Outcomes in children with hemophilia A with inhibitors: Results from a noninterventional study

Pediatric Rare Diseases Development in the Pharmaceutical Industry: An International Consortium for Innovation and Quality in Pharmaceutical Development, Clinical Pharmacology Leadership Group-Pediatrics Working Group, Rare Diseases Subteam Whitepaper Examining the Current Landscape and Recommendations for the Future

Many new opportunities surround rare pediatric disease drug development, thanks to key advances in regulatory thinking and in the scientific community. As rare disease drug development brings challenges to the developers in terms of limited understanding of natural history, heterogeneity in drug response, as well as difficulty recruiting patients in pivotal trials, there has never been a greater need for quantitative integration. To understand how International Consortium for Innovation and Quality in Pharmaceutical Development (IQ) member companies approach pediatric rare disease drug development, the rare pediatric subteam of the Clinical Pharmacology Leadership Group (CPLG) sponsored Pediatrics Working Group conducted a baseline survey to assess the four main pillars of this quantitative innovation, namely, biomarkers and surrogate end points, statistical methodologies, model-informed drug development, as well as public-private partnerships. The survey was administered by IQ and yielded 13 evaluable responders from represented companies. This article presents the key findings from this baseline identifying survey, highlighting the key blind spots, and providing insightful expert opinions to address those gaps. In summary, we call an urgent attention to the community on the opportunities to enhance integration and within-industry learnings from this analysis on aspects related to platform studies, end-to-end quantitative integration, and sharing of trial-level placebo data for better understanding of disease progression and more efficient trial designs. We collectively hope that these findings will stimulate discussion and debate around cross-industry sharing and collaboration to better delineate principles and further enhance the efficiency of rare pediatric disease drug development.

Knowledge gaps in health-related quality of life research performed in children with bleeding disorders - A scoping review

INTRODUCTION

Bleeding disorders (BDs) may influence health-related quality of life (HRQoL) in children and caregivers. Measuring HRQoL gives insight into domains requiring support and provides an opportunity to evaluate the effects of novel therapies.

AIM

To gain insight in the current body of literature on HRQoL in children with BDs in order to identify knowledge gaps for research and further development of this field.

METHODS

Scoping review.

RESULTS

We included 53 articles, describing studies mainly performed in Europe and North-America (60.4%) and mostly within the last ten years. Only 32% studies included children <4 years. Almost all studies (47/53, 88.7%) were performed in boys with haemophilia, pooling haemophilia A and B (n = 21) and different disease severities (n = 20). Thirteen different generic and five disease-specific HRQoL-questionnaires were applied; all questionnaires were validated for haemophilia specifically. Six (11,3%) combined generic and disease-specific questionnaires. Self-reports were most frequently applied (40/53, 75.5%), sometimes combined with proxy and/or parent-reports (17/53, 32.1%). Eleven studies used a reference group (20.8%). Statistical analyses mostly consisted of mean and SD (77.4%).

CONCLUSION

HRQoL-research is mainly performed in school-aged boys with haemophilia, treated in developed countries. Pitfalls encountered are the pooling of various BDs, subtypes and severities, as well as the application of multiple generic questionnaires prohibiting comparison of results. More attention is needed for broader study populations including other BDs, young children, feminine bleeding issues and platelet disorders, as well as the use of HRQoL as an effect-measurement tool for medical interventions, and more thorough statistical analysis.

Determinants of bleeding before and during immune tolerance in 222 boys with severe hemophilia A and inhibitors >5 BU

ABSTRACT

Prevention of bleeding and its consequences is the main goal of hemophilia treatment and determines treatment choices for patients who develop inhibitors. To assess bleeding before and during immune tolerance induction (ITI) and its association with ITI regimen and inhibitor titer, we selected and analyzed data on patients receiving high-titer inhibitors from the international prospective PedNet cohort study. In total, 222 patients with severe hemophilia A and inhibitor titers of >5 Bethesda units (BU) were followed from the first positive to the first negative inhibitor result (median overall follow-up, 1.7 years). Mean annual (joint) bleeding rates (AJBR) and 95% confidence intervals (CIs) were compared according to treatment and inhibitor titer using multivariable negative binomial regression. Before ITI, 115 patients showed an ABR of 6.1 (5.0-7.4) and an AJBR 2.6 (2.1-3.2). Bleeding was independent of inhibitor titer. During ITI, 202 patients had an ABR of 4.4 (3.9-5.1) and an AJBR of 1.7 (1.5-2.0). AJBR during ITI increased with inhibitor titer (hazard ratio [HR] for ≥200 BU vs 5 to 39 BU [4.9; CI, 3.2-7.4]) and decreased with daily ITI infusions (HR, 0.4; CI, 0.3-0.6) or activated prothrombin complex concentrate prophylaxis (HR, 0.4; CI, 0.2-0.8), whereas ITI dose and recombinant activated factor VII prophylaxis did not independently affect bleeding. These data provide evidence for a protective effect of repeated FVIII infusions (ITI) on bleeding in patients who have developed inhibitors; these data should be used to plan ITI and/or serve as a comparator for prophylaxis with nonreplacement therapy.

Regular prophylaxis with activated prothrombin complex concentrates in pediatric hemophilia

BACKGROUND

Regular prophylaxis with activated prothrombin complex concentrates (aPCCs) is effective in adult patients with hemophilia with inhibitors; however, data in children are scarce.

METHODS

This was a single-center retrospective study at Saitama Children's Medical Center. Patients with severe and moderate hemophilia with inhibitors aged <15 years at the start of aPCCs prophylaxis were included. Medical records were retrospectively reviewed.

RESULTS

We treated nine pediatric patients with hemophilia with inhibitors (median age, 1.9 years; age range, 1.3-12.9 years; inhibitor titers before treatment with aPCCs, 5.9-69 BU/mL) using prophylactic aPCCs (doses, 50-100 U/kg; 2-3 times/week). The median prophylactic period was 13 months (range: 5-31 months). The median annualized bleeding rate (ABR) during prophylactic treatment with aPCCs was 2 (range, 0-17). In four patients, ABR was reduced by 19%-100% with prophylactic aPCCs compared to on-demand aPCCs. An adverse effect of treatment was that a patient with hemophilia B developed nephrotic syndrome 34 months after starting regular prophylaxis with aPCCs.

CONCLUSIONS

Regular prophylactic aPCCs reduced the ABR even in younger children with hemophilia A and B. Serious adverse events include nephrotic syndrome, which requires caution.

Assessing the value of bypassing agent therapy used prophylactic versus on-demand, during immune tolerance induction for treatment of inhibitors: a retrospective chart review

BACKGROUND

Haemophilia A is a bleeding disorder caused by deficiency of coagulation factor VIII (FVIII) which leads to severe and repeated bleedings. There is a need to understand the optimal treatment pathway for FVIII inhibitors with the use of immune tolerance induction (ITI) and the role of haemostatic 'bypassing' agents (BPA) on-demand (OD) or prophylactically (Px). The aim of this study was to gain a better understanding of the real-world use of BPA therapy administered prophylactically or on-demand concomitant with ITI, for the treatment of an inhibitor to FVIII replacement therapy in patients with severe haemophilia A.

METHODS

Retrospective observational data were used to capture disease management information for patients who were aged 16 or under and had received ITI and BPA treatment for their most recent inhibitor from Jan-2015 to Jan-2019, for 47 patients in the UK and Germany. Descriptive comparisons of the clinical effectiveness and resource utilisation of Px and OD BPA therapy during ITI were conducted.

RESULTS

During ITI and BPA treatment, for an inhibitor, bleeding events averaged 1.5 and 1.2 for Px and OD treatment respectively. Compared to only BPA therapy we see 3.4 and 1.4 bleeding events for Px and OD respectively during an inhibitor.

CONCLUSION

Baseline disease characteristics differed between BPA therapy cohorts and this resulted in higher clinical effectiveness of ITI treatment alongside BPA Px than BPA OD during an inhibitor.

Low-dose immune tolerance induction therapy in severe hemophilia a children in China: Starting earlier resulted in better inhibitor eradication outcomes

BACKGROUND

Shorter interval-time from inhibitor detection to starting immune tolerance induction (ITI) might predict better ITI outcomes for severe Hemophilia A (SHA) patients with high-risk-inhibitors. However, the prediction-impact of interval-time for these patients on low-dose ITI strategy remained unclear.

OBJECTIVES

To explore the relationship between interval-time and low-dose ITI outcomes in Chinese SHA children with high-risk-inhibitors.

METHODS

This was a single-center, retrospective study on SHA children with high-risk-inhibitors (each with immediate pre-ITI inhibitor titer>10 Bethesda Units/mL) undergoing low-dose ITI strategy for ≥24 months. ITI outcomes and their predictive factors were evaluated at the 24th month treatment for each patient. The predictive ability of interval-time on ITI success was determined using receiver operating characteristic (ROC) curve.

RESULTS

Among 47 patients investigated, 34 (72.3 %) achieved success. Independent predictor for ITI-outcome on multivariate analysis included the interval-time (p = 0.007) and peak inhibitor-titer (p = 0.011). Shorter interval-time predicted ITI success [cut-off value = 22.3 months, area under ROC-curve (AUC) = 0.701] and early-ITI success within 12 month (cut-off value = 9.4 months AUC = 0.704). Linear regression analysis suggested each month interval-time delay delayed success by 0.1552 month. Unlike the interval-time, peak inhibitor-titer had no success-predictive value in high-peak inhibitor-titer patients on ITI with immunosuppressants.

CONCLUSIONS

Interval-time represented a strong predictive value for outcomes in our low-dose ITI strategy for SHA patients with high-risk-inhibitors. Shorter interval-time was associated with higher success rate and earlier success achievement. The respective interval-time cut-off values were 22.3 months for ITI success and 9.4 months for early-success.

Untreated bleeds in people with hemophilia A in a noninterventional study and intrapatient comparison after initiating emicizumab in HAVEN 1-3

Background

Bleeding in people with hemophilia A can be life threatening, and intra-articular bleeds can result in joint damage. Most clinical studies focus on treated bleeds, while bleeds not treated with coagulation factor(s) (untreated bleeds) are underreported.

Objectives

We assessed the incidence of untreated bleeds during a noninterventional study (NIS) wherein people with hemophilia A, with or without factor VIII (FVIII) inhibitors, were managed according to standard practice.

Patients/Methods

Using the Bleed and Medication Questionnaire, we prospectively collected data from three cohorts: Cohort A, adults/adolescents (age ≥12 years) with FVIII inhibitors; Cohort B, children (aged <12 years) with FVIII inhibitors; Cohort C, adults/adolescents without FVIII inhibitors. Untreated bleeds were analyzed for site, frequency, and etiology of bleeding and compared with those during emicizumab prophylaxis in the same individuals after transferring to a Phase III HAVEN trial.

Results

In the 221 participants enrolled in the NIS (Cohort A, n = 103; Cohort B, n = 24; Cohort C, n = 94), the incidence of untreated bleeds was approximately 40% of all bleeds in people with FVIII inhibitors and 26.2% in adolescents/adults without inhibitors. Approximately 70% of treated bleeds and approximately 54% of untreated bleeds in adults/adolescents were in joints. Untreated joint bleeds were less common (7.1%) in children. Overall, intra-individual comparisons showed reduced treated/untreated bleeds following transition from standard to emicizumab prophylaxis.

Conclusion

A significant proportion of bleeding events are untreated in people with hemophilia A. There is a need to further understand why bleeds remain untreated and to capture such events in clinical studies.

Exposure-Bleeding Count Modeling of Emicizumab for the Prophylaxis of Bleeding in Persons with Hemophilia A with/Without Inhibitors Against Factor VIII

BACKGROUND AND OBJECTIVE

Emicizumab is a monoclonal antibody that bridges activated coagulation factor IX and factor X to restore effective hemostasis in persons with hemophilia A. It is indicated for routine prophylaxis of bleeding episodes in persons with hemophilia A. The aim of the present study is to describe the exposure-response relationship between emicizumab concentrations and bleeding frequency, and to confirm adequate bleeding control of the investigated dosing regimens 1.5 mg/kg once weekly, 3 mg/kg every 2 weeks, and 6 mg/kg every 4 weeks.

METHODS

Treated bleeding events were pooled from 445 persons with hemophilia A with and without inhibitors against factor VIII, participating in six clinical studies. Emicizumab concentrations were predicted using a previously developed population pharmacokinetic model. A count model was used to quantify the exposure-response relationship. These models were used to illustrate the relationship between emicizumab concentrations and cumulative count of bleeding over 1 year (annualized bleeding rate).

RESULTS

The final exposure-response model, based on a generalized Poisson distribution and an inhibitory Emax relationship, adequately describes the relationship between daily emicizumab concentrations and daily bleed frequency. A significant effect of factor VIII prophylaxis among persons with hemophilia A without inhibitors was found. Annualized bleeding rate simulations show that the three emicizumab dosing regimens maintain the concentrations close to the plateau of the effect. At the average steady-state concentration across all regimens (53.5 µg/mL), the predicted mean annualized bleeding rate is 1.28, corresponding to a 94.0% reduction from baseline.

CONCLUSIONS

These results confirm that average emicizumab concentrations achieved with all three emicizumab dosing regimens provide adequate bleeding control.

Nonfactor Therapies: New Approaches to Prophylactic Treatment of Haemophilia

For several decades, the treatment of haemophilia has relied on factor replacement therapy, which restores haemostasis by replacing the missing coagulation factor. In recent years, novel alternative therapies for the treatment of haemophilia in patients with and without inhibitors have been developed. These emergent therapies promote haemostasis by mimicking coagulation factors or inhibiting natural anticoagulants. They provide a less invasive route of administration (i.e. subcutaneous) and some offer reduced frequency of dosing (i.e. every 2 weeks, monthly) compared with the majority of factor replacement therapies, and thus have the potential to simplify treatment, increase adherence and subsequently improve outcomes for patients. Their introduction has transformed the care of haemophilia patients with inhibitors to factor VIII, with similar expectation for haemophilia B patients with inhibitors. However, these therapies also come with several new challenges including their limitation to prophylactic treatment, the observed increased incidence of thrombosis, or their impact on the natural history of the disease and potential disruption of existing treatment guidelines like the use of immune tolerance induction. Moreover, questions remain regarding the long-term impact of non-replacement therapies on joint health as well as the optimal strategy to manage breakthrough bleeds in patients with inhibitors.

Health-related quality of life and health status in adolescent and adult people with haemophilia A without factor VIII inhibitors-A non-interventional study

INTRODUCTION

Real-world data on health-related outcomes in persons with haemophilia A (PwHA) can provide useful information for improving patient care. The global, non-interventional study (NIS; NCT02476942) prospectively collected high-quality data in PwHA, including those without factor VIII (FVIII) inhibitors treated according to local routine clinical practice.

AIM

To report health-related quality of life (HRQoL) and health status of adult/adolescent PwHA without FVIII inhibitors.

METHODS

Participants were PwHA without FVIII inhibitors age ≥12 years; they remained on existing episodic treatment or prophylaxis. HRQoL was assessed by Haemophilia Quality of Life Questionnaire for Adults (Haem-A-QoL) or Haemophilia-Specific Quality of Life Assessment for Children and Adolescents Short Form (Haemo-QoL-SF II). Health status was assessed through EuroQol 5-Dimensions 5-Levels (EQ-5D-5L) index utility score and visual analogue scale (EQ-VAS).

RESULTS

Ninety-four participants enrolled; median age was 34.0 years (range 12-76). Forty-five received episodic treatment and 49 received prophylaxis for a median time of 27.7 weeks and 30.4 weeks, respectively. Mean (standard deviation) baseline Haem-A-QoL total scores were 40.1 (17.0) for the episodic group and 26.6 (14.6) for the prophylaxis group, indicating impairments in HRQoL, which remained consistent over time. Mean EQ-5D-5L IUS scores were similar between treatment regimens (0.8 episodic; 0.9 prophylaxis) and consistent over time. The mean EQ-VAS scores were similar between treatment regimens, and lower on days when bleeding occurred (79.0 vs 85.0 for episodic treatment; 77.0 vs 82.0 for prophylaxis, respectively).

CONCLUSIONS

Adult and adolescent PwHA without FVIII inhibitors had HRQoL impairments regardless of whether they were treated with episodic or prophylactic standard care with FVIII.