Special Issue "Genetic, Functional and Therapeutic Aspects of Procoagulant and Anticoagulant Factors".

Pro- and anticoagulant factors are core components of hemostasis [...].

Factor XI deficiency: phenotypic age-related considerations and clinical approach towards bleeding risk assessment.

ABSTRACT: Factor XI (FXI) deficiency is a rare bleeding disorder that presents complex challenges in patient assessment and bleeding risk management. Despite generally causing mild to moderate bleeding symptoms, clinical manifestations can vary, and bleeding tendency does not always correlate with FXI plasma levels or genotype. Our manuscript delves into the age-related nuances of FXI deficiency across an individual's lifespan. We emphasize issues faced by specific groups, including neonates and females of reproductive age experiencing abnormal uterine bleeding and postpartum hemorrhage. Older patients present unique challenges and concerns related to the management of bleeding as well as thrombotic complications. The current assortment of diagnostic laboratory assays shows limited success in predicting bleeding risk in the perisurgical setting of patients with FXI deficiency. This review explores the intricate interplay between individual bleeding profiles, surgical sites, and FXI activity levels. We also evaluate the accuracy of existing laboratory assays in predicting bleeding and discuss the potential role of investigational global assays in perioperative assessment. Furthermore, we outline our suggested diagnostic approach to refine treatment strategies and decision making. Available treatment options are presented, including antifibrinolytics, replacement products, and recombinant activated FVII. Finally, we discuss promising nonreplacement therapies for the treatment of rare bleeding disorders that can potentially address the challenges faced when managing FXI deficiency-related bleeding complications.

Emicizumab prophylaxis in infants: Single-centre experience.

The hallmark of haemophilia A (HA) therapy is prophylaxis, aimed at spontaneous bleeding prevention. Emicizumab provides a viable alternative to intravenous factor replacement therapy. However, data on its use in infants are limited. This single-centre open arm prospective study reports on emicizumab prophylaxis in infants. We included severe HA patients under 1 year who started emicizumab prophylaxis since 2018, with longitudinal follow-up. The study collected data on demographics, clinical and laboratory variables, the occurrence of bleeding events, surgeries and treatment outcomes. Of the 27 enrolled infants, whose median age at prophylaxis initiation was 7 months, 24 primarily choose to start emicizumab therapy (3/27 switched from FVIII prophylaxis due to development of FVIII inhibitors). The median age for prophylaxis initiation decreased to 3 months in 2023. Following emicizumab initiation, the median calculated ABR decreased, and no intracranial haemorrhages were observed. Thrombin generation showed a significant improvement in peak height and endogenous thrombin potential at steady state after a loading period. Our study highlights a shift towards early prophylaxis in the era of non-replacement therapies. It underscores the need for continuous evaluation and refinement of treatment approaches, emphasizing personalized care and diligent monitoring in the evolving field of paediatric haemophilia care.

Bleeding phenotype and hemostatic evaluation by thrombin generation in children with Noonan syndrome: A prospective study.

BACKGROUND: This study aimed to evaluate the bleeding phenotype and to conduct a comprehensive hemostatic evaluation in individuals with Noonan syndrome (NS), a dominantly inherited disorder caused by pathogenic variants in genes associated with the Ras/MAPK signaling pathway. METHODS: Children with a genetically confirmed diagnosis of NS underwent clinical evaluation, routine laboratory tests, platelet function testing, and thrombin generation (TG) assessment. RESULTS: The study included 24 children. The most frequently reported bleeding symptoms were easy bruising and epistaxis, while bleeding complications were observed in 15% of surgical procedures. Various hemostatic abnormalities were identified, including platelet dysfunction, von Willebrand disease, and clotting factor deficiencies. Abnormal platelet function was observed in 50% of the patients, and significantly lower TG parameters were found compared to controls. However, no significant correlation was observed between bleeding symptoms and TG results. CONCLUSIONS: The study suggests that the bleeding diathesis in NS is multifactorial, involving both platelet dysfunction and deficiencies of plasma coagulation factors. The potential role of TG assay as an ancillary tool for predicting bleeding tendencies in individuals with NS undergoing surgery warrants further investigation.

Management of surgery in persons with hemophilia A receiving emicizumab prophylaxis: data from a national hemophilia treatment center.

Background: Persons with hemophilia A may require surgical procedures. Real-world data on invasive procedures in persons with hemophilia A receiving emicizumab prophylaxis are limited. Objectives: To evaluate the safety of invasive procedures in persons with hemophilia A receiving emicizumab prophylaxis and their outcomes in a longitudinally followed cohort. Methods: Data from medical records of persons with hemophilia A with and without factor VIII (FVIII) inhibitors longitudinally followed at our tertiary center, who received emicizumab prophylaxis and underwent all types of invasive procedures, were retrieved. Outcomes of interest were bleeding and thrombotic complications. Results: Overall, 35 patients underwent 56 invasive procedures, 18 (32.1%) were major. The median age was 36.3 years (IQR, 8.8-55.9 years); 12 patients (34.3%) were younger than 18 years at the time of procedure; 17 (48.6%) were patients with FVIII inhibitors. Among major procedures, orthopedic surgeries prevailed. All patients who underwent major procedures received factor replacement with either recombinant activated factor VII (patients with inhibitors) or FVIII (patients without inhibitors). Factor concentrates were administered prior to 32 (84.2%) of the minor procedures. Repeated doses were given according to international expert opinion recommendations and patients' condition.There were 7 bleeding events in 6 patients, 5 were major bleeds, including 1 patient who underwent a minor procedure without factor replacement. None of the patients experienced a thrombotic complication. Conclusion: Invasive procedures can be performed safely in patients receiving emicizumab prophylaxis with close surveillance after surgery. Factor concentrates may be advised in selected patients undergoing minor procedures.

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

Background: Using emicizumab in lieu of immune tolerance induction (ITI) for patients with hemophilia A (HA) and factor (F)VIII inhibitors has been well described. However, decisions regarding ITI initiation, regimen, and preservation of tolerance remain to be elucidated. Objectives: To study the course of FVIII inhibitors in patients with HA and a history of FVIII inhibitors receiving emicizumab prophylaxis. Methods: Patients with HA, with and without FVIII inhibitors, initiating emicizumab prophylaxis were prospectively followed up in our center. All patients with current or previous inhibitors were included in this analysis. Plasma samples for FVIII inhibitor assays were obtained every 3 to 6 months or following FVIII exposure. Patients documented annual bleeding rate and any FVIII exposure days (EDs). Results: Of 162 emicizumab-treated participants, 51 met the inclusion criteria. A decrease in annual bleeding rate was observed in all 51 participants followed up for a median of 3.3 years, with 31 breakthrough bleeding episodes reported in 22 of 51 participants. FVIII inhibitor level transiently increased following FVIII exposures in 5 of 15 failed ITI participants. Eight of 21 participants who did not undergo ITI were exposed to FVIII (1-2 EDs)), and 1 of these 8 participants demonstrated increased FVIII inhibitor levels after head trauma (following 1 ED). Among participants who underwent successful ITI, 8 of 15 patients were exposed to FVIII over a total of 13 EDs (1-2 ED(s) each) for traumatic breakthrough bleeds. In all these participants, inhibitor levels remained zero, indicating successful tolerance maintenance. Conclusion: Our longitudinal follow-up of emicizumab-treated patients with HA and FVIII inhibitors shows that occasional exposure to FVIII may induce a transient anamnestic response. Nonetheless, no FVIII inhibitor recurrence was noted following FVIII exposures in patients who underwent successful ITI.

3K3A-Activated Protein C Inhibits Choroidal Neovascularization Growth and Leakage and Reduces NLRP3 Inflammasome, IL-1ß, and Inflammatory Cell Accumulation in the Retina.

3K3A-Activated Protein C (APC) is a recombinant variant of the physiological anticoagulant APC with cytoprotective properties and reduced bleeding risks. We studied the potential use of 3K3A-APC as a multi-target therapeutic option for choroidal neovascularization (CNV), a common cause of vision loss in age-related macular degeneration. CNV was induced by laser photocoagulation in a murine model, and 3K3A-APC was intravitreally injected. The impact of 3K3A-APC treatment on myeloid and microglia cell activation and recruitment and on NLRP3 inflammasome, IL-1ß, and VEGF levels was assessed using cryosection, retinal flat-mount immunohistochemistry and vascular imaging. Additionally, we evaluated the use of fluorescein angiography as a surrogate marker for in vivo evaluation of the efficacy of 3K3A-APC treatment against leaking CNV lesions. Our results demonstrated that 3K3A-APC treatment significantly reduced the accumulation and activation of myeloid cells and microglia in the CNV area and decreased the NLRP3 and IL-1ß levels at the CNV site and the surrounding retina. Furthermore, 3K3A-APC treatment resulted in leakage regression and CNV growth suppression. These findings indicate that the anti-inflammatory activities of 3K3A-APC contribute to CNV inhibition. Our study suggests the potential use of 3K3A-APC as a novel multi-target treatment for CNV.

Association between Thrombin Generation and Clinical Characteristics in COVID-19 Patients.

INTRODUCTION: Coronavirus disease 2019 (COVID-19) disease is associated with coagulopathy and an increased risk of thrombosis. An association between thrombin generation (TG) capacity, disease severity, and outcomes has not been well described. METHODS: We assessed the correlation of TG with sequential organ failure assessment (SOFA) and sepsis-induced coagulopathy (SIC) scores and clinical outcomes by analysis of plasma samples obtained from hospitalized COVID-19 patients. RESULTS: 32 patients (68.8% male), whose median age was 69 years, were assessed, of whom only 3 patients did not receive anticoagulant therapy. D-dimers were uniformly increased. During hospitalization, 2 patients suffered thrombosis, 3 experienced bleeding, and 12 died. TG parameters from anticoagulated COVID-19 patients did not significantly differ from the values obtained from non-anticoagulated healthy controls. Patients who received higher than prophylactic doses of anticoagulant therapy had increased lag time (p = 0.003), lower endogenous thrombin potential (ETP) (p = 0.037), and a reduced peak height (p = 0.006). ETP correlated with the SIC score (p = 0.038). None of the TG parameters correlated with the SOFA score or were associated with mortality. CONCLUSION: TG was not associated with disease severity among patients hospitalized with COVID-19. However, a correlation between ETP and the SIC score was noted and deserves attention.

3K3A-Activated Protein C Prevents Microglia Activation, Inhibits NLRP3 Inflammasome and Limits Ocular Inflammation.

3K3A-Activated Protein C (APC) is a recombinant variant of the physiological anticoagulant APC with pleiotropic cytoprotective properties albeit without the bleeding risks. The anti-inflammatory activities of 3K3A-APC were demonstrated in multiple preclinical injury models, including various neurological disorders. We determined the ability of 3K3A-APC to inhibit ocular inflammation in a murine model of lipopolysaccharide (LPS)-induced uveitis. Leukocyte recruitment, microglia activation, NLRP3 inflammasome and IL-1ß levels were assessed using flow cytometry, retinal cryosection histology, retinal flatmount immunohistochemistry and vascular imaging, with and without 3K3A-APC treatment. LPS triggered robust inflammatory cell recruitment in the posterior chamber. The 3K3A-APC treatment significantly decreased leukocyte numbers and inhibited leukocyte extravasation from blood vessels into the retinal parenchyma to a level similar to controls. Resident microglia, which underwent an inflammatory transition following LPS injection, remained quiescent in eyes treated with 3K3A-APC. An inflammation-associated increase in retinal thickness, observed in LPS-injected eyes, was diminished by 3K3A-APC treatment, suggesting its clinical relevancy. Finally, 3K3A-APC treatment inhibited inflammasome activation, determined by lower levels of NLRP3 and its downstream effector IL-1ß. Our results highlight the anti-inflammatory properties of 3K3A-APC in ocular inflammation and suggest its potential use as a novel treatment for retinal diseases associated with inflammation.

Anti-TFPI for hemostasis induction in patients with rare bleeding disorders, an ex vivo thrombin generation (TG) guided pilot study.

BACKGROUND: Rare bleeding disorders (RBD) are inherited coagulopathies, whose hemostatic control is based upon replacement therapy. Marstacimab (PF-06741086) is a human monoclonal IgG that targets the Kunitz2 domain of tissue factor pathway inhibitor [TFPI]. Marstacimab is currently in development for bleeding prophylaxis in patients with hemophilia. OBJECTIVES: To assess the potential impact of Marstacimab upon thrombin generation (TG) in RBD patients' plasma samples. RESULTS: Our cohort included 18 RBD patients, with severe deficiencies: 5 Von Willebrand Disease (VWD) type 3, 4 FVII, 3 FXI, 2 FXIII deficiency and 1 patient with: FX, FV + FVIII, Fibrinogen, combined vitamin K dependent factors' deficiency. Citrated samples from RBD patients were collected and spiked with Marstacimab, TG was measured by calibrated automated thrombogram. Among all patients a reduced baseline TG was observed as compared to controls. Improvement of median (lag time, peak and ETP was observed in Marstacimab spiked samples from 8 min, 99 nM, 1116 nMx min to 5.5 min, 194 nM,1614 nMx min, respectively. None of the values measured among RBD patients exceeded normal controls. CONCLUSION: These in vitro data suggest that Marstacimab may serve as a promising approach for restoring the hemostatic balance in various RBD, though potential clinical implications should be further investigated.

Real-World Data on Bleeding Patterns of Hemophilia A Patients Treated with Emicizumab.

Emicizumab (Hemlibra™) is approved for prophylaxis of hemophilia A (HA) patients. The HAVEN studies addressed bleeding reduction in emicizumab-treated patients, but real-world data on bleeding patterns during emicizumab therapy are lacking. We aimed to compare the occurrence of breakthrough bleeding at different time points, starting from emicizumab initiation. This longitudinal prospective observational cohort study included HA patients (n = 70, aged 1 month to 74.9 years) that completed at least 18 months of follow-up in our center. We analyzed the number of spontaneous and traumatic bleeds during selected time points of the study ("bleeding periods"). The percentage of traumatic and spontaneous bleeding episodes was not significantly different among "bleeding periods" (P = 0.053 and P = 0.092, respectively). Most trauma-related treated bleeds resulted from either hemarthrosis (53%) or head trauma (33%). Spontaneous bleeding episodes were mostly hemarthroses (80%). Potential associations of the patients' age, annualized bleeding rate before emicizumab treatment, and the presence of inhibitors with spontaneous bleed occurrence were analyzed with binomial logistic regression. The odds of bleeding while on emicizumab increased by a factor of 1.029 (P = 0.034) for every one year of age. Conclusions: Our real-world data revealed that the risk of bleeding persists, especially in older patients, despite therapy with emicizumab. These data may help clinicians in counselling their patients and in planning their management.

Molecular Mechanisms of Skewed X-Chromosome Inactivation in Female Hemophilia Patients-Lessons from Wide Genome Analyses.

INTRODUCTION: Hemophilia A (HA) is an X-linked bleeding disorder caused by factor VIII (FVIII) deficiency or dysfunction due to F8 gene mutations. HA carriers are usually asymptomatic because their FVIII levels correspond to approximately half of the concentration found in healthy individuals. However, in rare cases, a carrier may exhibit symptoms of moderate to severe HA primarily due to skewed inactivation of her non-hemophilic X chromosome. AIM: The aim of the study was to investigate X-chromosome inactivation (XCI) patterns in HA carriers, with special emphasis on three karyotypically normal HA carriers presenting with moderate to severe HA phenotype due to skewed XCI, in an attempt to elucidate the molecular mechanism underlying skewed XCI in these symptomatic HA carriers. The study was based on the hypothesis that the presence of a pathogenic mutation on the non-hemophilic X chromosome is the cause of extreme inactivation of that X chromosome. METHODS: XCI patterns were studied by PCR analysis of the CAG repeat region in the HUMARA gene. HA carriers that demonstrated skewed XCI were further studied by whole-exome sequencing (WES) followed by X chromosome-targeted bioinformatic analysis. RESULTS: All three HA carriers presenting with the moderate to severe HA phenotype due to skewed XCI were found to carry pathogenic mutations on their non-hemophilic X chromosomes. Patient 1 was diagnosed with a frameshift mutation in the PGK1 gene that was associated with familial XCI skewing in three generations. Patient 2 was diagnosed with a missense mutation in the SYTL4 gene that was associated with familial XCI skewing in two generations. Patient 3 was diagnosed with a nonsense mutation in the NKAP gene that was associated with familial XCI skewing in two generations. CONCLUSION: Our results indicate that the main reason for skewed XCI in our female HA patients was negative selection against cells with a disadvantage caused by an additional deleterious mutation on the silenced X chromosome, thus complicating the phenotype of a monogenic X-linked disease. Based on our study, we are currently offering the X inactivation test to symptomatic hemophilia carriers and plan to expand this approach to symptomatic carriers of other X-linked diseases, which can be further used in pregnancy planning.

Novel mutation in coagulation factor VII (Carmel mutation): Identification and characterization.

BACKGROUND: Measurement of factor VII (FVII) activity does not enable prediction of bleeding tendency in individuals with inherited FVII deficiency. OBJECTIVE: To characterize the molecular and functional features of FVII in a family with FVII deficiency and correlate them with the bleeding tendency. PATIENTS/METHODS: We studied 7 family members with very low FVII activity using prothrombin time (PT), activated factor VII (FVIIa), FVII activity level, and thrombin generation. The factor 7 gene was sequenced and the mutation was analyzed by prediction software. RESULTS: The proband has very low FVII activity (0%-4%), with PT ranging between 5% to 18% depending on the tissue factor (TF) origin. Direct sequencing demonstrated a single homozygous nucleotide substitution G > A in exon 6, predicting a novel missense mutation Cys164Tyr. Three members of the family were found to be heterozygous carriers of this mutation. One of them was a compound heterozygote, carrying both the Cys164Tyr and Ala244Val mutation (linked to Arg353Gln polymorphism). Her FVII activity and antigen levels were 3%-7% and 8%, respectively. The other heterozygous carriers demonstrated FVII activity of 41%-54%, FVII antigen of 46%-66%, and FVIIa activity of 30%. FVIIa was undetectable in the homozygous and compound heterozygous subjects. Thrombin generation was normal in the presence of calcium, but no response to TF addition was observed in the homozygous proband, and a reduced response was observed in the compound heterozygous subject. CONCLUSION: The patient homozygous for the "Carmel" mutation has mild clinical manifestations despite very low FVII activity, which correlates with thrombin generation results.

Emicizumab prophylaxis: Prospective longitudinal real-world follow-up and monitoring.

INTRODUCTION: Real-world data on prophylaxis of severe haemophilia A (HA) patients treated by emicizumab are scarce. AIM: To study the efficacy and safety of longitudinal emicizumab prophylaxis and assess laboratory monitoring correlations in a large patient cohort. METHODS: HA patients with and without FVIII inhibitors, initiating emicizumab prophylaxis, were prospectively enrolled. Bleeding, adverse events and surgeries were documented. FVIII inhibitors, emicizumab levels and thrombin generation (TG) were sequentially measured. RESULTS: A total of 107 patients, including 58 children (whose median (IQR) age was 6 (1-11) years) with severe HA, composed the study cohort. Twenty-nine per cent (31/107) of our HA patients had FVIII inhibitors. Patients were followed for a median of 67 weeks (up to 144 weeks). Fifty-three patients, whose median follow-up was 53 weeks, experienced zero bleeds. Most bleeds (94%) among children were trauma-related, whereas 61% of adults sustained spontaneous joint bleeds. Four patients experienced major bleeds, with a fatal outcome in one infant, who also presented with central venous line thrombosis. No other serious adverse events were encountered. Seven patients have decided to stop emicizumab treatment for various reasons. Emicizumab plasma levels increased after emicizumab prophylaxis initiation, and values were maintained during follow-up, in all but one patient, suspected of anti-drug antibodies. A significant reduction of FVIII inhibitor levels was noted among inhibitor patients. TG was increased and sustained yet could not prognosticate bleeding risk. CONCLUSION: Emicizumab prophylaxis was mostly well tolerated, although 50% of patients experienced breakthrough bleeds. Routine TG monitoring is not obligatory, and further studies are warranted in selected patient populations.

Activated Protein C (APC) and 3K3A-APC-Induced Regression of Choroidal Neovascularization (CNV) Is Accompanied by Vascular Endothelial Growth Factor (VEGF) Reduction.

The activated protein C (APC) ability to inhibit choroidal neovascularization (CNV) growth and leakage was recently shown in a murine model. A modified APC, 3K3A-APC, was designed to reduce anticoagulant activity while maintaining full cytoprotective properties, thus diminishing bleeding risk. We aimed to study the ability of 3K3A-APC to induce regression of CNV and evaluate vascular endothelial growth factor (VEGF) role in APC's activities in the retina. CNV was induced by laser photocoagulation on C57BL/6J mice. APC and 3K3A-APC were injected intravitreally after verification of CNV presence. CNV volume and vascular penetration were evaluated on retinal pigmented epithelium (RPE)-choroid flatmount by fluorescein isothiocyanate (FITC)-dextran imaging. VEGF levels were measured using immunofluorescence anti-VEGF staining. We found that 3K3A-APC induced regression of pre-existing CNV. VEGF levels, measured in the CNV lesion sites, significantly decreased upon APC and 3K3A-APC treatment. Reduction in VEGF was sustained 14 days post a single APC injection. As 3K3A-APC retained APCs' activities, we conclude that the anticoagulant properties of APC are not mandatory for APC activities in the retina and that VEGF reduction may contribute to the protective effects of APC and 3K3A-APC. Our results highlight the potential use of 3K3A-APC as a novel treatment for CNV and other ocular pathologies.

Emicizumab prophylaxis in haemophilia patients older than 50 years with cardiovascular risk factors: Real-world data.

INTRODUCTION: Emicizumab (Hemlibra™) is approved for prophylaxis of Haemophilia A (HA) patients with and without inhibitors. However, real-world data on emicizumab use in the elderly HA patients with concomitant cardiovascular risk factors are lacking. AIM: To evaluate the safety and efficacy of emicizumab in a real-world cohort of elderly HA patients. METHODS: A prospective longitudinal observational study on HA patients over 50 years old treated, followed and monitored during emicizumab prophylaxis was conducted. We documented any bleeding or adverse events and collected plasma samples for emicizumab levels, aPTT and thrombin generation (TG). RESULTS: Seventeen HA patients (2 with inhibitor), whose median age was 62.4 years (range: 51.5-77.1) composed the cohort, including 9/17 with multiple cardiovascular risk factors (high risk group). Seven patients had chronic HIV infection. The median follow-up of our cohort was 400 days (range 89-805, IQR 211-479 days). The median annualized bleeding rate (ABR) significantly decreased for all patients. Among patients who displayed significant bleeding tendencies, emicizumab steady state levels as well as TG were lower as compared with the group. The ABR of four patients concomitantly treated by antiplatelet agents was significantly higher compared with the rest of the cohort. Neither thrombosis nor thrombotic microangiopathy (TMA) was encountered. CONCLUSIONS: Emicizumab prophylaxis for HA patients older than 50 years including those with cardiovascular risk factors was well tolerated. As lower emicizumab and TG levels were observed among bleeding patients, we suggest that monitoring laboratory assays could be of value within this age group.

The potential role of emicizumab prophylaxis in severe von Willebrand disease.

BACKGROUND: Severe von Willebrand disease (VWD) may be associated with chronic joint damage and may require prophylactic therapy. Emicizumab is a humanized bispecific antibody, which mimics the function of coagulation factor VIII (FVIII), and it has been approved for prophylaxis in hemophilia A. METHODS: This is the first study assessing the potential future role of emicizumab as an alternative prophylactic treatment in patients with severe VWD, based upon a thrombin generation (TG) ex vivo analysis. We report 51 weeks of successful off label emicizumab prophylaxis in a child with severe VWD and recurrent hemarthroses and progressive arthropathy despite adherence to previous prophylaxis with replacement therapy. RESULTS AND CONCLUSIONS: Our work demonstrated that ex vivo spiking with emicizumab increased TG in plasma from patients with type 3 VWD. Similar TG results were observed in our treated patient, whose therapy was well tolerated without any adverse events. Both in vitro and ex vivo TG data support sufficient hemostasis without exceeding the range seen in healthy volunteers. Further collaborative studies on the efficacy and safety of emicizumab prophylaxis in severe VWD is warranted.

A Single Low-Dose of Methylphenidate Improves Abnormal Visual Field Testing.

PURPOSE: To evaluate the effect of methylphenidate on visual field testing in healthy adults with abnormal visual field results. METHODS: This prospective, randomized, controlled interventional clinical trial comprised all patients who had abnormal visual field test results and normal eye examination and ophthalmic history. Eligible patients were randomly assigned to either the study group or the control group. All patients repeated their visual field testing. Study group patients received a single dose of 10 mg methylphenidate prior to that. The main outcome measures were the percent difference in mean deviation and pattern standard deviation between the second and first visual fields. RESULTS: The methylphenidate group had greater improvement in all parameters. Mean deviation improved by median 68% (IQR 19%-78%) in the methylphenidate group vs. 27% [-5% to 55%] in the controls. However, this was not statistically significant (p = .83). Pattern standard deviation improved by median 49% (22%-59%) vs. 7% [-9% to 45%], respectively (p = .012). The visual fields were also reviewed by 3 masked experienced ophthalmologists. They indicated that the second visual field improved in 76.2% of the methylphenidate group vs. 48.5% of the controls (p = .04). A normal repeat visual field occurred in 57.7% vs. 21.2%, respectively. A subgroup analysis of patients with prior experience in visual field testing yielded an even more striking improvement in the methylphenidate group vs. controls. CONCLUSIONS: A single low dose of methylphenidate can improve visual field testing in subjects without ocular pathology, and even more in those with prior experience in perimetry.

Emicizumab treatment and monitoring in a paediatric cohort: real-world data.

Real-world data on emicizumab use and monitoring in paediatric severe haemophilia A (HA) patients are scarce. We therefore sought to evaluate safety, efficacy, and laboratory monitoring of emicizumab prophylaxis in a cohort of 40 children with severe HA, including 22 non-inhibitor patients and nine infants younger than one year. Bleeding, trauma, adverse events, and surgeries were documented during a median follow-up of 45 weeks. Emicizumab levels, activated partial thromboplastin time (aPTT) values, and thrombin generation were measured before and during therapy. Twenty patients experienced zero bleeds. All bleeding was trauma-related, and bleeding risk was positively correlated with the length of emicizumab prophylaxis. Sixteen surgical interventions were performed in 12 patients, with no thrombotic complications or thrombotic microangiopathy. Prolonged aPTT values normalised after emicizumab initiation, correlating with an increase in emicizumab plasma levels. Elevation in the thrombin generation was observed following emicizumab prophylaxis, with lower values recorded in younger infants. Emicizumab prophylaxis was safe and well tolerated. As all bleedings were trauma-related, laboratory monitoring could not predict bleeding risk. Our results do not support routine thrombin generation monitoring in children treated by emicizumab, yet further studies are warranted in the context of surgical procedures.

Thrombin generation in plasma of patients with haemophilia A and B with inhibitors: Effects of bypassing agents and antithrombin reduction.

Antithrombin (AT) reduction has been shown to improve thrombin generation (TG) in haemophilia with or without inhibitors. As treatment with bypassing agents (BPAs) may be required in patients with breakthrough bleeding while receiving AT-lowering therapy, we assessed TG in platelet-poor plasma samples from haemophilia patients in the presence of BPA (recombinant activated factor VII [rFVIIa; 1.25 or 2.5 µg mL-1] or activated prothrombin complex concentrate [aPCC; 0.5 or 1 U mL-1]) and AT reduction (anti-AT antibody). Mean ± SEM baseline peak thrombin height was 19.9 ± 4.3 nM in plasma from haemophilia patients (n = 12) and 230.5 ± 9.8 nM in healthy males (n = 24). Reduced AT improved mean peak thrombin height in haemophilia patient plasma to 75.4 ± 17.4 nM. Spiking of 90% AT-reduced haemophilia patient plasma with 2.5 µg mL-1 rFVIIa or 1 U mL-1 aPCC increased the mean peak thrombin height to 82.5 ± 12 nM and 134.8 ± 18.7 nM, respectively. Peak thrombin levels did not exceed the range for healthy volunteers when plasma samples from haemophilia patients with in vitro AT reduction were treated with BPAs, suggesting the potential use of BPAs in conjunction with AT reduction. Further clinical investigations are needed to confirm the safety of this approach.