Hemophilia Natural History Study (ATHN 7): Baseline Characteristics, Adverse Events, and Self-Reported Health Status of Individuals with Hemophilia a and B

INTRODUCTION

The recent introduction of new therapies for hemophilia A and B (HA and HB) mandates careful monitoring of the safety of these treatments as their use becomes more widespread. The American Thrombosis and Hemostasis Network (ATHN) collects information about the use of all HA and HB therapies through the more than 140 ATHN-affiliated hemophilia treatment centers (HTCs) in the United States (US). The primary aim of ATHN 7: A Natural History Cohort Study of the Safety, Effectiveness, and Practice of Treatment for People with Hemophilia is to monitor the safety of current hemophilia therapies. Secondary aims include assessment over time of real-world effectiveness and patient experience of current therapies.

METHODS

ATHN 7 is being sponsored by ATHN. It is a longitudinal, prospective cohort study being conducted at over 20 ATHN-affiliated sites in the US. The study is approved by central and local institutional review boards. Any person with a diagnosis of congenital hemophilia A or B (factor VIII or IX activity < 50%) who receives care at a participating site is eligible for inclusion. All participants and parents/guardians sign informed consents and assents prior to participation. Patients are excluded if they have any other known bleeding disorder. Adverse events, including those events designated by the European Haemophilia Safety Surveillance (EUHASS) group as well as other adverse events of special interest, are recorded and monitored. Demographic and clinical information are collected at baseline and at least quarterly through patient interview and medical record review. Health status is measured using the 5-level EuroQoL-5D questionnaire (EQ-5D-5L). Descriptive statistics of the baseline medical history and demographic data are used to characterize the study population.

RESULTS

The first participant consented to ATHN 7 in February 2019. As of 06/30/2020, a total of 367 subjects were enrolled in the study from 24 sites. Baseline demographics, clinical characteristics, and treatments are shown in Table 1. Most participants (69.9%) had severe HA. Approximately half of the participants were being treated with clotting factor as their primary therapy and half with a bispecific antibody. Adverse events reported to date include allergic reactions/redness at the injection site, rash unrelated to treatment, and a severe subdural hematoma due to a fall, all in patients receiving emicizumab (Table 2). At baseline, problems with mobility, self-care, and completing usual activities were reported by 32.9%, 13.0%, and 33.7% of participants, respectively. Problems with pain and anxiety were reported by 52.4% and 34.1% of participants (Figure 1). The average health status rating was 83.4 out of 100 (Figure 2).

DISCUSSION

These results demonstrate the capability of ATHN 7 to enroll a large cohort of subjects from multiple sites, monitor safety events, and assess outcomes related to living with and being treated for HA and HB. Adverse events attributed to any hemophilia therapy have been limited to minor skin reactions and have not led to product discontinuation. One subject experienced a trauma-related subdural hemorrhage, which provides important information on the risk of bleeding from severe/significant trauma in those receiving emicizumab. We provide a sobering picture of the high prevalence of difficulties with activities of daily living, pain, and mental health concerns. Despite many advances in therapy, hemophilia continues to have a real, everyday impact on the lives of our patients.

CONCLUSIONS

During the first 16 months of enrollment in the ATHN 7 study, we observed skin reactions, as well as one severe, unanticipated bleeding event due to trauma. At baseline, pain, anxiety/depression, and impaired physical function were concerns for a significant proportion of the individuals in the study.