Mepolizumab

Introduction Overview

Generic Name

mepolizumab

Brand Name

Nucala

Dosage Form

single-dose prefilled autoinjector (100 mg/mL), single-dose prefilled syringe (100 mg/mL, 40 mg/0.4 mL), vial for subcutaneous injection (100 mg)

Drug Class

Interleukin inhibitors

Pharmacokinetics

Absorption:
Mepolizumab is administered via subcutaneous injection, and following administration, it is absorbed slowly and steadily into the systemic circulation. The bioavailability of subcutaneous administration is approximately 74%, reflecting efficient absorption. Peak plasma concentrations are typically observed within 4 to 8 days post-dose. The absorption rate can be influenced by factors such as local blood flow at the injection site, injection technique, and patient-specific variables. The slow absorption contributes to the drug's prolonged half-life and supports its once-every-4-weeks dosing schedule in clinical practice.

Distribution:
Upon entering the systemic circulation, mepolizumab exhibits a limited volume of distribution, indicative of its confinement primarily to the vascular and interstitial compartments. Being a monoclonal antibody, mepolizumab distributes mainly within the extracellular fluid with minimal penetration into intracellular spaces. Plasma protein binding is relatively low and nonspecific. The estimated volume of distribution is approximately 3.2 to 4.2 liters, consistent with other monoclonal antibodies. Distribution may be altered in patients with variations in body composition, but such effects are typically minimal and not clinically significant.

Metabolism:
Mepolizumab, like other therapeutic monoclonal antibodies, is metabolized through proteolytic catabolism throughout the reticuloendothelial system and target tissues. It undergoes degradation into smaller peptides and amino acids by ubiquitous proteases. Unlike small-molecule drugs, mepolizumab is not metabolized by cytochrome P450 enzymes, reducing the potential for classic drug-drug interactions involving hepatic metabolism. This protein catabolism is typically a non-saturable, linear process, contributing to predictable pharmacokinetics.

Elimination:
The elimination half-life of mepolizumab is approximately 16 to 22 days, supporting its monthly dosing regimen. Clearance occurs primarily via proteolytic enzymes present in the liver, spleen, and other tissues. Renal and hepatic impairments do not significantly affect the elimination of mepolizumab due to its metabolism as a protein therapeutic. The elimination is characterized by linear pharmacokinetics at therapeutic doses. The persistent presence in circulation aids sustained suppression of eosinophil-mediated inflammatory responses. No active metabolites are formed, and excretion pathways via urine or feces in intact form are negligible.

Dosage Forms

Available Dosage Forms:
Nucala is available in several dosage forms intended for subcutaneous injection: 1) Single-dose prefilled autoinjector containing 100 mg/mL of mepolizumab; 2) Single-dose prefilled syringes available in 100 mg/mL and 40 mg/0.4 mL strengths; 3) Lyophilized powder in single-dose vials requiring reconstitution to provide 100 mg per vial.

Dosages for Adults and Adolescents:
- Severe eosinophilic asthma: Adults and children aged 12 years and older receive 100 mg subcutaneously once every 4 weeks. Children aged 6 to 11 years receive 40 mg subcutaneously once every 4 weeks.
- Chronic Obstructive Pulmonary Disease (COPD) with eosinophilic phenotype: 100 mg subcutaneously once every 4 weeks for adults.
- Chronic rhinosinusitis with nasal polyps (CRSwNP): Adults aged 18 years and older are administered 100 mg subcutaneously once every 4 weeks.
- Eosinophilic granulomatosis with polyangiitis (EGPA): Adults receive 300 mg subcutaneously once every 4 weeks, administered as three separate 100 mg injections.
- Hypereosinophilic syndrome (HES): Adults and children aged 12 years and older receive 300 mg subcutaneously once every 4 weeks, given as three separate 100 mg injections.

Specific Patient Populations:
- Pediatric patients: Prefilled syringes can be used in children as young as 6 years for asthma treatment at 40 mg doses; autoinjectors are indicated for children 12 years and older.
- Nucala is not approved for use in patients under 6 years for asthma, under 12 years for HES, or under 18 years for COPD, EGPA and CRSwNP.
- Special instructions for administration include rotating injection sites between the thigh, abdomen, or upper arm, with caregiver or healthcare provider administration for pediatric populations or self-administration following appropriate training.
- Dose adjustments based on renal or hepatic impairment are not required due to the drug’s pharmacokinetic profile.

The availability of multiple dosage forms and strengths allows tailoring therapy to patient age, weight, and disease indication, facilitating optimized management of eosinophilic-driven diseases.

Mechanism Of Action

Nucala (mepolizumab) is a humanized monoclonal antibody that specifically binds to interleukin-5 (IL-5), a key cytokine involved in the growth, differentiation, recruitment, activation, and survival of eosinophils. By neutralizing IL-5, mepolizumab prevents its interaction with the IL-5 receptor alpha chain (IL-5Rα) present on the surface of eosinophils and their progenitor cells. This inhibition disrupts the IL-5 signaling cascade which normally promotes eosinophil maturation and prolonged survival, thus leading to a marked reduction in circulating and tissue eosinophil levels.

At the cellular level, the blockade of IL-5 prevents eosinophil-mediated inflammatory responses in various tissues including the lungs and nasal passages. Eosinophils contribute to airway inflammation, hyperresponsiveness, and remodeling characteristic of severe eosinophilic asthma and related conditions. By reducing eosinophil numbers and viability, Nucala helps mitigate these pathophysiological processes, leading to improved respiratory function, reduced exacerbation frequency, and amelioration of nasal polyposis symptoms.

Biochemically, mepolizumab belongs to the class of interleukin inhibitors and functions as a biologic therapeutic. It binds IL-5 with high affinity and specificity, resulting in a direct neutralization without eliciting antibody-dependent cellular cytotoxicity (ADCC) or complement activation, which aligns with its favorable safety profile. This mechanistic distinction differentiates it from other immunomodulatory agents. Clinical studies support that suppression of IL-5 activity correlates strongly with clinical benefits, emphasizing the pivotal role of eosinophils in the disease pathology.

Comparatively, other anti-IL-5 agents such as reslizumab and benralizumab target different aspects of the eosinophil life cycle or receptor, but all converge on reducing eosinophil inflammation. Mepolizumab’s targeted mechanism and dosing regimen provide a sustained therapeutic effect and have been validated across multiple eosinophilic disorders in rigorous clinical trials. This precision in targeting underpins its approval for multiple eosinophil-related indications, including severe asthma, EGPA, nasal polyps, and hypereosinophilic syndromes.

Pharmacological Actions

Selective inhibition of interleukin-5 (IL-5) mediated eosinophil activation and survival
Reduction of circulating and tissue eosinophil counts, leading to decreased eosinophilic inflammation
Suppression of eosinophil-driven airway inflammation contributing to improved lung function in severe eosinophilic asthma
Amelioration of chronic rhinosinusitis with nasal polyps symptoms by decreasing eosinophilic infiltration
Immune-modulatory action without broad immunosuppression, maintaining overall host defense
Decreased frequency of exacerbations in eosinophilic asthma and COPD phenotypes
Reduction of vascular inflammation in eosinophilic granulomatosis with polyangiitis (EGPA)
Management of hypereosinophilic syndrome (HES) via eosinophil depletion to prevent organ damage
Monoclonal antibody biologic therapy with high specificity and affinity to IL-5 cytokine
No significant cytochrome P450-mediated metabolism, minimizing pharmacokinetic drug interactions
Biweekly to monthly dosing maintains steady-state eosinophil control with good patient adherence
Minimal impact on other leukocyte populations, preserving broad immune function

Therapeutic Or Clinical Uses

Add-on maintenance treatment for severe eosinophilic asthma in adults and children 6 years and older
Management of inadequately controlled eosinophilic phenotype chronic obstructive pulmonary disease (COPD) in adults
Treatment of chronic rhinosinusitis with nasal polyps (CRSwNP) in adults insufficiently responsive to nasal corticosteroids
Therapeutic option for eosinophilic granulomatosis with polyangiitis (EGPA) in adult patients
Used for hypereosinophilic syndrome (HES) in adults and children 12 years and older with disease duration of 6 months or longer
Reduction of exacerbations and improvement of quality of life in eosinophil-driven respiratory diseases
Adjunct therapy to oral or inhaled corticosteroids in eosinophilic asthma management
Helps prevent the need for surgical intervention in nasal polyposis by reducing polyp size and symptoms
Improves nasal congestion, discharge, mucus throat symptoms, and olfactory function in CRSwNP
Clinical use facilitated by patient self-administration options to improve treatment adherence
Reduces dependence on systemic corticosteroids in chronic eosinophilic disorders
Indicated for patients with an eosinophilic phenotype demonstrated by elevated eosinophil counts
Not intended for acute bronchospasm or relief of acute asthma attacks
Considered as a treatment milestone in severe persistent eosinophilic inflammatory diseases

Side Or Adverse Effects

Common: headache
Common: fatigue (feeling tired)
Common: mouth or throat pain
Common: back pain and joint pain
Injection site reactions including pain, swelling, redness, burning, or itching
Potential for serious allergic hypersensitivity reactions including anaphylaxis
Rare herpes zoster (shingles) infections possibly triggered post-treatment
Occasional upper respiratory tract infections and nasopharyngitis
Possible fever and flu-like symptoms following injection in some patients
Uncommon hypersensitivity symptoms such as rash, urticaria, and pruritus
No significant reports of weight gain linked directly to mepolizumab usage
Rare cases of eosinophil-associated adverse events such as eosinophilic pneumonia reported
Injection site granulomas or delayed local hypersensitivity reactions reported infrequently
Lack of systemic immunosuppression reduces risk of opportunistic infections
Post-marketing surveillance continues to monitor for long-term adverse event profiles

Precautions

Patients should be evaluated for hypersensitivity to mepolizumab or any component prior to therapy initiation
Use cautiously in patients with active or chronic infections, especially helminthic (worm) infections
Monitor patients for signs of allergic reactions or anaphylaxis during and after injection
Assess vaccination status; consider administration of zoster vaccine prior to therapy initiation
Do not discontinue oral or inhaled corticosteroids abruptly upon initiation of Nucala
Pregnant or breastfeeding women should weigh potential benefits against unknown risks; consultation with healthcare provider required
Use in pediatric patients under approved age limits is not recommended due to lack of safety data
Patients with a history of herpes zoster infections should be monitored carefully
Ensure patients understand proper self-administration techniques to reduce injection site complications
Avoid use in patients with hypersensitivity to murine proteins or monoclonal antibodies
Careful monitoring in patients with comorbid immunological disorders or on concomitant immunosuppressive therapy
Report any adverse reactions promptly to healthcare providers
Store medication per guidelines to maintain efficacy and reduce contamination risk
Patients should be advised on the signs of infection and immediately report any unusual symptoms
Regular follow-up is recommended to assess treatment response and adverse effects

Warnings

Risk of serious allergic (hypersensitivity) reactions including anaphylaxis which may occur hours to days post-injection
Potential for herpes zoster infections; patients should seek medical attention if symptoms develop
Not a rescue medicine; should not be used for acute asthma exacerbations or status asthmaticus
Do not abruptly discontinue corticosteroids when starting Nucala to avoid adrenal insufficiency
Use caution in patients with underlying parasitic infections, as eosinophil suppression may worsen conditions
Injection site reactions may range from mild irritation to severe localized hypersensitivity
Long-term safety in pediatric patients below specified age thresholds is not established
Patients should be instructed not to use more than one dose at a time or deviate from prescribed dosing intervals
Potential immunogenicity with formation of anti-drug antibodies may alter efficacy and safety
Ensure appropriate storage conditions to prevent loss of potency or contamination
Discontinue use if serious hypersensitivity or immune reactions occur
Potential for rare immune-mediated systemic reactions requiring prompt medical intervention
Risk-benefit assessment recommended before use in pregnant or nursing mothers due to insufficient data
Patients with active or latent infections should be carefully monitored during therapy
Concomitant use with other immunomodulators should be approached cautiously due to additive immunosuppression

Contraindication

Known hypersensitivity to mepolizumab, Nucala formulation components, or monoclonal antibodies
Patients with a history of severe allergic reactions to any ingredient in the injection preparation
Not recommended for use in children under 6 years for asthma or under 12 years for hypereosinophilic syndrome
Not approved for treatment of chronic rhinosinusitis with nasal polyps (CRSwNP), eosinophilic granulomatosis with polyangiitis (EGPA), or COPD in children and adolescents under 18
Active parasitic infections where eosinophil suppression could lead to clinical worsening
Patients requiring immediate relief of acute bronchospasm or status asthmaticus should not receive Nucala
Presence of immune hypersensitivity disorders contraindicating monoclonal antibody therapy
Known intolerance or allergy to polysorbate 80 or other excipients contained in the formulation
Concurrent use with other biologics targeting IL-5 or IL-5 receptor not recommended outside clinical trials
Severe infections or immunodeficiency states where further immune modulation is hazardous
Pregnancy or lactation without careful risk assessment by healthcare provider
History of anti-mepolizumab antibody with clinical hypersensitivity symptoms
Use when alternative eosinophil-suppressing therapies are contraindicated or unavailable
Patients with acute systemic illness or fever until resolution

Drug Interactions

No formal drug interaction studies conducted; however, no clinically significant interactions expected with cytochrome P450 substrates due to protein metabolism
Potential pharmacodynamic interactions when co-administered with oral or inhaled corticosteroids; patients should not abruptly discontinue corticosteroids to avoid adrenal insufficiency
Combination with other immunomodulatory therapies may increase risk of immunosuppression
Concomitant vaccinations: live vaccines should be avoided during treatment due to immunomodulatory effects
No known interactions with commonly used respiratory medications such as beta-agonists or anticholinergics
No significant alteration of pharmacokinetics when combined with other biologics targeting eosinophils or type 2 inflammation (data limited)
Herbal supplements and over-the-counter drugs have not shown interactions but should be reported to healthcare providers
No known interactions affecting absorption, distribution, metabolism, or elimination of mepolizumab
Minimal risk of drug interactions given monoclonal antibody nature and proteolytic metabolism
Patients should inform healthcare providers about all medications including vaccinations, antibiotics, and steroids
Potential additive immunosuppressive effects when used with other biologics requires clinical monitoring
Interaction with helminthic infection treatments should be monitored given interaction with immune response
Limited data available regarding interactions with small-molecule immunosuppressants such as methotrexate
Concurrent use with other IL-5 pathway inhibitors is not recommended due to overlapping mechanisms
No evidence indicates interactions with drugs commonly used for comorbid cardiovascular or metabolic diseases

Preparations Of The Drug

Single-dose prefilled autoinjector containing 100 mg/mL mepolizumab for subcutaneous injection
Single-dose prefilled syringes available in two strengths: 100 mg/mL and 40 mg/0.4 mL
Lyophilized powder in single-dose vials for reconstitution providing 100 mg per vial for subcutaneous use
All preparations intended for once-monthly administration via subcutaneous injection
Inactive ingredients in vials include polysorbate 80, sodium phosphate dibasic heptahydrate, and sucrose
Prefilled autoinjectors and syringes contain citric acid monohydrate, EDTA disodium dihydrate, polysorbate 80, sodium phosphate dibasic heptahydrate, and sucrose as excipients
Prefilled syringes and autoinjectors are designed for single use; any unused portion must be discarded
Storage recommendations include refrigeration at 2°C to 8°C, protected from light and avoiding freezing or shaking
Prefilled syringes and autoinjectors may be kept at room temperature up to 7 days before use
Vials require reconstitution with sterile water prior to administration according to prescribing information
All forms are packaged with sterile, disposable needles suitable for subcutaneous injection
Instructions for use included with each preparation to guide self-administration and caregiver administration
Special packaging designed to maintain drug stability throughout shelf-life and transit conditions
Manufactured by GlaxoSmithKline (GSK), a multinational pharmaceutical company
Available only by prescription with no generic or biosimilar alternatives currently approved