Nucala (mepolizumab) is a monoclonal antibody (a laboratory-made protein designed to bind to only one substance) that affects the actions of the body’s immune system. The GlaxoSmithKline (GSK) treatment is currently used, together with other medicines, to help control severe asthma. The drug is also being investigated as a potential treatment for eosinophilic granulomatosis with polyangiitis (EGPA) as an add-on therapy to corticosteroids.

EGPA is a type of ANCA vasculitis that is characterized by widespread inflammation in the walls of small blood vessels, eventually leading to tissue and organ damage. People with EGPA may have different organ systems affected and experience symptoms such as fatigue, muscle and joint pain, and weight loss.

How Nucala works

Nucala is a targeted anti-IL-5 monoclonal antibody that binds to interleukin (IL-5), preventing it from binding to its receptor on the surface of certain types of white blood cells called eosinophils and activating them. Inhibiting the binding of  IL-5 reduces eosinophil levels in the blood, other tissues, and sputum.

IL-5 acts as a growth and differentiation factor for both B-cells (another type of white blood cell) and eosinophils, which have a role in protecting the body against infection. Increased production of IL-5 may be related to eosinophil-dependent inflammatory diseases, such as asthma.

Nucala in clinical trials for ANCA vasculitis

A Phase 3 clinical trial (NCT02020889) assessed the efficacy and safety of 300 mg of Nucala in people with EGPA who were under corticosteroid therapy with or without immunosuppressive therapy. Participants were given either 300 mg of Nucala or a placebo administered under the skin once every four weeks, for 52 weeks.

The two primary objectives were the accumulated weeks of remission during the study and the proportion of participants in remission at both week 36 and week 48. Secondary objectives included the time to first relapse and the average daily corticosteroid dose (from week 48 to week 52). The relapse rate and safety were also assessed.

The results showed that Nucala led to more accumulated weeks of remission than the placebo and a higher percentage of participants in remission at both week 36 and 48, allowing for reduced corticosteroid use. However, only about half of the participants treated with Nucala had remission as defined in the protocol of the study.

Other details

GSK recently announced that it submitted a supplemental biologics license application (sBLA) for Nucala to the U.S. Food and Drug Administration (FDA) for the treatment of EGPA.

Common side effects of Nucala include headache, tiredness, back pain, and swelling, redness, burning or itching, and pain where the medicine was injected.

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