Bleeding Events and Safety Outcomes in Patients with Hemophilia a with Inhibitors: A Prospective, Multicenter, Non-Interventional Study

Introduction: Coagulation factor VIII (FVIII) deficiency in hemophilia A (HA) patients (pts) results in spontaneous bleeding events, secondary arthropathy and diminished quality of life (QoL). FVIII replacement agents, the current standard of care, may require several infusions to treat bleeding events and infusions 2-3 times a week are needed for prevention of bleeding events due to relatively short half-lives. A major challenge of current therapies is development of anti-FVIII alloantibodies (inhibitors), which occur in 15-30% of HA pts, diminish effectiveness of FVIII replacement and are associated with significant morbidity and reduced QoL. Options for pts with inhibitors are limited. Bypassing agents to prevent/treat bleeding events, and immune tolerance induction to eliminate inhibitors, require frequent dosing, are not available in all countries, and have suboptimal efficacy. Thus, a high unmet need exists for safe, more effective and less burdensome options for pts with inhibitors. Emicizumab (ACE910), a bispecific monoclonal antibody in development for the management of HA, binds to FIXa and FX to mimic FVIII cofactor function and may be able to address current treatment needs.

Real world data (RWD) collected from HA pts are considered of high importance for the emicizumab clinical development program, providing the possibility of intra-patient comparison for those who may be subsequently eligible to participate in a pivotal emicizumab Phase 3 study (NCT02622321).

This non-interventional study (NIS) aims to prospectively collect detailed, high-quality data on bleeding events and safety outcomes in HA pts treated according to local routine clinical practice. In the first cohort (Cohort A), data from adult/adolescents with inhibitors were collected.

Methods: This prospective NIS (NCT02476942) was approved by local Ethics review groups, and all pts and/or legal guardians signed informed consent/assent prior to study entry. In Cohort A, eligible pts were ≥12 years old and had congenital HA of any severity; documented history of high-titer FVIII inhibitors (≥5 Bethesda Units/mL); documented treatment with bypassing agents for ≥6 months; and, ≥6 or ≥2 bleeds in the last 6 months on episodic or prophylactic treatment, respectively. Primary objective was to characterize the number of bleeding events over time. Bleeding/bypassing agent data were collected through a bleed and medication questionnaire (BMQ) developed by the Sponsor, as no standard questionnaire is available. BMQ was completed by the pt/legal guardian via an electronic handheld device. Demographic data and medical history were collected from pts' medical records on an electronic Case Report Form. Throughout the study, investigators recorded adverse events (AEs), concomitant medication, and routine laboratory assessment data. At least monthly interactions of pts/legal guardian with a professional from their treatment center were requested to confirm self-reported bleed/medication information.

Results: 103 HA pts with inhibitors (75 on episodic and 28 on prophylactic regimens with bypassing agents) from 33 centers and 12 countries were enrolled in Cohort A. As of 7/21/16, 54 pts had rolled over to the emicizumab Phase 3 study in adults/adolescents with inhibitors. The following Cohort A data will be presented: pt demographics/characteristics; global distribution of pts by country; summary of hemophilia medical history, concomitant medications and surgeries; pts' self-reported information on bleeding events and treatment (all, and by episodic and prophylactic treatment), including bleeding rates, types and locations, reason for coagulation product use, product type used, dose; and, safety.

Conclusion: The NIS will provide high quality documentation of bleeding events and safety outcomes in adult/adolescent HA pts with inhibitors treated with bypassing agents according to local clinical practice. For those participating in the ongoing Phase 3 emicizumab study, these data will provide the opportunity to perform robust intra-patient comparisons of prospectively collected bleeding event/medication data before and during emicizumab treatment. This is the first report of prospective RWD being collected for use as a valid historical control for a pivotal Phase 3 study in HA pts with inhibitors, and a novel and unique approach to bolster data reported in the clinical development of emicizumab.