Frequency of natural regulatory T cells specific for factor VIII in the peripheral blood of healthy donors.

Tolerance to self-proteins involves multiple mechanisms, including conventional CD4+ T-cell (Tconv) deletion in the thymus and the recruitment of natural regulatory T cells (nTregs). The significant incidence of autoantibodies specific for the blood coagulation factor VIII (FVIII) in healthy donors illustrates that tolerance to self-proteins is not always complete. In contrast to FVIII-specific Tconvs, FVIII-specific nTregs have never been revealed and characterized. To determine the frequency of FVIII-specific Tregs in human peripheral blood, we assessed the specificity of in vitro expanded Tregs by the membrane expression of the CD137 activation marker. Amplified Tregs maintain high levels of FOXP3 expression and exhibit almost complete demethylation of the FOXP3 Treg-specific demethylated region. The cells retained FOXP3 expression after long-term culture in vitro, strongly suggesting that FVIII-specific Tregs are derived from the thymus. From eleven healthy donors, we estimated the frequencies of FVIII-specific Tregs at 0.17 cells per million, which is about 10-fold lower than the frequency of FVIII-specific CD4+ T cells we previously published. Our results shed light on the mechanisms of FVIII tolerance by a renewed approach that could be extended to other self- or non-self-antigens.

Dissection of pleiotropic effects of variants in and adjacent to F8 exon 19 and rescue of mRNA splicing and protein function.

The pathogenic significance of nucleotide variants commonly relies on nucleotide position within the gene, with exonic changes generally attributed to quantitative or qualitative alteration of protein biosynthesis, secretion, activity, or clearance. However, these changes may exert pleiotropic effects on both protein biology and mRNA splicing due to the overlapping of the amino acid and splicing codes, thus shaping the disease phenotypes. Here, we focused on hemophilia A, in which the definition of F8 variants' causative role and association to bleeding phenotypes is crucial for proper classification, genetic counseling, and management of affected individuals. We extensively characterized a large panel of hemophilia A-causing variants (n = 30) within F8 exon 19 by combining and comparing in silico and recombinant expression analyses. We identified exonic variants with pleiotropic effects and dissected the altered protein features of all missense changes. Importantly, results from multiple prediction algorithms provided qualitative results, while recombinant assays allowed us to correctly infer the likely phenotype severity for 90% of variants. Molecular characterization of pathogenic variants was also instrumental for the development of tailored correction approaches to rescue splicing affecting variants or missense changes impairing protein folding. A single engineered U1snRNA rescued mRNA splicing of nine different variants and the use of a chaperone-like drug resulted in improved factor VIII protein secretion for four missense variants. Overall, dissection of the molecular mechanisms of a large panel of HA variants allowed precise classification of HA-affected individuals and favored the development of personalized therapeutic approaches.

Safety and efficacy of damoctocog alfa pegol prophylaxis in patients with severe haemophilia A: Results of an interventional, post-marketing study.

INTRODUCTION: Damoctocog alfa pegol (BAY 94-9027, Jivi® ) is an approved extended half-life factor VIII (FVIII) for treatment of previously treated patients with haemophilia A aged ≥12 years. We report the final results of an interventional, post-marketing study of damoctocog alfa pegol prophylaxis in patients with severe haemophilia A. METHODS: In this open-label, interventional, post-marketing, phase 4 trial (NCT04085458), previously FVIII-treated patients with severe haemophilia A aged ≥18 years received damoctocog alfa pegol for ≥100 exposure days (EDs). Patients initially received 45 IU/kg every 5 days (recommended) or 40 IU/kg twice-weekly. At Visit 3, patients' doses could be increased, or treatment frequency adapted. The primary endpoint was FVIII inhibitor development (titre ≥.6 Bethesda units). Secondary endpoints included anti-polyethylene glycol (PEG) antibody development, treatment-emergent adverse events (AEs) and annualized bleeding rate (ABR). RESULTS: Overall, 36 patients were enrolled; 32 patients received treatment, of whom, 27 completed the study. No patients developed FVIII inhibitors; three tested transiently positive for low-titre anti-PEG antibodies without clinical relevance. Three patients reported study-drug-related AEs of mild or moderate intensity. Two patients discontinued the study due to AEs. No deaths occurred. Most patients (70%) were treated with E5D/E7D regimens. The median (Q1;Q3) total ABR (N = 30) was 3.0 (.0;9.0) pre-study and 1.8 (.7;5.9) during the study. CONCLUSION: Damoctocog alfa pegol individualized prophylaxis regimens were well-tolerated with no immunogenicity concerns. ABRs improved following the switch from pre-study prophylaxis to damoctocog alfa pegol prophylaxis. These results support the favourable safety and efficacy profile of damoctocog alfa pegol prophylaxis.

Peri-operative desmopressin combined with pharmacokinetic-guided factor VIII concentrate in non-severe haemophilia A patients.

INTRODUCTION: Non-severe haemophilia A patient can be treated with desmopressin or factor VIII (FVIII) concentrate. Combining both may reduce factor consumption, but its feasibility and safety has never been investigated. AIM: We assessed the feasibility and safety of combination treatment in nonsevere haemophilia A patients. METHODS: Non-severe, desmopressin responsive, haemophilia A patients were included in one of two studies investigating peri-operative combination treatment. In the single-arm DAVID study intravenous desmopressin (0.3 µg/kg) once-a-day was, after sampling, immediately followed by PK-guided FVIII concentrate, for maximally three consecutive days. The Little DAVID study was a randomized trial in patients undergoing a minor medical procedure, whom received either PK-guided combination treatment (intervention arm) or PK-guided FVIII concentrate only (standard arm) up to 2 days. Dose predictions were considered accurate if the absolute difference between predicted and measured FVIII:C was ≤0.2 IU/mL. RESULTS: In total 32 patients (33 procedures) were included. In the DAVID study (n = 21), of the FVIII:C trough levels 73.7% (14/19) were predicted accurately on day 1 (D1), 76.5% (13/17) on D2. On D0, 61.9% (13/21) of peak FVIII:C levels predictions were accurate. In the Little DAVID study (n = 12), on D0 83.3% (5/6) FVIII:C peak levels for both study arms were predicted accurately. Combination treatment reduced preoperative FVIII concentrate use by 47% versus FVIII monotherapy. Desmopressin side effects were mild and transient. Two bleeds occurred, both despite FVIII:C > 1.00 IU/mL. CONCLUSION: Peri-operative combination treatment with desmopressin and PK-guided FVIII concentrate dosing in nonsevere haemophilia A is feasible, safe and reduces FVIII consumption.

A global comparative field study to evaluate the factor VIII activity of efanesoctocog alfa by one-stage clotting and chromogenic substrate assays at clinical haemostasis laboratories.

INTRODUCTION: Structural and chemical modifications of factor VIII (FVIII) products may influence their behaviour in FVIII activity assays. Hence, it is important to assess the performance of FVIII products in these assays. Efanesoctocog alfa is a new class of FVIII replacement therapy designed to provide both high sustained factor activity levels and prolonged plasma half-life. AIM: Evaluate the accuracy of measuring efanesoctocog alfa FVIII activity in one-stage clotting assays (OSAs) and chromogenic substrate assays (CSAs). METHODS: Human plasma with no detectable FVIII activity was spiked with efanesoctocog alfa or a full-length recombinant FVIII product comparator, octocog alfa, at nominal concentrations of 0.80 IU/mL, 0.20 IU/mL, or 0.05 IU/mL, based on labelled potency. Clinical haemostasis laboratories (N = 35) tested blinded samples using in-house assays. Data from 51 OSAs (14 activated partial thromboplastin time [aPTT] reagents) and 42 CSAs (eight kits) were analyzed. RESULTS: Efanesoctocog alfa activity was reliably (±25% of nominal activity) measured across all concentrations using OSAs with Actin FSL and multiple other aPTT reagents. Under- and overestimation of FVIII activity occurred with some reagents. No specific trend was observed for any class of aPTT activators. A two- to three-fold overestimation was consistently observed using CSAs and the OSA with Actin FS as the aPTT reagent across evaluated concentrations. CONCLUSION: Under- or overestimation occurred with some specific OSAs and most CSAs, which has been previously observed with other modified FVIII replacement products. Efanesoctocog alfa FVIII activity was measured with acceptable accuracy and reliability using several OSA methods and commercial plasma standards.

Unearthing the genotype-inhibitor phenotype association in severe haemophilia A: A north Indian cohort study.

INTRODUCTION: Various risk factors for inhibitor development in haemophilia A (HA) have been described but Indian data remains scanty. AIM: We aimed to evaluate the genetic changes in Indian HA-patients that are associated with the development of inhibitors. METHODS: All HA-patients with inhibitors who availed coagulation-laboratory services from January-2015 till December-2021 and had their samples preserved for DNA extraction were included in this study. An equal number of severity-matched HA patients without inhibitors were also included as controls. Intron 22 and intron 1 inversions in Factor VIII gene were identified using inverse-shifting-PCR. Inversion-negative patients were further assessed by targeted NGS, MLPA. RESULTS: Thirty HA-patients with inhibitors were identified. All had severe-HA. Thirty severe-HA-patients without inhibitors were also included as controls. Intron 22 inversion (63.3%) and large deletions (15%) were the commonest variants identified. There was no difference in genetic variants in patients with low and high titre inhibitors. A3, A2 and C2 were the most common domains involved in inversion-negative patients with inhibitors. However, there was no significant difference in domain involvement among inversion-negative patients with and without inhibitors. Seven novel-variants were identified, including three large deletions, one large duplication and two nonsense variants in inhibitor-positive patients, and one frameshift variant in inhibitor-negative patient. After adjusting for clinical risk-factors, large deletions were independently associated with the presence of inhibitors [aOR:6.1 (1.41-56.3)]. CONCLUSION: Intron 22 inversions are the commonest variant in Indian patients with severe-HA. Large deletions predispose to inhibitor development independent of clinical risk factors.

Measurement of recombinant porcine factor VIII in patients with congenital haemophilia A and inhibitors in the presence of emicizumab.

INTRODUCTION: Recombinant porcine factor VIII (rpFVIII) is a treatment option for break-through bleeds in patients with congenital haemophilia A with inhibitors (CHAwI) on emicizumab. However, there are limited data about the measurement of rpFVIII in the presence of emicizumab. AIM: To analyse whether rpFVIII can be measured with a chromogenic assay with bovine component (bCSA) in plasma from CHAwI on emicizumab treatment. METHODS: In the first part of the study, FVIII deficient plasma was spiked with rpFVIII, in the second part, commercial plasma from CHAwI was spiked with emicizumab and rpFVIII, and in the third part, plasma from CHAwI on emicizumab treatment was spiked with rpFVIII. FVIII was then measured with bCSA and a chromogenic assay with human component (hCSA). Thrombin generation (TG) and clot-waveform analysis (CWA) were also carried out. RESULTS: The recovery of rpFVIII measured with bCSA is approximately 80% and is further influenced by the presence of an anti-porcine inhibitor. rpFVIII assessed with hCSA was influenced by emicizumab. CWA and TG showed a weak correlation with baseline emicizumab concentration, but peak thrombin and CWA correlated well with increasing emicizumab concentrations and rpFVIII activities. CONCLUSION: This study indicates that rpFVIII can be measured in the presence of emicizumab with a bCSA. A calibration curve for the measurement of rpFVIII with bCSA should be established.

Unresolved hemostasis issues in haemophilia.

Despite rapid technological advancement in factor and nonfactor products in the prevention and treatment of bleeding in haemophilia patients, it is imperative that we acknowledge gaps in our understanding of how hemostasis is achieved. The authors will briefly review three unresolved issues in persons with haemophilia (PwH) focusing on the forgotten function that red blood cells play in hemostasis, the critical role of extravascular (outside circulation) FIX in hemostasis in the context of unmodified and extended half-life FIX products and finally on the role that skeletal muscle myosin plays in prothrombinase assembly and subsequent thrombin generation that could mitigate breakthrough muscle hematomas.

A post hoc analysis of PROTECT VIII kids assessing long-term efficacy and safety of damoctocog alfa pegol in adolescents with severe haemophilia A.

INTRODUCTION: The safety and efficacy of the extended half-life factor VIII (FVIII) product damoctocog alfa pegol (BAY 94-9027, Jivi®) has been demonstrated in the PROTECT VIII Kids study (NCT01775618), where male previously-treated patients (PTPs) aged <12 years old with severe haemophilia A and ≥ 50 exposure days (EDs) were treated prophylactically. The PROTECT VIII Kids extension study assessed the long-term safety and efficacy of damoctocog alfa pegol in the same population. AIM: To evaluate the long-term impact of damoctocog alfa pegol in a post hoc subgroup analysis of adolescent patients in the PROTECT VIII Kids study and its extension from 12th birthday onwards. METHODS: The current analysis included PTPs aged ≥12 years old, who remained in the extension for ≥6 months following their 12th birthday. The observation period was defined as the time from 12th birthday to the end of the extension period; all data from this birthday were included whether in the main study or extension phase. The main efficacy variable was annualised bleeding rate (ABR) and the main safety variable was the frequency of inhibitor development. RESULTS: This subgroup analysis comprised 25 patients. Median observation time after 12th birthday was 3.2 years. Median total/joint/spontaneous ABRs in the observation period were 1.7/0.7/0.3, respectively. Safety findings were consistent with those reported for the overall study population; no confirmed FVIII inhibitors or anti-drug antibodies were reported. CONCLUSIONS: Damoctocog alfa pegol is efficacious with a favourable safety profile in adolescents with haemophilia A, supporting its long-term use in children and adolescents.

CHIEF: A retrospective self-control study of children with severe hemophilia A without inhibitors comparing emicizumab to FVIII prophylaxis.

BACKGROUND: Hemophilia A (HA) is an X-linked bleeding disorder diagnosed by a deficiency in factor VIII (FVIII). For severe HA (SHA), prophylaxis clotting factor concentrates (CFC) has become the standard of care; however, it imparts a high treatment burden and typically results in an annualized bleeding rate (ABR) of 2-6. Emicizumab, a subcutaneously administered FVIII substitute, has become the de facto standard-of-care prophylaxis for children with SHA in many countries. Previous clinical trials of emicizumab have assessed ABR in patients greater than 12 years without inhibitors, and in children less than 12 years with inhibitors; however, there is little information published regarding the ABR of emicizumab compared to CFC in non-inhibitor SHA children. METHODS: Using a retrospective electronic medical record chart review, we conducted a self-control analysis of 15 patients less than 12 years of age during equivalent periods of CFC versus emicizumab prophylaxis. RESULTS: The mean ABR on CFC and emicizumab was 1.79 and 1.13 (p = .092), respectively, with a substantially decreased rate of joint bleeds (CFC 0.94; emicizumab 0.33; p = .001) and spontaneous bleeds (CFC 0.79; emicizumab 0.23; p = .008). No safety events were recorded for patients while administering emicizumab. The mean annual cost of CFC prophylaxis was $515,340 (SD $199,540), compared to $328,410 (SD $137,230) for emicizumab prophylaxis (p < .001). CONCLUSION: Emicizumab resulted in an improved ABR compared to CFC, especially for joint and spontaneous bleeds, had fewer administration complications, and was substantially less expensive compared to CFC prophylaxis; however, more research is necessary for a complete understanding of the effect of emicizumab on joint health and muscle bleeds.

Effect of factor VIII and FVIII/PC ratio on portal vein thrombosis in liver cirrhosis: a systematic review and meta­analysis.

BACKGROUND: To date, there is an ongoing debate regarding the ability to predict PVT development using markers of FVIII or FVIII/PC ratio. This study presents evidence-based medical findings on the influence of FVIII activity levels and FVIII/PC values in the formation of PVT in cirrhosis. METHODS: The search for original studies on risk factors for portal vein thrombosis (PVT) associated with cirrhosis was conducted, which primarily focused on comparing circulating FVIII activity levels or FVIII/PC ratio in cirrhotic patients with and without PVT. The quality of evidence from each study was assessed using the Newcastle-Ottawa Scale. RESULTS: The meta-analysis included a total of 10 original studies. In total, 2250 cirrhotic patients were included, with 414 having PVT and 1836 without PVT. The pooled analysis using a random-effects model showed no significant difference in standardized mean difference (SMD) for FVIII activity levels in cirrhotic patients with or without PVT (SMD = 0.12, 95% CI=-0.46 to 0.70, P = 0.68), but there was significant heterogeneity (I2 = 95.52%, P = 0.00). Meta-regression analysis indicated that differences in mean FVIII activity levels in the PVT group, the number of cases in the non-PVT group, and the study design methods partially contributed to the heterogeneity (P < 0.05). However, compared to the non-PVT group, the PVT group had higher FVIII/PC ratio with a statistically significant difference (SMD = 0.39, 95% CI: 0.15 to 0.63, P = 0.00), and there was no significant heterogeneity (I2 = 28.62%). CONCLUSION: In conclusion, the FVIII/PC ratio not only reflects the severity of liver disease, but also can be used as one of the predictors of PVT development.

Identification of the Efficient Enhancer Elements in FVIII-Padua for Gene Therapy Study of Hemophilia A.

Hemophilia A (HA) is a common X-linked recessive hereditary bleeding disorder. Coagulation factor VIII (FVIII) is insufficient in patients with HA due to the mutations in the F8 gene. The restoration of plasma levels of FVIII via both recombinant B-domain-deleted FVIII (BDD-FVIII) and B-domain-deleted F8 (BDDF8) transgenes was proven to be helpful. FVIII-Padua is a 23.4 kb tandem repeat mutation in the F8 associated with a high F8 gene expression and thrombogenesis. Here we screened a core enhancer element in FVIII-Padua for improving the F8 expression. In detail, we identified a 400 bp efficient enhancer element, C400, in FVIII-Padua for the first time. The core enhancer C400 extensively improved the transcription of BDDF8 driven by human elongation factor-1 alpha in HepG2, HeLa, HEK-293T and induced pluripotent stem cells (iPSCs) with different genetic backgrounds, as well as iPSCs-derived endothelial progenitor cells (iEPCs) and iPSCs-derived mesenchymal stem cells (iMSCs). The expression of FVIII protein was increased by C400, especially in iEPCs. Our research provides a novel molecular target to enhance expression of FVIII protein, which has scientific value and application prospects in both viral and nonviral HA gene therapy strategies.

[Successful immunosuppressive therapy in female hemophilia A developing inhibitor after perioperative administration of factor VIII products].

A 62-year-old woman was diagnosed as a hemophilia A carrier (factor VIII activity 35%) on preoperative examination of an ovarian tumor. A total of 35,600 units of recombinant factor VIII products was administered perioperatively. On postoperative day 95, a subcutaneous hematoma formed and immunosuppressive therapy with prednisolone was started based on an APTT of 66 seconds, factor VIII (FVIII) activity of 3%, and FVIII inhibitor of 1 BU/ml. During this treatment, the patient was hospitalized due to ankle joint bleeds and required hemostatic treatment, but the inhibitor disappeared and FVIII activity recovered to 30% after postoperative day 438 with cyclophosphamide. F8 analysis revealed the patient carried a heterozygosity of p.Arg391Cys, which has previously been categorized as cross-reacting material (CRM)-positive severe hemophilia A. No high-risk mutations for inhibitor development were found. We also report the results of a desmopressin acetate hydrate test administered to the patient to prepare for future treatment in case of hemorrhage, since high-dose FVIII administration may have been a factor in inhibitor development.

Microfluidic devices for studying coagulation biology.

The ability to study the behavior of cells, proteins, and cell-cell or cell-protein interactions under dynamic forces such as shear stress under fluid flow, provides a more accurate understanding of the physiopathology of hemostasis. This review touches upon the traditional methods for studying blood coagulation and platelet aggregation and provides an overview on cellular and protein response to shear stress. We also elaborate on the biological aspects of how cells recognize mechanical forces and convert them into biochemical signals that can drive various signaling pathways. We give a detailed description of the various types of microfluidic devices that are employed to study the complex processes of platelet aggregation and blood coagulation under flow conditions as well as to investigate endothelial shear-response. We also highlight works mimicking artificial vessels as platforms to study the mechanisms of coagulation, and finish our review by describing anticipated clinical uses of microfluidics devices and their standardization.

Whole F8 gene sequencing combined with splicing functional analyses led to a substantial increase of the molecular diagnosis yield for non-severe haemophilia A.

INTRODUCTION: Conventional genetic investigation fails to identify the F8 causal variant in 2.5%-10% of haemophilia A (HA) patients with non-severe phenotypes. In these cases, F8 deep intronic variants could be causal. AIM: To identify pathogenic F8 deep intronic variants in genetically unresolved families with non-severe HA analysed in the haematology laboratory of the Hospices Civils de Lyon. METHODS: The whole F8 was analysed by next generation sequencing. The pathogenic impact of candidate variants identified was assessed using both in silico analysis (MaxEntScan and spliceAI) and functional analysis (RNA or minigene assay). RESULTS: Sequencing was performed in 49/55 families included for which a DNA sample from a male propositus was available. In total, 33 candidate variants from 43 propositi were identified. These variants corresponded to 31 single nucleotide substitutions, one 173-bp deletion, and an 869-bp tandem triplication. No candidate variant was found in six propositi. The most frequent variants found were the association of [c.2113+1154G>C and c.5374-304C>T], identified in five propositi, and the c.2114-6529C>G identified in nine propositi. Four variants had been previously described as HA-causing. Splicing functional assay found a deleterious impact for 11 substitutions (c.671-94G>A, c.788-312A>G, c.2113+1154G>C, c.2114-6529C>G, c.5999-820A>T, c.5999-786C>A, c.5999-669G>T, c.5999-669G>A, c.5999-669G>C, c.6900+4104A>C, and c.6901-2992A>G). The HA-causing variant was identified in 33/49 (67%) cases. In total, F8 deep intronic variants caused 8.8% of the non-severe HA among the 1643 families analysed in our laboratory. CONCLUSION: The results emphasise the value of whole F8 gene sequencing combined with splicing functional analyses to improve the diagnosis yield for non-severe HA.

Effects of PK-guided prophylaxis on clinical outcomes and FVIII consumption for patients with moderate to severe Haemophilia A.

INTRODUCTION: In recent years, there has been increased focus on individualizing treatment for persons with hemophilia including pharmacokinetic-guided (PK) dosing. AIMS: In this retrospective study clinical outcomes before and after PK-guided prophylaxis were examined. MATERIALS AND METHODS: Eight Haemophilia Treatment Centres from the United States participated in the study and included 132 patients classified into two cohorts: those undergoing a PK-assessment for product switch (switchers) or to optimize treatment (non-switchers). Subset analyses for the two most common products and patients with dosing per prescription label were included for annual bleeding rates (ABR), mean weekly consumption outcomes, and annualized cost of prophylaxis. RESULTS: The most common products before and after index date were octocog alfa, rurioctocog alfa pegol, and efmoroctocog alfa. Seventy-four (56%) patients were identified as switchers and 58 (44%) patients were classified as non-switchers. The majority of patients (78.0%) experienced either a decrease in ABR post-index or maintained 0 ABR during pre- and post-index time periods, with similar proportions identified in both switchers (77.0%) and non-switchers (79.3%) populations. Non-switchers were identified as having no significant change in cost of therapy, while switchers experienced increased cost of therapy driven by higher price of extended half-life products. Within subset analyses, patients receiving rurioctocog alfa pegol and efmoroctocog alfa had mean ABR under 1 after index date. CONCLUSION: PK-guided prophylaxis has the potential to improve clinical outcomes without increase in cost of therapy for patients maintaining product and can aid in maintaining effective protection against bleeds in those switching product.

Modulation of factor VIII pharmacokinetics by genetic components in factor VIII receptors.

INTRODUCTION: Gene variation in receptors for circulating factor VIII (FVIII) is candidate to explain the large inter-patient variability of infused FVIII pharmacokinetics (PK) in haemophilia A (HA). AIM: To compare in an Italian HA cohort (n = 26) the influence on FVIII PK of genetic components in four von Willebrand factor (VWF)/FVIII receptors. METHODS: Genotypes of low-density lipoprotein receptor (LDLR), asialoglycoprotein receptor minor subunit (ASGR2), family 4 member M (CLEC4M), stabilin2 (STAB2) and ABO blood-group, and VWF:Ag levels were included as independent variables in linear regression analyses of two-compartment model (TCM) - standard half-life (SHL) FVIII PK parameters. RESULTS: In the initial FVIII distribution phase, the STAB2 rs4981022 AA, ASGR2 rs2289645 TT and LDLR rs688 TT genotypes may contribute to increase Cmax , and prolong or shorten AlphaHL. In the elimination phase, a shorter BetaHL was associated with the CLEC4M rs868875 GG (beta-coefficient .366, p = .025) and ASGR2 rs2289645 TC (beta-coefficient .456, p = .006) genotypes, which also showed shorter mean residence time (MRT) than TT genotypes (p = .021). The alpha and beta phase effects were independent of ABO and VWF:Ag levels at baseline. The association of the LDLR rs2228671 genotypes with clearance was independent of ABO (beta-coefficient -.363, p = .035) but not of other receptors or VWF:Ag, which may point out multiple and competing interactions. CONCLUSIONS: With the limitation of the small number of HA patients, these observations highlight multiple genetic components acting in distinct phases of FVIII PK and contributing to explain FVIII PK variability. This analysis provides candidates for genotype-based, individual tailoring of FVIII substitutive treatment.

Cases of less-than-expected FVIII activity in previously treated patients during post-marketing surveillance of N8-GP.

INTRODUCTION: Turoctocog alfa pegol (N8-GP) is a glycoPEGylated, extended half-life (EHL), human recombinant factor VIII (FVIII) approved for the treatment and prevention of bleeding episodes in patients with haemophilia A. Since its launch in August 2019, > 800 patients have been treated worldwide. AIM: To present data from identified post-marketing cases of less-than-expected FVIII activity in previously treated patients (PTPs) without inhibitors after switching to N8-GP. METHODS: The post-marketing safety database was searched using keywords such as 'coagulation FVIII level decreased'. Identified cases reported prior to 13 October 2021 were included in this report. Cases in which patients had FVIII inhibitors were excluded. RESULTS: Here we report 14 cases of less-than-expected FVIII activity. Details varied greatly amongst the cases. At presentation, FVIII activity ranged from 1% (15 min post-dose) to 51% (2 days post-dose). Seven patients experienced bleeding episodes after switching to N8-GP with heterogeneity in bleeding presentations. Six out of seven patients who were tested for anti-PEG IgG and/or IgM antibodies were positive. In all known cases, FVIII activity returned to the expected range when switched to an alternative FVIII replacement product. CONCLUSION: In conclusion, the 14 reported cases of less-than-expected FVIII activity, without presence of detectable FVIII inhibitors, presented with heterogenous characteristics, and wide variations in FVIII activity and anti-PEG antibody titre. FVIII activity returned to the expected range after switching to alternative FVIII products. In line with WFH guidelines, monitoring of FVIII activity can ensure FVIII activity in the expected range. The safety surveillance of N8-GP continues.

Real-world safety and effectiveness of recombinant porcine sequence factor VIII in acquired haemophilia A: A non-interventional, post-authorization safety study.

INTRODUCTION: Recombinant porcine factor VIII (rpFVIII, susoctocog alfa) is indicated for the treatment of bleeding episodes in adults with acquired haemophilia A (AHA). AIM: To provide long-term real-world safety and effectiveness data for rpFVIII in the management of AHA bleeding episodes. METHODS: US PASS (NCT02610127) was a multicentre, uncontrolled, open-label, post-marketing safety surveillance study conducted in adults with AHA. Data were collected retrospectively or prospectively for 180 days after rpFVIII treatment. The primary outcome was the incidence of treatment-related serious adverse events (SAEs). Secondary outcomes included haemostatic effectiveness of rpFVIII and rpFVIII utilization. RESULTS: Fifty-three patients were enrolled from December 2015 to June 2019 (prospective, n = 30; retrospective, n = 23). Six patients experienced seven treatment-related SAEs (incidence 12.0%). The most common treatment-related SAE was FVIII inhibition (inhibiting antibodies to rpFVIII; incidence 8.0%, 95% CI: 2.2-19.2). Five patients reported seven thromboembolic events; one was an SAE and possibly related to rpFVIII. Of bleeding events treated with rpFVIII, 80.3% (57/71) of bleeds resolved with rpFVIII. The median (range) dose of rpFVIII per infusion was 50 (10-300) units/kg, with a median (range) of 6.0 (1-140) infusions and a median (range) time from bleed onset to bleed resolution of 14.0 (2.0-132.7) days. CONCLUSION: In this real-world study of rpFVIII for AHA, no new safety signals were identified compared with previous clinical trial findings. Eighty percent of bleeds resolved with rpFVIII treatment.

No immunological changes after factor VIII product switch: An in depth analysis in haemophilia A patients.

BACKGROUND: A challenging complication in the treatment of haemophilia A is the formation of neutralizing anti-FVIII antibodies (inhibitors). There is ongoing debate on the effect of FVIII product and inhibitor risk, rendering patients and physicians reluctant to switch FVIII-products. AIM: This study aimed to evaluate changes in the immune profile of haemophilia A patients after switching FVIII products and their possible relation to inhibitor development. Secondary, FVIII efficacy after switching were assessed. METHODS: Patients, who switched FVIII-products between 2017-2019, were included in this single centre cohort study. Prospective comparison of immunoregulatory cells and markers by flow-cytometry before and after the switch was performed in a subgroup. For the total cohort clinical data regarding inhibitor development and FVIII efficacy 1 year before and after switching were retrospectively collected. RESULTS: One-hundred patients (including 39 with prospective immunological assessment) were analyzed, of which 31% switched from plasma-derived (pdFVIII) to recombinant standard half-life FVIII (SHL-rFVIII), 47% between different SHL-rFVIII, and 22% from pdFVIII/SHL-rFVIII to rFVIII-Fc. No remarkable changes in immunoregulatory cell functions were observed after switching, regardless the type of switch. None of the patients developed an inhibitor. FVIII efficacy, that is, FVIII usage, half-life and annual bleeding rate (ABR), was similar before and after switch for the SHL products, whereas rFVIII-Fc associated with a longer half-life (13.1 vs. 15.0 h) and lower ABR (3.0 vs. 1.0). CONCLUSIONS: Switching to a different FVIII product was not associated with inhibitor development, nor with differences in the immune profile. Switching to rFVIII-Fc lead to lower ABR.