Pharmacokinetics in routine haemophilia clinical practice: rationale and modalities-a practical review

Recombinant factor IX Fc for the treatment of hemophilia B

Current hemophilia B treatment guidelines recommend routine prophylaxis with factor IX (FIX) replacement products, tailored to maintain plasma activity at levels that will prevent bleeds. However, plasma FIX activity may not be the primary determinant or best indicator of hemostatic efficacy due to its extravascular distribution. FIX replacement therapy has evolved to include extended half-life (EHL) products that provide effective bleed protection when administered at intervals of 7 days or longer. rFIXFc is a recombinant fusion protein with an extended circulation time. rFIXFc has a biodistribution profile consistent with distribution into extravascular space, where it may support hemostasis at sites of vessel injury independent of circulating plasma activity levels. The safety and efficacy of rFIXFc prophylaxis is well established in adults, adolescents and children including previously untreated patients with hemophilia B, with substantial evidence from clinical trials and real-world clinical practice. This review describes the pharmacokinetic characteristics of rFIXFc, summarizes available safety and efficacy data, and evaluates the use of rFIXFc in special populations. Current hemophilia B treatment challenges, including target FIX plasma levels, perioperative use, and management of patients with comorbidities, are discussed together with the potential role of EHL products in the future treatment landscape of hemophilia B.

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.

Biodistribution of recombinant factor IX, extended half-life recombinant factor IX Fc fusion protein, and glycoPEGylated recombinant factor IX in hemophilia B mice

Extended half-life recombinant FIX (rFIX) molecules have been generated to reduce the dosing burden and increase the protection of patients with hemophilia B. Clinical pharmacology studies with recombinant factor IX Fc fusion protein (rFIXFc) report a similar initial peak plasma recovery to that of rFIX, but with a larger volume of distribution. Although the pegylation of N9-GP results in a larger plasma recovery, there is a smaller volume of distribution, suggesting less extravasation of the latter drug. In this study, we set out to compare the biodistribution and tissue localization of rFIX, rFIXFc, and glycoPEGylated rFIX in a hemophilia B mouse model. Radiolabeled rFIX, rFIXFc, and rFIX-GP were employed in in vivo single-photon emission computed tomography imaging (SPECT/CT), microautoradiography (MARG), and histology to assess the distribution of FIX reagents over time. Immediately following injection, vascularized tissues demonstrated intense signal irrespective of FIX reagent. rFIX and rFIXFc were retained in joint and muscle areas through 5 half-lives, unlike rFIX-GP (assessed by SPECT). MARG and immunohistochemistry showed FIX agents localized at blood vessels among tissues, including liver, spleen, and kidney. Microautoradiographs, as well as fluorescent-labeled images of knee joint areas, demonstrated retention over time of FIX signal at the trabecular area of bone. Data indicate that rFIXFc is similar to rFIX in that it distributes outside the plasma compartment and is retained in certain tissues over time, while also retained at higher plasma levels. Overall, data suggest that Fc fusion does not impede the extravascular distribution of FIX.

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.

The Effects of Coronavirus Disease 2019 Pandemic on Patients with Hemophilia and Inherited Bleeding Disorders: Results from 2 Centers in Turkey

OBJECTIVE

Patients with inherited bleeding disorders faced problems in accessing healthcare during coronavirus disease 2019 pandemic. This study aimed to investigate the health problems of patients with inherited bleeding disorders during the coronavirus disease 2019 pandemic.

MATERIAL AND METHODS

Children and adult patients with inherited bleeding disorders who had a coronavirus disease 2019 infection between March 2020 and November 2021 were retrospec- tively evaluated.

RESULTS

Seven hundred seventy-two patients were reviewed, and 65 patients who had a coro- navirus disease 2019 infection (Male/Female: 58/7, mean age 28.2 ±14.1 years) were analyzed. Sixty patients (92%) had hemophilia A or B or von Willebrand's disease and 5 (8%) had rare bleeding disorders. Sixteen (24.6%) patients had a comorbid disease and 6 (9.2%) needed hospitalization due to severe coronavirus disease 2019 infection. Seven patients (10.7%) expe- rienced a bleeding episode and were treated with factor concentrates. Totally, 64 (98.46%) patients recovered from the coronavirus disease 2019 infection and 1 died.

CONCLUSION

Patients with inherited bleeding disorders and coronavirus disease 2019 infection mostly had a mild/moderate course of the disease.

Efficacy and safety in patients with haemophilia A switching to octocog alfa (BAY 81-8973): Final results of the global real-world study, TAURUS

OBJECTIVES

To report the final results of the 2-year TAURUS study, assessing weekly prophylaxis dosing regimens of octocog alfa (Kovaltry®/BAY 81-8973) used in standard clinical practice in patients with moderate-to-severe haemophilia A.

METHODS

TAURUS (NCT02830477) is a phase 4, multinational, prospective, non-interventional, single-arm study in patients of any age with moderate or severe haemophilia A (≤5% factor [F]VIII activity). TAURUS was designed to primarily investigate weekly prophylaxis dosing regimens used in standard clinical practice. Annualised bleeding rates (ABRs), treatment satisfaction and adherence, and safety were also assessed.

RESULTS

Of 302 patients included in the full analysis set, 84.4% (n = 255) maintained their octocog alfa prophylaxis baseline regimen throughout the study, with a majority of patients (76.5%, n = 231) on two times or three times weekly regimens at the end of the observation period (≥1-≤2 years). ABRs, treatment satisfaction, and adherence remained stable during the observation period. Octocog alfa was well tolerated and there were no new or unexpected adverse events.

CONCLUSIONS

These data show that a smooth transition is observed when switching to octocog alfa from a previous FVIII treatment, with no safety issues and stable bleeding rates in a real-world setting of patients with moderate-to-severe haemophilia A.

Area under the curve: Comparing the value of factor VIII replacement therapies in haemophilia A

INTRODUCTION

In factor VIII (FVIII) prophylaxis for haemophilia A, cost comparisons have used price per international unit (IU) based on the once reasonable assumption of equivalent outcome per IU. Now, with several extended half-life (EHL) products available, new outcome-oriented ways to compare products are needed. Area under the curve (AUC) quantifies FVIII levels over time after infusion providing comparable data.

AIM

To develop a decision analytical model for making indirect comparisons of FVIII replacement products based on AUC.

METHODS

A literature search identified 11 crossover studies with relevant pharmacokinetic data. A common comparator FVIII level curve was calculated using pooled data from selected studies. Absolute curves for other products were estimated based on relative differences to the common comparator (% difference vs the anchor). Three scenarios were investigated: (1) Kogenate^® versus Kovaltry^® and Jivi^® ; (2) Advate^® versus Elocta^® , NovoEight^® , Kovaltry, Adynovate^® , Afstyla^® , and ReFacto^® ; and (3) Jivi versus Elocta, Adynovate, and Kogenate. Sensitivity analyses investigated effects of assay type and dose.

RESULTS

In scenario 1, Jivi (+50%) and Kovaltry (+14%) showed larger AUCs versus Kogenate. In scenario 2, EHL products, Elocta and Adynovate, had the largest AUC (+64% and +58%, respectively) versus Advate. Compared with all other products in scenario 3, Jivi had the largest AUC by +13%-28%.

CONCLUSION

This analysis concludes that EHL products differ in relative AUC, have a larger AUC compared with standard half-life, and thus, different FVIII levels over time after infusion. This model may aid decision makers in the absence of head-to-head data.

Individualised prophylaxis based on personalised target trough FVIII level optimised clinical outcomes in paediatric patients with severe haemophilia A

INTRODUCTION

As standard care of severe haemophilia A (SHA), prophylaxis should be individualised.

AIM

This study aimed to investigate the effectiveness of this new-proposed individualised prophylaxis protocol.

METHODS

Boys with SHA were enrolled and followed a PK-guided, trough-level escalating protocol of prophylaxis after a six-month observational period. In the next 2 years, clinical assessments including joint bleeds, ultrasound (US) scores and Haemophilia Joint Health Score (HJHS) in both sides of ankles, knees and elbows were conducted every 6 months as a scoring system, which determined whether the trough level's escalation. Adjustment of dosing regimen was based on WAPPS-Hemo.

RESULTS

Fifty-eight SHA boys were finally analysed. Their age and bodyweight were 5.3(2.8,6.9) years and 21.5(16,25) kg. During the study, 47 escalations were conducted. At study exit, the patient number and proportion of different trough level groups were: < 1 IU/dl, 17.2% (10/58); 1-3 IU/dl, 53.5% (31/58); 3-5 IU/dl, 15.5% (9/58); > 5 IU/dl, 13.8% (8/58). Significantly reduced annualised bleeding rate [4(0,8) to 0(0,2), p < .0001] and annualised joint bleeding rate [2(0,4) to 0(0,.25), p < .0001] was observed at study exit as well as the continuous trend of increased zero bleeding proportion (ZBP) (27.6%-69.0%) and zero joint bleeding proportion (46.5%-81.3%). Besides, 85% (6/7) of the target joints vanished. Statistical improvements of US scores (p = .04) and HJHS (p = .02) were also reported at study exit.

CONCLUSION

Our results showed the effectiveness of our protocol based on individualised target trough level and emphasise the importance of personalised prophylaxis.

The Impact of Pharmacokinetic-Guided Prophylaxis on Clinical Outcomes and Healthcare Resource Utilization in Hemophilia A Patients: Real-World Evidence from the CHESS II Study

Background

Using a pharmacokinetic (PK)-guided approach to personalize the dose and frequency of prophylactic treatment can help achieve and maintain targeted factor VIII (FVIII) trough levels in patients with hemophilia A.

Objective

Investigate clinical and healthcare resource use outcomes in patients with hemophilia A treated with or without PK-guided prophylaxis using data from the Cost of Haemophilia in Europe: A Socioeconomic Survey (CHESS) II database.

Methods

CHESS II was a cross-sectional, retrospective, burden-of-illness study incorporating data from eight European countries. Patients were eligible for this analysis if they were male, ≥18 years of age, and diagnosed with congenital hemophilia A of any severity. The clinical endpoints included annualized bleeding rate (ABR), presence and number of problem/target joints, and occurrence of joint surgeries. Healthcare resource utilization endpoints included the number of hematologist consultations and bleed-related hospitalizations or emergency department admissions. Data from November 2018 to October 2020 were included and were stratified according to treatment regimen and use of PK-guided dosing.

Results

Altogether, 281 patients on prophylaxis had available FVIII trough level data. Mean (SD) age was 35.7 (13.8) years. A specific FVIII trough level was targeted in 120 (42.7%) patients and 47 (39.2%) received PK-guided dosing. Patients receiving PK-guided dosing had a mean (SD) ABR of 2.8 (2.1) and target joint number of 0.5 (0.7), compared with 3.9 (2.7) and 0.9 (1.4), respectively, for patients receiving non-PK-guided treatment. The mean (SD) number of hematologist consultations was 7.1 (5.3) for patients receiving PK-guided dosing versus 10.7 (5.7) for those who were not. A higher proportion of patients in the non-PK-guided group required hospitalization during their lifetime compared with the PK-guided group.

Conclusion

This analysis of real-world data suggests that PK-guided dosing for prophylaxis has a beneficial impact on clinical and healthcare resource utilization outcomes in patients with hemophilia A.

Non‐factor therapies for bleeding disorders: A primer for the general haematologist

Management of patients with severe bleeding disorders, particularly haemophilia A and B, and to a lesser extent, von Willebrand disease, has come on leaps and bounds over the past decade. Until recently, patients relied upon the administration of factor concentrates to prevent or treat bleeding episodes. Factor administration requires intravenous access and, in up to one‐third of patients, leads to the development of neutralising antibodies, or inhibitors, which are associated with more frequent bleeding episodes and higher morbidity. Novel non‐factor therapies may offer a solution to these unmet needs. In this review, we discuss the factor mimetics, particularly emicizumab, and the rebalancing agents, which inhibit antithrombin, tissue factor pathway inhibitor and activated protein C, and novel treatments to enhance von Willebrand factor levels. We review the available trial data, unanswered questions and challenges associated with these new treatment modalities. Finally, we provide practical management algorithms to aid the general haematologist when faced with a patient receiving emicizumab who requires surgery or may develop bleeding.

First experience of a hemophilia monitoring platform: florio HAEMO

Background

florio HAEMO is a new hemophilia treatment monitoring application consisting of a patient smartphone application (app) and a web‐based dashboard for healthcare professionals, providing several novel features, including activity tracking, wearable connectivity, kids and caregiver mode, and real‐time pharmacokinetic factor level estimation.

Objectives

To assess intuitiveness, ease‐of‐use, and patient preference of florio HAEMO in Central Europe using a cross‐sectional survey.

Methods

This survey was conducted in six Central European countries between 9 December 2020 and 24 May 2021. The online questionnaire included 17 questions about overall satisfaction, ease‐of‐use, intuitiveness, and patient preference. Adults or children with hemophilia on regular prophylaxis and using the florio HAEMO app for a minimum of 1 week were invited to complete the online questionnaire by their treating physician.

Results

Sixty‐six participants took part in the survey. The median duration for all respondents using the florio HAEMO app was 3 to 4 weeks. Overall, 89.4% of users reported being very satisfied or rather satisfied after using florio HAEMO. Of the 23 respondents who had switched from another hemophilia app, 87.0% indicated that they strongly preferred or preferred using florio HAEMO. Most florio HAEMO users reported that the app was very easy or rather easy to use (97.0%) and intuitive (94.0%). florio HAEMO had a positive impact on daily living, with 78.8% of users reporting that the app was very important or rather important to them.

Conclusions

This survey suggests that florio HAEMO is an easy‐to‐use and intuitive app to assist self‐management of home prophylaxis.

How do we optimally utilize factor concentrates in persons with hemophilia?

The current mainstay of therapy for hemophilia is to replace the deficient clotting factor with the intravenous administration of exogenous clotting factor concentrates. Prophylaxis factor replacement therapy is now considered the standard of care in both pediatric and adult patients with hemophilia with a severe phenotype to protect musculoskeletal health and improve quality of life. Heterogeneity in bleeding presentation among patients with hemophilia due to genetic, environmental, and treatment-related factors has been well described. Accordingly, the World Federation of Hemophilia recommends an individualized prophylaxis regimen that considers the factors mentioned above to meet the clinical needs of the patient, which can vary over time. This review focuses on the practical points of choosing the type of factor concentrate, dose, and interval while evaluating appropriate target trough factor levels and bleeding triggers such as level of physical activity and joint status. We also discuss the use of a pharmacokinetics assessment and its incorporation in the clinic for a tailored approach toward individualized management. Overall, adopting an individualized prophylaxis regimen leads to an optimal utilization of factor concentrates with maximum efficacy and minimum waste.