemophilia A (HemA) patients. In clinical trials, anti-CD3 antibody therapy effectively modulates the immune response of allograft rejection or autoimmune diseases without eliciting major adverse effects. In this study, we delivered mRNA-encapsulated lipid nanoparticles (LNPs) encoding therapeutic anti-CD3 antibody (αCD3 LNPs) to overcome the anti-FVIII immune responses in HemA mice. It was found that αCD3 LNPs encoding the single-chain antibodies (Fc-scFv) can efficiently deplete CD3+ and CD4+ effector T cells, whereas αCD3 LNPs encoding double-chain antibodies cannot. Concomitantly, mice treated with αCD3 (Fc-scFv) LNPs showed an increase in the CD4+CD25+Foxp3+ regulatory T cell percentages, which modulated the anti-FVIII immune responses. All T cells returned to normal levels within 2 months. HemA mice treated with αCD3 LNPs prior to hydrodynamic injection of liver-specific FVIII plasmids achieved persistent FVIII gene expression without formation of FVIII inhibitors. Furthermore, transgene expression was increased and persistent following secondary plasmid challenge, indicating induction of long-term tolerance to FVIII. Moreover, the treated mice maintained their immune competence against other antigens. In conclusion, our study established a potential new strategy to induce long-term antigen-specific tolerance using an αCD3 LNP formulation.

Functional determination of emicizumab in presence of factor VIII activity

BACKGROUND

Accurate measurement of emicizumab in the presence of factor (F) VIII is required in patients with severe hemophilia A treated with emicizumab, as well as additional need for FVIII substitution or emicizumab prophylaxis in patients with acquired or moderate to mild hemophilia A. However, the presence of FVIII potentially biases the results.

OBJECTIVES

To assess the impact of plasma FVIII activity on determined emicizumab levels and evaluate different strategies for correction for or preanalytical inhibition of FVIII.

METHODS

Evaluated strategies comprised of the following: (1) calculation of actual emicizumab plasma levels based on measured FVIII activities and FVIII-affected emicizumab values, (2) preanalytical heat treatment (56 °C for 40 minutes), and (3) neutralization of FVIII activity using FVIII inhibitors. Emicizumab levels and FVIII activities were measured using a modified FVIII one-stage clotting assay and a chromogenic FVIII assay based on bovine factors, respectively.

RESULTS

Spiking experiments revealed a consistent linear association between FVIII activities and determined (FVIII-affected) emicizumab results at different emicizumab input levels (∼0.12 μg/mL per IU/dL of FVIII). This principally allowed for mathematical correction of measured emicizumab levels in the presence of FVIII. While a 40% to 50% activity loss of intrinsic plasma emicizumab through heat treatment was observed in patient samples, emicizumab spiked into FVIII-deficient plasma was not or only marginally affected. Application of inhibitor-based FVIII neutralization led to good agreement of results when compared with direct quantification of emicizumab by liquid chromatography-tandem mass spectrometry.

CONCLUSION

Inhibitor-based FVIII neutralization appears to be a feasible strategy for accurate measurement of plasma emicizumab levels in the presence of FVIII activity.

Emicizumab prophylaxis for people with hemophilia A: Waste estimation and the Brazilian perspective

Costs of hemophilia A treatment are increasing. Waste of clotting products should be avoided. To estimate the first-year waste of emicizumab prophylaxis for people with hemophilia A and inhibitors (PwHAi) who failed immune tolerance induction (ITI), in Brazil. We evaluated the manufacturer and the Brazilian Ministry of Health (MoH) protocol-recommended regimens in a budget impact model. The loading dose consisted of 3.0 mg/kg/Q1W for 4 weeks, for both recommendations. The manufacturer maintenance regimens comprised 1.5 mg/kg/Q1W, 3.0 mg/kg/Q2W, and 6.0 mg/kg/Q4W. The MoH protocol maintenance regimen encompassed a hybrid Q1W/Q2W administration, depending on the body weight. The Q4W regimen was not recommended by the MoH protocol. Analyses were performed to estimate waste given its expense based on the World Health Organization body weight range (percentiles [P] 15, 50, and 85). The first-year emicizumab waste was estimated individually and for the disclosed PwHAi who failed ITI (n = 114). The highest emicizumab waste was estimated for the lowest body weights and the Q1W regimen. The Q4W regimen resulted in the lowest emicizumab waste, followed by the MoH protocol regimen. The total reconstituted costs estimated for the PwHAi who failed ITI according to the hybrid MoH protocol ranged from US$32,858,777 (P15) to US$47,186,858 (P85), with emicizumab waste ranging from 7.9 % (US$2,594,515) to 3.7 % (US$1,738,750), respectively. Lost resources due to current protocols for emicizumab prophylaxis for PwHAi who failed ITI in Brazil are considerable. Waste was more pronounced due to lower body weight and shorter administration intervals.

Cellular stress and coagulation factor production: when more is not necessarily better

Remarkably, it has been 40 years since the isolation of the 2 genes involved in hemophilia A (HA) and hemophilia B (HB), encoding clotting factor (F) VIII (FVIII) and FIX, respectively. Over the years, these advances led to the development of purified recombinant protein factors that are free of contaminating viruses from human pooled plasma for hemophilia treatments, reducing the morbidity and mortality previously associated with human plasma-derived clotting factors. These discoveries also paved the way for modified factors that have increased plasma half-lives. Importantly, more recent advances have led to the development and Food and Drug Administration approval of a hepatocyte-targeted, adeno-associated viral vector-mediated gene transfer approach for HA and HB. However, major concerns regarding the durability and safety of HA gene therapy remain to be resolved. Compared with FIX, FVIII is a much larger protein that is prone to misfolding and aggregation in the endoplasmic reticulum and is poorly secreted by the mammalian cells. Due to the constraint of the packaging capacity of adeno-associated viral vector, B-domain deleted FVIII rather than the full-length protein is used for HA gene therapy. Like full-length FVIII, B-domain deleted FVIII misfolds and is inefficiently secreted. Its expression in hepatocytes activates the cellular unfolded protein response, which is deleterious for hepatocyte function and survival and has the potential to drive hepatocellular carcinoma. This review is focused on our current understanding of factors limiting FVIII secretion and the potential pathophysiological consequences upon expression in hepatocytes.

Pharmacokinetic-guided versus standard prophylaxis in hemophilia: a systematic review and meta-analysis

BACKGROUND

With population pharmacokinetic (PK) modeling more readily available and PK-guided prophylaxis endorsed by current hemophilia guidelines, we conducted a systematic review to summarize current evidence in the literature.

OBJECTIVES

To assess the efficacy of PK-guided compared with non-PK-guided prophylaxis.

METHODS

We did not restrict inclusion to specific study design labels and included all studies consisting of at least one distinct cohort arm receiving PK-guided prophylaxis. We searched the following databases from inception to date of search: MEDLINE, Embase, CENTRAL, ClinicalTrials.gov, and the EU Clinical Trial Register. Following title, abstract, and full-text screening conducted independently by 2 review authors, we summarized studies qualitatively and synthesized included randomized clinical trials (RCTs) quantitatively by fitting random-effects models.

RESULTS

Search of databases on February 3, 2023, yielded 25 studies fitting our inclusion criteria. Of those, only 2 RCTs and 17 nonrandomized studies included a standard prophylaxis comparator group. Furthermore, risk of bias in the latter was substantial, primarily due to before-after study designs and retrospective comparator groups. Thus, nonrandomized studies were only presented qualitatively. A random-effects meta-analysis of the 2 identified RCT remained inconclusive with regards to bleeding outcomes (ratio of means, 1.15; 95% CI, 0.85-1.56) and factor consumption (ratio of means, 0.82; 95% CI, 0.58-1.18).

CONCLUSION

Evidence in the literature suggesting a clinical benefit of PK-guided over standard fixed-dose prophylaxis was weak and mainly found in nonrandomized studies limited by lack of concurrent controls, heterogeneity in outcome reporting, small sample sizes, and high risk of bias.

Health-related quality of life following valoctocogene roxaparvovec gene therapy for severe hemophilia A in the phase 3 trial GENEr8-1

BACKGROUND

Severe hemophilia A (HA) negatively impacts health-related quality of life (HRQOL).

OBJECTIVES

We aimed to analyze HRQOL in adult men with severe HA without inhibitors after valoctocogene roxaparvovec gene transfer in the phase 3 trial GENEr8-1.

METHODS

Participant-reported outcomes were the hemophilia-specific quality of life questionnaire for adults (Haemo-QOL-A), the EQ-5D-5L instrument, the Hemophilia Activities List (HAL), and the Work Productivity and Activity Impairment Questionnaire: Hemophilia Specific (WPAI+CIQ:HS). Participants completed the questionnaires at baseline and through 104 weeks postinfusion with 6 × 1013 vg/kg of valoctocogene roxaparvovec. Scores were analyzed per participant characteristics and outcomes.

RESULTS

For 132 HIV-negative participants, mean change from baseline in Haemo-QOL-A Total Score met the anchor-based clinically important difference (CID: 5.5) by week 12; the mean (SD) increase was 7.0 (12.6) at week 104. At week 104, improvement in Consequences of Bleeding, Treatment Concern, Worry, and Role Functioning domain scores exceeded the CID (6). EQ-5D-5L Utility Index scores improved above the CID at week 52, but not at week 104. EQ-5D-5L visual analog scale and HAL scores increased from baseline to week 104. Participants reported less activity and work impairment at week 104 than baseline. Participants with problem joints had lower mean baseline Haemo-QOL-A Total and domain scores than those without them, but improved over 104 weeks, except for 11 participants with ≥3 problem joints. Participants with 0 bleeds during the baseline prophylaxis period reported Haemo-QOL-A score improvements above the CID, including in the Consequences of Bleeding domain.

CONCLUSION

Valoctocogene roxaparvovec provided clinically meaningful HRQOL improvement for men with severe HA.

Real-World Experience of People with Hemophilia A Receiving Turoctocog Alfa Pegol (N8-GP): Results from a Patient Experience Survey

Purpose

Turoctocog alfa pegol (N8-GP) is an extended half-life recombinant factor VIII molecule used for the treatment of hemophilia A (HA). The purpose of this study was to investigate real-world experiences of patients with HA treated with N8-GP.

Patients and Methods

A 25-minute online survey was completed by adults (≥18 years) and caregivers of adolescents (12-16 years) with HA receiving N8-GP across six countries (Germany, Italy, Portugal, Spain, UK and US). Patients were recruited using a multichannel approach through recruitment panels, referrals from healthcare professionals and patient associations. The survey comprised a questionnaire with metrics including satisfaction and preferences for N8-GP, quality of life (QoL) and long-term impact.

Results

A total of 62 participants (98% male [n=61], mean age 29 years) comprising 46 patients and 16 caregivers completed the survey. Patients (60% non-severe [n=37] and 40% severe [25]) were on N8-GP for a mean period of 1.4 years. Patients expressed satisfaction (95% vs 42%, p<0.001) and preference (91% vs 9%, p<0.001) for N8-GP vs their previous treatments. Most patients with severe HA (87%, p=0.038) and patients on prophylaxis (84%, p<0.001) stated lower frequency of injections as their main reason for satisfaction, while improved QoL drove satisfaction for non-severe patients (81%, p=0.053). Overall, patients perceived that QoL score improved (74.8 vs 65.9, p=0.01) with N8-GP treatment compared with previous treatments. Flexibility to store at room temperature was one of the key convenience factors driving satisfaction. Patients believed that N8-GP can offer a long-term impact in areas such as ability to perform day-to-day activities (68%), independence to live like a person without hemophilia (63%), ability to travel (60%) with a feeling of optimism and hopefulness (82%).

Conclusion

Lower frequency of injections, storage flexibility and improved QoL drove satisfaction and preference for N8-GP over previous treatments among patients with HA.

A Panoramic X-ray as a Supportive Diagnostic Tool for the Screening of Osteoporosis in Patients with Hemophilia A and B

BACKGROUND

Hemophilia is associated with an increased risk of developing osteoporosis and osteopenia. The aim of the study was to interpret the usefulness of fractal analysis of the trabecular bone of the mandible (FD) and selected radiomorphic indices (the antegonial index (AI) and Klemetti index (KI)) to assess the risk of reduced bone mineral density (BMD) in patients with hemophilia A/B.

METHODS

The study group consisted of 50 patients with type A/B hemophilia. The control group consisted of 25 males without congenital bleeding disorders. The patients had a panoramic radiograph taken with the same X-ray machine (Vistapano S, Durr Dental, Bietigheim-Bissingen, Germany). The AudaXCeph software (Audax d.o.o., Ljubljana, Slovenia) was used to evaluate the AI index, and the ImageJ, software with a specially prepared script, was used to evaluate the FD. The mandibular cortex was assessed distal to the mental foramen using the Klemetti index.

RESULTS

There were no statistically significant differences between the AI, KI and FD values between the study group and the control group.

CONCLUSIONS

This study indicated the lack of usefulness of AI, KI and fractal analysis in identifying patients with hemophilia at risk of reduced bone mass.

Serious bleeds in pediatric persons with hemophilia A on emicizumab prophylaxis

Background

Clinical trials have shown success in bleed prevention with emicizumab, but real-world data on the effectiveness of emicizumab in preventing serious bleeds in the pediatric population are lacking.

Objectives

To report real-world data on the effectiveness of Emicizumab in pediatric persons with hemophilia A.

Methods

We completed a retrospective chart review of 37 pediatric male patients aged ≤18 years on emicizumab prophylaxis for a median duration of 30.5 months at Children's Medical Center in Dallas, Texas.

Results

We identified 4 pediatric persons with severe hemophilia A with and without inhibitors who experienced a provoked or unprovoked serious bleed requiring hospitalization.

Conclusion

This study highlights that serious bleeds, both provoked and unprovoked, can occur in pediatric persons with severe hemophilia A. These findings are important for clinicians to provide appropriate counseling/education and recommendation of treatment for pediatric persons with severe hemophilia A through shared decision making. Up-titration of emicizumab or factor VIII replacement needs consideration in persons with hemophilia with suboptimal bleeding control or who participate in activities categorized as moderate- to high-risk activities.

Management and Outcomes of Invasive Procedures in Individuals with Hemophilia A on Emicizumab Prophylaxis: A Single Center Experience

Prophylactic treatment with emicizumab has become an important and effective bleeding prevention for people with hemophilia A (PwHA). Perioperative management of PwHA using emicizumab prophylaxis is still challenging due to a lack of experience. Medical records of perioperative management and outcomes were reviewed, and data were collected for adult PwHA receiving emicizumab and undergoing surgical procedures between August 2019 and July 2022 at the University Medical Center Ljubljana. Twelve surgical procedures were performed in eight PwHA (one with FVIII inhibitors) while on emicizumab prophylaxis. Three minor procedures included cataract surgery, cystoscopic lithotripsy, and percutaneous coronary intervention. Nine major surgeries included four osteosyntheses, necrectomy of chronic osteomyelitis with new ankle arthrodesis, two below-knee amputations, total knee replacement, and placement of ventriculostomy after a spontaneous intraventricular hemorrhage. No major bleeds, thrombotic events or deaths, or new inhibitors appeared. Our real-world experience demonstrates that minor and major surgeries can be performed safely in PwHA on emicizumab prophylaxis. Additional data are needed to optimize dosing/duration of additional hemostatic agents in diverse invasive procedures and complex clinical situations.

Race, ethnicity, and immune tolerance induction in hemophilia A in the United States

Background

In racially diverse communities, treatment of chronic diseases can vary across racial and ethnic groups.

Objectives

To examine healthcare disparities in hemophilia care in the United States by evaluating receipt of immune tolerance induction (ITI) among different racial and ethnic groups.

Methods

In this cross-sectional study, people with severe hemophilia A with an inhibitor who entered the Center for Disease Control and Prevention Community Counts registry between 2013 and 2017, were aged ≥5 years at study entry, and had a history of an inhibitor (n = 614) were included. The proportion of participants receiving ITI was examined according to race and ethnicity in bivariable analysis and multivariable analysis adjusting for demographic and clinical covariates. Unadjusted and adjusted prevalence ratios and corresponding 95% CIs were computed.

Results

Among 614 participants included in the study, 56.4% were non-Hispanic (NH) White, 19.7% were NH Black, 18.4% were Hispanic, and 4.9% were Asian. ITI was received by 85.2% of participants. On bivariable analysis, ITI treatment did not vary by race or ethnicity. On multivariable analysis, NH Black and Hispanic participants were significantly less likely to receive ITI compared to NH White participants (adjusted prevalence ratio, 0.91 [95% CI, 0.84-0.99] and 0.84 [95% CI, 0.75-0.93], respectively).

Conclusion

Although the role of ITI may evolve with growing use of emicizumab and the introduction of new hemophilia treatment products, understanding characteristics that influence care, particularly race and ethnicity, where physician bias and patient mistrust can occur, will remain relevant and applicable to other complex therapies, including gene therapy.

Clinical efficacy of simoctocog alfa versus extended half-life recombinant FVIII concentrates in hemophilia A patients undergoing personalized prophylaxis using a matching-adjusted indirect comparison method

OBJECTIVES

We aimed to indirectly compare the efficacy of personalized prophylaxis with simoctocog alfa (Nuwiq®) versus three extended half-life (EHL) recombinant FVIII (rFVIII) concentrates.

METHODS

Treatment effects were compared using matching-adjusted indirect comparisons after matching individual patient-level baseline characteristics for simoctocog alfa (pharmacokinetic [PK]-guided personalized prophylaxis) against published aggregate personalized prophylaxis data for efmoroctocog alfa, damoctocog alfa pegol, and rurioctocog alfa pegol.

RESULTS

A higher percentage (p < .001) of patients with zero bleeds was found with simoctocog alfa compared with efmoroctocog alfa (75% vs. 45%), damoctocog alfa pegol (77% vs. 38%), and rurioctocog alfa pegol (target trough level 1%-3%; 78% vs. 42%). Similar efficacy was found comparing simoctocog alfa against rurioctocog alfa pegol 8%-12% (77% vs. 62%). The mean total annualized bleeding rate was lower (p < .001) with simoctocog alfa than damoctocog alfa pegol (1.5 vs. 4.9). Consistent with approved dosing, the mean FVIII weekly dose was higher (p < .001) for simoctocog alfa than efmoroctocog alfa, damoctocog alfa pegol, or rurioctocog alfa pegol 1%-3%, but lower (p < .001) than rurioctocog alfa pegol 8%-12%.

CONCLUSIONS

Indirect comparisons demonstrated that PK-guided, personalized prophylaxis with simoctocog alfa can lead to higher zero bleed rates compared with personalized EHL rFVIII concentrate regimens, albeit with higher weekly doses, and a lower percentage of patients treated twice weekly or less.

The in vitro effect of anticoagulant agents on coagulation and fibrinolysis in the presence of emicizumab in the plasmas from patients with haemophilia A

INTRODUCTION

Emicizumab is used as hemostatic prophylaxis for patients with hemophilia A (PwHA), irrespective of the presence of inhibitors. Although bacterial infection can lead to a procoagulant state, there is limited information on coagulation and fibrinolysis potentials in emicizumab-treated PwHA and on the use of anticoagulants in such cases.

AIM

We examined whether anticoagulants affect the coagulation and fibrinolysis potentials in plasma from PwHA spiked with emicizumab.

METHODS

Plasma from PwHA was in vitro supplemented with emicizumab (50 μg/mL; emi-plasma) and anticoagulants (recombinant thrombomodulin (rTM), nafamostat mesylate (NM), unfractionated heparin (UFH), or low-molecular-weight heparin (LMH)). PwHA plasma spiked with rFVIII (1 IU/mL) was used as a reference (ref-plasma). The coagulation and fibrinolysis potentials in plasma was measured by thrombin and plasmin generation assay (T/P-GA) and clot-fibrinolysis waveform analysis (CFWA).

RESULTS

In T/P-GA and CFWA, coagulation potentials (maximum coagulation velocity; |min1|, and peak thrombin; Th-Peak) in plasma rose with increasing concentrations of emicizumab and rFVIII, but fibrinolytic potentials (peak plasmin; Plm-Peak, and maximum fibrinolytic velocity; |FL-min1|) remained unchanged. Adding rTM, NM, and UFH to emi-plasma suppressed coagulation and fibrinolysis potentials, similar to ref-plasma. Regarding the heparin, UFH and LMH inhibited the improved coagulation in emi-plasma. UFH inhibited fibrinolysis as well, but LMH did not.

CONCLUSIONS

Anticoagulants could exhibit the inhibitory effects on the coagulation and fibrinolysis potentials in plasma from PwHA spiked with emicizumab, similar to those in normal plasma.

Emicizumab use in females with moderate or mild hemophilia A without factor VIII inhibitors who warrant prophylaxis

Background

Hemophilia A (HA) is predominantly associated with males due to X-linked inheritance. Males and females with HA have shared unmet medical needs, highlighting the necessity for comprehensive care irrespective of sex.

Objectives

This analysis investigated the efficacy and safety of emicizumab prophylaxis in 3 females with HA.

Methods

HAVEN 6 (NCT04158648) is a phase III study of emicizumab in people with non-severe HA without factor (F)VIII inhibitors warranting prophylaxis per investigator assessment, and the study methodology has been reported previously. Female-specific endpoints included menstruation-related quality of life and menstruation heaviness.

Results

HAVEN 6 enrolled 3 females aged ≥18 years and within reproductive age (n = 2 mild HA; n = 1 moderate HA; n = 2 receiving prior FVIII prophylaxis; n = 1 receiving prior episodic FVIII). Participants presented with diverse bleeding phenotypes at baseline: 2 had no bleeds in the 24 weeks prior to enrollment, while 1 had an annualized bleed rate for all bleeds of 208.6. On-study annualized bleed rates for all bleeds were 0, 2.8, and 11.6, respectively. The 2 evaluable participants indicated improved menstruation-related quality of life vs baseline. Two participants experienced 3 grade 1/2 treatment-related adverse events; no new safety signals were identified. All 3 participants preferred emicizumab over their previous treatment and reported a better score for treatment burden and preoccupation domains of the Comprehensive Assessment Tool of Challenges in Hemophilia questionnaire.

Conclusion

Overall, results were consistent with those reported in the male population enrolled in the HAVEN 6 study, suggesting efficacy and a favorable safety profile for emicizumab in females with non-severe HA warranting prophylaxis.

Inhibitor development according to concentrate in severe hemophilia: reporting on 1392 Previously Untreated Patients from Europe and Canada

Background

Clotting factor concentrates have been the mainstay of severe hemophilia treatment over the last 50 years. Differences in risk of neutralizing antibody (inhibitor) formation according to concentrate used remain clinically relevant.

Objectives

To assess inhibitor development according to type of clotting factor concentrate in previously untreated patients (PUPs) with severe hemophilia A and B.

Methods

The European Haemophilia Safety Surveillance (EUHASS) and Canadian Bleeding Disorders Registry (CBDR) have been monitoring adverse events overall and according to concentrate for 11 and 8 years, respectively. Inhibitors were reported quarterly, and PUPs completed 50 exposure days without inhibitor development annually. Cumulative inhibitor incidences and 95% confidence intervals (CIs) were compared without adjustment for other risk factors.

Results

Fifty-six European and 23 Canadian centers reported inhibitor development in 312 of 1219 (26%; CI, 23%-28%) PUPs with severe hemophilia A and 14 of 173 (8%; CI, 5%-13%) PUPs with severe hemophilia B. Inhibitor development was lower on plasma-derived factor (F)VIII (pdFVIII, 20%; CI, 14%-26%) than on standard half-life recombinant FVIII (SHL-rFVIII, 27%; CI, 24%-30% and odds ratio, 0.67; CI, 0.45%-0.98%; P = .04). Extended half-life recombinant FVIII (EHL-rFVIII, 22%; CI, 12%-36%) showed an intermediate inhibitor rate, while inhibitor rates for Advate (26%; CI, 22%-31%) and Kogenate/Helixate (30%; CI, 24%-36%) overlapped. For other SHL-rFVIII concentrates, inhibitor rates varied from 3% to 43%. Inhibitor development was similar for pdFIX (11%; CI, 3%-25%), SHL-rFIX (8%; CI, 3%-15%), and EHL-rFIX (7%; CI, 1%-22%).

Conclusion

While confirming expected rates of inhibitors in PUPs, inhibitor development was lower in pdFVIII than in SHL-rFVIII. Preliminary data suggest variation in inhibitor development among different SHL-rFVIII and EHL-rFVIII concentrates.

Epidemiological profile of hemophilia A in Karbala-Iraq

Hemophilia is an X-linked congenital bleeding disorder caused by a deficiency of coagulation factor VIII (FVIII) (in hemophilia A) or factor IX (FIX) (in hemophilia B) and is one of the most important hereditary conditions in Iraq. The current study tried to provide a glimpse into the epidemiological and clinical status, as well as complications and treatment used for patients with hemophilia A in Karbala, Iraq. This retrospective research was carried out by reviewing the medical records of 90 male patients diagnosed with hemophilia A registered at the Hereditary Blood Disease Center in Karbala Teaching Hospital for children in Karbala, Iraq. The data was collected from May 10, 2023, until June 15, 2023, and included age, severity, type of bleeding, therapeutic approach, chronic viral infections including hepatitis B, hepatitis C, and human immunodeficiency virus (HIV). The median age of the patients was 15 years (18.86±14.42). In this study, one-third of patients' presentations started in the first year of life. The most common type was severe hemophilia A (factor VIII activity < 1%). Consequently, more than half of the patients were treated with factor VIII concentrate. Four patients had hepatitis C, while HIV was confirmed in one patient. The epidemiological or clinical parameters of hemophilia A patients in Karbala seem similar to those in other cities in Iraq. By considering this preliminary data, further comprehensive studies for patients with hemophilia and associated complications in other provinces or cities in Iraq are highly suggested to provide a clear perspective about the prevalence and epidemiological burdens.

The immunogenicity, safety, and efficacy of N8-GP in previously untreated patients with severe hemophilia A: pathfinder6 end-of-trial results

BACKGROUND

The pathfinder6 (NCT02137850) international phase 3 trial examined immunogenicity, safety, and efficacy of the extended half-life factor VIII (FVIII) replacement product N8-GP (turoctocog alfa pegol; Esperoct) in previously untreated patients (PUPs) with hemophilia A.

OBJECTIVES

We present end-of trial results for extended PUP N8-GP treatment for up to a median (range) 2.5 (0.0; 7.4) years.

PATIENTS/METHODS

Longer-term N8-GP treatment in PUPs with hemophilia A was examined. The prophylaxis regimen was ∼60 IU/kg N8-GP i.v. twice weekly, or every 3 or 7 days. The primary endpoint was the incidence of FVIII inhibitors.

RESULTS

Overall, 81 patients received N8-GP and were included in this analysis. The inhibitor incidence was 30.0% (15.7% high-titer [>5 BU]) for the extension phase. Patients had a median (range) 2.9 (0.1; 7.2) years of prophylaxis following the pre-prophylaxis period. During prophylaxis, the median annualized bleeding rate (ABR) (interquartile range) was 1.4 (0.6; 3.5), 13% of patients experienced no bleeding episodes, and 55.1% of patients experienced no spontaneous bleeds. The proportion of patients without any spontaneous bleeding episodes increased after the first year of prophylaxis. The hemostatic success rate in the treatment of bleeding episodes was 87.6%. No additional safety concerns were observed in patients with previously reported observation of temporarily decreased incremental recovery (IR).

CONCLUSION

Long-term end-of-trial PUP N8-GP prophylaxis data indicate that PUPs respond well to long-term N8-GP treatment. The inhibitor incidence was consistent with previous results. Median ABR during prophylaxis was 1.4. There were no lasting clinical impacts or safety concerns for patients with an observation of temporarily decreased IR.

Effect of emicizumab-neutralizing antibodies on activated partial thromboplastin time-based clotting time test results in patients treated with emicizumab

Background

Emicizumab is a bispecific humanized monoclonal antibody that shortens the activated partial thromboplastin time (aPTT), making aPTT-based tests unreliable.

Objectives

To evaluate the efficacy of a mixture of 2 anti-idiotype monoclonal antibodies (anti-emi) in neutralizing emicizumab in samples from persons with hemophilia A treated with emicizumab.

Methods

Fifty samples from persons with hemophilia A treated with emicizumab were analyzed for aPTT and factor VIII procoagulant activity; FVIII inhibitor titer was measured using Nijmegen-Bethesda assay in 50 plasma samples of additional patients (positive for FVIII inhibitor) treated with emicizumab. FVIII procoagulant activity and inhibitor titer were measured using 1-stage (Actin FS, Siemens) and chromogenic assays with bovine regents (Factor VIII Chromogenic Assay, Siemens). Emicizumab concentration was measured by modified a 1-stage assay calibrated with a drug-specific calibrator (r2 Diagnostics Inc). All the tests were performed on Sysmex CS-2400 (Sysmex) before and after the addition of anti-emi (Chugai Pharmaceutical).

Results

Emicizumab concentrations measured after neutralization were <1.6 μg/mL in all samples. FVIII levels were >480 IU/dL with an aPTT of <30.8 seconds in all samples before neutralization and were <1 IU/dL with an aPTT of >70 seconds after adding anti-emi. FVIII inhibitor resulted in a false negative result in 44 of 50 samples measured with the 1-stage assay before neutralization. A good correlation (r = 0.98) was found between inhibitor titer measured using the chromogenic (insensitive to emicizumab) and 1-stage assays after neutralization.

Conclusion

The anti-emi antibodies were shown to completely neutralize emicizumab, making samples pretreated with anti-emi analyzable with the 1-stage assay.

Large Intron Inversions in Romanian Patients with Hemophilia A-First Report

Background and Objectives: Despite the vast heterogeneity in the genetic defects causing hemophilia A (HA), large intron inversions represent a major cause of disease, accounting for almost half of the cases of severe HA worldwide. We investigated the intron 22 and intron 1 inversion status in a cohort of Romanian unrelated patients with severe HA. Moreover, we evaluated the role of these inversions as relative risk factors in inhibitor occurrence. Materials and Methods: Inverse shifting-a polymerase chain reaction method was used to detect the presence of intron 22 and intron 1 inversions in 156 Romanian patients with HA. Results: Intron inversion 22 was found in 41.7% of the patients, while intron 1 inversion was detected in 3.2% of the patients. Overall, large intron inversions represented the molecular defect in 44.9% of the studied patients. Our findings are in accord with previously published reports from Eastern Europe countries and with other international studies. The risk of inhibitor development was higher in patients with inversion 1 compared to the patients with HA without any inversion detected. Conclusions: The current study demonstrates the major causative role of large intron inversions in severe HA in Romanian patients. Moreover, our study confirms the contribution of intron 1 inversion in inhibitor development.

Imlifidase, a new option to optimize the management of patients with hemophilia A on emicizumab

BACKGROUND

Emicizumab is a bispecific, chimeric, humanized immunoglobulin G (IgG)4 that mimics the procoagulant activity of factor (F) VIII (FVIII). Its long half-life and subcutaneous route of administration have been life-changing in treating patients with hemophilia A (HA) with or without FVIII inhibitors. However, emicizumab only partially mimics FVIII activity; it prevents but does not treat acute bleeds. Emergency management is particularly complicated in patients with FVIII inhibitors receiving emicizumab prophylaxis in whom exogenous FVIII is inefficient. We have shown recently that Imlifidase (IdeS), a bacterial IgG-degrading enzyme, efficiently eliminates human anti-FVIII IgG in a mouse model of severe HA with inhibitors and opens a therapeutic window for the administration of exogenous FVIII.

OBJECTIVES

To investigate the impact of IdeS treatment in inhibitor-positive HA mice injected with emicizumab.

METHODS

IdeS was injected to HA mice reconstituted with human neutralizing anti-FVIII IgG and treated with emicizumab.

RESULTS

IdeS hydrolyzed emicizumab in vitro and in vivo, albeit, at slower rates than another recombinant human monoclonal IgG4. While F(ab')2 fragments were rapidly cleared from the circulation, thus leading to a rapid loss of emicizumab procoagulant activity, low amounts of single-cleaved intermediate IgG persisted for several days. Moreover, the IdeS-mediated elimination of the neutralizing anti-FVIII IgG and restoration of the hemostatic efficacy of exogenous FVIII were not impaired by the presence of emicizumab and polyclonal human IgG in inhibitor-positive HA mice.

CONCLUSION

Our results suggest that IdeS could be administered to inhibitor-positive patients with HA receiving emicizumab prophylaxis to improve and ease the management of breakthrough bleeds or programmed major surgeries.