DNA base editing corrects common Hemophilia A mutations and restores factor VIII expression in vitro and ex-vivo models.

BACKGROUND: Replacement and non-replacement therapies effectively control bleedings in Hemophilia A (HA) but imply lifelong interventions. The authorized gene addition therapy could provide a cure but still poses questions on durability. F8 gene correction would definitively restore factor VIII (FVIII) production, as shown in animal models through nucleases mediating homologous recombination (HR). However, low efficiency and potential off-target double-strand break (DSB) still limit HR translatability. OBJECTIVES: To correct common model single point mutations leading to severe HA through the recently developed DSB/HR-independent base (BE) and prime (PE) editing approaches. METHODS: Screening for efficacy of BE/PE systems in HEK293T transiently expressing FVIII variants and validation at DNA (sequencing) and protein (ELISA; aPTT) level in stable clones. Evaluation of rescue in engineered blood outgrowth endothelial cells (BOEC) by lentiviral-mediated delivery of BE. RESULTS AND CONCLUSIONS: Transient assays identified the best-performing BE/PE systems for each variant, with the highest rescue of FVIII expression (up to 25% of rFVIIIwt) for the p.R2166* and p.R2228Q mutations. In stable clones we demonstrated that the mutation reversion on DNA (∼24%) was consistent with the rescue of FVIII secretion and activity 20-30%). The lentiviral-mediated delivery of the selected BE systems was attempted in engineered BOEC harboring the p.R2166* and p.R2228Q variants, which led to an appreciable and dose-dependent rescue of secreted functional FVIII. Overall data provide the first proof-of-concept for effective BE/PE-mediated correction of HA-causing mutations, which encourage studies in mouse models to develop a personalized cure for large cohorts of patients though a single intervention.

Expert Opinions on the Management of Hemophilia A in India: The Role of Emicizumab.

Hemophilia A (HA) is a genetic disorder of hemostasis associated with a deficiency or reduced activity of clotting factor VIII (FVIII). This disorder remains unacceptably underdiagnosed in India. Early diagnosis and appropriate management of HA can substantially prevent morbidity and mortality. Currently, HA is managed with regular replacement therapy using standard or extended half-life FVIII concentrates or non-factor drug products. The challenges associated with FVIII concentrates include plateauing of drug effect, issues with its administration and adherence to treatment, breakthrough bleeds, and the development of inhibiting antibodies against administered clotting factors. Emicizumab is a bispecific antibody, launched in India in April 2019, for managing patients with HA. To investigate the role of emicizumab in Indian patients with HA, opinions were sought from 13 eminent hematologists and experts from India on the effectiveness of emicizumab in preventing all bleeds, spontaneous bleeds, perioperative bleeds, and intracranial hemorrhage; resolving target joints; and reducing the rate of hospitalizations and fatality associated with HA in children and adults, with or without inhibitors. The benefits of emicizumab over traditional FVIII concentrates include the subcutaneous route of delivery, less frequent dosing, and a lack of inhibitor development, in addition to providing sustained hemostasis without in-depth monitoring. It is a safe and effective management option for all HA patients, especially for patients with certain archetypes, such as those with inhibitors, those with high annualized bleed rates, those living far away from hemophilia care centers, pediatric patients and infants with intravenous access challenges, and those with a history of life-threatening bleeding events.

Emicizumab as a Promising Form of Therapy for Type A Hemophilia - A Review of Current Knowledge from Clinical Trials.

Hemophilia is a plasma bleeding disorder characterized by a deficiency of certain blood clotting factors. The most common forms of this disease, i.e., type A and type B, affect approximately 400,000 people worldwide. Without appropriate treatment ensuring the proper coagulation cascade, this disease may lead to serious disability. Minimizing patient discomfort is possible via replacement therapy, consisting of the substitution of a missing coagulation factor via intravenous administration. Frequent medication and the risk related to factor inhibitors are significant disadvantages, necessitating the improvement of current therapies or the development of novel ones. This review examines the humanized bispecific antibody Emicizumab which ensures hemostasis by mimicking the action of the coagulation factor VIII, a deficiency of which causes type A hemophilia. The paper outlines the topic and then summarizes available clinical trials on Emicizumab in type A hemophilia. Several interventional clinical trials have found Emicizumab to be effective in decreasing bleeding episodes and raising patient satisfaction among various hemophilia A populations. Current Emicizumab-related trials are forecast to be completed between 2024 and 2030, and in addition to congenital hemophilia A, the trials cover acquired hemophilia A and patients playing sports. Providing a more comprehensive understanding of Emicizumab may revolutionize the management of hemophilia type A and improve quality of life. Conclusively, Emicizumab is a gentler therapy owing to subcutaneous delivery and fewer injections, which reduces injection-site reactions and makes therapy less burdensome, ultimately decreasing hospital visits and indirect costs.

Emicizumab is efficacious in people with hemophilia A with comorbidities aged ≥50 years: analysis of 4 phase III trials.

Background: The treatment of older people with hemophilia A (HA) can be complicated by comorbidities. Objectives: This post hoc analysis evaluates the efficacy and safety of emicizumab in people with HA aged ≥50 years with cardiovascular (CV) risk factors or HIV and/or hepatitis C virus (HCV) infection. Methods: The HAVEN 1 (NCT02622321), HAVEN 3 (NCT02847637), HAVEN 4 (NCT03020160), and STASEY (NCT03191799) studies enrolled adults/adolescents with severe HA. Participants were categorized as having a comorbidity if they had any CV risk factors (including history of CV disease, hypertension, diabetes, hyperlipidemia, prior stroke, or obesity), HIV, and/or HCV infection. Efficacy and safety outcomes were compared by age (<50 vs ≥50 years). Results: Of 504 participants at data cutoff, 408 were aged <50 years and 96 were aged ≥50 years. In people with HA aged <50 years, 26.7% had ≥1 CV risk factor and 29.4% had HIV and/or HCV infection. In people with HA aged ≥50 years, 72.9% had ≥1 CV risk factor and 74.0% had HIV and/or HCV infection. The mean (95% CI) annualized bleed rate for treated bleeds was 1.29 (0.07-6.06) for people with HA aged <50 years and 1.82 (0.19-6.93) for people with HA aged ≥50 years. No significant differences in annualized bleed rates were observed for those with comorbidities compared with those without. Safety outcomes were similar regardless of age. Conclusion: This pooled analysis suggests that emicizumab efficacy and safety in people with HA aged ≥50 years with CV and HIV/HCV comorbidities were consistent with those in people with HA aged <50 years enrolled in the HAVEN 1, 3, and 4 and STASEY studies.

Predictive performance of pharmacokinetic-guided prophylactic dosing of factor concentrates in hemophilia A and B.

Background: Pharmacokinetic (PK)-guided dosing is used to individualize factor (F)VIII and FIX replacement therapy. Objectives: This study investigates the reliability and feasibility of PK-guided prophylactic dosing of factor concentrates in hemophilia A and B. Methods: In this multicenter, prospective cohort study, people of all ages with hemophilia received prophylactic treatment with factor concentrates based on individual PK parameters. During follow-up, at least 4 measured FVIII/FIX levels per patient were compared with corresponding predicted levels obtained by Bayesian forecasting. Predictive performance was defined as adequate when ≥80% of measured FVIII/FIX levels were within ±25% of prediction (relative error). Additionally, mean absolute error and mean error were calculated. In post hoc analyses, predictive performance was assessed allowing maximum absolute errors of 1 (trough), 5 (mid), and 15 (peak) IU/dL. Five-point scale questionnaires addressed feasibility of PK guidance. Results: We included 50 patients (median age, 19 years; range: 2-72 years). Median follow-up was 36 weeks. Seventy-one percent of levels (58% trough, 83% mid, and 80% peak) were within ±25% of prediction. Mean absolute errors were 0.8 (trough), 2.0 (mid), and 8.6 (peak) IU/dL. In post hoc analyses, 81% (trough), 96% (mid), and 82% (peak) of levels were within set limits. Patients reported low burden and high satisfaction. Conclusion: PK-guided dosing was reliable according to post hoc analyses, based on low absolute errors that were regarded as clinically irrelevant in most cases. The predefined predictive performance was achieved in mid and peak factor levels but not in trough factor levels due to measurement inaccuracy. PK guidance also seemed feasible.

Assessment of the phenotypic severity of hemophilia A: using rotational thromboelastometry (ROTEM) and APTT-clot waveform analysis.

BACKGROUND: Hemophilia A (HA) is an X-linked inherited bleeding disorder caused by reduced factor VIII (FVIII) levels. Approximately 10-15% of patients with severe HA (SHA) do not present with the anticipated bleeding pattern. Here, we assessed the phenotypic severity of hemophilia A using rotational thromboelastometry (ROTEM) and activated partial thromboplastin time-clot waveform analysis (APTT-CWA). METHODS: Patients diagnosed with hemophilia A were enrolled. Clinical phenotype assignment was performed according to the published literature, and patients were classified into four phenotypic subgroups. The whole blood sample was first run on ROTEM in INTEM mode using platelet-poor plasma, APTT was run, and the APTT-CWA graph was simultaneously recorded. RESULTS: A total of 66 patients were recruited for this study. Statistically significant differences were observed between the four phenotypically categorized groups using ROTEM and APTT-CWA. On comparing patients with mild/moderate-to-severe phenotypes (Group II) with SHA without inhibitors (Group IV), no significant difference was found for all parameters of ROTEM or APTT-CWA. The MCF, MA30, MAXV, and Alpha angle values using ROTEM were found to be the lowest in patients with SHA with inhibitors, which helped differentiate them from those with SHA without inhibitors. However, these two groups could not be differentiated using the APTT-CWA parameters. CONCLUSION: ROTEM can be used to distinguish patients with SHA with inhibitors from those with SHA without inhibitors using a combination of parameters with high sensitivity and specificity. However, APTT-CWA cannot be used to differentiate these patient groups.

Management of traumatic dental injuries in a hemophiliac patient: A challenge! Case report with nine years follow-up.

Traumatic dental injuries (TDIs) are frequently associated with an injury pattern that requires accurate diagnosis for developing the appropriate treatment plan. When children with special healthcare needs, i.e., Hemophilia experience TDIs, managing the situation becomes a challenging task for pediatric dentists due to the requirement of a multidisciplinary approach in their care. This case report highlights the successful management of extrusive luxation injury of a young permanent tooth with an open apex in an eight-year-old male child with severe Hemophilia A. After a follow-up of nine years, the pulp showed significant healing with physiological closure of the apical foramen. The study further emphasizes that timely management of such injuries can lead to improved tooth prognosis.

Simoctocog alfa (Nuwiq®) in children: early steps in life's journey for people with severe hemophilia A.

People with severe hemophilia A usually experience their first bleed early in life. In children with severe hemophilia A, primary prophylaxis is recommended to prevent recurrent and potentially life-threatening bleeds that significantly impact day-to-day life. Factor VIII (FVIII) prophylaxis is well-established in children and has been shown to reduce the development of hemophilic arthropathy. However, a major challenge of FVIII therapy is the development of neutralizing anti-FVIII antibodies (FVIII inhibitors). Simoctocog alfa (Nuwiq®) is a human cell line-derived recombinant FVIII (rFVIII) whose immunogenicity, efficacy, and safety have been studied in 167 children with severe hemophilia A across two prospective clinical trials and their long-term extensions. In 105 previously untreated children, the inhibitor rate of 16.2% for high-titer inhibitors (26.7% for all inhibitors) was lower than published rates for hamster cell line-derived rFVIII products. There was no inhibitor development in previously untreated children with non-null F8 mutations and in previously treated children. In a case series of 10 inhibitor patients, 8 (80%) underwent successful immune tolerance induction with simoctocog alfa with a median time to undetectable inhibitor of 3.5 months. In an analysis of 96 children who enrolled in the extension studies and received long-term simoctocog alfa prophylaxis for up to 5 years, median spontaneous, joint, and total annualized bleeding rates were 0.3, 0.4, and 1.8, respectively. No thromboembolisms were reported in any of the 167 children, and there were no treatment-related deaths. Optimal care of children should consider several factors, including minimization of inhibitor development risk, maintaining tolerance to FVIII, highly effective bleed prevention and treatment, safety, and impact on long-term outcomes such as bone and joint health. In this context we review the pediatric clinical data and ongoing studies with simoctocog alfa.

Application of machine learning approaches for predicting hemophilia A severity.

BACKGROUND: Hemophilia A (HA) is an X-linked congenital bleeding disorder, which leads to deficiency of clotting factor (F) VIII. It mostly affects males, and females are considered carriers. However, it is now recognized that variants of F8 in females can result in HA. Nonetheless, most females go undiagnosed and untreated for HA, and their bleeding complications are attributed to other causes. Predicting the severity of HA for female patients can provide valuable insights for treating the conditions associated with the disease, such as heavy bleeding. OBJECTIVES: To predict the severity of HA based on F8 genotype using a machine learning (ML) approach. METHODS: Using multiple datasets of variants in the F8 and disease severity from various repositories, we derived the sequence for the FVIII protein. Using the derived sequences, we used ML models to predict the severity of HA in female patients. RESULTS: Utilizing different classification models, we highlight the validity of the datasets and our approach with predictive F1 scores of 0.88, 0.99, 0.93, 0.99, and 0.90 for all the validation sets. CONCLUSION: Although with some limitations, ML-based approaches demonstrated the successful prediction of disease severity in female HA patients based on variants in the F8. This study confirms previous research findings that ML can help predict the severity of hemophilia. These results can be valuable for future studies in achieving better treatment and clinical outcomes for female patients with HA, which is an urgent unmet need.

Inhibitor eradication and treatment for acquired hemophilia A.

INTRODUCTION: Acquired hemophilia A (AHA) is a rare hemorrhagic autoimmune disorder characterized by autoantibodies against coagulation factor VIII (FVIII). In approximately half of the cases AHA does not recognize any cause (idiopathic form), while in the other cases it may be triggered by autoimmune disorders, cancers, drugs, infections, or pregnancy. Besides treating the underlying disorder, specific AHA treatment includes management of bleeding, if necessary, and inhibitor eradication. AREAS COVERED: This narrative review summarizes the main epidemiological, clinical, laboratory, and therapeutic characteristics of AHA. In particular, it is focused on the current therapeutic options for the inhibitor eradication, also showing the latest findings on the innovative therapies. A literature search strategy was performed, without temporal limits, through Medline and PubMed electronic databases. EXPERT OPINION: Various first-line and second-line immunosuppressive agents are currently available for the management of AHA. Among the latter, the anti-CD20 monoclonal antibody rituximab has been the object of intense research during the last years from investigators as innovative promising eradicating therapy for AHA. Preliminary data from the studies support the use of this drug as a first-line option for newly diagnosed AHA cases.

Variceal hemorrhage in a patient with cirrhosis and congenital hemophilia A: A therapeutic challenge.

We describe the case of a 61-year-old male patient with a history of hemophilia A and previous hepatitis C virus infection with sustained virological response and no previous documentation of cirrhosis, who was admitted for variceal bleeding. He was taken for endoscopic evaluation with evidence of active variceal hemorrhage requiring rubber band ligation. Patients with congenital coagulation disorders, such as hemophilia A, are excluded from international guidelines for gastrointestinal bleeding, making their management and counseling challenging. In this article, we describe the specific interventions to be performed in patients with hemophilia A and upper gastrointestinal tract bleeding, specifically variceal bleeding, focusing on pre-endoscopic and endoscopic management.

Laser Ablation of Pilonidal Sinus in a Patient With Hemophilia Type A: A Case Report and Review of the Literature.

Pilonidal sinus (PNS) is a common occurrence in young men. It is often caused by blockage of the sebaceous glands in the hair follicles in the sacrococcygeal area. Hemophilia type A is a hemorrhagic disorder caused by a deficiency of factor VIII. It presents with excessive bleeding, either spontaneously or secondary to trauma. The mainstay of treatment for PNS is often excision of the sinus; however, recently, laser ablation has started to be commonly used. In this article, we present a case of a young man with hemophilia A presenting with recurrent PNS successfully managed with laser ablation with no complications.

Economic and Humanistic Burden of Moderate and Severe Hemophilia A and B in Spain: Real-World Evidence Insights from the CHESS II Study.

Background: Hemophilia is a congenital disorder characterized by deficiency or absence of clotting factor VIII in hemophilia A (HA) or clotting factor IX in hemophilia B (HB), resulting in frequent, repeated, and prolonged spontaneous or traumatic bleeding into joints or soft tissue. Severity is classified by the patient's baseline level of clotting factor activity as mild (>5%-40%), moderate (1%-5%), or severe (<1%). In Spain, there is limited information on the societal economic burden of disease. Objective: To estimate the economic and humanistic burden of disease in adult patients with non-inhibitor moderate and severe HA and HB in Spain. Methods: Spanish data from the CHESS II study (2018-2020) on patients' clinical characteristics, health-related quality of life (HRQoL) and hemophilia-related healthcare resource utilization were analyzed. Economic burden was determined by estimating condition-related annual per-patient direct (medical and nonmedical) and indirect costs, stratified according to hemophilia type and severity and presented as 2022 Euros. HRQoL was assessed via the EQ-5D-5L. Results: Of 341 patients in the Spanish CHESS II cohort, 288 patients met the inclusion criteria: 181 had HA (37% [n = 66] moderate and 63% [n=115] severe) and 107 had HB (26% [n = 28] moderate and 74% [n = 79] severe). Mean annual direct cost was higher in HB than in HA, and higher in severe than in moderate patients, resulting in an annual cost/patient of €17 251 (moderate HA), €17 796 (moderate HB), €116 767 (severe HA) and €206 996 (severe HB). The main direct cost component in all groups except moderate HA was factor replacement therapy. Mean per-patient indirect cost was €4089 (moderate HA), €797 (moderate HB), €8633 (severe HA) and €8049 (severe HB). Finally, the mean total cost (direct and indirect) for moderate and severe patients were €91 017 (HA) and €163 924 (HB). EQ-5D-5L [SD] scores were lower in patients with severe HA (0.77 [0.18]) and severe HB (0.70 [0.22]) compared with patients with moderate HA (0.81 [0.15]) and moderate HB (0.86 [0.17]). Conclusions: Independently of the type of hemophilia, greater condition severity was associated with increased costs and a decrease in HRQoL.

Clinical and molecular characteristics of hemophilia A affected individuals and carriers: A 24 years experience from three centers.

Hemophilia A is a rare bleeding disorder with variable expressivity and allelic heterogeneity. Despite the advancement of prenatal diagnostics and molecular studies, the number of studies reviewing the reproductive choices of hemophilia A carriers and affected individuals remains limited. Through this retrospective review, we hope to gain a deeper understanding of hemophilia A-affected individuals' clinical and molecular characteristics, as well as the reproductive choices of the at-risk couples. A total of 122 individuals harboring likely causative F8 gene alterations from 64 apparently unrelated families attending three centers between 3/2000 and 3/2023 were included in this study. Their clinical and molecular findings as well as reproductive choices were gathered in a clinical setting and verified through the electronic medical record database of the public health system. Forty-seven affected males and 75 female heterozygous carriers were included in the analysis. Among 64 apparently unrelated families, 36 distinct pathogenic/likely pathogenic variants were identified, of which 30.6% (11/36) of variants were novel. While the majority of clinical findings and genotype-phenotype correlations appear to be in accordance with existing literature, female carriers who had no fertility intention were significantly more likely to have affected sons than those who had fertility intention (5/19 vs. 4/5; p = 0.047). Through this retrospective review, we summarized the clinical and molecular characteristics of 122 individuals harboring pathogenic/likely pathogenic F8 variants, as well as their fertility intentions and reproductive outcomes. Further studies are required to look into the considerations involved in reproductive decision-making.

GP64-pseudotyped lentiviral vectors target liver endothelial cells and correct hemophilia A mice.

Lentiviral vectors (LV) are efficient vehicles for in vivo gene delivery to the liver. LV integration into the chromatin of target cells ensures their transmission upon proliferation, thus allowing potentially life-long gene therapy following a single administration, even to young individuals. The glycoprotein of the vesicular stomatitis virus (VSV.G) is widely used to pseudotype LV, as it confers broad tropism and high stability. The baculovirus-derived GP64 envelope protein has been proposed as an alternative for in vivo liver-directed gene therapy. Here, we perform a detailed comparison of VSV.G- and GP64-pseudotyped LV in vitro and in vivo. We report that VSV.G-LV transduced hepatocytes better than GP64-LV, however the latter showed improved transduction of liver sinusoidal endothelial cells (LSEC). Combining GP64-pseudotyping with the high surface content of the phagocytosis inhibitor CD47 further enhanced LSEC transduction. Coagulation factor VIII (FVIII), the gene mutated in hemophilia A, is naturally expressed by LSEC, thus we exploited GP64-LV to deliver a FVIII transgene under the control of the endogenous FVIII promoter and achieved therapeutic amounts of FVIII and correction of hemophilia A mice.

Clinical and economic burden of immune tolerance induction in entire patients with hemophilia A: Insights from a real-world Korean setting.

INTRODUCTION: The most notable challenge facing hemophilia A treatment is the development of inhibitors against factor VIII, resulting in increased clinical and socioeconomic burdens due to the need for expensive bypassing agents (BPAs). Although immune tolerance induction (ITI) is currently the primary approach for inhibiting and reducing the inhibitors, the lengthy duration of ITI necessitates the continued use of BPA to manage bleeding episodes. In this study, we aimed to obtain real-world evidence on the clinical and economic aspects and associated burdens experienced by patients with hemophilia A with inhibitors undergoing ITI in Korea. METHODS: Claims data from January 1, 2007, to December 31, 2020, were used in this study. The study cohort comprised patients with hemophilia A undergoing ITI, who were categorized into three groups: successful, failed, or continuation of ITI. We evaluated clinical and economic burdens, including monthly healthcare visits, medication costs, and total medical expenses. RESULTS: The study involved 33 cases of ITI across 32 patients. Excluding seven continuation cases where success could not be determined at the observation point, the estimated success rate of ITI was 80.8 %. The median duration of ITI for all patients was 25.7 months. While no significant disparities were noted in the ITI duration between successful and unsuccessful cases (24.51 vs. 25.66 months), substantial discrepancies were observed in the duration of BPA usage (11.10 vs. 25.66 months) and the number of prescribed BPAs (1.79 vs. 2.97). CONCLUSION: Successful ITI reduced both clinical and economic burdens, resulting in decreased monthly medication expenses and overall medical costs.

In-depth structure-function profiling of the complex formation between clotting factor VIII and heme.

BACKGROUND AND AIMS: Blood disorders, such as sickle cell disease, and other clinical conditions are often accompanied by intravascular hemolytic events along with the development of severe coagulopathies. Hemolysis, in turn, leads to the accumulation of Fe(II/III)-protoporphyrin IX (heme) in the intravascular compartment, which can trigger a variety of proinflammatory and prothrombotic reactions. As such, heme binding to the blood coagulation proteins factor VIII (FVIII), fibrinogen, and activated protein C with functional consequences has been demonstrated earlier. METHODS: We herein present an in-depth characterization of the FVIII-heme interaction at the molecular level and its (patho-)physiological relevance through the application of biochemical, biophysical, structural biology, bioinformatic, and diagnostic tools. RESULTS: FVIII has a great heme-binding capacity with seven heme molecules associating with the protein. The respective binding sites were identified by investigating heme binding to FVIII-derived peptides in combination with molecular docking and dynamic simulation studies of the complex as well as cryo-electron microscopy, revealing three high-affinity and four moderate heme-binding motifs (HBMs). Furthermore, the relevance of the FVIII-heme complex formation was characterized in physiologically relevant assay systems, revealing a ~ 50 % inhibition of the FVIII cofactor activity even in the protein-rich environment of blood plasma. CONCLUSION: Our study provides not only novel molecular insights into the FVIII-heme interaction and its physiological relevance, but also strongly suggests the reduction of the intrinsic pathway and the accentuation of the final clotting step (by, for example, fibrinogen crosslinking) in hemolytic conditions as well as a future perspective in the context of FVIII substitution therapy of hemorrhagic events in hemophilia A patients.

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

BACKGROUND: Valoctocogene roxaparvovec transfers a human factor (F)VIII coding sequence into hepatocytes of people with severe hemophilia A to provide bleeding protection. OBJECTIVES: To 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, annualized FVIII utilization, 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. Safety was assessed by adverse events (AEs). RESULTS: At week 156, 131 of 134 participants remained in the study; overall, 17 of 134 resumed prophylaxis. Mean annualized bleeding rate for treated bleeds decreased from 4.8 (SD, 6.5) bleeds/y at baseline to 0.8 (SD, 2.3; P < .0001) bleeds/y after prophylaxis (prophylaxis cessation to last follow-up) and 0.97 (SD, 3.48) bleeds/y during year 3. Annualized FVIII utilization decreased 96.8% from baseline after 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 and 3 than between years 1 and 2. At the end of year 3, clinically meaningful improvements in the Haemophilia-Specific Quality of Life Questionnaire for Adults Total Score were observed (mean change from baseline, 6.6; 95% CI, 4.24-8.87; P < .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. CONCLUSION: Hemostatic efficacy was maintained, and safety remained unchanged from previous years.

Comparative Effectiveness of Valoctocogene Roxaparvovec and Prophylactic Factor VIII Replacement in Severe Hemophilia A.

INTRODUCTION: A prospective, non-interventional study (270-902) followed 294 adults with severe hemophilia A (SHA) receiving prophylactic factor VIII (FVIII). From these participants, 112 rolled over into a single-arm, multicenter, phase 3 trial (GENEr8-1; NCT03370913) that evaluated efficacy and safety of valoctocogene roxaparvovec, a gene therapy that provides endogenous FVIII in individuals with SHA. Participants from 270-902 who did not roll over provide an opportunity for a contemporaneous external control. Therefore, the comparative effectiveness of valoctocogene roxaparvovec vs FVIII prophylaxis was evaluated using propensity scoring (PS). METHODS: This post hoc analysis compared 112 participants from GENEr8-1 (treated cohort) to 73 participants in 270-902 who did not enroll in GENEr8-1 (control cohort). The primary analysis used standardized mortality ratio weighting to re-weight baseline characteristics of the control cohort to better match the treated cohort. Mean annualized bleeding rates (ABR) for treated and all bleeds were compared between cohorts along with the proportion of participants with zero bleeds (treated and all bleeds). Sensitivity and scenario analyses were also conducted. RESULTS: PS adjustments reduced differences in baseline characteristics between cohorts. Mean treated (4.40 vs 0.85; P < 0.001) and all (5.01 vs 1.54; P < 0.001) ABR were significantly lower, and the proportions of participants with zero treated bleeds (82.1% vs 32.9%; P < 0.001) and all bleeds (58.0% vs 28.5%; P < 0.001) were significantly higher in GENEr8-1. CONCLUSIONS: PS-adjusted analyses were consistent with prior intra-individual comparisons. Compared with participants receiving prophylactic FVIII, the participants receiving valoctocogene roxaparvovec experienced lower ABR, and a higher proportion had zero bleeds. TRAIL REGISTRATION: ClinicalTrials.gov identifier, NCT03370913.

Hemophilia A is a bleeding disorder where blood is unable to clot properly because of a missing protein called factor VIII (FVIII). Individuals with hemophilia A have an increased risk of prolonged bleeding episodes that can be deadly. To prevent bleeding, people with severe hemophilia A need to routinely inject treatment into the skin or vein (prophylaxis). While effective, some people find the time and effort needed to maintain frequent injections difficult, since some forms of the prophylaxis must be administered in a hospital setting. Valoctocogene roxaparvovec is a gene therapy where a single injection provides instructions to the liver of individuals with hemophilia A to make the missing protein (FVIII). Then, their own liver cells can produce FVIII protein and prevent bleeding episodes. The valoctocogene roxaparvovec clinical trial compared the number of treated bleeding episodes participants had prior to gene therapy, while using prophylaxis, with the number of treated bleeding episodes after gene therapy. On average, after gene therapy, participants had 4.1 fewer treated bleeding episodes per year. In this study, mathematical models were used to explore how differences in participant's physical characteristics, such as body weight or medical history, might influence the effectiveness of gene therapy. Even when considering differences in the participants' physical characteristics, the gene therapy reduced treated bleeding episodes by 3.6 events per year. This study confirms results originally presented from the valoctocogene roxaparvovec clinical trial and reinforces confidence in the ability of valoctocogene roxaparvovec to reduce bleeding outcomes for participants with hemophilia A.