Anti-IL-5 receptor alpha monoclonal antibody (anti-eosinophilic biologic) Pregnancy: US label section 8.1: data on pregnancy exposure from clinical trials are insufficient to inform on drug-associated risk. Monoclonal antibodies such as benralizumab are transported across the placenta during the third trimester, so potential effects on the fetus are likely to be greater then. Asthma control should be closely monitored in pregnant women and treatment adjusted as necessary.

Benralizumab

Brand names: Fasenra (30 mg/mL prefilled syringe)

Benralizumab is a monoclonal antibody used as add-on therapy for severe eosinophilic asthma in patients inadequately controlled on high-intensity inhaled therapy.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: 30 mg (one injection)

Route: Subcutaneous injection into the thigh or abdomen (the upper arm may also be used if a healthcare provider or caregiver gives the injection)

Frequency: Every 4 weeks for the first 3 doses, then every 8 weeks thereafter (asthma, adults and patients 12 years of age and older)

No UK SPC section was available in this bundle - dose taken from the US FDA prescribing information for FASENRA (AstraZeneca, label date 2026-05-13); verify against the UK SPC before publication. For EGPA and HES the US label recommends 30 mg subcutaneously once every 4 weeks (no loading schedule). Paediatric patients 6 to 11 years of age with asthma are dosed by weight band, not per kg: less than 35 kg, 10 mg every 4 weeks for the first 3 doses then every 8 weeks thereafter; 35 kg or more, 30 mg every 4 weeks for the first 3 doses then every 8 weeks thereafter - verify against a children's formulary. In asthma patients aged 6 to 11 years weighing 35 kg or more, the FASENRA PEN autoinjector should only be administered by a caregiver or healthcare provider. Warm the carton at room temperature (up to 25 C) for about 30 minutes before injecting. Must not be used to treat acute asthma symptoms, acute exacerbations, acute bronchospasm or status asthmaticus. Do not discontinue systemic or inhaled corticosteroids abruptly on starting therapy - decrease gradually if appropriate. Treat pre-existing helminth infections before starting therapy. No interactions section was present in the fetched label, and the US warnings/adverse-reactions sections were truncated at the source-fetch limit.

Dose auto-extracted from US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Known hypersensitivity to benralizumab or any of its excipients

Side effects

Headache (asthma, EGPA and HES; incidence 5% or more)
Pharyngitis (asthma)
Hypersensitivity reactions including anaphylaxis, angioedema, urticaria and rash
Influenza-like illness (HES)

Clinical monograph

How it works

It binds the interleukin-5 receptor alpha subunit on eosinophils and, by engaging natural killer cells, induces their rapid depletion, reducing eosinophilic airway inflammation.

Prescribing in practice

Hypersensitivity reactions including anaphylaxis can occur, so administer where these can be recognised and managed.
It is given by subcutaneous injection and is for maintenance, not acute exacerbations or bronchospasm.
Any pre-existing helminth infection should be treated before starting, as eosinophils contribute to parasite defence.

Monitoring

Monitor for hypersensitivity reactions after dosing and review asthma control and exacerbation frequency over time.

Counselling the patient

This injection is an add-on and does not replace your inhalers.
Report rash, swelling or breathing difficulty after an injection.
Do not stop your other asthma medicines unless advised.

Evidence & guidelines

NICE recommends benralizumab as an option for severe eosinophilic asthma within defined eligibility criteria.

Reference: NICE TA565; SIROCCO Trial (Bleecker et al, Lancet 2016); CALIMA Trial; ZONDA Trial (Nair et al, NEJM 2017); Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways