Monoclonal antibody
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Emicizumab, sold under the brand name Hemlibra, is a humanized bispecific monoclonal antibody for the treatment of haemophilia A, developed by Genentech and Chugai (both organizations are subsidiaries of Hoffmann-La Roche). A Phase I clinical trial found that it was well tolerated by healthy subjects.
In November 2017, it was approved in the United States for treatment of haemophilia A in those who had developed resistance to other treatments. It was subsequently approved by the US FDA in April 2018 under the breakthrough therapy designation for treatment of haemophila A in those who have "not" developed resistance to other treatments. The U.S. Food and Drug Administration (FDA) considers it to be a first-in-class medication.
Studies indicate that emicizumab is a better therapy compared to the previous generations, due to subcutaneous administration and fewer injections, which reduces injection site reactions and makes therapy less troublesome.
Adverse effects.
The most common adverse reactions (incidence ≥10%) are injection site reactions, headache, and arthralgia. 
Mechanism of action.
Emicizumab binds to both the activated coagulation factor IX and to factor X, mediating the activation of the latter. This is normally the function of coagulation factor VIII, which is missing in haemophilia A patients.
References.
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