Mepolizumab

What it is and how it works

Mechanism of Action Mepolizumab is an IL-5 antagonist (IgG1 kappa). IL-5 is the major cytokine responsible for the growth and differentiation, recruitment, activation, and survival of eosinophils. Mepolizumab binds to IL-5 with a dissociation constant of 100 pM, inhibiting the bioactivity of IL-5 by blocking its binding to the alpha chain of the IL-5 receptor complex expressed on the eosinophil cell surface. Inflammation is an important component in the pathogenesis of asthma, CRSwNP, COPD, EGPA, and HES.

Mechanism class: Interleukin-5 Antagonists

Indications

is an interleukin-5 (IL-5) antagonist monoclonal antibody (IgG1 kappa) indicated for: • Add-on maintenance treatment of adult and pediatric patients aged 6 years and older with severe asthma and with an eosinophilic phenotype. • Add-on maintenance treatment of adult patients aged 18 years and older with chronic rhinosinusitis with nasal polyps (CRSwNP). • Add-on maintenance treatment of adult patients with inadequately controlled chronic obstructive pulmonary disease (COPD) and an eosinophilic phenotype. • The treatment of adult patients with eosinophilic granulomatosis with polyangiitis (EGPA). • The treatment of adult and pediatric patients aged 12 years and older with hypereosinophilic syndrome (HES) for greater than or equal to 6 months without an identifiable non-hematologic secondary cause. Limitations of use: Not for relief of acute bronchospasm or status asthmaticus.

Dosage and administration (summary)

• Severe asthma in patients aged 12 years and older: 100 mg administered subcutaneously once every 4 weeks. • Severe asthma in patients aged 6 to 11 years: 40 mg administered subcutaneously once every 4 weeks. • CRSwNP: 100 mg administered subcutaneously once every 4 weeks. • COPD: 100 mg administered subcutaneously once every 4 weeks. • EGPA: 300 mg administered subcutaneously once every 4 weeks. • HES: 300 mg administered subcutaneously once every 4 weeks. Recommended Dosage NUCALA is for subcutaneous use only, and should be injected into the upper arm, thigh, or abdomen . Table 1.

Contraindications

is contraindicated in patients with a history of hypersensitivity to mepolizumab or excipients in the formulation . History of hypersensitivity to mepolizumab or excipients in the formulation.

Warnings and precautions

• Hypersensitivity reactions (e.g., anaphylaxis, angioedema, bronchospasm, hypotension, urticaria, rash) have occurred after administration of NUCALA. Discontinue NUCALA in the event of a hypersensitivity reaction. • Herpes zoster infections have occurred in patients receiving NUCALA. Consider vaccination if medically appropriate. • Do not discontinue systemic or inhaled corticosteroids abruptly upon initiation of therapy with NUCALA. Decrease corticosteroids gradually, if appropriate. • Treat patients with pre-existing helminth infections before therapy with NUCALA.

Pregnancy

Pregnancy Risk Summary The data on pregnancy exposure are insufficient to inform on drug-associated risk. Monoclonal antibodies, such as mepolizumab, are transported across the placenta in a linear fashion as pregnancy progresses; therefore, potential effects on a fetus are likely to be greater during the second and third trimester of pregnancy.

Storage and supply

for Injection NUCALA (mepolizumab) for injection is a sterile, preservative-free, white to off-white, lyophilized powder for reconstitution and subcutaneous injection in a single-dose glass vial with a flip-off seal. The vial stopper is not made with natural rubber latex.

Source: Mepolizumab (Nucala) — US FDA prescribing information, 2025-08-06, DailyMed. Summarised and shortened; the full label governs. Iranian registration, indications and labelling may differ.