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

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

Personalized Prophylaxis with myPKFiTCE: A Real-World Cost-Effectiveness Analysis in Haemophilia A Patients.

Background and Objectives: This study aimed to assess the effectiveness and costs associated with pharmacokinetics-driven (PK) prophylaxis based on the myPKFiT® device in patients affected by hemophilia A (HA) in Italy. Materials and Methods: An observational retrospective study was conducted in three Italian hemophilia centers. All patients with moderate or severe HA, aged ≥ 18 years, capable of having PK estimated using the myPKFiT device, and who had had a clinical visit between 1 November 2019 and 31 March 2022 were included. Differences in clinical, treatment, health resources, and cost data were assessed comparing post-PK prophylaxis with pre-PK. The incremental cost-effectiveness ratio (ICER) was estimated as cost (EUR) per bleed avoided. Results: The study enrolled 13 patients with HA. The mean annual bleeding rate decreased by -1.45 (-63.80%, p = 0.0055) after the use of myPKFiT®. Overall, the consumption of FVIII IU increased by 1.73% during follow-up compared to the period prior the use of the myPKFiT. Prophylaxis based on the myPKFiT resulted in an ICER of EUR 5099.89 per bleed avoided. Conclusions: The results of our study support the idea that the use of PK data in clinical practice can be associated with an improvement in the management of patients, as well as clinical outcomes, with a reasonable increase in costs.

Joint replacement for the management of haemophilic arthropathy in patients with inhibitors: A long-term experience at a single Haemophilia centre.

INTRODUCTION: The association between haemophilia and the so-called 'inhibitors', alloantibodies against the infused factor able to neutralize its clotting activity, is a very rare condition. Those sporadic patients suffer of an even more severe arthropathy and performing primary or revision arthroplasty become truly challenging. Literature about this topic is scarce, consisting in small case series, high rates of complications and mid-term follow-ups. AIM: The purpose of this study is the assessment of the long-term outcomes of primary and revision arthroplasty performed in a population of patients with inhibitors, the more consistent to date reported at a single haemophilia centre. METHODS: We reviewed the records of 18 patients with inhibitors (26 procedures) between 1999 and 2017, divided in two groups. Group A [primary total Knee-Hip arthroplasty (TKA-THA)]: 13 patients underwent 19TKA and 2THA; and B (revision): 5 subjects underwent 3rTKA and 2rTHA. All patients received the same haematological prophylaxis (rFVIIa). Haemophilic Joint Health score and VAS, and X-rays were recorded pre- and postoperatively. The survival rate of all primary implants was assessed. RESULTS: The median follow-up was 12.2 years (3-21) for group A, 8.6 years (4-12) for B. Few complications have been reported; the overall survival rate was 94.7% at 15 years. All patients reported satisfaction, pain reduction and improved functional ability. CONCLUSION: Primary and revision TKA/THA in haemophilic subjects and inhibitors may be nowadays considered safe and effective if performed in dedicated multidisciplinary centres. The use of continuous infusion of rFVIIa showed an adequate haemostatic effect and low rate of complications. As expected, revisions are more prone to complications compared to primary arthroplasty.

Practical considerations for nonfactor-replacement therapies in the treatment of haemophilia with inhibitors.

New therapeutic agents for haemophilia with inhibitors that are in development or already licensed are expected to provide transformative treatment options. Many of these new therapies are not based on simply replacing the missing factor; new strategies include bispecific antibody technology that mimics factor VIII coagulation function (emicizumab), and inhibition of anticoagulant proteins such as tissue factor pathway inhibitor (eg PF-06741086) and antithrombin (eg fitusiran). These agents are administered subcutaneously and should significantly reduce treatment burden and increase the ability to deliver prophylaxis for patients. Limited real-world data and validated practical guidance on these recently licensed/upcoming treatments resulted in the authors convening to discuss recommendations on their use. Emicizumab is currently the only licenced nonfactor therapy; thus, our recommendations focus on this product. Target candidates for emicizumab prophylaxis are difficult-to-treat patients with haemophilia A and inhibitors and/or venous access issues, frequent bleeds and target joints. In case of breakthrough bleeding while receiving emicizumab, patients still require treatment with bypassing agents; the adjunct treatment of choice is recombinant activated factor VII. This treatment is also recommended to prevent bleeds in patients with inhibitors undergoing surgery. Our recommendations on suitable laboratory assays and monitoring new products, as well as the benefit of patient-reported outcomes (such as pain and physical activity levels), are included. We also briefly discuss future treatment options for patients with haemophilia B and inhibitors. Although these nonfactor treatments offer great promise, further data and real-world evidence are needed.

Product type and the risk of inhibitor development in nonsevere haemophilia A patients: a case-control study.

Inhibitor development is a major complication of treatment with factor VIII concentrates in nonsevere haemophilia A. It has been suggested that plasma-derived factor VIII (FVIII) concentrates elicit fewer inhibitors than recombinant FVIII concentrates, but studies in severe haemophilia A patients have shown conflicting results. We designed a case-control study to investigate the clinical and genetic risk factors for inhibitor development in nonsevere haemophilia A patients. We investigated whether the type of FVIII concentrate was associated with inhibitor development in nonsevere haemophilia A patients. This nested case-control study includes 75 inhibitor patients and 223 controls, from a source population of the INSIGHT study, including all nonsevere haemophilia A patients (FVIII:C 2-40%) that were treated with FVIII concentrates in 33 European and one Australian centre. Cases and controls were matched for date of birth and cumulative number of exposure days (CED) to FVIII concentrate. A conditional logistic regression model was used to calculate unadjusted and adjusted odds ratios. No increased risk for inhibitor development was found for any type of FVIII concentrate; either when comparing recombinant FVIII concentrates to plasma-derived FVIII concentrates (adjusted odds ratio 0·96, 95% confidence interval (CI) 0·36-2·52) or for specific types of FVIII concentrates.

Inhibitors in haemophilia A and B: Management of bleeds, inhibitor eradication and strategies for difficult-to-treat patients.

The standard therapy for patients with haemophilia is prophylactic treatment with replacement factor VIII (FVIII) or factor IX (FIX). Patients who develop inhibitors against FVIII/FIX face an increased risk of bleeding, and the likelihood of early development of progressive arthropathy, alongside higher treatment-related costs. Bypassing agents can be used to prevent and control bleeding, as well as the recently licensed prophylaxis, emicizumab, but their efficacy is less predictable than that of factor replacement therapy. Antibody eradication, by way of immune tolerance induction (ITI), is still the preferred management strategy for treating patients with inhibitors. This approach is successful in most patients, but some are difficult to tolerise and/or are unresponsive to ITI, and they represent the most complicated patients to treat. However, there are limited clinical data and guidelines available to help guide physicians in formulating the next treatment steps in these patients. This review summarises currently available treatment options for patients with inhibitors, focussing on ITI regimens and those ITI strategies that may be used in difficult-to-treat patients. Some alternative, non-ITI approaches for inhibitor management, are also proposed.

Treatment Regimens with Bypassing Agents in Patients with Hemophilia A and Inhibitors: A Survey from the Italian Association of Hemophilia Centers (AICE).

The development of neutralizing antibodies (inhibitors) against infused factor VIII currently represents the main complication of replacement therapy in patients with severe hemophilia A. Inhibitors, indeed, particularly high-titer inhibitors (>5 BU/mL), greatly complicate the management of bleeding, exposing patients to an increased morbidity and mortality risk, thus representing a significant burden for physicians of Hemophilia Treatment Centers (HTCs). Although bypassing agents (i.e., activated prothrombin complex concentrate [APCC] and recombinant activated factor VII [rFVIIa]) are available for the treatment and prevention of bleeding in inhibitor patients, their efficacy, safety, and cost-benefit outcomes are poorly known in the long term and should be further improved. In the frame of the update of recommendations for the management of inhibitor patients by the Italian Association of Hemophilia Centers (AICE), to collect more information on real-life therapeutic approaches with bypassing agents in this setting, a survey was conducted among the Directors of the Italian HTCs. From questionnaires returned by 55% of them, data on the use of rFVIIa and APCC in children, adolescent, and adult patients with hemophilia A and inhibitors were obtained and are summarized in this article, including information about the implementation of prophylaxis with both bypassing agents, the adopted regimens, and reasons for starting, adjusting, and interrupting such a therapeutic approach.

Outcome measures for adult and pediatric hemophilia patients with inhibitors.

Recent advancements in almost all aspects of hemophilia treatment have vastly improved patient care and management, and new and emerging treatments hold the promise of further progress. However, there remains a scarcity of data on long-term outcomes in hemophilia, particularly among those patients with inhibitors, for whom no validated outcome assessment tools are currently available. At the 15th Zürich Haemophilia Forum, an expert panel reviewed the most important outcome measures in inhibitor patients and considered the challenges associated with assessing outcomes in this population. A framework for outcome assessment in inhibitor patients incorporates traditional hemophilia outcome measures, such as bleed frequency and mortality, alongside measures of health, functioning, disability, social participation, quality of life, and economic considerations. It is important to remember that inhibitor patients differ in their clinical needs, perspectives, and priorities according to age, inhibitor status, degree of joint disease, and activity levels; as a result, the relative importance of different outcome measures will change throughout an inhibitor patient's life. Challenges inherent in measuring long-term outcomes in inhibitor patients include the small number of known patients, the subjective nature of many outcome assessment tools, and the risk of overburdening patients with repeated requests to complete questionnaires or participate in studies. Therefore, there is an urgent need to reach consensus on the most important and appropriate assessment tools for measuring outcomes in this population. These tools should ideally be standardized, easily applied, and internationally applicable in order to collect and generate quality outcome data.

The bleeding score predicts clinical outcomes and replacement therapy in adults with von Willebrand disease.

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.

Emerging drugs for the treatment of hemophilia A and B.

INTRODUCTION: Replacement therapy with clotting factor concentrates is the most appropriate and effective way to treat bleedings of Hemophilia A&B to prevent chronic arthropathy. Unfortunately, the short half-life (HL) of FVIII/IX concentrates obliges the patients to receive frequent infusions, a big concern for children. The development of inhibitors in about 30-45% of hemophilia A and in 3-5% of hemophilia B patient is the major adverse event of replacement therapy. AREAS COVERED: In the last few years, new rFIX have been developed with HL. New rFVIII concentrates are displaying small increase of PK characteristics. The new bio-engineering methods allowed the production of molecules fused with Fc fragment of IgG or Albumin or linked to PEG. A new approach to improve hemostasis is represented by Mab against TFPI and small RNA interfering with Antithrombin synthesis. Another innovative drug seems to be the new bi-specific antibody which mimics FVIII function in linking FXa and FX to tenase production. EXPERT OPINION: The emerging drugs for hemophilia treatment seem to be very promising. The extended half-life will improve the adherence of patients to therapy. Accurate post-marketing surveillance studies will be necessary to check the efficacy, safety and immunogenicity of these new molecules.

Rapid rFVIIa enhanced on-demand dosing in haemophilia inhibitor patients.

Recombinant factor VII activated (rFVIIa) is a bypassing agent widely used in haemophilia A and B patients with antibodies against coagulation factors VIII or IX. When used according to the correct doses, rFVIIa may control bleeding, subclinical bleeding and rebleeding, avoiding the effect of neutralising inhibitors. Because of the fast action of the rFVIIa, haemostasis occurs promptly and enables a fast bleeding control with on-demand treatment in home or in surgical setting. Rapidity is also a distinguishing feature in preparation and injection of rFVIIa to cope the restraining times of busy patients and parents. The effective haemostatic activity of rFVIIa enables a sustained bleeding control, which is implemented with every other day (eod) administration and suited for enhanced on-demand therapy and short-term repeated infusions use of rFVIIa to prevent microhaemorrhages or rebleeding. Comprehensive appreciation of these pharmacological and pharmacodynamic' characteristics will likely be a further stimulus to the wider enhanced on-demand use of rFVIIa.

Factor VIII gene (F8) mutation and risk of inhibitor development in nonsevere hemophilia A.

Neutralizing antibodies (inhibitors) toward factor VIII form a severe complication in nonsevere hemophilia A, profoundly aggravating the bleeding pattern. Identification of high-risk patients is hampered by lack of data that take exposure days to therapeutic factor VIII concentrates into account. In the INSIGHT study, we analyzed the association between F8 mutation and inhibitor development in patients with nonsevere hemophilia A (factor VIII 2-40 IU/dL). This analysis included 1112 nonsevere hemophilia A patients from 14 centers in Europe and Australia that had genotyped at least 70% of their patients. Inhibitor risk was calculated as Kaplan-Meier incidence with cumulative number of exposure days as the time variable. During 44 800 exposure days (median, 24 exposure days per patient; interquartile range [IQR], 7-90), 59 of the 1112 patients developed an inhibitor; cumulative incidence of 5.3% (95% confidence interval [CI], 4.0-6.6) after a median of 28 exposure days (IQR, 12-71). The inhibitor risk at 50 exposure days was 6.7% (95% CI, 4.5-8.9) and at 100 exposure days the risk further increased to 13.3% (95% CI, 9.6-17.0). Among a total of 214 different F8 missense mutations 19 were associated with inhibitor development. These results emphasize the importance of F8 genotyping in nonsevere hemophilia A.

Switching treatments in haemophilia: is there a risk of inhibitor development?

Patients with haemophilia A (and their physicians) may be reluctant to switch factor VIII (FVIII) concentrates, often due to concerns about increasing the risk of inhibitors; this reluctance to switch may contribute to patients missing the clinical benefits provided by the arrival of new factor VIII products. This topic was explored at the Eleventh Zürich Haemophilia Forum. Clinical scenarios for which product switching may be cause for concern were discussed; when there is a clinical need, there are no absolute contraindications to switching, but some patients (e.g. previously untreated patients and those undergoing elective surgery) may require more careful consideration. Both patient and physician surveys indicate that the reluctance to switch, and the fear of inhibitor development, does not appear to be evidence based. The evaluation of more recent data did not support previous studies suggesting that particular products (e.g. recombinant vs. plasma-derived and full length vs. B-domain modified) may be associated with increased risk. In addition, data from three national product switches showed that switching was not associated with increased inhibitor risk, but highlighted the need for regular inhibitor testing and for a centralised, unbiased database of inhibitor incidence. To conclude, current evidence does not suggest that switching products significantly influences inhibitor development.

Anti-inhibitor coagulant complex prophylaxis in hemophilia with inhibitors.

BACKGROUND: Patients with severe hemophilia A and factor VIII inhibitors are at increased risk for serious bleeding complications and progression to end-stage joint disease. Effective strategies to prevent bleeding in such patients have not yet been established. METHODS: We enrolled patients with hemophilia A who were older than 2 years of age, had high-titer inhibitors, and used concentrates known as bypassing agents for bleeding in a prospective, randomized, crossover study comparing 6 months of anti-inhibitor coagulant complex (AICC), infused prophylactically at a target dose of 85 U per kilogram of body weight (±15%) on 3 nonconsecutive days per week, with 6 months of on-demand therapy (AICC at a target dose of 85 U per kilogram [±15%] used for bleeding episodes). The two treatment periods were separated by a 3-month washout period, during which patients received on-demand therapy for bleeding. The primary outcome was the number of bleeding episodes during each 6-month treatment period. RESULTS: Thirty-four patients underwent randomization; 26 patients completed both treatment periods and could be evaluated per protocol for the efficacy analysis. As compared with on-demand therapy, prophylaxis was associated with a 62% reduction in all bleeding episodes (P<0.001), a 61% reduction in hemarthroses (P<0.001), and a 72% reduction in target-joint bleeding (≥3 hemarthroses in a single joint during a 6-month treatment period) (P<0.001). Thirty-three randomly assigned patients received at least one infusion of the study drug and were evaluated for safety. One patient had an allergic reaction to the study drug. CONCLUSIONS: AICC prophylaxis at the dosage evaluated significantly and safely decreased the frequency of joint and other bleeding events in patients with severe hemophilia A and factor VIII inhibitors. (Funded by Baxter BioScience; Pro-FEIBA ClinicalTrials.gov number, NCT00221195.).

Safety and pharmacokinetics of a novel recombinant fusion protein linking coagulation factor IX with albumin (rIX-FP) in hemophilia B patients.

A recombinant fusion protein linking coagulation factor IX (FIX) with human albumin (rIX-FP) has been developed to facilitate hemophilia B treatment by less frequent FIX dosing. This first-in-human dose-escalation trial in 25 previously treated subjects with hemophilia B (FIX ≤ 2 IU/dL) examined the safety and pharmacokinetics of 25, 50, and 75 IU/kg rIX-FP. Patients in the 50-IU/kg cohort underwent a comparative pharmacokinetics assessment with their previous FIX product (plasma-derived or recombinant). No allergic reactions or inhibitors were observed. Four mild, possibly treatment-related adverse events were reported. In the 50-IU/kg cohort (13 subjects), the mean half-life of rIX-FP was 92 hours, more than 5 times longer than the subjects' previous FIX product. After 25 or 50 IU/kg rIX-FP administration, the baseline-corrected mean FIX activity remained elevated at day 7 (7.4 IU/dL and 13.4 IU/dL, respectively) and day 14 (2.5 IU/dL and 5.5 IU/dL, respectively). The incremental recovery of rIX-FP was higher than both recombinant and plasma-derived FIX (1.4 vs 0.95 and 1.1 IU/dL per IU/kg, respectively). These results demonstrated both the safety and improved pharmacokinetics of rIX-FP, thus indicating this new product with extended half-life as possibly able to control and prevent bleeding with less frequent injection.

Innovative approach for improved rFVIII concentrate.

The development of a new recombinant factor VIII was designed and implemented to answer a number of unmet needs of patients affected by hemophilia A. Turoctocog alfa is bioengineered in a specific Chinese hamster ovary clone to present translational and posttranslational characteristics (sulphation, glycosylation) biosimilar to natural circulating forms of FVIII, with the aim to devoid any minimal change which may impact immunogenicity and antigenicity of recombinant protein. Both producer cell line and media are maintained free of any animal or human plasma derivative. Downstream processes of purification are performed by five steps (immunoaffinity chromatography, ion-exchange chromatography, virus inactivation by means of solvent-detergent treatment and nanofiltration, and to end with gel filtration), to provide the best possible margin of safety from known and unknown infectious agents. Large clinical trials seem to confirm the expectations placed in Turoctocog alfa in terms of high quality and safety of recombinant FVIII toward the goal of overcoming actual and future challenges of hemophilia therapy.

Angiogenesis is increased in advanced haemophilic joint disease and characterised by normal pericyte coverage.

BACKGROUND: Repeated intra-articular bleedings in patients with haemophilia results in a crippling arthropathy for which no specific treatment is currently available. Recent studies have shown that neoangiogenesis is involved in the pathologic process. The aim of this study was to determine whether angiogenesis is dysregulated in haemophilic joint disease (HJD). METHODS: Synovial tissue and synovial fluid were collected from patients with severe haemophilia undergoing knee or hip replacement and from a control group consisting of non-haemophilic patients undergoing diagnostic procedures. In a second set of patients, blood samples were collected in patients with mild, moderate and severe haemophilia A when free from current bleeding. Analysis of microvascular density, vascular endothelial growth factor (VEGF) expression and pericyte coverage was performed by immunofluorescence. Analyses of VEGF concentrations in plasma, platelet lysates and synovial fluid were performed by ELISA. RESULTS: Microvascular density and VEGF expression were significantly increased in synovial tissue from haemophilic patients compared with controls (P = 0.005 and P = 0.02, respectively). There was no difference in pericyte coverage of synovial vessels or levels of VEGF in plasma, platelet lysates or synovial fluid. CONCLUSIONS: Angiogenesis observed as synovial microvascular density, and VEGF expression is increased in HJD. As pericyte coverage was similar in synovial vessels from haemophilic and non-haemophilic patients, we assume that the vessels were mature, suggesting that the rate of new vessel formation is low in the chronic phase of haemophilic joint disease.

Systematic review of the role of FVIII concentrates in inhibitor development in previously untreated patients with severe hemophilia a: a 2013 update.

Nowadays, patients with hemophilia A receive a high standard of care; therefore, the most challenging complication of factor VIII (FVIII) replacement therapy has become the development of FVIII inhibitors, which render the concentrate infusion ineffective and expose patients to an increased risk of morbidity and mortality. Among environmental risk factors influencing inhibitor development, the type of FVIII products has always drawn the attention of investigators. Conflicting results are reported in the literature concerning rates of inhibitor development after either plasma-derived or recombinant FVIII concentrates. To help elucidate this controversial issue, we have performed a systematic review and meta-analysis of prospective studies evaluating the incidence of inhibitors in previously untreated patients with severe hemophilia A receiving plasma-derived or recombinant FVIII products. The quality of the studies was assessed using the Newcastle-Ottawa Scale (NOS), the STrenghtening the Reporting of OBservational studies in Epidemiology and an ad hoc quality score. Overall, 28 prospective studies, including 1,421 patients with hemophilia A, fulfilled our selection criteria and were included in the systematic review. No statistically significant differences were observed in the inhibitor incidence between plasma-derived and recombinant FVIII concentrates considering all (weighted means: 23%, 95% CI: 15-33% vs. 29%, 95% CI: 26-32%) and high titer (16%, 95% CI: 10-26% vs. 18%, 95% CI: 15-21%) inhibitors. Similarly, no significant differences were found in the inhibitor incidence among the different classes of recombinant products. In conclusion, the results of our meta-analysis show that the different types of FVIII products are not associated with different risks of inhibitor development.

Bioequivalence of recombinant factor VIII products: a position paper from the Italian Association of Hemophilia Centers.

Over the last three decades, the continuous evolution of recombinant factor VIII (rFVIII) concentrates for replacement treatment of hemophilia A, including recent extended half-life products, implies that patients may switch from one product to another, technologically more advanced, with the aim of improving treatment efficacy, safety, management and, ultimately, quality of life. In this scenario, the issues of bioequivalence of rFVIII products and the clinical implications of their interchangeability are keenly debated, in particular when economic reasons or purchasing systems influence product availability and choices. Although sharing the same Anatomical Therapeutic Chemical (ATC) level, rFVIII concentrates, as other biological products, show relevant differences in terms of molecular structure, source and manufacturing process, which make them unique products, recognized as new active substances by regulatory agencies. Moreover, data from clinical trials with both standard and extended half-life products clearly document the large inter-patient variability of pharmacokinetic profiles after administering the same dose of the same product; in cross-over evaluations, even when mean values are comparable, some patients show better patterns with one product or with the comparator one. Pharmacokinetic assessment thus reflects the response to a specific product in the individual patient, with his genetic determinants, only partially identified, affecting the behavior of exogenous FVIII. These concepts, consistent with the currently recommended approach of personalization of prophylaxis, are discussed in this position paper endorsed by the Italian Association of Hemophilia Centers (AICE), highlighting that ATC or other available classifications do not completely consider differences between drugs and innovations and that substitutions of rFVIII products will not invariably ensure the previously achieved clinical outcomes or generate benefits for all patients.