Anti-IL-5 receptor alpha monoclonal antibody (anti-eosinophilic biologic) Pregnancy: Avoid — insufficient data. Effective contraception advised.

Benralizumab

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

Adult dose

Dose: 30 mg SC every 4 weeks for first 3 doses, then 30 mg SC every 8 weeks

Route: Subcutaneous injection (upper arm, thigh, or abdomen)

Frequency: Monthly × 3 loading doses, then every 8 weeks

Max: 30 mg per dose

Severe eosinophilic asthma (blood eosinophils ≥150 cells/mcL at initiation or ≥300 historically). Unique mechanism: targets IL-5 receptor alpha — depletes eosinophils via ADCC (antibody-dependent cellular cytotoxicity) more rapidly than mepolizumab. NICE TA565. Review at 12 months — continue only if ≥50% reduction in exacerbations.

Paediatric dose

Route: SC

Frequency: Monthly × 3, then every 8 weeks

Max: 30 mg per dose

Concentration: 30 mg/mL mg/ml

Licensed ≥12 years in the UK for severe eosinophilic asthma. Same adult dosing regimen applies.

Dose adjustments

Renal

No dose adjustment required.

Hepatic

No dose adjustment required.

Clinical pearls

SIROCCO and CALIMA trials: benralizumab reduces exacerbations by 51–59% in severe eosinophilic asthma with blood eosinophils ≥300 cells/mcL
ADCC mechanism: depletes eosinophils more rapidly than mepolizumab (IL-5 ligand blockade) — blood eosinophils approach zero within weeks
Advantage over mepolizumab: 8-weekly maintenance dosing after loading (vs 4-weekly for mepolizumab) — improved convenience
NICE TA565 (2019): recommended for severe eosinophilic asthma uncontrolled on step 4 therapy with blood eosinophils ≥300 cells/mcL
Oral corticosteroid sparing: ZONDA trial — 75% reduction in OCS requirement

Contraindications

Active helminth (parasitic) infection — treat before starting
Hypersensitivity to benralizumab

Side effects

Injection site reactions
Headache
Pharyngitis
Hypersensitivity reactions (rare anaphylaxis — observe 30 min post-injection for first dose)
Herpes zoster

Interactions

Live vaccines — avoid during treatment
Minimal systemic drug interactions — monoclonal antibody

Monitoring

Blood eosinophil count (baseline for eligibility)
Exacerbation frequency (response assessment at 12 months)
OCS dose (opportunity for steroid sparing)
Parasitic infection risk

Reference: BNFc; BNF; NICE TA565; SIROCCO Trial (Bleecker et al, Lancet 2016); CALIMA Trial; ZONDA Trial (Nair et al, NEJM 2017). Verify against your local formulary and the latest BNF before prescribing.

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways