A new study has found that emicizumab therapy is associated with reduced bleeding rates and improved musculoskeletal health in people with severe hemophilia A.

The study, published in the journal Haemophilia, noted that inhibitors can quickly recur in patients upon switching to emicizumab if they are not fully tolerized to the medication.

“Emicizumab is a recombinant, humanised bispecific monoclonal antibody mimicking FVIII by binding to activated coagulation factors IX and X.2,” the authors wrote. “As it was newly approved, we conducted a controlled prospective observational study at the Quebec Reference Centre for Inhibitors (QCRI) from July 2019 to January 2022 to evaluate the efficacy of emicizumab to control or prevent bleeding in our participants compared to their previous standard treatments.”

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The research team assessed a cohort of 9 adult male and 8 pediatric male participants with severe hemophilia A and a history of inhibitors, median age 19 years, and who had received emicizumab for at least 10 months on study completion. Data on coagulation parameters, antifactor FVIII antibody titers, joint health scores, and patient-reported outcomes were collected, and when feasible, blood samples were also taken.

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The results revealed improved bleeding rates and musculoskeletal health parameters among patients switched to emicizumab, in addition to improved overall patient-reported outcomes.

However, in those patients who were not fully tolerized to emicizumab, inhibitor recurrence occurred rapidly, even with regular FVIII administration. The authors note that this result could have major implications for the management of these patients in terms of breakthrough bleeding or surgery.

The authors caution that the small sample size and the inability to conduct on-site visits during the COVID-19 pandemic limit the ability to draw firm conclusions.


Dubé E, Merlen C, Bonnefoy A, et al. Switching to emicizumab: a prospective surveillance study in haemophilia A subjects with inhibitors. Haemophilia. Published online October 31, 2022. doi:10.1111/hae.14685