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Analyses of the bleeding tendency by means of the bleeding score (BS) have been proposed until now to confirm diagnosis but not to predict clinical outcomes in patients with inherited von Willebrand disease (VWD). We prospectively followed up, for 1 year, 796 Italian patients with different types of VWD to determine whether the previous BS of European VWD1 is useful to predict the occurrence of spontaneous bleeds severe enough to require replacement therapy with desmopressin (DDAVP) and/or von Willebrand factor (VWF)/factor VIII concentrates. Among the 796 patients included, 75 (9.4%) needed treatment of 232 spontaneous bleeding events. BS >10 and VWF:ristocetin cofactor activity <10 U/dL were associated with the risk of bleeding, but only a BS >10 remained highly associated in a multivariable Cox proportional hazard model (adjusted hazard ratio: 7.27 [95% confidence interval, 3.83-13.83]). Although the bleeding event-free survival was different in VWD types, only a BS >10 could predict for each type which patient had bleeding events severe enough to require treatment with DDAVP and/or concentrates. Therefore, BS can be considered a simple predictor of clinical outcomes of VWD and may identify patients needing intensive therapeutic regimens.

Analyses of the bleeding tendency by means of the bleeding score (BS) have been proposed until now to confirm diagnosis but not to predict clinical outcomes in patients with inherited von Willebrand disease (VWD). We prospectively followed up, for 1 year, 796 Italian patients with different types of VWD to determine whether the previous BS of European VWD1 is useful to predict the occurrence of spontaneous bleeds severe enough to require replacement therapy with desmopressin (DDAVP) and/or von Willebrand factor (VWF)/factor VIII concentrates. Among the 796 patients included, 75 (9.4%) needed treatment of 232 spontaneous bleeding events. BS >10 and VWF:ristocetin cofactor activity <10 U/dL were associated with the risk of bleeding, but only a BS >10 remained highly associated in a multivariable Cox proportional hazard model (adjusted hazard ratio: 7.27 [95% confidence interval, 3.83-13.83]). Although the bleeding event-free survival was different in VWD types, only a BS >10 could predict for each type which patient had bleeding events severe enough to require treatment with DDAVP and/or concentrates. Therefore, BS can be considered a simple predictor of clinical outcomes of VWD and may identify patients needing intensive therapeutic regimens.

Summary. Background:Inhibitor development is influenced by several factors and the type of factor VIII (FVIII) products may play a role.

Background:Immune tolerance induction (ITI) is the only therapeutic approach that can eradicate factor VIII (FVIII) inhibitors in patients with hemophilia A. Predictors of ITI outcome are still debated, and the role of F8gene mutations in this is not well established. Objectives:To investigate the relationship between F8genotype and ITI outcome in patients with severe hemophilia A and high‐responding inhibitors. Patients and Methods:F8mutations were identified in 86 patients recruited as part of the Italian ITI registry (the PROFIT study). ITI outcome was centrally reviewed according to the following definitions: success (undetectable inhibitor and normal FVIII pharmacokinetics), partial success (inhibitor titer < 5 BU mL−1and/or abnormal FVIII pharmacokinetics), and failure. Results:F8mutations known to be associated with a high risk of inhibitor development (large deletions, inversions, nonsense mutations and splice site mutations) were found in 70 patients (81%); among these, the intron 22 inversion was present in 49 patients (57%). In 16 patients (19%) lower‐risk F8defects (small insertions/deletions and missense mutations) were identified. The latter group of patients showed a significantly higher ITI success rate than those carrying high‐risk mutations [13/16 (81%) vs. 33/70 (47%); risk ratio 1.7, 95% confidence interval (CI) 1.1–2.1, P = 0.01]. On multivariate analysis, the mutation risk class remained a significant predictor of success [adjusted odds ratio (OR) 6.2, 95% CI 1.1–36.0, P = 0.04], as were inhibitor titer at ITI start (< 5 BU mL−1, OR 11.8, 95% CI 3.5–40.2, P< 0.001), and peak titer during ITI (< 100 BU mL−1, OR 11.4, 95% CI 3.2–40.8, P < 0.001). Conclusions:ITI success is influenced by F8genotype. This knowledge should contribute to the stratification of prognosis, and to the clinical choices made for ITI in patients with high‐responding inhibitors.

Aim: A multicenter randomized open‐label crossover prospective trial was designed to compare the efficacy, safety, and cost of standard and high dosages of recombinant factor VIIa (rFVIIa) for home treatment of hemarthroses in hemophiliacs with inhibitors. Methods: Patients were instructed to treat, within 6 h from the onset of bleeding, four consecutive hemarthroses of ankles, knees, or elbows, either with the rFVIIa standard dose of 90 μg kg−1(repeated as necessary every 3 h) or with a single high dose of 270 μg kg−1. Patients who did not achieve a clinical success within 9 h continued rFVIIa treatment with repeated standard doses. Response to treatment was assessed for up to 48 h by patients/caregivers, who reported on a Visual Analogue Scale (VAS) graded from 0 to 100 the improvement in symptoms and also rated the responses as effective, partially effective or ineffective. Success was defined a treatment course rated as effective and with a VAS score ≥70 and failure a treatment course rated as ineffective and VAS score ≤30, whereas treatment courses that did not fulfill these criteria were considered partial responses. Results: Twenty hemophiliacs with inhibitors were originally enrolled (median age: 27 years), 18 of them treated 32 hemarthroses assigned to the standard‐dosage and 36 to the high‐dosage regimen, during the study period of 18 months. Forty‐eight hemarthroses (71%) occurred in target joints. Success rates for standard‐ and high‐dosage regimens were similar: 31% and 25% at 9 h, 53% and 50% at 24 h, 66% and 64% at 48 h, the end point for outcome assessment. The median number of rFVIIa infusions needed to achieve a successful course was significantly greater for the standard‐dosage (n = 3) than for the high‐dosage regimen (n = 1), and the median amount of rFVIIa ultimately used per successful course was identical (270 μg kg−1). Conclusion: Our results indicate that a high‐dosage regimen with rFVIIa for home treatment of hemarthroses is effective, safe, does not imply an increased consumption of rFVIIa and requires the infusion of a smaller number of rFVIIa doses. Its convenience is particularly relevant in cases with difficult venous access and in hemorrhages into target joints.

Hepatocellular carcinoma (HCC) is an increasingly frequent cause of mortality in hemophiliacs with chronic viral hepatitis. Early diagnosis of the tumor at an initial stage is known to improve the outcome of HCC treatment. Because all HCC cases detected in a previous study based upon annual ultrasound (US) surveillance of hemophiliacs with elevated alanine aminotransferase levels were multinodular, this study was designed to evaluate if a more intense surveillance with US and alphafetoprotein (AFP) serum levels of all the patients infected with the hepatitis C virus (HCV) improved the identification of single nodule tumors. A multicenter cohort of 559 HCV-infected hemophiliacs was divided into 2 arms, one followed up at 6-month intervals and one at 12-month intervals depending on the choice and available facilities of each treatment center. During a 6-year surveillance period, HCC was diagnosed in 5 (2.4%) of 210 patients in the 6-month group and in 3 (0.9%) of 349 patients in the 12-month group. The overall incidence rate of HCC was 239 per 100 000 per year (397 per 100 000 per year in the 6-month group and 143 per 100 000 per year in the 12-month group; differences not statistically significant). By multivariate analysis, HCC risk was increased 12.9-fold with alcohol intake more than 80 g/d and 15.2-fold with AFP levels higher than 11 ng/mL. Liver-related death occurred in 8 cases (1.4%), including 3 with HCC. Still alive and tumor free after 24 to 34 months from diagnosis are 3 patients with multinodular tumors treated with repeat chemoembolization followed by orthotopic liver transplantation. In conclusion, 6-month surveillance with US did not increase the chances of detection of single nodule tumors, but it is reasonable to assume that successful treatment of multinodular tumors based upon debulking with chemoembolization and liver transplantation was facilitated by this approach. (Blood. 2003;102:78-82)

Hepatocellular carcinoma (HCC) is an increasingly frequent cause of mortality in hemophiliacs with chronic viral hepatitis. Early diagnosis of the tumor at an initial stage is known to improve the outcome of HCC treatment. Because all HCC cases detected in a previous study based upon annual ultrasound (US) surveillance of hemophiliacs with elevated alanine aminotransferase levels were multinodular, this study was designed to evaluate if a more intense surveillance with US and alphafetoprotein (AFP) serum levels of all the patients infected with the hepatitis C virus (HCV) improved the identification of single nodule tumors. A multicenter cohort of 559 HCV-infected hemophiliacs was divided into 2 arms, one followed up at 6-month intervals and one at 12-month intervals depending on the choice and available facilities of each treatment center. During a 6-year surveillance period, HCC was diagnosed in 5 (2.4%) of 210 patients in the 6-month group and in 3 (0.9%) of 349 patients in the 12-month group. The overall incidence rate of HCC was 239 per 100 000 per year (397 per 100 000 per year in the 6-month group and 143 per 100 000 per year in the 12-month group; differences not statistically significant). By multivariate analysis, HCC risk was increased 12.9-fold with alcohol intake more than 80 g/d and 15.2-fold with AFP levels higher than 11 ng/mL. Liver-related death occurred in 8 cases (1.4%), including 3 with HCC. Still alive and tumor free after 24 to 34 months from diagnosis are 3 patients with multinodular tumors treated with repeat chemoembolization followed by orthotopic liver transplantation. In conclusion, 6-month surveillance with US did not increase the chances of detection of single nodule tumors, but it is reasonable to assume that successful treatment of multinodular tumors based upon debulking with chemoembolization and liver transplantation was facilitated by this approach. (Blood. 2003;102:78-82)

Very high purity factor VIII (FVI1I) concentrates (plasma‐derived or produced by recombinant‐DNA technology) were used to achieve immune tolerance in five patients with high‐responding inhibitors to FVIII. The mean time required for inhibitor disappearance was 5 months. Four out of five patients showed normalisation of the half‐life of infused FVIII after 8–18 months of treatment with 100 IU FVIII/kg body weight administered once daily. Highly purified FVIII products thus appear to be suitable for achieving immune tolerance without negative effects on endogenous von Willebrand factor levels and activity.

AbstractVery high purity factor VIII (FVIII) concentrates (plasma–derived or produced by recombinant–DNA technology) were used to achieve immune tolerance in five patients with high–responding inhibitors to FVIII. The mean time required for inhibitor disappearance was 5 months. Four out of five patients showed normalisation of the half–life of infused FVIII after 8–18 months of treatment with 100 IU FVIII/kg body weight administered once daily. Highly purified FVIII products thus appear to be suitable for achieving immune tolerance without negative effects on endogenous von Willebrand factor levels and activity.

Pathophysiologic considerations as well as noncomparative clinical results suggest that very high purity concentrates may slow immunologic deterioration in human immunodeficiency virus (HlV)-infected hemophiliacs. In an attempt to evaluate this hypothesis, we prospectively compared CD4 cell counts, skin testing responses, and changes of the clinical status in 20 asymptomatic HIV-positive hemophiliacs, randomly assigned to continue the treatment with an intermediate purity concentrate or to receive a very high purity product, purified by immunoaffinity chromatography with monoclonal antibodies. In the group switched to the very high purity concentrate there was no significant change of the CD4 cell counts over the 96-week follow-up period, whereas in the group continued on the intermediate purity concentrate, a highly significant decline was detected (P < .013). Furthermore, in the very high purity group, four of six anergic patients at entry acquired reactivity to skin testing. The results of this study clearly support the use of very high purity concentrates for the replacement therapy of HIV-infected hemophiliacs.

Pathophysiologic considerations as well as non-comparative clinical results suggest that very high purity concentrates may slow immunologic deterioration in human immunodeficiency virus (HIV)-infected hemophiliacs. In an attempt to evaluate this hypothesis, we prospectively compared CD4 cell counts, skin testing responses, and changes of the clinical status in 20 asymptomatic HIV-positive hemophiliacs, randomly assigned to continue the treatment with an intermediate purity concentrate or to receive a very high purity product, purified by immunoaffinity chromatography with monoclonal antibodies. In the group switched to the very high purity concentrate there was no significant change of the CD4 cell counts over the 96-week follow-up period, whereas in the group continued on the intermediate purity concentrate, a highly significant decline was detected (P less than .013). Furthermore, in the very high purity group, four of six anergic patients at entry acquired reactivity to skin testing. The results of this study clearly support the use of very high purity concentrates for the replacement therapy of HIV-infected hemophiliacs.

To assess the risk factors, natural history, and eligibility for curative treatment of early-detected hepatocellular carcinoma (HCC), 385 hemophiliacs who were treated with blood or plasma derivates for at least 10 years and had persistently elevated aminotransferase values underwent an annual screening with an abdominal ultrasound examination and measurement of the serum alpha-fetoprotein (AFP) level. Of these, 355 had serum antibody to hepatitis C virus (anti-HCV), 29 had anti-HCV and hepatitis B surface antigen (HBsAg), and one had HBsAg alone; 141 had serum antibody to human immunodeficiency virus (anti-HIV). During 48 months of follow-up study, six patients developed HCC. All HCC patients had a HCV-related cirrhosis and had been exposed to HCV risk at a median age of 40 years. All patients had a multicentric tumor, which was not eligible for curative treatment. Univariate analysis showed age, cirrhosis, and baseline AFP levels to be significantly associated with an increased risk of HCC. By multivariate analysis, the risk of HCC was infinite in patients with cirrhosis, 31.0 for those with baseline AFP higher than 11 ng/mL, and 17.9 for those more than 45 years of age. In conclusion, the risk of cancer was greater for patients infected later in life, particularly those with cirrhosis and high AFP. Annual screening of hemophiliacs with ultrasound and AFP fails to identify potentially curable tumors because the diagnosis is made at a late stage of the disease.

Guanylate cyclase, which catalyzes the synthesis of guanosine 3',5'-monophosphate, has been assayed in several strains of Escherichia coli. They include wild-type cells and mutants defective in adenylate cyclase, which is responsible for the synthesis of adenosine 3',5'-phosphate. Our results demonstrate that adenylate cyclase and guanylate cyclase are two different enzymes in E. coli and suggest that the gene that encodes adenylate cyclase also plays a regulatory role in the synthesis of guanylate cyclase.

Two cross-reacting material–positive (CRM+) factor VII (FVII) mutations, associated with similar reductions in coagulant activity (2.5%) but with mild to asymptomatic (Gly331Ser, c184 [in chymotrypsin numbering]) or severe (Gly283Ser, c140) hemorrhagic phenotypes, were investigated. The affected glycines belong to structurally conserved regions in the c184 through c193 and c140s activation domain loops, respectively. The natural mutants 331Ser-FVII and 283Ser-FVII were expressed, and in addition 331Ala-FVII and 283Ala-FVII were expressed because 3 functional serine-proteases bear alanine at these positions. The 331Ser-FVII, present in several asymptomatic subjects, showed detectable factor Xa generation activity in patient plasma (0.7% ± 0.2%) and in reconstituted system with the recombinant molecules (2.7% ± 1.1%). The reduced activity of recombinant 283Ala-FVII (7.2% ± 2.2%) indicates that the full function of FVII requires glycine at this position, and the undetectable activity of 283Ser-FVII suggests that the oxydrile group of Ser283 participates in causing severe CRM+ deficiency. Furthermore, in a plasma system with limiting thromboplastin concentration, 283Ser-FVII inhibited wild-type FVIIa activity in a dose-dependent manner.

Two cross-reacting material–positive (CRM+) factor VII (FVII) mutations, associated with similar reductions in coagulant activity (2.5%) but with mild to asymptomatic (Gly331Ser, c184 [in chymotrypsin numbering]) or severe (Gly283Ser, c140) hemorrhagic phenotypes, were investigated. The affected glycines belong to structurally conserved regions in the c184 through c193 and c140s activation domain loops, respectively. The natural mutants 331Ser-FVII and 283Ser-FVII were expressed, and in addition 331Ala-FVII and 283Ala-FVII were expressed because 3 functional serine-proteases bear alanine at these positions. The 331Ser-FVII, present in several asymptomatic subjects, showed detectable factor Xa generation activity in patient plasma (0.7% ± 0.2%) and in reconstituted system with the recombinant molecules (2.7% ± 1.1%). The reduced activity of recombinant 283Ala-FVII (7.2% ± 2.2%) indicates that the full function of FVII requires glycine at this position, and the undetectable activity of 283Ser-FVII suggests that the oxydrile group of Ser283 participates in causing severe CRM+deficiency. Furthermore, in a plasma system with limiting thromboplastin concentration, 283Ser-FVII inhibited wild-type FVIIa activity in a dose-dependent manner.

Background/Aim: The “FEIBA GO” study was designed to capture long-term outcomes on effectiveness, safety and quality of life in subjects with haemophilia and inhibitors treated with APCC in routine clinical practice. The primary objective is to describe the hemostatic effectiveness of APCC in different settings such as prophylaxis and on demand, including patients on immune-tolerance induction; most relevant secondary objectives are: joint functionality outcomes, safety, health-related quality of life (HR-QoL), daily activity level, acute and chronic pain associated with haemophilia, healthcare resources used.

Cid: Baxalta Innovations GmbH, now part of Shire: Other: Investigator Clinical Studies. Escuriola:Baxalta, now part of Shire: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Investigator Clinical Studies, Research Funding; Bayer: Consultancy, Honoraria, Research Funding; Biotest: Consultancy, Honoraria, Research Funding; CSL Behring: Consultancy, Honoraria, Research Funding; Grifols: Consultancy, Honoraria, Research Funding; Octapharma: Consultancy, Honoraria, Research Funding; NovoNordisk: Consultancy, Honoraria, Research Funding. Hermans:Baxalta, now part of Shire: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Investigator Clinical Studies. Holme:Baxalta, now part of Shire: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Investigator Clinical Studies. Negrier:LFB: Membership on an entity's Board of Directors or advisory committees; Bayer: Membership on an entity's Board of Directors or advisory committees, Other: Travel support; SOBI: Membership on an entity's Board of Directors or advisory committees; Octapharma: Membership on an entity's Board of Directors or advisory committees, Other: Travel support, Research Funding; Baxter: Membership on an entity's Board of Directors or advisory committees; Pfizer: Research Funding; Alnylam: Research Funding; CSL Behring: Membership on an entity's Board of Directors or advisory committees, Research Funding; NovoNordisk: Membership on an entity's Board of Directors or advisory committees, Other: Travel support, Research Funding. Rangarajan:Baxter: Research Funding; Grifols: Consultancy, Research Funding; Biogen: Consultancy; Pfizer: Research Funding; Baxalta, now part of Shire: Other: Investigator Clinical Studies, Research Funding; Novo Nordisk: Research Funding; Biotest: Research Funding. Rocino:Baxalta, now part of Shire: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Investigator Clinical Studies; Bayer: Honoraria, Membership on an entity's Board of Directors or advisory committees; NovoNordisk: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; CSL Behring: Consultancy, Honoraria; Kedrion: Consultancy, Honoraria; Sobi: Consultancy, Honoraria. Windyga:Octapharma: Consultancy, Equity Ownership, Honoraria, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding, Speakers Bureau; Alexion: Other: Speaker's honorarium; Biogen: Consultancy, Equity Ownership, Honoraria, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding, Speakers Bureau; Sanofi: Consultancy, Equity Ownership, Honoraria, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding, Speakers Bureau; CSL Behring: Consultancy, Equity Ownership, Honoraria, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding, Speakers Bureau; Aspen: Consultancy, Equity Ownership, Honoraria, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding, Speakers Bureau; Nordisk: Consultancy, Equity Ownership, Honoraria, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding, Speakers Bureau; Baxalta, now part of Shire: Consultancy, Equity Ownership, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Investigator Clinical Studies, Patents & Royalties, Research Funding, Speakers Bureau. Gringeri:Shire: Employment, Equity Ownership. Crea:Shire: Employment, Equity Ownership.

Introduction: Data on APCC´s effectiveness, safety and quality of life are relatively poor because of the rarity of patients with FVIII or FIX inhibitors, the small populations included in clinical trials and the relatively short follow-up available. The FEIBA-GO study was designed to capture long-term outcomes on effectiveness, safety and health-related quality of life (HR-QoL) in subjects receiving APCC in different settings in routine clinical practice.

Inhibitor development is influenced by several genetic and environmental factors and the type of factor VIII (FVIII) products may play a role. Methods: We designed a cohort study whose novelty resides in the classification of products not only according to the plasmatic (pdFVIII) or recombinant (rFVIII) source of FVIII but also to the degree of purity expressed as FVIII specific activity per mg of protein. The role of FVIII product as risk factor for inhibitor development was evaluated in a multivariate model adjusting for potential confounders (i.e. age at first FVIII exposure, intensive treatment and prophylaxis). Cumulative incidences of all and high-responding inhibitors were calculated for the whole cohort of 721 patients with severe and moderate hemophilia A followed-up in 3 Italian Hemophilia Centers. Detailed treatment data from the first FVIII infusion up to inhibitor development or 150 exposure days were available for 377 patients and in this group of patients risk factors for inhibitor development including the type of FVIII product and its degree of purity (i.e. low/intermediate-, high-purity pdFVIII and rFVIII) were analysed. Results: The overall cumulative incidence of inhibitors was 22% (n=160; 130 high-responders, 18%) and it was lower in patients first treated with pdFVIII (107/586, 18%) than in those treated with rFVIII (53/135, 39%). Similar results were obtained by evaluating only high-responding inhibitors and patients with severe hemophilia. 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 in patients first treated with rFVIII or high-purity pdFVIII than in those treated with low/intermediate-purity pdFVIII. In fact, in all the aforementioned subgroups by multivariate analysis the risk of inhibitor development was invariably 3- to 6-fold higher in patients first treated with rFVIII than in those first treated with pdFVIII, and similar results were obtained for both all inhibitors and high-responding inhibitors. 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 also within pdFVIII products.No relevant conflicts of interest to declare.

Abstract 25This icon denotes a clinically relevant abstract

Patients with congenital hemophilia and inhibitors are at increased risk for serious bleeding complications and progression to end-stage joint disease. Anecdotal reports and small case series suggest that regular doses of anti-inhibitor coagulant complex (AICC; FEIBA VH) may be effective in preventing bleeding episodes in patients with hemophilia A and inhibitors. The Pro-FEIBA study is the first prospective controlled clinical trial to study the efficacy of AICC in bleed prevention.The study was conducted in hemophilia A patients >2 years with a history of high-titer inhibitors who were using bypassing therapy for the treatment of bleeding episodes. Subjects on or planning immune tolerance therapy were excluded as were patients with thrombocytopenia or other bleeding disorders. This randomized, crossover study compared 6 months of AICC prophylactically dosed at 85 U/kg ± 15% on 3 nonconsecutive days per week (Prophy period) to 6 months of on-demand therapy (OD period) (target dose for the treatment of bleeds: 85 U/kg ± 15%). The 2 study periods were separated by a 3-month washout, during which time patients used on-demand therapy for bleeding. Patients were randomized to initially enter either the 6-month Prophy period or the 6-month OD period. Each patient then crossed-over to the alternate study period after a 3-month wash-out.Thirty-four subjects were randomized; 26 subjects completed both study periods and were deemed evaluable per protocol (PP) for efficacy analysis of the primary outcome to compare bleeds in each 6-month treatment period. Eight subjects did not complete the study (1 patient in the Prophy treatment arm and 1 patient in the post-prophylaxis washout period died of complications associated with underlying illness and bleeding, 1 patient experienced an allergic reaction to study drug, 1 patient was lost to follow-up, and 4 patients withdrew from study). All randomized subjects were evaluated for safety. In the PP group, mean patient age was 26.9 years (median: 24.7; range: 2.8–67.9). In the total randomized group, mean patient age was 27.1 years (median: 28.7; range: 2.8–67.9). Of the 26 subjects who completed the study PP, 14 were randomized to enter the Prophy period first and then crossed-over to the OD period, while 12 subjects were initially randomized to enter the OD period and then crossed-over to the Prophy period. For the PP analysis, total bleeds and joint bleeds requiring treatment during the 2 study periods were compared (p-value is for the Wilcoxon signed-rank test of difference between OD and Prophy periods). In addition, bleeds for the 6-month period prior to enrollment were recorded retrospectively on study entry.Both total bleeds and joint bleeds were significantly reduced during the Prophy period as compared with the OD period (p < .0001) Table 1. There was no difference in bleed event rates based on randomization sequence (ie, no carry-over effect was detected when the Prophy period preceded the OD period).A total of 38 serious adverse events (SAEs) occurred, none of which was thrombotic in nature. One SAE was deemed by the study safety monitor to be related to the study drug (an allergic reaction). Otherwise, treatment was safe and well tolerated.These results in patients with hemophilia A and inhibitors show that AICC, dosed at 85 IU/kg +/− 15% given on 3 non-consecutive days each week was associated with a 62% reduction in all bleeds and a 61% reduction in joint bleeds as compared with on-demand therapy.Leissinger: Baxter: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; NovoNordisk: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Off Label Use: This is a report of a clinical trial using the Anti-Inhibitor Coagulant Complex, FEIBA, as prophylactic therapy to prevent bleeding in hemophilia patients with inhibitors. FEIBA is not currently licensed for use in prophylaxis in the US. Berntorp:Baxter: Consultancy, Honoraria, Research Funding. Negrier:Baxter: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Rocino:Baxter: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; NovoNordisk: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Windyga:Baxter: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Gringeri:Baxter: Consultancy, Honoraria, Research Funding; NovoNordisk: Honoraria.

Abstract 720

This retrospective study evaluates the interactions of known determinants of the inhibitor risk in severe and moderate hemophiliacs followed-up at 3 Italian Hemophilia Centers.clinical data up to inhibitor development or 150 exposure days (EDs) were collected in 393 patients with Factor VIII <5% (FVIII <1%: 331, 84%) and median age of 27 years (interquartile range, IQR:15-36) first treated with plasma-derived (pdFVIII, 70%) or recombinant products (rFVIII, 30%). Exposure to blood components for more than 4 days was an exclusion criterion.the F8 genotype was known in 334 patients (85%), 57% with null mutations (nonsense mutations, inversions and large deletions). Inhibitors (titer ≥ 0.6 BU/ml on at least two consecutive occasions and FVIII recovery <66% of expected) were detected in 112 patients (28%) after a median of 17 EDs (IQR:10-29), being high responding (HR, peak titer ≥ 5 BU/ml) in 23% and transient in 7%. Table 1 shows the crude and adjusted hazard ratios of potential determinants of inhibitor development in this cohort. Intensive treatment was defined as treatment duration ≥ 3 consecutive days at a dose ≥ 50 IU/kg/day. Sub-analyses were performed in 272 patients who never switched class of product (pdFVIII and rFVIII) and in 314 patients who did not started prophylaxis (≥ 1 regular infusion per week): in both cases the use of rFVIII at first exposure was associated with an increased inhibitor risk (adjusted hazard ratio 5.1, 95%CI 1.5-16.9 and 4.1, 95%CI 1.8-9.4, respectively). Similar results were obtained also excluding 103 patients (26%) who were first exposed to blood components (adjusted hazard ratio 3.5, 95%CI 1.5-7.9). Interestingly, patients with null mutations treated with rFVIII had a higher inhibitor risk than those first treated with pdFVIII (adjusted hazard ratio 3.3, 95%CI 1.4-7.6), while no difference was found in patients with non null mutations treated with rFVIII (hazard ratio 1.4, 95%CI 0.5-3.7). These results were confirmed including only high-responding inhibitors in the analysis.our results show the influence of the interaction between type of FVIII product and F8 genotype on inhibitor risk, being the use of rFVIII associated with an higher risk in patients with null mutations. In our cohort this association was confirmed also after adjustment for the other known genetic and environmental risk factors of inhibitor development.No relevant conflicts of interest to declare.

von Willebrand disease type 3 (VWD3) is due to virtually complete deficiency of the von Willebrand factor (VWF) and, for this reason, has been also described as “severe VWD”. Although rare (1-5 cases per million population), VWD3 is of major interest because of its severe clinical presentation, the need for replacement therapy with VWF/FVIII concentrates and the risk of occurrence of anti-VWF inhibitors after the infusion of VWF/FVIII concentrates.to determine the prevalence and determinants of bleedings requiring therapy with VWF/FVIII concentrates in VWD3 patients, data were collected from the Italian registry on Hemophilia and Allied Disorders organized on behalf of the Italian Association of Hemophilia Centers (AICE). The VWD3 patients included in the registry were then followed up for one year by six Italian Centers and prospective data on number, type and management of bleeding episodes were analyzed.VWD3 patients were diagnosed when VWF antigen was undetectable and factor VIII (FVIII) levels were reduced in plasma. Bleeding severity score (BSS) was calculated at enrollment. Gene deletions and mutations were searched for in all available DNA. Bleeding-free survival was computed with the Kaplan-Meier method and a Cox's proportional hazard model was used to calculate the risk of bleeding (hazard ratio = HR)In the Italian registry, 105 VWD3 patients (5.7%) were identified among the 1850 VWD (Italian prevalence=1.75 per million). The entire cohort of VWD3 was characterized by the following demographic, clinical and laboratory parameters (median, range): gender (M/F)= 50/55; age=37 (3-65); BSS=18 (3-35); FVIII= 4 (2-18); anti-VWF inhibitors= 7 cases (6.7%) from 3 families. Molecular diagnosis was available in 65/105 cases with the following gene defects (pt-n): large deletion (7); small deletions and insertions (23); nonsense (9); splice site (8) and missense mutations (17). Mucosal bleedings (64%) were more frequent than hematomas and hemarthrosis (24%). At the time of the enrollment in the registry 95/105 (91%) VWD3 had been already exposed to VWF/FVIII concentrates because of bleeding and/or minor or major surgeries. In the prospective study, 52 VWD3 patients could be enrolled and 46 (88%) were treated in a year for 118 bleeding episodes and 27 minor or major surgeries. BSS>10 (6.8, 3.8-12.3) and FVIII<10U/dL (4.1, 2.4-7) were significantly associated with high risk of bleeding. The bleeding-free survival at one year calculated according to values of BSS and FVIII levels showed 4 different KM curves with the following results:89% (BSS=5-10&FVIII>10U/dL); 64%(BSS>10&FVIII=5-10U/dL);59% (BSS=5-10&FVIII<10U/dL); 18%(BSS>10&FVIII<5U/dL). A total of 192 injections of VWF/FVIII concentrates were used to treat bleeding and surgeries in VWD3. Patients with anti-VWF inhibitors were off therapy during this follow-up.these retro/prospective studies performed for the first time in a relative large cohort of patients show that also VWD3 can be very heterogeneous. BSS & FVIII levels are good predictors of bleeding. Larger multicenter studies should be organized to identify possible additional modifiers influencing the risk of bleeding in VWD3.No relevant conflicts of interest to declare.

Abstract 3500

Abstract 3494

Background. von Willebrand disease (VWD) is the most common inherited bleeding disorder and is due to quantitative and/or qualitative defects of von Willebrand factor (VWF). Despite the improved knowledge of the disorder, no data on the incidence and determinants of bleedings requiring specific treatments have been available thus far. Aims and design of the study: to determine the incidence and determinants of bleedings requiring therapy with DDAVP and/or VWF concentrates in VWD, a national registry was organized by using a database devised to collect detailed retrospective information. Patients included in the registry were followed up for one year and prospective data on number, type and management of bleeding episodes were analyzed. Methods: all patients were diagnosed following recommendations of the ISTH-SSC-SC on VWF with bleeding severity score (BSS) calculated at enrollment. Diagnoses of VWD were confirmed by the coordinating center using also multimeric analysis in plasma and mutations of VWF gene in all types 2 and 3. For different risk categories the incidence of bleeding (mucosal and non-mucosal bleeding) was calculated. Bleeding-free survival was computed with the Kaplan-Meier method and a Cox’s proportional hazard model was used to calculate the risk of bleeding (hazard ratio = HR) Results: In the retrospective study, 1,234/1,529 (81%) cases satisfied the inclusion criteria and were enrolled in the registry as types 1 (54%), 2 (40%) and 3 (6%).VWD diagnosis occurs in young adults (83%), mainly in women (57%). Mucosal bleeding (64%) are more frequent than hematomas or hemarthrosis (15%) but 73% of patients did not require transfusions. In the prospective study based on 814/1,234 (66%) cases of the registry (type 1=47%, 2=47%, 3=6%) 147/815 (18%) were treated in a year for 318 bleeding episodes and 87 minor or major surgeries. BSS >10 (6.8, 3.8–12.3), bleeding time >20 min (BT = 5.5, 3.1–9.8), VWF:RCo <10 U/dL (3.2, 1.7–5.9) and FVIII:C <20 U/dL (4.1, 2.4–7) were significantly associated with high risk of bleeding. By multivariate model including all the variables, BSS (5.5, 2.8–10.8) was the most significant determinant of bleeding. The bleeding-free survival at one year was significantly different in type 3 (52%) versus types 1 (96%) and 2 (91%) VWD. On the other hands, patients with VWF.RCo >30 U/dL and FVIII:C > 40 U/dL showed always BSS <5 with the lowest incidence of bleeding. A total of 292 DDAVP injections were used to manage bleeding and surgeries in types 1 (65%) and 2 (35%) VWD and 452 injections of VWF concentrates were used to treat bleeding and surgeries in type 3 (75%), type 2 (34%) and type 1 (15%) VWD. Conclusions: This prospective study confirms that BSS is an important predictive factor for clinical bleeding and the need for treatment. In cases with VWF.RCo >30 U/dL and FVIII:C >40 U/dL bleeding episodes are very rare, in agreement with their relatively low BSS.

Backgrounds. Not pegilated liposomal doxorubicin (Myocet®) has a better pharmacokinetic profile with less myelosuppression, much lower gastroenterological and cardiological toxicity than conventional doxorubicin. In order to reduce toxicity of conventional doxorubicin, in our department from 2002 to 2007 we have treated patients with Multiple Myeloma (MM) and Non-Hodgkin’s Lymphoma (NHL) with therapeutical regimens replacing conventional anthracyclines with not pegilated liposomal doxorubicin. Methods. In our department, from 2002 to 2007, 35 patients (17M,18F) with a median age of 68.8±9.6(range 82–33) affected by Multiple Myeloma (MM) received one or more cycles according to chemiotherapic scheme: VCR 1mg iv at day 1 + Myocet® 25mg/sm iv at day 2 + CTX 100mg/sm os days 1–4 + PDN 60mg/sm os days 1–4. Diagnosis concerned patients with IgG Myeloma (n=26), IgA Myeloma (n=7), micromolecular Myeloma (n=1) and PL (n=1). 22 patients (16M,6F) with a median age of 63.6±9.6 (range 45–79) affected by NHL received chemoimmunotherapy COMP21-R (CTX, Myocet®, VCR and PDN plus Rituximab). Four patients were stage I, 7 stage II, 6 stage III and 5 stage IV. According to IPI score: 2 patients were low risk, 6 low-intermediate, 8 intermediate-high and 6 high risk. In all patients, chemoimmunotherapy induced cardiologic evaluation was made considering Left Ventricular Ejection Fraction (LVEF): cardiotoxicity was evaluated testing the null hypothesis that the LVEF delta is more negative than −4% of the baseline value before chemotherapy (which was felt to be a reasonable clinical threshold separating non-clinically-significant cardiac toxicity from clinically significant damage due to chemotherapy). Results. In MM patients evaluation of treatment was made for 31 patients: mean Monoclonal Component (MC) has been reduced from 3048.2±2296.9 to 2353,7±1912.4 and the one sided t-test on the variable delta resulted statistically significant (P = 0.038). Response of treatment was CR 43,3%, PR 23,3%, DP 16,7%, NR 16,7% but no statistically significant correlations were present with both the line of treatment and the diagnosis. For NHL evaluation was made in 20 patients: 17 (77.3%) obtained a Complete Remission (CR), 1 (4.5%) a Partial Remission (PR) and 2 (9.1%) Not Respond (NR) to therapy: no statistically significant correlations were present with both the line of treatment and the diagnosis. In all patients (21 NHL and 30MM, totally 51 subjects), Myocet® cardiotoxicity has been evaluated by LVEF assessment at baseline and monitored along the course of the treatment: baseline mean was 57.8±5.4% and slightly lowered to 55.6±5.2% at the end of treatment. For each sub-population and for the entire population a one-sided t-test was performed in order to determine whether therapy with not pegilated liposomal doxorubicin determines relatively low cardiotoxicity: the tests resulted significant (NHL: P = 0.022, MM: P = 0.0021, All: P = 0.00020), leading to reject the null hypothesis in favour of the alternative hypothesis that cardiotoxicity is actually less severe and that the decrement of LVEF is not as negative as −4%. Conclusion. Myocet® reduce cardiotoxicity and is effective in the treatment of MM and NHL patients.

Backgrounds. Not pegilated liposomal doxorubicin (Myocet®) has a better pharmacokinetic profile with less myelosuppression, much lower gastroenterological and cardiological toxicity than conventional doxorubicin. In order to reduce toxicity of conventional doxorubicin, in our department from 2002 to 2007 we have treated patients with Multiple Myeloma (MM) and Non-Hodgkin's Lymphoma (NHL) with therapeutical regimens replacing conventional anthracyclines with not pegilated liposomal doxorubicin.

Background. von Willebrand disease (VWD) is the most common inherited bleeding disorder and is due to quantitative and/or qualitative defects of von Willebrand factor (VWF). Despite the improved knowledge of the disorder, no data on the incidence and determinants of bleedings requiring specific treatments have been available thus far. Aims and design of the study: to determine the incidence and determinants of bleedings requiring therapy with DDAVP and/or VWF concentrates in VWD, a national registry was organized by using a database devised to collect detailed retrospective information. Patients included in the registry were followed up for one year and prospective data on number, type and management of bleeding episodes were analyzed.

Pegylated interferon (Peg-IFN) plus ribavirin is the standard treatment for patients with chronic hepatitis C. In a multicenter open trial, we assessed the efficacy and tolerability of this treatment in 78 HIV negative hemophiliacs (age: 20–64 years) with persistently high transaminase values. Sixty-four were naïve and 14 were relapsers to IFN monotherapy. Cirrhosis was clinically detected in 12 patients (15%). HCV genotype was 1 in 69%, 2a/c in 14%, 3a in 14% and 4 in 3%. Peg-IFN alpha-2b was given subcutaneously at doses of 1.5 mcg/Kg/week for 48 weeks in genotypes 1 and 4 and for 24 weeks in genotypes 2 and 3; oral ribavirin at 800–1200 mg/day based on body weight. Treatment was stopped in patients with polymerase chain reaction positive HCV-RNA at month 6. Results: 11 patients (14%) withdrew for side effects (4) or non-compliance (7). Neutropenia (<500 cells/mmc), decompensated diabetes, ALT flares, and vomiting not responding to antiemetic drugs were reasons for treatment discontinuation. The median fall in hemoglobin levels was 3.1 g/dL. Weight loss (38%), fatigue (33%) and cephalalgia (15%) were frequent side effects. Thirty-two patients (41%) required dose reduction of ribavirin (23, 29%) or Peg-IFN (20, 26%). At the end of the 6-month follow-up, sustained virological response (SVR) was achieved in 43 patients (55%): 40/64 naïve (63%) and 3/14 relapsers (21%, p = 0.007). Five patients (6%), all relapsers to IFN monotherapy, had a virological breakthrough during treatment and 4 (5%) relapsed during the post-treatment follow-up period. SVR was obtained in 86% genotypes 2/3 and 43% genotypes 1/4 (p = 0.001). Predictors of SVR were evaluated by univariate analysis in the 64 naïve patients. SVR was significantly associated with HCV infection type 2 and 3 (86% vs 50% in HCV type 1 and 4; p = 0.008), absence of cirrhosis (97.5% vs 75% in non-responders; p = 0.02) and higher pre-treatment serum ALT levels (111 vs 75 IU/L in non-responders; p = 0.02). SVR rates did not differ in relation to patient’s age, pretreatment HCV viremia, median disease duration and compliance to full-dose treatment. Conclusions: combination therapy with Peg-IFN plus ribavirin is the recommended therapeutic option for hemophiliacs with hepatitis C chronic infection. Relapsers to IFN monotherapy may benefit of re-treatment with Peg-IFN plus ribavirin achieving at least 20% SVR. Genotype 2 and 3 infection is the most significant predictor of SVR.

A multicenter randomized crossover trial was designed to compare efficacy, safety, feasibility and cost associated with standard- and high-dosages of rFVIIa for home treatment of hemarthroses in hemophiliacs with inhibitors. Enrolled patients were instructed to treat within 6 hours from the onset of bleeding 4 consecutive haemarthroses of ankles, knees or elbows either with the rFVIIa standard dose of 90 mcg/kg (repeated as necessary every 3 hours) or with a single high dose of 270 mcg/kg. Patients who did not achieve a success within 9 hours continued rFVIIa treatment with repeated standard doses. The response to treatment was assessed for up to 48 hours by patients/caregivers who reported on a visual analogic scale (VAS) graded from 0 to 100 the improvement in symptoms and also rated the response as effective, partially effective or ineffective. Success was defined a treatment rated as effective and VAS score ≥70 and failure a treatment rated as ineffective and VAS score ≤30, responses that did not fulfil these criteria being considered a partial response. Of 20 hemophiliacs with inhibitors enrolled (median age: 27 years), 18 treated 32 hemarthroses assigned to the standard- and 36 to the high-dose regimen during the study period of 18 months. Forty-eight hemarthroses (71%) occurred in target joints. Success rates for standard- and high-dose regimens were similar: 31% and 25% at 9 hours, 53% and 50% at 24 hours, 66% and 64% at 48 hours. Recurrence rates were identical (3%). The median number of rFVIIa boluses needed to achieve a successful course was 3 for the standard-dose and 1 for the high-dose regimen, and the median amount of rFVIIa used per successful course was identical (270 mcg/kg). Our results indicate that the use of a high-dose regimen with rFVIIa for home treatment of hemarthroses is effective, safe, does not imply an increased consumption of rFVIIa and requires the infusion of a smaller number of boluses. Its convenience is particularly relevant in cases with difficult venous access and in hemorrhages into target joints.

Pegylated interferon (Peg-IFN) plus ribavirin is the standard treatment for patients with chronic hepatitis C. In a multicenter open trial, we assessed the efficacy and tolerability of this treatment in 78 HIV negative hemophiliacs (age: 20–64 years) with persistently high transaminase values. Sixty-four were naïve and 14 were relapsers to IFN monotherapy. Cirrhosis was clinically detected in 12 patients (15%). HCV genotype was 1 in 69%, 2a/c in 14%, 3a in 14% and 4 in 3%. Peg-IFN alpha-2b was given subcutaneously at doses of 1.5 mcg/Kg/week for 48 weeks in genotypes 1 and 4 and for 24 weeks in genotypes 2 and 3; oral ribavirin at 800–1200 mg/day based on body weight. Treatment was stopped in patients with polymerase chain reaction positive HCV-RNA at month 6.

A multicenter randomized crossover trial was designed to compare efficacy, safety, feasibility and cost associated with standard- and high-dosages of rFVIIa for home treatment of hemarthroses in hemophiliacs with inhibitors. Enrolled patients were instructed to treat within 6 hours from the onset of bleeding 4 consecutive haemarthroses of ankles, knees or elbows either with the rFVIIa standard dose of 90 mcg/kg (repeated as necessary every 3 hours) or with a single high dose of 270 mcg/kg. Patients who did not achieve a success within 9 hours continued rFVIIa treatment with repeated standard doses. The response to treatment was assessed for up to 48 hours by patients/caregivers who reported on a visual analogic scale (VAS) graded from 0 to 100 the improvement in symptoms and also rated the response as effective, partially effective or ineffective. Success was defined a treatment rated as effective and VAS score ≥70 and failure a treatment rated as ineffective and VAS score ≤30, responses that did not fulfil these criteria being considered a partial response. Of 20 hemophiliacs with inhibitors enrolled (median age: 27 years), 18 treated 32 hemarthroses assigned to the standard- and 36 to the high-dose regimen during the study period of 18 months. Forty-eight hemarthroses (71%) occurred in target joints. Success rates for standard- and high-dose regimens were similar: 31% and 25% at 9 hours, 53% and 50% at 24 hours, 66% and 64% at 48 hours. Recurrence rates were identical (3%). The median number of rFVIIa boluses needed to achieve a successful course was 3 for the standard-dose and 1 for the high-dose regimen, and the median amount of rFVIIa used per successful course was identical (270 mcg/kg). Our results indicate that the use of a high-dose regimen with rFVIIa for home treatment of hemarthroses is effective, safe, does not imply an increased consumption of rFVIIa and requires the infusion of a smaller number of boluses. Its convenience is particularly relevant in cases with difficult venous access and in hemorrhages into target joints.

In a multicenter case-control study we investigated the impact of prenatal/perinatal events and early FVIII exposure on the inhibitor risk in hemophiliacs. Patients: 102 children (age:13–196 months) with hemophilia A (FVIII≤2%) exclusively treated with recombinant FVIII and evaluated for inhibitors every 3 months were included. Forty-seven patients who developed inhibitors at the median age of 26 months (4–80) after a median of 16 exposure days (ED, 5–150), 37 high-responders (6–500 BU/mL) and 10 low-responders (<5 BU/mL), were compared with 55 children who did not develop inhibitors after at least 20 ED (5<50, 4<100, 10<200 and 36>200 ED). Results: by univariate analysis, family history of inhibitors, intron 22 inversion and prophylaxis started after the first 20 ED were significantly associated with an increased risk of inhibitor development (OR 9.5, 95%CI 1.1–79.9; OR 2.7, 95%CI 1.1–6.6; OR 3.7, 95%CI 1.1–12.1, respectively). No statistically significant differences were found for variables such as villocentesis/amniocentesis, premature/caesarian birth, breast-feeding, surgery, central venous devices and FVIII infusions associated with infections/vaccinations. By multivariate analysis, the inhibitor risk was 2.8-folds (95%CI 1.1–7.3) in children with intron 22 inversion and 4.5-folds (95%CI 1.1–17.5) in patients who started prophylaxis after the first 20 ED. By univariate and multivariate analysis, there was not a linear trend in the inhibitor development according to the age at first FVIII exposure (≤6, 7–12, 13–18, 19–24, >24 months). Conclusions: this study showed that starting prophylaxis within the first 20 ED had a favourable impact on the inhibitor risk independently from the age at first FVIII exposure.

In a multicenter case-control study we investigated the impact of prenatal/perinatal events and early FVIII exposure on the inhibitor risk in hemophiliacs. Patients: 102 children (age:13–196 months) with hemophilia A (FVIII≤2%) exclusively treated with recombinant FVIII and evaluated for inhibitors every 3 months were included. Forty-seven patients who developed inhibitors at the median age of 26 months (4–80) after a median of 16 exposure days (ED, 5–150), 37 high-responders (6–500 BU/mL) and 10 low-responders (<5 BU/mL), were compared with 55 children who did not develop inhibitors after at least 20 ED (5<50, 4<100, 10<200 and 36>200 ED). Results: by univariate analysis, family history of inhibitors, intron 22 inversion and prophylaxis started after the first 20 ED were significantly associated with an increased risk of inhibitor development (OR 9.5, 95%CI 1.1–79.9; OR 2.7, 95%CI 1.1–6.6; OR 3.7, 95%CI 1.1–12.1, respectively). No statistically significant differences were found for variables such as villocentesis/amniocentesis, premature/caesarian birth, breast-feeding, surgery, central venous devices and FVIII infusions associated with infections/vaccinations. By multivariate analysis, the inhibitor risk was 2.8-folds (95%CI 1.1–7.3) in children with intron 22 inversion and 4.5-folds (95%CI 1.1–17.5) in patients who started prophylaxis after the first 20 ED. By univariate and multivariate analysis, there was not a linear trend in the inhibitor development according to the age at first FVIII exposure (≤6, 7–12, 13–18, 19–24, >24 months). Conclusions: this study showed that starting prophylaxis within the first 20 ED had a favourable impact on the inhibitor risk independently from the age at first FVIII exposure.