A new study is evaluating the optimal dosage of bypassing agents (BPAs) for concomitant use with emicizumab prophylaxis among patients with hemophilia A and factor VIII (FVIII) inhibitors, according to an article published in BMJ Open.

Hemophilia A, an inherited bleeding disorder, is frequently treated with replacement therapy, which may reduce the number of bleeds a patient experiences. Prophylaxis with FVIII products has, furthermore, improved health-related quality of life in this patient population.

There is, however, evidence that FVIII product infusion may pose both a physical and cognitive burden on patients, especially pediatric patients. FVIII inhibitors also pose a threat to disease management by rendering inactive standard therapeutic regimens.

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In this circumstance, determining the optimal treatment strategy is difficult. Emicizumab is an antibody targeting activated FIX and FX, and has been shown to supplement FVIII function in case if the presence of inhibitors.

While emicizumab was approved in the United States because of its comparable effects on patient quality of life, its use as a prophylactic has been linked with several issues, including thrombotic events, particularly in the case of concomitant BPA use. It is, furthermore, unclear how best to monitor patients receiving emicizumab.

The single-arm, multi-center UNEBI study aims to include 60 patients with hemophilia A with FVIII inhibitors to evaluate outcomes after initiation of emicizumab and concomitant BPAs. The researchers plan to monitor coagulation before and after bleeding events and surgical procedures. The study’s primary endpoint is improvement in the maximum coagulation rate by clot waveform analysis (CWA) prior to and after administration of BPAs in fixed doses.

“Although clinicians need to pay attention to possibilities of both under-treatment (insufficient haemostasis) and overtreatment (thrombotic adverse event), a suitable monitoring tool to evaluate haemostatic function comprehensively remains to be established,” the authors wrote. “The UNEBI Study has just started to find the answer to such clinical enigmas.”

Disclosure: The study author(s) declared affiliations with biotech, pharmaceutical, or device companies. Please see the original reference for a full list of authors’ disclosures. 


Ogiwara K, Taki M, Suzuki T, et al. Assessment of global coagulation function under treatment with emicizumab concomitantly with bypassing agents in haemophilia A with inhibitor (UNEBI Study): multicentre open-label non-randomised clinical trial. BMJ Open. 2022;12(2):e056922. doi:10.1136/bmjopen-2021-056922