Mepolizumab is a fully-humanized monoclonal IgG1 kappa anti-IL-5 antibody used in conjunction with other therapies to treat severe asthma, eosinophilic granulomatosis with polyangiitis, and hypereosinophilic syndrome.

Brand Names
Generic Name
DrugBank Accession Number

Eosinophils are involved in inflammatory immune responses, and prolonged hypereosinophilia (typically defined as absolute eosinophil levels of 1500/mm3 or more) is associated with a spectrum of diseases, including severe asthma, eosinophilic granulomatosis with polyangiitis (EGPA), and hypereosinophilic syndrome (HES). The pathogenesis of eosinophilia is complex, but IL-5 is recognized as a key cytokine involved in the differentiation, recruitment, activation, and prolonged survival of eosinophils in peripheral tissue. Activated eosinophils further stimulate an inflammatory response and also induce tissue lesions and promote fibrosis, all of which contribute to the multifactorial symptomatology of hypereosinophilic diseases.1,2,3,4,5,6

Mepolizumab is a fully-humanized recombinant IgG1 kappa monoclonal antibody directed against IL-5 produced in Chinese hamster ovary cells. Mepolizumab was first approved by the FDA on November 4, 2015, as an add-on therapy for severe asthma and marketed under the brand name Nucala by GlaxoSmithKline. This indication was subsequently expanded to cover EGPA on December 12, 2017, and HES on September 25, 2020.6

Approved, Investigational
Biologic Classification
Protein Based Therapies
Monoclonal antibody (mAb)
Protein Structure
Protein Chemical Formula
Not Available
Protein Average Weight
149000.0 Da
Not Available
  • Mepolizumab
External IDs
  • SB 240563
  • SB-240563



Mepolizumab is an anti-IL-5 IgG1 kappa monoclonal antibody indicated as an add-on maintenance treatment in patients aged six years and older with severe eosinophilic asthma and as a treatment in adult patients for eosinophilic granulomatosis with polyangiitis (EGPA). Mepolizumab is also indicated for the treatment of hypereosinophilic syndrome (HES) in patients aged 12 and older in whom eosinophilia is present for at least six months without an identifiable non-hematologic secondary cause.6

Mepolizumab is additionally indicated as an add-on maintenance treatment of chronic rhinosinusitis with nasal polyps (CRSwNP) in patients ≥18 years old with inadequate response to nasal corticosteroids.6

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Associated Conditions
Indication TypeIndicationCombined Product DetailsApproval LevelAge GroupPatient CharacteristicsDose Form
Adjunct therapy in management ofChronic rhinosinusitis phenotype with nasal polyps (crswnp)••••••••••••••••••••••••••• •••••••• •• ••••• ••••••••••••••••••••••••
Treatment ofEosinophilic granulomatosis with polyangiitis••••••••••••••••••••••••••
Treatment ofHypereosinophilic syndromes••••••••••••••••••••••••••••• ••••••• •• ••••• ••• ••••••• •• •••••••••••• ••••••••••••••• ••••••••• ••••••••••••••
Adjunct therapy in management ofSevere eosinophilic asthma•••••••••••••••••••••
Contraindications & Blackbox Warnings
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Mepolizumab is a monoclonal antibody that acts through interleukin-5 (IL-5) antagonism to reduce blood eosinophil levels, generally in the range of 60-90% of baseline depending on dose, which in turn offers therapeutic benefit in the specific conditions for which mepolizumab is indicated. Mepolizumab has a relatively long half-life of between 16 and 22 days, which allows for long-lasting therapeutic benefit and a four-week dosing schedule. Despite a good demonstrated safety profile, mepolizumab use does act to depress part of the immune system and may be associated with increased infections, such as with herpes zoster virus; pre-existing helminth infections should be treated before starting mepolizumab therapy. Inhaled and oral corticosteroids should not be discontinued after starting mepolizumab but may be tapered as appropriate. Mepolizumab should not be used to treat acute bronchospasms or status asthmatics. Finally, hypersensitivity reactions, including anaphylaxis, have been reported in patients; mepolizumab should be discontinued in patients with suspected or confirmed hypersensitivity.6

Mechanism of action

Hypereosinophilia is typically considered as an absolute eosinophil count of 1500/mm3 or higher and is associated with aberrant immune responses in several conditions, including severe asthma, eosinophilic granulomatosis with polyangiitis, and the variable spectrum of hypereosinophilic syndrome (HES).1,2 Eosinophils are involved in the inflammatory response by secretion of molecules such as MBP, leukotrienes, matrix metalloproteinases, transforming growth factor-β, nitric oxide, and other reactive oxygen species.3,4 Interleukin-5 (IL-5) is the primary cytokine associated with the differentiation of bone marrow progenitor cells into mature inflammatory neutrophils and the subsequent migration, activation, and prolonged survival of activated neutrophils. In concert with other cells, including lymphocytes, neutrophils, mast cells, and macrophages, which themselves can secrete additional pro-inflammatory molecules, high concentrations of neutrophils are associated with tissue damage and fibrosis, leading to the symptoms of eosinophilic diseases.1,2,3,4,5

Typically, eosinophils arise from both CD34+ and dual CD34+, IL-5 receptor-positive (IL-5R+) progenitor cells, which is in part mediated by the cytokines IL-5, IL-3, and granulocyte-macrophage colony-stimulating factor (GM-CSF).4 Although there exists a population of eosinophils that are insensitive to IL-5 levels, the main population of inflammatory eosinophils proliferates and migrates into the tissue in response to IL-5.4 Mepolizumab is a fully-humanized monoclonal IgG1 kappa antibody that binds IL-5 with a dissociation constant of 100 pM, preventing IL-5 from binding to and subsequently activating IL-5R+ cells.6 This reduction lowers circulating blood eosinophil levels and therefore exerts a beneficial effect in eosinophilic disease; the exact mechanistic nature of mepolizumab action has not been definitively determined.1,2,3,4,5,6 Not all patients will benefit from mepolizumab treatment, such as those with milder asthma or those with a sub-type of HES that is independent of IL-5 signalling.1,4


Mepolizumab is administered subcutaneously and has a bioavailability of approximately 80% based on a 100 mg dose given to both adult and adolescent subjects with asthma. With the recommended four-week dosing schedule, there is an approximately two-fold accumulation of mepolizumab at steady-state.6

Volume of distribution

Mepolizumab has a population central volume of distribution of 3.6 L (for a 70 kg individual) in adult asthma patients.6

Protein binding

Not Available


As a monoclonal antibody, mepolizumab is subject to proteolytic degradation at sites distributed throughout the body.6

Route of elimination

Not Available


Mepolizumab has a mean terminal half-life of between 16 and 22 days.6


Mepolizumab has an estimated apparent population systemic clearance of 0.28 L/day (for a 70-kg individual) in adult and adolescent subjects.6

Adverse Effects
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Toxicity information regarding mepolizumab is not readily available. Patients experiencing an overdose are at an increased risk of severe adverse effects such as newly established or worsening chronic infections, including those caused by helminths, and generalized immune depression. Symptomatic and supportive measures are recommended.6

Not Available
Pharmacogenomic Effects/ADRs
Not Available


Drug Interactions
This information should not be interpreted without the help of a healthcare provider. If you believe you are experiencing an interaction, contact a healthcare provider immediately. The absence of an interaction does not necessarily mean no interactions exist.
AbataceptThe risk or severity of adverse effects can be increased when Abatacept is combined with Mepolizumab.
AbciximabThe risk or severity of adverse effects can be increased when Abciximab is combined with Mepolizumab.
AdalimumabThe risk or severity of adverse effects can be increased when Adalimumab is combined with Mepolizumab.
Adenovirus type 7 vaccine liveThe risk or severity of infection can be increased when Adenovirus type 7 vaccine live is combined with Mepolizumab.
AducanumabThe risk or severity of adverse effects can be increased when Mepolizumab is combined with Aducanumab.
Food Interactions
No interactions found.


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International/Other Brands
Bosatria (GlaxoSmithKline)
Brand Name Prescription Products
NameDosageStrengthRouteLabellerMarketing StartMarketing EndRegionImage
NucalaInjection, solution100 mgSubcutaneousGlaxo Smith Kline Trading Services2022-05-04Not applicableEU flag
NucalaInjection, solution100 mgSubcutaneousGlaxo Smith Kline Trading Services2020-12-16Not applicableEU flag
NucalaInjection, solution100 mgSubcutaneousGlaxo Smith Kline Trading Services2020-12-16Not applicableEU flag
NucalaSolution40 mg / 0.4 mLSubcutaneousGlaxosmithkline Inc2023-02-13Not applicableCanada flag
NucalaSolution100 mg / mLSubcutaneousGlaxosmithkline Inc2019-12-10Not applicableCanada flag


ATC Codes
R03DX09 — Mepolizumab
Drug Categories
Chemical TaxonomyProvided by Classyfire
Not Available
Organic Compounds
Super Class
Organic Acids
Carboxylic Acids and Derivatives
Sub Class
Amino Acids, Peptides, and Analogues
Direct Parent
Alternative Parents
Not Available
Not Available
Molecular Framework
Not Available
External Descriptors
Not Available
Affected organisms
  • Humans and other mammals

Chemical Identifiers

CAS number


Synthesis Reference

Robert S. Ames, Edward Robert Appelbaum, Irwin M. Chaiken, Richard M. Cook, Mitchell Stuart Gross, Stephen Dudley Holmes, Lynette Jane McMillan, Timothy Wayne Theisen, "Recombinant il-5 antagonists useful in treatment of il-5 mediated disorders." Patent WO1996021000A2, issued July 11, 1996.

General References
  1. Kuang FL, Fay MP, Ware J, Wetzler L, Holland-Thomas N, Brown T, Ortega H, Steinfeld J, Khoury P, Klion AD: Long-Term Clinical Outcomes of High-Dose Mepolizumab Treatment for Hypereosinophilic Syndrome. J Allergy Clin Immunol Pract. 2018 Sep - Oct;6(5):1518-1527.e5. doi: 10.1016/j.jaip.2018.04.033. Epub 2018 May 8. [Article]
  2. Curtis C, Ogbogu P: Hypereosinophilic Syndrome. Clin Rev Allergy Immunol. 2016 Apr;50(2):240-51. doi: 10.1007/s12016-015-8506-7. [Article]
  3. Caminati M, Menzella F, Guidolin L, Senna G: Targeting eosinophils: severe asthma and beyond. Drugs Context. 2019 Jul 23;8:212587. doi: 10.7573/dic.212587. eCollection 2019. [Article]
  4. Bakakos A, Loukides S, Bakakos P: Severe Eosinophilic Asthma. J Clin Med. 2019 Sep 2;8(9). pii: jcm8091375. doi: 10.3390/jcm8091375. [Article]
  5. Rothenberg ME, Klion AD, Roufosse FE, Kahn JE, Weller PF, Simon HU, Schwartz LB, Rosenwasser LJ, Ring J, Griffin EF, Haig AE, Frewer PI, Parkin JM, Gleich GJ: Treatment of patients with the hypereosinophilic syndrome with mepolizumab. N Engl J Med. 2008 Mar 20;358(12):1215-28. doi: 10.1056/NEJMoa070812. Epub 2008 Mar 16. [Article]
  6. FDA Approved Drug Products: Nucala (mepolizumab) for subcutaneous injection [Link]
  7. GlaxoSmithKline: NUCALA safety data sheet [Link]
PubChem Substance
1720597 Drug Page
FDA label
Download (3.56 MB)
Download (86.4 KB)

Clinical Trials

Clinical Trials
4Not Yet RecruitingBasic ScienceChronic Rhinosinusitis Phenotype With Nasal Polyps (CRSwNP)1
4Not Yet RecruitingOtherAsthma1
4Not Yet RecruitingTreatmentChronic Sinusitis / Nasal Polyps1


Not Available
Not Available
Dosage Forms
InjectionSubcutaneous100 mg
Injection, powder, for solutionSubcutaneous100 mg/1mL
Injection, powder, for solutionSubcutaneous100 MG
Injection, solutionParenteral; Subcutaneous100 MG
Injection, solutionParenteral; Subcutaneous40 mg
Injection, solutionSubcutaneous100 mg
Injection, solutionSubcutaneous100 mg/1mL
Injection, solutionSubcutaneous40 mg/0.4mL
Injection, solutionSubcutaneous40 mg
Powder, for solutionSubcutaneous100 mg / vial
SolutionSubcutaneous100 mg / mL
SolutionSubcutaneous40 mg / 0.4 mL
SolutionSubcutaneous40.000 mg
Injection, powder, for solutionSubcutaneous
Injection, powder, lyophilized, for solutionSubcutaneous100 mg
Injection, solutionSubcutaneous100 mg/ml
SolutionSubcutaneous100 mg
Injection, powder, for solutionSubcutaneous100 mg/1vial
Not Available
Patent NumberPediatric ExtensionApprovedExpires (estimated)Region
US20100086547No2007-04-302027-04-30US flag


Experimental Properties
Not Available


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Pharmacological action
General Function
Interleukin-5 receptor binding
Specific Function
Factor that induces terminal differentiation of late-developing B-cells to immunoglobulin secreting cells.
Gene Name
Uniprot ID
Uniprot Name
Molecular Weight
15237.695 Da
  1. Basavaraju KP, Wong T: Eosinophilic oesophagitis: a common cause of dysphagia in young adults? Int J Clin Pract. 2008 Jul;62(7):1096-107. doi: 10.1111/j.1742-1241.2008.01782.x. [Article]
  2. Garrett JK, Jameson SC, Thomson B, Collins MH, Wagoner LE, Freese DK, Beck LA, Boyce JA, Filipovich AH, Villanueva JM, Sutton SA, Assa'ad AH, Rothenberg ME: Anti-interleukin-5 (mepolizumab) therapy for hypereosinophilic syndromes. J Allergy Clin Immunol. 2004 Jan;113(1):115-9. Epub 2003 Dec 12. [Article]
  3. Agarwal A, Spath D, Sherris DA, Kita H, Ponikau JU: Therapeutic Antibodies for Nasal Polyposis Treatment: Where Are We Headed? Clin Rev Allergy Immunol. 2020 Oct;59(2):141-149. doi: 10.1007/s12016-019-08734-z. [Article]
  4. FDA Approved Drug Products: Nucala (mepolizumab) for subcutaneous injection [Link]

Drug created at March 19, 2008 16:41 / Updated at June 03, 2022 07:24