Gene Therapy with Etranacogene Dezaparvovec for Hemophilia B.

BACKGROUND: Moderate-to-severe hemophilia B is treated with lifelong, continuous coagulation factor IX replacement to prevent bleeding. Gene therapy for hemophilia B aims to establish sustained factor IX activity, thereby protecting against bleeding without burdensome factor IX replacement. METHODS: In this open-label, phase 3 study, after a lead-in period (≥6 months) of factor IX prophylaxis, we administered one infusion of adeno-associated virus 5 (AAV5) vector expressing the Padua factor IX variant (etranacogene dezaparvovec; 2×1013 genome copies per kilogram of body weight) to 54 men with hemophilia B (factor IX activity ≤2% of the normal value) regardless of preexisting AAV5 neutralizing antibodies. The primary end point was the annualized bleeding rate, evaluated in a noninferiority analysis comparing the rate during months 7 through 18 after etranacogene dezaparvovec treatment with the rate during the lead-in period. Noninferiority of etranacogene dezaparvovec was defined as an upper limit of the two-sided 95% Wald confidence interval of the annualized bleeding rate ratio that was less than the noninferiority margin of 1.8. Superiority, additional efficacy measures, and safety were also assessed. RESULTS: The annualized bleeding rate decreased from 4.19 (95% confidence interval [CI], 3.22 to 5.45) during the lead-in period to 1.51 (95% CI, 0.81 to 2.82) during months 7 through 18 after treatment, for a rate ratio of 0.36 (95% Wald CI, 0.20 to 0.64; P<0.001), demonstrating noninferiority and superiority of etranacogene dezaparvovec as compared with factor IX prophylaxis. Factor IX activity had increased from baseline by a least-squares mean of 36.2 percentage points (95% CI, 31.4 to 41.0) at 6 months and 34.3 percentage points (95% CI, 29.5 to 39.1) at 18 months after treatment, and usage of factor IX concentrate decreased by a mean of 248,825 IU per year per participant in the post-treatment period (P<0.001 for all three comparisons). Benefits and safety were observed in participants with predose AAV5 neutralizing antibody titers of less than 700. No treatment-related serious adverse events occurred. CONCLUSIONS: Etranacogene dezaparvovec gene therapy was superior to prophylactic factor IX with respect to the annualized bleeding rate, and it had a favorable safety profile. (Funded by uniQure and CSL Behring; HOPE-B ClinicalTrials.gov number, NCT03569891.).

Valoctocogene Roxaparvovec Gene Therapy for Hemophilia A.

BACKGROUND: Valoctocogene roxaparvovec (AAV5-hFVIII-SQ) is an adeno-associated virus 5 (AAV5)-based gene-therapy vector containing a coagulation factor VIII complementary DNA driven by a liver-selective promoter. The efficacy and safety of the therapy were previously evaluated in men with severe hemophilia A in a phase 1-2 dose-escalation study. METHODS: We conducted an open-label, single-group, multicenter, phase 3 study to evaluate the efficacy and safety of valoctocogene roxaparvovec in men with severe hemophilia A, defined as a factor VIII level of 1 IU per deciliter or lower. Participants who were at least 18 years of age and did not have preexisting anti-AAV5 antibodies or a history of development of factor VIII inhibitors and who had been receiving prophylaxis with factor VIII concentrate received a single infusion of 6×1013 vector genomes of valoctocogene roxaparvovec per kilogram of body weight. The primary end point was the change from baseline in factor VIII activity (measured with a chromogenic substrate assay) during weeks 49 through 52 after infusion. Secondary end points included the change in annualized factor VIII concentrate use and bleeding rates. Safety was assessed as adverse events and laboratory test results. RESULTS: Overall, 134 participants received an infusion and completed more than 51 weeks of follow-up. Among the 132 human immunodeficiency virus-negative participants, the mean factor VIII activity level at weeks 49 through 52 had increased by 41.9 IU per deciliter (95% confidence interval [CI], 34.1 to 49.7; P<0.001; median change, 22.9 IU per deciliter; interquartile range, 10.9 to 61.3). Among the 112 participants enrolled from a prospective noninterventional study, the mean annualized rates of factor VIII concentrate use and treated bleeding after week 4 had decreased after infusion by 98.6% and 83.8%, respectively (P<0.001 for both comparisons). All the participants had at least one adverse event; 22 of 134 (16.4%) reported serious adverse events. Elevations in alanine aminotransferase levels occurred in 115 of 134 participants (85.8%) and were managed with immune suppressants. The other most common adverse events were headache (38.1%), nausea (37.3%), and elevations in aspartate aminotransferase levels (35.1%). No development of factor VIII inhibitors or thrombosis occurred in any of the participants. CONCLUSIONS: In patients with severe hemophilia A, valoctocogene roxaparvovec treatment provided endogenous factor VIII production and significantly reduced bleeding and factor VIII concentrate use relative to factor VIII prophylaxis. (Funded by BioMarin Pharmaceutical; GENEr8-1 ClinicalTrials.gov number, NCT03370913.).

Ribosome dysfunction underlies SLFN14-related thrombocytopenia.

Pathogenic missense variants in SLFN14, which encode an RNA endoribonuclease protein that regulates ribosomal RNA (rRNA) degradation, are known to cause inherited thrombocytopenia (TP) with impaired platelet aggregation and adenosine triphosphate secretion. Despite mild laboratory defects, the patients displayed an obvious bleeding phenotype. However, the function of SLFN14 in megakaryocyte (MK) and platelet biology remains unknown. This study aimed to model the disease in an immortalized MK cell line (imMKCL) and to characterize the platelet transcriptome in patients with the SLFN14 K219N variant. MK derived from heterozygous and homozygous SLFN14 K219N imMKCL and stem cells of blood from patients mainly presented with a defect in proplatelet formation and mitochondrial organization. SLFN14-defective platelets and mature MK showed signs of rRNA degradation; however, this was absent in undifferentiated imMKCL cells and granulocytes. Total platelet RNA was sequenced in 2 patients and 19 healthy controls. Differential gene expression analysis yielded 2999 and 2888 significantly (|log2 fold change| >1, false discovery rate <0.05) up- and downregulated genes, respectively. Remarkably, these downregulated genes were not enriched in any biological pathway, whereas upregulated genes were enriched in pathways involved in (mitochondrial) translation and transcription, with a significant upregulation of 134 ribosomal protein genes (RPGs). The upregulation of mitochondrial RPGs through increased mammalian target of rapamycin complex 1 (mTORC1) signaling in SLFN14 K219N MK seems to be a compensatory response to rRNA degradation. mTORC1 inhibition with rapamycin resulted in further enhanced rRNA degradation in SLFN14 K219N MK. Taken together, our study indicates dysregulation of mTORC1 coordinated ribosomal biogenesis is the disease mechanism for SLFN14-related TP.

Emicizumab for acquired haemophilia A: A case series.

BACKGROUND: Emicizumab is approved to prevent bleeding in patients with congenital haemophilia A with or without inhibitors. However, no randomized trials addressed the efficacy of emicizumab in acquired haemophilia A (AHA). AIMS: To report the clinical and biochemical response of emicizumab in AHA. METHODS: This single-centre retrospective study included seven adults with AHA between November 2020 and May 2022. We collected patient characteristics, laboratory coagulation parameters, the use of haemostatic agents, bleeds and thrombotic events. Treatment was monitored using chromogenic FVIII assays. The assay with human reagents assesses both the emicizumab FVIII-like-activity and native patient FVIII-activity. The assay with bovine reagents only measures the patients' native FVIII-activity as emicizumab does not bind to bovine reagents. RESULTS: Patients presented with spontaneous hematoma (n = 7), intramuscular bleeding (n = 2), haematuria (n = 2) and/or gastro-intestinal bleeding (n = 2). Six patients had major bleedings. At diagnosis, APTT was prolonged (91 seconds, IQR 73-103), FVIII activity was 0% (IQR 0-1) and FVIII inhibitor 182 BU/mL (IQR 104-228). Emicizumab was administered weekly (3 mg/kg) for 4 weeks, and thereafter every 2 weeks until regression of the inhibitor. Three patients received activated FVIIa (cumulative dose of 1.7 mg/kg, IQR 1.2-2.2). All bleedings were controlled after treatment initiation, without further bleeds. After starting emicizumab, FVIII-like activity reached ≥5% at 12 days (IQR 7-14), whereas recovery of the intrinsic FVIII-activity ≥5% occurred at 128 days (IQR 88-173), coinciding with the disappearance of the FVIII inhibitor. There were no safety issues. CONCLUSION: In this AHA case series, no new clinically relevant bleeds were observed after initiation of emicizumab in conjunction with standard immunosuppressive therapy.

Venous Thromboembolism in Patients Discharged after COVID-19 Hospitalization.

BACKGROUND: Venous thromboembolism (VTE) is a frequent complication of COVID-19, so that the importance of adequate in-hospital thromboprophylaxis in patients hospitalized with COVID-19 is well established. However, the incidence of VTE after discharge and whether postdischarge thromboprophylaxis is beneficial and safe are unclear. In this prospective observational single-center study, we report the incidence of VTE 6 weeks after hospitalization and the use of postdischarge thromboprophylaxis. METHODS: Patients hospitalized with confirmed COVID-19 were invited to a multidisciplinary follow-up clinic 6 weeks after discharge. D-dimer and C-reactive protein were measured, and all patients were screened for deep vein thrombosis with venous duplex-ultrasound. Additionally, selected high-risk patients received computed tomography pulmonary angiogram or ventilation-perfusion (V/Q) scan to screen for incidental pulmonary embolism. RESULTS: Of 485 consecutive patients hospitalized from March through June 2020, 146 patients were analyzed, of which 39% had been admitted to the intensive care unit (ICU). Postdischarge thromboprophylaxis was prescribed in 28% of patients, but was used more frequently after ICU stay (61%) and in patients with higher maximal D-dimer and C-reactive protein levels during hospitalization. Six weeks after discharge, elevated D-dimer values were present in 32% of ward and 42% of ICU patients. Only one asymptomatic deep vein thrombosis (0.7%) and one symptomatic pulmonary embolism (0.7%) were diagnosed with systematic screening. No bleedings were reported. CONCLUSION: In patients who had been hospitalized with COVID-19, systematic screening for VTE 6 weeks after discharge revealed a low incidence of VTE. A strategy of selectively providing postdischarge thromboprophylaxis in high-risk patients seems safe and potentially effective.

Patient preferences for gene therapy in haemophilia: Results from the PAVING threshold technique survey.

OBJECTIVES: The aim of the Patient preferences to Assess Value IN Gene therapies (PAVING) study was to investigate trade-offs that adult Belgian people with haemophilia (PWH) A and B are willing to make when choosing between prophylactic factor replacement therapy (PFRT) and gene therapy. METHODS: The threshold technique was used to quantify the minimum acceptable benefit (MAB) of a switch from PFRT to gene therapy in terms of 'Annual bleeding rate' (ABR), 'Chance to stop prophylaxis' (STOP), and 'Quality of life' (QOL). The design was supported by stakeholder involvement and included an educational tool on gene therapy. Threshold intervals were analysed using interval regression models in Stata 16. RESULTS: A total of 117 PWH completed the survey. Mean thresholds were identified for all benefits, but substantial preference heterogeneity was observed; especially for the STOP thresholds, where the distribution of preferences was bimodal. Time spent on the educational tool and residence were found to impact MAB thresholds. The most accepted (88% of PWH) gene therapy profile investigated in this study comprised of zero bleeds per year (vs. six for PFRT), 90% chance to stop prophylaxis, no impact on QoL, and 10 years of follow-up on side effects (vs. 30 for PFRT). CONCLUSIONS: Results from this study proved the value of educating patients on novel treatments. Moreover, preference heterogeneity for novel treatments was confirmed in this study. In gene therapy decision-making, preference heterogeneity and the impact of patient education on acceptance should be considered.

Patient perspectives regarding gene therapy in haemophilia: Interviews from the PAVING study.

INTRODUCTION: Exploring patient perceptions regarding gene therapies may provide insights about their acceptability to patients. OBJECTIVE: To investigate opinions of people with haemophilia (PWH) regarding gene therapies. Moreover, this study aimed to identify patient-relevant attributes (treatment features) that influence PWH's treatment choices. METHODS: Semi-structured individual interviews were conducted with Belgian PWH, types A and B. A predefined interview guide included information sections and open, attribute ranking and case questions. Qualitative data were organized using NVivo 12 and analysed following framework analysis. Sum totals of scores obtained in the ranking exercise were calculated per attribute. RESULTS: In total, 20 PWH participated in the interviews. Most participants demonstrated a positive attitude towards gene therapy and were very willing (40%; n = 8) or willing (35%; n = 7) to receive this treatment. The following five attributes were identified as most important to PWH in making their choice: annual bleeding rate, factor level, uncertainty of long-term risks, impact on daily life, and probability that prophylaxis can be stopped. While participants were concerned about the uncertainty regarding long-term safety, most participants were less concerned about uncertainty regarding long-term efficacy. CONCLUSIONS: This qualitative study showed that most PWH have a positive attitude towards gene therapy and that besides efficacy, safety and the related uncertainties, also impact on daily life is important to patients. The identified patient-relevant attributes may be used by regulators, health technology assessment bodies and payers in their evaluation of gene therapies for haemophilia. Moreover, they may inform clinical trial design, pay-for-performance schemes and real-world evidence studies.

The biomechanical behaviour of ankle and foot joints during walking with shoes in patients with haemophilia.

INTRODUCTION: Patients with haemophilia (PwH) often prefer shod walking over barefoot walking as footwear offers ankle joint stability and comfort during gait. Yet, the biomechanical mechanisms contributing to the latter remain poorly understood. AIM: To explore the effect of shoes on the biomechanical functioning of the ankle and foot complex in PwH with and without haemophilic ankle arthropathy and to determine the amount of ankle joint loading during shod walking. METHODS: We analysed data of PwH without haemophilic ankle arthropathy (n = 5) and PwH with severe haemophilic ankle arthropathy (n = 17) and a control group (n = 17). During 3D gait analysis, a four-segment kinetic foot model was used to calculate kinematic and kinetic parameters of the ankle, Chopart, Lisfranc and first metatarsophalangeal (MTP 1) joints during both barefoot and shod walking. RESULTS: We found a significantly greater ankle joint power generation during shod walking compared to barefoot walking in PwH with severe haemophilic ankle arthropathy (P < .001). Chopart joint biomechanics were significantly lowered in all three groups during shod walking compared to barefoot walking. During shod walking, the ankle joint load was significantly lowered in both PwH groups (P = .039 and P = .002), but not in the control group (P = .952). CONCLUSION: Explorations in this study uncover a tendency that shoes alter the biomechanical functioning of the ankle and foot complex in PwH and simultaneously lower the ankle joint load during walking.

Acquired multi-segment foot kinematics in haemophilic children, adolescents and young adults with or without haemophilic ankle arthropathy.

INTRODUCTION AND AIM: The ankle joint remains vulnerable in children with haemophilia and is the primary joint affected. The purpose of this study was to dynamically characterize the segmental foot and ankle kinematics of male children, adolescents and young adults with or without ankle arthropathy. METHODS: The barefoot multi-segment foot kinematics of 70 ankles from 35 haemophilia subjects between 6 and 20 years old were captured with the Rizzoli Multi-Segment Foot Model. Joint damage of the tibiotalar and subtalar joints was scored using the IPSG-MRI score. The feet of patients with or without evidence of ankle arthropathy were compared with those of matched typically developing boys via a nonpaired comparison. The differences between the affected and nonaffected sides of patients with unilateral ankle arthropathy were assessed using a paired comparison. RESULTS: Subjects without arthropathy demonstrated a nonsignificant trend towards a higher frontal plane range of motion (RoM) at the midfoot upon loading response and a lower sagittal plane RoM at the midfoot during midstance. No differences were observed between the affected side group and their matched control group. The affected side of unilaterally affected subjects exhibited a nonsignificant tendency towards a higher frontal plane RoM at the ankle joint upon loading response and terminal stance compared to the healthy side. CONCLUSION: Most patients maintained physiological rocker function of the ankle and had no (mal)adaptive motion patterns in the more distal joints of the foot. Therefore, established structural lesions may remain subclinical with respect to moderate functional activities like walking.

Clinical gait features are associated with MRI findings in patients with haemophilic ankle arthropathy.

INTRODUCTION: Haemophilic ankle arthropathy due to repeated joint bleeds often leads to altered gait in adult patients with haemophilia. AIM: To investigate the association between clinical gait features and blood-induced ankle joint damage scored using MRI findings in patients with haemophilic ankle arthropathy. METHODS: This observational study investigated 48 ankles of 24 patients with severe haemophilia (median age of 33 years). Blood-induced ankle joint damage was scored by an experienced radiologist using the International Prophylaxis Study Group (IPSG-)MRI score which evaluates the presence or absence of effusion, synovial hypertrophy, haemosiderin, surface erosions, subchondral cysts and cartilage degeneration. Using 3D gait analysis, peak ankle joint power generation and absorption (W/kg) were measured for each ankle since these are surrogate measures for joint loading during walking. Associations between MRI findings and these two clinical gait features were calculated using Spearman's ρ correlation with an α-level correction (α = 0.01) for multiple tests. RESULTS: We found large negative associations between ankle joint peak power generation and IPSG-MRI score (ρ = -0.631; P = <.001), IPSG-MRI osteochondral subscore (ρ = -0.701; P = <.001), severity of synovial hypertrophy (ρ = -0.507; P = <.001) and haemosiderin (ρ = -0.400; P = .005). Associations were also found for ankle joint peak power absorption and IPSG-MRI score (ρ = -0.425; P = .003) and IPSG-MRI osteochondral subscore (ρ = -0.556; P = <.001). CONCLUSION: Severe blood-induced ankle joint damage relates to a lowered tolerance towards ankle joint mechanical loading during walking in patients with haemophilia.