Nucala (mepolizumab) is a biologic drug used for the treatment of hypereosinophilic syndrome (HES). Credit: GlaxoSmithKline.
Mepolizumab is an IL-5-inhibiting humanised monoclonal antibody. Credit: GlaxoSmithKline.
The US FDA approved Nucala for the treatment of HES in September 2020. Credit: GlaxoSmithKline.

Nucala® (mepolizumab) is the first biologic therapy indicated for the treatment of hypereosinophilic syndrome (HES) in adult and paediatric patients aged 12 years and older.

Nucala is eligible for patients suffering from HES for more than six months without an identifiable non-hematologic secondary cause.

The drug is indicated as an add-on maintenance treatment for patients with severe asthma with an eosinophilic phenotype aged six years and older and for the treatment of eosinophilic granulomatosis with polyangiitis (EGPA) in adult patients. It is also being studied in many other eosinophilic diseases.

Nucala is available in 100mg strength as white to off-white lyophilised powder in a single-dose vial for reconstitution, for subcutaneous administration.

Nucala approvals

Developed by GlaxoSmithKline (GSK), Nucala was initially approved by the US Food and Drug Administration (FDA) as an add-on maintenance therapy for severe eosinophilic asthma in November 2015, while the European Union approved the drug for the condition in December 2015.

The company submitted a supplemental biologics license application (sBLA) for the drug to the FDA for the treatment of EGPA in June 2017, while the approval was granted in December 2017.

In June 2019, Nucala received the FDA approval for two new self-administration methods, an autoinjector, and a pre-filled safety syringe. Nucala is the first respiratory biological drug authorised as an autoinjector for administration.

Nucala was approved for severe eosinophilic asthma in children aged six to eleven years, in September 2019.

The FDA accepted Nucala for priority review for the treatment of patients with HES in May 2020, while the drug received approval for the condition in September 2020.

Nucala holds orphan drug designation from both EMA and FDA for the HES treatment. It is also being studied for the treatment of chronic obstructive pulmonary disease (COPD).

Hypereosinophilic Syndrome (HES) causes and symptoms

Hypereosinophilic Syndrome (HES) is a group of blood disorders characterised by constantly elevated levels of eosinophils in blood for about six months without any recognisable cause.

Eosinophils may infiltrate certain tissues due to overproduction, causing inflammation and organ damage. The disease can worsen if left untreated and can become life-threatening.

Symptoms of HES include anaemia, congestive heart failure, deep venous thrombosis (blood clots in the veins), itching, asthma, skin rashes, difficulty in breathing, vomiting, muscle inflammation, arthritis and diarrhoea.

The disease affects approximately 20,000 people across the world.

Mepolizumab mechanism of action

Mepolizumab is an interleukin-5 (IL-5) antagonist monoclonal antibody. IL-5 is the primary cytokine that is responsible for eosinophils’ growth and survival.

Mepolizumab binds to IL-5 and suppresses bioactivity by blocking its binding to the alpha chain of the IL-5 receptor complex expressed on the cell surface of eosinophil. This controls the IL-5 signalling, reducing the production and endurance of eosinophils.

Clinical trials on Nucala

FDA approval of Nucala is based on the results of a pivotal phase three, multi-centre, randomised, placebo-controlled, double-blind, 32-week clinical trial.

“Eosinophils may infiltrate certain tissues due to overproduction, causing inflammation and organ damage.”

The trial evaluated the safety and efficacy of Nucala in 108 adult and adolescent patients aged 12 years and older with uncontrolled HES.

Recruited patients were randomised to receive 300mg Nucala or placebo once every four weeks.

The primary endpoint of the study was the percentage of patients, experiencing a HES flare during the 32-week treatment period. A HES flare was defined as the deterioration of clinical signs and symptoms of HES or increasing eosinophils at least twice.

Approximately 28% of the patients receiving Nucala experienced a HES flare compared to 56% of patients in the placebo group, over the 32-week treatment period.

The most common side effects observed in patients during the trial were injection site reactions such as pain and swelling.