Emicizumab has confirmed prior results for safety and efficacy for patients with hemophilia A with factor VIII inhibitors, according to the results of a phase III study presented at the International Society on Thrombosis and Haemostasis (ISTH) 2021 annual congress.

Emicizumab mimics the function of missing activated factor VIII in patients with hemophilia A. The STASEY trial (ClinicalTrials.gov Identifier: NCT03191799) included data for 193 patients who received at least 1 dose of emicizumab.

Patients were given emicizumab subcutaneously once a week for up to 2 years, with a median treatment duration of 103.1 weeks. A total of 17.1% of patients experienced arthralgia, 15.5% experienced nasopharyngitis, and 15% had headache.

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There were 2 patients who had thromboembolic events, which were reported at the study’s interim analysis, and included myocardial infarction and hypertrophic clot. A total of 2 deaths were reported during the trial, but both were unrelated to emicizumab.

A total of 82.6% of participants had no treated bleeds, and the mean annualized bleed rate for treated bleeds was 0.5. There were 10 patients who developed anti-drug antibodies.

Overall, the results of this study confirmed the results of the HAVEN clinical trials, with no new safety signals.


Jiménez-Yuste V, Peyvandi F, Klamroth R, et al. Final analysis of the STASEY trial: a single-arm, multicenter, open-label, phase III clinical trial evaluating the safety and tolerability of emicizumab prophylaxis in persons with hemophilia A (PwHA) with factor (F)VIII inhibitors. Paper presented at: International Society on Thrombosis and Haemostasis (ISTH) 2021 Congress; July 17-21, 2021; virtual. Abstract PB0521.