A new observational study sponsored by the University Hospital of Grenoble, France, aims to evaluate the effect of emicizumab (Hemlibra®) on a coagulation test used as a point-of-care device to monitor heparin therapies during cardiac surgeries and cardiac catheterizations.

The study, which is not yet recruiting, will enroll 15 participants with severe hemophilia who are under emicizumab treatment for more than 4 weeks. Participants must be 18 years or older.

The primary outcome measure is modification of activating clotting time (ACT) by emicizumab.

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“Because ACT is activated through the intrinsic pathway, it may also be shortened by emicizumab. Prophylactic treatment with emicizumab would make it impossible to use ACT for heparin therapy in a hemophiliac patient benefiting from this treatment,” the study’s authors explained.

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The investigators will measure ACT using the i-STAT Alinity device in patients with severe hemophilia under emicizumab and healthy volunteers. The measurements will occur after in vitro spiking with unfractionated heparin of blood samples from patients with severe hemophilia A already treated with emicizumab, and after in vitro spiking with unfractionated heparin with or without emicizumab in blood samples from healthy volunteers.

Patients receiving anticoagulants or infusion of factor VIII (<5 days), protected persons, and patients who refuse to participate are excluded from the study.

Emicizumab is a bispecific humanized monoclonal antibody that is administered subcutaneously. It works by mimicking the actions of factor VIII, thus improving homeostasis. Prophylaxis with emicizumab provides a constant level of coagulation similar to that observed in patients with minor hemophilia A whose factor VIII level is 10% to 15%.

The US Food and Drug Administration has approved emicizumab for routine prophylaxis to prevent or reduce the frequency of bleeding episodes in adult and pediatric patients with hemophilia A with or without factor VIII inhibitors.


Impact of emicizumab on activated clotting time using the i-STAT alinity analyzer (EMISTAT). ClinicalTrials.gov. May 12, 2023. Accessed May 16, 2023.