Using pharmacokinetics for tailoring prophylaxis in people with hemophilia switching between clotting factor products: A scoping review

Debates Surrounding the Use of Antithrombotic Therapy in Hemophilic Patients with Cardiovascular Disease: Best Strategies to Minimize Severe Bleeding Risk

Navigating through antithrombotic therapy in patients with both hemophilia and cardiovascular pathology presents a complex scenario with inherent challenges and opportunities. The presence of hemophilia, characterized by impaired blood clotting, adds a layer of complexity to the management of cardiovascular conditions requiring antiplatelet therapy and anticoagulation. Striking a delicate balance between the necessity for antithrombotic treatment to prevent cardiovascular events and the heightened risk of severe bleeding in individuals with hemophilia demands a nuanced and carefully considered approach. The challenges revolve around identifying an optimal therapeutic strategy that effectively mitigates cardiovascular risks without exacerbating bleeding tendencies. In hemophilic patients with cardiovascular disease, the decision to use antiplatelet therapy requires careful consideration of the individual's bleeding risk profile, considering factors such as the severity of hemophilia, history of bleeding episodes, and concurrent medications. The goal is to provide effective antithrombotic treatment while minimizing the potential for excessive bleeding complications. Conventional anticoagulants like warfarin pose difficulties due to their potential to increase the risk of bleeding. On the other hand, emerging options like novel direct oral anticoagulants (DOACs) present an opportunity, offering predictable pharmacokinetics and user-friendly administration. However, a comprehensive exploration of their safety and efficacy in hemophilic patients is imperative. Achieving the right equilibrium between preventing cardiovascular events and minimizing bleeding risk is pivotal in selecting the most effective therapeutic option for individuals with hemophilia and cardiovascular pathology. A multidisciplinary approach, integrating the expertise of hematologists and cardiologists, becomes essential to customize treatments and address the intricacies of this medical challenge.

Development of a Coagulation Disorders Unit

Our Coagulation Disorders Unit in Helsinki, Finland, provides 24/7 services for local and national hospitals and colleagues upon requests regarding bleeding and thrombosis diagnostics and management, including follow-up. The unit has a tight connection between the clinic and laboratory, and its maintenance and sharing knowledge and observations have been priorities, already for over 20 years and will continue to be of major importance. The consultation service is provided by phone during daytime and on-call hours, and in written form sent electronically to the consulting stakeholders. Thrombosis and hemostasis-targeted outpatient clinics are also available for the patients referred to the center. Writing local guidance and official guidelines, Nordic, European and international collaboration, and educational activities including social communication are critical elements for the Coagulation Disorders Unit. Alertness to acute coagulation abnormalities, such as occurred during COVID-19 and vaccine-induced thrombosis and thrombocytopenia, and development of strategies to manage cross-disciplinary problems are topics which call upon broad networking. The Nordic community has an ongoing historical meeting, which has been circulating among coagulation centers for the past 56 years. At the European level, the European Association of Haemophilia and Allied Disorders focuses on bleeding disorders and their management, including safety surveillance. The International Society of Thrombosis and Haemostasis offers excellent basic and clinical benchmarks for any Coagulation Disorders Unit. We hope that the description of the development and implementation of our Coagulation Disorders Unit in Helsinki achieves international interest and broadens international collaboration. Finally, we congratulate STH on its great contributions around the globe and for providing a vivid forum to foster the discipline of thrombosis and hemostasis.

Pharmacokinetic-Pharmacodynamic Modelling in Hemophilia A: Relating Thrombin and Plasmin Generation to Factor VIII Activity After Administration of a VWF/FVIII Concentrate

BACKGROUND

Hemophilia A patients are treated with factor (F) VIII prophylactically to prevent bleeding. In general, dosage and frequency are based on pharmacokinetic measurements. Ideally, an alternative dose adjustment can be based on the hemostatic potential, measured with a thrombin generation assay (TGA), like the Nijmegen hemostasis assay.

OBJECTIVE

The objective of this study was to investigate the predicted performance of a previously developed pharmacokinetic-pharmacodynamic model for FVIII replacement therapy, relating FVIII dose and FVIII activity levels with thrombin and plasmin generation parameters.

METHODS

Pharmacokinetic and pharmacodynamic measurements were obtained from 29 severe hemophilia A patients treated with pdVWF/FVIII concentrate (Haemate P®). The predictive performance of the previously developed pharmacokinetic-pharmacodynamic model was evaluated using nonlinear mixed-effects modeling (NONMEM). When predictions of FVIII activity or TGA parameters were inadequate [median prediction error (MPE) > 20%], a new model was developed.

RESULTS

The original pharmacokinetic model underestimated clearance and was refined based on a two-compartment model. The pharmacodynamic model displays no bias in the observed normalized thrombin peak height and normalized thrombin potential (MPE of 6.83% and 7.46%). After re-estimating pharmacodynamic parameters, EC50 and Emax values were relatively comparable between the original model and this group. Prediction of normalized plasmin peak height was inaccurate (MPE 58.9%).

CONCLUSION

Our predictive performance displayed adequate thrombin pharmacodynamic predictions of the original model, but a new pharmacokinetic model was required. The pharmacodynamic model is not factor specific and applicable to multiple factor concentrates. A prospective study is needed to validate the impact of the FVIII dosing pharmacodynamic model on bleeding reduction in patients.

Effects of PK-guided prophylaxis on clinical outcomes and FVIII consumption for patients with moderate to severe Haemophilia A

INTRODUCTION

In recent years, there has been increased focus on individualizing treatment for persons with hemophilia including pharmacokinetic-guided (PK) dosing.

AIMS

In this retrospective study clinical outcomes before and after PK-guided prophylaxis were examined.

MATERIALS AND METHODS

Eight Haemophilia Treatment Centres from the United States participated in the study and included 132 patients classified into two cohorts: those undergoing a PK-assessment for product switch (switchers) or to optimize treatment (non-switchers). Subset analyses for the two most common products and patients with dosing per prescription label were included for annual bleeding rates (ABR), mean weekly consumption outcomes, and annualized cost of prophylaxis.

RESULTS

The most common products before and after index date were octocog alfa, rurioctocog alfa pegol, and efmoroctocog alfa. Seventy-four (56%) patients were identified as switchers and 58 (44%) patients were classified as non-switchers. The majority of patients (78.0%) experienced either a decrease in ABR post-index or maintained 0 ABR during pre- and post-index time periods, with similar proportions identified in both switchers (77.0%) and non-switchers (79.3%) populations. Non-switchers were identified as having no significant change in cost of therapy, while switchers experienced increased cost of therapy driven by higher price of extended half-life products. Within subset analyses, patients receiving rurioctocog alfa pegol and efmoroctocog alfa had mean ABR under 1 after index date.

CONCLUSION

PK-guided prophylaxis has the potential to improve clinical outcomes without increase in cost of therapy for patients maintaining product and can aid in maintaining effective protection against bleeds in those switching product.

Anticoagulation and antiplatelet therapy in hereditary hemorrhagic telangiectasia: A scoping review

INTRODUCTION

Data describing safety and tolerability of anticoagulation and antiplatelet therapy in hereditary hemorrhagic telangiectasia (HHT), the second-most-common inherited bleeding disorder, is limited.

METHODS

We performed a scoping review, searching MEDLINE and EMBASE from inception to March 2023 for eligible studies reporting detailed clinical data describing antithrombotic use in HHT. Data extracted included study design, patient population, and characteristics and outcomes of antithrombotic therapy.

RESULTS

Of 625 unique manuscripts identified through database search, 77 were included: 64 case reports/case series describing 65 patients and 13 cohort studies. Data were extracted on a total of 466 patients with HHT, covering 587 episodes of antithrombotic therapy. The most common reasons for antithrombotic therapy were venous thromboembolism (VTE) (44.6 %), atrial arrhythmias (17.8 %) and stroke (10.5 %). anticoagulation was used in in 356 episodes (61.9 %), antiplatelet therapy in 140 episodes (24.3 %), and both together in 50 episodes (8.7 %). Complications of therapy included worsened HHT-associated bleeding (primarily epistaxis and gastrointestinal bleeding) in 198 antithrombotic treatment episodes (38.9 %) and premature antithrombotic therapy discontinuation in 142 episodes (28.9 %). Bleeding-directed therapy (local ablative therapy and systemic therapies) were employed to address worsening bleeding in 14.6 % of episodes. No specific complications of therapy were reported in 322 total antithrombotic events (58.4 %). Rates of bleeding (8.3 % to 80 %), therapy discontinuation (14.3 % to 57.1 %), and other complications ranged considerably from study to study.

CONCLUSION

Current publications vary widely on the outcomes and tolerability of antithrombotics in HHT, but confirm the clinical challenge of adequate antithrombotic therapy in this population. More formal studies are needed to better guide optimal antithrombotic use in HHT.

Limited sampling strategies for individualized BAX 855 prophylaxis in severe hemophilia A: in silico evaluation

OBJECTIVE

Limited sampling strategies (LSS) lower the burden of pharmacokinetic (PK)-guided dosing, but an extensive evaluation of LSS for BAX 855 (Adynovi) is currently lacking. This study aimed to develop a LSS for BAX 855 and combine this with a LSS of a standard half-life (SHL) factor VIII (FVIII) concentrate in a clinical setting.

METHODS

Individual PK parameters of BAX 855 were estimated for 10 000 virtual patients with severe hemophilia A using Monte Carlo simulations. Several LSS consisting of 2-6 samples were examined based on patient burden, bias and accuracy of clearance, elimination half-life, volume of distribution and trough levels at 72 h (C72). Analyses were performed separately for adults and children <12 years.

RESULTS

The preferred LSS for BAX 855 consisted of three sampling points at 15-30 min, 48 h and 72 h for both adults (mean accuracy C72: 14.0% vs. 10.8% using six samples) and children (mean accuracy C72: 14.9% vs. 11.4% using six samples). The best strategy with two samples (peak, 48 h) resulted in an adequate, but lower accuracy than strategies with ≥3 samples (mean accuracy C72: 22.3%). The optimal combination of the LSS of SHL FVIII and BAX 855 led to six samples during four clinical visits.

CONCLUSION

This in silico study has identified that two to three samples are necessary to estimate the individual PK of BAX-855 adequately. These samples can be collected in one or two clinical visits. When combining PK profiling of SHL FVIII and BAX 855, six samples during four clinical visits are needed.

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.

Vascular abnormalities in patients with von Willebrand disease: A scoping review

BACKGROUND

Qualitative or quantitative defects of von Willebrand factor (VWF) such as in von Willebrand disease (VWD) are associated with vascular abnormalities, especially in the gastrointestinal (GI) tract. However, the locations, extent, and natural history of vascular abnormalities in patients with VWD is not well understood. To summarize the existing literature on the topic, we conducted a scoping review of vascular abnormalities in patients with VWD.

METHODS

We searched MEDLINE and EMBASE from inception to September 1, 2020, for studies clinically describing vascular abnormalities in VWD patients. Screening and data extraction was completed independently and in duplicate and each abnormality was documented individually.

RESULTS

After screening, 54 studies that reported patient level data comprising 146 patients were included. Type 2A (39%) and type 3 (14.4%) were the most common VWD subtypes. The most common site of vascular malformation was the GI tract, occurring in 124 patients (84.9%), whereas 18 (12.3%) had non-GI vascular abnormalities and 4 (2.7%) had both GI and non-GI vascular abnormalities. With respect to outcomes, the clinical course was not specified in the majority (55.5%) of patients. Survey and population level data were reported in nine studies, demonstrating vascular abnormalities occurred at higher rates in VWD and that VWD patients are overrepresented among those with those abnormalities.

CONCLUSION

Vascular malformations in patients with VWD occur primarily in the gastrointestinal tract. Type 2A and type 3 VWD are the most common subtypes affected. The clinical treatment and natural history of these abnormalities remains understudied and further research is needed.

Long-Term Antithrombotic Treatments Prescribed for Cardiovascular Diseases in Patients with Hemophilia: Results from the French Registry

Cardiovascular diseases (CVDs) are a major issue in aging patients with hemophilia (PWHs). Antithrombotic agents are widely used in the general population for CVD treatment, but this recommendation is not fully applicable to PWHs. To improve treatment strategies, a prospective case-control study (COCHE) that analyzed CVD management and follow-up (2 years/patient) in PWHs was performed in France from 2011 to 2018. In total, 68 PWHs (median age: 65 years [39-89]; 48 mild, 10 moderate, and 10 severe hemophilia) were included (n = 50 with acute coronary syndrome, n = 17 with atrial fibrillation, n = 1 with both). They were matched with 68 control PWHs without antithrombotic treatment. In our series, bleeding was significantly influenced by (1) hemophilia severity, with a mean annualized bleeding ratio significantly higher in COCHE patients than in controls with basal clotting factor level up to 20%, (2) antihemorrhagic regimen (on-demand vs. prophylaxis) in severe (hazard ratio [HR] = 16.69 [95% confidence interval, CI: 8.2-47.26]; p < 0.0001) and moderate hemophilia (HR = 42.43 [95% CI: 1.86-966.1]; p = 0.0028), (3) type of antithrombotic treatment in mild hemophilia, with a significantly higher risk of bleeding in COCHE patients than in controls for dual-pathway therapy (HR = 15.64 [95% CI: 1.57-115.8]; p = 0.019), anticoagulant drugs alone (HR = 9.91 [95% CI: 1.34-73.47]; p = 0.0248), dual antiplatelet therapy (HR = 5.31 [95% CI: 1.23-22.92]; p = 0.0252), and single antiplatelet therapy (HR = 3.76 [95% CI: 1.13-12.55]; p = 0.0313); and (4) HAS-BLED score ≥3 (odds ratio [OR] = 33 [95% CI: 1.43-761.2]; p = 0.0065). Gastrointestinal bleeding was also significantly higher in COCHE patients than in controls (OR = 15 [95% CI: 1.84-268]; p = 0.0141). The COCHE study confirmed that antithrombotic treatments in PWHs are associated with increased bleeding rates in function of hemophilia-specific factors and also of known factors in the general population.

Acquired von Willebrand syndrome in monoclonal gammopathy - A scoping review on hemostatic management

BACKGROUND

Acquired von Willebrand syndrome (AVWS) has been associated with monoclonal gammopathy of undetermined significance (MGUS), with limited data on its management.

METHODS

We conducted a systematic literature search in Medline (Ovid), Embase, and Scopus up to September 11, 2019, for studies reporting on the management of AVWS associated with MGUS (AVWS-MGUS). Data on patient characteristics, laboratory parameters at presentation, and clinical and laboratory outcomes were extracted.

OBJECTIVES

To describe the clinical presentation and outcomes of different therapeutic approaches.

RESULTS

Seventy-five studies were included in the final review, for a total of 137 patients. Most patients had von Willebrand factor ristocetin cofactor activity <30 IU/dL (86.6%) and factor VIII levels <50 IU/dL (91.8%). Bleeding severity ranged from no bleeding (16.1%) to minor bleeding (46.4%) and major bleeding (37.5%). The overall clinical success rates for 1-deamino-8-D-arginine vasopressin (DDAVP), factor replacement therapy, and intravenous immunoglobulin (IVIG) were 43.8%, 33.3%, and 85.4%, respectively. The laboratory response rates for DDAVP, factor replacement therapy, and IVIG were 39.0%, 62.9%, and 88.6%, respectively. Several other treatments were also reported in small numbers, out of which myeloma-directed therapies, plasma exchange, recombinant factor VIIa, and antifibrinolytics appeared most successful, while immunosuppressive agents were largely ineffective.

CONCLUSION

IVIG appears to be an effective treatment for AVWS-MGUS bleeding, conferring a high clinical success rate with measurable laboratory outcomes; albeit temporary. DDAVP and factor replacement therapy may be partially successful in controlling minor bleeds, but not major bleeds. Other less commonly used agents may be effective in certain cases, although data are limited.

Extended half-life factor VIII concentrates in adults with hemophilia A: Comparative pharmacokinetics of two products

BACKGROUND

The use of pharmacokinetic (PK) studies to help design personalized prophylaxis regimens for factor VIII (FVIII) concentrate in individuals with hemophilia A has been recognized for many years but only became practical for routine clinical use with the availability of web-accessible population PK applications based on Bayesian analysis.

OBJECTIVE

To compare PK variables using population PK studies done on 2 extended half-life recombinant FVIII concentrates in 23 individuals with hemophilia A after switching from one product to the other.

METHODS

We retrospectively analyzed PK parameters derived from the Web-Accessible Population Pharmacokinetic Service-Hemophilia (WAPPS-HEMO) application on 23 individuals with severe or moderately severe hemophilia A who were required to switch from recombinant FVIII Fc (Eloctate; Biogen, Cambridge, MA, USA) to recombinant antihemophilic factor PEGylated (Adynovate; Takeda Pharmaceutical Company, Osaka, Japan) between 2016 and 2017.

RESULTS

There were minor PK differences between Eloctate and Adynovate, but some parameters did reach statistical significance, namely in vivo recovery (mean, 2.73 IU/dL per IU/kg vs 2.41 IU/dL per IU/kg), clearance (mean, 0.163 mL/h vs 0.194 mL/h), and volume of distribution at steady state (mean, 42.5 ml/kg vs 49.8 mL/kg). Smaller nonsignificant trends toward higher values for Adynovate were seen in terminal half-life, area under the curve, and predicted times to 5% and 1% residual FVIII after infusion.

CONCLUSION

Population PK analysis revealed differences between the two extended half-life FVIII concentrates, reaching significance for in vivo recovery, clearance, and volume of distribution.

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.

A comparison of methods for prediction of pharmacokinetics when switching to extended half-life products in hemophilia A patients

INTRODUCTION

Hemophilia A is a genetic bleeding disorder resulting from a lack of clotting factor VIII. Where extended half-life products are available, people with hemophilia may stop their current drug regimen and switch to a EHL product providing a more convenient dosing regimen. While most factor VIII concentrate regimens are started prophylactically based on international units per weight, this "one-size-fits-all" approach does not account for the large pharmacokinetic variability between individuals.

AIMS

We explored methods to predict individual PK of an EHL product by using population pharmacokinetic models and eta-values (η), a value that quantifies how individuals deviate from a population for any PK parameter, derived from a prior product. In addition, we wanted to investigate which individuals would benefit from this method compared to using a PopPK model alone.

METHODS

PK data from subjects (n = 39) who have taken both Adynovate and Eloctate was collected from clinical trial data and from the Web-Accessible Population Pharmacokinetic Service - Hemophilia (WAPPS-Hemo) database. In addition, PK data from subjects (n = 200) who switched from a standard half-life product to Eloctate was also extracted from the WAPPS-Hemo database. Two methods to estimate individual PK outcomes of the second product were compared. The PopPK method used the Eloctate PopPK model published from WAPPS-Hemo, while the η-method incorporated individually scaled η from the prior product's PopPK model. Both methods were assessed for its performance in predicting PK outcomes. Absolute percent differences were calculated between the predicted and observed PK outcomes. Infusions were parsed into subgroups based on number of samples and individual η-percentiles for analysis.

RESULTS

For the three switching protocols (Adynovate to Eloctate, Eloctate to Adynovate, and SHL FVIII to Eloctate), the η-method resulted in a relative difference reduction in mean absolute percent difference of 27.8% (range 1-59%), 4.9% (range 0-129%), and 18.0% (0-79%) in half-life compared to the PopPK method respectively. With some exceptions (in particular central volume), the η-method produced relative difference reduction in mean absolute percent differences up to 33% lower compared to the PopPK method. When individuals were parsed based on their η-values (either CL or V1), the two methods differentiate up to 64% in terms of half-life and time to 0.02 IU/mL predictions for individuals with a low (0th to 20th percentile) η_CL or η_V1 on the first product. Individuals with higher number of observations per infusion on the first product resulted in better predictions in PK parameter estimates when using the η-method.

CONCLUSION

The use of prior knowledge by implementing η-values into PopPK models may provide clinicians with a safer and more effective method to choose a dosing regimen for patients with hemophilia A switching from one factor concentrate to another. However, the η-method was unable to better predict an increase or decrease in half-life of a future product compared to the PopPK method, and thus supports the conclusion that most individuals would still benefit from a trial on the EHL and subsequent estimation of their individual PK profile from sparse measurements on the EHL.

Comparing Factor Use and Bleed Rates in U.S. Hemophilia A Patients Receiving Prophylaxis with 3 Different Long-Acting Recombinant Factor VIII Products

BACKGROUND

Recombinant factor VIII (rFVIII) products have been developed with improved pharmacokinetics, offering some patients the potential to extend dosing intervals, thereby reducing their dosing frequency while minimizing the occurrence of bleeding events. No clinical trials have been conducted to compare the bleeding rates and use of these long-acting products.

OBJECTIVES

To (a) assess real-world use of prophylaxis regimens in patients using 1 of 3 different long-acting products-rVIII-SingleChain, rFVIIIFc, or PEG-rFVIII; and (b) compare bleeding rates, dosing frequency, and factor consumption in 3 cohorts of patients. For rVIII-SingleChain patients, these measures were also compared with the prior products these patients used.

METHODS

De-identified patient chart data were collected from 11 hemophilia treatment centers in the United States. Patients were included if they had been treated with rVIII-SingleChain, rFVIIIFc, or PEG-rFVIII prophylaxis for ≥ 8 weeks at the time of data collection. Matching for age and disease severity was attempted between the 3 patient groups. Data were also collected for patients who switched from their prior FVIII product to prophylaxis with rVIII-SingleChain.

RESULTS

Data were obtained for 120 male patients. The majority of patients were dosing 2 times per week or less frequently (rVIII-SingleChain 65.0%, rFVIIIFc 70.0%, and PEG-rFVIII 72.5%). Annualized bleeding rates were comparable among the 3 cohorts, with median (mean) values of 2.0 (2.6) with rVIII-SingleChain and rFVIIIFc, and 3.0 (3.7) with PEG-rFVIII. The overall median (mean) FVIII consumption in IU per kg per week (IU/kg/week) was 91.9 (91.1) with rVIII-SingleChain, 108.5 (103.6) with rFVIIIFc, and 97.6 (111.0) with PEG-rFVIII, resulting in expected mean annual consumption of 322,140 IU, 361,816 IU, and 373,100 IU, respectively, for a 70 kg patient aged ≥12 years. The mean consumption was significantly different among the 3 products for all patients (P = 0.0164) and for those dosed 2 times per week (P < 0.0001). Among patients infusing 2 times per week, median (mean) consumption with rVIII-SingleChain was 83.8 (81.2) IU/kg/week, compared with 109.6 (104.4) IU/kg/week for rFVIIIFc and 92.1 (91.5) IU/kg/week for PEG-rFVIII. Additionally, switching from prophylaxis with prior FVIII products to rVIII-SingleChain increased the proportion of patients dosing ≤ 2 times per week (20% to 65%), decreased mean consumption (103.3 to 91.9 IU/kg/week; P = 0.0164), and maintained the mean annualized bleeding rates (2.9 to 2.6; P = 0.5665).

CONCLUSIONS

Results for rVIII-SingleChain confirm the findings from its pivotal trial. Analyses of annualized bleeding rates demonstrate comparable clinical outcomes of rVIII-SingleChain to the other 2 long-acting products assessed. In patients aged ≥ 12 years, rVIII-SingleChain prophylaxis may result in an 11.0% and 13.7% lower mean factor consumption than rFVIIIFc and PEG-rFVIII, respectively, representing a potential cost-saving opportunity of 34% in both cases-at the current wholesale acquisition cost of the corresponding products. In addition, in patients using rVIII-SingleChain prophylactically, consumption was reduced compared with their prior products, while bleeding control was well maintained.

DISCLOSURES

This study was funded by CSL Behring. Analyses were conducted by Adivo Associates. Maro is an employee of Adivo Associates. Desai and Yan are employees of CSL Behring. Simpson has received consulting honoraria for participation in advisory boards for CSL Behring, Genentech, Octapharma, and Bioverativ and speakers bureau for Bayer and Novo Nordisk. Data were presented in part at the Hemostasis and Thrombosis Research Society; May 9-11, 2019; New Orleans, LA, and at the International Society on Thrombosis and Haemostasis; July 6-10, 2019; Melbourne, Australia.

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.

Optimising prophylaxis outcomes and costs in haemophilia patients switching to recombinant FVIII-Fc: a single-centre real-world experience

BACKGROUND

The recombinant factor VIII (rFVIII)-IgG1 Fc fusion protein (rFVIII-Fc) was the first available extended half-life rFVIII, shown to prolong dosing intervals of individualised prophylaxis in patients with severe haemophilia A, maintaining low bleeding rates and unchanged or lower FVIII dose versus standard half-life (SHL) rFVIII. Few data are available about real-world experience with rFVIII-Fc, including criteria for patient switching from SHL products, follow up and prophylaxis optimisation.

MATERIALS AND METHODS

A single-centre retrospective study was designed to review patients switched to rFVIII-Fc, based on individual needs, after pharmacokinetic (PK) assessment, according to routine clinical practice. In patients with adequate post-switch follow up, data about rFVIII-Fc prophylaxis were compared with those from the last 18-months SHL rFVIII prophylaxis.

RESULTS

Of 25 candidates, 18 patients (15 severe, 3 moderate; aged 9-62 years; 3 with inhibitor history) started rFVIII-Fc regimens, with comparable FVIII weekly dose and reduced infusion frequency (mean -30%) in all 17 patients previously on SHL rFVIII prophylaxis thrice weekly or every other day. Over a mean 18-month follow up in 13 patients, compared with SHL products, further reduced infusion frequency (mean -40%; p<0.001; interval ≥4 days in 9 patients), improved treatment satisfaction (Hemo-sat questionnaires), significantly lower FVIII weekly dose and annual consumption (mean -12%; p=0.019), comparable bleeding rates and FVIII trough levels, and improved management of breakthrough bleeding were observed. von Willebrand Factor Antigen (VWF:Ag) correlated to PK variables and both had relationships with rFVIII-Fc weekly dose, increasing statistical significance over the follow-up period. No inhibitors or drug-related adverse events were recorded.

DISCUSSION

In this real-world series of patients, a switch to rFVIII-Fc, based on careful assessment of clinical needs, PK testing and treatment monitoring, was able to optimise individual convenience, efficacy and costs of prophylaxis.

Using pharmacokinetics for tailoring prophylaxis in people with hemophilia switching between clotting factor products: A scoping review

The objective of this scoping review is to summarize the current use of pharmacokinetics for tailoring prophylaxis in hemophilia patients switching between clotting factor products. Patients with hemophilia may require switching of clotting factor concentrates due to a variety of factors, but there have been perceived risks associated with switching, such as inhibitor development or suboptimal protection due to inadequate dosing while titrating treatment. Studies that look at patients switching from one clotting factor concentrate to another are categorized in terms of their primary and/or secondary objectives, notably biosimilarity and comparative pharmacokinetic studies and inhibitor development studies. Research on how best to switch concentrates with respect to dosing regimen are lacking, and currently a trial‐and‐error approach is used for dosing the new factor concentrate. In the future, studies looking at the predictability of pharmacokinetics (PK) of a new factor concentrate based on individual PK knowledge of the original factor concentrate may offer clinical benefit by providing a safer switching approach and protocol.