A new retrospective study enrolling patients with hemophilia suggests that, during an inhibitor event, concomitant use of immune tolerance induction (ITI) treatment and a bypassing agent (BPA) administered prophylactically could have higher clinical effectiveness than ITI alongside a BPA on-demand.

The analysis of the clinical effectiveness of BPAs during ITI therapy showed that bleeding events of any type and severity occurred, on average, 1.4 times during ITI, 1.5 times during ITI with a prophylactic BPA, and 1.2 times during ITI with an on-demand BPA.

The average number of bleeding events of any type and severity reported with a BPA only was 2.8 overall, with 3.4 and 1.4 events occurring, on average, when BPA therapy was administered prophylactically and on-demand, respectively.

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Moreover, joint bleeding events occurred 1.2 times overall on average, with averages of 1.3 events during ITI with a prophylactic BPA and 1.1 events during ITI with an on-demand BPA.

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Patients receiving BPA therapy only experienced 2.1 joint bleeding events of any severity, on average, with 2.5 events occurring when BPA therapy was administered prophylactically and 1.2 occurring with an on-demand BPA.

“Although it can be inferred that this study shows that the treatment pathway of BPA concomitant with ITI results in a higher bleeding and joint bleeding rate on average during treatment for an inhibitor to [factor VIII] replacement therapy, there are multiple contextual factors to take into consideration that may support the opposite claim,” the study authors recognized.

The study also reported differences in healthcare resource utilization. Overall, in the 12 months prior to the most recent inhibitor event, patients were hospitalized 1.4 times on average due to causes relating to hemophilia. Patients who received a prophylactic or on-demand BPA during an inhibitor event were hospitalized 1.6 and 1.0 times on average, respectively.

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Inpatient length of stay and stay in days were consistent between the study cohorts, with averages around 3.8 and 3.0 days, respectively. The average number of hospitalizations during an inhibitor event for patients receiving ITI with a BPA was 1.25 to 1.48 for those on a prophylactic BPA and 0.69 for those given an on-demand BPA.

This was a retrospective, multicenter, case-note review of male patients (n=47) with severe hemophilia A who had a recorded incidence of inhibitors to factor VIII replacement therapy.

The study comprised 2 cohorts: 1 receiving a BPA prophylactically alongside ITI for treatment of an inhibitor event and the other receiving ITI only or with a BPA on-demand. Most (72%) participants were under prophylactic treatment, while the remaining patients received on-demand treatment.


Morgan G, Back E, Rosa D, O’Hara J, Finnegan A. Assessing the value of bypassing agent therapy used prophylactic versus on-demand, during immune tolerance induction for treatment of inhibitors: a retrospective chart review. Orphanet J Rare Dis. 2023;18(1):47. doi:10.1186/s13023-023-02654-0