PERSEPT 1: a phase 3 trial of activated eptacog beta for on-demand treatment of haemophilia inhibitor-related bleeding.

INTRODUCTION: Haemophilia A or B patients with inhibitors have been treated with FVIIa-containing bypassing agents for over 20 years. However, due to uncertainty regarding dose response and thrombotic risk, the use of a gradual, titrated, minimal dosing strategy remains prevalent, potentially hampering early haemostasis. AIM: Evaluate the dose-dependent efficacy, safety and immunogenicity of activated eptacog beta (rhFVIIa), a new recombinant inhibitor bypassing agent for the treatment of bleeding episodes (BEs). METHODS: A Phase 3, randomized, cross-over study of initial dose regimens (IDRs) in 27 bleeding congenital haemophilia A or B subjects with inhibitors was conducted to evaluate on-demand treatment of mild/moderate BEs. Intravenous 75 µg/kg or 225 µg/kg initial doses with 75 µg/kg subsequent doses by schedule were administered until clinical response. RESULTS: The primary endpoint was sustained clinical response within 12 hours, determined by a composite of objective and pain measures. In the 75 µg/kg IDR, 84.9% (95% CI; 74.0%, 95.7%) of mild/moderate BEs at 12 hours were successfully treated compared to 93.2% (95% CI; 88.1%, 98.3%) treated in the 225 µg/kg IDR. Efficacy between the IDRs was statistically different (P<.020) in mild/moderate bleeding episodes. Both IDRs were well tolerated with no detectable immunogenic or thrombotic responses to rhFVIIa or host cell proteins. CONCLUSION: The dose-dependent efficacy seen in this study supports individualizing the initial dose of eptacog beta to optimize clinical response. By reducing uncertainty, the PERSEPT 1 results should increase the adoption of early haemostasis as a treatment goal for clinicians who treat haemorrhage in the inhibitor population.

The future of bypassing agents for hemophilia with inhibitors in the era of novel agents.

Bypassing agents are presently the standard of care for the treatment of bleeding episodes in patients with hemophilia and high-titer inhibitors and are also used for bleed prevention. Only two bypassing agents are available to patients, and these products trace their lineage to the 1970s (activated prothrombin complex concentrates) and the 1980s (recombinant factor VIIa). Given the limited repertoire of available products, clinicians have relied on experience, empirical observation, registry data and individualized care to improve clinical outcomes on a case-by-case basis. Research over the past two decades has culminated in a greatly improved understanding of human coagulation; resulting from this, new products have been developed that offer treatment options and mechanisms of actions that differ from current bypassing agents. The most advanced in clinical development is emicizumab, a bispecific antibody that mimics the function of FVIIIa in the intrinsic Xase complex and is indicated for once-weekly or every-other-week prophylactic dosing in inhibitor patients. Other non-traditional products in clinical development include fitusiran and antibodies directed against tissue factor pathway inhibitor. As non-factor-based therapies become more widely utilized over time, the use of bypassing agents may be expected to decrease; however, bypassing agents will remain essential for the foreseeable future. As such, clinical development of bypassing agents continues, with some products (e.g. eptacog beta) under regulatory review. In this review we examine the optimal use of bypassing agents and their mechanism of action. We also discuss newer products and how these might theoretically be administered in conjunction with traditional bypassing agents.