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Biologic — Anti-IL-5 Monoclonal Antibody Pregnancy: Avoid — insufficient data; animal studies showed no teratogenicity

Mepolizumab (Eosinophilic GPA)

Brand names: Nucala

Adult dose

Dose: 300 mg subcutaneous injection every 4 weeks (EGPA); 100 mg every 4 weeks (severe asthma — different dose)
Route: Subcutaneous
Frequency: Every 4 weeks
Max: 300 mg every 4 weeks (EGPA)
For eosinophilic granulomatosis with polyangiitis (EGPA, formerly Churg-Strauss syndrome). Administer as 3 × 100 mg injections at separate sites. Designed as steroid-sparing agent. Does not replace glucocorticoids in organ-threatening EGPA — used for maintenance after induction.

Paediatric dose

Route:
Not licensed for paediatric EGPA — seek specialist opinion; licensed for eosinophilic asthma in children ≥6 years at 40 mg/4 weeks

Dose adjustments

Renal

No dose adjustment required

Hepatic

No dose adjustment required

Clinical pearls

  • MIRRA trial (NEJM 2017): mepolizumab 300 mg/4 weeks significantly increased remission rates (28% vs 3% placebo) and reduced accrued weeks in remission — landmark trial for EGPA management
  • EGPA (formerly Churg-Strauss syndrome): triad of asthma, blood eosinophilia (>1.5 × 10⁹/L), and granulomatous vasculitis — eosinophil-driven pathology makes IL-5 inhibition mechanistically sound
  • Steroid-sparing: primary goal is reduction of prednisolone to <7.5 mg/day — mepolizumab allows significant steroid dose reduction in most responders
  • ANCA status: only ~40% of EGPA patients are ANCA-positive (usually MPO-ANCA); eosinophil-dominant disease may respond better to IL-5 inhibition than ANCA-dominant disease
  • Note on dose: EGPA dose is 300 mg (3 × 100 mg injections) — NOT 100 mg used for eosinophilic asthma; prescribe with indication to avoid dosing error

Contraindications

  • Active severe infection
  • Acute EGPA flare with organ-threatening manifestations (mepolizumab not appropriate as sole therapy in this context)
  • Live vaccines

Side effects

  • Injection site reactions
  • Headache
  • Back pain
  • Upper respiratory tract infections
  • Fatigue
  • Hypersensitivity reactions (rare)

Interactions

  • Live vaccines — contraindicated
  • Other immunosuppressants — limited interaction data

Monitoring

  • Blood eosinophil count
  • EGPA activity score (BVAS or EGPA-specific tools)
  • Prednisolone dose at each visit — steroid-sparing assessment
  • Signs of infection
  • Pulmonary function (FEV1, FENO)

Reference: BNFc; BNF 90; NICE TA671; MIRRA Trial (NEJM 2017); EULAR EGPA Guidelines; SPC Nucala. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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