Non-Compartment and compartmental pharmacokinetics, efficacy, and safety of Kedrion FIX concentrate.

BACKGROUND: An open-label phase II, multicenter clinical trial was conducted at 11  Haemophilia Centres in  Italy, Romania, and Turkey, to evaluate the pharmacokinetics (PK), efficacy, and safety of high purity, plasma-derived, double virus inactivated and double nano-filtered factor IX (pd-FIX) concentrate (Kedrion FIX), EudraCT Number: 2005-006186-14. MATERIAL AND METHODS: 16 previously treated patients (PTPs) with severe or moderately severe haemophilia B were enrolled in the study. At enrolment, 14 underwent the first PK assessment (PK I), and the second PK (PK II) assessment was performed after six months of treatment (5 on-demand and nine prophylaxis) at the end of the study. PK parameters were evaluated by Non-Compartmental Analysis (NCA), One-Compartment model (OCM), and Two-Compartment Model (TCM). Efficacy of Kedrion FIX in all 16 patients was evaluated by the number of bleeding events, and clinical response following the infusions. Periodic FIX inhibitor assays and thrombogenicity tests were scheduled throughout the study to assess the safety of the drug. RESULTS: As compared to the published data on PK of pdFIX, Kedrion FIX displayed a longer half-life (22.37-55.73 hrs), reduced clearance, and regular volume of distribution at PK I by both NCA and OCM. The comparison of outcomes of PK II with those of PK I by OCM,  also showed significant changes, particularly in patients on prophylaxis, who showed some improved parameters of PK. Due to two outlier values at the end of the trial, the NCA parameters of PK I were not compared to those of PK II. Breakthrough bleeds were successfully treated with 1 or 2 infusions. No significant adverse events were observed during the study. DISCUSSION: During the six-month clinical study period, the use of Kedrion FIX resulted in a safe and effective pd-FIX concentrate with excellent PK characteristics.

Common themes and challenges in hemophilia care: a multinational perspective.

OBJECTIVE: To identify ways that provision of hemophilia care can be maximized at the local level, irrespective of available resources or cultural or geographic challenges. METHODS: The SHIELD group used its multinational experience to share examples of local initiatives that have been employed to deliver optimal hemophilia care. RESULTS: The examples were reviewed and categorized into four key themes: guidelines and algorithms for delivery of care; collaboration with patients and allied groups for care and education; registries for the monitoring of treatment and outcomes and health care planning and delivery; and opportunities for personalization of care. These themes were then incorporated into a road map for collaborative care in hemophilia that reflected the contribution of best practice. DISCUSSION: Differing healthcare reimbursement systems, budgetary constraints, and geographical and cultural factors make it difficult for any country to fully deliver ideal care for people with hemophilia. The SHIELD approach for collaborative care provides illustrative examples of how four key themes can be used to optimize hemophilia care in any setting. ABBREVIATIONS: AHCDC: Association of Hemophilia Clinic Directors of Canada; AICE: Italian Association of Hemophilia Centres; ATHN: American Thrombosis and Hemostasis Network; EAHAD: European Association for Haemophilia and Allied Disorders; EHC: European Hemophilia Consortium; FIX: Coagulation Factor IX; FVIII: Coagulation Factor VIII; HAL: Haemophilia Activity List; HJHS: Haemophilia Joint Health Score; HTC: Hemophilia Treatment Centre; HTCCNC: Hemophilia Treatment Centre Collaborative Network of China; MASAC: Medical and Scientific Advisory Council; MDT: Multidisciplinary team; NHD: National Haemophilia Database; NHF: National Hemophilia Foundation; PK: Pharmacokinetics; POCUS: Point of care ultrasound; PWH: People with haemophilia; SHIELD: Supporting Hemophilia through International Education, Learning and Development; WFH: World Federation of Hemophilia.

Muscle function deterioration in patients with haemophilia: Prospective experience from Costa Rica.

INTRODUCTION: In haemophilia, recurrent joint bleeds are responsible for the development of chronic joint damage, because blood induces biochemical changes in joint structures. Joint degeneration is a long process, and structural damage is often preceded by joint dysfunction, which is represented by quantitative and qualitative changes in the contraction pattern of muscles around the joints. Muscle function in patients with haemophilia is still poorly investigated. AIM: The aim of this 2-year prospective study was to assess the changes in muscle function of lower limbs in a group of patients affected with haemophilia in San José, Costa Rica. METHODS: Muscle function of lower limbs was assessed by means of surface electromyography (sEMG) accomplished at study enrolment and after 2 years of follow-up. Gluteus medius, vastus medialis, biceps femoris, gastrocnemius and tibialis anterior were examined. All patients underwent concurrent clinical examination using Haemophilia Joint Health Score (HJHS). RESULTS: Sixty patients aged 2-43 years with severe haemophilia underwent clinical and sEMG evaluation. Thirty-two patients (53%) had target joints. sEMG parameters were altered in all patients and were not correlated to the presence of target joints and/or an abnormal HJHS. Muscle function deterioration was observed after 2 years of follow-up despite an unmodified HJHS. CONCLUSIONS: Muscle function of lower limbs as detected by means of sEMG was impaired in patients with haemophilia irrespective of the presence of overt joint damage. sEMG is a simple and sensitive assessment tool able to detect muscle dysfunction and so favouring the implementation of early rehabilitation therapy.

Ageing successfully with haemophilia: A multidisciplinary programme.

INTRODUCTION: Persons with haemophilia (PWH) born before the middle 1970s have spent a substantial part of their lives without the benefits of replacement therapy, that became available on a relative large scale only during the 1970s. As a consequence, this group of PWH, although still relatively young, suffers from musculoskeletal and functional problems that are typical of old people. METHODS: We report herewith the short-term results of a project based upon a multidisciplinary training programme led by a physiotherapist and an occupational therapist, that was implemented over a period of 12 months in 40 patients with severe or moderate hemophilia A or B born before the middle 1970s and regularly followed-up at a comprehensive haemophilia treatment centre in Italy. The project was aimed to provide information and skills in order to empower the older PWH carrying physical handicaps and functional limitations that had resulted from the inadequate management in their early ages, and to enable them to cope more efficiently with their crippling disease and prevent further disabilities. RESULTS AND CONCLUSIONS: The comparison of the data obtained before and after the 12-month programme found marginal improvements, but the purpose of this programme was indeed to offer a blueprint for the future. In this respect, the level of satisfaction for the programme was very high and we expect that it will be implemented long-term by our older PWH.

Involvement of the IgE-basophil system and mild complement activation in haemophilia B with anti-factor IX neutralizing antibodies and anaphylaxis.

INTRODUCTION: Patients with haemophilia B who develop factor IX (FIX) neutralizing antibodies (inhibitors) after FIX infusion are at high risk of hypersensitivity reactions upon FIX re-exposure, but the underlying mechanisms are incompletely understood. AIM: To investigate biomechanisms of FIX hypersensitivity. METHODS: A cellular antigen stimulation test (CAST) was employed to evaluate leukotriene C4 (LTC4) release from basophils stimulated by FIX in three treated children with haemophilia B, one of whom developed FIX inhibitor and experienced anaphylaxis following FIX re-exposure. Anti-FIX IgE and IgG antibodies and markers of complement activation (C5b9, C3d and iC3b) were measured in plasma, the last also after FIX infusion. Ten healthy children served as controls. RESULTS: The patient who developed anti-FIX inhibitors and anaphylaxis had a nonsense mutation in FIX gene (p.Arg298Stop) and, compared to controls, had higher plasma levels of specific anti-FIX IgE (2.285 vs 0.084 OD492 nm ), with marked LTC4 release from his FIX-stimulated basophils (519.8 vs 39.9 pg/mL). Further, he had higher plasma levels of anti-FIX IgG of all the four subclasses (total IgG 1.180 vs 0.120 OD492 nm ) with FIX neutralizing activity (1.5 BU); mild complement activation occurred during FIX-induced anaphylaxis (C5b9 increased from 258.5 to 351.1 ng/mL). The same parameters were normal in the two patients who tolerated FIX infusion. CONCLUSION: In the patient with haemophilia B who experienced anaphylaxis after FIX, but not in the patients with haemophilia B who tolerated FIX, the CAST assay showed FIX-induced LTC4 release, which was associated with high plasma levels of specific anti-FIX IgE and IgG antibodies.

Low-factor consumption for major surgery in haemophilia B with long-acting recombinant glycoPEGylated factor IX.

INTRODUCTION: Surgery in patients with haemophilia B carries a high risk of excessive bleeding and requires adequate haemostatic control until wound healing. Nonacog beta pegol, a long-acting recombinant glycoPEGylated factor IX (FIX), was used in the perioperative management of patients undergoing major surgery. AIM: To evaluate the efficacy and safety of nonacog beta pegol in patients with haemophilia B who undergo major surgery. METHODS: This was an open-label, multicentre, non-controlled surgery trial aimed at assessing peri- and postoperative efficacy and safety of nonacog beta pegol in 13 previously treated patients with haemophilia B. All patients received a preoperative nonacog beta pegol bolus injection of 80 IU kg-1 . Postoperatively, the patients received fixed nonacog beta pegol doses of 40 IU kg-1 , repeated at the investigator's discretion. Safety assessments included monitoring of immunogenicity and adverse events. RESULTS: Intraoperative haemostatic effect was rated 'excellent' or 'good' in all 13 cases. Apart from the preoperative injection, none of the patients needed additional doses of nonacog beta pegol on the day of surgery. The median number of postoperative doses of nonacog beta pegol was 2.0 from days 1 to 6 and 1.5 from days 7 to 13. No unexpected intra- or postoperative complications were observed including deaths or thromboembolic events. No patients developed inhibitors. CONCLUSIONS: These results indicated that nonacog beta pegol was safe and effective in the perioperative setting, allowing major surgical interventions in patients with haemophilia B with minimal peri- and postoperative concentrate consumption and infrequent injections as reported with standard FIX products.

Evaluation of the utility of the ISTH-BAT in haemophilia carriers: a multinational study.

INTRODUCTION: There has been increasing recognition in recent years that female carriers of haemophilia manifest abnormal bleeding; however, data on the use of bleeding assessment tools in this population are lacking. AIM: Our objective was to validate the ISTH-BAT in haemophilia carriers to describe bleeding symptoms and allow for comparisons with factor levels and other patient groups. METHODS: This was a prospective, observational, cross-sectional study performed by members of Global Emerging HEmostasis Panel (GEHEP). Unselected consecutive haemophilia carriers were recruited and a CRF and the ISTH-BAT were completed by study personnel. RESULTS: A total of 168 haemophilia carriers were enrolled: 155 haemophilia A and 13 haemophilia B. The mean age was 40 years (range: 20-82). Carriers had higher mean bleeding scores (BS) compared with age-matched controls (n = 46; 5.7 vs. 1.43; P < 0.0001) and Type 3 VWD OC (n = 32; 3.0; P = 0.009), but lower BS compared with women with Type 1 VWD (n = 83; 8.7; P < 0.0001). Fifteen carriers reported haemarthrosis, and of those six had normal FVIII/FIX levels. There was a significant but weak negative correlation between BS and factor level (Spearman's r2  = -0.36, P < 0.001). CONCLUSION: Our results show that haemophilia carriers experience abnormal bleeding, including haemarthrosis. Overall, BS in women with Type 1 VWD > haemophilia carriers > Type 3 VWD OC > controls. Understanding the performance of the ISTH-BAT in this population is a critical step in future research aimed at investigating the underlying pathophysiology of abnormal bleeding, with the ultimate goal of optimizing treatment.

Tailoring hemostatic therapies to lower inhibitor development in previously untreated patients with severe hemophilia A.

After technological progress provided safer therapeutic products for patients with hemophilia A, the development of alloantibodies (inhibitors) neutralizing the coagulant activity of infused factor VIII (FVIII) remains the most serious complication of replacement therapy, predisposing patients to greater morbidity and causing higher treatment costs. The pathogenesis of inhibitors, which develop at a high rate in previously untreated children with severe hemophilia A, is multifactorial, resulting from complex interactions between genetic and environmental factors. Among non-genetic determinants, a key role is played by treatment-related factors, including the source of FVIII product (i.e., plasma derived or recombinant) and the mode of replacement therapy delivery (i.e., intensity, prophylaxis vs. on demand). We review the potential interventions on these modifiable factors that may help to lower the rate of inhibitor development. In addition, interest is currently directed toward the potential for lesser immunogenicity of novel hemostatic agents designed to decrease the dosing frequency or avoid/delay the need of FVIII replacement therapy.

The thrombin generation assay distinguishes inhibitor from non-inhibitor patients with severe haemophilia A.

INTRODUCTION: Patients with haemophilia A (HA) have impaired thrombin generation (TG) capacity and TG assay (TGA) values are linearly related to plasma factor VIII (FVIII) levels. AIM: This study carried out in patients with unmeasurable FVIII (<1 IU dL(-1) ) was aimed at unravelling any difference in TG capacity in patients with or without inhibitors. METHODS: Blood samples were collected from patients in a non-bleeding state, after a 5-day wash-out period from last treatment. RESULTS: TGA was performed in 102 patients with severe HA (15% with high-responding inhibitors; 51% with null F8 mutations, that as expected were more prevalent in inhibitor than in non-inhibitor patients). TG capacity was significantly lower in inhibitor than non-inhibitor patients and in those with null mutations than in those with non-null mutations. When the TG capacity was evaluated only in patients with null mutations with and without inhibitors it was lower in the presence of inhibitors. CONCLUSIONS: This study shows a greater TG impairment in inhibitor patients irrespective of FVIII levels, inhibitor titre and F8 mutation type, suggesting a role for the TGA in unravelling functional interferences of anti-FVIII inhibitors on coagulation system activation.

Low thrombin generation during major orthopaedic surgery fails to predict the bleeding risk in inhibitor patients treated with bypassing agents.

INTRODUCTION: In the presence of high-titre inhibitors, haemostatic bypassing agents are used to control bleeding and perform surgery. In this setting, no specific laboratory test is yet available to guide drug choice, monitor treatment efficacy and predict the risk of bleeding. AIM: The aims of this study, carried out in patients candidate to orthopaedic surgery, were to assess the dose-dependent increase in thrombin generation (TG) after infusion of bypassing agents and to evaluate whether or not a correlation existed between the haemostatic efficacy of bypassing therapies and perioperative TG values. METHODS AND RESULTS: TG was measured in 16 inhibitor patients, 10 of whom underwent 11 major orthopaedic procedures. In the non-bleeding state, TG significantly improved 30 min after whichever dose (P < 0.01), with no dose-response relationship when values obtained after different rFVIIa doses were compared. TG significantly improved 30 min after the preoperative bolus (P < 0.05), while during the postoperative period TG values measured before and after dosing did not differ. Moreover, postoperative TG values were similar or even more impaired (P ≤ 0.05) than those measured before preoperative dosing. No difference was found by comparing procedures with and without bleeding complications and yet no bleeding occurred in spite of persistently low TG values in one-third of procedures. CONCLUSION: This study fails to support a definite role for the TG assay as a reliable laboratory tool to monitor the haemostatic efficacy of bypassing therapies and as a predictor of the risk of bleeding in inhibitor patients using these agents during orthopaedic surgery.

BAY 81-8973 safety and efficacy for prophylaxis and treatment of bleeds in previously treated children with severe haemophilia A: results of the LEOPOLD Kids Trial.

INTRODUCTION: BAY 81-8973, a full-length, unmodified, recombinant factor VIII (FVIII) in development for treatment of haemophilia A, has the same primary amino acid sequence as Bayer's sucrose-formulated recombinant FVIII but is produced with more advanced manufacturing technologies. AIM: To demonstrate safety and efficacy of BAY 81-8973 for prophylaxis and treatment of bleeds in previously treated children. METHODS: In this phase III, multicentre, open-label, nonrandomized study, boys aged ≤12 years with severe haemophilia A and ≥50 exposure days (EDs) to FVIII products received prophylaxis with BAY 81-8973 25-50 IU kg(-1) ≥2 times weekly for ≥50 EDs. The efficacy endpoint was annualized number of total bleeds. Adverse events (AEs) and immunogenicity were assessed. RESULTS: Fifty-one patients were treated (age: <6 years, n = 25; 6-<12 years, n = 26) with a 2× per week (43%) or >2× per week (57%) regimen at study start. Median [quartile 1; quartile 3 (Q1; Q3)] annualized number of bleeds for the combined age groups was 1.90 (0; 6.02) for total bleeds, 0 (0; 2.01) for joint bleeds and 0 (0; 0) for spontaneous bleeds. Median (Q1; Q3) annualized number of total bleeds within 48 h of previous prophylaxis infusion was 1.88 (0; 3.97) for children aged <6 years and 0 (0; 1.96) for children aged 6-<12 years. No drug-related serious AEs or inhibitors were reported. CONCLUSIONS: Prophylaxis with BAY 81-8973 using individualized prophylaxis regimens of 2× per week, 3× per week and every-other-day infusions was efficacious in prevention and treatment of bleeds in children with severe haemophilia A. Treatment with BAY 81-8973 was well tolerated.

Central venous access device (CVAD) complications in Haemophilia with inhibitors undergoing immune tolerance induction: Lessons from the international immune tolerance study.

INTRODUCTION: Central venous access devices (CVADs) are frequently required as stable long-lasting venous access in children with haemophilia, especially those requiring immune tolerance induction (ITI) for inhibitors. CVAD infection is one of the most frequently reported catheter-related complications in this patient population. AIM: Detailed review of CVAD complications from the International ITI (I-ITI) study and analysis of potential risk factors for such complications. METHODS: Retrospective analysis of prospectively obtained data from the I-ITI study primarily focused on CVAD-related complications. RESULTS: A total of 115 children were recruited and 183 CVADs were placed in 99 subjects resulting in 121,206 CVAD-days observed on-study. A total of 124 CVAD infections were reported in 41 of 99 (41%) subjects with an overall infection rate of 0.94 per 1000 CVAD-days (interquartile ranges 0-1.7). A similar number of infections were observed in the two treatment arms (median: 2 and 3 in high dose and low dose respectively). Infections occurred more frequently in the presence of external catheters than with fully implanted catheters (P = 0.026). Infected patients were significantly younger at the time of CVAD insertion (median age: 22 vs. 25 months, P = 0.020). Patients with Gram-positive infections were also significantly younger than those with Gram-negative infections (median age: 17 vs. 25 months, P < 0.0001). CONCLUSION: CVAD infection was the most common complication observed in children with severe haemophilia and inhibitors in the frame of the I-ITI study. Younger age at CVAD insertion and external CVAD were associated with higher risk for infection. ITI outcome was unaffected by CVAD infections.

Presentation and management of acute coronary syndromes among adult persons with haemophilia: results of an international, retrospective, 10-year survey.

Sparse data are available on presentation and management of acute coronary syndromes (ACS), including unstable angina and non-ST- and ST-elevation myocardial infarction, among persons with haemophilia (PWH). The aim of this study was to determine demographics, bleeding disorder characteristics, cardiovascular risk factors (CRFs), interventions, haemostatic protocol, revascularization outcomes and complications among PWH with ACS. Members of an international consortium comprising >2000 adult PWH retrospectively completed case report forms for episodes of ACS in a >10-year follow-up period (2003-2013). Twenty ACS episodes occurred among 19 patients [rate, 0.8% (95% CI 0.4, 1.2)]. Seven patients (37%) were aged <50 years; 10 (53%) had ≥3 CRFs. In 5/20 episodes (25%), the initial ACS management protocol was altered because of the bleeding disorder. None of the eight patients with severe haemophilia underwent coronary artery bypass grafting (CABG), compared with 54.5% of patients with non-severe disease (P = 0.02). Revascularization with percutaneous coronary intervention (PCI) or CABG was rated successful in 13/13 cases, with no excessive bleeding during initial management. During chronic exposure to antiplatelet agents, secondary haemophilia prophylaxis was more prevalent in patients with severe haemophilia compared with non-severe haemophilia (85.7% vs. 30%, P = 0.05). No ACS-related deaths occurred during initial management, but one patient with severe haemophilia A died of undetermined cause 36 months after the ACS event while on aspirin therapy. ACS occurs even among relatively younger PWH, typically in association with multiple CRFs. Revascularization with PCI/CABG is feasible, and antiplatelet agents plus secondary prophylaxis appears to be well tolerated in selected PWH with ACS.

Factors influencing illness representations and perceived adherence in haemophilic patients: a pilot study.

Illness representations of chronic patients are important to explain adherence and preventive behaviours. However, it is unclear if the patient's objective health status may influence illness representations and perceived adherence. This study explored if health status and socio-demographic characteristics influence illness representations and perceived adherence in haemophilic patients. Fifty patients (25 on-demand and 25 on prophylaxis) ageing from 13-73, completed the Illness Perceptions Questionnaire-Revised and the Morisky Medication Adherence Scale. Patients' cognitive illness representations were influenced by type of treatment, haemophilia severity, presence of inhibitor and co-morbidity. Perceived chronicity was influenced by patient's age (P = 0.021). Perceived adherence was not influenced by the health status, but was affected by the relationship status (P = 0.048). Perceived adherence was predicted by perceived chronicity (ß = 0.412; P = 0.003) and by emotions (ß = -0.308; P = 0.023). Patient's health status seems to affect cognitive illness representations but not perceived adherence. Perceived chronicity and negative emotions, which affected perceived adherence, were not influenced by the health status. Physician-patient communication addressing perceived chronicity and emotions rather than patients' health status may influence patient's adherence. Psycho-educational groups could be offered to promote patient's well-being and adjustment to haemophilia, and improve adherence.

Integrated postural analysis in children with haemophilia.

The maintenance of a correct posture in haemophilic boys might contribute to prevent joint bleeds, chronic pain and dysfunction. This single-centre study was aimed at evaluating whether or not postural alterations are more common in haemophilic than in non-haemophilic boys and whether they are related to the orthopaedic status. Posture and balance were investigated in boys with severe/moderate haemophilia (cases) and in age-matched non-haemophilic peers (controls). Thirty-five cases (89% with haemophilia A: 74% with severe disease) were included in the study and compared with 57 controls. Posture was evaluated on digital pictures of anterior, lateral and posterior views of the habitual standing position. Balance was examined with a portable force platform with eyes open and closed. The trajectory of the total body centre of force (CoF) displacement over the platform was computed by multiple planes obtaining different measures: sway area, velocity, acceleration and body loads. The joint status of cases was assessed with the Haemophilia Joint Health Score. Cases were more disharmonic than controls (52% vs. 26% in controls; P = 0.04), swayed significantly less and more slowly than controls (P < 0.05 for several parameters of CoF displacement) revealing stiffness of the musculoskeletal system. However, they were able to maintain their stance within a similar sway area. Haemophilic boys have more postural disharmonies than non-haemophilic peers, hence a global evaluation of the orthopaedic status should include also balance and posture examination to identify early dysfunction and establish a tailored physical or rehabilitation programme.

Results from a large multinational clinical trial (guardian™1) using prophylactic treatment with turoctocog alfa in adolescent and adult patients with severe haemophilia A: safety and efficacy.

Recombinant factor VIII (rFVIII) products provide a safe and efficacious replacement therapy for prophylaxis and treatment of bleeding episodes in patients with severe haemophilia A. This multinational, open-label, non-controlled trial investigated the safety and efficacy of turoctocog alfa, a new rFVIII product. The primary objective was to evaluate safety. A total of 150 patients (24 adolescents and 126 adults) with severe haemophilia A (FVIII activity ≤ 1%), with at least 150 exposure days (EDs) to any FVIII product and no history of inhibitors were enrolled, and 146 patients (97%) completed the trial. All patients received prophylaxis with turoctocog alfa for approximately 6 months and had a mean of 85 EDs during the trial. None of the patients developed FVIII inhibitors, there were no indications of early FVIII inhibitor development and no safety concerns were identified. A total of 225 adverse events were reported in 100 (67%) patients, with the most common being events associated with dosing procedures, headaches, and nasopharyngitis. A total of 499 bleeding episodes were reported during the trial, the majority (89%) were controlled with 1-2 infusions of turoctocog alfa. Based on patient reports, the success rate (defined as 'excellent' or 'good' haemostatic response) for treatment of bleeding episodes was 81%. The overall median annualized bleeding rate was 3.7 (interquartile range: 8.7) bleeds/patient/year. In conclusion, turoctocog alfa provides a new, safe and effective alternative for prophylaxis and treatment of bleeding episodes in patients with haemophilia A.

Source and purity of factor VIII products as risk factors for inhibitor development in patients with hemophilia A.

BACKGROUND: Inhibitor development is influenced by several factors and the type of factor VIII (FVIII) products may play a role. OBJECTIVES: In order to explore such a role, we designed a cohort study whose novelty resides in the classification of products not only according to the source of FVIII (plasmatic, pd, or recombinant, r) but also to their degree of purity (expressed as specific activity). PATIENTS/METHODS: Treatment data up to inhibitor development or 150 exposure days were collected in 377 patients with hemophilia A. RESULTS: Inhibitors developed in 111 patients (29%; 96 high-responders, 25%). The cumulative incidence was progressively higher from patients treated with low/intermediate-purity pdFVIII compared with those treated with high-purity pd and rFVIII. The adjusted hazard ratio of inhibitor development was 4.9 with rFVIII and 2.0 with high-purity pdFVIII (95% CI, 2.9-8.3 and 1.1-4.0), taking as reference low/intermediate-purity pdFVIII. There was no difference in the frequency of inhibitor testing between treatment groups. Sensitivity analyses (in patients who never switched product type, previously untreated patients, those treated on-demand and those with high-risk F8 mutations) confirmed an increased inhibitor risk with rFVIII and high-purity pdFVIII. CONCLUSIONS: This study shows that the degree of purity of FVIII products influences inhibitor development independently from other risk factors, and emphasizes that differences exist within pdFVIII products.