Clinical outcomes in hemophilia A patients undergoing tailoring of prophylaxis based on population-based pharmacokinetic dosing

Shifting Paradigms and Arising Concerns in Severe Hemophilia A Treatment

The management of hemophilia A has undergone a remarkable revolution, in line with technological advancement. In the recent past, the primary concern associated with Factor VIII (FVIII) concentrates was the risk of infections, which is now almost resolved by advanced blood screening and viral inactivation methods. Improving patients' compliance with prophylaxis has become a key focus, as it can lead to improved health outcomes and reduced health care costs in the long term. Recent bioengineering research is directed toward prolonging the recombinant FVIII (rFVIII) coagulant activity and synthesising higher FVIII yields. As an outcome, B-domain deleted, polyethylene glycolated, single-chain, Fc-fused rFVIII, and rFVIIIFc-von Willebrand Factor-XTEN are available for patients. Moreover, emicizumab, a bispecific antibody, is commercially available, whereas fitusiran and tissue factor pathway inhibitor are in clinical trial stages as alternative strategies for patients with inhibitors. With these advancements, noninfectious complications, such as inhibitor development, allergic reactions, and thrombosis, are emerging concerns requiring careful management. In addition, the recent approval of gene therapy is a major milestone toward a permanent cure for hemophilia A. The vast array of treatment options at our disposal today empowers patients and providers alike, to tailor therapeutic regimens to the unique needs of each individual. Despite significant progress in modern treatment options, these highly effective therapies are markedly more expensive than conventional replacement therapy, limiting their access for patients in developing countries.

Moderate- to vigorous-intensity physical activities for hemophilia A patients during low-dose pharmacokinetic-guided extended half-life factor VIII prophylaxis

BACKGROUND

Low-dose pharmacokinetic (PK)-guided extended half-life (EHL) factor VIII (FVIII) prophylaxis can reduce the bleeding risk in hemophilia A (HA) patients. An increase in physical activities for promoting musculoskeletal health may enhance the benefits of prophylactic therapy.

OBJECTIVES

To determine the clinical impact of moderate- to vigorous-intensity physical activities in HA patients during low-dose PK-guided EHL FVIII prophylaxis.

PATIENTS/METHODS

This prospective study enrolled patients with moderate/severe HA (baseline FVIII levels ≤ 5 IU/dL) who had received low-dose PK-guided EHL FVIII prophylaxis for ≥ 6 months. An individualized exercise protocol was introduced to each participant, targeting a 65% increase in the maximum predicted heart rate for ≥ 150 min/week, while continuing low-dose PK-guided EHL FVIII prophylaxis for 6 months. Before and after implementing the intervention, annualized bleeding rates (ABR), annualized joint bleeding rates (AJBR), Hemophilia Joint Health Scores (HJHS), skeletal muscle mass, hemophilia-specific quality-of-life (QoL) scores and annualized FVIII consumption were compared.

RESULTS

Of 13 participants (mean age ± standard deviation [SD]: 20.1 ± 6.8 years), ABR, AJBR, and HJHS were significantly reduced (mean differences [MD] ± SD: -5.7 ± 2.6 bleeds/year, -4.2 ± 2.6 joint bleeds/year, and -4.3 ± 3.2 marks, respectively; P < 0.05) after applying the 6-month exercise protocol. Skeletal muscle mass and QoL scores had also improved (P = 0.001), while FVIII usage had decreased (MD ± SD: -129.1 ± 208.7 IU/kg/year; P < 0.05).

CONCLUSIONS

The combination of moderate- to vigorous-intensity physical activities with low-dose PK-guided EHL FVIII prophylaxis improves bleeding prevention, musculoskeletal status and QoL in patients with moderate/severe HA. By minimizing FVIII consumption, this strategy helps optimize hemophilia care in countries with budget constraints.

CLINICALTRIALS

gov NCT05728528.

Predictive performance of pharmacokinetic-guided prophylactic dosing of factor concentrates in hemophilia A and B

Background

Pharmacokinetic (PK)-guided dosing is used to individualize factor (F)VIII and FIX replacement therapy.

Objectives

This study investigates the reliability and feasibility of PK-guided prophylactic dosing of factor concentrates in hemophilia A and B.

Methods

In this multicenter, prospective cohort study, people of all ages with hemophilia received prophylactic treatment with factor concentrates based on individual PK parameters. During follow-up, at least 4 measured FVIII/FIX levels per patient were compared with corresponding predicted levels obtained by Bayesian forecasting. Predictive performance was defined as adequate when ≥80% of measured FVIII/FIX levels were within ±25% of prediction (relative error). Additionally, mean absolute error and mean error were calculated. In post hoc analyses, predictive performance was assessed allowing maximum absolute errors of 1 (trough), 5 (mid), and 15 (peak) IU/dL. Five-point scale questionnaires addressed feasibility of PK guidance.

Results

We included 50 patients (median age, 19 years; range: 2-72 years). Median follow-up was 36 weeks. Seventy-one percent of levels (58% trough, 83% mid, and 80% peak) were within ±25% of prediction. Mean absolute errors were 0.8 (trough), 2.0 (mid), and 8.6 (peak) IU/dL. In post hoc analyses, 81% (trough), 96% (mid), and 82% (peak) of levels were within set limits. Patients reported low burden and high satisfaction.

Conclusion

PK-guided dosing was reliable according to post hoc analyses, based on low absolute errors that were regarded as clinically irrelevant in most cases. The predefined predictive performance was achieved in mid and peak factor levels but not in trough factor levels due to measurement inaccuracy. PK guidance also seemed feasible.

Comparison Pharmacokinetic Dosing Tools in Hemophilia A Children

Prophylaxis is the gold standard for the management of hemophilia A patients. It has been shown that prophylaxis regulated with pharmacokinetic (PK) data reduces frequency of bleeding and cost of treatment. To determine the best prophylaxis regimen, PK dosing tools using the Bayesian method have been developed. We aimed to compare two PK dosing tools. Blood samples were drawn before, 4, 24, and 48 h after FVIII infusions from patients with severe hemophilia A and inhibitor negative. FVIII levels were measured by PTT-based one-stage assay method. PK parameters obtained using WAPPS and myPKFiT, which are web-accessible PK dosing tools using Bayesian algorithm, and daily prophylaxis dose estimated by the programs were compared. Forty-two hemophilia A patients [median age 13 years (IQR 8.9-16.4)] included in the study. There was no difference between the daily dose of FVIII given for prophylaxis and the dose recommended by the myPKFiT for the 1% trough level; whereas, a significant difference was found with the WAPPS. The half-lives of FVIII did not differ between the two dosing tools; however, significant differences were found in the estimated dose, clearances, and times to 1% trough level. There was no significant difference between PK data of patients who received Advate® and those who received non-Advate® factor concentrates. Choice of PK dosing tool can affect recommended FVIII dose. However, target trough levels should be individualized according to bleeding phenotype and daily activity of patient.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12288-023-01671-0.

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.

Pharmacokinetic-guided versus standard prophylaxis in hemophilia: a systematic review and meta-analysis

BACKGROUND

With population pharmacokinetic (PK) modeling more readily available and PK-guided prophylaxis endorsed by current hemophilia guidelines, we conducted a systematic review to summarize current evidence in the literature.

OBJECTIVES

To assess the efficacy of PK-guided compared with non-PK-guided prophylaxis.

METHODS

We did not restrict inclusion to specific study design labels and included all studies consisting of at least one distinct cohort arm receiving PK-guided prophylaxis. We searched the following databases from inception to date of search: MEDLINE, Embase, CENTRAL, ClinicalTrials.gov, and the EU Clinical Trial Register. Following title, abstract, and full-text screening conducted independently by 2 review authors, we summarized studies qualitatively and synthesized included randomized clinical trials (RCTs) quantitatively by fitting random-effects models.

RESULTS

Search of databases on February 3, 2023, yielded 25 studies fitting our inclusion criteria. Of those, only 2 RCTs and 17 nonrandomized studies included a standard prophylaxis comparator group. Furthermore, risk of bias in the latter was substantial, primarily due to before-after study designs and retrospective comparator groups. Thus, nonrandomized studies were only presented qualitatively. A random-effects meta-analysis of the 2 identified RCT remained inconclusive with regards to bleeding outcomes (ratio of means, 1.15; 95% CI, 0.85-1.56) and factor consumption (ratio of means, 0.82; 95% CI, 0.58-1.18).

CONCLUSION

Evidence in the literature suggesting a clinical benefit of PK-guided over standard fixed-dose prophylaxis was weak and mainly found in nonrandomized studies limited by lack of concurrent controls, heterogeneity in outcome reporting, small sample sizes, and high risk of bias.

The road to implementation of pharmacokinetic-guided dosing of factor replacement therapy in hemophilia and allied bleeding disorders. Identifying knowledge gaps by mapping barriers and facilitators

Clinical guidelines and expert groups recommend the use of pharmacokinetic (PK)-guided dosing of factor replacement therapy for the treatment of bleeding disorders, especially for patients with hemophilia. Although PK-guided dosing is increasingly applied, it is generally not considered standard clinical practice. The aim of this scoping review is to map barriers and facilitators for the implementation of PK-guided dosing in clinical practice and to identify knowledge gaps. A literature search was performed and 110 articles were included that describe PK-guided dosing in patients with bleeding disorders, mostly hemophilia A. We defined two overarching themes, efficacy and feasibility, and discuss five topics within each theme. For each topic, barriers, facilitators and knowledge gaps were described. Although consensus was found with regard to some topics, contradicting reports were found for others, especially with respect to the efficacy of PK-guided dosing. These contradictions highlight the need for future research to elucidate current ambiguities.

Management of Severe Hemophilia A: Low-Dose Prophylaxis vs. On-Demand Treatment

INTRODUCTION

Prophylactic clotting factor infusion regimens to prevent bleeding and joint deformity has become the standard of care in severe hemophilia A patients.

AIM

To assess low-dose factor prophylaxis in our population as an alternative approach to managing severe hemophilia A.

METHODS

A prospective cohort study that included 68 hemophilia A patients divided into two groups, i.e., Prophylaxis and on-demand. The two groups were compared for annualized bleeding rate (ABR), hospitalization, units of factor VIII (FVIII) infused, or plasma products transfused, i.e., fresh frozen plasma (FFP) and cryoprecipitate (CP), and development of FVIII inhibitors.

RESULTS

Of the 68 patients recruited in this study, 25 (36.7%) were in the prophylaxis group, and 43(63.3%) were in the on-demand group. The on-demand group presented a higher median-IQR ABR [8(20-3) vs. 5(10-1.5), p-value 0.024], several hospitalizations (39.7% vs. 0, p-value 0.001), and inhibitor development (9.3% vs. 0, p-value 0.289) compared to the prophylaxis group. The prophylaxis approach demonstrated a significant negative correlation of ABR with FVIII prophylaxis (r=-0484, p=value=0.014). Moreover, no hospitalizations or inhibitor development was observed in the prophylaxis group. The estimated annual consumption of FVIII was 328 IU/kg/year in the on-demand group and 1662.6 IU/kg/year in the prophylaxis group. However, a highly significant difference in plasma product utilization was observed between the two groups, i.e., p-value <0.001 and 0.038 for FFP and CP, respectively.

CONCLUSION

Low-dose factor prophylaxis resulted in improved outcomes compared to on-demand treatment in terms of ABR, joint bleeding, hospitalization, and the development of inhibitors. This treatment approach should be adopted as an economically feasible alternative to high-dose Prophylaxis in resource-constrained countries.

Clinical outcomes of low-dose pharmacokinetic-guided extended half-life versus low-dose standard half-life factor VIII concentrate prophylaxis in haemophilia A patients

INTRODUCTION

Despite receiving standard half-life (SHL) factor VIII (FVIII) concentrates prophylaxis, some severe haemophilia A (HA) patients still encounter spontaneous breakthrough bleeding. Individualized pharmacokinetic (PK)-guided dosing of extended half-life (EHL) FVIII concentrates may reduce their bleeding events.

AIM

To compare clinical outcomes before and after switching low-dose prophylaxis using weight-based SHL FVIII to PK-guided EHL FVIII concentrates, taking into consideration of a trough FVIII activity at 1 IU/dl above natural baseline.

METHODS

In this single-centre prospective cohort, Thai severe or moderate HA (FVIII activity ≤3 IU/dl) patients receiving low-dose weight-based SHL FVIII prophylaxis were enrolled. After a 3-day wash-out period, participants underwent low-dose EHL FVIII prophylaxis with PK-based adjustment (myPKFiT^® ) for 6 months. The annualized bleeding rates (ABR), the annualized joint bleeding rates (AJBR), the haemophilia-specific quality-of-life (Haemo-QoL or Haemo-QoL-A) scores, the Hemophilia Joint Health Scores (HJHS) and the annualized FVIII consumption were compared between the two prophylactic periods.

RESULTS

Of 15 eligible subjects (mean age 18.7 ± 6.7 years), ABR, AJBR and HJHS were significantly reduced (mean differences of -11.1 ± 4.9 bleeds/year, -10.4 ± 5.2 joint bleeds/year and -5.1 ± 1.5 marks, respectively; P < .001 for all comparisons) after switching regimen. The quality-of-life scores had also improved (P = .001). Nonetheless, FVIII consumption tended to increase despite no statistical significance (means of 1240.9 ± 531.3 SHL FVIII IU/kg/year versus 1591.7 ± 438.9 EHL FVIII IU/kg/year; P = .05).

CONCLUSIONS

This is the first low-dose, PK-guided, EHL FVIII prophylaxis clinical study in Thailand. Benefits and practicability of this personalized regimen may support the implementation of regular FVIII prophylaxis in developing countries with budget constraints.

CLINICALTRIALS

gov NCT05281185.

The Limitations and Unmet Needs of the Five Cornerstones to Guarantee Lifelong Optimization of Prophylaxis in Hemophilia Patients

Prophylaxis to prevent bleeding is highly recommended for hemophilia patients. The development of new drugs and tools for modeling personalized prophylaxis provides the means for people with hemophilia to lead active lives with a quality of life comparable to that of nonhemophilic individuals. The choice of regimens must be made on a highly individual basis. Unfortunately, reference guides neither always concur in their recommendations nor provide directions to cover all possible scenarios. In this review, a group of experts identify the significant limitations and unmet needs of prophylaxis, taking advantage of their clinical experience in the disease, and supported by a rigorous literature update. To perform a more systematic and comprehensive search for gaps, the main cornerstones that influence decisions regarding prophylactic patterns were first identified.

Bleeding phenotype, joint status, physical activity, pharmacokinetics/medication properties, and adherence to treatment were considered as the primary mainstays that should allow physicians guiding prophylaxis to secure the best outcomes. Several challenges identified within each of these topics require urgent attention and agreement. The scores to assess severity of bleeding are not reliable, and lead to no consensus definition of severe bleeding phenotype. The joint status is to be redefined in light of new, more efficient treatments with an agreement to establish one scale as the unique reference for joint health. Further discussion is needed to establish the appropriateness of high-intensity physical activities according to patient profiles, especially because sustaining trough factor levels within the safe range is not always warranted for long periods. Importantly, many physicians do not benefit from the advantages provided by the programs based on population pharmacokinetic models to guide individualized prophylaxis through more efficient and cost-saving strategies. Finally, ensuring correct adherence to long-term treatments may be time-consuming for practitioners, who often have to encourage patients and review complex questionnaires.

In summary, we identify five cornerstones that influence prophylaxis and discuss the main conflicting concerns that challenge the proper long-term management of hemophilia. A consensus exercise is warranted to provide reliable guidelines and maximize benefit from recently developed tools that should notably improve patients' quality of life.

Cost-Effectiveness Analysis of Pharmacokinetic-Guided Prophylaxis Versus Standard Prophylaxis in Adults with Severe Hemophilia A in China

INTRODUCTION

Multiple studies have demonstrated the effectiveness of pharmacokinetic (PK)-guided individualized prophylaxis with human coagulation factor VIII (FVIII) compared with standard prophylaxis, but no studies have evaluated the economics of PK-guided prophylaxis in China. Hence, we conducted this study to assess the cost-effectiveness of PK-guided prophylaxis with recombinant FVIII (rFVIII) versus standard prophylaxis in Chinese adult patients with severe hemophilia A.

METHODS

A discrete event simulation model was developed to simulate 10,000 patients with hemophilia A who received rFVIII treatment over a 1-year time horizon. The standard prophylaxis rFVIII dose was 30 IU/kg by intravenous injection. The PK-guided prophylaxis dosage was adjusted for each patient to maintain FVIII trough level at 1-5 IU/dL. Dosing interval for both approaches was kept fixed at 48 h. The health outcomes included annual joint bleed rate (AJBR) and quality-adjusted life years (QALYs). The model considered the costs of drug. Incremental cost-effectiveness ratio (ICER) was estimated and scenario analysis was performed.

RESULTS

A total of 94.3% of patients receiving PK-guided individualized prophylaxis achieved the goal of maintaining the trough concentration at 1-5 IU/dL compared with 62.7% on standard prophylaxis. AJBR and QALYs gained in PK-guided and standard prophylaxis were 1.527 vs 1.601, and 0.8384 vs 0.8383, respectively. Costs of drug prophylaxis and costs of treatment for bleeding events in PK-guided prophylaxis (148,641.47 USD; 4546.43 USD) were lower than those in standard prophylaxis (159,620.93 USD; 4753.39 USD). An average saving of USD 11,186.47 was obtained by the PK-guided approach. The prophylaxis treatment scenarios were the most influential factors.

CONCLUSION

PK-guided individualized prophylaxis appeared to be a dominant treatment compared with standard prophylaxis, with slightly higher QALYs but lower total costs.

Treatment Individualization Using Pharmacokinetic Studies and Joint Ultrasound Imaging in Pediatric Patients With Hemophilia

Hemophilia is characterized by bleeding diathesis, primarily affecting the joints. Prophylactic use of missing factor aims at limiting the number of bleeds and, in the long term, the risk of permanent joint damage. However, standard prophylactic regimens are usually applied empirically, not adjusting for variations in bleeding phenotype or drug metabolism. Aim of the present study was to evaluate the need for individualizing prophylaxis, with guidance of pharmacokinetic (PK) studies and joint ultrasound in a setting of everyday clinical practice. To evaluate adequacy of applied regimens, joint status was assessed using the Hemophilia Joint Health Score as well as ultrasound imaging, while PK studies were performed using the Web-Accessible Population Pharmacokinetic Service-Hemophilia. Imaging results were consistent with early joint damage in a large proportion of pediatric patients, whereas PK measures were indicative of inadequate prophylaxis in many cases-despite the limited number of bleeds reported by patients. The study revealed the need for prophylaxis adjustment in the majority of patients. Real world data confirm that traditional prophylaxis is often unable to achieve therapeutic goals, while an individualized approach, guided by the use of novel modalities, may be of great benefit to young hemophilia patients.

Combining factor VIII levels and thrombin/plasmin generation: a population pharmacokinetic-pharmacodynamic model for patients with hemophilia A

Aims

Prophylactic treatment of haemophilia A patients with factor VIII (FVIII) concentrate focuses on maintaining a minimal trough FVIII activity level to prevent bleeding. However, due to differences in bleeding tendency, the pharmacokinetic (PK)‐guided dosing approach may be suboptimal. An alternative approach could be the addition of haemostatic pharmacodynamic (PD) parameters, reflecting a patient's unique haemostatic balance. Our aim was to develop a population PK/PD model, based on FVIII activity levels and Nijmegen Haemostasis Assay (NHA) patterns, a global haemostatic assay that measures thrombin/plasmin generation simultaneously.

Methods

PK/PD measurements were collected from 30 patients treated with standard half‐life FVIII concentrate. The relationship between FVIII activity levels and the thrombin/plasmin generation parameters (thrombin potential, thrombin peak height and plasmin peak height), were described by sigmoidal E_max functions.

Results

The obtained EC₅₀ value was smallest for the normalized thrombin potential (11.6 IU/dL), followed by normalized thrombin peak height (56.6 IU/dL) and normalized plasmin peak height (593 IU/dL), demonstrating that normalized thrombin potential showed 50% of the maximal effect at lower FVIII activity levels. Substantial inter‐individual variability in the PD parameters, such as EC₅₀ of thrombin potential (86.9%) was observed, indicating that, despite similar FVIII activity levels, haemostatic capacity varies significantly between patients.

Conclusion

These data suggest that dosing based on patients' individual PK/PD parameters may be beneficial over dosing solely on individual PK parameters. This model could be used as proof‐of‐principle to examine the application of PK/PD‐guided dosing. However, the relation between the PD parameters and bleeding has to be better defined.

Addressing unmet needs in rare bleeding disorders: selected poster extracts of recent research in hemophilia A and von Willebrand disease presented at the 14th Annual Congress of the European Association for Haemophilia and Allied Disorders (EAHAD) (Feb 3-5, 2021; virtual congress)

Hemophilia A and von Willebrand disease (VWD) are inherited rare bleeding disorders affecting normal hemostasis. Patients with VWD, especially those with severe disease types, share some similarities to patients with hemophilia A in their burden of disease: they suffer from an increased risk of potentially severe and life-threatening bleeds and associated long-term consequences, such as impaired joint health and overall lower quality of life. However, the two bleeding disorders differ in their primary cause and affected patient population, and comprise a range of different bleeding phenotypes with varying unmet needs. Generating scientific evidence to advance health care for patients with rare bleeding disorders is challenging due to the low prevalence and heterogeneity of affected populations, including patient demographics and symptom severities. Innovative study designs are needed to adequately answer relevant scientific questions and address patients' unmet needs. In support of advancing clinical outcomes and treatment options for these patients, at the recent EAHAD 2021 annual congress, novel approaches and data from clinical and real-world observational studies, as well as systematic literature analyses, were presented. Herein, extracts from seven selected posters reporting research in hemophilia A and VWD funded by Takeda are discussed.

Clinical benefits of a Bayesian model for plasma-derived factor VIII/VWF after one year of pharmacokinetic-guided prophylaxis in severe/moderate hemophilia A patients

INTRODUCTION

Individual pharmacokinetic (PK) profiling in hemophilia A (HA) helps to individualize prophylaxis using population PK models (popPK). A specific popPK model for plasma-derived factor VIII containing von-Willebrand Factor (pdFVIII/VWF) was developed.

AIM

To compare standard versus PK-driven prophylaxis, using a generic or a specific popPK model for pdFVIII/VWF.

MATERIALS AND METHODS

A prospective study conducted in HA patients in prophylaxis with pdFVIII/VWF (Fanhdi®) comparing three one-year study periods: (1) standard prophylaxis, (2) PK-guided prophylaxis using a generic pdFVIII popPK model which described FVIII activity irrespective of FVIII concentrate, and (3) PK-guided prophylaxis with specific pdFVIII/VWF popPK model. PK parameters analyzed were half-life, trough levels (TL) at 24, 48 and 72 h, and time to reach FVIII levels of 1, 2, 5% (T5%). Clinical outcomes were dose/kg, FVIII consumption, annualized bleeding rate (ABR), annualized joint bleeding rate (AJBR), spontaneous and traumatic bleeds.

RESULTS

Of the 30 analyzed patients, 28 had severe HA and the median age was 31.2. Fifteen patient's prophylaxis doses were PK-adjusted. After the generic PK-guided prophylaxis period, younger patients showed more joint bleeds, a shorter half-life, and lower TL48, TL72 and T5%. Using the specific pdFVIII/VWF popPK model compared with standard prophylaxis, a lower spontaneous AJBR was observed in the entire cohort and in patients aged >15 years. Additionally, lower spontaneous ABR was reported in patients aged ≤15 years comparing specific and generic models.

CONCLUSIONS

PK-guided prophylaxis with a specific pdFVIII/VWF popPK model allowed treatment individualization and improved bleeding control in routine clinical practice, especially in younger patients with short pdFVIII/VWF half-lives.

Pharmacokinetics and complementary evaluation system-based guidance on prophylaxis of paediatric patients with haemophilia A in China with Kovaltry: protocol of the LEAP study

INTRODUCTION

Haemophilia A is a rare inherited bleeding disease caused by the deficiency of coagulation factor VIII (FVIII). The main treatment protocol is to administer regular exogenous FVIII concentrate infusions. With the discovery of variability in individualised pharmacokinetics (PK) and bleeding phenotype, the previous weight-based approach needs to be replaced by more advanced PK-tailored prophylaxis with an accurate evaluation system. In this study, we combine individualised PK profiles and a complementary evaluation system to guide prophylaxis in paediatric patients with haemophilia A.

METHODS AND ANALYSIS

This is a single-centre, prospective single-arm study. The aim of this study is to assess the effectiveness of a new strategy combining PK and a complementary evaluation system to treat haemophilia A in Chinese paediatric patients. Sixty paediatric patients with haemophilia will be recruited. After PK testing, they will receive a PK-guided stepup prophylaxis in the next 2 years. The dosing regimen will be determined according to individualised PK profiles and complementary evaluation findings. Related indicators at the end of the study will be compared with the values at treatment initiation to examine the effectiveness of this new strategy. The demographic data of the investigated patients will be summarised by descriptive statistics. Quantitative data will be described by summary statistics, including arithmetic median, range, mean and arithmetic SD. Analyses will use t-test to compare indicators such as bleeding rate and imaging score at both ends of the study as well as during follow-up.

ETHICS AND DISSEMINATION

The study has been approved by the Ethics Committee of Beijing Children's Hospital (Number 2020-Z-095). The findings will be presented at international meetings such as World Federation of Hemophilia World Congress. Related manuscripts will be submitted to peer-review journals such as Blood and Hemophilia.

TRIAL REGISTRATION NUMBER

ChiCTR2000037821; Pre-results.

Development and Validation of a Population-Pharmacokinetic Model for Rurioctacog Alfa Pegol (Adynovate®): A Report on Behalf of the WAPPS-Hemo Investigators Ad Hoc Subgroup

BACKGROUND AND OBJECTIVE

Rurioctacog alfa pegol (Adynovate) is a modified recombinant factor VIII concentrate used for treating hemophilia A. Aiming to improve treatment tailoring on the Web-Accessible Population Pharmacokinetic Service-Hemophilia (WAPPS-Hemo) platform for patients of all ages treated with Adynovate, we have developed and evaluated a population pharmacokinetic (PopPK) model. On the platform, PopPK models are used as priors for Bayesian forecasting that derive individual PK of hemophilia patients and are subsequently used for personalized dose regimen design.

METHODS

Factor activity measurements and demographic covariate data from patients infused with Adynovate were extracted from the WAPPS-Hemo database. Evaluations testing the appropriateness of Bayesian forecasting included 10-fold cross validation, a limited sampling analysis (LSA), and an external evaluation using additional independent data extracted from the WAPPS-Hemo database at a later date.

RESULTS

The model was constructed using 650 plasma factor activity observations (555 one stage assay and 95 chromogenic assay - 4.6% below limit of quantification) measured in 154 patients from 36 hemophilia centres. A two-compartment model including between subject variability on clearance and central volume was selected as the base model. Covariates were fat free mass on clearance and central volume, age on clearance and assay type on activity. The final model was well-suited to predict PK parameters of new individuals (n = 26) from sparse observations.

CONCLUSIONS

The development of a PopPK model for Adynovate using real-world data increases the covariate space (e.g. age) beyond what is possible from clinical trial data. This model is available on the WAPPS-Hemo platform for tailoring treatment in hemophilia A patients.

Pharmacokinetic variability of factor VIII concentrates in Chinese pediatric patients with moderate or severe hemophilia A

IMPORTANCE

The use of factor VIII (FVIII) concentrates under pharmacokinetic (PK) guidance has become the main approach for treatment of hemophilia. However, limited PK research has been conducted in Chinese pediatric patients.

OBJECTIVE

To investigate the PK parameters of various FVIII concentrates in Chinese pediatric patients.

METHODS

Seventy-nine patients were enrolled (28 treated with Kogenate FS®, 23 treated with Advate ®, and 28 treated with GreenMono™). All enrolled patients participated in single-dose PK analysis after at least a 3-day washout period. Blood samples were collected predose, as well as at 1 h, 9 h, 24 h, and 48 h after infusion; FVIII levels were measured using a one-stage clotting assay. von Willebrand Factor Antigen (VWF:Ag) levels and blood types were also determined. PK parameters were evaluated by WAPPS-Hemo.

RESULTS

Mean values of terminal elimination half-life time (t1/2) for the Kogenate FS®, Advate®, and GreenMono™ FVIII groups were 12.24 h, 10.18 h, and 9.62 h; median clearance values were 4.16, 6.23, and 5.11 mL·kg-1·h-1; and median in vivo recovery values were 1.97, 1.55, and 1.61 IU/dL per IU/kg. Longer t1/2, higher in vivo recovery, and lower clearance were observed in patients with higher VWF:Ag level who were treated with recombinant concentrates.

INTERPRETATION

Chinese pediatric patients with hemophilia had FVIII PK characteristics similar to those previously observed in non-Chinese children, including large variation among individuals. VWF:Ag level and FVIII brand were associated with differences in FVIII PK. Thus, PK-guided dosing should be used to optimize individualized therapy in Chinese children.

A Practical, One-Clinic Visit Protocol for Pharmacokinetic Profile Generation with the ADVATE myPKFiT Dosing Tool in Severe Hemophilia A Subjects

Standard pharmacokinetic (PK) assessments are demanding for persons with hemophilia A, requiring a 72-hour washout and 5 to 11 timed blood samples. A no-washout, single-clinic visit, sparse sampling population PK (PPK) protocol is an attractive alternative. Here, we compared PK parameters obtained with a traditional washout, 6-sampling time point PPK protocol with a no-washout, single-clinic visit, reverse 2-sampling time point PPK protocol in persons with severe hemophilia A (SHA) receiving ADVATE. A total of 39 inhibitor-negative males with SHA (factor VIII activity [FVIII:C] < 2%) were enrolled in a prospective sequential design PK study. Participants completed a washout, 6-sampling time point PPK protocol as well as a no-washout, reverse 2-sampling time point protocol, with samples taken during a single 3-hour clinic visit 24 hours post home infusion of FVIII and then 3 hours post infusion in clinic. FVIII:C levels were analyzed by one-stage and chromogenic assays; blood group and von Willebrand factor antigen (VWF:Ag) were determined; and PK parameters were analyzed using the ADVATE myPKFiT dosing tool. There was moderate to almost perfect agreement for the PK parameters obtained with the 2- and the 6- point PPK protocols using a one-stage FVIII:C assay and a substantial to almost perfect agreement using a chromogenic FVIII:C assay. Significant associations between specific PK parameters and blood group and VWF:Ag were observed. The no-washout, single-clinic visit, reverse 2-sampling time point PPK protocol can be used in the routine clinical setting since it demonstrates sufficient accuracy compared with the more demanding and less practical washout, 6-sampling time point PPK protocol in persons with SHA receiving ADVATE.

Pharmacodynamic monitoring of factor VIII replacement therapy in hemophilia A: Combining thrombin and plasmin generation

BACKGROUND

Clinical severity of hemophilia A (HA) varies, possibly due to interplay of many factors in the hemostatic pathway. Pharmacokinetic monitoring of factor VIII (FVIII) replacement therapy in HA patients consists of measuring FVIII activity levels and subsequent dose adjustment. The Nijmegen Hemostasis Assay (NHA) measures thrombin generation (TG) and plasmin generation (PG).

OBJECTIVE

To determine differences in TG and PG between HA patients before and during a pharmacokinetic study and identify best parameters to develop a pharmacodynamic model.

METHODS

Twenty-five HA patients (baseline FVIII < 1-9 IU/dL) underwent a pharmacokinetic study with a single dose of 25-50 IU/kg standard half-life FVIII concentrate. At baseline and after administration of FVIII TG and PG parameters were measured with the NHA.

RESULTS

FVIII activity level increased from median 1.0 IU/dL (interquartile range < 1.0-6.0) to 71 IU/dL (62-82) 15 minutes after administration and decreased to 15 IU/dL (10-26) at 24 hours. TG was enhanced simultaneously, with thrombin peak height (TPH) increasing from 22nM (15-35) to 222nM (159-255), and thrombin potential (TP) from 404nM/min (undetectable-876) to 1834nM/min (1546-2353). Twenty-four hours after infusion, TG parameters remained high (TPH 73nM [58.5-126.3]; TP 1394nM/min [1066-1677]) compared to FVIII activity level. PG showed hyperfibrinolysis in severe HA patients compared to mild patients and controls, which normalized after FVIII supplementation.

CONCLUSION

HA patients showed clear differences in baseline TG and PG despite having comparable FVIII activity levels. These results reveal a discrepancy between FVIII activity level and TG, in which the latter may be a better parameter to monitor individualized treatment in HA patients.

Assessment of Self-Image With the Offer Self-Image Questionnaire in Adolescents With Hemophilia: A Single-Center Experience

BACKGROUND

Hemophilia, which is a chronic illness associated with recurrent bleeding, may occur with psychosocial and behavioral problems.

AIM

The aim of this study was to evaluate the clinical characteristics and demographic features and changes in the self-image of adolescents with hemophilia.

MATERIALS AND METHODS

Data about hemophilia type, the severity of hemophilia, secondary prophylaxis received, and annual bleeding rate (ABR) were recorded from patient files. Hemophilia Joint Health Score (HJHS) and the Offer Self-Image Questionnaire (OSIQ) (as a measure of self-esteem) were applied to hemophilia patients and a healthy control group.

RESULTS

Thirty-two hemophilia patients (mean age=16.2±3.06 y) and 35 healthy male individuals (mean age=16.02±1.4 y) were enrolled in the study. Hemophilia patients had lower total OSIQ score than their peers (P=0.007). There was no difference between patients who received and who did not receive secondary prophylaxis (P=0.408) in terms of total OSIQ score. The median total OSIQ score of patients with pathologic HJHS (>0 points) was lower than that of patients with normal HJHS (0 points) (P=0.010). The median of ABR was 6 (range: 0 to 20) in the whole hemophilia group. There were no differences between hemophilia patients with ABR≤4 and >4 (P=0.084). All of the subscale parameters of the OSIQ were lower for hemophilia patients compared with their peers, besides one. The subscale of sexuality attitudes was better for hemophilia patients than for the healthy control group (P=0.028).

CONCLUSIONS

Low self-esteem in hemophilia patients indicates the importance of lifelong psychosocial support. Patients with pathologic HJHS are at risk of low-esteem. Using OSIQ with HJHS during follow-up of hemophilia patients may be useful for management.

Pharmacokinetic-tailored approach to hemophilia prophylaxis: Medical decision making and outcomes

BACKGROUND

Clinical application of population pharmacokinetics (popPK) is of increasing interest to patients with hemophilia, providers, and payers. Routine use of popPK profiles in factor replacement prophylaxis decision making has the potential to maintain or improve efficacy and reduce product consumption.

AIM

To investigate the feasibility of implementation and longitudinal assessment of pharmacokinetic (PK)-tailored prophylaxis in routine clinical practice for hemophilia A and to describe factors that influence decision making for prescribed hemophilia prophylaxis.

METHODS

This longitudinal, multicenter, prospective feasibility study of children and adults with hemophilia A without inhibitors used the Web Accessible Population Pharmacokinetic Service-Hemophilia (WAPPS-Hemo) to generate PK profiles. Assessments over 12 weeks captured data on prescribed prophylaxis, popPK tool use, provider decision making, and patient-reported outcomes.

RESULTS

Eighteen participants aged 6 to 39 years enrolled; half used extended half-life concentrates. Patient interest in their PK centered on general curiosity followed by a desire for participation in physical activity and decrease in infusion frequency. Providers used the WAPPS clinical calculator feature to simulate prophylaxis regimens under different dose, infusion, and trough conditions. Most targeted troughs were 1 to 3 IU/dL. The feasibility assessment demonstrated challenges with patient recruitment; however, the majority of participants successfully completed study assessments meeting feasibility targets.

CONCLUSION

A larger-scale study powered to evaluate the impact of PK-tailored prophylaxis on clinical and patient-reported outcomes is feasible with study design modifications to support increased recruitment rate. Shared decision making incorporating patient and provider goals is important and facilitated by regimen simulations with the clinical calculator.

Economic impact model of delayed inhibitor development in patients with hemophilia a receiving emicizumab for the prevention of bleeding events

Aims: Cumulative exogenous factor VIII (FVIII) exposure is an important predictor of developing neutralizing antibodies (inhibitors) to FVIII in patients with persons with hemophilia A (PwHA). The aim of this study was to model the costs of emicizumab versus FVIII prophylaxis and total treatment costs for patients with severe HA.Materials and Methods: An Excel-based decision model was developed to calculate cumulative costs in PwHA over a 20-year time horizon from the US payer perspective. The model considered persons with severe HA beginning at age 12 months with no prior FVIII exposure and initiating prophylaxis with emicizumab or FVIII. PwHA could develop inhibitors on accumulation of 20 FVIII exposure days. PwHA with inhibitors replaced FVIII with bypassing agents until inhibitors resolved spontaneously, following immune tolerance induction (ITI), or at the end of the time horizon. The primary model outcome was the difference in emicizumab versus FVIII treatment costs in 2019 USD. Sensitivity analyses were performed to test the robustness of results.Results: Total incremental cost over 20 years was -$1,945,480 (emicizumab arm, $4,919,058; FVIII arm, $6,864,538). Prophylaxis costs (emicizumab arm, $4,096,105; FVIII arm, $6,290,919) comprised the majority of costs in both groups, followed by breakthrough bleed treatment for the FVIII arm ($342,652) and ITI costs for the emicizumab arm ($733,671). Higher costs in the FVIII group reflected earlier inhibitor development (FVIII, 4 months; emicizumab, 162 months) and switch to bypassing agents.Limitations: The model design reflects a simplified treatment pathway for patients with severe HA who initiate FVIII or emicizumab prophylaxis. In the absence of clinical data, a key conservative assumption of the model is that patients receiving emicizumab and FVIII prophylaxis have the same risk of developing inhibitors.Conclusions: This study suggests that prophylaxis with emicizumab results in cost savings compared to FVIII prophylaxis in HA.

Clinical application of Web Accessible Population Pharmacokinetic Service-Hemophilia (WAPPS-Hemo): Patterns of blood sampling and patient characteristics among clinician users

BACKGROUND

Use of population pharmacokinetics (PopPK) to facilitate PK-informed prophylaxis in clinical practice has gained momentum among haemophilia providers due to the accessibility of tools such as the Web Accessible Population Pharmacokinetic Service-Hemophilia (WAPPS-Hemo) and availability of extended half-life (EHL) factor concentrates. It is unknown how clinicians implement PopPK.

AIM

To investigate the evolution of PopPK use in clinical practice by comparing blood sampling strategies, patient features, and factor group between initial and recent periods of WAPPS-Hemo availability.

METHODS

PK data for haemophilia A and haemophilia B patients from two time periods were extracted from the WAPPS-Hemo database: early availability (10/2015-09/2016) and recent use (10/2017-09/2018). We compared patient characteristics (age, body weight, haemophilia type), product type and dose, and blood sampling times between the time frames.

RESULTS

Over 1900 eligible infusions were submitted to WAPPS-Hemo during the periods studied, with 85% representing FVIII concentrates. In the recent cohort, PK profiles were requested for younger patients (median age 18 vs 26 years), with increased proportional EHL FVIII use (29% vs 14% of infusions). High-use centres generally submitted fewer blood samples per infusion than non-high-use centres, although the number of samples collected by non-high-use centres decreased significantly over time. During both periods, blood sample timing was generally consistent with ISTH recommended windows.

CONCLUSION

The use of WAPPS-Hemo by haemophilia providers grew by over threefold between the time periods investigated. While sampling times have included key time points proposed first by Björkman since early WAPPS-Hemo usage, a trend towards minimizing sampling was observed.

Bayesian Forecasting Utilizing Bleeding Information to Support Dose Individualization of Factor VIII

Bayesian forecasting for dose individualization of prophylactic factor VIII replacement therapy using pharmacokinetic samples is challenged by large interindividual variability in the bleeding risk. A pharmacokinetic‐repeated time‐to‐event model‐based forecasting approach was developed to contrast the ability to predict the future occurrence of bleeds based on individual (i) pharmacokinetic, (ii) bleeding, and (iii) pharmacokinetic, bleeding and covariate information using observed data from the Long‐Term Efficacy Open‐Label Program in Severe Hemophilia A Disease (LEOPOLD) clinical trials (172 severe hemophilia A patients taking prophylactic treatment). The predictive performance assessed by the area under receiver operating characteristic (ROC) curves was 0.67 (95% confidence interval (CI), 0.65–0.69), 0.78 (95% CI, 0.76–0.80), and 0.79 (95% CI, 0.77–0.81) for patients ≥ 12 years when using pharmacokinetics, bleeds, and all data, respectively, suggesting that individual bleed information adds value to the optimization of prophylactic dosing regimens in severe hemophilia A. Further steps to optimize the proposed tool for factor VIII dose adaptation in the clinic are required.

BAY 94-9027 prophylaxis is efficacious and well tolerated for up to >5 years with extended dosing intervals: PROTECT VIII extension interim results

Introduction

BAY 94‐9027 is an extended‒half‐life, site‐specifically PEGylated, B‐domain‒deleted recombinant factor VIII (FVIII). The PROTECT VIII main study demonstrated efficacy of bleed control using extended‐interval prophylaxis with BAY 94‐9027 for 36 weeks.

Aim

To report long‐term efficacy and safety of prophylaxis with BAY 94‐9027 in a descriptive analysis of the ongoing PROTECT VIII extension with a total treatment time of up to >5 years.

Methods

Previously treated males aged 12‐65 years with severe haemophilia A who completed the PROTECT VIII main study were eligible for the open‐label extension. Patients received on‐demand treatment or prophylaxis (30‒40 IU/kg twice weekly, 45‒60 IU/kg every 5 days, or 60 IU/kg every 7 days) and could switch regimens as needed.

Results

Patients (N = 121; on demand, n = 14; prophylaxis, n = 107) accumulated a median (range) of 3.9 years (297‒1965 days) and 223 (23‒563) total exposure days by 31 January 2018. During the extension, median (quartile [Q]1; Q3) annualized bleeding rates (ABRs) for total bleeds were 1.6 (0.3; 4.6) for patients receiving prophylaxis and 34.1 (20.3; 36.6) for patients receiving on‐demand treatment. ABRs for twice‐weekly (n = 23), every‐5‐days (n = 33), every‐7‐days (n = 23) and variable frequency (n = 28) treatments were 1.7, 1.2, 0.7 and 3.1, respectively. Of prophylaxis patients, 20.6% were bleed‐free throughout the extension (median time, 3.2 years), and 51.0% were bleed‐free during the last 6 months. No patients developed FVIII inhibitors.

Conclusions

BAY 94‐9027 prophylaxis was efficacious and well tolerated with dosing intervals up to every 7 days for a median (range) of 3.9 years (0.8‐5.4 years).

Regional variation and cost implications of prescribed extended half-life factor concentrates among U.S. Haemophilia Treatment Centres for patients with moderate and severe haemophilia

BACKGROUND

Extended half-life (EHL) factor VIII (FVIII) and IX (FIX) products are intended to decrease the burden of prophylaxis for patients with haemophilia A or B. Whether these newer concentrates have led to meaningful clinical practice change remains vague.

AIM

To characterize the longitudinal use of standard (SHL) and EHL factor concentrates at haemophilia treatment centres (HTCs), using the ATHNdataset, a US database of 138 ATHN-affiliated HTCs.

METHODS

Factor concentrate use among moderate and severe haemophilia A and B patients without inhibitors was analysed at three time points over 18 months.

RESULTS

Use of EHL concentrates rose from 10% of patients to 22% during this study. EHL FVIII prophylaxis is prescribed to the minority of patients, 28%; EHL FIX now predominates for prophylaxis, 52%. Rates of prescribed EHL products varied significantly by age group and HTC region. Median prescribed prophylaxis for SHL compared to EHL products was FVIII 6240 and 5200 and FIX 6968 and FIX 3900 IU/kg/y, respectively. On-demand EHL use has grown but has minimal contribution to overall usage (2%).

CONCLUSION

Haemophilia treatment centre region and patient age impact the rate of adoption of EHL products; however, EHL prescribing continues to rise nationally, particularly for EHL FIX. Careful attention to annual cost of prophylaxis is imperative as the decrease in median EHL prophylaxis consumption is not offset by the higher unit cost of these products. It is unclear how further growth in use of EHLs will be impacted by emerging non-factor replacement and gene therapies.