Kinetic Modeling for BT200 to Predict the Level of Plasma-Derived Coagulation Factor VIII in Humans

Lack of Factor VIII (FVIII) concentrates is one of limiting factors for Hemophilia A prophylaxis in resource-limited countries. Rondaptivon pegol (BT200) is a pegylated aptamer and has been shown to elevate the level of von Willebrand Factor (VWF) and FVIII in previous studies. A population pharmacokinetic model for BT200 was built and linked to the kinetic models of VWF and FVIII based on reasonable assumptions. The developed PK/PD model for BT200 described the observed kinetic of BT200, VWF, and FVIII in healthy volunteers and patients with mild-to-moderate hemophilia A from two clinical trials. The developed model was evaluated using an external dataset in patients with severe hemophilia A taking recombinant FVIII products. The developed and evaluated PK/PD model was able to describe and predict concentration-time profiles of BT200, VWF, and FVIII in healthy volunteers and patients with hemophilia A. Concentration-time profiles of FVIII were then predicted following coadministration of plasma-derived FVIII concentrate and BT200 under various dosing scenarios in virtual patients with severe hemophilia A. Plasma-derived products, that contain VWF, are more accessible in low-resource countries as compared to their recombinant counterparts. The predicted time above 1 and 3 IU/dL FVIII in one week was compared between scenarios in the absence and presence of BT200. A combination dose of 6 mg BT200 once weekly plus 10 IU/kg plasma-derived FVIII twice weekly maintained similar coverage to a 30 IU/kg FVIII thrice weekly dose in absence of BT200, representing only 22% of the FVIII dose per week.

Estimating the impact of improved management of haemophilia a on clinical outcomes and healthcare utilisation and costs

OBJECTIVE

Haemophilia A (HA) is associated with high clinical and healthcare burden. We developed an Excel-based model comparing current practice to improved management in severe HA patients currently managed on demand (OD). Outcomes included short- and long-term bleed events. Expected annual bleeds were estimated based on locally-derived OD annualised bleed rate (ABR), adjusted by relative prophylaxis-related ABRs (published literature). The objective of our study was to explore the impact of improving HA prophylaxis in target countries with limited published data (Algeria, Argentina, Chile, India, Malaysia, Mexico, Taiwan and Thailand). Bleed-related healthcare resource use (HCRU) and costs were estimated as a function of bleed type, with inputs obtained from local expert estimates. Clotting factor concentrates (CFC) consumption related to treatment and prophylaxis was estimated based on locally relevant dosing. CFC costs were not included.

RESULTS

When 20% of OD patients were switched to prophylaxis, projected reduction in bleeds was estimated between 3% (Taiwan) through 14% (Algeria and India); projected reductions in hospitalisations ranged from 3% (Taiwan) through 15% (India). Projected HCRU-related annual cost savings were estimated at USD 0.45 m (Algeria), 0.77 m (Argentina), 0.28 m (Chile), 0.13 m (India), 0.29 m (Malaysia), 2.79 m (Mexico), 0.15 m (Taiwan) and 0.78 m (Thailand). Net change in annual CFC consumption ranged from a 0.05% reduction (Thailand) to an overall 5.4% increase (Algeria). Our model provides a flexible framework to estimate the clinical and cost offsets of improved prophylaxis. Modest increase in CFC consumption may be an acceptable offset for improvements in health and healthcare capacity in resource constrained economies.

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.

Clinical outcome and incidence of inhibitor development in severe hemophilia patients receiving low-dose prophylaxis: a 3-year follow-up study in Senegal, West Africa

INTRODUCTION

In Africa, where access to diagnosis and treatment of hemophilia is the lowest in the world, prophylaxis is rarely used in preference to on-demand treatment. There are limited data of prophylaxis treatment from sub-Saharan Africa. The aim of this study was to evaluate clinical outcomes and inhibitor development in people with hemophilia receiving low-dose prophylaxis (LDP) in a sub-Saharan African setting.

METHODS

We conducted a three-year prospective study. A once or twice weekly prophylaxis regimen of 25 IU/kg of rFVIIIFc or 30 IU/kg of rFIXFc was given to Hemophilia A and B, respectively. We evaluated clinical outcomes and inhibitors occurrence, determined by screening and titration using the Nijmegen technique.

RESULTS

A total of 15 patients were included in the LDP regimen. The mean age was 6.3 years (1.5 - 10). A significant reduction was noted in the annualized bleeding rate, from 7.53 to 1.33 (p = 0.0001); the annualized joint bleeding rate passed from 3.6 to 1.4 (p = 0.001) and the proportion of severe bleeding, from 86.1% to 16.7% (p = 0.0001). The Hemophilia Joint Health Score (HJHS) moved from 9.6 to 3.4 (p = 0.0001) and the Functional Independence Score in Hemophilia (FISH) improved from 25.8 to 30.9 (p = 0.0001). School absenteeism decreased from 7.33% to 2.59%. Adherence to prophylaxis was 89.5% versus 60%. Consumption was 580 IU/kg/year versus 1254.6 IU/kg/year before and after prophylaxis, respectively. Incidence of inhibitors was 23% (3 /13 HA).

CONCLUSION

The LDP in Hemophilia improves the clinical outcome without a surplus risk of inhibitor development. Using extended half-life clotting factor concentrates (CFCs) is better for prophylaxis in resource-limited countries, as they allow better compliance in treatment.

Low dose prophylaxis and antifibrinolytics: Options to consider with proven benefits for persons with haemophilia

INTRODUCTION

Prophylaxis has become standard of care for persons with severe phenotype haemophilia (PWsH). However, 'standard prophylaxis' with either factor or non-factor therapies (emicizumab) is prohibitively expensive for much of the world. We sought to evaluate whether haemophilia care can be provided at a lower cost yet achieve good results using Lower dose/Lower frequency prophylaxis (LDP) and with increasing use of antifibrinolytics (Tranexamic acid and Epsilon amino caproic acid).

METHODS

We identified 12 studies that collectively included 335 PWsH using LDP. Additionally, we undertook a literature search regarding the benefits of antifibrinolytics in haemophilia care.

RESULTS

Identified studies show that LDP is far superior to no prophylaxis (On demand [OD] therapy) resulting in significant patient benefits. Patients on LDP showed (in comparison to patients OD) on average: 72% less total bleeds; 75% less joint bleeds; 91% less days lost from school; 77% less hospital admission days; and improved quality of life measures. These benefits come at similar or only slightly higher (< 2-fold greater) costs than OD therapy. Antifibrinolytics are effective adjunctive agents in managing bleeds (oral, nasal, intracranial, possibly other) and providing haemostasis for surgeries (particularly oral surgeries). Antifibrinolytics can substitute for more expensive factor concentrates or can reduce the use of such concentrates. There is evidence to show that antifibrinolytics may be used in conjunction with factor concentrates/emicizumab for more effective/less costly prophylaxis.

CONCLUSIONS

The use of LDP along with appropriate and increased use of antifibrinolytics offers less resourced countries good options for managing patients with haemophilia.

Predicting Individual Changes in Terminal Half-Life After Switching to Extended Half-Life Concentrates in Patients With Severe Hemophilia

Predicting individual effects of switching from standard half-life (SHL) to extended half-life (EHL) FVIII/FIX concentrates is pivotal in clinical care, but large-scale individual data are scarce. The aim of this study was to assess individual changes in terminal half-life (THL) after switching to EHL concentrates and identifying determinants of a clinically relevant THL extension in people with severe hemophilia. Data from participants with pharmacokinetic studies on both SHL and EHL were extracted from the Web-Accessible Population Pharmacokinetics Service (WAPPS) database and stratified according to hemophilia type and age groups (children/adults). A 30% increase in THL was considered clinically relevant. Predictors of a relevant increase were identified using logistic regression. Data from 688 persons with severe hemophilia (2174 infusions) were included: 89% hemophilia A; median age: 21.7 (interquartile range [IQR]: 11.5–37.7); positive inhibitor history: 11.7%. THL increased by 38% (IQR: 17%–67%) and 212% (139%–367%) for hemophilia A and B, respectively. All EHL-FIX concentrate users showed clinically relevant THL extension. However, 40% (242/612) of people with hemophilia A showed limited extension or decrease in THL after switching. Relevant FVIII-THL extension was predicted by short baseline THL and blood group non-O in both children and adults. In conclusion, clinically relevant THL extension was observed in all 75/76 participants switching to EHL-FIX, and in 60% of 612 switching to EHL-FVIII. Short THL on SHL-FVIII and blood group non-O were identified as predictors for a relevant THL increase after switching to EHL-FVIII. Individualized pharmacokinetic assessment may guide clinical decision-making when switching from SHL to EHL-FVIII.

Terminal half-life of FVIII and FIX according to age, blood group and concentrate type: Data from the WAPPS database

BACKGROUND

Real-life data on pharmacokinetics of factor (F) VIII/IX concentrates, especially extended half-life (EHL), concentrates in large cohorts of persons with hemophilia are currently lacking.

OBJECTIVES

This cross-sectional study aimed to establish reference values for terminal half-life (THL) for FVIII/IX concentrates according to concentrate type, age, blood group and inhibitor history.

PATIENTS/METHODS

Data were extracted from the Web-Accessible Population Pharmacokinetics Service database. Groups were compared by nonparametric tests. THL was modelled according to patient characteristics and concentrate type.

RESULTS

Infusion data (n = 8022) were collected from 4832 subjects (including 2222 children) with severe hemophilia (age: 1 month-85 years; 89% hemophilia A; 34% using EHL concentrates, 9.8% with history of inhibitors). THL of FVIII-EHL was longer than of FVIII standard half-life (SHL; median 15.1 vs. 11.1 h). FVIII-THL was dependent on age, concentrate type, blood group, and inhibitor history. THL of FIX-EHL was longer than of FIX-SHL (median 106.9 vs. 36.5 h). FIX-THL increased with age until 30 years and remained stable thereafter. FVIII-THL was shorter in subjects with blood group O. THL was decreased by 1.3 h for FVIII and 22 h for FIX in subjects with a positive inhibitor history.

CONCLUSIONS

We established reference values for FVIII/IX concentrates according to patient characteristics and concentrate type in a large database of hemophilia patients. These reference values may inform clinical practice (e.g., assessment of immune tolerance success), economic implications of procurement processes and value attribution of novel treatments (e.g., mimetics, gene therapy).

2021 clinical trials update: Innovations in hemophilia therapy

Therapies engineered to prolong clotting factor protein circulation time, manipulate the balance of pro-coagulant and anti-coagulant proteins, or introduce new genetic material to enable endogenous factor protein production dominate the clinical trial landscape of hemophilia. The availability of clotting factor concentrates and the establishment of primary prophylaxis have dramatically improved health outcomes for hemophilia patients. But, the burden of hemostatic therapy remains significant, and many barriers to consistent longitudinal use of prophylaxis exist. Several types of emerging therapeutics including engineered factor concentrates, substitutive therapies, rebalancing therapies, and gene transfer/editing all aim to reduce the challenges of current hemophilia treatment. Emerging treatment options may reduce treatment frequency or need for intravenous administration. They may also introduce new challenges in laboratory assessment of hemostasis. These novel therapies must not introduce significant new health risks and continue to support similar or improved outcomes. The potential ramifications of rebalancing the coagulation cascade, particularly in a stress or inflammatory state, or introduction of new genetic material are not trivial. The focus of this review is to provide an overview of active and recently completed clinical trials as well as emerging preclinical data investigating new therapeutic possibilities for hemophilia patients and potentially other rare bleeding disorders.

Population Pharmacokinetics of Clotting Factor Concentrates and Desmopressin in Hemophilia

Hemophilia A and B are bleeding disorders caused by a deficiency of clotting factor VIII and IX, respectively. Patients with severe hemophilia (< 0.01 IU mL⁻¹) and some patients with moderate hemophilia (0.01–0.05 IU mL⁻¹) administer clotting factor concentrates prophylactically. Desmopressin (d-amino d-arginine vasopressin) can be applied in patients with non-severe hemophilia A. The aim of administration of factor concentrates or desmopressin is the prevention or cessation of bleeding. Despite weight-based dosing, it has been demonstrated that factor concentrates still exhibit considerable pharmacokinetic variability. Population pharmacokinetic analyses, in which this variability is quantified and explained, are increasingly performed in hemophilia research. These analyses can assist in the identification of important patient characteristics and can be applied to perform patient-tailored dosing. This review aims to present and discuss the population pharmacokinetic analyses that have been conducted to develop population pharmacokinetic models describing factor levels after administration of factor VIII or factor IX concentrates or d-amino d-arginine vasopressin. In total, 33 publications were retrieved from the literature. Two approaches were applied to perform population pharmacokinetic analyses, the standard two-stage approach and non-linear mixed-effect modeling. Using the standard two-stage approach, four population pharmacokinetic models were established describing factor VIII levels. In the remaining 29 analyses, the non-linear mixed-effect modeling approach was applied. NONMEM was the preferred software to establish population pharmacokinetic models. In total, 18 population pharmacokinetic analyses were conducted on the basis of data from a single product. From all available population pharmacokinetic analyses, 27 studies also included data from pediatric patients. In the majority of the population pharmacokinetic models, the population pharmacokinetic parameters were allometrically scaled using actual body weight. In this review, the available methods used for constructing the models, key features of these models, patient population characteristics, and established covariate relationships are described in detail.