Implications of coagulation factor VIII and IX pharmacokinetics in the prophylactic treatment of haemophilia

Obesity in the global haemophilia population: prevalence, implications and expert opinions for weight management

Overweight and obesity may carry a significant disease burden for patients with haemophilia (PWH), who experience reduced mobility due to joint inflammation, muscle dysfunction and haemophilic arthropathy. This review aimed to define the prevalence and clinical impact of overweight/obesity in the global population of PWH. A detailed literature search pertaining to overweight/obesity in haemophilia in the last 15 years (2003-2018) was conducted, followed by a meta-analysis of epidemiological data. The estimated pooled prevalence of overweight/obesity in European and North American PWH was 31%. Excess weight in PWH is associated with a decreased range in motion of joints, accelerated loss of joint mobility and increase in chronic pain. Additionally, the cumulative disease burden of obesity and haemophilia may impact the requirement for joint surgery, occurrence of perioperative complications and the prevalence of anxiety and depression that associates with chronic illness. Best practice guidelines for obesity prevention and weight management, based on multidisciplinary expert perspectives, are considered for adult and paediatric PWH. Recommendations in the haemophilia context emphasize the importance of patient education and tailoring engagement in physical activity to avoid the risk of traumatic bleeding.

Optimizing bleed prevention throughout the lifespan: Womb to Tomb

The focus of care providers, patients and families is the ability to tailor care for persons with haemophilia (PWH) across the lifespan. Care requires knowledge of the bleeding disorder and age-related complications, risk of therapeutic interventions, and evaluation of individual characteristics that contribute to outcomes. The ultimate goal is to live a normal life without the burden of bleeding, for PWH and carriers. A wide range of therapeutic options is required to achieve personalized care. Over the last decade, substantial therapeutic advantages have been achieved in the treatment of haemophilia that include the development of a robust array of factor concentrates, novel haemostatic agents, and increased knowledge and awareness of disease associated outcomes and risk factors. Significant strides on the road to accessible gene therapy have been realized. This increased range of therapeutic modalities provides options for development and implementation of care plans for each patient at each stage of life that are more flexible compared to prior care regimens. Paradigms for management of haemophilia are changing. As a community, we must work together to use these resources wisely, to learn from outcomes with new therapies and diagnostic tools, to assure all patients can achieve improved care and outcomes regardless of disease state or country of origin.

[Efficacy of short-term full-dose prophylaxis in adult Chinese patients with severe hemophilia A]

OBJECTIVE

To investigate the efficacy of short-term full-dose prophylaxis in adult Chinese patients with severe hemophilia A.

METHODS

Thirteen adult Chinese patients with severe hemophilia A receiving on-demand or low-dose prophylaxis underwent ultrasound examination of the target joints and evaluation of Hemophilia Joint Health Score (HJHS). The data of annual bleeding episodes in the period of on-demand or low-dose prophylaxis were collected retrospectively from the patients, and the changes in bleeding and joint condition (ultrasound findings of the target joints and HJHS) were observed during short-term full-dose prophylaxis. The activity intensity of the patients was assessed using the IPAQ questionnaire, and the 72 h FⅧ trough activity was measured during full-dose prophylaxis.

RESULTS

The median age of the 13 patients was 26.0 (20.5-29.0) years. For full-dose prophylaxis, the patients received a median therapeutic dose of 31.0 (29.1-33.0) IU/kg, administered for 3 times per week; the median 72 h FⅧ trough activity of patients was 1.7% (1.3-3.4%). During the follow-up period for 3 months, the annual bleeding rates (ABR) and annual joint bleeding rates (AJBR) decreased significantly in all the patients (P=0.001 and 0.001, respectively), but zero bleeding was achieved in only 4 patients (30.8%) and zero joint bleeding in 7 patients (53.8%); 9 patients (69.2%) still experienced breakthrough bleeding. The damage severity of target joints assessed by ultrasound and HJHS in 6 patients (46.2%)was worse than before and no obvious progression of target joints damage was found in 7 patients (53.8%). Compared with the patients without progression, the patients with worsened joint damage had poorer baseline joint condition, higher bleeding frequencies before and during the follow-up, a higher intensity of physical activity, and a lower baseline FⅧ activity.

CONCLUSIONS

At present, although short-term full-dose prophylaxis can significantly reduce the bleeding and partially prevent the progression of joint damage, it is not yet possible to achieve the goal of zero bleeding for all adult patients with severe hemophilia A in China, nor can it completely prevent further joint damage. For adult patients with different clinical bleeding phenotypes, joint conditions and physical activity intensity, individualized therapy involving additional evaluation methods should be implemented, and physiotherapy and surgical intervention can be considered when necessary.

Relative and Absolute Bioavailability Study of Emicizumab to Bridge Drug Products and Subcutaneous Injection Sites in Healthy Volunteers

Emicizumab (ACE910) is a bispecific antibody that is a novel, subcutaneously injectable treatment for patients with hemophilia A. This study assessed the relative bioavailability of emicizumab between old and new drug products (DPs) and among 3 commonly used subcutaneous injection sites (abdomen, upper arm, and thigh), together with its absolute bioavailability in healthy volunteers. Forty‐eight healthy volunteers were randomized into 4 groups to receive a single subcutaneous injection of 1 mg/kg with the old or new DP, and another 12 volunteers each received a single, 90‐minute, intravenous infusion of 0.25 mg/kg with the new DP. Similar pharmacokinetic profiles were observed between the DPs, with geometric mean ratios of 1.199 (90% confidence interval [CI] 1.060‐1.355) for the maximum plasma concentration and 1.083 (90% CI 0.920‐1.275) for area under the plasma concentration‐time curve extrapolated to infinity. The geometric mean ratios of maximum plasma concentration and area under the plasma concentration‐time curve extrapolated to infinity for upper arm versus abdomen were 0.823 (90% CI 0.718‐0.943) and 0.926 (90% CI 0.814‐1.053), respectively, and those for thigh versus abdomen were 1.168 (90% CI 1.030‐1.324) and 1.073 (90% CI 0.969‐1.189), respectively. Absolute bioavailability ranged from 80.4% to 93.1%. These results suggested that no emicizumab dose adjustment would be needed when switching the DPs or injecting to different sites interchangeably and that emicizumab injected subcutaneously is highly bioavailable.

A Pharmacometric Approach to Substitute for a Conventional Dose-Finding Study in Rare Diseases: Example of Phase III Dose Selection for Emicizumab in Hemophilia A

BACKGROUND

Emicizumab (ACE910) is a bispecific antibody mimicking the cofactor function of activated coagulation factor VIII. In phase I-I/II studies, emicizumab reduced the bleeding frequency in patients with severe hemophilia A, regardless of the presence of factor VIII inhibitors, at once-weekly subcutaneous doses of 0.3, 1, and 3 mg/kg.

METHODS

Using the phase I-I/II study data, population pharmacokinetic and repeated time-to-event (RTTE) modeling were performed to quantitatively characterize the relationship between the pharmacokinetics of emicizumab and reduction in bleeding frequency. Simulations were then performed to identify the minimal exposure expected to achieve zero bleeding events for 1 year in at least 50% of patients and to select the dosing regimens to be tested in phase III studies.

RESULTS

The RTTE model adequately predicted the bleeding onset over time as a function of plasma emicizumab concentration. Simulations suggested that plasma emicizumab concentrations of ≥  45 μg/mL should result in zero bleeding events for 1 year in at least 50% of patients. This efficacious exposure provided the basis for selecting previously untested dosing regimens of 1.5 mg/kg once weekly, 3 mg/kg every 2 weeks, and 6 mg/kg every 4 weeks for phase III studies.

CONCLUSIONS

A pharmacometric approach guided the phase III dose selection of emicizumab in hemophilia A, without conducting a conventional dose-finding study. Phase III studies with the selected dosing regimens are currently ongoing. This case study indicates that a pharmacometric approach can substitute for a conventional dose-finding study in rare diseases and will streamline the drug development process.

Improved Pharmacokinetics with BAY 81-8973 Versus Antihemophilic Factor (Recombinant) Plasma/Albumin-Free Method: A Randomized Pharmacokinetic Study in Patients with Severe Hemophilia A

Background

BAY 81-8973 is a full-length, unmodified, recombinant human factor VIII (FVIII) for the treatment of hemophilia A.

Objective

The aim of this study was to compare the pharmacokinetic (PK) profile of BAY 81-8973 with antihemophilic factor (recombinant) plasma/albumin-free method (rAHF-PFM)

Patients/Methods

In this phase I, open-label, crossover study, men aged 18–65 years with severe hemophilia A and ≥150 exposure days to FVIII were randomized to receive a single intravenous infusion of 50 IU/kg BAY 81-8973 or rAHF-PFM, followed by crossover to a single infusion of the other treatment. FVIII levels were measured in plasma over 48 h using one-stage and chromogenic assays. PK parameters, including area under the curve from time zero to the last data point (AUC_last; primary outcome) and half-life (t_½) were calculated. A population PK model was developed to simulate various treatment scenarios.

Results

Eighteen patients were randomized and analyzed. Using both assays, geometric mean (coefficient of variation [%CV]) AUC_last was significantly higher, and t_½ was significantly longer, for BAY 81-8973 versus rAHF-PFM (one-stage, AUC_last: 1660 IU·h/dL [29.4] vs. 1310 IU·h/dL [29.0], p < 0.0001; one-stage, t_½: 14.5 [25.7] vs. 11.7 h [27.3], p < 0.0001). Simulations showed that median time to 1 IU/dL was approximately 27% longer for BAY 81-8973 versus rAHF-PFM over doses of 25–50 IU/kg; plasma levels >1 IU/dL could be maintained with 14.4 IU/kg BAY 81-8973 or 39.1 IU/kg rAHF-PFM 3×/week.

Conclusions

BAY 81-8973 showed a superior PK profile versus rAHF-PFM. The same FVIII trough threshold level could be achieved with lower doses of BAY 81-8973 versus rAHF-PFM.

ClinicalTrials.gov: NCT02483208.

Performing and interpreting individual pharmacokinetic profiles in patients with Hemophilia A or B: Rationale and general considerations

OBJECTIVES

In a separate document, we have provided specific guidance on performing individual pharmacokinetic (PK) studies using limited samples in persons with hemophilia with the goal to optimize prophylaxis with clotting factor concentrates. This paper, intended for clinicians, aims to describe how to interpret and apply PK properties obtained in persons with hemophilia.

METHODS

The members of the Working Party on population PK (PopPK) of the ISTH SSC Subcommittee on Factor VIII and IX and rare bleeding disorders, together with additional hemophilia and PK experts, completed a survey and ranking exercise whereby key areas of interest in the field were identified. The group had regular web conferences to refine the manuscript's scope and structure, taking into account comments from the external feedback to the earlier document.

RESULTS

Many clinical decisions in hemophilia are based on some form of explicit or implicit PK assessment. Individual patient PK profiles can be analyzed through traditional or PopPK methods, with the latter providing the advantage of fewer samples needing to be collected on any prophylaxis regimen, and without the need the for a washout period. The most useful presentation of PK results for clinical decision making are a curve of the factor activity level over time, the time to achieve a certain activity level, or related parameters like half-life or exposure (AUC). Software platforms have been developed to deliver this information to clinicians at the point of care. Key characteristics of studies measuring average PK parameters were reviewed, outlining what makes a credible head-to-head comparison among different concentrates. Large data collections of PK and treatment outcomes currently ongoing will advance care in the future.

CONCLUSIONS

Traditionally used to compare different concentrates, PK can support tailoring of hemophilia treatment by individual profiling, which is greatly simplified by adopting a PopPK/Bayesian method and limited sampling protocol.

Evolving Complexity in Hemophilia Management

Rapid expansion of therapeutic options have increased the complexity of hemophilia care. Previously, on-demand therapy aimed to reduce morbidity and early mortality; however, now aggressive prophylaxis, particularly in children, encourages an active lifestyle. Accurate diagnosis, recognition of early threats to musculoskeletal health, and optimization of therapy are critical for both males and females affected by hemophilia. The diversity of emerging hemophilia therapies, from modified factor protein concentrates, to gene therapy, to nonfactor hemostatic strategies, provide an exciting opportunity to target unmet needs in the bleeding disorder community.

Pharmacokinetic modelling and validation of the half-life extension needed to reduce the burden of infusions compared with standard factor VIII

INTRODUCTION

Currently, no universally accepted definition of extended half-life (EHL) recombinant FVIII (rFVIII) exists. Identifying the minimum half-life extension ratio required for a reduction in dosing frequency compared with standard rFVIII could enable a more practical approach to decisions around prophylaxis with EHL rFVIII.

AIM

To identify the half-life extension ratio required to decrease rFVIII dosing frequency by at least 1 day while maintaining the proportion of patients with plasma rFVIII levels above 1 IU/dL and without increasing the total weekly dose.

METHODS

A previously published population pharmacokinetic model for standard rFVIII was used to estimate the percentage of patients with factor VIII (FVIII) levels always >1 IU/dL using various benchmark regimens. Using modelling, dosing frequency was reduced while rFVIII half-life was extended until the percentage of patients with FVIII >1 IU/dL equalled that of the benchmark regimen.

RESULTS

Benchmark 3×/wk dosing totalling 100 IU/kg/wk of rFVIII resulted in 56.6% of patients with FVIII levels always >1 IU/dL. With 2×/wk dosing, totalling 80 or 90 IU/kg/wk, half-life extensions required to maintain 56.6% of patients at FVIII levels >1 IU/dL were 1.30 and 1.26, respectively. A half-life extension ratio of 1.33 was required to change dosing from every 48 hours to every 72 hours (both at 105 IU/kg/wk) while maintaining 92.8% of patients with FVIII >1 IU/dL.

CONCLUSION

Based on this investigation, EHL rFVIII products should have a minimum half-life extension ratio of 1.3 to provide a reduction in dosing frequency from 3× to 2×/wk compared with standard rFVIII products while maintaining the same minimum FVIII trough level.

Optimization of prophylaxis for hemophilia A

Background & aims

Prophylactic injections of factor VIII reduce the incidence of bleeds and slow the development of joint damage in people with hemophilia. The aim of this study was to identify optimal person-specific prophylaxis regimens for children with hemophilia A.

Methods

Analytic and numerical methods were used to identify prophylaxis regimens which maximize the time for which plasma factor VIII concentrations exceed a threshold, maximize the lowest plasma factor VIII concentrations, and minimize risk of bleeds.

Results

It was demonstrated analytically that, for any injection schedule, the regimen that maximizes the lowest factor VIII concentration involves sharing doses between injections so that all of the trough concentrations in a prophylaxis cycle are equal. Numerical methods were used to identify optimal prophylaxis schedules and explore the trade-offs between efficacy and acceptability of different prophylaxis regimens. The prophylaxis regimen which minimizes risk of bleeds depends on the person’s pattern of physical activity and may differ greatly from prophylaxis regimens that optimize pharmacokinetic parameters. Prophylaxis regimens which minimize risk of bleeds also differ from prophylaxis regimens that are typically prescribed. Predictions about which regimen is optimal are sensitive to estimates of the effects on risk of bleeds of factor VIII concentration and physical activity.

Conclusion

The methods described here can be used to identify optimal, person-specific prophylaxis regimens for children with hemophilia A.

Setting the stage for individualized therapy in hemophilia: What role can pharmacokinetics play?

Replacement therapy with clotting factor concentrates (CFC) is the mainstay of treatment in hemophilia. Its widespread application has led to a dramatic decrease in morbidity and mortality in patients, with concomitant improvement of quality of life. However, dosing is challenging and costs are high. This review discusses benefits and limitations of pharmacokinetic (PK)-guided dosing of replacement therapy as an alternative for current dosing regimens. Dosing of CFC is now primarily based on body weight and based on its in vivo recovery (IVR). Benefits of PK-guided dosing include individualization of treatment with better targeting, more flexible blood sampling, increased insight into association of coagulation factor levels and bleeding, and potential overall lowering of overall costs. Limitations include a slight burden for the patient, and availability of closely collaborating, experienced clinical pharmacologists.

Climbing therapy under PK-tailored prophylaxis

Climbing has a low risk of injury and strengthens the entire musculature. Due to its benefits in physical and mental health as well as its high fun factor climbing is an established way of therapy. So far, the usefulness of climbing therapy has not been shown for people with haemophilia (PWH). A crucial requirement for physical activity in PWH is regular prophylaxis. As the patient’s individual pharmacokinetic (PK) response varies significantly, PK-tailored prophylaxis may decrease bleeding frequency. Case report: We describe a man (age 25 years) with severe haemophilia A who took part in an 8.5-month weekly climbing program under PK-tailored prophylaxis. Bleeding frequency, factor consumption, joint health (Haemophilia Joint Health Score, HJHS), quality of life (Haemo-QoL-A) and climbing performance (UIAA scale) were assessed before and after the training. Prior to the study, the patient was on demand treatment. The patient was started on standard prophylaxis for a 2 months period and then observed for 6.5 months under PK-tailored prophylaxis. PK-tailored prophylaxis was targeted to a trough level of 1–3%. For high-impact activities a factor activity >15%, for low-impact activities a factor activity >5% was suggested. Results: Climbing therapy was safe. The bleeding rate decreased from 14 (2012) to 1 (during the study period of 8.5 months). The one bleeding event was due to a missed infusion and was not triggered by physical activity. The elimination half-life using Bayesian statistics was determined to be 16h. Using this half-life for PK-tailored prophylaxis reduced the factor VIII consumption in comparison to standard prophylaxis. Joint health was particularly improved in the categories range of motion and swelling. Quality of life scores stayed at a high level. Climbing performance improved by 1 grade. Conclusio: The combination of PK-tailored prophylaxis with therapeutic climbing improved clinical outcome in this young adult with severe haemophilia. The tailored concept for high- and low-impact activities appeared to be safe.

Pharmacokinetic drug evaluation of recombinant factor VIII for the treatment of hemophilia A

INTRODUCTION

The prevention of bleeding by prophylactic factor replacement is the recommended approach for the treatment of severe hemophilia. Prophylaxis should be individualized to provide the best clinical benefit to each patient. Therefore, a pharmacokinetic approach is crucial. Areas covered: This review aims to concisely describe the basic principles of pharmacokinetics of FVIII, the role of population pharmacokinetic, the available different recombinant FVIII concentrates and the new extended half-life FVIII molecules with possible improvement in hemophilia A treatment. Expert opinion: Pharmacokinetic is a useful tool to predict the outcome of replacement therapy, even though a large inter-individual variability exists, becauseof several factors: age, weight, von Willebrand factor level, blood group, active bleed, presence of inhibitors to FVIII, FVIII concentrate. Among the different recombinant FVIII concentrates pharmacokinetic differences are minor and clinically not significant. The extended half-life FVIII products brings only moderate advances, as half life extension is limited to 1.5-1.8-fold in comparison to that of native FVIII. Thus, infusions could be done every fourth, rarely fifth day to ensure a safe through level and a significant benefit can be offered only to patients treated every other day or three times weekly.

Using pharmacokinetics to individualize hemophilia therapy

Prevention and treatment of bleeding in hemophilia requires that plasma clotting factor activity of the replaced factor exceeds a defined target level. Most clinical decisions in hemophilia are based on implicit or explicit application of pharmacokinetic measures. The large interindividual variability in pharmacokinetics of factor concentrates suggests that relying on the average pharmacokinetic characteristics of factor concentrates would not allow optimizing the treatment of individual patients; for example, adjusting the frequency of infusions and targeting a specific clotting factor activity level on a case-by-case basis. However, individual pharmacokinetic profiles are seldom assessed as part of routine clinical care. Population pharmacokinetics provide options for precise and convenient characterization of pharmacokinetics characteristics of factor concentrates, simplified individual pharmacokinetic profiling, and individualized dosing. Population pharmacokinetics allow for the incorporation of determinants of interpatient variability and reduces the need for extensive postinfusion plasma sampling. Barriers to the implementation of population pharmacokinetics are the need for concentrate-specific pharmacokinetic models, Bayesian calculation power, and specific expertise for production, validation, and appraisal of forecasted estimates. Population pharmacokinetics provide an important theoretical and practical contribution to tailoring the treatment of hemophilia. The need remains for prospective exploration of the clinical impact of tailoring hemophilia treatment based on individual pharmacokinetics, and for the systematic validation of existing software solutions and concentrate-specific models.

Modeling of Body Weight Metrics for Effective and Cost-Efficient Conventional Factor VIII Dosing in Hemophilia A Prophylaxis

The total body weight-based dosing strategy currently used in the prophylactic treatment of hemophilia A may not be appropriate for all populations. The assumptions that guide weight-based dosing are not valid in overweight and obese populations, resulting in overdosing and ineffective resource utilization. We explored different weight metrics including lean body weight, ideal body weight, and adjusted body weight to determine an alternative dosing strategy that is both safe and resource-efficient in normal and overweight/obese adult patients. Using a validated population pharmacokinetic model, we simulated a variety of dosing regimens using different doses, weight metrics, and frequencies; we also investigated the implications of assuming various levels of endogenous factor production. Ideal body weight performed the best across all of the regimens explored, maintaining safety while moderating resource consumption for overweight and obese patients.

Partnering to change the world for people with haemophilia: 7th Haemophilia Global Summit, Madrid, Spain 22-24 September 2016

The 7th Haemophilia Global Summit was held in Madrid, Spain, in September 2016. With a programme designed, for the 6th consecutive year, by a Scientific Steering Committee of haemophilia experts, the aim of the summit was to share optimal management strategies for haemophilia at all life stages and to provide an opportunity for specialists from across the haemophilia multidisciplinary care team to engage in discussion and debate with leading international experts on current and future areas of research. Topics covered ranged from the optimisation of haemophilia management, emerging issues in clinical care, practical approaches and future perspectives, in addition to patient engagement and empowerment in modern haemophilia care.

In silico evaluation of limited blood sampling strategies for individualized recombinant factor IX prophylaxis in hemophilia B patients

Essentials Individual pharmacokinetic (PK) parameters can be obtained by limited sampling strategies (LSSs). Following 100 IU kg-1 rFIX, LSSs with 1 to 3 samples were evaluated in 5000 simulated subjects. For all LSSs, estimated individual PK parameters showed acceptable bias and precision. One sample between 10 min-3 h and two between 48 h-56 h showed best predictive performance.

SUMMARY

Background Patients with severe hemophilia B regularly administer prophylactic intravenous doses of clotting factor IX concentrate to maintain a trough level of at least 0.01 IU mL-1 in order to prevent joint bleeds. Assessment of individual pharmacokinetic (PK) parameters allows individualization of the recombinant factor IX (rFIX) dose. Aim To evaluate the predictive performance of limited sampling strategies (LSSs) with one to three samples to estimate individual PK parameters of rFIX. Methods Monte Carlo simulations were performed to obtain 5000 concentration-time profiles by the use of population PK parameters for rFIX from literature. Eleven LSSs were developed with one, two or three samples taken within an 80-h interval following administration of 100 IU kg-1 rFIX. Clearance (CL), half-life (t1/2 ), time to 1% and steady-state distribution volume (Vss ) were estimated for each simulated individual by the use of Bayesian analysis. Results For each LSS, average bias was small for CL (range - 1.5% to 1.4%), t1/2 (range - 4.5% to - 0.7%), time to 1% (range - 2.9% to 0%), and Vss (range - 3.7% to 0.3%). Imprecision for these parameters ranged from 6.4% to 11.9%, from 10.3% to 15.6%, from 7.3% to 10.9%, and from 9% to 20.1%, respectively. The best predictive performance was achieved with one sample taken between 10 min and 3 h and two samples taken between 48 h and 56 h after administration of rFIX. Conclusions This study demonstrates that limited sampling strategies, used for individualized dosing of rFIX in hemophilia B patients, can be developed and evaluated by in silico simulation.

What is the role for population pharmacokinetics in hemophilia?

Prevention of bleeding in hemophilia requires that plasma levels of the deficient factor exceed the desired minimum target level. Large interindividual variability suggests that knowledge of individual pharmacokinetic (PK) would help to achieve this goal, simultaneously minimizing infusion frequency and the amount of concentrate used. Population PK (PopPK) allows for the incorporation of determinants of interpatient variability and eliminates the need for extensive postinfusion plasma sampling. Barriers to implementation of PopPK are the need for concentrate specific models, Bayesian calculation power, specific expertise for validation and appraisal of forecasted estimates. The Web Accessible Population Pharmacokinetic Service – Hemophilia ( www.wapps-hemo.org ), developed by an international research network of hemophilia centers will test if PK-guided dose individualization can improve patient important outcomes in hemophilia.

Population pharmacokinetic characterization of BAY 81-8973, a full-length recombinant factor VIII: lessons learned - importance of including samples with factor VIII levels below the quantitation limit

INTRODUCTION

The pharmacokinetics (PK), safety and efficacy of BAY 81-8973, a full-length, unmodified, recombinant human factor VIII (FVIII), were evaluated in the LEOPOLD trials.

AIM

The aim of this study was to develop a population PK model based on pooled data from the LEOPOLD trials and to investigate the importance of including samples with FVIII levels below the limit of quantitation (BLQ) to estimate half-life.

METHODS

The analysis included 1535 PK observations (measured by the chromogenic assay) from 183 male patients with haemophilia A aged 1-61 years from the 3 LEOPOLD trials. The limit of quantitation was 1.5 IU dL^-1 for the majority of samples. Population PK models that included or excluded BLQ samples were used for FVIII half-life estimations, and simulations were performed using both estimates to explore the influence on the time below a determined FVIII threshold.

RESULTS

In the data set used, approximately 16.5% of samples were BLQ, which is not uncommon for FVIII PK data sets. The structural model to describe the PK of BAY 81-8973 was a two-compartment model similar to that seen for other FVIII products. If BLQ samples were excluded from the model, FVIII half-life estimations were longer compared with a model that included BLQ samples.

CONCLUSIONS

It is essential to assess the importance of BLQ samples when performing population PK estimates of half-life for any FVIII product. Exclusion of BLQ data from half-life estimations based on population PK models may result in an overestimation of half-life and underestimation of time under a predetermined FVIII threshold, resulting in potential underdosing of patients.

Medical co-morbidities of patients with haemophilia: pain, obesity and hepatitis C

Clinical care of patients with haemophilia (PWH) has progressed rapidly over the past decade. Current therapy has allowed patients with haemophilia to live longer and many patients are now experiencing the co-morbidities of the general population. In this review article, we focus on three common diseases states that affect PWH: chronic pain, obesity and hepatitis C. Pain has been a co-morbidity for many years and PWH often have unusual needs for chronic pain relief compared to the general population. Obesity is not only increasing in the general population but also in patients with hereditary bleeding disorders. The co-morbidity of obesity not only causes increased pain progression and joint damage but also affects the dosing of factor concentrates. Finally, hepatitis C is known to have infected the majority of patients who received non-virally inactivated pooled factor concentrates in the past. New treatment regimens have been developed that allow the nearly uniform cure of chronic hepatitis C with a short course of oral medications.

Partnering to change the world for people with haemophilia: 6(th) Haemophilia Global Summit, Prague, Czech Republic, 24-26(th) September 2015

The 6(th) Haemophilia Global Summit was held in Prague, Czech Republic, in September 2015. The programme was designed by an independent Scientific Steering Committee of haemophilia experts and aimed to share optimal management strategies for haemophilia at all life stages, explore recent potential advances in the management of haemophilia A and B and discuss challenges in haemophilia care. In this supplement from the meeting, Dan Hart reviews the lessons that can be learnt from cost-constrained environments with regard to improving care for people with haemophilia globally. Sébastien Lobet discusses the importance of physical activity for optimising care and Roseline d'Oiron and Jan Blatný consider the role of real-world data in understanding the effect of treatment in a clinical setting over the long term and the true impact of treatment on the day-to-day life of the patient. Gili Kenet addresses the current challenges relating to the optimal management of prophylaxis, and Gerry Dolan and Cedric Hermans discuss the value of pharmacokinetic (PK) parameters in informing treatment decisions. Cedric Hermans and Valérie Libotte explore the importance of considering social and occupational development factors as an integral part of haemophilia care, and Jan Astermark reviews key strategies to predict and prevent inhibitor development.

New therapies for hemophilia

Individuals with severe hemophilia have benefitted from 5 decades of advances that have led to widespread availability of safe and efficacious factors VIII and IX, a multidisciplinary integrated care model through a network of specialized hemophilia treatment centers, and aggressive introduction of prophylactic replacement therapy to prevent bleeding and preserve joint health. Yet, there are remaining challenges and treatment gaps which have prevented complete abrogation of all joint bleeding, and progressive joint deterioration may continue in some affected individuals over the course of a lifetime. Some of these challenges can now be addressed with recombinant clotting factors with extended half-life that may improve adherence to prophylaxis regimens through more convenient infusion schedules, maintain higher plasma levels for longer when clinically necessary, and allow for better adaptation to individual phenotypic and pharmacokinetic variability. Real-world case studies will be presented that illustrate practical application of these newly approved therapies in clinical practice and the clinical trial data that have demonstrated the potential for improved clinical outcomes by implementing these strategies.

2017 Clinical trials update: Innovations in hemophilia therapy

A surge in therapeutic clinical trials over recent years is paving the way for transformative treatment options for patients with hemophilia. The introduction of recombinant factor concentrates in the early 1990s facilitated the use of prophylactic replacement as standard care for hemophilia rather than on-demand treatment. This has revolutionized health outcomes for hemophilia patients, enabling participation in physical activities and reducing debilitating, chronic joint damage. Challenges of prophylactic factor infusion include the frequency of infusions needed to maintain factor levels greater than 1%, patient adherence, reliable intravenous access, and development of neutralizing alloantibodies ("inhibitors"). Novel therapeutics seek to improve upon current factor concentrates by several different mechanisms: (1) extending the half-life of circulating exogenous factor protein, (2) replacing the gene necessary for production of endogenous factor protein, (3) employing bispecific antibody technology to mimic the coagulation function of factor VIII, (4) disrupting anticoagulant proteins, such as tissue factor pathway inhibitor (TFPI) or antithrombin (AT3) with antibodies, aptamers, or RNA interference technology. Emerging treatment options may reduce the frequency of (extended half-life products) or eliminate (gene therapy) the need for scheduled factor concentrate infusions, or provide a subcutaneous administration option (bispecific antibody, AT3, and TFPI targeting therapies). In addition, the nonfactor replacement strategies provide a promising treatment option for patients with inhibitors, presently the greatest unmet medical need in hemophilia. This review highlights current and recently completed clinical trials that are driving a paradigm shift in our approach to hemophilia care for patients with and without inhibitors. Am. J. Hematol. 91:1252-1260, 2016. © 2016 Wiley Periodicals, Inc.

Hemophilia in Sports: A Case Report and Prophylactic Protocol

OBJECTIVE

 To describe a successful prophylactic protocol for managing an athlete with hemophilia playing at a high level of contact sports.

BACKGROUND

 Published data show that team physicians are not comfortable either treating athletes with bleeding disorders or allowing them to participate in contact sports. Much of the literature historically has recommended against allowing athletes with bleeding disorders to play sports at all and certainly against playing contact sports. Hemophilia treatment can now include prophylactic injections of recombinant factor VIII to prevent bleeding episodes. Modern treatments hold the promise of allowing athletes with hemophilia to participate in contact sports.

DIFFERENTIAL DIAGNOSIS

 Mild, moderate, or severe hemophilia; von Willebrand disease; other factor deficiencies.

TREATMENT

 A treatment protocol was developed that included prophylactic factor VIII injections on a regular basis and when the athlete was injured.

UNIQUENESS

 This is the first published case report of an athlete with known hemophilia being successfully treated and participating in National Collegiate Athletic Association collegiate basketball for 2 full seasons.

CONCLUSIONS

 Sports medicine teams can successfully manage an athlete with hemophilia playing a contact sport.

Adherence to treatment regimen and bleeding rates in a prospective cohort of youth and young adults on low-dose daily prophylaxis for severe hemophilia A

BACKGROUND

When availability and/or affordability of anti-hemophilic factor concentrates are limited, optimal prophylaxis regimens in severe hemophilia A (HA) remain to be determined. In selected situations, low-dose daily prophylaxis (LDDP) may be an effective and economical option. The goal of our study was to evaluate if subjects on a LDDP regimen could achieve adherence and good clinical outcome.

METHODS

Seventeen subjects (age between 15.2 and 28.4) on LDDP suffering from severe/moderate HA were followed prospectively for 2 to 3 years as part of a health-related quality of life (HRQoL) study. Bleeding and treatments data were collected using electronic diaries and validated every three months. The SF-36 questionnaire was administered at the beginning of the study and then every 6 months until the end of the study.

RESULTS

The subjects (mean age 22.0, median 21.9, standard deviation 4.06), were all from a single centre and on LDDP for at least 12 months as part of their routine care before entering the study. Fifteen subjects were prescribed a daily dose of 500 IU factor VIII (FVIII) and 2 subjects received 1000 IU FVIII per day, resulting into a median dose of 7.1 IU/kg/day (ranging from 4 to 13 IU/kg/day) and of 2591 IU/kg/year. Median adherence (the percentage of the prescribed daily dose received) was 84 % (mean 80 %, range 57 % to 94 %) throughout the study. Seventy-six bleeds in the 6 index joints and 51 other types of bleeds were observed throughout the study. The median annualized bleeding rate in joints (ABRjoints) was 0.7 and the median annualized bleeding rate for all bleeds (ABRall) was 1.6. The Physical Component and Mental Component Summary scores of SF-36, and the Hemophilia Joint Health Score were not significantly different over the course of the study (respective medians of 49.8, 52.4 and 16.0 at entry; vs. 52.5, 51.5 and 16.0 upon exit).

CONCLUSIONS

This prospective longitudinal study in youth and young adults shows that LDDP may be associated with low ABRs, adequate adherence and HRQoL comparable to previously reported.

Predicting the outcomes of using longer-acting prophylactic factor VIII to treat people with severe hemophilia A: a hypothetical decision analysis

Essentials No randomized trials have compared long-acting factor VIII (FVIII) with currently used products. A comparison was undertaken using a decision model to predict FVIII use and number of bleeds. In the base case, longer acting FVIII reduced factor use by 17% while resulting in similar bleeds. The value of longer acting FVIII will be largely determined by existing regimens and unit price. Click to hear Prof. Makris's presentation on new treatments in hemophilia SUMMARY: Background Recently, factor VIII (FVIII) products with longer half-lives, such as recombinant FVIII Fc fusion protein (rFVIIIFc), have become available. Use of longer-acting FVIII products will largely depend on effectiveness and cost; no direct evaluations have compared these parameters between conventional and longer-acting FVIII therapies. Objectives To present a hypothetical decision analysis, combining evidence from multiple sources to estimate bleeding frequency, resource use and cost of longer-acting prophylactic products, such as rFVIIIFc, vs. conventional recombinant FVIII (rFVIII). Patients/Methods The decision model used published pharmacokinetic parameters, bleeding frequency vs. time information below a 1-IU dL-1 FVIII trough level, and adherence. Prophylactic treatment scenarios were modelled for a hypothetical patient with severe hemophilia A (<1 IU/dL) receiving rFVIIIFc or rFVIII. Results Infusing twice weekly with rFVIIIFc 42.7 IU kg-1 per dose required less clotting factor than infusing every 56 h with rFVIII 33.75 IU kg-1 per dose; annual bleeding rates were similar. Base case analysis suggested that total FVIII costs were equated when rFVIIIFc cost 1.18 times more per IU than rFVIII, assuming similar adherence. Other modelled scenarios produced similar results, although differences in FVIII consumption were particularly sensitive to assumptions regarding frequency and dose of the rFVIII and rFVIIIFc regimens. For example, decreasing rFVIII from 33.75 IU kg-1 to 30 IU kg-1 per dose decreased the price factor to 1.05. Conclusions Longer-acting FVIII products may reduce FVIII consumption and infusion frequency without compromising hemostatic effect; this should be considered along with other factors (e.g. adherence and underlying FVIII regimen) when evaluating a suitable price for these agents.

A population pharmacokinetic model for perioperative dosing of factor VIII in hemophilia A patients

The role of pharmacokinetic-guided dosing of factor concentrates in hemophilia is currently a subject of debate and focuses on long-term prophylactic treatment. Few data are available on its impact in the perioperative period. In this study, a population pharmacokinetic model for currently registered factor VIII concentrates was developed for severe and moderate adult and pediatric hemophilia A patients (FVIII levels <0.05 IUmL^-1) undergoing elective, minor or major surgery. Retrospective data were collected on FVIII treatment, including timing and dosing, time point of FVIII sampling and all FVIII plasma concentrations achieved (trough, peak and steady state), brand of concentrate, as well as patients' and surgical characteristics. Population pharmacokinetic modeling was performed using non-linear mixed-effects modeling. Population pharmacokinetic parameters were estimated in 75 adults undergoing 140 surgeries (median age: 48 years; median weight: 80 kg) and 44 children undergoing 58 surgeries (median age: 4.3 years; median weight: 18.5 kg). Pharmacokinetic profiles were best described by a two-compartment model. Typical values for clearance, intercompartment clearance, central and peripheral volume were 0.15 L/h/68 kg, 0.16 L/h/68 kg, 2.81 L/68 kg and 1.90 L/68 kg. Interpatient variability in clearance and central volume was 37% and 27%. Clearance decreased with increasing age (P<0.01) and increased in cases with blood group O (26%; P<0.01). In addition, a minor decrease in clearance was observed when a major surgical procedure was performed (7%; P<0.01). The developed population model describes the perioperative pharmacokinetics of various FVIII concentrates, allowing individualization of perioperative FVIII therapy for severe and moderate hemophilia A patients by Bayesian adaptive dosing.

An innovative outcome-based care and procurement model of hemophilia management

Hemophilia is a rare bleeding disorder associated with spontaneous and post-traumatic bleeding. Each hemophilia patient requires a personalized approach to episodic or prophylactic treatment, but self-management can be challenging for patients, and avoidable bleeding may occur. Patient-tailored care may provide more effective prevention of bleeding, which in turn, may decrease the likelihood of arthropathy and associated chronic pain, missed time from school or work, and progressive loss of mobility. A strategy is presented here aiming to reduce or eliminate bleeding altogether through a holistic approach based on individual patient characteristics. In an environment of budget constraints, this approach would link procurement to patient outcome, adding incentives for all stakeholders to strive for optimal care and, ultimately, a bleed-free world.

Perioperative treatment of hemophilia A patients: blood group O patients are at risk of bleeding complications

ESSENTIALS: Targeting of factor VIII values is a challenge during perioperative replacement therapy in hemophilia. This study aims to identify the extent and predictors of factor VIII underdosing and overdosing. Blood group O predicts underdosing and is associated with perioperative bleeding. To increase quality of care and cost-effectiveness of treatment, refining of dosing is obligatory.

SUMMARY

BACKGROUND

Perioperative administration of factor VIII (FVIII) concentrate in hemophilia A may result in both underdosing and overdosing, leading to respectively a risk of bleeding complications and unnecessary costs.

OBJECTIVES

This retrospective observational study aims to identify the extent and predictors of underdosing and overdosing in perioperative hemophilia A patients (FVIII levels < 0.05 IU mL(-1)).

PATIENTS AND METHODS

One hundred nineteen patients undergoing 198 elective, minor, or major surgical procedures were included (median age 40 years, median body weight 75 kg). Perioperative management was evaluated by quantification of perioperative infusion of FVIII concentrate and achieved FVIII levels. Predictors of underdosing and (excessive) overdosing were analyzed by logistic regression analysis. Excessive overdosing was defined as upper target level plus ≥ 0.20 IU mL(-1).

RESULTS

Depending on postoperative day, 7-45% of achieved FVIII levels were under and 33-75% were above predefined target ranges as stated by national guidelines. A potential reduction of FVIII consumption of 44% would have been attained if FVIII levels had been maintained within target ranges. Blood group O and major surgery were predictive of underdosing (odds ratio [OR] 6.3, 95% confidence interval [CI] 2.7-14.9; OR 3.3, 95% CI 1.4-7.9). Blood group O patients had more bleeding complications in comparison to patients with blood group non-O (OR 2.02, 95% CI 1.00-4.09). Patients with blood group non-O were at higher risk of overdosing (OR 1.5, 95% CI 1.1-1.9). Additionally, patients treated with bolus infusions were at higher risk of excessive overdosing (OR 1.8, 95% CI 1.3-2.4).

CONCLUSION

Quality of care and cost-effectiveness can be improved by refining of dosing strategies based on individual patient characteristics such as blood group and mode of infusion.

Joining the patient on the path to customized prophylaxis: one hemophilia team explores the tools of engagement

BACKGROUND

The relationship between hemophilia team interventions and achievement of optimal clinical outcomes remains to be elucidated. The British Columbia Hemophilia Adult Team has previously reported results of a comprehensive approach to individualize prophylaxis that has resulted in substantially reduced bleeding rates. In order to facilitate knowledge exchange and potential replication, it was important to gain a thorough understanding of the team's approach.

METHODS

A focus group of the British Columbia Hemophilia Adult Team was conducted to identify specific roles and processes that might be contributing to the prophylaxis regimen outcomes in this clinic. The focus group consisted of two workshops; one to describe the individual and collective roles of the clinic team in providing clinical care and guiding patients toward individualized prophylaxis; and the other to describe the patient journey from initial contact through reaching a successful engagement with the clinic.

RESULTS

Analysis of the results revealed team roles and processes that underpinned a shared decision-making relationship with the patient with a particular focus on supporting the patient's autonomy. Within this relationship, team focus shifts away from "adherence" toward the process whereby patients design and implement prophylaxis regimens resulting in reduction or elimination of bleeding episodes.

LIMITATIONS

Using the current methodology, it is not possible to demonstrate a causal link between specific team processes and improved bleeding rates in patients.

CONCLUSION

Through the active support of patient autonomy in all aspects of decisions related to hemophilia management, the British Columbia Hemophilia Adult Team approach de-emphasizes "adherence" as the primary goal, and focuses on a prophylaxis plan that is customized by the patient and aligned with his priorities. Adoption of this comprehensive team approach facilitates shared goals between the patient and the team that may optimize treatment adherence, but more importantly, reduce bleeding rates.

A first-in-human phase 1 study of ACE910, a novel factor VIII-mimetic bispecific antibody, in healthy subjects

ACE910 is a recombinant humanized bispecific antibody that binds to activated factor IX and factor X and mimics the cofactor function of factor VIII (FVIII). This first-in-human study examined the safety, tolerability, pharmacokinetics (PK), and pharmacodynamics (PD) of ACE910 in healthy male adults. A total of 40 Japanese and 24 white subjects were randomized to receive a single subcutaneous injection of ACE910 (Japanese: 0.001, 0.01, 0.1, 0.3, or 1 mg/kg; white: 0.1, 0.3, or 1 mg/kg; n = 6 per dose group) or placebo (n = 2 per dose group). ACE910 exhibited a linear PK profile and had a half-life of ∼4 to 5 weeks. In FVIII-neutralized plasma, ACE910 shortened activated partial thromboplastin time and increased peak height of thrombin generation in a dose-dependent manner. All adverse events were nonserious and did not lead to any subject's withdrawal. Neither clinical findings nor laboratory abnormalities indicating hypercoagulability were observed. Two of 48 subjects receiving ACE910 (1 Japanese and 1 white) were positive for anti-ACE910 antibodies (anti-drug antibodies [ADAs]). One subject tested positive for ADAs both before and after ACE910 administration, whereas the other became ADA positive after receiving ACE910. The PK and PD profiles of ACE910 were similar in healthy Japanese and white subjects and suggest that ACE910 will be an effective and convenient prophylactic treatment of hemophilia A. This trial was registered at www.clinicaltrials.jp as #JapicCTI-121934.

Impact of being overweight on factor VIII dosing in children with haemophilia A

INTRODUCTION

Treatment of haemophilia A (HA) requires infusions of factor VIII (FVIII) concentrates. The number of FVIII units infused to obtain a specific circulating FVIII level is calculated with the formula: [body weight (BW) (kg) × desired FVIII increase (%)]/2, with the assumption that each unit of FVIII infused per kg of BW increases the circulating FVIII level by 2%.

AIM

The aim of this study was to evaluate the impact of several morphometric parameters (BW, body mass index (BMI)-for-age, height), age and type of FVIII concentrate on FVIII recovery in children with HA.

METHODS

A total of 66 children aged between 10 and 18 with severe HA selected from six pharmacokinetic (PK) clinical trials using two recombinant FVIII concentrates were included in the analysis. Regression tree (RT) was used to identify predictors of FVIII recovery.

RESULTS

The median age was 14.5 years with a median FVIII recovery of 2.09 for all children. The median FVIII recovery was not significantly different between age groups. Two groups were created by RT: children with a BMI-for-age percentile <P95 (Median FVIII recovery: 1.94) and obese children with a BMI-for-age percentile ≥P95 (Median FVIII recovery: 2.65). The FVIII recovery was significantly different between these two groups (P < 0.001).

CONCLUSION

These results are consistent with previous studies conducted in adults with HA and confirm that the long-held and current practice of applying an arbitrary and universal recovery of two to the calculations of FVIII dosage should be abolished in both children and adults.

Managing Haemophilia for Life: 5th Haemophilia Global Summit

The 5th Haemophilia Global Summit was held in Barcelona, Spain, in September 2014. The programme was designed by an independent Scientific Steering Committee of haemophilia experts and explored issues relevant to the practical management of haemophilia, as well as key opportunities and challenges for care in the future. The topics outlined in this supplement were selected by the Scientific Steering Committee for their relevance to improving haemophilia care globally. In this supplement from the meeting, Gerry Dolan explores pharmacokinetics and dynamics in haemophilia, and Gerry Dolan and Ian Jennings jointly address the role of the laboratory in haemophilia care. The potential benefits of low-dose prophylaxis regimens for people with haemophilia in the developing world are reviewed by Jerzy Windyga, and the question of whether 'Future haemophilia research should be undertaken in the developing world' is debated by Jerzy Windyga and Cedric Hermans. Management strategies for ankle arthropathy are discussed by Sébastien Lobet and E. Carlos Rodríguez-Merchán, and the use of ultrasound for the early detection of haemophilic arthropathy is addressed by Matteo Nicola Dario Di Minno and Víctor Jiménez-Yuste. Finally, the role of patients in the future of haemophilia care is reviewed by Brian O'Mahony.

Personalized approaches to the treatment of hemophilia A and B

The recognition that individuals respond differently to the same medication is not new and dates almost to the founding of western medicine. In the last century it came to be recognized that genetic factors influence the heterogeneity of individual responses to medications with respect to both toxicity and effectiveness. Nonetheless, it has been challenging to integrate pharmacogenetic approaches in the routine practice of medicine as the identification of biomarkers is difficult due to the inherent complexity of biological systems. Here, we present potential applications of pharmacogenetics in managing hemophilia A and B. We discuss how predicting and circumventing immunogenicity, an important impediment to treating hemophilia patients, particularly lends itself to a pharmacogenetic approach. In addition, we discuss new trends toward personalizing the management of hemophilia in clinical settings.