Common brand names

• Nucala

How it is administered

Mepolizumab is given as a subcutaneous injection (under the skin). It is available as a lyophilized powder for reconstitution or as a prefilled syringe or autoinjector. The injection is typically administered in the upper arm, thigh, or abdomen. The dosage and frequency depend on the condition being treated, but for most indications, it is given every 4 weeks. For some conditions, such as hypereosinophilic syndrome (HES), the dose is 300 mg (administered as three 100 mg injections) every 4 weeks.

How it works

Mepolizumab is a monoclonal antibody that targets interleukin-5 (IL-5), a protein that plays a key role in the growth, activation, and survival of eosinophils—a type of white blood cell involved in inflammation. By binding to IL-5, mepolizumab blocks its interaction with the IL-5 receptor on eosinophils, reducing their numbers in the blood and tissues.

This action helps decrease inflammation caused by eosinophils, which is important in diseases where these cells are overactive, such as severe asthma, eosinophilic granulomatosis with polyangiitis (EGPA), and hypereosinophilic syndrome (HES). The reduction in eosinophils can help control symptoms, reduce flare-ups, and improve quality of life for patients with these conditions.

Who should take it

Mepolizumab is approved for use in adults and certain pediatric patients with:

• Severe asthma with an eosinophilic phenotype (ages 6 and older)
• Eosinophilic granulomatosis with polyangiitis (EGPA, adults)
• Hypereosinophilic syndrome (HES, ages 12 and older)
• Chronic rhinosinusitis with nasal polyps (adults)
• Chronic obstructive pulmonary disease (COPD) with an eosinophilic phenotype (adults)

It is used as an add-on maintenance treatment for these conditions, especially when symptoms are not well controlled with standard therapies. For blood cancers like Chronic Myelomonocytic Leukemia (CMML), mepolizumab is not specifically indicated, but it may be considered in rare cases of HES associated with blood cancers if eosinophils are significantly involved.

Who should not take it

Mepolizumab should not be used by anyone who has had a previous allergic reaction (hypersensitivity) to mepolizumab or any of its ingredients. Signs of an allergic reaction can include rash, swelling, difficulty breathing, or severe dizziness.

It should also be used with caution in patients with active parasitic (helminth) infections, as eosinophils play a role in fighting these infections. If you have a known parasitic infection, it should be treated before starting mepolizumab. If you develop a parasitic infection while on mepolizumab and it does not respond to treatment, your doctor may recommend stopping the medication until the infection is resolved.

Commonly used with

Mepolizumab is commonly used alongside other standard treatments for the underlying disease, such as inhaled or oral corticosteroids, immunosuppressive agents, or other biologic therapies, depending on the specific condition. For example, in severe asthma or EGPA, it is often added to ongoing corticosteroid therapy to help reduce steroid use and improve disease control.

Commonly tested with

In clinical trials, mepolizumab has been tested in combination with standard-of-care therapies, such as corticosteroids and other immunosuppressive medications. It has not been shown to have significant drug interactions with commonly used small molecule drugs. No formal drug interaction studies have been performed, but population data suggest it can be safely used with other medications typically prescribed for asthma, EGPA, HES, and related conditions.