New Data Reinforce Safety Profile of Emicizumab in Patients with Hemophilia A


Trial identifies no new safety signals, as emicizumab continues to demonstrate effective bleeding control with a high proportion of participants achieving zero treated bleeds.

A final analysis of data from the phase 3b STASEY study supports the benefit and risk profile of emicizumab (Hemlibra) in patients with hemophilia A, according to a press release from Genentech.

Emicizumab is a bispecific factor IXa- and factor X-directed antibody that is designed to join both factor IXa and X. These proteins are necessary to activate the natural coagulation cascade and restore the blood clotting process for patients with hemophilia A.

The trial identified no new safety signals and emicizumab continued to demonstrate effective bleeding control with a high proportion of participants achieving zero treated bleeds, according to the researchers. The trial investigated longer-term treatment with emicizumab in adults and adolescents with hemophilia A with inhibition of factor VIII, the clotting protein that is lacking in patients with hemophilia A.

Nearly one-third of patients with severe hemophilia A develop factor VIII inhibitors, which bind to and block the efficacy of replacement factor VIII. Individuals with these inhibitors have a greater risk of frequent bleeding, including life-threatening bleeds, and may have more challenges in their day-to-day lives than patients who do not have factor VIII inhibitors.

The final analysis from the STASEY trial included data from 193 individuals with hemophilia A and factor VIII inhibitors who received emicizumab prophylactically once weekly for up to 2 years. The data analysis did not show any new cases of thrombotic microangiopathy or serious thrombotic events related to the drug.

The most common adverse events (AEs) occurring in 10% or more of patients in the STASEY study were joint pain (17.1%), nasopharyngitis (15.5%), headache (15%), injection site reactions (11.4%), and fever (10.9%). Furthermore, 18.1% of participants reported an emicizumab-related AE, with injection site reaction being the most common (9.8%).

Study findings also reinforced that emicizumab is associated with a low incidence of anti-drug antibody (ADA) development. Ten (5.2%) participants tested positive for ADAs, 2.6% of whom were classified as having ADAs that were neutralizing in vitro. ADA development did not impact the efficacy or safety of emicizumab in any of the 10 patients, and none had ADAs that resulted in a decrease in emicizumab plasma concentration. None of the ADA-positive participants experienced a treated bleed and the ADAs disappeared over time, according to the study.

Emicizumab continued to demonstrate effective bleed control, with 82.6% of participants experiencing no bleeding episodes that required treatment. Annualized bleeding rates were consistent with previously reported data from the pivotal HAVEN studies.

“As the treatment landscape evolves, determining the long-term benefit/risk profile of medicines for people living with hemophilia A remains a top priority for the community,” said Levi Garraway, MD, PhD, chief medical officer and head of global product development at Genentech, in the press release. “These results provide further confidence in Hemlibra’s favorable safety profile in people with hemophilia A with factor VIII inhibitors, who have historically faced significant treatment challenges.”


New Data for Genentech’s Hemlibra (emicizumab-kxwh) Reinforce Safety Profile in People With Hemophilia A. News release. Genentech. July 18, 2021. Accessed July 19, 2021.

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