In late September, GlaxoSmithKline announced FDA approval of its treatment, Nucala, for patients with hypereosinophilic syndrome (HES). The treatment is safe for patients older than 12. Additionally, this approval is meaningful as Nucala now becomes the first biologic approved to treat HES.

Nucala

Nucala (Mepolizumab) was first approved in 2015 to treat patients with severe eosinophilic asthma, a rare and severe form of asthma characterized by high eosinophil levels. Unlike other subtypes of asthma, severe eosinophilic asthma is often treatment-averse. Nucala is a monoclonal antibody which inhibits IL-5, thus reducing eosinophil levels. The Mayo Clinic defines monoclonal antibodies as:

laboratory-produced molecules engineered to serve as substitute antibodies that can restore, enhance or mimic the immune system.

Because Nucala works for conditions associated with eosinophilic inflammation, researchers believed it could be effective for patients with HES. This was studied in a Phase 3 clinical trial. Over a 7.3 month period, 108 patients received either 300mg Nucala subcutaneously every 4 weeks or a placebo. According to the data, Nucala reduced HES symptom flares by up to 50%.

While generally safe and well-tolerated, some adverse reactions did occur. In the Phase 3 HES trial, researchers noted injection site reactions. In clinical trials testing Nucala for severe eosinophilic asthma, adverse reactions included injection site reactions, fatigue, and headaches.