Mepolizumab
Biologics for asthma
Biologics for asthma
An anti-IL-5 antibody that lowers eosinophils, used in severe eosinophilic asthma, COPD, nasal polyps, EGPA and hypereosinophilic syndrome.
Quick facts
- Group
- Biologics for asthma
- Target
- Interleukin-5 (IL-5)
- Used for
- Severe eosinophilic asthma
- Key effects
- Injection-site pain · Headache · Dry
- Monitor
- Blood eosinophil count · Exacerbations
- ATC
- R03DX09
No doses: the clinician sets them by the current guideline.
Mechanism of action
Mepolizumab is a humanised monoclonal antibody that binds interleukin-5 and stops it from attaching to its receptor on eosinophils. IL-5 is the main cytokine for eosinophil maturation, activation and survival, so blood and tissue eosinophils fall. In eosinophilic asthma this reduces exacerbations and the need for oral corticosteroids.
- Mepolizumab binds circulating IL-5
- IL-5 cannot reach its receptor on eosinophils
- Eosinophils mature less and die sooner
- Eosinophilic airway inflammation and flare-ups fall
Indications
- Severe eosinophilic asthma, as add-on maintenance Asthma →
- COPD with an eosinophilic phenotype Chronic obstructive pulmonary disease (COPD) →
- Chronic rhinosinusitis with nasal polyps Chronic rhinosinusitis and nasal polyps →
- Eosinophilic granulomatosis with polyangiitis (EGPA) Eosinophilic granulomatosis with polyangiitis (Churg–Strauss) →
- Hypereosinophilic syndrome Hypereosinophilic syndrome →
Adverse effects
Common
- Injection-site pain, redness or swelling
- Headache
- Back pain and muscle spasms
- Dry, itchy skin or eczema
Contraindications
- Hypersensitivity to mepolizumab
- Not for acute bronchospasm or status asthmaticus
- Existing helminth infection is treated first
Key interactions
- Oral and inhaled corticosteroids
- Are not stopped abruptly; dose reduction is gradual and supervised
What is monitored
- Blood eosinophil count (selection and response)
- Exacerbations and oral corticosteroid use
- Hypersensitivity after injections
Administration and safety
- Subcutaneous injection in a clinic or at home after training
- Injected into the upper arm, thigh or abdomen; vials, prefilled syringes and autoinjectors exist
Pregnancy and breastfeeding
Antibodies cross the placenta, especially late in pregnancy; data are limited and use is decided with the specialist.
Nursing care
- Ask about worm infections and shingles vaccination before starting
- Teach signs of allergic reaction
- Remind that the rescue inhaler is still needed and steroids are not stopped suddenly
Pharmacokinetics
- Absorption
- Subcutaneous injection, slowly absorbed
- Elimination
- Broken down like other antibodies (proteolysis)
- Onset and duration
- Eosinophils fall within days; clinical benefit builds over weeks to months
Test yourself
Think of the answer, then tap the question to see it.
Which cytokine does mepolizumab block?
Interleukin-5.
Which blood test helps select patients for mepolizumab?
The blood eosinophil count.
What are two non-asthma indications of mepolizumab?
EGPA and hypereosinophilic syndrome (also nasal polyps and eosinophilic COPD).
Connections
← Back to the class: Biologics for asthma
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Mepolizumab Injection: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2025); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
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Representative model, for educational purposes only.