Mepolizumab

Overview

Mepolizumab, sold under the brand name Nucala, is a humanized monoclonal antibody used for the treatment of severe eosinophilic asthma, chronic obstructive pulmonary disease (COPD) of an eosinophilic phenotype, eosinophilic granulomatosis with polyangiitis, and hypereosinophilic syndrome.[1] WP

The most common side effects include headache, injection site reactions, and back pain.[2] WP

Uses, dosage and effects

Medical uses

Mepolizumab is approved by the US Food and Drug Administration (FDA) for the maintenance treatment of severe asthma in patients aged six years or older and with an eosinophilic phenotype in combination with other medicines used to treat asthma. In the European Union it is approved as an add-on treatment for severe refractory eosinophilic asthma in adults.[2–5] WP

In studies, mepolizumab cut the necessity for hospitalisation due to asthma exacerbations in half, as compared to placebo.[6] WP

In December 2017, the FDA expanded mepolizumab's indication to treat adults with eosinophilic granulomatosis with polyangiitis, which is a rare autoimmune condition that can cause vasculitis.[7] WP

In September 2020, the FDA expanded mepolizumab's indication to treat adults and children aged twelve years and older with hypereosinophilic syndrome for six months or longer without another identifiable non-blood related cause of the disease.[1] WP

In May 2025, the FDA approved mepolizumab as an add-on therapy for people with chronic obstructive pulmonary disease who exhibit an eosinophilic phenotype.[8] WP

Risks and side effects

Side effects

Common side effects in clinical trials included headache (19% of patients under mepolizumab treatment versus 18% under placebo), injection site reactions (8% versus 3%), infections of the urinary tract (3% versus 2%) and the lower respiratory tract, eczema and muscle spasms (both 3% versus <1%).[9][10] WP

The most common side effects in people with hypereosinophilic syndrome include: upper respiratory tract infection and pain in extremities (such as the hands, legs and feet).[1] WP

Overdose

Single doses of 15 times the usual therapeutic dose have been tolerated in studies without significant side effects.[9][10] WP

Interactions

Interactions

No interaction studies have been conducted. The interaction potential is considered to be low.[9] WP

Pharmacology

Mechanism of action

Mepolizumab binds to IL-5 and prevents it from binding to its receptor, more specifically the interleukin 5 receptor alpha subunit, on the surface of eosinophil white blood cells. While eosinophils play a role in inflammation associated with asthma, the exact mechanism of mepolizumab is unknown.[10] WP

Pharmacokinetics

After subcutaneous injection, mepolizumab has an estimated bioavailability of 80% and reaches highest blood plasma concentrations after four to eight days. Like other antibodies, it is degraded by proteolytic enzymes. Its biological half-life is 20 days on average, ranging from 16 to 22 days in different individuals.[9][10] WP

History

History

Phase III clinical trials in severe eosinophilic asthma were completed in 2014.[11] WP

Mepolizumab was evaluated in a randomized, double-blind, multicenter, placebo-controlled trial in 108 participants with hypereosinophilic syndrome. In the study, participants were randomly assigned to receive mepolizumab or placebo by injection every four weeks. The trial compared the proportion of subjects who experienced a hypereosinophilic syndrome flare during the 32-week treatment period. A hypereosinophilic syndrome flare was defined as worsening of clinical signs and symptoms of hypereosinophilic syndrome or increasing eosinophils (disease-fighting white blood cells) on at least two occasions. The trial compared the proportions of participants with at least one flare over a 32-week treatment period, as well as the time to the first flare. Fewer participants in the mepolizumab treatment group (28%) had hypereosinophilic syndrome flares compared to participants in the placebo group (56%), with a 50% relative reduction. In addition, the time to the first hypereosinophilic syndrome flare was later, on average, for participants treated with mepolizumab versus placebo.[1] WP

Legal status

Legal status

In November 2015, the US Food and Drug Administration (FDA) approved mepolizumab for severe asthma, and in December 2015 mepolizumab was authorized for medical use in the European Union.[2][11] WP

In September 2020, mepolizumab was approved in the United States to treat adults and children aged twelve years of age and older with hypereosinophilic syndrome for six months or longer without another identifiable non-blood related cause of the disease.[1] WP

In January 2024, mepolizumab was approved in China for use in severe asthma with an eosinophilic phenotype.[12] WP

In May 2025, the FDA approved mepolizumab as an add-on therapy for people with chronic obstructive pulmonary disease who exhibit an eosinophilic phenotype.[13] WP

Chemistry

Harm reduction information

No harm reduction data is on file for this compound yet. That means no dose, timing or combination data from PsychonautWiki or TripSit. Please don't guess a dose from similar compounds. If you have taken it and feel unwell, contact emergency services or a poison control center.

User reports

Pop culture

No references added yet.

Sources

1. Journal / agency FDA Approves First Drug to Treat Group of Rare Blood Disorders in Nearly 14 Years. 25 September 2020
2. Journal / agency Nucala EPAR. 17 September 2018
3. Journal / agency FDA approves severe eosinophilic asthma treatment for children ages 6-11. AAP News. 30 January 2020
4. Journal / agency Bermejo I, Stevenson M, Cooper K, Harnan S, Hamilton J, Clowes M, Carroll C, Harrison T, Saha S. Mepolizumab for Treating Severe Eosinophilic Asthma: An Evidence Review Group Perspective of a NICE Single Technology Appraisal. PharmacoEconomics. February 2018. doi:10.1007/s40273-017-0571-8 · PMID 28933002
5. Journal / agency Nucala EPAR Summary for the public. December 2015
6. Journal / agency Yancey SW, Ortega HG, Keene ON, Mayer B, Gunsoy NB, Brightling CE, Bleecker ER, Haldar P, Pavord ID. Meta-analysis of asthma-related hospitalization in mepolizumab studies of severe eosinophilic asthma. The Journal of Allergy and Clinical Immunology. April 2017. doi:10.1016/j.jaci.2016.08.008 · PMID 27726946
7. Journal / agency FDA approves first drug for Eosinophilic Granulomatosis with Polyangiitis, a rare disease formerly known as the Churg–Strauss Syndrome
8. Other FDA: Mepolizumab Approved as Add-On Treatment for Chronic Obstructive Pulmonary Disease
9. Journal / agency Nucala Summary of Product Characteristics. December 2015
10. Other for Nucala drugs.com pro nucala
11. Journal / agency FDA approves Nucala to treat severe asthma. 4 November 2016
12. Other Rani, Archana. GSK's Nucala for severe eosinophilic asthma approved in China. 11 January 2024
13. Other Mepolizumab Reduces Exacerbation Risk, Healthcare Resource Utilization in COPD. 21 May 2025

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