Advances in bypassing agent therapy for hemophilia patients with inhibitors to close care gaps and improve outcomes.

In the past, patients with hemophilia and inhibitors have had less-than-optimal treatment and have experienced more orthopedic complications than patients without inhibitors. Bypassing agents offer the potential to close treatment gaps between inhibitor and noninhibitor patients by helping the former better attain key treatment goals, including: facilitating early initiation of treatment and hemostatic control in hemarthroses; providing effective treatment in serious hemorrhagic episodes; and performance of major surgery. Effective treatment with a bypassing agent minimizes joint and/or muscle damage and potentially can serve as an effective prophylactic agent to minimize the number of hemarthroses experienced per year, thereby mitigating the development of arthropathy. The reported efficacy of the currently available bypassing agents ranges from approximately 50-80% (50-64% in controlled studies) for plasma-derived activated prothrombin complex concentrate (pd-aPCC) and 81-91% (in controlled studies) for recombinant activated factor VII (rFVIIa), including use in major orthopedic surgery. Both bypassing agents have undergone key improvements in their formulation and/or properties in recent years. The nanofiltered, vapor-heated formulation of pd-aPCC has diminished the risk of acquiring blood-borne viral infections and the room temperature stable formulation of rFVIIa allows more convenient storage, increased ease to dissolve and inject, and smaller volumes, thereby increasing overall ease of administration. Use of recommended dosing has been demonstrated to provide effective hemostasis with a minimal number of injections for both agents. In this paper, we review the individual characteristics of pd-aPCC and rFVIIa and discuss clinical data from studies conducted in inhibitor patients that demonstrate the potential benefits of these bypassing agents in this difficult-to-treat population, and underscore the potential opportunities to close the gap in care between inhibitor and noninhibitor hemophilic patients.