How it is administered

Mepolizumab is given as a subcutaneous injection (an injection under the skin). It comes in several forms:

• A lyophilized powder in a single-dose vial that must be reconstituted by a healthcare professional.
• Prefilled autoinjectors and prefilled syringes for subcutaneous injection, available in 100 mg/mL and 40 mg/0.4 mL doses.

The injection is usually given in the upper arm, thigh, or abdomen. For some conditions, multiple injections may be required at one time (e.g., 300 mg as three 100 mg injections). The dosing schedule is typically every 4 weeks.

How it works

Mepolizumab is a monoclonal antibody that targets interleukin-5 (IL-5), a protein that plays a major role in the growth, activation, and survival of eosinophils. Eosinophils are a type of white blood cell involved in inflammation and are often elevated in certain diseases, including some blood cancers and related conditions.

By binding to IL-5, mepolizumab prevents it from attaching to its receptor on eosinophils. This reduces the number of eosinophils in the blood and tissues, helping to control diseases where these cells cause problems. In blood cancers, particularly hypereosinophilic syndrome (HES) and eosinophilic granulomatosis with polyangiitis (EGPA), reducing eosinophil levels can help manage symptoms and reduce disease activity.

Who Should take it

Mepolizumab is indicated for:

• Adults and children aged 12 years and older with hypereosinophilic syndrome (HES) for at least 6 months without an identifiable non-hematologic secondary cause.
• Adults with eosinophilic granulomatosis with polyangiitis (EGPA).

It is also used as an add-on maintenance treatment for severe asthma with an eosinophilic phenotype and other conditions, but for blood cancer purposes, its main use is in HES and EGPA. Patients should have a confirmed diagnosis and be under the care of a specialist familiar with these conditions.

Who should not take it

Mepolizumab should not be used by anyone with a known hypersensitivity to mepolizumab or any of its ingredients. Signs of hypersensitivity can include rash, swelling, difficulty breathing, or severe allergic reactions.

It is not intended for the treatment of acute symptoms or emergencies, such as sudden asthma attacks or acute worsening of disease. Patients with active parasitic (helminth) infections should be treated for those infections before starting mepolizumab. If a patient develops a parasitic infection while on mepolizumab and does not respond to treatment, the medication should be stopped until the infection is resolved.

Commonly used with

For blood cancer-related conditions like HES and EGPA, mepolizumab is often used alongside other therapies such as corticosteroids (like prednisone) and sometimes immunosuppressive or cytotoxic medications. The goal is often to reduce the need for steroids or other drugs and help control symptoms more effectively.

Commonly tested with

In clinical studies for HES and EGPA, mepolizumab has been tested in combination with standard therapies, including corticosteroids and immunosuppressive agents. Patients in these studies typically continued their background therapy while receiving mepolizumab, allowing researchers to see if the addition of mepolizumab provided extra benefit.