Emicizumab

Emicizumab is a humanized bispecific monoclonal antibody marketed under the brand name Hemlibra. It is used for the prevention of bleeding in people with hemophilia A. Its mechanism is to act as a factor VIII mimetic by binding simultaneously to activated factor IX (FIXa) and factor X (FX), drawing them together to enable FX activation and thrombin generation in the absence or deficiency of functional FVIII. This bypasses the need for FVIII in the coagulation cascade and provides a subcutaneous prophylaxis rather than intravenous therapy.

Indications include prophylaxis to reduce bleeding episodes in people with hemophilia A, including those with and without inhibitors to factor VIII. It is not used to treat acute bleeds.

Administration and dosing: Emicizumab is given by subcutaneous injection and has a long half-life, allowing regimens with once-weekly, every-two-weeks, or every-four-weeks maintenance dosing after an initial loading period.

Efficacy and safety: In clinical trials, emicizumab substantially reduced annualized bleeding rates compared with standard care. Common adverse effects include injection-site reactions and headaches. Serious safety considerations include a risk of thrombotic microangiopathy or thrombosis when used with activated prothrombin complex concentrates; combinations with certain bypassing agents should be avoided or used with caution. Hypersensitivity and anti-drug antibodies may occur, though neutralizing antibodies are uncommon.

Regulatory status: Emicizumab is available by prescription in many regions for hemophilia A prophylaxis and is subject to ongoing regulatory oversight and post-market safety monitoring.