Association of peak factor VIII levels and area under the curve with bleeding in patients with haemophilia A on every third day pharmacokinetic-guided prophylaxis.

INTRODUCTION: We previously showed that pharmacokinetic-guided prophylaxis (PKP) allows the dosing interval to be extended while maintaining a specific trough level. However, the associations of peak factor VIII (FVIII) levels and area under the curve (AUC) with breakthrough bleeding have not been investigated. AIM: The aim of this study was to analyse data from the PKP arm to determine whether peak FVIII levels, AUC and time with FVIII levels in a haemostatically effective range are independent predictors of bleeding during prophylaxis. METHODS: Post hoc analysis of the association of FVIII levels and AUC with annualized bleeding rate in 34 patients on PKP. RESULTS: During 1 year of PKP, 131 bleeding episodes occurred in 24/34 patients. Average peak FVIII levels ranged from 24 to 168 IU dL(-1) , with higher values associated with a decreased risk for all bleeding (joint and non-joint; P < 0.01) and joint bleeding (P < 0.01). Following rFVIII infusion, median percent of time spent with FVIII levels >20 IU dL(-1) was 22%; median AUC was 1363. Both values were significantly associated with a lower ABR when targeting a 1% trough at 72 h. CONCLUSION: When PKP was administered every third day, higher peak FVIII levels, higher AUC and more time spent per week with FVIII levels >20 IU dL(-1) provided increased protection from joint and non-joint bleeding. These data highlight the potential impact of variability in individual pharmacokinetic and bleeding risk and support the need for high peak levels and AUC in some patients treated every third day. The findings do not necessarily apply to alternate-day or other prophylactic dosing regimens.

Pro- and anticoagulant factors facilitate thrombin generation and balance the haemostatic response to FEIBA(®) in prophylactic therapy.

INTRODUCTION: FEIBA(®) consists of zymogens and traces of activated forms of procoagulant factors II, VII, IX, X, anticoagulants protein C and TFPI, and small amounts of cofactors FV, FVIII and protein S, in a balanced ratio. As shown previously, FII-FXa complex plays a key role in FEIBA's mode of action (MoA). METHODS: Thrombin generation (TG) was measured by spiking coagulation factors, cofactors and inhibitors to high titer FVIII inhibitor plasma, and in plasma samples from patients in a phase 3 clinical study evaluating the safety and efficacy of FEIBA prophylaxis in haemophilia A patients with inhibitors. RESULTS: Increasing the FXa/FII ratio improved TG, while adding coagulation enzyme components had a negligible effect. Adding FX, FIX, and FVII increased the peak thrombin and decreased the lag time. The presence of FV and phospholipids led to faster TG, while protein C and protein S reduced the amount of peak thrombin. TFPI appeared to have no effect. Patients on prophylaxis with FEIBA(®) showed higher peak thrombin and AUC with elevated FII, FX, FIX, FVIIa, and protein C levels, and experienced significantly less bleeding episodes than those receiving on-demand treatment. CONCLUSION: These experiments showed that although the FII-FXa complex induced immediate thrombin formation on the activated platelet surface, other procoagulant components of FEIBA were necessary to achieve an optimal thrombin burst. The presence of the pro- and anti-coagulants in FEIBA provides a haemostatic balance, and is thus expected to prevent thrombotic events. Recent clinical data verified the postulated MoA of FEIBA in prophylaxis treatment.

The role of previously untreated patient studies in understanding the development of FVIII inhibitors.

Development of inhibitors against factor VIII (FVIII), the major complication of haemophilia A treatment today, is influenced by multiple factors. Genetic (F8 mutation, family history, ethnicity, polymorphisms in immune modulating genes) and non-genetic (intensive exposure to FVIII, presence of pro-inflammatory signals as might occur with large bleeds, infections, surgery, or other immune stimulants [e.g. vaccines]) risk factors as well as their complex inter-relationships contribute to the inhibitor risk profile of haemophilia patients, particularly in the previously untreated patient (PUP) population. Studies in PUPs have been fundamental to furthering the understanding of FVIII inhibitor development, as well as discovering previously unappreciated risk factors. The multi-factorial nature of inhibitor development makes it difficult to ascertain the contribution of FVIII products in inhibitor development through individual PUP studies. Sufficiently powered studies of large cohorts may overcome these limitations but interpretations should be conducted cautiously. Proper design and implementation of PUP safety studies will become even more important with the introduction of new molecules, such as extended half-life or human cell-line derived FVIII that propose reduced immunogenicity. Despite these difficulties, carefully performed clinical studies in PUPs may provide important insights into the natural history of the immune response to FVIII and may suggest targets for intervention to reduce immunogenicity.

Efficacy and safety of OBI-1, an antihaemophilic factor VIII (recombinant), porcine sequence, in subjects with acquired haemophilia A.

Acquired haemophilia A (AHA) is a rare bleeding disorder caused by autoantibodies against human factor VIII (hFVIII). OBI-1 is an investigational, B-domain deleted, recombinant FVIII, porcine sequence, with low cross-reactivity to anti-hFVIII antibodies. Efficacy can be monitored with FVIII activity levels in addition to clinical assessments. This prospective, open label, phase 2/3 study was designed to evaluate the efficacy of OBI-1 treatment for bleeding episodes in subjects with AHA. After an initial dose of 200 U kg(-1) , OBI-1 was titrated to maintain target FVIII activity levels, in correlation with clinical assessments, throughout the treatment phase. All 28 subjects with AHA had a positive response to OBI-1 treatment 24 h after initiation despite inhibition of FVIII activity levels immediately after infusion in 10 subjects with baseline anti-porcine FVIII inhibitors. Control of the qualifying bleed was ultimately achieved in 24 of 28 subjects. No related serious adverse events, thrombotic events, allergic reactions or thrombocytopaenia occurred. The results of this study indicate that OBI-1 is safe and effective in treating bleeding episodes in subjects with AHA. The ability to safely and effectively titrate dosing based on FVIII activity levels in this study demonstrates that OBI-1 fulfils the unmet medical need to monitor the key coagulation parameter in AHA patients.

The burden of bleeding in haemophilia: is one bleed too many?

Joint bleeding is the hallmark of haemophilia. Increasingly, the pain, restricted movement and anxiety provoked by even a single haemarthrosis are concerns for patients, families and treating physicians. The aims of this study were to determine whether the current paradigm for prophylaxis requires a shift in focus from reducing the frequency of bleeding episodes to a goal of zero bleeding and to review and discuss the published data from in vitro and animal experiments and clinical studies in patients with haemophilia that describe the impact of joint bleeding. More than two to three bleeding into the same joint may cause irreversible and progressive structural damage that compromise health-related quality of life (HRQoL). A goal of zero bleeding episodes - or as close to zero as possible - is key to enhancing joint health and HRQoL in children and adults with haemophilia. Achieving this goal requires individualized, outcome-based, multidisciplinary care to maximize prophylactic efficacy without increasing overall health care costs.

Randomized comparison of prophylaxis and on-demand regimens with FEIBA NF in the treatment of haemophilia A and B with inhibitors.

Factor replacement therapy for the treatment of moderate to severe haemophilia A and B can be complicated by the production of inhibitory alloantibodies to factor VIII (FVIII) or factor IX. Treatment with the nanofiltered anti-inhibitor coagulant complex, Factor Eight Inhibitor Bypassing Activity (FEIBA NF), is a key therapeutic option for controlling acute haemorrhages in patients with high-titre inhibitors or low-titre inhibitors refractory to replacement therapy. Given the high risk for morbidity and mortality in haemophilia patients with inhibitors to FVIII or FIX, we conducted this Phase 3 prospective study to evaluate whether prophylaxis with FEIBA NF is a safe and effective treatment option. Over a 1-year period, 17 subjects were treated prophylactically (85 ± 15 U kg(-1) every other day) while 19 subjects were treated on demand. The median (IQR) annualized bleeding rate (ABR) during prophylaxis was 7.9 (8.1), compared to 28.7 (32.3) during on-demand treatment, which amounts to a 72.5% reduction and a statistically significant difference in ABRs between arms (P = 0.0003). Three (17.6%) subjects (ITT) on prophylaxis experienced no bleeding episodes, whereas none treated on demand were bleeding episode-free. Total utilization of FEIBA NF for the treatment of bleeding episodes was significantly higher during on-demand therapy than prophylaxis (P = 0.0067). There were no differences in the rates of related adverse events between arms. This study demonstrates that FEIBA prophylaxis significantly reduces all types of bleeding compared with on-demand treatment, and the safety of prophylaxis is comparable to that of on-demand treatment.

Development of novel treatment options for patients with haemophilia.

UNLABELLED: Treatment of haemophilia has vastly improved over the last years, but many needs are still unmet. Baxter is continuously pursuing the aim to provide new therapeutic options to patients with haemophilia and to their treating physicians. In fact, there are several opportunities to improve existing therapies, e.g., by new indications for existing products, the introduction of new products, and by novel therapeutic approaches other than factor replacement. Among these, Baxter is working on a number of innovations, such as pharmacokinetics-tailored factor VIII prophylaxis, bypassing agent prophylaxis with FEIBA in inhibitor patients, development of a longer acting pegylated recombinant FVIII, a new recombinant factor IX, a new recombinant factor FVIIa, the first recombinant von Willebrand factor, recombinant ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) as well as gene therapy to cure haemophilia B. CONCLUSION: Baxter is truly committed to the benefit for the patient, and therefore engaged in providing a more and more individualized treatment, in increasing efficiency of current products, in developing new products and new approaches with added value.

Trends in bleeding patterns during prophylaxis for severe haemophilia: observations from a series of prospective clinical trials.

Replacement therapy or prophylaxis, has become the standard of care for the treatment of severe haemophilia A. To describe bleeding patterns in children, adolescents and adults on prophylaxis and their observed relationships to times of infusion (during the week and during the day) as well as season of the year. Data from Advate pre-licensure prospective clinical trials from 145 patients with factor VIII (FVIII) <1%, were used. All patients underwent a 48-h pharmacokinetic study. The 10-65 year group had ≥ 75 exposure days on fixed prophylaxis (25-40 IU kg(-1) 3-4x per week). Prophylaxis was not fixed but similar for 1-6 year olds. Bleeding patterns were analysed. Overall, 700 bleeds were observed in 110/145 patients. All were treated with prophylaxis, mean dose 108 IU kg(-1) week(-1) in on average 2.9 infusions (1-6 years), 86 IU kg (-1) week(-1) in 2.7 infusions (10-17 years), and 75 IU kg (-1) week(-1) in 2.6 infusions (18-65 years), respectively. On prophylaxis, median total bleeds per year were low at 3.1 for patients aged 1-6 years, 3.3 for those aged 10-17 years and 2.1 for patients aged 18-65 years. Patients aged 1-6 years had predominantly soft tissue bleeds (79%). Incidence of joint bleeding was not associated with season, but was significantly lower in patients who infused FVIII in the mornings: median 0 per year (IQR 0.0-0.4) compared to those who infused later [median 1.8 per year (IQR 0.0-5.2)]. Older patients predominantly experienced joint bleeds (50% and 62%, respectively). More joint bleeds occurred during the summer [43 and 46% respectively, (P < 0.01)]. Bleeding patterns in patients on prophylaxis varied according to age. In addition, the 10-65 year olds showed increased bleeding during the summer. After confirmation in prospective studies, this information may be used to improve tailoring of prophylactic treatment.

The relative burden of haemophilia A and the impact of target joint development on health-related quality of life: results from the ADVATE Post-Authorization Safety Surveillance (PASS) study.

Studies with haemophilia A (HA) patients have shown burden in health-related quality of life (HRQOL) when compared with general population norms. In the current study, HA patients' SF-36v2 health survey scores were compared with general population norms and to patients with other chronic conditions. The impact of target joints (TJs) on HRQOL was also examined. The sample was a subset of HA patients enrolled in the Post-Authorization Safety Surveillance (PASS) programme: a prospective open-label study in which ADVATE [Antihaemophilic Factor (Recombinant), Plasma/Albumin-Free Method] was prescribed. A total of 205 patients who were ≥ 18 years old and had SF-36v2 baseline scores were selected for this study. To measure the burden of HA on HRQOL, manova analyses compared these SF-36v2 scores to age- and gender-matched general population US and EU norms and to patients from other chronic condition groups. manova and correlational analyses examined the relations among TJ, age and SF-36v2 scores. Comparisons with general population norms confirm that HA negatively impacts physical, but not mental, HRQOL. Comparison with other chronic conditions shows the physical burden of HA is greater than for chronic back pain but similar to diabetes and rheumatoid arthritis, while the mental burden of HA is less than for all three patient groups. The presence of TJs was negatively associated with physical HRQOL, although this association was much larger for older patients (45+ years) than for younger ones. Physical, but not mental, HRQOL is diminished in HA patients. Target joints are associated with lower physical HRQOL, although this effect is moderated by age.

Postauthorization safety surveillance of ADVATE [antihaemophilic factor (recombinant), plasma/albumin-free method] demonstrates efficacy, safety and low-risk for immunogenicity in routine clinical practice.

Postauthorization safety surveillance of factor VIII (FVIII) concentrates is essential for assessing rare adverse event incidence. We determined safety and efficacy of ADVATE [antihaemophilic factor (recombinant), plasma/albumin-free method, (rAHF-PFM)] during routine clinical practice. Subjects with differing haemophilia A severities and medical histories were monitored during 12 months of prophylactic and/or on-demand therapy. Among 408 evaluable subjects, 386 (95%) received excellent/good efficacy ratings for all on-demand assessments; the corresponding number for subjects with previous FVIII inhibitors was 36/41 (88%). Among 276 evaluable subjects receiving prophylaxis continuously in the study, 255 (92%) had excellent/good ratings for all prophylactic assessments; the corresponding number for subjects with previous FVIII inhibitors was 41/46 (89%). Efficacy of surgical prophylaxis was excellent/good in 16/16 evaluable procedures. Among previously treated patients (PTPs) with >50 exposure days (EDs) and FVIII≤2%, three (0.75%) developed low-titre inhibitors. Two of these subjects had a positive inhibitor history; thus, the incidence of de novo inhibitor formation in PTPs with FVIII≤2% and no inhibitor history was 1/348 (0.29%; 95% CI, 0.01-1.59%). A PTP with moderate haemophilia developed a low-titre inhibitor. High-titre inhibitors were reported in a PTP with mild disease (following surgery), a previously untreated patient (PUP) with moderate disease (following surgery) and a PUP with severe disease. The favourable benefit/risk profile of rAHF-PFM previously documented in prospective clinical trials has been extended to include a broader range of haemophilia patients, many of whom would have been ineligible for registration studies.

Comparative pharmacokinetics of plasma- and albumin-free recombinant factor VIII in children and adults: the influence of blood sampling schedule on observed age-related differences and implications for dose tailoring.

BACKGROUND: Dose tailoring of coagulation factors requires reliably estimated and reproducible pharmacokinetics (PK) in the individual patient. OBJECTIVES: To investigate the contribution of both biological and methodological factors to the observed variability of factor VIII (FVIII) PK, with the focus on differences between children and adults, and to examine the implications for dosing. PATIENTS: Data from 52 1-6-year-old and 100 10-65-year-old patients with hemophilia A (FVIII < or = 2 IU dL(-1)) in three clinical studies were included. RESULTS: In vivo recovery was lower, weight-adjusted clearance was higher and FVIII half-life was on average shorter in children than in adults. However, a reduced blood sampling schedule for children was estimated to account for up to one half of the total observed differences. Intrapatient variance in PK was smaller than interpatient variance in 10-65-year-olds. Age and ratio of actual to ideal weight only showed weak relationships with PK parameters. Variance in PK caused large variance in the calculated dose required to maintain a target FVIII trough level during prophylactic treatment. CONCLUSION: Differences in blood sampling schedules should be taken into account when results from different PK studies are compared. However, even with this consideration, PK cannot be predicted from observable patient characteristics but must be determined for the individual. Because the influence of reducing the blood sampling was minor in comparison to the true variance between patients, a reduced blood sampling protocol can be used. Low intrapatient variability supports the use of PK measurements for dose tailoring of FVIII.

Factor VIII requirement to maintain a target plasma level in the prophylactic treatment of severe hemophilia A: influences of variance in pharmacokinetics and treatment regimens.

BACKGROUND: Prophylactic factor (F)VIII has been shown to reduce bleeds and arthropathy in patients with severe hemophilia A. OBJECTIVES: Assuming that the trough FVIII level is an important determinant of the efficacy of prophylaxis, this paper addresses the effect of the inter-patient variability in pharmacokinetics and different dosing regimens on trough levels. METHODS: Simulations used FVIII half-lives and in vivo recoveries (IVR), observed during clinical trials with Advate [Antihemophilic Factor (Recombinant), Plasma/Albumin-Free Method], and commonly used prophylactic regimens to calculate their effect on FVIII levels during prophylaxis. RESULTS AND CONCLUSIONS: Half-life and dose frequency had a larger effect on trough FVIII and time per week with FVIII<1 IU dL(-1) than IVR and infused dose per kg. The combined effect of these parameters resulted in substantial inter-patient variability in the amount of FVIII required to sustain a desired trough level. Prophylactic regimens based on Monday, Wednesday, Friday dosing were less cost effective in maintaining a desired trough level throughout the week. Dose escalation on Friday to cover the weekend would require potentially harmful doses of FVIII in many patients, especially in young children where more than 50% would require a Friday dose of over 100 IU kg(-1) and some would require more than 400 IU kg(-1). Knowledge of individual patients' half-lives and alteration of frequency of infusions may allow the more cost-effective use of FVIII and potentially expand access to prophylaxis to a greater number of patients, especially in regions where healthcare resources are scarce.

Development of a plasma- and albumin-free recombinant von Willebrand factor.

Baxter has developed a recombinant therapy for treating von Willebrand's disease. Recombinant VWF is co-expressed with the rFVIII in CHO cells used to produce the rFVIII product Advate. This rVWF is used as a drug component for a rVWF-rFVIII complex drug product. CHO cells produce partially processed and partially un-processed rVWF still containing the pro-peptide. In order to make a consistent preparation containing mature and processed rVWF only rVWF is exposed to recombinant furin to remove the pro-peptide. Recombinant VWF and furin are produced under serum- and protein-free conditions. It is highly purified by a series of chromatographic steps and formulated in a protein-free buffer and has a homogeneous multimer distribution. The specific activity is higher in rVWF than in commercial plasma-derived VWF-FVIII complex products. SDS agarose electrophoretic analysis shows the presence of ultra-high molecular weight multimers. The FVIII-binding capacity and affinity of rVWF to FVIII is comparable to VWF in plasma. Carbohydrate analysis shows an intact glycosylation pattern. Recombinant VWF binds to collagen and promotes platelet adhesion under shear stress. It stabilizes endogenous FVIII in VWF-deficient knock-out mice as seen by a secondary rise in murine FVIII.

Emerging clinical concerns in the ageing haemophilia patient.

The availability of safe replacement clotting factor concentrates together with effective antiviral drugs to treat human immunodeficiency and hepatitis C viruses and the provision of care at designated haemophilia treatment centres have resulted in a new phenomenon in haemophilia management - the ageing patient. Today, increasing numbers of persons with haemophilia (PWH) are middle-aged and older, and they face the same age-related health issues as the general population. The impact of these risks on PWH is unclear, however, and there is a paucity of information about how to manage comorbidities in this patient population. This review focuses on five comorbidities that uniquely affect older PWH: cardiovascular disease, liver disease, cancer, renal disease and joint disease. Available research is summarized and potential management approaches are suggested.

Cost minimization analysis to compare activated prothrombin complex concentrate (APCC) and recombinant factor VIIa for haemophilia patients with inhibitors undergoing major orthopaedic surgeries.

Benefits of bypassing agents for maintaining haemostasis in major surgeries have been described in the literature; however, their use has a substantial economic impact. This study assessed the cost of FEIBA, an activated prothrombin complex concentrate and recombinant factor VIIa (rFVIIa) when used in inhibitor patients undergoing major surgeries. After reviewing published literature, a cost minimization model was developed describing dosing regimens recommended and used during major surgeries for FEIBA (pre-operative: 75-100 U kg(-1); postoperative: 75-100 U kg(-1) q 8-12 h days 1-5 and 75-100 U kg(-1) q 12 h days 6-14) and rFVIIa (pre-operative: 90 microg kg(-1); intra-operative: 90 microg kg(-1) q 2 h; postoperative: 90 microg kg(-1) q 2-4 h days 1-5 and 90 microg kg(-1) q 6 h days 6-14). Using a 75 kg patient and US prices, total drug cost was calculated for three scenarios: use of FEIBA or rFVIIa alone and a third case combining rFVIIa pre- and intra-operative and FEIBA throughout a 14-day postoperative period. Dosage amounts of modelled bypassing agents were similar to cases in the literature. Using FEIBA instead of rFVIIa would decrease total drug cost by >50% and save over $400,000 per surgery. Sequential use of both bypassing agents would increase total drug cost by 9% when compared with FEIBA alone, but would remain >40% lower than rFVIIa alone. Univariate sensitivity analyses confirmed robustness of results. As large amounts of bypassing agents are necessary for patients with inhibitors to undergo major surgeries, cost is a major consideration. Use of FEIBA alone or in combination with rFVIIa has emerged as a cost-saving approach.

Break-through bleeding in relation to predicted factor VIII levels in patients receiving prophylactic treatment for severe hemophilia A.

BACKGROUND: The role of prophylactic factor VIII (FVIII) to decrease hemophilic bleeding and arthropathy is well established. The rationale for this strategy is to convert patients with severe hemophilia A to a moderate clinical phenotype by reducing time spent with a FVIII level <1 IU dL(-1). Studies to date, however, have not demonstrated a strong link between FVIII level and the bleeding rate. OBJECTIVES: To assess the effect of FVIII level on break-through bleeding in patients with severe hemophilia A on prophylaxis. PATIENTS/METHODS: This study analysed data from 44 patients aged 1-6 and 99 patients aged 10-65 years with severe hemophilia A (FVIII <1 IU dL(-1)) who were treated with prophylactic FVIII as part of clinical studies assessing pharmacokinetics, safety and efficacy of a recombinant FVIII (Advate). Each patient had pharmacokinetic measurements and FVIII infusions recorded, and these were used to calculate time spent with a FVIII below 1, 2 and 5 IU dL(-1). RESULTS: The data demonstrate that increasing time with a FVIII below 1 IU dL(-1) is associated with increased total bleeds and hemarthroses. Lack of adherence to the intended frequency of FVIII infusion was the most important determinant of low FVIII and increased bleeding. In children aged 1-6 years, the rate of bleeding was also influenced by FVIII half-life and clearance. CONCLUSIONS: These data have important implications for the management of patients with severe hemophilia.