Background Prophylaxis with a von Willebrand factor (VWF) concentrate is recommended in von Willebrand disease (VWD) patients with a history of frequent and severe bleeds. Despite nosebleeds being a frequent manifestation of VWD, few studies have investigated the efficacy of factor prophylaxis in preventing nosebleeds in patients with severe VWD. Methods This post-hoc analysis of a prospective, 12-month, phase 3 study assessed the efficacy of wilate in the prevention of nosebleeds in 33 patients aged ≥6 years with severe type 1, type 2 or type 3 VWD. All patients previously participated in a 6-month prospective study of on-demand treatment with any VWF concentrate. Prophylactic efficacy was assessed by comparing total and spontaneous annualized bleeding rates for nosebleeds (TABR and SABR, respectively) during prophylaxis with rates during on-demand treatment. Results The mean TABR and SABR for nosebleeds were reduced by 76% and 81% respectively during prophylaxis versus on-demand treatment (2.7 vs 11.0 and 2.1 vs 10.9). During the second 6 months of prophylaxis, mean TABR was 49% lower and mean SABR 57% lower versus the first 6 months. The percentage of patients with zero nosebleeds was 19% during 6 months of on-demand treatment, 55% during the first 6 months of prophylaxis, and 68% during the second 6 months of prophylaxis. The efficacy of wilate in the treatment of breakthrough nosebleeds was rated excellent in 99% of cases. Conclusion This post-hoc analysis demonstrated the efficacy of wilate prophylaxis in the prevention and treatment of nosebleeds in children and adults with severe VWD.

Long-term prophylaxis with a von Willebrand factor (VWF) concentrate is recommended in patients with von Willebrand disease (VWD) who have a history of severe and frequent bleeds. However, data from prospective studies are scarce. WIL-31, a prospective, noncontrolled, international phase 3 trial, investigated the ef ficacy and safety of Wilate prophylaxis in severe patients with VWD. Male and female patients 6 years or older with VWD types 1, 2 (except 2N), or 3 who had completed a prospective, 6-month, on-demand, run -in study (WIL-29) were eligible to receive Wilate prophylaxis for 12 months. At baseline, patients (n = 33) had a median age of 18 years. Six (18%) patients had severe type 1, 5 (15%) had type 2, and 22 (67%) had type 3 VWD. The primary end point of a >50% reduction in mean total annualized bleeding rate (TABR) with Wilate prophylaxis vs prior on-demand treatment was met; mean TABR during prophylaxis was 5.2, representing an 84.4% reduction. The bleeding reduction was consistent across age, sex, and VWD types. The mean spontaneous ABR was 3.2, representing an 86.9% reduction vs on-demand treatment. During prophylaxis, 10 (30.3%) patients had 0 bleeding events and 15 (45.5%) patients had 0 spontaneous bleeding events. Of 173 BEs, 84.4% were minor and 69.9% treated. No serious adverse events related to study treatment and no thrombotic events were recorded. Overall, WIL-31 showed that Wilate prophylaxis was ef ficacious and well-tolerated in pediatric and adult patients with VWD of all types. The WIL-29 and WIL-31 trials were registered at www.ClinicalTrials.gov as #NCT04053699 and #NCT04052698, respectively.

Background: The use of a von Willebrand factor (VWF) concentrate for long-term prophylaxis is recommended for individuals with von Willebrand disease (VWD) who have a history of frequent and severe bleeds, regardless of their age or the type of VWD. Bleeding from the nose (epistaxis) is one of the most common types of bleeding in VWD patients. The WIL-31 study demonstrated the efficacy of prophylaxis with a plasma-derived VWF/factor VIII (pdVWF/FVIII) concentrate containing VWF and FVIII in a 1:1 activity ratio (wilate ®) in adults and children with VWD of all types. The primary endpoint was met, showing a decrease of 84% in the mean total annualized bleeding rate (ABR) compared with prior on-demand treatment. Aims: To investigate the efficacy of regular prophylaxis with a pdVWF/FVIII concentrate in reducing nose bleeds in people with VWD, compared with previous on-demand treatment. Methods: WIL-31 (NCT04052698) was a prospective, non-controlled, international, multicenter phase 3 trial that enrolled male/female patients, aged ≥6 years with VWD type 1 (VWF:RCo <30 IU/dL), type 2 (except 2N) or type 3. Prior to entering the WIL-31 study, all patients had received on-demand treatment with a VWF-containing product during a 6-month, prospective, observational, run-in study (WIL-29); patients who experienced at least 6 bleeding episodes, excluding menstrual bleeds, of which ≥2 were treated with a VWF-containing product, were eligible to enter WIL-31. Patients in WIL-31 received regular prophylaxis with pdVWF/FVIII 2-3 times per week at a dose of 20-40 IU/kg for 12 months. In this post-hoc analysis, nose bleeds during WIL-29/-31 were described, and the mean ABRs were compared. Results: The study population included 33 patients with a median (range) age of 18 (7-61) years; 9 (27.3%) patients were 6-11 years old, 6 (18.2%) were 12-16 years old, and 18 (54.5%) were ≥17 years old. All VWD types were represented: type 1 (n=6), type 2 (n=5); and type 3 (n=22). There were 173 breakthrough bleeds in total during WIL-31, of which nose bleeds were the most common (89/173; 51.4%). Nose bleeds occurred in 16 of 33 patients during prophylaxis vs 26 of 33 during on-demand treatment. Of the 89 nose bleeds, 17 were traumatic, 69 spontaneous, and 3 due to allergic reaction (not product related). The mean number of spontaneous nose bleeds per patient during prophylaxis was 2.1, 2.3, 1.2, and 2.2, for the overall population, and the 6-11, 12-16, and ≥17 years age groups, respectively. Eight nose bleeds (9.0%) were major (all in the same patient). The mean nose ABR was reduced by 76% during prophylaxis vs on-demand treatment. The reduction was consistent across age groups (74-77%, Figure 1) but not across VWD types, with mean nose ABR reductions of 48, 89, and 80% for VWD type 1, type 2, and type 3 patients, respectively. During prophylaxis, a higher number of VWD type 3 patients, compared with type 1 and type 2 patients, experienced nose bleeds (12 vs 3 vs 1). The mean duration of nose bleeds decreased during prophylaxis vs on-demand for 12-17 years old, ≥17 years old, type 2 and type 3 VWD patients, but increased for 6-11 years old and severe type 1 patients. No relationship was observed between the number of nose bleeds and patient age (R 2=0.082). The majority (80.9%; 72/89) of nose bleeds were treated with pdVWF/FVIII with 86.1% (62/72) requiring only a single infusion; two required concomitant treatment with tranexamic acid. All treated nose bleeds were rated as “successfully treated”. Conclusion: The data indicate thatprophylaxis with pdVWF/FVIII was effective at reducing nose bleeds in patients with VWD type 2 and 3, and across all age groups.

BACKGROUND:The NuProtect study reported data on the immunogenicity, efficacy and tolerability of simoctocog alfa (Nuwiq® ) in 108 previously untreated patients with severe haemophilia A planned to be treated for ≥100 exposure days or up to 5 years. The NuProtect-Extension study collected long-term prophylaxis data in children with severe haemophilia A.METHODS:Patients who completed the NuProtect study according to the protocol were eligible for the NuProtect-Extension study, a prospective, multinational, non-controlled, Phase 3b study.RESULTS:Of 48 patients who entered the extension study, 47 (median age 2.8 years) received prophylaxis with simoctocog alfa for a median of 24 months, with 82%-88% on a twice-weekly or less regimen. No patient developed FVIII inhibitors during the extension study. The median (IQR) annualized bleeding rate (ABR) during prophylaxis was 0 (0-0.5) for spontaneous bleeding episodes (BEs) and 1.00 (0-1.95) for all BEs. ABRs estimated using a negative binomial model were .28 (95% CI: .15, .53) for spontaneous and 1.62 (95% CI: 1.09, 2.42) for all BEs. During the median follow-up of 24 months, 34 (72%) patients had zero spontaneous BEs and 46 (98%) had zero spontaneous joint BEs. Efficacy in treating BEs was excellent or good for 78.2% of rated BEs, and efficacy of surgical prophylaxis was excellent for two rated surgeries. No treatment-related adverse events were reported.CONCLUSION:No FVIII inhibitors developed during long-term prophylaxis in the NuProtect-Extension study. Prophylaxis with simoctocog alfa was efficacious and well-tolerated, and is therefore an attractive long-term option for children with severe haemophilia A.

Background: Prophylaxis with von Willebrand factor (VWF) concentrate is recommended for individuals with von Willebrand disease (VWD) who have a history of frequent and severe bleeds, regardless of their age. The WIL-31 study demonstrated the efficacy of prophylaxis with a plasma-derived VWF/factor VIII (pdVWF/FVIII) concentrate containing VWF and FVIII in a 1:1 activity ratio (wilate ®) in adults and children with VWD of all types. Here we specifically report on the results in children and adolescents. Aims: To investigate the efficacy and safety of regular prophylaxis with a pdVWF/FVIII concentrate in children and adolescents with VWD, compared with prior on-demand treatment. Methods: WIL-31 (NCT04052698) was a prospective, non-controlled, international, multicenter phase 3 trial that enrolled male/female patients aged ≥6 years with VWD type 1 (VWF:RCo <30 IU/dL), type 2 (except 2N) or type 3. Prior to entering the WIL-31 study, all patients had received on-demand treatment with a pdVWF/FVIII concentrate during a 6-month, prospective, observational, run-in study (WIL-29); patients who experienced at least 6 BEs, excluding menstrual bleeds, with at least 2 of these BEs treated with a VWF-containing product, were eligible to enter WIL-31. Patients in WIL-31 received regular pdVWF/FVIII prophylaxis 2-3 times per week at a dose of 20-40 IU/kg for 12 months. In this post-hoc analysis patients were grouped by age: children (6-11 years old), adolescents (12-16 years old), and adults (≥17 years old). Mean total and spontaneous ABR were compared, and the number and site of breakthrough bleeds were described. Safety and tolerability were assessed throughout the study. Results: The study population included 33 patients, with a median (range) age of 18 (7-61) years. Nine (27.3%) patients were children, 6 (18.2%) were adolescents, and 18 (54.5%) were adults. During 12 months of prophylaxis, 67% (6/9) of children and 83% (5/6) of adolescents experienced 34 (all minor) and 26 bleeds (20 minor; 6 major), respectively. Among children and adolescents, 82% (28/34) and 77% (20/26) of bleeds required treatment, with “excellent/good” efficacy achieved in 100% and 95% of treated bleeds, respectively. The mean total ABRs during on-demand vs prophylaxis were 32.5 vs 3.7 in children and 28.9 vs 4.3 in adolescents, representing 88.6% and 85.1% reductions during prophylaxis compared with on-demand treatment. Of these bleeds, the most common sites were nose (74%; 25/34) and oral cavity (9%; 3/34) for children, and nose (46%; 12/26), ankle (23%; 6/26) and elbow (19%; 5/26) joints for adolescents. During prophylaxis children experienced no joint bleeds; the mean knee, ankle, and elbow joint ABRs in adolescents were 0.2, 1.0, and 0.8, respectively. The mean spontaneous ABRs during on-demand treatment vs prophylaxis were 22.8 vs 2.5 (88.9% reduction) and 21.7 vs 1.5 (93.2% reduction) (Figure 1). Forty-four percent of children, and 33% of adolescents had zero spontaneous bleeding events during 12 months of prophylaxis. No serious adverse events related to study treatment and no thrombotic events were observed, and no safety concerns were raised by clinical laboratory, vital sign, and physical examination findings. There were no cases of parvovirus B19 seroconversion or inhibitor development judged to be related to study treatment. Conclusion: Prophylaxis with pdVWF/FVIII was efficacious and well tolerated in children and adolescents with all types of VWD.

Introduction Simoctocog alfa (Nuwiq (R)) is a 4th generation recombinant FVIII with proven efficacy for the prevention and treatment of bleeding episodes (BEs) in previously treated patients with severe haemophilia A. The NuProtect study assessed the immunogenicity, efficacy and safety of simoctocog alfa in 108 previously untreated patients (PUPs). The incidence of high-titre inhibitors was 16.2% and no patients with non-null F8 mutations developed inhibitors.Aim To report the efficacy and safety results from the NuProtect study.Methods PUPs received simoctocog alfa for prophylaxis, treatment of BEs, or as surgical prophylaxis. The efficacy of prophylaxis (during inhibitor-free periods) was assessed using annualised bleeding rates (ABRs). The efficacy in treating BEs and in surgical prophylaxis was assessed using a 4-point scale. Adverse events were recorded throughout the study.Results Of 108 PUPs treated with simoctocog alfa, 103 received at least one prophylactic dose and 50 received continuous prophylaxis for at least 24 weeks. In patients on continuous prophylaxis, the median ABR was 0 (mean 0.5) for spontaneous BEs and 2.5 (mean 3.6) for all BEs. In 85 patients who had BEs, efficacy of BE treatment was excellent or good for 92.9% (747/804) of rated BEs; 92.3% of BEs were treated with 1 or 2 infusions. The efficacy of surgical prophylaxis was excellent or good for 94.7% (18/19) of rated procedures. There were no safety concerns and no thromboembolic events.Conclusion Simoctocog alfa was efficacious and well tolerated as prophylaxis, surgical prophylaxis and for the treatment of BEs in PUPs with severe haemophilia A.

Background: Heavy menstrual bleeding (HMB) is the dominant symptom affecting ~80-90% of women with VWD and is a common cause of outpatient visits and hospitalizations. Long-term prophylaxis with a von Willebrand factor (VWF) concentrate is recommended in von Willebrand disease (VWD) patients with a history of severe, frequent bleeds, and for women with VWD who experience HMB. A recent prospective study found that recombinant VWF was not superior to tranexamic acid at reducing HMB in women with VWD. The WIL-31 study demonstrated the efficacy of prophylaxis with a plasma-derived VWF/factor VIII (pdVWF/FVIII) concentrate containing VWF and FVIII in a 1:1 activity ratio (wilate ®) in adults and children with VWD of all types. The primary endpoint was met, showing a decrease of 84% in the mean total annualized bleeding rate (ABR) compared with prior on-demand treatment. The impact of pdVWF/FVIII prophylaxis on HMB was evaluated as a secondary endpoint of the WIL-31 study. Aims: To investigate the efficacy of regular prophylaxis with a pdVWF/FVIII concentrate in reducing the incidence of HMB in females with VWD who had previously been treated on demand. Methods: WIL-31 (NCT04052698) was a prospective, non-controlled, international, multicenter phase 3 trial that enrolled male/female patients, aged ≥6 years old with VWD type 1 (VWF:RCo <30 IU/dL), type 2 (except 2N) or type 3. Prior to entering the WIL-31 study, all patients had received on-demand treatment with a VWF-containing product during a 6-month, prospective, observational, run-in study (WIL-29). Patients in WIL-31 received regular pdVWF/FVIII prophylaxis 2-3 times per week at a dose of 20-40 IU/kg for 12 months. Exploratory analyses included comparison of heavy menstrual ABR (HMABR). HMB was defined as any menstrual bleed that impeded the ability to perform daily activities (such as work, housework, exercise, or social activities) during menstrual periods. Criteria for HMB included changing pads more frequently than hourly, menstrual bleeding lasting 7 or more days, or the presence of clots >1 cm combined with a history of flooding or a Pictorial Blood Assessment Chart (PBAC) score ≥185. PBAC scores were reviewed from patient diaries at each study visit. Results: Of the 33 patients included in the overall population, 14 (42%) were female and half (n=7; 13-43 years old) were of childbearing age. In these females, all VWD types were represented: type 1 (n=2), type 2 (n=1); and type 3 (n=4). Six (86%) females were on hormonal birth control during WIL-31. Prophylaxis with pdVWF/FVIII reduced the mean HMABR by 64% compared with on-demand treatment (3.0 vs 8.3 in WIL-31 and WIL-29, respectively). During on-demand treatment, 86% (6/7) of females experienced ≥1 HMB episode, which was reduced to 29% (2/7) during prophylaxis with four patients experiencing no HMB (Figure 1). During on-demand treatment, 6 females experienced 32 HMB episodes; of these, 7 (22%) required further treatment with pdVWF/FVIII and 2 (6%) required concomitant medication. Under prophylaxis, two patients (aged ≥17 years), experienced 12 HMBEs; of these, only one (8%) impeded daily activity and none required additional pdVWF/FVIII treatment, hospitalization, or concomitant medication. Mean (SD) intra-individual median PBAC scores (N=4) decreased by 43% from 227 (91.7) during on-demand treatment to 131 (59.9) with prophylaxis, a 96-point reduction. Conclusion: Prophylaxis with pdVWF/FVIII was efficacious in reducing HMB compared with on-demand treatment in 7 female patients with VWD. None of the cases of HMB during prophylaxis was severe enough to require additional treatment. Among women with VWD, HMB remains a major burden and further research is required.

Introduction: Long-term prophylaxis with a von Willebrand factor (VWF) concentrate is recommended in von Willebrand disease (VWD) patients with a history of severe and frequent bleeds, regardless of age or VWD type. Data on the efficacy and safety of prophylaxis with a human plasma-derived VWF/factor VIII concentrate (pdVWF/FVIII; wilate®) that contains the two factors in a physiological 1:1 activity ratio have been collected previously from 19 VWD patients in four prospective, multicenter phase 2 and 3 trials. In these patients, bleeding rates were significantly reduced compared with previous treatment. Aims: To investigate the efficacy and safety of regular prophylaxis with a pdVWF/FVIII concentratein previously treated patients with VWD. Methods: WIL-31 (NCT04052698) was a prospective, non-controlled, international, multicenter phase 3 trial that enrolled patients of any gender with VWD type 1 (VWF:RCo <30 IU/dL), type 2 (except 2N) or type 3, who were at least 6 years old. Prior to entering the WIL-31 study, all patients had received on-demand treatment with pdVWF/FVIII during a 6-month, prospective, observational, run-in study (WIL-29); patients who experienced at least 6 bleeding episodes (BEs), excluding menstrual bleeds, with at least 2 of these BEs treated with a VWF-containing product, were eligible to enter WIL-31. Patients in WIL-31 received regular pdVWF/FVIIIprophylaxis, 2-3 times per week at a dose of 20-40 IU/kg, for 12 months. The primary endpoint of the study was to demonstrate that prophylaxis with pdVWF/FVIII lowered the mean total annualized bleeding rate (ABR) compared with that during 6 months of on-demand treatment by more than 50%. Secondary outcomes included spontaneous ABR and treatment-emergent adverse events. Results: Thirty-three patients were included in the modified full analysis set, with a median (range) age of 18 years (7-61). Fourteen (42.4%) patients were female, 9 (27.3%) patients were <12 years old. Six (18.2%) patients had severe Type 1 VWD, 7 (21.2%) had type 2, and 20 (60.6%) patients had type 3 VWD. Mean (median, range) total ABR in the on-demand run-in period and during pdVWF/FVIII prophylaxis was 33.4 (24.5, 11-115) and 5.2 (1.9, 0-35.8), respectively (Figure 1), meeting the primary endpoint of a ≥50% reduction in mean ABR. Mean (median, range) spontaneous ABR in the on-demand run-in period and during pdVWF/FVIII prophylaxis was 24.4 (18.7, 5-93) and 3.2 (1.0, 0-24.6), respectively. Of the 33 patients, 10 (30.3%) and 15 (45.5%) patients had zero total or spontaneous BEs during the study period, respectively. A total of 173 BEs occurred, the majority of which (146 BEs; 84.4%) were classified as minor. Of the 173 BEs, 121 (69.9%) were treated with pdVWF/FVIII. The overall efficacy of treatment was assessed as "excellent” or "good” for 120 (99.2%) BEs and "moderate” for 1 (0.8%) BE. Five serious adverse events were reported, none of which were assessed as related to the study treatment. Two patients had adverse events assessed as probably or possibly related to the study treatment by the investigator, and both patients discontinued from the study. One patient developed mild chest tightness (3 events), the other had hypersensitivity reactions of moderate severity (2 events). No thrombotic events occurred. Conclusions: Prophylaxis with a pdVWF/FVIII containing VWF and FVIII in a 1:1 activity ratio was effective in pediatric and adult patients with VWD of all types. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

INTRODUCTION:FVIII inhibitor development is the most serious contemporary treatment complication in haemophilia A, particularly in previously untreated patients (PUPs). No inhibitors developed in clinical trials in previously treated patients treated with simoctocog alfa (Nuwiq), a fourth-generation recombinant FVIII produced in a human cell line. METHODS:The NuProtect study investigated the immunogenicity of simoctocog alfa in PUPs. NuProtect was a prospective, multinational, open-label, non-controlled, phase III study. PUPs with severe haemophilia A (FVIII:C <1%) of any age and ethnicity were treated with simoctocog alfa for 100 exposure days or a maximum of 5 years. Patients were true PUPs without prior exposure to FVIII concentrates or blood components. Inhibitor titres were measured with the Nijmegen-modified Bethesda assay; cut-off for positivity was 0.6 BU mL-1 (≥0.6 to <5 low-titre, ≥5 high titre). RESULTS:A total of 108 PUPs with a median age at first treatment of 12.0 months (interquartile range: 8.0-23.5) were treated with simoctocog alfa. F8 mutation type was known for 102 patients (94.4%) of whom 90 (88.2%) had null F8 mutations and 12 (11.8%) had non-null mutations. Of 105 PUPs evaluable for inhibitor development, 28 (26.7%) developed inhibitors; 17 high titre (16.2%) and 11 low titre (10.5%). No PUPs with non-null F8 mutations developed inhibitors. CONCLUSION:In the NuProtect study, the rate of inhibitor development in PUPs with severe haemophilia A treated with simoctocog alfa was lower than the rate reported for hamster-cell-derived recombinant factor VIII products in other recent clinical trials. No inhibitors were reported in PUPs with non-null F8 mutations.

Abstract Background Studies have shown that the incidence of inhibitor development varies between FVIII concentrates, with some suggesting that recombinant FVIII (rFVIII) concentrates produced in hamster cell lines pose a greater risk of inhibitor development than plasma-derived (pd) von Willebrand factor (VWF)-containing FVIII (pdFVIII/VWF) products. In the SIPPET study, the cumulative incidence of high-titer inhibitorswith hamster-cell derived rFVIII products was 28.4% vs 18.6% for pdFVIII/VWF (Peyvandi F et al. N Engl J Med 2016; 374:2054-2064). These studies did not include new generation rFVIII products produced in human cell lines. Nuwiq® (Human-cl rFVIII) is the first and only new-generation rFVIII produced in human cells without chemical modification or protein fusion. The pharmacokinetics, efficacy and safety of Nuwiq® have been examined in previously treated patients (PTPs) with severe hemophilia A, and no inhibitors have been reported in 201 PTPs. The immunogenicity, efficacy and safety of Nuwiq® in previously untreated patients (PUPs) with severe hemophilia A is currently being assessed in the ongoing NuProtect study. Methods The NuProtect study was initiated in 2013 and is being conducted in 17 countries and 38 centers worldwide. One hundred evaluable (110 enrolled) male PUPs of all ages and ethnicities are being studied for 100 exposure days (EDs) or a maximum study participation of 5 years. The patients were to have received no treatment with FVIII concentrates or other blood products containing FVIII prior to study entry. The primary objective of the NuProtect study is to assess the immunogenicity of Nuwiq® by determining inhibitor activity (≥0.6 BU) using the Nijmegen modified Bethesda assay in a central laboratory. Intensive screening for inhibitors is scheduled every 3-4 EDs until 20 EDs, then every 10-12 EDs until 100 EDs, and every 3 months until study completion. Secondary endpoints include assessment of hemostatic efficacy in prophylaxis, in the treatment of bleeds and in surgical prophylaxis, as well as safety and tolerability. All patients undergo F8 gene mutation analysis. Results Data from 85 treated PUPs have been included in the first pre-planned interim analysis (May 2016) of which 66 PUPs had ≥20 EDs (by which time the majority of inhibitors are likely to have arisen). The median age at first treatment was 13 months (range: 3-135). Of the 59 patients with available F8 gene mutation analysis, 1 (1.7%) had no identifiable mutation, 44 (74.6%) had mutations conferring a high risk of inhibitor development and 47 (81.0%) had null mutations. Data analysis in May 2016 showed that only 8 of the 66 PUPs treated with Nuwiq® for ≥20 EDs had developed a high-titer inhibitor after a median of 11.5 EDs (range 6-24). Five of the 66 PUPs developed a low-titer inhibitor, 4 (80%) of which were transient. Only 2 patients developed an inhibitor (1 high-titer) after 20 EDs. The cumulative incidence of high-titer inhibitors in PUPs treated with Nuwiq® is 12.8% (95% CI: 4.49-21.15) (Figure 1). The cumulative incidence of low-titer inhibitors was 8.4% (95% CI: 1.28-15.59) and of all inhibitors was 20.8% (95% CI: 10.68-30.95). No patient developed an inhibitor after 25 EDs. The incidence has remained consistent since the start of the study in 2013. Twelve of 13 patients who developed inhibitors had the causative F8 gene mutation detected, all of which were null, and all but one were high-risk. Conclusions PUPs treated with Nuwiq® for ≥20 EDs had 12.8% cumulative incidence of high-titer inhibitorsat the time of interim analysis (8 of 66 PUPs) despite the fact that 81% of patients had gene mutations known to be associated with increased inhibitor risk (e.g. null mutations). These interim data support the low rate of inhibitor development in PUPs treated with Nuwiq® - a human-cell derived (not chemically modified or protein fused) recombinant FVIII. Final data from the NuProtect study are expected in 2018 and will provide further insights into the development of inhibitors in PUPs with severe hemophilia A. Figure 1. Cumulative incidence of inhibitor development Figure 1. Cumulative incidence of inhibitor development Disclosures Liesner: CSL Behring: Consultancy, Honoraria, Research Funding; Biogen: Consultancy, Honoraria, Research Funding; Pfizer: Consultancy, Honoraria, Research Funding; SOBI: Consultancy, Honoraria, Research Funding, Speakers Bureau; Octapharma: Consultancy, Honoraria, Research Funding, Speakers Bureau; BPL: Consultancy, Honoraria, Research Funding; Bayer: Consultancy, Honoraria, Speakers Bureau; Cangene: Research Funding; Baxalta Innovations GmbH, now a part of Shire: Consultancy, Honoraria, Research Funding; Grifols: Consultancy, Honoraria. Altisent:Baxalta: Consultancy, Research Funding; Bayer: Consultancy, Research Funding; Novo Nordisk: Consultancy, Research Funding; Grifols: Consultancy; Pfizer: Consultancy, Research Funding; CSL Behring: Consultancy, Research Funding; Octapharma: Consultancy. Belletrutti:Shire Pharmaceuticals (formerly Baxalta): Membership on an entity's Board of Directors or advisory committees, Other: Travel support, Research Funding; Bayer: Membership on an entity's Board of Directors or advisory committees, Research Funding; Octapharma: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Travel support, Research Funding; NovoNordisk: Other: Travel support. Borel-Derlon:LFB: Other: Reference expert and national coordinator for VWD; Shire - Baxalta: Research Funding; Octapharma: Research Funding; NovoNordisk: Other: Expert for scientific committee. Ducore:CSL Behring: Membership on an entity's Board of Directors or advisory committees; Biogen: Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees; LFB: Membership on an entity's Board of Directors or advisory committees; Octapharama: Membership on an entity's Board of Directors or advisory committees; Baxalta (Shire): Membership on an entity's Board of Directors or advisory committees; Bayer: Membership on an entity's Board of Directors or advisory committees. Sigaud:Shire - Baxalta: Honoraria, Membership on an entity's Board of Directors or advisory committees.