Blood Clots Dent Hopes for Hemophilia Drug Emicizumab

Monoclonal antibody promotes blood coagulation

Four patients have experienced serious thrombotic events in a clinical trial of the experimental hemophilia medication emicizumab (ACE910, Genentech/Roche), dimming hopes for the potential blockbuster drug, according to a Reuters report. The patients were being treated for breakthrough bleeding.

A Roche spokesman told Reuters that the cases involved patients who were treated with one of two bypassing agents. He added that both agents––Shire’s FEIBA and Novo’s NovoSeven––carried thrombosis warnings.

Emicizumab is an investigational humanized bispecific monoclonal antibody engineered to simultaneously bind factors IXa and X. The drug mimics the cofactor function of factor VIII and is designed to promote blood coagulation in patients with hemophilia A, a rare genetic disorder, regardless of whether they have developed inhibitors to factor VIII. Emicizumab is administered subcutaneously once weekly, and as its structure is distinct from that of factor VIII, it is not expected to lead to the formation of inhibitors against factor VIII. The drug was created by Chugai Pharmaceutical Co., Ltd., and is being codeveloped by Genentech.

In September 2015, the FDA granted breakthrough therapy status to emicizumab for the prophylactic treatment of patients 12 years of age or older with hemophilia A with factor VIII inhibitors.

In a phase 1 study, emicizumab showed promising results as a prophylactic treatment administered as a weekly subcutaneous injection in people with severe hemophilia A with and without inhibitors to factor VIII.

According to Reuters, emicizumab is being closely watched because it could change the way hemophilia is treated.

Sources: Reuters; November 2, 2016; and Genentech; September 3, 2015.