Pharmacokinetics, coagulation factor consumption and clinical efficacy in patients being switched from full-length FVIII treatment to B-domain-deleted r-FVIII and back to full-length FVIII

A Real-World Analysis of Commonly Prescribed FVIII Products Based on U.S. Medical Charts: Consumption and Bleeding Outcomes in Hemophilia A Patients

BACKGROUND

Patients with hemophilia A are commonly treated with replacement recombinant factor VIII (rFVIII) products, which can be standard-acting or long-acting. Long-acting products have modifications, offering the potential for reduced dosing frequency while maintaining therapeutic benefit. Extended dosing intervals reduce patient burden and can improve quality of life and adherence.

OBJECTIVE

To assess real-world data for the use of 6 commonly prescribed standard-acting and long-acting FVIII products in the United States: octocog alfa, BAY 14-2222, BAY 81-8973, rVIII-SingleChain, rFVIIIFc, and polyethylene glycol (PEG)-rFVIII. We summarized annualized bleeding rates (ABRs), dosing frequency, and factor consumption in patients treated with each product, with subgroup analyses for patients with severe disease.

METHODS

De-identified patient data were collected from 11 hemophilia treatment centers in the United States. Patients treated with octocog alfa, BAY 14-2222, BAY 81-8973, rVIII-SingleChain, rFVIIIFc, or PEG-rFVIII prophylaxis for ≥ 8 weeks at the time of data collection were included in the analysis. Among the 6 treatment groups, matching was attempted for patient age and disease severity where possible.

RESULTS

Data were obtained for 240 patients, of whom 191 patients had severe disease. Patients receiving long-acting FVIII products were dosed less frequently than those receiving standard-acting FVIII products. The proportion of patients dosed 2 times weekly or less was 65.0%, 70.0%, 72.5%, 25.0%, 40.0%, and 47.5% with rVIII-SingleChain, rFVIIIFc, PEG-rFVIII, octocog alfa, BAY 14-2222, and BAY 81-8973, respectively. Median ABRs ranged from 2.0 to 3.0 (mean 2.6 to 4.4) across the 6 products for all patients and were similar for patients with severe disease (median 2.0 to 3.0 and mean 2.5 to 4.8). The proportion of patients experiencing 0 bleeding episodes ranged from 7.5% to 25.0% for all patients and 12.0% to 28.6% for patients with severe disease. For all patients, median (mean) weekly FVIII product consumption was lowest for rVIII-SingleChain among the 6 products (P = 0.045); 91.9 (91.1) IU per kg per week for rVIII-SingleChain, 108.5 (103.6) for rFVIIIFc, 97.6 (111.0) for PEG-rFVIII, 114.0 (117.5) for octocog alfa, 102.5 (102.6) for BAY 14-2222, and 95.1 (100.7) for BAY 81-8973. Similar differences in weekly consumption among the 6 products were observed for patients with severe disease (P = 0.014).

CONCLUSIONS

Real-world data demonstrate that long-acting products may be beneficial compared with standard-acting products because of reduced dosing frequency while maintaining effectiveness. The 6 products evaluated showed statistically comparable ABRs and percentage of patients with 0 bleeds for all patients including those with severe disease. rVIII-SingleChain demonstrated lowest mean consumption for all patients, as well as for patients with severe hemophilia A, which may lead to potential savings in health care costs.

DISCLOSURES

This study was funded by CSL Behring. Simpson reports consulting honoraria for participation in advisory boards for Bayer, CSL Behring, HEMA Biologics, Novo Nordisk, Octapharma, and Takeda and speakers bureau for Bayer and Novo Nordisk. Yan and Desai are employees of CSL Behring. Maro is an employee of Adivo Associates, which conducted the analyses for this study. Data were presented in part at the Hemostasis and Thrombosis Research Society; May 9-11, 2019; New Orleans, LA; at the International Society on Thrombosis and Haemostasis; July 6-10, 2019; Melbourne, Australia; and have been published in part in "Comparing Factor Use and Bleed Rates in U.S. Hemophilia A Patients Receiving Prophylaxis with 3 Different Long-Acting Recombinant Factor VIII Products," by Mindy L. Simpson, Vidhi Desai, Géraldine S. Maro, Songkai Yan (J Manag Care Spec Pharm. 2020;26[4]:504-12).

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.

Safety of recombinant coagulation factors in treating hemophilia

INTRODUCTION

During the last decade, new FVIII/IX concentrates have been developed for the treatment of patients affected by hemophilia A/B. Significant progress has been achieved regarding their half-life, but the old issue of immunogenicity and new concerns about safety need to be addressed.

AREAS COVERED

After the implementation of virucidal methods, both plasma-derived and recombinant clotting factor concentrates achieved a very safe profile. The development of anti-FVIII antibodies is the major adverse event of replacement therapy with both FVIII concentrates. Furthermore, the new extended half-life concentrates, protein fused or pegylated, raised some concerns about their side effects.

EXPERT OPINION

The treatment of hemophilia A with inhibitors by induction of immunotolerance and using by-passing concentrates, improved the quality of life of patients but did not allow them to have a life expectancy like that of patients without inhibitors. The new humanized monoclonal antibody (MAb) ACE910, mimicking FVIII function, seems to be able to reduce the bleedings of hemophilia A patients with inhibitors. The post-marketing surveillance will clarify if the adverse events observed during the phase III clinical trials and compassionate use were due to the association with a Prothrombin activated complex concentrate or to the prothrombotic effect of the drug itself.

Using pharmacokinetics to individualize hemophilia therapy

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

Major and Minor Classifications for Surgery in People With Hemophilia: A Literature Review

Agents that control bleeding and the usage of bypassing agents have made surgery an option to consider in people with hemophilia. However, the lack of consistent definitions for major or minor surgery may lead to inconsistencies in patient management. This literature review has evaluated how surgical procedures in people with hemophilia were categorized as major or minor surgery and assessed the consistency across publications. After screening 926 potentially relevant articles, 547 were excluded and 379 full-text articles were reviewed. Ninety-five articles categorized major or minor surgical procedures; of these, 35 publications categorized three or more major or minor surgical procedures and were included for analysis. Seven (20%) publications provided varying criteria for defining major or minor surgery, five of which defined surgery according to the level of surgical invasiveness. Across all 35 publications, there was considerable variance in the categorization of major and minor surgical procedures and some overlap in surgical nomenclature (eg, type of synovectomy, arthroscopy, and central venous access device insertion/removals). The lack of consistent guidance when referring to major or minor surgery in people with hemophilia needs to be addressed. Clear and consistent definitions, achieved by consensus and promoted by relevant international hemophilia committees, are desirable, to provide guidance on appropriate treatment, to increase the accuracy of trial data and may confound the interpretation of surgical outcomes.

Assessment of relative bioavailability of two presentations of moroctocog alfa (AF-CC) in subjects with moderately severe or severe hemophilia A

An open-label, single-dose, randomized, two-period, cross-over study comparing the pharmacokinetics of factor VIII activity in plasma (

FVIII

C) after administration of a new presentation of moroctocog alfa containing 3,000 IU in a dual-chamber syringe and the combined contents of approved 1,000 and 2,000 IU vials was conducted in 16 male subjects who had moderately severe or severe hemophilia A (FVIII:C ≤2 IU/dL). Blood samples were collected for 72 hours after administration of the dose.

FVIII

C were assayed using a chromogenic substrate assay in a central laboratory. The

FVIII

C pharmacokinetic parameters were calculated using noncompartmental analysis. The dual-chamber syringe would be bioequivalent to the combined contents of the vials if the 90% confidence limits of the ratio of the geometric mean values of AUCinf , and Cmax fell within the interval of 80-125%. The bioequivalence criteria were met. A total of seven treatment related adverse events were observed in a total of five subjects. All were mild and none was determined to be related to administration of study medication.

Switching clotting factor concentrates: considerations in estimating the risk of immunogenicity

The development of neutralizing antibodies to factor VIII (FVIII) is the most serious complication of therapy for haemophilia A. There is now excellent documentation that a large number of both genetic and environmental factors contribute to the risk of FVIII inhibitor incidence. One of the environmental factors that has been proposed as an influence on this complication is the occurrence of FVIII product switching. There are only a small number of clinical studies that have addressed this question, and thus, the amount of objective information available to assess this association is limited. In this review, in addition to summarizing past evidence pertinent to this subject, we present the results of a complementary strategy, a Delphi analysis, to add to the considerations of product switching and FVIII immunogenicity. With the imminent arrival in the clinic of several new FVIII products, the haemophilia community must be prepared to collect prospectively controlled data to better address this important management issue.

Clotting factor concentrate switching and inhibitor development in hemophilia A

The development of alloantibodies or inhibitors is the most serious complication a patient with severe hemophilia can experience from treatment with clotting factor concentrates. Although common in previously untreated patients, inhibitor development is rare in multiply exposed, well-tolerized patients. There has been a nonevidence-based reluctance to change concentrate because of a perceived greater inhibitor risk after the switch, even though most patients are now likely to be using a concentrate on which they did not begin. Inhibitors in previously treated patients are observed in approximately 2 per 1000 patient/years, which makes it difficult to study and compare rates among different products. Because the baseline inhibitor risk in previously treated patients may vary over time, it is important to compare the risk in patients switching to a new product with that in a parallel control group of nonswitching patients or within a case-controlled study. The study designs imposed by regulators are suboptimal in detecting immunogenicity signals. The issue of immunogenicity of new products is likely to gain more relevance in the near future, with a call for effective postmarketing surveillance studies for all of the new engineered factor VIII concentrates with prolonged half-lives that are likely to enter clinical practice.

Can B-domain deletion alter the immunogenicity of recombinant factor VIII? A meta-analysis of prospective clinical studies

BACKGROUND

As a result of the infrequency of inhibitors in previously treated patients (PTPs) with hemophilia A and the small size of available clinical studies, the immunogenicity of factor (F)VIII products has been difficult to assess.

OBJECTIVES

A meta-analysis of prospective clinical studies was conducted to test the hypothesis that de novo inhibitor incidence differs between PTPs receiving full-length recombinant FVIII (FL-rFVIII) and B-domain deleted recombinant FVIII (BDD-rFVIII).

METHODS

Prospective studies with data on inhibitors in PTPs receiving FL-rFVIII or BDD-rFVIII were sought using systematic methods including bibliographic database searches. Data were secured from published study reports and inquiries to investigators. Between-group differences in inhibitor incidence rates were evaluated using mixed effects Cox regression.

RESULTS

Twenty-nine studies with 3012 total PTPs were included. Patients were at risk of de novo inhibitor development for a median of 79 exposure days. A total of 35 de novo inhibitors were observed. The cumulative hazard for all de novo inhibitors was 1.25% with a 95% confidence interval (CI) of 0.63-1.88%. The corresponding rate for high-titer de novo inhibitors [> 5 Bethesda units (BU)] was 0.29% (CI, 0.01-0.57%). Exposure to BDD-rFVIII was associated with an increased risk of all de novo inhibitors (hazard ratio, 7.26; CI, 2.12-24.9; P = 0.0016) and of high-titer de novo inhibitors (hazard ratio, 10.8; CI, 2.17-53.7; P = 0.0037), compared with FL-rFVIII.

CONCLUSIONS

This meta-analysis of prospective clinical studies suggests that recombinant FVIII products may differ in immunogenicity.