Nucala (Mepolizumab)

Mepolizumab (Nucala) targets the interleukin‑5 pathway and is indicated for several eosinophilic disorders.

• Severe eosinophilic asthma: Reduces exacerbations and improves control in patients with high eosinophil counts.
• Eosinophilic granulomatosis with polyangiitis (EGPA): Helps achieve remission and reduces disease activity.
• Chronic rhinosinusitis with nasal polyps: Decreases polyp size and improves sinus symptoms.

• Mepolizumab is a humanized IgG1 monoclonal antibody that binds selectively to interleukin‑5 (IL‑5). By preventing IL‑5 from interacting with its receptor on eosinophil precursors and mature eosinophils, the drug blocks eosinophil differentiation, activation, recruitment and survival, leading to reduced eosinophil counts in blood and tissues and thereby mitigates the inflammatory processes that drive eosinophil‑mediated airway and tissue damage. This targeted approach results in clinical improvement in the associated diseases.

Mepolizumab may cause a range of adverse reactions, which are categorized by frequency and severity.

Common Side Effects

• Injection site reactions: pain, redness, or swelling at the injection site.
• Headache: mild to moderate headache reported.
• Upper respiratory tract infection: symptoms such as sore throat or nasal congestion.
• Fatigue: general feeling of tiredness.
• Arthralgia: joint pain without swelling.

Serious or Rare Side Effects

• Anaphylaxis: severe allergic reaction requiring immediate medical attention.
• Hypersensitivity reactions: including rash, angioedema, or bronchospasm.
• Parasitic infections: increased risk due to reduced eosinophils.
• Immunogenicity: development of anti‑drug antibodies that may affect efficacy.
• Serum sickness–like reaction: fever, rash, arthralgia, and lymphadenopathy.

When prescribing Mepolizumab, clinicians should consider several precautionary measures to ensure safe use.

• Patient selection: confirm diagnosis of eosinophilic disease and assess eosinophil count.
• Infection risk: evaluate for active parasitic infections before initiating therapy.
• Hypersensitivity: avoid use in patients with known severe allergy to Mepolizumab or its excipients.
• Monitoring: regularly monitor eosinophil levels and clinical response during treatment.
• Vaccination: defer live vaccines while receiving the drug.
• Store at 2-8°C: keep refrigerated, protect from light, do not freeze or shake.

Mepolizumab has a limited interaction profile, but certain concomitant therapies require attention.

Major Interactions (Avoid)

• Live vaccines: concurrent administration may increase risk of vaccine‑related infection.
• Immunosuppressants: may augment immunosuppression and heighten infection risk.

Moderate Interactions (Monitor Closely)

• Anthelmintic drugs: consider prophylactic treatment for parasitic infections.
• Other biologics targeting eosinophils: combined use may increase adverse event risk.
• Systemic corticosteroids: dose adjustments may be needed based on clinical response.