Mepolizumab (CRSwNP)

How it works

Mepolizumab is a humanised monoclonal antibody against interleukin-5 (IL-5); by blocking IL-5 binding to its receptor on eosinophils it reduces eosinophil production and survival, dampening the type-2 inflammation that drives polyp formation.

Prescribing in practice

• Hypersensitivity and injection-site reactions can occur, so administer with appropriate observation and do not use to treat acute symptoms or exacerbations.
• Pre-existing helminth infection should be treated before starting, as eosinophils contribute to host defence against parasites.
• It is given by subcutaneous injection at regular intervals as add-on therapy and should be initiated and reviewed by a specialist within agreed access criteria.

Monitoring

Assess polyp size, nasal obstruction and symptom scores at defined review points to confirm continued benefit, and monitor for hypersensitivity reactions around administration.

Counselling the patient

• This is an add-on treatment for nasal polyps, not a reliever for sudden symptoms.
• Keep using your steroid nasal spray unless told otherwise.
• Report any rash, swelling, breathing difficulty or signs of an allergic reaction after injection.

Evidence & guidelines

Mepolizumab is licensed for severe CRSwNP on the basis of randomised trials showing reduced polyp size and nasal obstruction, and is positioned by NICE for specialist add-on use.