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Fidanacogene elaparvovec, an adeno-associated virus (AAV) gene-therapy vector for hemophilia B containing a high-activity human factor IX variant (FIX-R338L/FIX-Padua), was associated with sustained factor IX activity in a phase 1-2a study. We conducted a phase 3 open-label study of fidanacogene elaparvovec at a dose of 5×10 vector genome copies per kilogram of body weight. Men 18 to 65 years of age with hemophilia B and a factor IX level of 2% or less were eligible for screening if they had received at least 6 months of therapy with prophylactic factor IX concentrate. The primary end point, tested for noninferiority, was the annualized bleeding rate (treated and untreated bleeding episodes) from week 12 to month 15 after treatment with fidanacogene elaparvovec as compared with the prophylaxis lead-in period. Superiority, additional efficacy end points, and safety were also assessed. Of 316 men who underwent screening for the lead-in study, 204 (64.6%) were not eligible; 188 (59.5%) of those were ineligible owing to the presence of anti-AAV neutralizing antibodies. Of the 45 participants who received fidanacogene elaparvovec, 44 completed at least 15 months of follow-up. The annualized rate of bleeding for all bleeding episodes decreased by 71%, from 4.42 (95% confidence interval [CI], 1.80 to 7.05) at baseline to 1.28 (95% CI, 0.57 to 1.98) after gene therapy, a treatment difference of -3.15 episodes (95% CI, -5.46 to -0.83; P = 0.008). This result shows the noninferiority and superiority of fidanacogene elaparvovec to prophylaxis. At 15 months, the mean factor IX activity was 26.9% (median, 22.9%; range, 1.9 to 119.0) by one-stage SynthASil assay. A total of 28 participants (62%) received glucocorticoids for increased aminotransferase levels or decreased factor IX levels (or both) starting between 11 and 123 days. No infusion-related serious adverse events, thrombotic events, development of factor IX inhibitors, or malignant conditions were observed. Fidanacogene elaparvovec was superior to prophylaxis for the treatment of participants with hemophilia B, leading to reduced bleeding and stable factor IX expression. (Funded by Pfizer; BENEGENE-2 ClinicalTrials.gov number, NCT03861273.).

Emicizumab is a humanized bispecific antibody that mimics the cofactor function of factor VIII. In a dose-escalation study in Japanese persons with hemophilia A, including those with factor VIII inhibitors, emicizumab markedly reduced the number of bleeding episodes. Hemophilia A is a serious bleeding disorder caused by a deficiency of clotting factor VIII. Approximately 50% of patients have severe hemophilia A, 1 defined as less than 1% residual factor VIII activity (<1 IU per deciliter). 2 Such patients have severe bleeding from early childhood, and without appropriate treatment, recurrent bleeding into joints can lead to irreversible hemoarthropathy. 3 , 4 Standard treatment for hemophilia A includes regular prophylaxis and episodic treatment with recombinant or plasma-derived factor VIII. The goals of prophylaxis with factor VIII are to increase factor VIII activity to at least a moderate level (1 to 5 IU per deciliter) . . .

Nine of 10 patients with hemophilia B who received a liver-directed adeno-associated viral vector containing a hyperactive variant of factor IX maintained factor IX activity for up to 42 months. Thrombosis developed in 1 patient.

Adeno-associated virus (AAV)-mediated gene therapy has emerged as a promising treatment for hemophilia B. Data on safety and durability from 13 years of follow-up in a cohort of patients who had been successfully treated with scAAV2/8-LP1-hFIXco gene therapy are now available. Ten men with severe hemophilia B received a single intravenous infusion of the scAAV2/8-LP1-hFIXco vector in one of three dose groups (low-dose: 2×10 vector genomes [vg] per kilogram of body weight [in two participants]; intermediate-dose: 6×10 vg per kilogram [in two]; or high-dose: 2×10 vg per kilogram [in six]). Efficacy outcomes included factor IX activity, the annualized bleeding rate, and factor IX concentrate use. Safety assessments included clinical events, liver function, and imaging. Participants were followed for a median of 13.0 years (range, 11.1 to 13.8). Factor IX activity remained stable across the dose cohorts, with mean factor IX levels of 1.7 IU per deciliter in the low-dose group, 2.3 IU per deciliter in the intermediate-dose group, and 4.8 IU per deciliter in the high-dose group. Seven of the 10 participants did not receive prophylaxis. The median annualized bleeding rate decreased from 14.0 episodes (interquartile range, 12.0 to 21.5) to 1.5 episodes (interquartile range, 0.7 to 2.2), which represented a reduction by a factor of 9.7. Use of factor IX concentrate decreased by a factor of 12.4 (interquartile range, 2.2 to 27.1). A total of 15 vector-related adverse events occurred, primarily transient elevations in aminotransferase levels. Factor IX inhibitor, thrombosis, or chronic liver injury did not develop in any participant. Two cancers were identified but were deemed by the investigators, together with an expert multidisciplinary team, as being unrelated to the vector. A liver biopsy that was conducted in 1 participant 10 years after the infusion revealed transcriptionally active transgene expression in hepatocytes without fibrosis or dysplasia. Levels of neutralizing antibodies to AAV8 remained high throughout follow-up, thus indicating potential barriers to readministration of the vector. A single administration of scAAV2/8-LP1-hFIXco gene therapy resulted in durable factor IX expression, sustained clinical benefit, and no late-onset safety concerns over a period of 13 years. These data support the long-term efficacy and safety of AAV gene therapy for severe hemophilia B. (Funded by the U.K. Medical Research Council and others; ClinicalTrials.gov number, NCT00979238; EudraCT number, 2005-005711-17.).

Gene correction in a blood disorder Direct editing of disease-causing mutations has obvious attractions for the treatment of genetic disorders if the many practical obstacles to the technique can be overcome. One promising line of research centres on the development of zinc finger nucleases (ZFNs) produced by fusing an engineered zinc finger DNA-binding domain to an endonuclease. These artificial enzymes induce efficient gene correction in cultured cells. Li et al . now report that zinc finger nucleases induce double-strand breaks in specifically selected locations on the genome and stimulate genome editing at a clinically meaningful level in vivo . In a proof-of-principle experiment, ZFNs delivered to the liver in a mouse model of haemophilia B achieved a level of gene replacement that was sufficient to correct the clotting defect, and the effect persisted following liver regeneration. Editing of the human genome to correct disease-causing mutations is a promising approach for the treatment of genetic disorders. Genome editing improves on simple gene-replacement strategies by effecting in situ correction of a mutant gene, thus restoring normal gene function under the control of endogenous regulatory elements and reducing risks associated with random insertion into the genome. Gene-specific targeting has historically been limited to mouse embryonic stem cells. The development of zinc finger nucleases (ZFNs) has permitted efficient genome editing in transformed and primary cells that were previously thought to be intractable to such genetic manipulation 1 . In vitro , ZFNs have been shown to promote efficient genome editing via homology-directed repair by inducing a site-specific double-strand break (DSB) at a target locus 2 , 3 , 4 , but it is unclear whether ZFNs can induce DSBs and stimulate genome editing at a clinically meaningful level in vivo . Here we show that ZFNs are able to induce DSBs efficiently when delivered directly to mouse liver and that, when co-delivered with an appropriately designed gene-targeting vector, they can stimulate gene replacement through both homology-directed and homology-independent targeted gene insertion at the ZFN-specified locus. The level of gene targeting achieved was sufficient to correct the prolonged clotting times in a mouse model of haemophilia B, and remained persistent after induced liver regeneration. Thus, ZFN-driven gene correction can be achieved in vivo , raising the possibility of genome editing as a viable strategy for the treatment of genetic disease.

Human endothelial cells (ECs) synthesize, store, and secrete von Willebrand factor multimeric strings and coagulation factor (F) VIII. It is not currently known if ECs produce other coagulation factors for active participation in coagulation. We found that 3 different types of human ECs in primary culture produce clotting factors necessary for FX activation via the intrinsic (FVIII-FIX) and extrinsic (tissue factor [TF]-FVII) coagulation pathways, as well as prothrombin. Human dermal fibroblasts were used as comparator cells. TF, FVII, FIX, FX, and prothrombin were detected in ECs, and TF, FVII, FIX, and FX were detected in fibroblasts. In addition, FVII, FIX, FX, and prothrombin were detected by fluorescent microscopy in EC cytoplasm (associated with endoplasmic reticulum and Golgi proteins). FX activation occurred on human umbilical vein EC surfaces without the addition of external coagulation proteins, proteolytic enzymes, or phospholipids. Tumour necrosis factor, which suppresses the generation of activated protein C and increases TF, augmented FX activation. Fibroblasts also produced TF, but (in contrast to ECs) were incapable of activating FX without the exogenous addition of FX and had a marked increase in FX activation following the addition of both FX and FVII. We conclude that human ECs produce their own coagulation factors that can activate cell surface FX without the addition of exogenous proteins or phospholipids.

Preanalytical quality control of blood samples is critical for tests of coagulation function and coagulation factor activity. Preanalytical storage time and temperature are the main variables. We investigated the effects of preanalytical frozen storage time and temperature on activated partial thromboplastin time (APTT), fibrinogen (Fbg), prothrombin time (PT)/international normalized ratio (INR), thrombin time (TT), factor VIII activity (FVIII:C), and factor IX activity (FIX:C) in frozen plasma. Samples (n = 144) were randomly and equally divided into four groups (storage at −80 °C or −20 °C) and analysed by CS5100 or CA7000 coagulation analysers. Baseline values and results after storage for 15 days, 1 month, 3 months, 6 months, and 1 year were measured after thawing. Mean percent changes and scatter plots were used to determine clinically relevant differences. The stabilities of coagulation tests and coagulation factor activities measured by the CS5100 system were consistent with those measured by the CA7000 system. At −80 °C, assessment samples of PT/INR, Fbg, and TT can be safely stored for 1 year, APTT for 6 months, and FVIII:C and FIX:C for 1 month. At −20 °C, samples of Fbg and TT can be stored for 1 year, PT/INR and FIX:C for 1 month, and APTT and FVIII:C for 15 days.

A conventional photolithography technique was used to fabricate three types of Archimedean-spiral interdigitated electrodes (AIDEs) containing concentric interlocking electrodes with different electrode and gap sizes, i.e., 150 μm (D1), 100 μm (D2), and 50 μm (D3). The precision of the fabrication was validated by surface topography using scanning electron microscopy, high power microscopy, 3D-nano profilometry, and atomic force microscopy. These AIDEs were fabricated with a tolerance of ± 6 nm in dimensions. The insignificant current variation at the pico-ampere range for all bare AIDEs further proved the reproducibility of the device. The large gap sized AIDE (D1) is insensitive to acidic medium, whereas D2 and D3 are insensitive to alkali medium. D2 was the best with regard to its electrical characterization. Furthermore, uniformly synthesized molecularly imprinted polymer (MIP) nanoparticles prepared with human blood clotting factor IX and its aptamer were in the size range 140 to 160 nm, attached on the sensing surface and characterized. The average thickness of deposited MIP film was 1.7 μm. EDX data shows the prominent peaks for silicon and aluminum substrates as 61.79 and 22.52%, respectively. The MIP nanoparticles-deposited sensor surface was characterized by applying it in electrolyte solutions, and smooth curves with the current flow were observed at pH lower than 8 and discriminated against alkali media. This study provides a new MIP amalgamated AIDE with nano-gapped fingers enabling analysis of other biomaterials due to its operation in an ideal buffer range. Graphical abstract

In a phase I study, administration of an AAV2-FIX vector into the skeletal muscle of eight hemophilia B subjects proved safe and achieved local gene transfer and FIX expression for at least 10 months after vector injection, the last time point assessed by muscle biopsy. In hemophilia B dogs we have demonstrated FIX in both muscle biopsies and circulation >4 years following AAV2-FIX injection. Because circulating FIX levels remained less than 1% of normal in human subjects from the study, the duration of AAV2-mediated transgene expression in humans is unknown. We sought to determine if FIX gene transfer and expression persisted locally at injection sites. Muscle biopsies were obtained from one subject 3.7 years following treatment and revealed transgene FIX DNA and protein by quantitative PCR, DNA fluorescence in situ hybridization, and immunohistochemistry for FIX. These results demonstrate, for the first time, multiyear FIX expression by AAV2 vector in humans and suggest that improved muscle delivery provides effective treatment for protein deficiencies or muscle-specific diseases.

Obesity is associated with a hypercoagulable state and increased risk for thrombotic cardiovascular events. Establish the onset and reversibility of the hypercoagulable state during the development and regression of nutritionally-induced obesity in mice, and its relation to transcriptional changes and clearance rates of coagulation factors as well as its relation to changes in metabolic and inflammatory parameters. Male C57BL/6J mice were fed a low fat (10% kcal as fat; LFD) or high fat diet (45% kcal as fat; HFD) for 2, 4, 8 or 16 weeks. To study the effects of weight loss, mice were fed the HFD for 16 weeks and switched to the LFD for 1, 2 or 4 weeks. For each time point analyses of plasma and hepatic mRNA levels of coagulation factors were performed after overnight fasting, as well as measurements of circulating metabolic and inflammatory parameters. Furthermore, in vivo clearance rates of human factor (F) VII, FVIII and FIX proteins were determined after 2 weeks of HFD-feeding. HFD feeding gradually increased the body and liver weight, which was accompanied by a significant increase in plasma glucose levels from 8 weeks onwards, while insulin levels were affected after 16 weeks. Besides a transient rise in cytokine levels at 2 weeks after starting the HFD, no significant effect on inflammation markers was present. Increased plasma levels of fibrinogen, FII, FVII, FVIII, FIX, FXI and FXII were observed in mice on a HFD for 2 weeks, which in general persisted throughout the 16 weeks of HFD-feeding. Interestingly, with the exception of FXI the effects on plasma coagulation levels were not paralleled by changes in relative transcript levels in the liver, nor by decreased clearance rates. Switching from HFD to LFD reversed the HFD-induced procoagulant shift in plasma, again not coinciding with transcriptional modulation. Changes in dietary fat content rapidly alter the mouse plasma coagulation profile, thereby preceding plasma metabolic changes, which cannot be explained by changes in relative expression of coagulation factors or decreased clearance rates.