Factor VIII Inhibitors Research Articles

Correlations of Plasma Cytokine Levels and Anti-FVIII Antibodies during Immune Tolerance Induction

IntroductionThe development of neutralizing anti-FVIII antibodies (inhibitors) with reduced or absent activity of substituted factor VIII (FVIII) remains the most serious complication of hemophilia A therapy (Kempton, 2014). Frequent and high doses of FVIII with or without bypassing products can reestablish immune tolerance in 60-70% of patients. Polymorphism in immune response genes including IL-10 and TNFa were identified as risk factors for inhibitor development (Astermark, 2006). Cross-sectional studies showed different cytokine profiles in patients with hemophilia, especially in those with history of an inhibitor (Oliveira, 2013). In this study cytokine profiles were monitored longitudinally during immune tolerance induction (ITI).Methods107 plasma samples from 18 patients were collected during the RES.I.S.T Experienced and Naive trial, which included patients with a poor prognosis for ITI success (Gringeri, 2007). We quantified 14 cytokines in each sample by using a Human High Sensitivity T-Cell Discovery Array 14-Plex (Eve Technologies Corp, Calgary, AB, Canada). ELISA based FVIII antibody assays were used for anti-FVIII IgG detection. FVIII inhibitor titers (Bethesda assay, BU) were measured and available for the analysis. The cut-off for a positive inhibitor was >0,6 BU mL-1. Bethesda titers (BUpos) between 0,6 - <5,0 were considered as low titer (BUlow), whereas BU ≥5 as high titer (BUhigh). Statistical analyses were performed using GraphPad Prism 7. Mann-Whitney U tests and Spearman correlation tests considered significant when P value <0.05.ResultsPlasma levels of TNFa (P=0,014) and IL-8 (P=0,048) were positively correlated with FVIII inhibitor titers. Negative correlation was found in levels of IL-10 (P=0,041), IL-12 (P=0,038) and IL-1B (P=0,026). When cytokine levels of plasma samples with detectable and undetectable FVIII inhibitor titers were compared, significant higher plasma levels of TNFa (median: 11,56pg/ml, 8,11pg/ml; P=0,016) and lower levels of IL-12 (median: 4,29 pg/ml, 6,25 pg/ml; P=0,047) and IL-23 (median: 1016 pg/ml, 1353 pg/ml; P=0,049) were measured in samples with detectable FVIII inhibitor (BUpos). Furthermore, TNFa levels were higher in BUlow (median: 10,83 pg/ml; P=0,047) as well as in BUhigh samples (median: 11,75 pg/ml; P=0,019), compared to BUneg (median: 8,11 pg/ml). Cytokine concentrations of IL-1B (median: 2,64 pg/ml, 3,77 pg/ml; P=0,023), IL-2 (median: 2,44 pg/ml, 2,97pg/ml; P=0,043) and IL-17 (median: 15,79 pg/ml, 19,42 pg/ml; P=0,036) were significantly lower in BUhigh plasma samples compared to BUneg. Additionally, plasma level of IL-10 correlated negatively with levels of anti-FVIII IgG (P=0.045).ConclusionThis is the first study of cytokine measurement in a longitudinal setting as well as during ITI in patients with hemophilia. FVIII inhibitors and anti-FVIII IgG antibodies were correlated to IL-10 and TNFa levels - of note, polymorphisms in the genes of these cytokines are a known risk factor for inhibitor development. Furthermore, IL-12, IL-17 and IL-23 levels were higher in samples with loss of FVIII Inhibitors. In addition to prediction of inhibitor development, cytokine profiles might serve as prognostic factors for ITI success and considering the emerging evidence of the IL-17-IL-23 immune axis in autoimmunity might also be promising therapeutic approaches for higher ITI success rates. DisclosuresEwing:Genentech: Honoraria; Shire: Honoraria; Bayer: Honoraria; Grifols: Honoraria; CSL Behring: Honoraria; Novo Nordisk: Honoraria; Hema Biologics: Honoraria; Biogen: Research Funding. Koenigs:Jansen: Research Funding; Gilead: Research Funding; Biotest: Research Funding, Speakers Bureau; Bayer: Consultancy, Research Funding, Speakers Bureau; Pfizer: Research Funding, Speakers Bureau; Intersero: Research Funding; CSL Behring: Consultancy, Research Funding; EU (IMI, FP7): Research Funding; Sobi: Consultancy, Research Funding, Speakers Bureau; Shire: Consultancy, Research Funding; Novo Nordisk: Consultancy, Speakers Bureau; Bioverativ: Consultancy; Roche/Chugai: Consultancy.

Overshoot of FVIII Activity in Patients with Acquired Hemophilia

Background: Acquired hemophilia A (AHA) is a rare, life-threatening bleeding disorder caused by autoantibodies against coagulation factor VIII (FVIII) [J Thromb Haemost. 2011;9:226-235]. The disease is characterized by spontaneous hemorrhage or prolonged bleeding after surgery, trauma, or other invasive procedures in patients with neither family nor personal histories of hemorrhagic diathesis [BMC Res Notes. 2010;3:161]. The main goal of AHA therapy is arrest of bleeding by eliminating FVIII inhibitors. Once AHA is diagnosed, the patient should be placed on immunosuppressive therapy comprising corticosteroids either alone or in combination with effective cytotoxic agents such as cyclophosphamide, cyclosporine, azathioprine or, more recently, rituximab. Through these therapeutic interventions, 70-80% of patients with AHA reportedly achieve complete remission (CR) [Blood. 2007;109:1870-1877]. Overshoot of FVIII activity after achieving CR has been known anecdotally in some AHA patients, but the details remain unclear.Patients and methods: CR was defined when the following criteria were met: resolution of hemorrhagic signs; FVIII activity >60 IU/dl; and negative results for FVIII inhibitor. We treated a total of 20 patients with AHA between January 2009 and December 2017 at Gunma University Hospital (GUH). Data from the 15 AHA patients (median age, 74 years; range, 30-87 years; 10 males) who achieved CR under immunosuppressive therapy were retrospectively analyzed. Overshoot of FVIII activity was defined as a level ³150 IU/dl. All patients provided written informed consent for review of their medical records. The institutional review board at GUH approved the study protocol.Results: Baseline AHA-related parameters are shown below. All 15 patients showed a prolonged APTT (median, 77.0 s; range, 63.4-124.7 s). FVIII activity had decreased to <10 IU/dl in all patients (median, 2.3 IU/dl; range, <1.0-8.0 IU/dl), and two patients were very deficient in FVIII (<1.0 IU/dl). Median titer of FVIII inhibitor was 13.0 BU/mL (range, 2.0-234 BU/ml). Eleven patients required therapy with bypassing agents. Hemostatic therapy was generally effective and no deaths due to bleeding events were encountered. All 15 patients achieved CR by immunosuppressive therapy primarily due to steroids, within a median of 39 days (range, 19-173 days). Overshoot was observed in 10 patients (66.7%), with maximum FVIII activity >200 IU/dl in 5 patients. Median duration from CR to overshoot was 17 days (range, 0-154 days). Venous thromboembolism as a severe complication caused by overshoot was observed in one patient, with a giant hematoma compressing the left iliac vein.Discussion and Conclusion: We have provided, here, the first report on the frequency of FVIII overshoot after CR in AHA patients, revealing a higher than expected frequency. Most AHA patients are elderly, relatively inactive and receiving steroid therapy, and so are a prime group for developing thromboembolism. Some patients have been reported to develop thrombosis during AHA treatment [Haemophilia. 2007;13:451-461]. In addition, high FVIII activity (>150 IU/dl) has been reported as a risk factor for venous thromboembolism [Lancet. 1995;345:152-155]. Overshoot of FVIII activity after CR may risk thromboembolism when combined with other thrombotic triggers. DisclosuresHanda:Takeda: Consultancy, Honoraria, Research Funding, Speakers Bureau; Celgene: Honoraria, Research Funding, Speakers Bureau.

Model of Short and Long-Term Outcomes of Emicizumab Prophylaxis Treatment for Persons with Hemophilia Α

Introduction: Persons with hemophilia A (PwHA) can experience bleeds that result in pain, disability, and a decrease in quality of life over time. Emicizumab is a Food and Drug Administration-approved bispecific antibody to factors IXa/X for prophylaxis of PwHA with inhibitors. Emicizumab was evaluated for the treatment of PwHA without inhibitors in the HAVEN 3 trial. However, its long-term impact is still unknown. This model aimed to estimate the lifetime clinical and economic outcomes of prophylaxis with emicizumab versus factor VIII (FVIII) replacement in persons with severe hemophilia A (HA).Methods: An Excel-based Markov model was developed to predict long-term clinical and economic outcomes associated with HA treatment options from the US societal perspective. In the model base-case, a hypothetical cohort of patients aged 1 year with severe HA without inhibitors were assigned to prophylaxis with emicizumab or FVIII. Patients in both arms could receive FVIII episodic treatment for breakthrough bleeds. In the model, patients could experience serious adverse events, develop FVIII inhibitors (based on FVIII exposure days), undergo immune therapy induction, develop arthropathy (conditional on number of joint bleeds and Pettersson score), and undergo orthopedic surgery (based on achieving a Pettersson score of 28). Indirect costs associated with productivity loss due to missed work or disabilities were also estimated and applied when patients would be in working age (18-65 years). Patients were assumed to receive life-long treatment. Model inputs were obtained from the HAVEN trials, published literature, and expert opinion. One-way sensitivity analysis was performed to assess inputs that were influential on the model outcomes. We report number of treated bleeds, mean age at inhibitor development, mean age at arthropathy onset, number of orthopedic surgeries, and total direct medical and indirect productivity costs. Outcomes are reported over 1 year, 5 years and lifetime time horizons. Cost results were inflation-adjusted to 2017 USD. Scenario analysis of moderate and severe PwHA was also performed.Results: The number of treated bleeds and joint bleeds was consistently lower for patients in the emicizumab arm across all time horizons (emicizumab vs. FVIII treated bleeds 1 year: 1.5 vs. 5.8; 5 years: 7.4 vs. 29.1; lifetime: 125.7 vs. 444.0; Joint bleeds 1 year: 1.1 vs. 3.6; 5 years: 5.4 vs. 17.8; lifetime: 92.2 vs. 273.3). Consequently, arthropathy onset (defined as Pettersson score ≥1) was postponed for patients receiving emicizumab versus FVIII prophylaxis (mean age at arthropathy onset: 12.9 vs. 5.4 years). Orthopedic surgeries were rare events in both emicizumab and FVIII arms (0.0 vs. 0.2). FVIII inhibitor development was also delayed in the emicizumab arm (mean age at inhibitor development: 13.9 vs. 1.1 years). Total cumulative direct and indirect costs were lower for emicizumab prophylaxis compared with FVIII prophylaxis for all time horizons (1 year: $97,127 vs. $312,020; 5 years: $603,057 vs. $1,281,059; lifetime: $15,373,443 vs. $20,134,246). Sensitivity analysis indicated that results were driven by drug list price, dosing schedule, and differences in efficacy rate. Results for moderate and severe PwHA were consistent with findings in the severe HA-only population.Conclusions: The model suggests that prophylaxis treatment of HA with emicizumab can result in a lower number of bleeding events as well as delayed onset of arthropathy and inhibitor development. Findings indicate that prophylaxis with emicizumab leads to better patient outcomes and has a lower financial impact from the US societal perspective. DisclosuresMahajerin:Genentech Inc.: Consultancy. Zhou:Analysis Group, Inc.: Employment; Celgene Corporation: Research Funding. Raimundo:Genentech Inc: Employment, Other: Ownership interests PLC. Patel:Genentech Inc: Employment. Han:Analysis Group Inc.: Research Funding. Ji:Analysis Group Inc.: Research Funding. Zhong:Analysis Group Inc.: Research Funding. Betts:Analysis Group Inc.: Research Funding.

Acquired hemophilia A presenting as progressive intra-abdominal hemorrhage, muscle hemorrhage and hemothorax postpartum: A case report and literature review.

Acquired hemophilia A (AHA) is a rare antibody-mediated condition in which autoantibodies form against a coagulation factor, most commonly factor VIII (FVIII), causing severe coagulopathy. Here the present report presents a case of AHA in a 35-year-old postpartum woman with continuous polyserous bloody effusions who was admitted to the First Affiliated Hospital of Zhejiang Chinese Medical University (Hangzhou, China) in October 2017 without a history of trauma, anticoagulation treatment or coagulopathy. At presentation, the patient's hemoglobin level was low (70 g/l; normal range: 115–150 g/l) g/l, blood pressure was 89/58 mmHg (normal range, 90–140/60–90 mmHg), and activated partial thromboplastin time was 68.4 sec (normal range: 25.0–36.0 sec), with a normal international normalized ratio (0.94; normal range, 0.8–1.2). The reaction time in thrombography was prolonged (35.8 min; normal range: 5–10 min), coagulation FVIII had markedly decreased activity (12.6%; normal range, 60–150%), and FVIII inhibitor had a high titer [7.4 Bethesda units (BU)/ml; normal range, 0–0.6 BU/ml]. Notably, the patient's autoantibody level was markedly higher than normal (1:320; normal range: <1:100). The patient was successfully treated with bleeding control, eradication of FVIII inhibitor, and treatment of the underlying disease. To the best of our knowledge, this is the first case of AHA with polyserous bloody effusions in a patient with an autoimmune disorder during the postpartum period. Reports of such rare cases will aid the characterization of disease pathogenesis, which may in turn lead to the recognition and timely treatment of this rare disorder.

A Novel Approach to Immune Tolerance Induction in Hemophilia Α with Factor VIII Inhibitor

Factor VIII (FVIII) inhibitors are currently the most significant complication of hemophilia A therapy. Immune tolerance induction (ITI) is the treatment of choice for inhibitor eradication. However, the optimal ITI regimen has not been identified. We describe an ITI approach for an adolescent male with severe hemophilia A and recurrent and refractory high-titer FVIII inhibitor. This strategy is now being tested in a randomized, controlled trial (NCT03204539).A 1-year-old white, Hispanic male with severe hemophilia A, intron 22 inversion, developed a FVIII inhibitor while receiving on-demand treatment with recombinant FVIII (rFVIII). Due to life-threatening bleeding despite bypassing agents, he was immediately started on ITI with daily rFVIII along with intravenous immunoglobulin (IVIg), solumedrol, and rituximab. He achieved tolerance after 15 months and was switched to every-other-day dosing for prophylaxis. Unfortunately, on prophylaxis he had breakthrough bleeding and inhibitor recurrence, and has required additional ITI regimens over the past 14 years (Table 1).Most recently, the family agreed to switch to Wilate® [von Willebrand Factor/Coagulation Factor VIII Complex (Human); Octapharma USA, Inc.; Hoboken, NJ; U.S. License No. 1646] as an alternative von Willebrand factor (VWF)/FVIII concentrate since he was unable to achieve tolerance on prior plasma-derived (pd) VWF/FVIII concentrate at 100 international units (IU)/kg daily for ~4 years. Wilate® was started when inhibitor titer was 1.5 Bethesda Units (BU). Initial FVIII recovery was 30% and 24-hour trough level was 1%. After several months, blood samples were sent to a diagnostic laboratory at Haemophilie-Zentrum Rhein Main GmbH for lot selection. Lot selection entails measuring residual FVIII activity when patient plasma is mixed with different lots of VWF/FVIII in vitro. This involves using the modified New Oxford method to measure residual FVIII activity after incubation of a FVIII source (lot) with the inhibitor patient plasma. The inhibitor titer is the reciprocal of the dilution of patient plasma that results in 50% of residual FVIII, similar to the Bethesda Unit. Ideally, the lot providing the highest residual FVIII activity will more effectively challenge the immune system, provide better prevention and control of bleeding, and have shorter time to tolerance. Investigators have demonstrated the utility of lot section in in vitro studies. The patient's plasma was tested against 6 lots of Wilate® and the lot with the lowest inhibitor activity was selected for prescription. This lot was allocated to this patient, and the prescribing physician included the lot number on the factor prescription for distribution to the patient via the patient's specialty pharmacy. The patient received Wilate® from the same lot for ~11 months. During that time, his inhibitor decreased from 2.6 BU to 0 after 5 months. A new plasma sample was tested against an additional 5 lots of Wilate®. Inhibitor was negative at that time and all lots of Wilate® revealed a negative inhibitory activity. One lot was selected for ongoing treatment. After 18 months his 48-hour trough FVIII level was detectable. He had blood drawn for pharmacokinetic analysis, which showed FVIII recovery of 55% and an estimated half-life of 6.75 hours. He was switched to every-other-day dosing and has had only one trauma-induced soft-tissue bleed despite increased physical activity, with negative inhibitor and a 48-hour trough of 2%. DisclosuresThornburg:Shire: Research Funding; CSL Behring: Research Funding; ATHN: Research Funding; Bayer Pharmaceuticals: Research Funding; Octapharma: Research Funding; Bioverativ: Consultancy; Genentech: Speakers Bureau; Biomarin: Consultancy; Bluebird Bio: Consultancy; NovoNordisk: Research Funding; Johns Hopkins All Children's Hospital: Research Funding. Ducore:OPKO: Other: investigator; HemaBiologics: Consultancy, Other: investigator, travel support; Shire: Consultancy, Other: travel support, investigator; Biomarin: Other: investigator; Octapharma: Consultancy, Other: travel support, investigator , Research Funding; Bayer Healthcare: Consultancy, Other: travel support, investigator; Pfizer: Other: investigator; Spark Therapeutics: Consultancy, Other: investigator; CSL Behring: Other: investigator.

Immune Tolerance Induction with Simoctocog Alfa (Nuwiq®) in Six Patients with Severe Haemophilia a and FVIII Inhibitors

Introduction and Objective: Inhibitors to coagulation factor VIII (FVIII) are the most serious complication of haemophilia A treatment. Previously untreated patients (PUPs) are at the greatest risk of inhibitors, which generally occur within the first 20 exposure days (ED) to FVIII. Immune tolerance induction (ITI) is the only clinically proven strategy for eradication of inhibitors. We present a case series of six PUPs with severe haemophilia A and inhibitors who underwent ITI with simoctocog alfa (Nuwiq®), a 4th generation human cell-line-derived recombinant FVIII approved for treatment of haemophilia A.Materials and Methods: Six male PUPs with severe haemophilia A who developed FVIII inhibitors after treatment with simoctocog alfa were started on ITI with simoctocog alfa. Primarily, we assessed the success of simoctocog alfa in patients with inhibitors. Success of ITI was determined based on undetectable inhibitor titre (< 0.6 BU/ml), FVIII recovery ≥ 66% and half-life ≥ 6 hours. Secondary objectives were to assess bleeding rate, tolerability and safety in patients with inhibitors treated with simoctocog alfa ITI.Results: The age of the patients at the start of ITI ranged from 8 to 186 months. Four of the patients were Caucasian, and two were African. All patients had a F8 mutation associated with high risk of ITI failure and two patients had an additional risk factor for ITI failure. The number of EDs prior to inhibitor development ranged from 9 to 33, and the peak inhibitor titre ranged from 0.9 to 114 BU. For ITI, five patients were treated with 100 IU/kg simoctocog alfa daily, and one with 90 IU/kg every other day. One patient achieved complete tolerisation and is now on prophylaxis at normal doses, having achieved an undetectable inhibitor titre after 9 months. This was despite an inhibitor titre ≥ 10 BU/mL at ITI start, which is considered a poor prognosis factor for ITI success. Three other patients achieved an undetectable inhibitor titre after 1, 6 and 18 months of ITI, and FVIII recovery has normalised but half-life remains short and they are on weaning doses as the half-life extends. One patient discontinued ITI with simoctocog alfa after 15 months due to an increasing inhibitor level. This patient was 15 years old at ITI start, and older age is associated with poor ITI outcome. Additionally, his haemophilia A was untreated for 15 years, during which time he developed severe arthropathy. One patient, who started ITI 3 months ago, has an ongoing inhibitor titre and continues on ITI with simoctocog alfa.Conclusions: In a case series of six patients treated with simoctocog alfa for ITI, who all had poor prognosis factors for ITI success, four patients (67%) to date have achieved an undetectable inhibitor titre. These data suggest that ITI with simoctocog alfa may be an effective treatment approach in haemophilia A patients with inhibitors. DisclosuresKhair:Shire, SOBI, Pfizer, Roche, Novo Nordisk, Octapharma: Speakers Bureau; shire, SOBI, Pfizer, Roche: Research Funding. Liesner:Roche: Research Funding; Novo Nordisk: Research Funding, Speakers Bureau; Baxalta: Consultancy, Research Funding; Bayer: Consultancy, Research Funding; Octapharma: Consultancy, Other: Clinical study investigator for NuProtect Study (Octapharma sponsored), Research Funding, Speakers Bureau; Sobi: Speakers Bureau. Belyanskaya:Octapharma AG: Employment.

Recombinant Porcine FVIII in Acquired Hemophilia: Decreased Product Usage When Used Upfront, Non-Utility of Baseline Porcine Bethesda Titer, and Confirmation of Dosing Algorithm

IntroductionAcquired hemophilia A (AHA) is a rare bleeding disorder in which acquired autoantibodies to endogenous Factor VIII (FVIII) decrease FVIII activity. AHA can lead to serious bleeding, with effective treatment requiring both immunosuppressive therapy (IST) and bypassing agents such as recombinant activated Factor VII (rFVIIa) or activated prothrombin complex concentrates (APCC). Disadvantages to bypassing agents include the inability to monitor response with standard lab assays, inconsistent hemostatic efficacy, and thrombosis (Astermark et al. 2007).Recombinant porcine FVIII (rpFVIII) ), by virtue of its incomplete homology in the A2 and C2 domains of the FVIII molecule, has decreased reactivity with anti-human FVIII (hFVIII) inhibitors (Mulliez et al. 2014), enabling its use in AHA. It also has the advantage of laboratory monitoring of FVIII activity levels and hemostatic efficacy after failure of bypassing agents (Trautmann-Grill et al. 2018).Between July 2015 and April 2018, 14 patients with AHA were treated with rpFVIII at the University of North Carolina. Data from our cohort show that the initial anti-porcine Bethesda titer (pBIA) does not reliably predict the clinical response to rpFVIII treatment and is not correlated with the anti-human Bethesda titer (hBIA). We also present data showing lower total rpFVIII use for initial bleed resolution when rpVIII is used up front, as compared to use as rescue therapy. Lastly, we validated our dosing algorithm which uses much lower than FDA-recommended doses with 10 more patients than in our previously reported patient series (Martin et al. 2016).MethodsWe analyzed clinical, pharmacy, and laboratory data from 14 patients treated with rpFVIII at the University of North Carolina for AHA from July 2015 to April 2018. All patients were initially treated according to our previously established dosing algorithm (Fig. 3). Investigational review board approval was obtained for our data collection and analysis.ResultsOf our 14 patients, 11 had a pBIA drawn prior to receiving rpFVIII, with 9/11 having a detectable porcine inhibitor, and only 2 of these showing no clinical response to rpFVIII infusion. There was no correlation between initial pBIA and FVIII response to rpFVIII infusion (Figs 1a-c). Only 2 patients lost their FVIII response and needed subsequent bypass agent use. One had a peak pBIA of 212 BU, and the other had a pBIA of 7, though 3 other patients who developed high titer pBIA did not lose their response. pBIA and hBIA showed poor correlation (r = 0.4, P = 0.2). 2/11 patients with available values had pBIA of <0.4, but had high titer hBIA.13/14 patients achieved excellent resolution of their presenting bleed at much lower than FDA-recommended doses (see Fig 1c and Table 1). In 12/14 patients, the inhibitor resolved after IST. rpFVIII was given as up front therapy in 6/14 patients (i.e., preceded by < 24 hours of bypassing agent), and they required less cumulative rpFVIII for resolution of the presenting bleed compared to the 8 patients given rpFVIII as rescue therapy (up front mean dose = 400 U/kg, rescue mean dose = 663 U/kg, P=0.06, see Fig 2).ConclusionOur data validate our previously established dosing algorithm, providing hemostatic efficacy at lower than FDA-approved doses, and allowing for rapid and standardized dosing adjustments based on laboratory and clinical response without delaying initial treatment. As the initial pBIA does not reliably predict response to rpFVIII, and is not correlated with the hBIA, our practice has been to initiate rpFVIII therapy without waiting for results of the pBIA. The pBIA can be useful in case of repeat bleeding events, though not in a predictable manner. Our data also suggest lower dose requirements when used up front, rather than as rescue therapy, which can also allow pharmacy cost savings. [Display omitted] DisclosuresKey:UniQure BV: Research Funding. Ma:CSL: Consultancy; Shire: Honoraria, Research Funding; Novo Nordisk: Consultancy; CVS: Honoraria.

Efficacy and Safety Results from a Phase 3b, Open-Label, Multicenter, Continuation Study of Rurioctocog Alfa Pegol for Prophylaxis in Previously Treated Patients with Severe Hemophilia A

Background: Patients with severe hemophilia A experience substantial morbidity and mortality due to frequent spontaneous and traumatic bleeding episodes, especially in joints. Prophylaxis with standard half-life factor VIII (FVIII) is the standard of care to prevent bleeds. Extended half-life products benefit patients by reducing the number of infusions without impacting the treatment efficacy.Methods: This phase 3b, prospective, open-label, multicenter, continuation study (NCT# 01945593) investigated the safety and efficacy of a PEGylated recombinant FVIII with an extended half-life, rurioctocog alfa pegol (SHP660, BAX 855, ADYNOVATE®, Shire, Lexington, MA, USA), for prophylaxis and treatment of bleeding in patients with severe hemophilia A (FVIII <1%). Eligible children and adults were ≤75 years of age and had either completed a previous rurioctocog alfa pegol study (NCT# 01599819, 01736475, 02210091, 02615691, 01913405, or 02585960) and were willing to immediately transition to the continuation study, or were naïve to rurioctocog alfa pegol but had received treatment with plasma-derived or recombinant FVIII for ≥150 (in patients ≥6 years of age) or ≥50 (in patients <6 years of age) exposure days. Patients received prophylactic rurioctocog alfa pegol at least twice weekly, either at a fixed dose (FD; 45 ± 5 IU/kg in patients ≥12 years of age; 50 ± 10 IU/kg in those <12 years of age; dose adjustment ≤80 ± 5 IU/kg allowed) or with pharmacokinetically (PK)-tailored dosing (≤80 ± 5 IU/kg) to maintain FVIII trough levels ≥3%. The co-primary endpoints assessed were the incidence of FVIII inhibitory antibody development (as measured by ≥0.6 BU in the Nijmegen modification of the Bethesda assay) and the spontaneous annualized bleed rate (ABR). Secondary endpoints included overall hemostatic efficacy ratings and occurrence of adverse events (AEs).Results: The study began in October 2013 and completed in March 2018. Overall, 216 patients receiving prophylaxis were eligible and included in the safety/full analysis dataset (≥1 dose received). Of these, 215 were male, the mean (SD) age at enrollment was 22.8 (15.7) years, the mean (SD) number of documented previous rurioctocog alfa pegol exposure days was 57.0 (39.6), the total ABR over 3-6 months prior to enrollment in the continuation study (including patients naïve to rurioctocog alfa pegol or receiving on-demand or prophylactic treatment with rurioctocog alfa pegol) was mean (SD) 4.7 (12.6), median (range) 0.0 (0-69). Most patients (206; 95.4%) had participated in a previous rurioctocog alfa pegol study. Overall, 215 patients received ≥1 dose in the FD regimen and 25 received ≥1 dose in the PK regimen. These patients received a mean (SD) of 1.72 (0.29) and 2.11 (0.61) prophylactic infusions per week, respectively, with a mean (SD) dose per infusion of 51.15 (8.11) IU/kg and 52.14 (17.03) IU/kg, respectively.None of the patients developed a confirmed FVIII inhibitor in this study and only 1 treatment-related allergic or hypersensitivity reaction (a nonserious mild AE) was reported. Nonserious AEs assessed by the investigators to be related to treatment occurred in 11/216 (5.1%) patients. Serious AEs (SAEs) occurred in 33 (15.3%) patients; there were no SAEs assessed by the investigators to be related to treatment. Descriptive statistics on spontaneous, joint, and total ABR by prophylactic regimen are shown in the Table. The overall total ABR in all patients was mean (SD) 2.5 (3.1), median (range) 1.6 (0.0-19.5). Overall hemostatic efficacy was rated as good or excellent in 88.5% of all bleeds and 89.4% of all bleeds were treated with 1 or 2 infusions.Conclusions: These results show that in previously treated patients with severe hemophilia A, rurioctocog alfa pegol prophylaxis in FD- and PK-tailored regimens was well tolerated and effective. None of the patients developed FVIII inhibitory antibodies, and a decrease in mean total ABR was reported in these patients compared with baseline. [Display omitted] DisclosuresMullins:Shire: Honoraria, Membership on an entity's Board of Directors or advisory committees. Konkle:Genentech: Consultancy; CSL Behring: Consultancy; Gilead: Consultancy; Pfizer: Research Funding; Spark: Consultancy, Research Funding; BioMarin: Consultancy; Bioverativ: Research Funding; Shire: Research Funding; Sangamo: Research Funding. McGuinn:CSL Behring: Consultancy; BioMarin: Consultancy; Bioverativ: Membership on an entity's Board of Directors or advisory committees, Research Funding; Spark: Consultancy, Research Funding; Genentech: Consultancy; Shire: Research Funding; Pfizer: Research Funding. Engl:Shire: Employment, Equity Ownership. Tangada:Shire: Employment, Equity Ownership.

The Un-BLyS-Ful State: Blocking Factor VIII Inhibitor Development with BLyS Depletion

The development of neutralizing alloantibodies (inhibitors) to infused factor VIII (FVIII) remains the most significant complication of therapy in hemophilia A (HA). Despite some insights into genetic and environmental risk factors associated with inhibitor development, the immunological mechanisms behind this complication remain incompletely understood. Given that infused FVIII is likely encountered in the periphery, transitional B cell response to FVIII may regulate inhibitor development. Transitional B cell survival, maturation and proliferation are tightly regulated by the cytokine BLyS (B-lymphocyte stimulator). Elevated levels of BLyS have been described in both auto- and allo-immune disease processes and may be genetically determined in a subset of patients with lupus and multiple sclerosis. In prior experiments, we noted that BLyS levels are higher in HA patients with inhibitors as opposed to 10 other pro- and anti-inflammatory cytokines. However, BLyS levels normalized amongst those who underwent successful immune tolerance induction. Thus, we hypothesized that BLyS may regulate FVIII inhibitor development or persistence. Here, we present results from animal studies aimed at 1) preventing inhibitor development in naïve HA mice and 2) maintaining long-term tolerance.For prevention experiments, HA C57Bl/6 mice (n=8-10/group) were given a single dose of anti-BLyS neutralizing antibody (Sandy-2, Adipogen) or PBS control one week prior to immunization with recombinant human FVIII (rhFVIII) at 80 IU/kg via tail vein injection every 14 days for four injections (Fig 1). Plasma samples were obtained at baseline and 7 days after last immunization and analyzed for FVIII antibody by Bethesda assay, anti-FVIII IgG by ELISA, and BLyS levels by ELISA. To test long-term tolerance, 22 weeks after initial anti-BLyS antibody injection, mice without inhibitors were challenged with 4 additional rhFVIII intravenous infusions and plasma obtained 7 days following each injection (Fig 1). Data was analyzed using Prism and is reported as median (IQR) with Mann-Whitney test for two-group comparisons and Mantel-Cox log-rank test for Kaplan-Meier survival analysis.Anti-BLyS treated mice achieved nadir BLyS levels at 14 days post-injection compared to control (0.2 [0.09-0.3] vs 8.2 [7.3-8.5] ng/ml, respectively, p < 0.0001), and levels equalized by day 28 between groups. Only 2 of 9 mice in the anti-BLyS treated group developed inhibitors to FVIII (0 [0-12.5] BU) compared to 9 of 10 in the treated group (21.1 [2.5-157.3] BU) with a significant log-rank survival of 0.0007 and favorable hazard ratio of 0.16 (95% CI 0.05-0.56) after initial immunization. Total anti-FVIII IgG was lower in the treated group (4.7 [1.1-11.5] mcg/ml) compared to control mice (27.6 [24-42] mcg/ml) with p of 0.003. Of the anti-BLyS treated inhibitor-free mice that have been challenged with rhFVIII, no inhibitors were detected until after the fourth rhFVIII injection. In these mice, there was a trend towards lower inhibitor titers compared to controls with a range of 1-1.8 BU vs. 85.6-1016 BU and lower FVIII IgG (23 [20.9-25.2] vs 69.9 [65.1-129.9] mcg/ml), respectively.Here, we demonstrate that BLyS depletion prior to FVIII exposure in naïve HA mice can prevent antibody development and may result in long-term sustained FVIII tolerance. As BLyS is central to the survival and maturation of transitional B cells, including marginal zone B cells which have recently been demonstrated to be important in inhibitor formation, this may provide a strategy for both antibody prevention and eradication in HA patients. Notably, the anti-BLyS monoclonal antibody belimumab is already FDA approved for the treatment of patients with lupus. Further studies to confirm the duration of immune tolerance obtained with anti-BLyS therapy in animal models may allow for translation of this strategy to provide long-lasting FVIII tolerance to patients with high risk of inhibitor development. [Display omitted] DisclosuresDoshi:Bayer Hemophilia Awards Program: Research Funding.

Efficacy and Safety of Bay 94-9027 Is Sustained for 5 Years: Outcomes in 33 Patients in the Protect VIII Extension Study

IntroductionBAY 94-9027 is a B-domain-deleted recombinant factor VIII (FVIII) that is site-specifically PEGylated with a 60-kDa (2 × 30-kDa) polyethylene glycol (PEG) to extend its half-life. The efficacy and safety of BAY 94-9027 as prophylactic and on-demand therapy for patients with severe hemophilia A were demonstrated in the phase II/III PROTECT VIII trial and its extension. We present an analysis of efficacy and safety outcomes in patients from PROTECT VIII who had completed at least 5 years of treatment as of 31 January 2018.MethodsPROTECT VIII was a partially randomized, open-label trial of 134 males aged 12-65 years with severe hemophilia A (FVIII < 1%) and ≥ 150 FVIII exposure days (ED). Prophylaxis patients received BAY 94-9027 25 IU/kg twice weekly for a 10-week run-in period. Patients with ≤ 1 spontaneous, joint or muscle bleed during this period were randomized to 45-60 IU/kg every 5 days (E5D) or 60 IU/kg every 7 days (E7D) for the main 26-week study period; patients enrolling after the randomization arms were full, or with ≥ 2 bleeds in the run-in period, received 30-40 IU/kg twice-weekly (2×W). Twenty patients received BAY 94-9027 on demand as they had been prior to study. Following completion of the main PROTECT VIII study, patients could enter an extension, continuing BAY 94-9027 on any regimen used in the main study; 121 patients entered the extension, of whom 107 were on the prophylactic arm. Prophylaxis patients who switched regimen after the first 7 days of being in the extension were analyzed in a combined variable frequency (VAR) group. Annualized bleeding rate (ABR) and joint ABR were analyzed, along with safety outcomes.ResultsAt the cut-off date, 33 patients had completed 5 years of treatment with BAY 94-9027 (2×W, n = 3; E5D, n = 10; E7D, n = 6; VAR, n = 14). Median number of infusions (range) was 363 (272-546), and median (range) annual factor consumption was 3385 (2732-5053) IU/kg. Median (range) ABR was 2 (0-15) in the full 5-year period, and 1 (0-12) for the final year. Corresponding joint ABRs were 1 (0-7) and 0 (0-7). Over the 5-year period, study drug-related adverse events (AE)s occurred in 6 patients (18.2%); no patients had a study drug-related serious AE. There were no discontinuations for AEs. No patients had confirmed FVIII inhibitors (titre ≥0.6 Bethesda units).ConclusionsThirty-three patients have received BAY 94-9027 prophylaxis for 5 years. The previously demonstrated efficacy of BAY 94-9027 was maintained across this period; in the last year of the extension median ABR was 1 and a third of patients were entirely free from bleeds. Consistent with the established safety profile of FVIII and with prior analyses of PROTECT VIII, there were few study drug-related AE and no evidence of any long-term toxicity of PEGylated product exposure. Taken together, these data support the use of BAY 94-9027 as a long-term treatment option for patients with hemophilia A. DisclosuresReding:Genentech: Other: Advisory Board. Hvitfeldt Poulsen:Primary investigator and national coordinator on clinical trials from Bayer Health Care: Other: Primary Investigator and national coordinator; Chaired an educational haemophilia symposium for nurses: Other: Chair; Nordic advisory boards (Bayer Health Care, Roche): Membership on an entity's Board of Directors or advisory committees; Lecturer on Nordic meeting on EHL FVIII (SOBI): Other: Lecturer . Tian:Bayer: Employment. Holme:Bayer, Biogen Idec, CSL Behring, Novo Nordisk, Pfizer, Shire and Sobi: Consultancy; Bayer, Octapharma, Pfizer and Shire: Research Funding.

A Phase 1/2 Trial of Investigational Spk-8011 in Hemophilia a Demonstrates Durable Expression and Prevention of Bleeds

A Phase 1/2 Trial of Investigational Spk-8011 in Hemophilia a Demonstrates Durable Expression and Prevention of Bleeds

Role of lupus anticoagulants in immediate acting inhibitor positivity in congenital haemophilia A patients

ObjectivesPresence of lupus anticoagulants (LA) in haemophilia and their interference in coagulation assays is well-known. Factor VIII (FVIII) inhibitors are generally time and temperature dependent whereas LAs are immediate acting inhibitors (IAIs). The present study reports the challenges in laboratory detection of both progressive and non-progressive, specific FVIII inhibitors in the presence of LA. MethodsFrom 2012 through 2015, 4900 HA patients were screened for inhibitors. APTT based inhibitor screening tests and Nijmegen-modified Bethesda assay (NBA) were done in all samples. LA test and FVIII inhibitors by ELISA were done in patients with IAIs. ResultsOut of 451 patients positive for inhibitors in the initial screening tests, classical and progressive FVIII inhibitors were observed in 398 patients while 53 had IAIs showing no/partial correction in 1:1 mixtures of NPP and patient plasma. In 27 patients, both FVIII and FIX activity levels were <1%, resulting in difficulty in diagnosis. In 48 HA patients with IAIs, 42 were LA positive. 4 patients were found to have only LA with false positive results in NBA while 38 had a combination of LA and FVIII inhibitors. Six patients were LA negative and had only FVIII IAIs. Five (62.5%) of 8 HA patients initiated on immune tolerance induction (ITI) also were positive for IAIs. ConclusionThe findings emphasizes the presence of specific FVIII inhibitors in congenital HA with absence of time dependent inactivation kinetics in a small proportion of cases. ELISA or chromogenic assays along with LA testing can offer accurate laboratory diagnosis in patients with coexisting LA.

Bleeding events and safety outcomes in persons with haemophilia A with inhibitors: A prospective, multi‐centre, non‐interventional study

Prospectively collected, real-world data on bleeds, haemophilic treatment and safety outcomes in persons with haemophilia A (PwHA) with factor VIII (FVIII) inhibitors are limited. A prospective, global, multi-centre, non-interventional study (NIS; NCT02476942) collected detailed real-world data in PwHA treated per local routine clinical practice. To characterize bleeding rates, haemophilic treatment practices, prophylaxis adherence and adverse events (AEs) in adult/adolescent PwHA with inhibitors in the NIS. Participants aged ≥12years with congenital haemophilia A/documented high-titre FVIII inhibitor history were enrolled. Participants remained on their usual treatment; no interventions were applied. Overall, 103 PwHA with inhibitors enrolled, (median [range] age 31 [12-75] years) and were monitored for median (range) 26.0 (4.1-69.6) weeks. In the episodic (n=75) and prophylactic (n=28) treatment groups, respectively, 1244 and 325 bleeds were reported, and 528 (42.4%) and 104 (32.0%) were not treated; annualized bleeding rates (ABRs; 95% confidence interval) were 18.6 (15.2-22.8) and 14.9 (10.5-21.2) for treated bleeds, and 32.7 (27.3-39.1) and 25.0 (18.4-34.0) for all bleeds. Coagulation products used included activated prothrombin complex concentrate (aPCC) and/or recombinant activated FVII. Among participants prescribed aPCC prophylaxis, 35.0% adhered to both prescribed frequency of aPCC administration and prescribed dose. Serious AEs of haemarthrosis and muscle haemorrhage were reported; most common AEs were arthralgia, viral upper respiratory tract infection and pyrexia. ABRs (treated bleeds and all bleeds) remain high on standard treatment; this prospective NIS demonstrates the need for more effective treatments for PwHA with inhibitors to reduce/prevent bleeds, with potential to improve prophylaxis adherence and further improve outcomes.

Distinguishing lupus anticoagulants from factor VIII inhibitors in haemophilic and non-haemophilic patients.

Accurate diagnosis of an inhibitor, a neutralizing antibody to infused factor VIII (FVIII), is essential for appropriate management of haemophilia A (HA). Low-titre inhibitors may be difficult to diagnose due to high rates of false-positive inhibitor results in that range. Transient low-titre inhibitors and false-positive inhibitors may be due to the presence of a lupus anticoagulant (LA) or other non-specific antibodies. Fluorescence immunoassay (FLI) to detect antibodies to FVIII is a sensitive method to identify inhibitors in HA. Evaluations of antibody profiles by various groups have demonstrated that haemophilic inhibitors detected by Nijmegen-Bethesda (NBA) and chromogenic Bethesda (CBA) assays correlate with positivity for anti-FVIII immunoglobulin (Ig) G1 and G4. This study sought to determine whether FLI could distinguish false-positive FVIII inhibitor results related to LAs from clinically relevant FVIII inhibitors in HA patients. Samples from haemophilic and non-haemophilic subjects were tested for LA, specific FVIII inhibitors by NBA and CBA, and anti-FVIII immunoglobulin profiles by FLI. No samples from LA-positive non-haemophilic subjects were positive by FLI for anti-FVIII IgG4. Conversely, 91% of NBA-positive samples from haemophilia subjects were positive for anti-FVIII IgG4. Two of 11 haemophilia subjects had samples negative for anti-FVIII IgG4 and CBA, which likely represented LA rather than FVIII inhibitor presence. Assessment of anti-FVIII profiles along with the CBA may be useful to distinguish a clinically relevant low-titre FVIII inhibitor from a transient LA in HA patients.

Prophylactic bypassing agent use before and during immune tolerance induction in patients with haemophilia A and inhibitors to FVIII.

The development of high-titre inhibitory antibodies (inhibitors) against factor VIII (FVIII) remains a challenge in the management of patients with haemophilia A (HA). Patients with high-titre inhibitors are more likely to experience uncontrolled bleeding, physical disability from chronic arthropathy and premature death compared with those without this complication. Immune tolerance induction (ITI), utilizing repeated infusions of FVIII, is an effective therapeutic approach to eliminating inhibitory antibodies. This strategy can eradicate FVIII inhibitors, so that FVIII-specific tolerance is induced. However, patients undergoing ITI are still vulnerable to the development of serious and/or repeated bleeding events. The efficacy of bypassing agents in preventing bleeding episodes has been widely proven in patients with HA and inhibitors to FVIII. Evidence suggests that reducing bleeding during ITI can also shorten the time to tolerance. There are concerns with the use of bypassing agents, including the cost of treatment, short half-life, management of non-responders and the risk of thrombosis. Despite these concerns, and the still limited evidence from prospective studies and consensus reports, the use of prophylaxis with bypassing agents during ITI has been gaining support. This review presents a rationale and current data supporting the use of prophylactic bypassing agents as effective and safe therapies to reduce the incidence of joint bleeding due to inhibitors and improve quality of life in patients with HA undergoing ITI.

Optimization of pre-analytical heat treatment for inhibitor detection in haemophilia A.

Factor VIII (FVIII) antibody formation is the greatest clinical and laboratory challenge within the haemophilia centre. The Nijmegen-Bethesda assay (NBA) is the gold standard for inhibitor quantification, but affected by pre-analytical variables including a patient's FVIII activity (FVIII:C). Pre-analytical heat treatment (PHT) provides a methodology for inhibitor testing when measurable FVIII:C is present. We evaluated the effect of different PHT conditions (time/temperature) on FVIII:C as well as on potency of inhibitory activity in samples containing FVIII:C (endogenous pooled plasma and exogenous recombinant FVIII (rFL-FVIII) concentrate) or FVIII inhibitor. PHT of endogenous FVIII at 37°C, 47°C and 52°C resulted in declining measurable FVIII:C at 120minutes (69%, 57% and 13% of the original FVIII:C, respectively). Incubation at 56°C resulted in FVIII:C≤1IU/dL after 60minutes for endogenous FVIII and 120minutes for rFL-FVIII. Incubation at 58°C resulted in FVIII:C<1IU/dL at 15-30minutes for endogenous FVIII and at 30-60minutes for rFL-FVIII. No difference was seen for inhibitor detection following PHT (56°C or 58°C) by NBA or anti-FVIII IgG ELISA. PHT at 58°C for 30minutes demonstrated consistent reduction in FVIII:C<1IU/dL without appearing to affect inhibitor detection. Laboratory awareness of differences in thermostability of different sources of FVIII is important when choosing PHT conditions.

Factor VIII manufactured from plasma—the ups and downs, and the up again: a personal journey—part 1: history of the development of plasma-derived factor VIII therapies

The history of the treatment of haemophilia is a success story. Despite the setbacks posed by the viral transmission epidemics, by the mid-1980s the safety of products from blood-borne pathogens was all but assured. Scientific understanding of the way in which factor VIII (FVIII) behaves in different separation processes led to the development of increasingly pure and potent preparations from plasma. In the late 1980s, the first products from recombinant technology unleashed a 13-year-old flood of technological innovation leading to the current generation of molecularly modified improved products. The capacity to produce FVIII independently from the blood and plasma donation system has also led to the potential of unlimited supply and the attainment of treatment for all the global population of people with haemophilia. Despite these developments, FVIII concentrates derived from human plasma continue to represent an important sector of the market, with a relatively strong presence in the emerging economies. Recent studies indicate that some plasma-derived FVIII (pd-FVIII), at least those containing von Willebrand factor, may offer some therapeutic advantages relative to recombinant products, particularly in the area of FVIII inhibitors. In this, first part, of my personal journey in FVIII, I will review the history of this product.

Effects of pre-analytical heat treatment in factor VIII (FVIII) inhibitor assays on FVIII antibody levels.

The use of pre-analytical heat treatment (PHT) with the Nijmegen-Bethesda assay (NBA) for inhibitors to factor VIII (FVIII) can remove/destroy infused or endogenous FVIII from patient plasma samples, allowing testing of recently infused patients with haemophilia. Two PHT methods have been described as follows: heating to 56°C for 30minutes and heating to 58°C for 90minutes. Data examining the effects of PHT on anti-FVIII IgG4 , the antibodies known to correlate most closely with the presence of FVIII inhibitors, are limited. To assess the effect of PHT on the levels of detectable anti-FVIII IgG4 . Nijmegen-Bethesda assay-positive specimens were incubated at 56, 58 or 60°C for 90minutes, and anti-FVIII IgG4 was measured by fluorescence immunoassay (FLI) at 30-minute intervals. The effects of PHT on the ability of recombinant FVIII (rFVIII) to inhibit detection of patient antibodies by FLI was also examined to assess the stability of rFVIII under the various PHT conditions tested. Levels of anti-FVIII IgG4 showed little change following incubations at 56°C (mean 101% of original value at 30minutes and 100% at 60minutes) but decreased upon exposure to 58°C (mean 85% at 30minutes and 66% at 60minutes). In addition, heating to 56°C effectively decreased the ability of rFVIII to block antibody binding compared to unheated rFVIII. The optimal temperature for PHT in the FVIII NBA is 56°C. Higher temperatures may lead to loss of inhibitory antibodies.

A prospective surveillance study of inhibitor development in haemophilia A patients following a population switch to a third-generation B-domain-deleted recombinant factor VIII.

Following a provincial tender, most subjects with haemophilia A in Quebec switched their treatment to a third-generation recombinant B-domain-deleted factor VIII (FVIII). Our objective was to evaluate the incidence of inhibitor development and FVIII recovery in patients following the switch of factor replacement therapy. One hundred and thirty-five subjects were enrolled and tested for FVIII activity and inhibitors every 6months during 1year. Subjects with mild haemophilia A or current inhibitors were excluded. Data on demographics, bleeds and FVIII usage were collected. A total of 125 switchers and 10 non-switchers were enrolled. Most subjects had severe haemophilia A (95.6%) and were on prophylaxis (89.6%). Mean FVIII recovery was similar at 0, 6 and 12months postswitch. Two switchers developed de novo inhibitors in the 6months postswitch, one of which was transient. No recurrent inhibitor was observed. A small but significant increase in FVIII usage was observed for adult switchers and the whole cohort of switchers and non-switchers. There was an increase in the annualized bleeding rate (ABR) for non-joint bleeds for the whole cohort of switchers. However, no significant differences were observed in ABR for joint bleeds. Our surveillance study shows comparable inhibitor development to similar published studies. A significant increase in FVIII utilization was noted for the whole cohort, switchers and non-switchers. Lastly, no clinically significant changes were observed in ABR for joint bleeds, but a difference for non-joint bleed ABRs was observed in switchers.

Low incidence of factor VIII inhibitors in previously untreated patients with severe haemophilia A treated with octanate® : Final report from a prospective study.

Octanate® is a human, plasma-derived, von Willebrand factor-stabilized coagulation factor VIII (FVIII) concentrate with demonstrated haemostatic efficacy in previously treated patients with haemophilia A. This prospective, open-label study aimed to assess the immunogenicity of octanate® in previously untreated patients (PUPs). The study monitored development of FVIII inhibitors in 51 PUPs. Tolerability, viral safety, FVIII recovery and efficacy of octanate® for the prevention and treatment of bleeds and in surgical procedures were also assessed. Five (9.8%) of the 51 patients developed inhibitors during the study, 4 of which (7.8%) were high titre. Three inhibitor cases (5.9%) were considered clinically relevant; 2 were transient inhibitors that disappeared during regular octanate® treatment without a change in dose or treatment frequency. Amongst 45 patients with FVIII:C <1% at baseline and who received ≥20 exposure days (EDs) or had <20 EDs but developed an inhibitor, inhibitor incidence was 11.1% (6.7% clinically relevant). All clinically relevant inhibitors developed within 20EDs of on-demand treatment. No inhibitors developed in PUPs receiving prophylaxis. All patients who developed inhibitors had either intron 22 inversions or large deletions. Irrespective of the reason for administration, haemostatic efficacy was rated as "excellent" in 99.6% of all infusions (4700 of 4717 infusions), and no complications were reported in 23 surgical procedures. Mean incremental in vivo recovery was 2.0%/IU/kg (±0.7) and 1.9%/IU/kg (±0.5) for the first and second assessments, respectively. Tolerability was rated "very good" in 99.9% of infusions. In PUPs with severe haemophilia A, octanate® demonstrated haemostatic efficacy with a low rate of inhibitor development.