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Biologic
UniProt P05113

Mepolizumab

Nucala
Mechanism of action
IL-5 ()
In plain language
A lab-made that locks onto IL-5, a signaling protein that tells the body to make and sustain eosinophils — an immune cell that, in excess, drives inflammation in conditions like severe asthma.
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How it works
Mepolizumab is a humanized IgG1 monoclonal antibody that binds circulating interleukin-5 with high affinity, preventing IL-5 from engaging the alpha subunit of its complex on the eosinophil surface. By blocking this -receptor interaction, mepolizumab interrupts a key survival and maturation signal for eosinophils, reducing their production in bone marrow and shortening their circulating lifespan, producing blood eosinophil reductions of roughly 79-92% within four weeks.
Therapeutic applications
FDA-indicated as add-on maintenance therapy for severe eosinophilic asthma in patients 6 and older, chronic rhinosinusitis with nasal polyps, and COPD with an eosinophilic phenotype. Also indicated as treatment for eosinophilic granulomatosis with polyangiitis and hypereosinophilic syndrome in patients 12 and older.
Class
Monoclonal antibody
Therapeutic area
Respiratory / Immunology
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