Evaluating the benefits of emicizumab prophylaxis for haemophilia A with inhibitors: A cost-effectiveness and budget impact analysis in Thailand's upper-middle income setting.

BACKGROUND: In Thailand, an upper-middle-income country, managing haemophilia A (HA) with inhibitors poses significant challenges, often necessitating bypassing agents (BPAs) for bleeding control. This study evaluates the cost-effectiveness and budget impact of emicizumab, a novel prophylactic agent, as an alternative to both episodic and prophylactic BPA treatments from a societal perspective. METHODS: A Markov model was employed to estimate the lifetime societal costs and outcomes of emicizumab prophylaxis for HA patients with inhibitors. Treatment efficacy, cost, and epidemiological data were obtained through a comprehensive literature review and incorporated into the model. A 5-year budget impact analysis complemented the cost-utility analysis, with a 3% annual discount rate applied to future costs and outcomes. RESULTS: In the base-case scenario, emicizumab prophylaxis in HA patients aged 2 years and above demonstrated superior cost-effectiveness, yielding 18.1 quality-adjusted life years (QALYs) per patient over a lifetime and resulting in cost savings of 138 million Thai Baht (THB) compared to BPA prophylaxis. Compared to episodic BPA treatment, emicizumab yielded 30.5 QALYs and saved 25 million THB per patient. The 5-year budget impact was projected at 1775 million THB. CONCLUSIONS: Emicizumab offers a cost-saving approach for HA treatment with inhibitors in Thailand, promising significant health benefits and budgetary savings. This supports its potential inclusion in Thailand's National List of Essential Medicines to enhance haemophilia care access. HIGHLIGHTS: Managing haemophilia A (HA) with inhibitors in Thailand, an upper-middle-income country, faces challenges due to limited access to effective treatments or newer drugs for bleeding management. Emicizumab prophylaxis found to as a cost-effective and viable alternative to traditional treatments, effectively preventing bleeding in Thai HA patients over 2 years old with inhibitors. Demonstrating improved clinical outcomes and reduced costs, emicizumab prophylaxis outperforms episodic BPA treatments, positioning it as a superior treatment option for HA patients with inhibitors in Thailand.

Unravelling Acquired Hemophilia A in an Ambiguous Clinical Picture.

Acquired hemophilia A (AHA) is characterized by the development of neutralizing autoantibodies, called "inhibitors," against intrinsic factor VIII. Its presentation differs profoundly from congenital hemophilia. Here, we present the case of a 69-year-old patient presenting with right-sided flank pain and hematuria, initially diagnosed with acute pyelonephritis, who was found to have bilateral renal hemorrhage during the course of his hospitalization. Later, after a thorough diagnostic evaluation, he was deemed to have AHA.

CHIEF: A retrospective self-control study of children with severe hemophilia A without inhibitors comparing emicizumab to FVIII prophylaxis.

BACKGROUND: Hemophilia A (HA) is an X-linked bleeding disorder diagnosed by a deficiency in factor VIII (FVIII). For severe HA (SHA), prophylaxis clotting factor concentrates (CFC) has become the standard of care; however, it imparts a high treatment burden and typically results in an annualized bleeding rate (ABR) of 2-6. Emicizumab, a subcutaneously administered FVIII substitute, has become the de facto standard-of-care prophylaxis for children with SHA in many countries. Previous clinical trials of emicizumab have assessed ABR in patients greater than 12 years without inhibitors, and in children less than 12 years with inhibitors; however, there is little information published regarding the ABR of emicizumab compared to CFC in non-inhibitor SHA children. METHODS: Using a retrospective electronic medical record chart review, we conducted a self-control analysis of 15 patients less than 12 years of age during equivalent periods of CFC versus emicizumab prophylaxis. RESULTS: The mean ABR on CFC and emicizumab was 1.79 and 1.13 (p = .092), respectively, with a substantially decreased rate of joint bleeds (CFC 0.94; emicizumab 0.33; p = .001) and spontaneous bleeds (CFC 0.79; emicizumab 0.23; p = .008). No safety events were recorded for patients while administering emicizumab. The mean annual cost of CFC prophylaxis was $515,340 (SD $199,540), compared to $328,410 (SD $137,230) for emicizumab prophylaxis (p < .001). CONCLUSION: Emicizumab resulted in an improved ABR compared to CFC, especially for joint and spontaneous bleeds, had fewer administration complications, and was substantially less expensive compared to CFC prophylaxis; however, more research is necessary for a complete understanding of the effect of emicizumab on joint health and muscle bleeds.

Postpartum Acquired Hemophilia A.

Acquired hemophilia A (AHA) is a bleeding disorder that occurs from aberrant production of autoantibodies that target factor VIII. The underlying cause of AHA is unclear but can present postpartum. Very few cases have reported instances of AHA coexisting with other hematological disorders, such as sickle cell trait (SCT). Although rare and no direct correlation between the two, critical situations involving intractable bleeding can intensify the severity of these disorders. A 31-year-old pregnant female with a medical history significant for SCT presented to the hospital for a C-section. Shortly after the procedure she experienced intractable bleeding from multiple sites. Initial lab work yielded an isolated increase in activated partial thromboplastin time (aPTT). Further investigation showed abnormal mixing studies, reduced factor VIII activity and the presence of factor VIII antibodies. The patient was diagnosed with postpartum AHA (PAH) and treated with activated Factor VII and prednisone. PAH is an uncommon bleeding disorder that commonly occurs one to four months postpartum and presents as excessive bleeding elevated aPTT, abnormal mixing studies, and reduced factor VIII levels with abnormally high inhibitor levels. Despite an unknown identifiable etiology, treatment hinges upon establishing hemostasis and eradicating the aberrant generated factor VIII inhibitors. The association of AHA and other hematological disorders is not yet elucidated.

Comprehensive Evaluation of Anti-Emicizumab Antibodies in Acquired Hemophilia A: A Detailed Case Study and Methodological Evaluation.

BACKGROUND: Acquired hemophilia A (AHA) is a rare and severe bleeding disorder characterized by autoantibodies inhibiting coagulation factor VIII (FVIII). Current treatment of AHA involves bypassing agents, or FVIII replacement therapy, yet their efficacy is limited in cases of high inhibitor titers. Emicizumab, a humanized bispecific monoclonal antibody, has shown promising hemostatic effectiveness in congenital hemophilia A (HA) patients and AHA, but a minority of patients developed anti-drug antibodies (ADAs), compromising its efficacy. MATERIALS AND METHODS: We present a comprehensive characterization of anti-emicizumab antibodies in a patient with AHA experiencing diminished emicizumab efficacy from week 10 of treatment. We developed a method for analysis of anti-emicizumab antibodies, distinguishing immunoglobulin subclasses and IgG subtype profiling. ADAs' neutralizing activity was evaluated using a modified clotting assay. RESULTS: The Luminex-based assay demonstrated the presence of anti-emicizumab antibodies, confirmed through competitive analysis. We detected anti-emicizumab IgG antibodies in the patient's plasma between week 16 and 29. IgG1 and IgG2 subclasses were identified. Longitudinal analysis showed IgG isotype antibodies against both emicizumab and FVIII. Anti-emicizumab antibodies exhibited non-inhibitory activity, confirmed by a modified Bethesda assay. Moreover, no accelerated clearance of emicizumab was observed in plasma samples from the patient. CONCLUSIONS: This study presents the first documented case of anti-emicizumab antibodies in AHA. Our study provides insights into ADA development against emicizumab, emphasizing the need for monitoring tools. The developed method enables comprehensive evaluation of ADAs, aiding in personalized treatment strategies. These findings contribute to understanding emicizumab's immunogenicity profile in AHA, facilitating its optimized clinical use.

Emicizumab in Children with Severe Hemophilia A.

OBJECTIVES: To assess the effectiveness and tolerability of emicizumab prophylaxis in hemophilia A (HA). Emicizumab is a novel therapeutic drug which is the first and only non-factor replacement agent licensed for use in people with HA. METHODS: Pediatric patients aged 1 mo to 12 y with severe HA and frequent / life threatening bleeding events, with or without coagulation protein factor VIII inhibitors were enrolled (n = 18) in this observational pre-post study. Patients were switched from therapy involving on-demand or prophylactic factor VIII/bypassing agents/immune tolerance induction to emicizumab prophylaxis and followed up for 52 wk. RESULTS: One year before initiating emicizumab, a total of 229 bleeding events occurred among the enrolled children. After emicizumab prophylaxis, 5 patients had one episode of bleeding event each with a mean bleeding duration of 1.2 d in one year. The mean annualized bleeding rate significantly reduced from 12.7 ± 8.61 events pre-emicizumab prophylaxis to 0.28 ± 0.46 events post-emicizumab prophylaxis (p < 0.001). Out of the total cohort (n = 18), 72.2% of patients (n = 13) had no bleeding events (95% Confidence interval: 46.4-89.3) while on emicizumab. The mean annualized joint bleeding rate reduced from 9.72 ± 7.44 to 0.17 ± 0.38 (p < 0.001). The target joint resolution was 100% and no adverse events were noted. CONCLUSIONS: Emicizumab was found to be effective and safe as a prophylactic agent for the treatment of severe HA with and without factor VIII inhibitors. Emicizumab prophylaxis can optimize treatment outcomes and promote a better quality of life in children with severe HA.

Real-world use of recombinant porcine sequence factor VIII in the treatment of acquired hemophilia A: EU PASS.

Background: Recombinant porcine factor VIII (rpFVIII; susoctocog alfa) is indicated for the treatment of bleeding events (BEs) in adults with acquired hemophilia A (AHA). Objectives: To assess the safety, utilization, and effectiveness of rpFVIII in clinical practice. Design: EU post-authorization safety study (PASS) (NCT03199794) was a multicenter, noninterventional, post-authorization safety study conducted in adults with AHA. Methods: Data were collected retrospectively or prospectively for up to 180 days after the last rpFVIII dose. The primary objective was safety, as assessed by adverse events (AEs), serious AEs (SAEs), and AEs of special interest (AESIs) (e.g. immunogenicity, hypersensitivity reactions, thromboembolic events). Secondary endpoints included immunogenicity, rpFVIII hemostatic effectiveness, and rpFVIII utilization. Results: Fifty patients were enrolled; 31 completed the study. The median (range) follow-up for patients who completed or discontinued the study was 178 (26-371) days. The median (range) first dose of rpFVIII was 54.0 (11-200) U/kg. Thirty patients reported 46 SAEs; 5 SAEs were considered probably related to rpFVIII, of which 1 was lack of rpFVIII efficacy, and 4 were AESIs: drug resistance due to FVIII inhibition (one patient), antibody test positive for anti-pFVIII inhibitors (one patient), and de novo anti-pFVIII inhibitors (two patients). No hypersensitivity reactions or thromboembolic events were reported. Of the 50 initial BEs, 37 resolved [in a median (interquartile range) of 8.0 (4.0-16.0) days]. Conclusion: Results from this real-world study support the use of rpFVIII for AHA, aligning with findings from the clinical trial of rpFVIII (NCT01178294) in the treatment of BEs in adults with AHA. Trial registration: EUPAS16055; NCT03199794.

Pharmacokinetic evaluation of efanesoctocog alfa: breakthrough factor VIII therapy for hemophilia A.

INTRODUCTION: Blood coagulation factor (F)VIII functions as a cofactor in the tenase complex responsible for phospholipid-dependent FIXa-mediated activation of FX in plasma. Congenital defect of FVIII causes severe bleeding disorder, hemophilia (H) A. Intravenous FVIII replacement therapy is the gold standard therapy in patients with HA (PwHA) but requirement for frequent dosing of FVIII owing to pharmacokinetics burdens PwHA a lot. Efanesoctocog alfa is a new class of recombinant FVIII and has the ability to overcome conceivable unmet needs in treatment for PwHA. AREAS COVERED: Efanesoctocog alfa is a B domain-deleted single-chain fusion FVIII connected to the Fc-region of human immunoglobulin G1, D'D3-fragment of von Willebrand factor (VWF), and unstructured hydrophilic recombinant polypeptides (XTEN). Owing to its novel design, it can function independently of endogenous VWF and elicits 2 to 4 times longer half-life compared to other existing FVIII products. The prolonged half-life contributes to maintain high level of FVIII activity for most of the week and has led to excellent hemostatic effect by once-weekly administration in phase 3 clinical trials. EXPERT OPINION: Efanesoctocog alfa with outstanding pharmacological properties, well tolerated in the clinical trials, is a promising FVIII therapy for PwHA. Future studies should include long-term safety, especially in previously untreated patients.

Prevalence of Hemophilia and Clinicodemographic Characteristics of Hemophilic Patients Aged ≤ 18 Years in Thi-Qar, Iraq.

Objectives. This study aims to determine the prevalence of hemophilia in Thi-Qar, Iraq and study clinical and demographic characteristics of patients with hemophilia. Methods. In this cross-sectional study, data were obtained by reviewing all patient medical records and interviewed with the patients and their parents in 2022. The total number of patients enrolled for this study was 110 children. Results. The prevalence of hemophilia in Thi-Qar was 9.5/100 000 population (18.7/100 000 males). Factor VIII inhibitors were positive in 13.1% of patients with hemophilia A (HA). Target joints were developed among 41.4% and 27.3% of patients with HA and hemophilia B, respectively. Hepatitis C virus was positive in 3% of those with HA. Inhibitors development and arthropathy were more among those with severe disease (22% and 46.3%, respectively). Conclusion. Hemophilia prevalence in Thi-Qar was higher than the total prevalence in Iraq reported by World Federation of Hemophilia in 2022.

Lack of factor VIII detection in humans and dogs with an intron 22 inversion challenges hypothesis regarding inhibitor risk.

BACKGROUND: Almost half of severe hemophilia A (HA) cases are caused by an intron 22 inversion (Int22Inv) mutation, which truncates the 26-exon F8 messenger RNA (mRNA) after exon 22. Another F8 transcript, F8B, is initiated from within F8-intron-22. F8B mRNA consists of a short exon spliced to exons 23 to 26 and is expressed in multiple human cell types. It has been hypothesized that Int22Inv patients have self-tolerance to partial factor (F)VIII proteins expressed from these 2 transcripts. FVIII is expressed in endothelial cells, primarily in the liver and lungs. Several studies have reported FVIII expression in other cell types, although this has been controversial. OBJECTIVES: To determine if partial FVIII proteins are expressed from intron 22-inverted and/or F8B mRNA and if FVIII is expressed in nonendothelial cells. METHODS: A panel of FVIII-specific antibodies was validated and employed to label FVIII in cells and tissues and for immunoprecipitation followed by western blots and mass spectrometry proteomics analysis. RESULTS: Immunofluorescent staining localized FVIII to endothelial cells in liver sections from non-HA but not HA-Int22Inv dogs. Neither FVIII nor FVIIIB was detected in human peripheral blood mononuclear cells, B cell or T cell lines, or cell lines expanded from peripheral blood mononuclear cells, whereas FVIII antigen and activity were readily detected in primary nonhemophilic liver sinusoidal endothelial cells. CONCLUSION: If FVIII is expressed in nonendothelial cells or if partial FVIII proteins are expressed in HA-Int22Inv, the concentrations are below the detection limits of these sensitive assays. Our results argue against promotion of immune tolerance through expression of partial FVIII proteins in Int-22Inv patients.

Increased Expression Level of Human Blood Clotting Factor VIII Using NS0 Cell Line as a Host Cells.

Background: Coagulation factor VIII (FVIII) is applied for spontaneous hemorrhaging inhibition and excessive bleeding after trauma in patients with hemophilia A. High-quality human recombinant factor VIII (rFVIII) has been produced relatively in large quantities in cultured mammalian cells. NS0 is one of the most common mammalian cell lines for therapeutic protein production. Production of rFVIII has increased due to low FVIII expression levels and rising demand for hemophilia A prophylactic treatment. Several methods have been developed to prevent cell cycle progression in mammalian cells for increased recombinant protein yields. Objective: The aim of the study was to investigate the level of recombinant BDD-FVIII expression in NS0 mouse myeloma cells. Additionally, the study aimed to determine the effects of chemical drugs, Mitomycin C, Lovastatin, and Metformin on the secretion of FVIII through cell cycle arrest. Materials and Methods: We cultured NS0 cells and transfected them with the 2 µg pcDNA3-hBDDFVIII plasmid by Lipofectamine 3000. The cells were treated with 10 µg.mL-1 Mitomycin C, 20 µM Lovastatin, and 20 mM Metformin separately. After 24 and 48 hours, the samples were collected and, protein expression was analyzed using RT-PCR, Dot blot, and ELISA. Results: A higher protein expression level was observed in treated cells 24h and 48h after treatment with all three drugs. According to real-time PCR, Metformin treatment resulted in the highest expression level within 24 h (P=0.0026), followed by Mitomycin C treatment within 48 h (P=0.0030). Conclusion: The NS0 cell line can be regarded as a suitable host for FVIII production. FVIII protein expression level was increased by using Lovastatin, Metformin, and Mitomycin C drugs. Further investigations are suggested, and the potential application of these drugs to increase recombinant protein yield can be used to produce therapeutic proteins in the industry.

[Hemophilia: is a revolution in treatment options taking place?] / Hämophilie ­ Revolution der Therapiemöglichkeiten?

Prophylactic replacement therapy for hemophilia A (hereditary factor VIII deficiency) is a success story of the production of coagulation factor concentrates from donor plasma. Recombinant factor concentrates, which are also produced with modified gene constructs for coagulation factor VIII in order to improve pharmacological properties, have since proven their worth. This successful development over many years of factor concentrates for the successful treatment of hemophilia patients has now been followed by the innovation of a factor VIII mimetic in the form of a monoclonal antibody, which was developed in Japan already some years back. Emicizumab is a humanized, bispecific monoclonal antibody for therapeutic use in hemophilia A. With this therapeutic agent, the treatment of the hereditary coagulation defect is based, for the first time, on a completely new active principle. The specific antibody simulates the properties of coagulation factor VIII as a cofactor for the formation of the tenase complex with the coagulation factors IX and X. As a result under steady state conditions almost normal thrombin and thus fibrin formation can be achieved.

Clinical and Humanistic Burden of Non-inhibitor Haemophilia A in Five European Countries: Insights from the CHESS II Study.

INTRODUCTION: Haemophilia A (HA) is a congenital bleeding disorder caused by a deficiency/absence of factor VIII (FVIII) and characterised by frequent, acute and prolonged spontaneous or traumatic bleeding events, often leading to haemophilic arthropathy and progressive joint deterioration. HA severity is characterized by endogenous FVIII activity: mild (> 5-40%), moderate (1-5%), or severe (< 1%). HA poses a substantial clinical and socioeconomic burden on people with HA (PWHA), their caregivers, and society. This analysis evaluates clinical and patient-centric outcomes of a cohort of individuals with non-inhibitor HA sampled from France, Germany, Italy, Spain, and the UK in the 'Cost of Haemophilia in Europe: A Socioeconomic Survey II' (CHESS II) study. METHODS: CHESS II was a cross-sectional burden-of-illness study collecting clinical and socioeconomic data on adult (≥ 18 years) individuals with haemophilia A or B of any severity with or without inhibitors from eight European countries. Descriptive analyses were conducted examining physician-reported demographics, clinical and health resource utilisation information. PWHA-reported health-related quality of life (HRQoL) using the EQ-5D-5L and Work Productivity and Activity Impairment (WPAI) were also examined. Outcomes were stratified by HA severity and reported at country level. RESULTS: Demographics and clinical characteristics of the cohort (N = 880) were generally consistent across countries. Individuals with severe HA experienced more frequent bleeding events and joint disease despite broad use of factor replacement therapy long-term prophylaxis. A minority of those with mild or moderate HA also experienced such challenges. HRQoL and workforce participation diminished, and chronic pain increased, with increasing HA severity. CONCLUSION: This analysis provides up-to-date insights on the impact of HA across five European countries. Increasing HA severity was generally associated with worse clinical outcomes, HRQoL and workforce participation. These findings suggest a place for continued evidence-based tailored treatment and clinical management approaches in addressing the residual burden of HA.

Efficacy and safety of recombinant porcine factor VIII in Japanese patients with acquired hemophilia A.

Acquired hemophilia A (AHA) is a rare bleeding disorder caused by autoantibodies inhibiting human factor VIII (hFVIII). This phase II/III open-label study evaluated the safety and efficacy of recombinant porcine factor VIII (rpFVIII, susoctocog alfa) in adults with AHA and severe bleeding episodes in Japan (NCT04580407). The initial rpFVIII dose was 200 U/kg, with subsequent doses based on clinical measures including plasma FVIII activity. The primary efficacy endpoint was the proportion of severe bleeding episodes with a positive response to rpFVIII therapy 24 h after treatment initiation. Five patients were eligible for, and completed, rpFVIII treatment (age group: 60s-80s; median hFVIII inhibitor: 52 BU/mL; porcine FVIII [pFVIII] inhibitor: 3/5 patients). The median (range) total dose/patient was 548.4 (198-1803) U/kg with a median 3.0 infusions/patient. All patients responded positively to rpFVIII therapy at 24 h regardless of baseline pFVIII inhibitor status. rpFVIII treatment was well tolerated with no adverse events of special interest such as thromboembolic events or de novo pFVIII inhibitors. This study supports the use of rpFVIII as a novel therapy in the clinical management of patients with AHA in Japan. rpFVIII was approved for treating bleeding episodes in adults with AHA in Japan in 2024.

An Electrochemical Biosensor for the Detection of Pulmonary Embolism and Myocardial Infarction.

Due to the clinical similarities between pulmonary embolism (PE) and myocardial infarction (MI), physicians often encounter challenges in promptly distinguishing between them, potentially missing the critical window for the correct emergency response. This paper presents a biosensor, termed the PEMI biosensor, which is designed for the identification and quantitative detection of pulmonary embolism or myocardial infarction. The surface of the working electrode of the PEMI biosensor was modified with graphene oxide and silk fibroin to immobilize the mixture of antibodies. Linear sweep voltammetry was employed to measure the current-to-potential mapping of analytes, with the calculated curvature serving as a judgment index. Experimental results showed that the curvature exhibited a linear correlation with the concentration of antigen FVIII, and a linear inverse correlation with the concentration of antigen cTnI. Given that FVIII and cTnI coexist in humans, the upper and lower limits were determined from the curvatures of a set of normal concentrations of FVIII and cTnI. An analyte with a curvature exceeding the upper limit can be identified as pulmonary embolism, while a curvature falling below the lower limit indicates myocardial infarction. Additionally, the further the curvature deviates from the upper or lower limits, the more severe the condition. The PEMI biosensor can serve as an effective detection platform for physicians.

Reduce energy consumption in your laboratory - switch ultra-low temperature freezers from - 80 °C to -70 °C. A pilot study on short term storage of plasma samples for coagulation testing.

It is common practice in laboratories to store biological samples in ultra-low temperature (ULT) freezers. There is growing interest in raising the temperature of ULT freezers in order to save energy and reduce expenses, as energy conservation becomes increasingly important and sustainable laboratory practices gain popularity. In our laboratory, plasma samples are stored for three months for diagnostic purposes. We therefore took the opportunity to investigate the effect of two different storage temperatures (-70 °C vs -80 °C), on activated partial thromboplastin time (APTT), factor VIII (FVIII), international normalized ratio (INR) and factor VII (FVII) measurements on paired plasma samples collected from 26 individuals after three months of storage. Automated coagulation analysers CS-5100 and ACL TOP were used to perform the tests. We found no consistent difference between the two storage temperatures for any of the four coagulation parameters (all p-values > 0.05). We conclude that the temperature of ULT freezers used to store plasma samples for APTT, FVIII, INR, and FVII measurements can be safely increased from -80 to -70 °C without affecting the stability of the samples.

Activated protein C resistance in the copresence of emicizumab and activated prothrombin complex concentrates.

Background: Venous thromboembolic events have been reported in persons with hemophilia A who received emicizumab and activated prothrombin complex concentrate (APCC) concomitantly, but the relevant mechanism(s) remains unclear. We speculated that activated protein C (APC) and antithrombin (AT) resistance might be associated with these adverse events. Objectives: To investigate APC and AT resistance in factor (F)VIII-deficient (FVIIIdef) plasma in the presence of emicizumab and APCC. Methods: In pooled normal plasma or FVIIIdef plasma samples mixed with emicizumab (50 µg/mL) and FVIII-bypassing agents, including recombinant FVIIa (2.2 µg/mL), APCC (1.3 IU/mL), or plasma-derived FVIIa/FX (1.5 µg/mL), the suppression effect of AT (0-2.4 µM) and APC (0-16 nM) was assessed by tissue factor-triggered thrombin generation assay. The APC effects in FVIIIdef plasma with the copresence of emicizumab, FII (1.3 µM), and/or FIXa (280 pM) were also examined. Results: The AT resistance in emicizumab and each bypassing agent was not observed. Moreover, APC dose-dependent suppression effect was observed in pooled normal plasma or FVIIIdef plasma mixed with emicizumab and recombinant FVIIa or plasma-derived FVIIa/FX. However, APC-catalyzed inactivation had little effect on thrombin generation assay potential in FVIIIdef plasma spiked with emicizumab and APCC. The addition of FIXa to emicizumab in FVIIIdef plasma could lead to partial APC resistance. Furthermore, FVIIIdef plasma spiked with emicizumab, FIXa, and FII was markedly resistant to APC-mediated inactivation. Conclusion: FII and FIXa in APCCs were key clotting factors for APC resistance in FVIIIdef plasma supplemented with emicizumab and APCCs. The APC resistance in persons with hemophilia A receiving emicizumab and APCC may contribute to venous thromboembolic events.

Peripheral Blood Lymphocyte Subsets in Factor VIII Inhibitor-Positive Patients with Severe Hemophilia A: A Case-Control Study.

INTRODUCTION AND OBJECTIVES: The present study aimed to investigate different peripheral lymphocyte subsets in patients with severe hemophilia A (HA) and factor VIII (FVIII) inhibitor production. For this, age-matched cases of 19 FVIII inhibitor-positive (IP), 21 FVIII inhibitor-negative (IN) and 45 healthy controls were selected for study. METHODS: Flow cytometry was used to analyze the peripheral lymphocyte subsets, including T, B, natural killer (NK) and NKT cells. The T cell subsets included CD3 + CD4-CD8- [double negative T (DNT)], CD3 + CD4 + CD8+ [double-positive T (DPT)], CD3 + CD4 + CD8- and CD3 + CD4-CD8+ T cells. Pairwise comparisons of absolute lymphocyte subset values were conducted among the three groups. The cut-off value for absolute lymphocyte counts was determined using receiver operating characteristic curve analysis. RESULTS: The results demonstrated that the absolute values of DPT cells in the IN and IP groups were significantly lower than those in the healthy control group (P = 0.007). The DNT values were also lower in severe HA patients with or without inhibitor than those in healthy subjects, but these differences were not statistically significant (P = 0.053). In addition, the absolute value of CD4+ Th cells in the IP group was lower than that in the healthy controls (P = 0.013). Although not statistically significant (P = 0.064), the absolute values of NKT cells were higher in the IN group compared with the IP group, and higher in the IP group compared with the healthy control group. There were no statistically significant differences in total T, B, CD8 + and NK cells among the IN, IP and healthy control groups. The cut-off value for absolute CD4+ Th cells in the IN group was < 598/µl. CONCLUSION: The decrease in absolute values of CD4+ Th cells in severe HA patients may contribute to the establishment of infused FVIII immune tolerance. If the CD4+ Th value remains > 598/µl, clinicians should be vigilant for possible FVIII inhibitor production, especially on days prior to FVIII exposure.

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

INTRODUCTION: Hemophilia A is an inherited bleeding disorder caused by pathogenic variants in the factor VIII gene (F8), which leads to factor VIII (FVIII) deficiency. Immune tolerance induction (ITI) is a therapeutic approach to eradicate alloantibodies (inhibitors) against exogenous FVIII in people with inherited hemophilia A. Few studies have evaluated the role of F8 variants on ITI outcome. MATERIAL AND METHODS: We included people with severe hemophilia A (FVIII ˂ 1 international units/dL) and high-responding inhibitors (≥ 5 Bethesda units/mL lifelong) who underwent a first course of ITI. Socio-demographic, clinical and laboratory data were collected. ITI outcomes were defined as total, partial successes, and failure. Detection of intron 1 and 22 inversions was performed by polymerase-chain reaction, followed by F8 sequencing. RESULTS: We included 168 people with inherited hemophilia A and high-responding inhibitors, median age 6 years at ITI start. Intron 22 inversion was the most prevalent variant (53.6 %), followed by nonsense (16.1 %), small insertion/deletion (11.3 %), and large deletion (10.7 %). In comparison with intron 22 inversion, the odds of ITI failure were 15.5 times higher (odds ratio [OR] 15.50; 95 % confidence interval [95 % CI] 4.59-71.30) and 4.25 times higher (95 % CI, 1.53-12.3) among carriers of F8 large deletions and small insertions and deletions, respectively. CONCLUSION: F8 large deletions and small insertions/deletions predicted ITI failure after a first course of ITI in patients with severe hemophilia A and high-responding inhibitors. This is the first study to show F8 large deletions and small insertions/deletions as predictors of ITI failure.