Factor 4 Research Articles

Inhibition of Ehrlich ascites carcinoma growth by melatonin: Studies with micro-CT.

Melatonin is a versatile indolamine synthesized and secreted by the pineal gland in response to the photoperiodic information received by the retinohypothalamic signaling pathway. Melatonin has many benefits, such as organizing circadian rhythms and acting as a powerful hormone. We aimed to show the antitumor effects of melatonin in both in vivo and in vitro models through the mammalian target of rapamycin (mTOR) signaling pathway and the Argyrophilic Nucleolar Regulatory Region (AgNOR), using the Microcomputed Tomography (Micro CT). Ehrlich ascites carcinoma (EAC) cells were administered into the mice by subcutaneous injection. Animals with solid tumors were injected intraperitoneally with 50 and 100 mg/kg melatonin for 14 days. Volumetric measurements for the taken tumors were made with micro-CT imaging, immunohistochemistry (IHC), real-time polymerase chain reaction (PCR) and AgNOR. Statistically, the tumor tissue volume in the Tumor+100 mg/kg melatonin group was significantly lower than that in the other groups in the data obtained from micro-CT images. In the IHC analysis, the groups treated with Tumor+100 mg/kg melatonin were compared when the mTOR signaling pathway and factor 8 (F8) expression were compared with the control group. It was determined that there was a significant decrease (p < 0.05). Significant differences were found in the total AgNOR area/nuclear area (TAA/NA) ratio in the treatment groups (p < 0.05). Furthermore, there were significant differences between the amount of mTOR mRNA for the phosphatidylinositol 3-kinase (PI3K), AKT Serine/Threonine Kinase (PKB/AKT) genes (p < 0.05). Cell apoptosis was evaluated with Annexin V in an in vitro study with different doses of melatonin; It was observed that 100 µg/mL melatonin dose caused an increase in the apoptotic cell death. In this study, we have reported anti-tumor effects of melatonin in cell culture studies as well as in mice models. Comprehensive characterization of the melatonin-mediated cancer inhibitory effects will be valuable in advancing our fundamental molecular understanding and translatability of pre-clinical findings to earlier phases of clinical trials.

A novel factor IXa–specific enzyme-linked immunosorbent assay detects factor IXa in human plasma

BackgroundFactor (F)IXa activity has been detected in human plasma and may impact thrombotic risk. Current FIXa activity assays are complex and cumbersome. ObjectivesTo develop a reproducible enzyme-linked immunosorbent assay (ELISA) using a novel monoclonal antibody that detects total FIXa in human plasma. MethodsA monoclonal antibody was raised against the new N-terminus exposed upon activation of FIX to FIXa by cleavage after R226. This antibody is specific for FIXa protease and does not recognize FIX zymogen or FIXα. The antibody was used to develop a FIXa-specific ELISA capable of quantifying total FIXa (free FIXa and FIXa-antithrombin complex) in human plasma. Total FIXa quantified using the ELISA was compared to that of FIXa-antithrombin quantified using modifications of a previously described ELISA. ResultsThe FIXa-specific ELISA was reproducible and quantified total FIXa in human plasma. Total FIXa levels correlated with FIXa-antithrombin levels. ConclusionA monoclonal antibody was developed that specifically detects human FIXa protease. A FIXa-specific ELISA using the new antibody is capable of reproducibly measuring total FIXa in human plasma (both free FIXa and FIXa-antithrombin). This assay should facilitate the evaluation of total FIXa levels in a variety of clinical circumstances.

Complete F9 Gene Deletion, Duplication, and Triplication Rearrangements: Implications for Factor IX Expression and Clinical Phenotypes.

Factor IX (FIX) plays a critical role in blood coagulation. Complete deletion of F9 results in severe hemophilia B, whereas the clinical implications of complete F9 duplication and triplication remain understudied. To investigate the rearrangement mechanisms underlying complete F9 deletion (cases 1 and 2), duplication (cases 3 and 4), and triplication (case 5), and to explore their association with FIX expression levels and clinical impacts. Plasma FIX levels were detected using antigen and activity assays. CNVplex technology, optical genome mapping, and long-distance polymerase chain reaction were employed to characterize the breakpoints of the chromosomal rearrangements. Cases 1 and 2 exhibited FIX activities below 1%. Case 3 displayed FIX activities within the reference range. However, cases 4 and 5 showed a significant increase in FIX activities. Alu-mediated nonallelic homologous recombination was identified as the cause of F9 deletion in case 1; FoSTeS/MMBIR (Fork Stalling and Template Switching/microhomology-mediated break-induced replication) contributed to both F9 deletion and tandem duplication observed in cases 2 and 3; BIR/MMBIR (break-induced replication/microhomology-mediated break-induced replication) mediated by the same pair of low-copy repeats results in similar duplication-triplication/inversion-duplication (DUP-TRP/INV-DUP) rearrangements in cases 4 and 5, leading to complete F9 duplication and triplication, respectively. Large deletions involving the F9 gene exhibit no apparent pattern, and the extra-hematologic clinical phenotypes require careful analysis of other genes within the deletion. The impact of complete F9 duplication and triplication on FIX expression might depend on the integrity of the F9 upstream sequence and the specific rearrangement mechanisms. Notably, DUP-TRP/INV-DUP rearrangements significantly elevate FIX activity and are closely associated with thrombotic phenotypes.

The current challenges faced by people with hemophilia B.

Hemophilia B (HB) is a rare, hereditary disease caused by a defect in the gene encoding factor IX (FIX) and leads to varying degrees of coagulation deficiency. The prevailing treatment for people with HB (PWHB) is FIX replacement product. The advent of recombinant coagulation products ushered in a new era of safety, efficacy, and improved availability compared with plasma-derived products. For people with severe HB, lifelong prophylaxis with a FIX replacement product is standard of care. Development of extended half-life FIX replacement products has allowed for advancements in the care of these PWHB. Nonetheless, lifelong need for periodic dosing and complex surveillance protocols pose substantive challenges in terms of access, adherence, and healthcare resource utilization. Further, some PWHB on prophylactic regimens continue to experience breakthrough bleeds and joint damage, and subpopulations of PWHB, including women, those with mild-to-moderate HB, and those with inhibitors to FIX, experience additional unique difficulties. This review summarizes the current challenges faced by PWHB, including the unique subpopulations; identifying the need for improved awareness, personalized care strategies, and new therapeutic options for severe HB, which may provide future solutions for some of the remaining unmet needs of PWHB.

Real-World Amount of Clotting Factor Concentrates Dispensed and Annual Medical Expenditures for Japanese Patients with Hemophilia B.

Until extended half-life (EHL) factor IX (FIX) concentrates became available in Japan in 2010, patients with hemophilia B received intravenous FIX replacement therapy with standard half-life (SHL) FIX concentrates. To investigate the amount of factor dispensed and the associated medical expenditures for the treatment of hemophilia B in the real-world clinical setting in Japan. This retrospective study comprised patients with hemophilia B (N=197) who had filled prescriptions for FIX concentrates reported in Japan's Medical Data Vision database from 2015 to 2019. Patients were included if they had 2 or more prescriptions for the same FIX concentrates within the first 6 months of the study period and the interval between prescriptions was at least 2 weeks. Since 2015, there was a decrease in the proportion of patients using SHL FIX concentrates and a corresponding increase in international units of dispensed EHL FIX concentrates. Median annualized dispensed dosages (IU/kg body weight) of EHL FIX concentrates were lower than for SHL concentrates for outpatient use only. Annual total health care expenditures per patient and annual expenditures for prescribed FIX concentrates increased each year during the study period. Following a switch from an SHL to an EHL concentrate, the median amount of prescribed FIX concentrate decreased slightly, although median total health care expenditures and FIX concentrate expenditures increased. In the real-world setting in Japan, medical expenditures and the proportion of patients prescribed EHL FIX concentrates for the treatment of hemophilia B have increased.

Genetic associations with mixed neuropathologies in the aging brainGenetic associations with mixed neuropathologies in the aging brain

AbstractBackground““Mixed” neuropathologies (NPs) are common in aged brains. Classic Alzheimer’s disease neuropathologic change (ADNC) proteinopathies are amyloid‐β plaques and tau neurofibrillary tangles (NFTs). In addition, α‐synuclein and TDP‐43 are also key proteinaceous disease markers, and cerebrovascular diseases (CVDs) often coexist. Although the scientific problems regarding mixed NPs are increasingly recognized, genetic associations with mixed NPs have not been well‐investigated. In this study, we applied item response theory (IRT) to optimize the clustering and combination of mixed NPs and examined the genetic associations.MethodNP data were drawn from the National Alzheimer’s Coordinating Center (NACC) NP v10‐11 forms through the March 2022 data freeze, including Thal phase ratings (A score); Braak NFT stage (B score); CERAD neuritic plaque scores (C score); Lewy bodies (LBs); TDP‐43; hippocampal sclerosis (HS); cerebral amyloid angiopathy (CAA); infarct and lacunes; microinfarcts; atherosclerosis of the circle of Willis; and brain arteriolosclerosis. We determined dominant pathology patterns in 1,228 participants who had no missing data using a multidimensional graded response model within the IRT framework. The NACC NP data were linked to the U.S. Alzheimer’s Disease Research Centers genetic data provided by the Alzheimer’s Disease genetic Consortium.ResultFrom the leave one out cross validation simulation, the model fitness tests showed that the 4‐factor model had fewer differences from the data than the other models. As shown in Figure, the predominant NPs were TDP‐43 and HS for factor 1 (F1), CVDs other than CAA for factor 2 (F2), A, B, and C scores and CAA for factor 3 (F3), and LBs for factor 4 (F4). The TMEM106B locus was genome‐wide significant with F1 (TDP‐43/HS) and the APOE locus was genome‐wide significant with F3 (ADNC/CAA) after adjusted for age at death, sex, and other factor scores. The SDK1 and FMNL2 loci were not genome‐wide significant, but had noteworthy associations with F2 (CVDs).ConclusionOur new approach to create mixed NP scores could detect the TMEM106B and APOE loci as TDP‐43/HS related and ADNC related regions, respectively. Although previous studies reported SDK1 as an ADNC related gene, we showed that the gene may be associated with CVDs.

Real-world data on the use of emicizumab in patients with haemophilia A with and without inhibitors in Singapore.

Emicizumab is a bispecific monoclonal antibody that mimics the function of factor VIII by binding to factor IXa and factor X to achieve haemostasis in haemophilia A. The long half-life and subcutaneous mode of administration makes emicizumab a compelling treatment option for bleeding prophylaxis. There is still limited real-world data on its use and management considerations, especially during surgical procedures. The objective of the study is to describe the real-world experience of emicizumab in a cohort of adult and paediatric haemophilia A patients in Singapore, including its use in the periprocedural setting. This was an observational study conducted at the 2 main haemophilia treatment centres in Singapore. All haemophilia A patients who commenced treatment with emicizumab before 1 July 2022 were recruited. A total of 18 patients with haemophilia A were included in this study. Ten (55.6%) patients had active inhibitors. The median annual bleeding rate for all patients before emicizumab use was 4.5 events (interquartile range [IQR] 2.8-8.3) compared with 0 events (IQR 0-0) after emicizumab was commenced (P=0). There were no adverse events of venous or arterial thrombosis, thrombotic microangiopathy, or death. A total of 6 procedures in 5 patients were performed during the study period with no major bleeding complications. Emicizumab effectively protects against bleeding in haemophilia A patients with and without inhibitors, including in children less than 12 years old. More studies are required to address clinical nuances, such as periprocedural management and the role of immune tolerance in patients with inhibitors on emicizumab.

Extravascular Factor IX Pool Fed By Prophylaxis Is a True Hemostatic Barrier Against Bleeding

Factor IX (FIX) can bind to type-IV collagen in the endothelial basement membrane and diffuse into extravascular spaces. Previous studies in rodents have reported a large biodistribution of FIX. However, the potential hemostatic activity of extravascular FIX and its role in protecting against joint bleeds have not been demonstrated. The capacity of 4 different FIX molecules (plasma derived [pd] and recombinants) to bind type I and type IV collagen was studied here. FIX molecules were also administered intravenously at doses of 50 to 3000 IU/kg in FIX knock-out (KO) mice. A specific FIX signal was detected in immunohistochemistry in the liver as well as in muscles and knee joints with recombinant FIX molecules injected at 1000 and 3000 IU/kg but not at the usual clinical doses of 50-100 IU/kg, while pdFIX generated a FIX signal at all doses including 50 IU/kg. After five 100 IU/kg daily infusions of rFIX, a clear accumulation of FIX was seen in the liver and joints of animals having received 5-day daily FIX infusions with all FIX molecules, with a higher FIX labelling intensity compared to that observed after a single infusion of FIX 100 IU/kg or a single infusion of FIX 500 IU/kg. The extravascular procoagulant activity of FIX was assessed in saphenous vein bleeding assays performed 7 days after a single infusion of FIX 100 IU/kg. An additional group of FIX KO mice received intravenously for 5 days a single daily dose of 100 IU/Kg of one the four types of FIX concentrate in order to mimic prophylaxis. The number of clots formed in 15 minutes was significantly greater in mice having received prophylaxis during 5 days with 100 IU/kg FIX compared to untreated FIX KO mice (p=0.009) and to mice having received a single infusion of FIX 100 IU/kg (p&amp;lt;0.0001) (Figure 1). Taken together, these results show that in individuals with severe hemophilia B receiving regular prophylaxis with FIX, extravascular accumulation of FIX over time may have a significant impact on the coagulation capacity and protection towards bleeding.

Thrombosis Caused By a Novel Coagulation Factor IX Mutation (FIX Shanghai II)

Most thrombophilia patients are caused by insufficient suppression of coagulation reactions, which could be either mediated by deficiencies of protein C, protein S,antithrombin, or inhibition-resistant coagulation factor mutants, such as Factor V Leiden and prothrombin Yukuhashi. The thrombosis caused by coagulation factor mutants with increased procoagulant activity is very rare and so far only two Factor IX (FIX) variants involving residue Arg384, FIX Padua (p.Arg384Leu) and Shanghai (p.Arg384Gln), which increased FIX activity by up to 8 folds, had been reported to be associated with the incidence of thrombosis. In a young male venous thrombosis patient we had identified a novel F9 gene missense mutation c.1018G&amp;gt;A, resulting in p. Glu340Lys substitution (designated as FIX Shanghai II). The patient's APTT time was 28.9 seconds (normal reference 22.3~38.7s), and his PT was also within the normal reference range (11.5 seconds, normal reference 10.0~16.0s). Although the patient had the FIX: Ag comparable to the normal reference, 128.20±6.07%, the his FIX:C was around 201.69±10.38% of normal control (normal reference 50~150%). Thrombin generation assay (TGA) showed that compared with normal control, the patient had a shorter Lag time (2.67 vs 3.33 min), elevated ETP (1649.43 vs 1311.62 nM*min), and higher Peak value (387.34 vs 200.86 nM), indicating increased global coagulation activity of the patient. The activity of protein C, protein S, and antithrombin were all within the normal reference ranges and the patient was negative for antiphospholipid antibodies. Consistent with the patient's coagulation laboratory manifestations, the purified recombinant FIX Glu340Lys mutant showed 1.82 folds higher procoagulant activity than wild type FIX as determined by FIX:C/FIX:Ag ratio. The recombinant FIX Shanghai II mutant can be converted into FIXa by activated factor XI (FXIa) in a similar fashion as FIX WT. The kinetic study of FIXa-catalyzed FX activation showed that p. Glu340Lys mutation led to accelerated FX activation by FIXa. The p.Glu340Lys mutation also enhanced the procoagulant activity of previously reported thrombosis-causing FIX mutants, FIX Shanghai and Padua, in a similar fashion as it did on FIX WT. The FIX:C/FIX:Ag ratio of double mutants containing Glu340Lys and Arg384Gln (FIX Shanghai) or Arg384Leu (FIX Padua) was about twice of FIX Shanghai or Padua alone, 11.48- and 22.53-folds vs 6.16- and 8.13- folds higher than FIX WT respectively.

HIV Comorbid Infection and Liver-Directed AAV-Based Gene Therapy in Adults with Severe and Moderately Severe Hemophilia B: Efficacy and Safety Results from Phase 2b and the Pivotal Phase 3 HOPE-B Trials 3 Years after Administration of a Single Dose of Etranacogene Dezaparvovec

Introduction: People living with HIV represent an important subset within the hemophilia community. Concerns about increased hepatotoxicity of liver-directed adeno-associated viral (AAV) vectors in patients receiving potentially hepatotoxic HIV medications (eg, efavirenz) have excluded this population from participating in many of gene therapy hemophilia trials. However, adult patients with hemophilia B (PwHB) with controlled HIV comorbid infection were not excluded from enrollment in phase 2b (NCT03489291) and phase 3 HOPE-B (NCT03569891) trials evaluating the efficacy and safety of etranacogene dezaparvovec (formerly AMT-061), an AAV5 vector containing a codon-optimized, highly active factor IX (FIX) Padua R338L transgene under the control of the liver-specific promoter LP-1. Aim: The aim of this ad hoc analysis was to evaluate the efficacy and safety of etranacogene dezaparvovec in the subset of adult PwHB with comorbid infection with HIV from both the phase 2b and the phase 3 HOPE-B trials. Methods: A single IV administration of 2x10 13 gc/kg etranacogene dezaparvovec was administered to adult patients with severe or moderately severe hemophilia B in phase 2b and phase 3 HOPE-B trials. Patients with HIV infections uncontrolled by antiviral therapy demonstrated by CD4+ counts ≤200/µL were excluded from the studies. Individual safety and efficacy outcomes of participants with controlled HIV infection treated with etranacogene dezaparvovec were assessed. Liver enzyme levels and aPTT-based FIX activity levels were analyzed by a central laboratory. Descriptive statistical analyses were used to report all results with a data cut at 3 years post administration of etranacogene dezaparvovec. Results: Among 57 participants who received etranacogene dezaparvovec in phase 2b and phase 3 HOPE-B trials, 5 had comorbid HIV infection (median [range] age 49 years [38-54]), of whom 4 had a history of treated hepatitis C virus with a negative viral load. Three out of 5 participants with comorbid HIV infection had pre-existing AAV5 neutralizing antibodies with median [range] titer of 20 [0-99]. Annualized bleeding rate (ABR) decreased post treatment compared with previous FIX prophylaxis regimen (with extended half-life FIX products) for all HIV+ patients; median [range] ABR during FIX prophylaxis was 5 [1-10.4]. Two patients recorded no bleeds in the 36 months after receiving etranacogene dezaparvovec treatment, and the overall median [range] ABR post treatment was 0.64 [0-5.0]. FIX activity levels in these participants were apparent from week 3 and were maintained in the mild/normal range for 4/5 (80%) participants (Figure 1). Median [range] uncontaminated endogenous FIX at 3 years post treatment was 32.3% [31.5%-58%]. Two patients had contaminated FIX measurements at 36 months (1 returned to prophylaxis shortly after 24 months and the other took on-demand replacement therapy the day before the 36-month visit). No treatment-related serious adverse events (AEs) occurred. Only 7 treatment-related AEs were reported in 3 participants. Treatment-related ALT elevation of moderate severity occurred in Participant 5 (20%, similar to patients without HIV comorbid infection) at 35 days post treatment and resolved within 15 days with the use of corticosteroids. This patient eventually had his FIX levels declined to 2-5% range; his bleeding phenotype returned, and he resumed prophylaxis per protocol at month 30 post-treatment. Annualized FIX use (IU/year) was reduced between 34% and 100%, with 3 participants who received no FIX infusions through 36 months post treatment. Conclusion: Etranacogene dezaparvovec were observed to be safe and effective in a subset of study participants living with HIV. These results support the use of etranacogene dezaparvovec, the first approved liver-directed AAV-based gene therapy product for the treatment of patients with severe or moderately severe hemophilia B in the US and Europe, for eligible patients with controlled comorbid HIV infection. Owing to the small number of patients with HIV being enrolled in trials, long-term collection of data and special attention in the real-world setting is recommended.

Functional and Morphological Characterization of RBCs Loaded with Factor IX Conjugated with an Anti-Glycophorin Ā Antibody

Red blood cells (RBCs) potentially can be used as drug carriers to improve pharmacokinetics (PK) for their unparalleled lifespan in circulation (120 days). Coupling factor IX (FIX) to the surface of RBCs is an innovative approach to boost FIX replacement therapy in hemophilia B. Here we studied effects of loading FIX to RBCs in vitro (morphology, rheological properties, procoagulant activity) and in vivo (PK of FIX-Ter119/RBC). To achieve RBC binding, purified human FIX was conjugated to the anti-mouse glycophorin A monoclonal antibody Ter119 and the FIX-Ter119 conjugates were separated and collected using SEC-HPLC. Then, mouse RBCs were incubated with either 10,000 or 50,000 molecules of FIX-Ter119 per one RBC, resulting in ~40% binding efficiency (~4,000 and ~20,000 molecules of FIX/RBC, respectively). Procoagulant activity of FIX/RBC was assessed in FIX-deficient human plasma using 3 assays: 1) activated partial thromboplastin time (aPTT), 2) rotational thromboelastometry (ROTEM), and 3) thrombin generation assay (TGA). FIX/RBC showed a dose-dependent activity in all the assays: i) aPTT was reduced (4,000 FIX/RBC: 57±1 s; 20,000 FIX/RBC: 48±1 s vs. control RBCs: 71±0.2 s, p&amp;lt;0.0001); ii) ROTEM: plasma clotting time was shortened and rate of clot strengthening was increased (45±6 and 69±3 vs 43±7 α, n.s. and p&amp;lt;0.001 vs. control, respectively) as was maximal clot firmness (maximum amplitude 19±3; 29±5 vs 22±3 mm, n.s. and p&amp;lt;0.05, respectively) between the RBCs bearing 4,000 and 20,000 FIX/RBC and control RBC, respectively (Figure 1A); iii) TGA: peak thrombin concentration was increased (134±18 and 193±17nM, for 4,000 and 20,000 FIX/RBC, respectively, p&amp;lt;0.05) vs. 74±27 nM for control RBCs (p&amp;lt;0.01). Altogether these results indicate that RBCs loaded with FIX-Ter119 possess specific FIXa activity, promote thrombin generation, and accelerate clotting in FIX-deficient plasma. Morphology and deformability of FIX/RBC were changed compared with control RBC. Scanning electron microscopy showed that the RBCs loaded with 4,000 and 20,000 FIX/RBC had increased echinocyte content (10±7% and 25±9%, respectively, p&amp;lt;0.01) while control RBCs contained only 3±1% echinocytes (p&amp;lt;0.001). After centrifugation at 1000g, the compressed RBCs had altered morphology, reflecting dissimilarity in cell deformability. The shape distribution for 4,000 and 20,000 FIX/RBC showed, respectively, 4±2% and 14±5% uncompressed biconcave RBCs, 8±3% and 12±8% intermediate mainly biconcave RBCs, 8±4% and 14±6% intermediate mainly polyhedral RBCs, and 63±20% and 70±24% fully compressed polyhedral RBCs (polyhedrocytes). In contrast, the unloaded centrifuged RBCs contained only 0.5±0.4% uncompressed biconcave RBCs, 1.5±0.6% intermediate mainly biconcave RBCs, 6±2% intermediate mainly polyhedral RBCs, and as much as 92±5% polyhedrocytes. Therefore, FIX/RBC demonstrated reduced deformability under mechanical compression caused by centrifugation. These results agree with ektacytometry data that showed a reduction in the deformability of RBC loaded with the FIX-Ter119 conjugates (maximum elongation index: 4,000 FIX/RBC: 0.40±0.09; 20,000 FIX/RBC: 0.34±0.04 vs 0.49±0.05 control RBCs, n.s. and p&amp;lt;0.01, respectively). Flow cytometry of FIX/RBC showed externalization of phosphatidylserine, but this increase was within normal levels (2.9±0.5% of phosphatidylserine-expressing RBCs). Agglutination assays showed that the FIX/RBC conjugates do not undergo agglutination at 4,000 FIX/RBC, but there was spontaneous agglutination of 20,000 FIX/RBCs, which limits the amount of FIX that can be loaded on the surface of RBC. Finally, we injected radiolabeled free FIX or FIX-Ter119 conjugates intravenously in mice to allow binding directly to circulating RBCs in vivo. The PK profile shows that more than 90% of the FIX-Ter119 conjugate was associated with RBCs and circulated stably bound to the RBCs for 24 hours, increasing the area under the PK curve 7.6 times vs. free FIX (Figure 1B). In conclusion: i) FIX can be loaded to the surface of RBCs, ii) FIX/RBC exert procoagulant activity, iii) FIX binding causes detectable, but apparently tolerable rheological changes in RBCs, and iv) FIX/RBC circulation time grossly exceeds that of free FIX. These preclinical studies support the potential utility of using FIX/RBC for treating bleeding conditions related to FIX deficiency.

Design of a Superior Factor VIIIa Mimetic By Coupling a Membrane Binding Domain to a Factor IXa Binding Antibody Fragment

Emicizumab is a bispecific antibody that augments Factor X (FX) activation by factor IXa (FIXa) in the absence of factor VIIIa (FVIIIa) by binding and approximating the substrate FX and protease FIXa. Clinical use of this FVIIIa mimetic significantly reduces bleeding episodes in Hemophilia A (HA) patients. Membrane dependent assembly of FVIIIa-FIXa-FX is an absolute requirement for the intrinsic tenase activity. In contrast, emicizumab lacks any membrane binding ability itself and exhibits significant FXa generation even in the absence of membranes. This major distinction likely allows FVIIIa to function at sub-nanomolar concentrations to greatly accelerate the activation of FX while only much lower enhancements of rate are achieved at several 100-fold higher concentrations of emicizumab. We sought to test whether the addition of a membrane binding feature in the monospecific FIXa binding fragment of emicizumab could alone approximate the cofactor activity obtained with the bispecific antibody. We first generated a single chain antibody fragment (scFv) of the FIXa binding arm of emicizumab by joining the variable heavy chain (V H) with the variable light chain (V L) to produce V H9V L. In line with previous observations that FIXa one arm antibodies of emicizumab that can only bind FIXa and impart a modest cofactor mimetic activity, V H9V L, facilitated FIXa-mediated FX activation at a much lower rate in comparison to bispecific emicizumab. The scFv, V H9V L, was used as a template to introduce membrane binding properties. The Factor V C2-domain, which binds membrane, was fused at the C-terminus of V H9V L via a repeating Gly 4Ser flexible linker of ~ 5.7 nm to allow the V H and V L domains of the scFv to potentially orient correctly at the membrane surface. The resulting construct V H9V LC2 showed a substantial amplification in cofactor mimetic activity as compared to V H9V L. In vitro kinetic analyses with purified proteins and synthetic phospholipid vesicles containing phosphatidylcholine (PC) and phosphatidylserine (PS) (PC:PS, 75:25 %) showed approximately 22-fold faster activation of FX by V H9V LC2 as compared to V H9V L. Remarkably, despite its inability to bind FX, cofactor mimetic activity of V H9V LC2 was about two-fold higher than that of emicizumab. Potent enhancement of FX activation by V H9V LC2 observed with purified proteins was also reflected in thrombin generation assays (TGA). V H9V LC2 added at 100 nM brought thrombin generation into the reference range in congenital FVIII-deficient HA plasma supplemented with 4 µM PC:PS and triggered with either low tissue factor (0.1 pM), or factor XIa (0.1 nM). The role of C2 domain-mediated increase in cofactor activity of V H9V LC2 was further assessed by using an antibody fragment (E 9scFv) that inhibits the binding of factor V to membranes. Increasing concentrations of E 9scFv caused a dose-dependent reduction in the rate of FXa formation catalyzed by the complex of V H9V LC2: FIXa (20nM:25nM). Inhibition saturated at ~ 85% at 100 nM E 9scFv, indicating a substantial contribution of membrane binding to the cofactor mimetic function of V H9V LC2. To evaluate whether V H9V LC2 can restore clotting in HA plasma with FVIII inhibitors, normal pooled plasma was supplemented with a FVIII neutralizing antibody to mimic FVIII inhibitor plasma. Addition of V H9V LC2 to this plasma restored clotting time to the levels shown by normal pooled plasma, suggesting that V H9V LC2 can bypass FVIII inhibitor activity. The engineered scFv with a factor V C2 domain fusion, V H9V LC2, demonstrates that mere addition of a membrane binding feature to the FIXa arm of the emicizumab surpasses the mimetic activity achieved by a bispecific antibody that exploits both bridging and allostery to be an effective cofactor. Such a construct also avoids the burden of productive assembly from a combination of three separate polypeptide chains, as in a functional bispecific antibody. Replicating the membrane binding feature into bispecific FVIIIa mimetic antibodies could further amplify function and more closely resemble FVIIIa in both activity and membrane dependent regulation. Our results provide surprising insights into how a single chain, monospecific, membrane-anchored FVIIIa mimetic enhances the catalytic activity of FIXa.

Adult Patients with Hemophilia B and with a History of Chronic HCV/HBV Infection Receiving Liver-Directed Gene Therapy Demonstrated Long-Term Bleeding Protection and Sustained FIX Activity: Efficacy and Safety Results from the HOPE-B Trial 3 Years after Administration of a Single Dose of Etranacogene Dezaparvovec

Introduction: Liver-targeted recombinant adeno-associated virus (rAAV) gene therapy for hemophilia B has recently become a real-world therapeutic option for an adult population burdened with prevalent co-morbid chronic hepatitis C virus (HCV) and hepatitis B virus (HBV). The pivotal phase 3 HOPE-B trial (NCT03489291) evaluated the efficacy and safety of etranacogene dezaparvovec (CSL222, formerly AMT-061), an AAV5 vector, containing a codon-optimized, highly active factor IX (FIX) Padua R338L transgene under the control of the liver-specific promoter LP-1. Here we evaluate the efficacy and safety of etranacogene dezaparvovec in the subset of HOPE-B participants with a history of chronic HCV and/or HBV. Methods: Adult male participants with hemophilia B (FIX ≤2%), were infused with a single dose of etranacogene dezaparvovec (2x10 13 gc/kg), following a ≥6-month lead-in period receiving their usual FIX prophylaxis. Relevant exclusion criteria included baseline liver chemistries &amp;gt; 2X the upper limit of normal (ULN); active HCV (HCV RNA detectable), HBV (HBV DNA detectable or HBV sAg reactive) or uncontrolled HIV infection; or advanced liver fibrosis (FibroScan™ score of ≥9 kPa). Regular liver ultrasound screening, serum chemistries, and alphafetoprotein (AFP) were collected along with FIX expression and bleeding data. During the first months post-treatment, alanine aminotransferase (ALT) increase to 2X the subject's baseline or &amp;gt;ULN was treated with a per-protocol tapering course of oral corticosteroids. Results: Among 54 HOPE-B trial participants, 31 (57.4%) had history of co-morbid chronic HCV, without active disease and with undetectable HCV RNA. Of these 31 subjects, 7 had a history of chronic HBV infection without active disease (HBV DNA undetectable; HBV sAg neg). Two subjects were HCV/HIV co-infected (HIV DNA neg; CD4+ T-cell count &amp;gt;200). Two subjects were HBV+ (HBV env AB reactive, HBV sAg non-reactive, HBV DNA undetectable)/HCV-/HIV-. The mean age in the HCV+ and/or HBV+ subgroup (HCBV n=33) was 50.0 years (range 31-75). All HCBV participants had central lab (CL) ALT &amp;lt;ULN (ULN=41 U/L) on the day of dosing except one subject who had a CL ALT of 48 U/L. The mean screening fibroscan (liver elastography) score for this subgroup was 5.2 kPa (range 2.8-8.0). In HCBV participants 16/33 (48.5%) had pre-existing AAV5 neutralizing antibodies (NAb), with titers ranging from 8.5-3232; all NAb+ HCBV patients had titer ≤678 except one participant who had a titer of 3212 and never demonstrated FIX expression; as a result his prophylactic FIX infusions were never discontinued and his efficacy outcomes reflect exogenous FIX therapy. One HCBV participant returned to continuous routine prophylaxis 30 months post treatment. In the HOPE-B trial 11/54 (20.4%) of participants had 12 adverse events of ALT elevation of 2X above baseline or &amp;gt;ULN within 12 weeks after etranacogene dezaparvovec treatment, which triggered immunosuppressive therapy with corticosteroids in 9/54 (16.7%) participants. In the HCBV subgroup, 5/33 (15.2%) participants had ALT elevations of which 4/33 (12.1%) participants received corticosteroids. As reported previously (Schmidt M, et al. Blood Advances. 2023), one HCBV subject maintained normal AFP levels however per-protocol screening ultrasound at one year after gene therapy this participant developed a hepatocellular carcinoma (HCC); molecular characterization demonstrated the HCC was not related to etranacogene dezaparvovec treatment. Factor IX expression was stably increased above baseline throughout 36 months after the single CSL222 infusion. History of chronic HCBV did not impact FIX expression (Table 1). After excluding the subject with the pre-existing AAV5 NAb titer 3212 whose continued prophylaxis use confounds analysis, the mean annualized bleeding rate (ABR) decreased after gene therapy compared to lead-in standard of care FIX prophylaxis. HCBV participants demonstrated an ABR rate ratio of 0.31 (95% CI 0.13, 0.72) indicating 69% reduction in all bleeding, sustained from months 7-36 following etranacogene dezaparvovec treatment. Conclusions: The majority of HOPE-B trial participants were adults with a history of chronic HCV and/or HBV infection without active viral disease or evident pre-existing liver fibrosis. Safety and efficacy are observed in the HCBV participants.

Prevalence of Rare Bleeding Disorders in the Central California Cohort: A Retrospective Single Institution Analysis

Abstract Rare bleeding disorders (RBD) constitute 3- 5% of all inherited clotting factor deficiencies and include inherited deficiencies of fibrinogen (FI), factors II, V, VII, X, XI and XIII, and combined factor V and VIII, and affect both sexes in an autosomal recessive manner. Rare platelet disorders can also present with bleeding diathesis which are recessively inherited. Significant clinical heterogeneity is present in these disorders with varying bleeding symptomatology causing diagnostic and therapeutic challenges. The objective of this study was to analyze the prevalence, characteristics, and treatment of rare bleeding disorders at the Valley Children's Hemophilia Treatment Center(HTC) in Central California.We conducted a retrospective analysis of all individuals who were referred for abnormal bleeding to our institution from 2018- 2023. We analyzed the clinical features, laboratory variables, and treatment of patients identified with RBD. Rare platelet disorders were included in this study. We excluded factor VIII, IX deficiencies and Von Willebrand disease (VWD) from this analysis. Results We identified a total of 157 patients (age range 18 months-46 years old) with RBD, 46% were of female gender (Table 1). Majority of the patients (n=92, 58%) were of Hispanic ethnicity. Major RBD in the cohort was Factor 7 (F7) deficiency (n= 96, 60.4%). F11 deficiency constituted 10.1%, followed by fibrinogen deficiency (6.3%), and F13 deficiency (5.7%). F2 and Plasminogen activator inhibitor-1 (PAI-1) deficiency was identified in one individual each. Glanzmann thrombasthenia was the most common platelet disorder noted in our population (n=7, 4.4%), followed by giant platelet disorder (n=6, 3.8%). MYH9- related disorder was identified in 5 (3.1%) individuals with macrothrombocytopenia and bleeding. Wiskott-Aldrich Syndrome was detected in 3 (1.9%) cases of RBD. Combined bleeding disorders (CBDs) were observed in 15 individuals (9.5%) (Table 2). These disorders were distinguished by genotyping, factor activity, and chromogenic activity assays. F7 and Type 1 VWD combined disorder was observed in 46.7% (n=7) of these individuals. Genetic testing was done in 38% (n=60) of the affected individuals. Genetic analysis was done through American Thrombosis &amp; Hemostasis Network (ATHN 10) in 19% (n=30). F7 gene mutation was the most commonly identified mutation and variants c.1238G&amp;gt;A (p.Arg413Gln), c.1172G&amp;gt;A (p.Arg353Gln), and c.1091G&amp;gt;A (p.Arg364Gln) were observed in those with F7 deficiency. All individuals with F7 deficiency with variants of uncertain significance were presumed to be positive. Treatment was specific to the factor deficiency. Most individuals received additional anti-fibrinolytic therapy during acute bleeding episodes. Recombinant F7 was used in platelet disorders for bleeding. Major bleeding events and death in the cohort was 1.2% (n= 2), and 2 individuals with F13 deficiency developed inhibitors to F13 concentrate. These individuals have been managed with recombinant F7 and anti-fibrinolytic therapy. Conclusion Ethnically diverse distribution of rare bleeding disorders was evident in our Central California cohort. Similar to previous reports, F7 deficiency was of the highest prevalence. A high prevalence of CBDs was also observed in this cohort. Genetic testing enabled diagnosis in some complex cases and needs to be used more widely to facilitate timely and accurate identification, and treatment of CBDs, and RBD in general. Further, these results help to identify novel mutations in different ethnicities, and provide additional information in understanding the clinical impact of new mutations.

Development of an Ex Vivo Precision Gene Engineered B Cell Medicine That Produces Active and Sustained Levels of FIX for the Treatment of Hemophilia B

Hemophilia B is an X-linked recessive bleeding disorder that affects approximately 1:20,000 males. It is caused by mutations in the F9 gene that encodes for the factor IX (FIX) protein, an essential enzyme in the coagulation cascade. The current recommended therapy for hemophilia B patients is prophylactic administration of exogenous FIX derived from recombinant protein. The short biological half-life of FIX requires frequent infusions to maintain therapeutic level. More recently, an adeno-associated virus (AAV) vector-based gene therapy, etranacogene dezaparvovec, has been approved for some adults as a potential new option. Despite these advances, there remains a significant unmet medical need in hemophilia B. Intravenous infusions of weekly (or more frequently, 3 times per week) factor replacements are an enormous burden to patients and their caregivers. Gene therapy, while a promising option for some, carries potential for significant risk. Importantly, the limitations associated with increasing the dose of FIX needed to treat pediatric patients as they age make immunogenic AAV-based gene therapy inappropriate for this patient population. Terminally differentiated human plasma cells derived from genetically engineered B cells (termed B Cell Medicines, BeCMs), potentially offer natural longevity (persisting for decades), capacity for high levels of protein secretion (thousands of Ig molecules/cell/sec), the ability to engraft without host preconditioning, and the ability to re-dose, making them an attractive platform for the sustained supply of biologics where continuous dosing is required to achieve therapeutic benefit. We have developed an ex vivo precision engineered BeCM platform with modularity and broad therapeutic utility. In this study, primary human B cells were isolated, activated, and engineered by CRISPR/Cas9 genome editing followed by AAV-mediated homology directed repair (HDR) insertion of human F9 gene into the C-C chemokine receptor type 5 (CCR5) safe harbor locus. The cells were then further expanded and differentiated towards the plasma cell lineage, resulting in FIX-producing BeCMs. We achieved approximately 40% targeted integration as measured by droplet digital PCR (ddPCR). Engineered BeCMs secreted up to 60 ng/1e6 cells/hour of FIX protein, approaching 40% of IgG secretion rate as measured by ELISA. BeCM-produced FIX was analyzed by LC-MS which demonstrated gamma carobxylation of FIX protein Gal-domain. Vitamin K-dependent activated partial thromboplastin time (aPTT), using the one stage clotting assay, was employed to verify biological activity of BeCM-produced FIX. Similarly, FIX-expressing BeCMs exhibited vitamin K-dependent activity in vitro in the chromogenic assay. FIX-expressing BeCMs were transferred into immunodeficient NOG-hIL6 mice, with FIX production demonstrated at least 20 weeks in vivo. The safety of FIX-expressing BeCMs has been characterized based on 28-day and 5-month in vivo studies in NOG-hIL6 mice. Neither abnormal clinical observations nor mortality were observed in those studies. Biodistribution of the FIX expressing BeCM product was assessed using a qPCR assay. The qPCR data confirms the expected biodistribution of FIX-expressing BeCMs, which engraft and persist in bone marrow tissue over time. In summary, we have developed an ex vivo precision gene engineered B cell medicine that produces active and sustained levels of FIX for the treatment of hemophilia B. The potential therapeutic application of this unique biologic delivery system could afford a novel treatment modality for hemophilia B.

Intraarticular Delivery of AAV5-Mir-125a-5p Regulates Key Molecular Mediators of Hemophilic Arthropathy

Background: Hemophilic arthropathy (HA) is a major comorbidity in patients with hemophilia characterized by chronic inflammation of the joints, stiffness and loss of function. The expression of microRNAs are known to be altered in various joint diseases such as rheumatoid arthritis and osteoarthritis which share clinical attributes with HA. One such microRNA is miR-125a-5p, known to be involved in regulating inflammatory mediators in the arthritic joints. The current study was designed to investigate the role of miR125a-5p in HA and examine the phenotypic effect of its targeted reconstitution in the joints. Methods: We utilized a chronic arthropathy model in hemophilia A mice to study the impact of miR125a-5p in disease progression. First, we performed a targeted screen of miR125a-5p and its target genes (STAT1 and TRAF6) using digital PCR (dPCR). Further, to validate if reconstitution of miR125a-5p aids in modulating the molecular mediators of HA, we performed the Adeno-associated virus vector (AAV) serotype 5 targeted delivery of miR125a (AAV5-miR125a) either alone (2.13x10 11vgs/joint) or in combination with capsid-modified AAV8-human Factor 8 (F8)(AAV8-F8) gene therapy at a low dose (1x10 11vgs/animal) intravenously in F8 tm1kaz/Jmice. Briefly, the animals were administered with vectors (alone or in combination), and seven days post vector administration, the animals were subjected to multiple bleeding episodes in the right knee (Day 0, 14, and 30) to mimic chronic hemarthrosis. On day 45, blood samples were collected from experimental animals for FVIII specific clotting assay, and joint tissues were isolated to perform further molecular and histochemical analysis. Results: Our dPCR analysis revealed a significant reduction (2-fold) of miR125a-5p (3518 copies/µl vs 7242 copies/µl, p≤0.0001) in injured joints compared to control joints. Absolute quantification of target genes, namely STAT1 and TRAF6 showed significantly higher expression in injured joints (7.6 to 10.6 fold, respectively) when compared to control joints. Further immunohistochemical examination of joint sections from the experimental mice confirmed the elevated expression of these immunological mediators (STAT1, TRAF6). Upon administration of AAV vectors containing miR125a and/or F8, we observed a significantly increased expression of miR125a-5p (~12 fold) in only miR125a vector-administered animals while the combination vector treated group had, ~44-fold higher levels of miR125a-5p. The coagulant assay revealed an increased FVIII activity (~17%) in only F8 vector-treated animals and approximately 20% FVIII levels in mice that received both miR125a and F8 vectors at low doses. Surprisingly, the animals that received only F8 vectors also showed significantly upregulated miR125a-5p expression (~20 fold) signifying the role of miR125a-5p in HA pathology. In line with the above findings, immunohistochemical analysis of joint tissues revealed decreased expression of immunological markers STAT1, TRAF6 (direct targets of miR125a-5p), and the chondro-degenerative matrix metalloproteinases 3, 9, 13 in vector-treated groups when compared to injured joints with no treatment. Hematoxylin and Eosin (H&amp;E) staining of joint tissues from experimental animals was performed which revealed that animals that received both miR125a and F8 vectors showed decreased synovial hyperplasia, villi formation, cartilage erosion, and reduced hemosiderin deposition signifying moderate phenotype rescue. Conclusions: Our data confirms that miR125a-5p is a major molecular target that regulates inflammatory response in chronic HA. Targeted delivery of miR125a in tandem with F8 gene augmentation had an impact on several molecular mediators like STAT1, TRAF6, MMP3,9, and 13. The reconstitution of miR125a and a higher dose of F8 vectors might be beneficial to reverse chronic HA.

B Cell Therapeutics

Plasma cells are specialized immune cells that can survive in the bone marrow for decades and continually secrete large amounts of antibodies, thus providing long-term, often lifelong protection from repeated exposures to a pathogen. The long-term survival and the capability to secrete high amounts of protein make plasma cells a potential candidate for stable delivery of therapeutic proteins and antibodies. However, engineering plasma cells or B cells has been challenging due to low lentiviral transduction efficiency, incompatibility with plasmid transfection and loss of episomal DNA expression over time. We have previously shown that human plasma cells can be engineered to secrete antibodies and proteins in in vitro culture systems via gene editing. In the current study, we have generated engineered murine plasma cells that can secrete the clotting factor IX (FIX). We hypothesize that the FIX-secreting plasma cells will engraft long-term in FIX-deficient immunocompetent mice and secrete therapeutic levels of FIX leading to protection from Hemophilia B. The standard of care for Hemophilia B is repeated intravenous infusion of recombinant FIX or AAV-based gene therapy. However, 30-60% humans have pre-existing immunity to AAV-based gene therapy and gene therapy can induce an immune response in people lacking pre-existing antibodies. Moreover, gene therapy is unsuitable for pediatric patients due to their rapid growth and proportional loss of AAV. Plasma cell-based therapy is lowly immunogenic and can be used for redosing in pediatric patients that require more product with age. Here, we will describe proof-of-concept studies showing that engineered murine plasma cells can engraft into immunocompetent mice without the need for conditioning and produce stable levels of protein for &amp;gt;10 weeks. We developed a three-step in vitro co-culture system that can be used to engineer and differentiate naïve B cells into plasma cells. These in vitro generated murine plasma cells had a comparable gene expression profile and phenotype to natural plasma cells and can engraft stably, in the absence of conditioning, into immunocompetent mice whereupon they secreted antibodies (Figure 1). Moreover, we show that plasma cells can be re-dosed to increase antibody levels without triggering a secondary immune response (Figure 1). For delivery of therapeutic proteins, we have developed adeno-associated virus-based homology directed repair reagents to edit murine B cells at several loci, including beta-2 microglobulin, Rosa-26, and the antibody heavy chain. By co-delivery of cis-linked fluorescent markers, we were able to sort and expand only edited cells, enabling enrichment of cells expressing a therapeutic protein. In proof-of-concept studies, we have used this approach to generate a human FIX-secreting plasma cell product with close to 90% edited cells at the end of the B cell culture. The enriched plasma cells generated 0.28 pg FIX/cell/day compared to 0.19 pg FIX/cell/day generated by the bulk edited cells (figure 2). We estimate that engraftment of 1 million edited plasma cells is sufficient to generate therapeutic levels of FIX upon (figure 2). We have developed reagents for a novel cell-based therapeutic tool with protein secretion capabilities and far-reaching applications. Out studies will provide insights into the feasibility and efficacy of a B cell based therapeutic product.

Health Care Resource Use, Comorbidities, and Costs of Hemophilia B Patients in France: A Nationwide Claims Database Analysis

Background and objectives Hemophilia B is an inherited bleeding disorder characterized by a deficiency in blood clotting factor IX (FIX). Its severity varies based on the degree of FIX deficiency, with the most severe cases experiencing frequent spontaneous hemorrhages (FIX levels &amp;lt; 1 IU/dL). Treatment options include on-demand administration following a hemorrhage or prophylaxis to prevent bleeding. A complication is the production of inhibitory antibodies against the coagulation factors in some patients, leading to more aggressive and expensive treatments. The aim of this study was to describe Hemophilia B patients according to severity in France in 2021, including sociodemographic characteristics and comorbidities, current treatments, healthcare resource use and related costs. Methods This study used the French health-insurance claims database (SNDS) containing pseudonymized individual data for over 66 million people. Hemophilia B patients are fully covered in France and might be identified by the ICD-10 code D67. Patients alive on January 1st, 2021, were selected after exclusion of those presenting with Willebrand disease and other rare bleeding disorders. Comorbidities were identified through validated algorithms. An age and gender matched control group without Hemophilia B was randomly selected in the general population: for each HB patient a subject of the same age,gender and region of residence was randomly selected among the overall population of French citizens (excluding HB patients). Sub-group analyses were performed according to the treatment pattern (on demand / in prophylaxis) and the presence of inhibitors (defined with the treatment: high dose of factor IX or bypassing agents). Direct costs were estimated in a societal perspective. Results 1,311 patients with Hemophilia B were identified. Mean age was 36 years and 83.5% were males. Compared to controls, hemophilia patients had significantly (p&amp;lt;0.05) more frequently an HIV infection, hepatitis B or C, and a chronic cardiopathy (Figure 1). There were no significant differences for coronary artery diseases, chronic heart failure, arrhythmia, and hepatic diseases. Respectively 996 (76.0%) and 303 (23.1%) patients were treated on demand and in prophylaxis both without inhibitors. Less than 10 patients were treated either on demand with inhibitors or in prophylaxis with inhibitors. Compared to controls, patients with hemophilia B had more frequent consultations with general practitioners and hospital specialists, visits to emergency unit, with nurses and physiotherapists (Table 1). They also were more frequently treated with analgesics and corticosteroids but less frequently with non-steroid anti-inflammatory drugs. The proportion of hemophilia B patients hospitalized was higher than controls, overall and also for bleeding and for orthopedic surgery. The mean annual direct medical costs (drugs, consultations, hospitalizations, ...) varied strongly according to treatment modalities: €6,506 for patients treated on demand without inhibitors (versus €1,795 for their matched controls)€162,635 for patients treated in prophylaxis without inhibitors (versus €1,071 for their matched controls). The majority of the costs was related to antihemophilic drugs: 33% and 92% respectively for these 2 treatment groups. Conclusion: These results highlight the burden of hemophilia B in terms of comorbidities, healthcare consumptions and cost. The cost of Hemophilia B varied greatly with disease severity and was mostly due to the antihemophilic drugs

Hemophilic Pseudotumor of Paranasal Sinuses in a Child with Severe Hemophilia a Receiving Emicizumab: A Case Report

Emicizumab, a bispecific humanized monoclonal antibody, bridges activated factor IX (FIX) and FX to restore the function of missing activated FVIII in individuals with hemophilia A (PwHA). Prophylaxis with subcutaneous emicizumab promotes adequate hemostasis in PwHA. Emicizumab prophylaxis in children with hemophilia A has been approved in the United States for use in PwHA ages newborn and older, with or without FVIII inhibitors. We report a 2-year-old boy with severe congenital hemophilia A who initially received prophylaxis with standard half-life factor VIII but later switched to subcutaneous emicizumab at 6 mg/kg every four weeks due to difficult IV access and parental preference. Shortly after starting emicizumab, the patient presented to the hospital with severe episodic epistaxis from the left nostril, requiring ICU admission and ENT consultation. Despite treatment, the condition did not improve, prompting the need for imaging studies. Subsequently, the patient developed ipsilateral eye proptosis and a mass protruding from the left nostril. CT and MRI imaging of the orbit revealed an expansible soft tissue mass measuring 2 x 2.5 x 4 cm occupying the right sphenoid sinus, extending to the nasal cavity. The mass had caused erosion of the clivus and the anterior cranial fossa floor, extending to the middle cranial fossa (Figures 1 &amp; 2). He underwent endoscopic nasal debulking of the left nostril mass, and the pathological examination revealed a cystic mass with a thick capsule and intra-cystic blood clots, consistent with the characteristics of a hemophilic pseudotumor (HP). The fibrous stroma contained hemosiderin-laden macrophages with no evidence of malignancy. Emicizumab was discontinued before the operation, and the patient received several doses of recombinant FVIII to maintain hemostasis. Despite the debulking procedure, the patient continued to experience episodic epistaxis and joint bleeding. An inhibitor assay was performed at that time and showed high levels, leading to a switch to on-demand FVIII treatment for hemophilia A with an inhibitor. Managing the bleeding episodes with bypassing agents proved challenging, and the family expressed dissatisfaction. A decision was made to resume emicizumab treatment, and the patient eventually stabilized, experiencing no bleeding for nearly six months. Additionally, he regularly follows up with ENT specialty, with no further intervention or progression of the tumor. Notably, he did not receive any bypassing agents concomitantly with emicizumab. HP is characterized by encapsulated blood clots accumulating in extravascular tissues, especially the musculoskeletal system, in patients with bleeding tendencies, particularly hemophiliacs. It is a benign, expansible, soft tissue-like mass that exerts pressure on surrounding structures, mimicking a locally invasive malignancy. HP is a hematoma that grows and causes bone erosion through repeated bleeding episodes. A literature review revealed that HP is a rare hemorrhagic complication that develops in 1-2% of patients with severe hemophilia (Magallón et al. Am J Hematol. 1994). Its occurrence in patients receiving emicizumab prophylaxis is extremely rare. The first reported case involved a Japanese child with hemophilia who presented with a pseudotumor occupying the left maxillary sinus after repeated episodes of epistaxis. The mass caused a downward deviation of the ipsilateral eye and bulged into the buccal cavity. The patient received monthly prophylaxis with emicizumab at 6 mg/kg (Kawahara et al. Int J Hematol. 2022), but unlike our patient, he received bypassing agents concomitantly. Our reported case is unique because HP developed independently of bypassing agent therapies, as the patient did not receive any bypassing agents before the tumor's development. The likely explanation is related to repeated bleeding insults to the same anatomical location, leading to the cumulative development of hematoma and HPs. Another possibility could be attributed to the known adverse thrombotic effects of emicizumab treatment. Physicians treating hemophilia should remain vigilant for abnormal clinical signs, such as new masses in patients receiving emicizumab, which could indicate HP.

Humanization and functional characterization of enhanced coagulation factor IX variants identified through ancestral sequence reconstruction

BackgroundLaboratory resurrection of ancient coagulation factor (F) IX variants generated through ancestral sequence reconstruction led to the discovery of a FIX variant, designated An96, which possesses enhanced specific activity independent of and additive to that provided by human p.Arg384Lys, referred to as FIX-Padua. ObjectivesThe goal of the current study was to identify the amino acid substitution(s) responsible for the enhanced activity of An96 and create a humanized An96 FIX transgene for gene therapy application. MethodsReductionist screening approaches, including domain swapping and scanning residue substitution, were used and guided by one-stage FIX activity assays. In vitro characterization of top candidates included recombinant high-purity preparation, specific activity determination, and enzyme kinetic analysis. Final candidates were packaged into adeno-associated viral (AAV) vectors and delivered to hemophilia B mice. ResultsFive of 42 total amino acid substitutions in An96 appear sufficient to retain the enhanced activity of An96 in an otherwise human FIX variant. Additional substitution of the Padua variant further increased the specific activity 5-fold. This candidate, designated ET9, demonstrated 51-fold greater specific activity than hFIX. AAV2/8-ET9 treated hemophilia B mice produced plasma FIX activities equivalent to those observed previously for AAV2/8-An96-Padua, which were 10-fold higher than AAV2/8-hFIX-Padua. ConclusionStarting from computationally inferred ancient FIX sequences, novel amino acid substitutions conferring activity enhancement were identified and translated into an AAV-FIX gene therapy cassette demonstrating high potency. This ancestral sequence reconstruction discovery and sequence mapping refinement approach represents a promising platform for broader protein drug and gene therapy candidate optimization.