The New England Journal of Medicine September 25, 2014

Mepolizumab Treatment in Patients with Severe Eosinophilic Asthma

Hector G. Ortega, Mark C. Liu, Ian D. Pavord et al.

Bottom Line

In patients with severe eosinophilic asthma, adjunctive mepolizumab (administered intravenously or subcutaneously) significantly reduced the rate of asthma exacerbations and improved lung function and asthma control.

Key Findings

1. Mepolizumab 100 mg subcutaneously reduced the rate of clinically significant asthma exacerbations by 53% compared to placebo (95% CI, 37-65; P<0.001).

2. Mepolizumab 75 mg intravenously reduced the rate of exacerbations by 47% compared to placebo (95% CI, 29-61; P<0.001).

3. Exacerbations necessitating emergency department visits or hospitalization were reduced by 61% in the subcutaneous group and 32% in the intravenous group.

4. At week 32, the mean increase from baseline in FEV1 was 98 mL greater with subcutaneous mepolizumab and 100 mL greater with intravenous mepolizumab than with placebo (P=0.03 and P=0.02, respectively).

5. St. George's Respiratory Questionnaire (SGRQ) scores improved by 7.0 points (subcutaneous) and 6.4 points (intravenous) over placebo, exceeding the minimal clinically important difference of 4 points.

Study Design

Design

RCT

Double-Blind

Sample

576

Patients

Duration

32 wk

Median

Setting

Multicenter, multinational

Population Patients aged 12-82 with severe asthma, recurrent exacerbations (≥2 in the previous year) despite high-dose inhaled glucocorticoids, and evidence of eosinophilic inflammation (blood eosinophils ≥150 cells/μL at screening or ≥300 cells/μL in the previous year).

Intervention Mepolizumab 75 mg intravenously (IV) or 100 mg subcutaneously (SC) every 4 weeks.

Comparator Placebo administered intravenously or subcutaneously every 4 weeks.

Outcome Frequency of clinically significant asthma exacerbations.

Study Limitations

• The 32-week study duration limits the ability to evaluate long-term safety, durability of response, and effects on airway remodeling.

• The trial was strictly limited to patients with distinct eosinophilic inflammation, meaning the findings cannot be generalized to non-eosinophilic severe asthma phenotypes.

• The strict adherence to therapy within a clinical trial setting may not accurately reflect real-world medication compliance.

Clinical Significance

The MENSA trial definitively established that targeting the interleukin-5 (IL-5) pathway with mepolizumab is highly efficacious in patients with severe, exacerbation-prone eosinophilic asthma. By demonstrating that a 100 mg subcutaneous dose is both safe and effective at cutting exacerbation rates in half while improving lung function and quality of life, this study formed the basis for the widespread regulatory approval and clinical adoption of subcutaneous mepolizumab as a standard biologic therapy for this specific asthma phenotype.

Historical Context

Prior to targeted biologic therapies, patients with severe eosinophilic asthma were largely dependent on high-dose inhaled or chronic systemic corticosteroids, which carry significant morbidity. Early trials of anti-IL-5 therapies yielded mixed results because they were unselected for the eosinophilic phenotype. Following the proof-of-concept DREAM trial (2012) which stratified patients by sputum or blood eosinophils, MENSA (alongside the steroid-sparing SIRIUS trial) was the pivotal Phase 3 study that validated peripheral blood eosinophils as a biomarker for anti-IL-5 responsiveness and cemented the modern phenotype-driven approach to severe asthma management.

Guided Discussion

High-yield insights from every perspective

Med Student

Medical Student

Mepolizumab targets IL-5 in severe eosinophilic asthma. What is the physiological role of IL-5 in the pathogenesis of this specific asthma phenotype, and why is targeted biologic therapy highly effective compared to escalating non-targeted treatments?

Key Response

IL-5 is the predominant cytokine responsible for the maturation, bone marrow release, recruitment, and survival of eosinophils. Students must understand Type 2 inflammatory pathways, recognizing that blocking IL-5 directly reduces eosinophilic airway inflammation with far fewer systemic side effects than broad immunosuppressants like oral corticosteroids.

Resident

When evaluating a patient with severe, uncontrolled asthma on high-dose ICS and a LABA, what specific clinical history features and biomarker thresholds are required to determine if they are an appropriate candidate for mepolizumab therapy based on the MENSA trial criteria?

Key Response

Residents need to master asthma phenotyping. Key criteria include a clinical history of frequent exacerbations despite maximal inhaler therapy and evidence of eosinophilic inflammation, specifically a peripheral blood eosinophil count greater than or equal to 150 cells per microliter at initiation or greater than or equal to 300 cells per microliter in the past year.

Fellow

The MENSA trial demonstrated comparable efficacy between intravenous and subcutaneous mepolizumab. How do you approach the clinical decision between anti-IL-5 agents (mepolizumab, reslizumab, benralizumab), anti-IgE (omalizumab), and anti-IL-4/13 (dupilumab) in a patient with overlapping allergic and eosinophilic asthma phenotypes?

Key Response

Fellows must navigate complex, overlapping phenotypes. Choosing among biologics requires integrating comorbidities like nasal polyps or atopic dermatitis, understanding receptor versus ligand targeting (e.g., benralizumab depletes via ADCC while mepolizumab binds circulating IL-5), and evaluating complex biomarker profiles including IgE, FeNO, and eosinophil trends.

Attending

While the MENSA trial demonstrated a significant reduction in exacerbations over 32 weeks, how does the integration of mepolizumab alter the long-term clinical trajectory of severe eosinophilic asthma, particularly regarding the ability to wean maintenance oral corticosteroids and prevent irreversible airway remodeling?

Key Response

Attendings focus on long-term disease modification. Reducing exacerbations prevents cumulative oral corticosteroid toxicity and may slow accelerated lung function decline, fundamentally shifting the severe asthma treatment paradigm from reactive symptom management to proactive disease modification and steroid-sparing strategies.

Scholarly Review

Critical appraisal through the lens of expert reviewers and guideline development

PhD

The MENSA trial utilized the rate of clinically significant asthma exacerbations as the primary endpoint, analyzed using a negative binomial regression model. What are the methodological advantages of this statistical approach over a time-to-first-exacerbation survival analysis for this specific patient population?

Key Response

Exacerbations in severe asthma are recurrent events, and count data is highly skewed and overdispersed. Negative binomial regression accounts for this unobserved heterogeneity between patients, providing a more accurate estimate of the overall exacerbation rate ratio compared to Cox proportional hazards, which ignores subsequent events after the first exacerbation.

Journal Editor

A critical reviewer of the MENSA trial might scrutinize the potential for unblinding due to the profound pharmacological effects of the drug. How robust is the blinding in a trial where routine complete blood counts reveal dramatic reductions in peripheral eosinophils, and how might this impact the interpretation of subjective secondary endpoints like the ACQ-5?

Key Response

Anti-IL-5 therapies rapidly deplete peripheral eosinophils. If investigators or patients view routine lab results, they could easily deduce the treatment assignment. This unblinding could introduce detection bias or placebo effects, disproportionately affecting subjective questionnaire scores compared to hard endpoints like hospitalizations.

Guideline Committee

Based on the MENSA trial data, how should clinical practice guidelines position mepolizumab within the GINA Step 5 treatment algorithm, specifically regarding its prioritization over maintenance systemic corticosteroids and the establishment of strict biomarker cutoffs for recommendation?

Key Response

Guideline committees must translate trial inclusion criteria into practice recommendations. Based on MENSA, GINA strongly recommends Type 2 biologics as preferred add-on therapies in Step 5 over maintenance OCS, strictly citing blood eosinophils greater than or equal to 150 to 300 cells per microliter as the crucial biomarker threshold for anti-IL-5 initiation.

Clinical Landscape

Noteworthy Related Trials

2012

DREAM Trial

n = 621 · Lancet

Tested

Mepolizumab 75mg, 250mg, or 750mg IV

Population

Patients with severe eosinophilic asthma

Comparator

Placebo

Endpoint

Rate of clinically significant asthma exacerbations

Key result: Mepolizumab significantly reduced the rate of clinically significant asthma exacerbations compared to placebo across all intravenous doses tested.

2014

SIRIUS Trial

n = 135 · NEJM

Tested

Mepolizumab 100mg SC every 4 weeks

Population

Patients with severe eosinophilic asthma dependent on oral glucocorticoids

Comparator

Placebo

Endpoint

Percentage reduction in oral glucocorticoid dose

Key result: Patients receiving mepolizumab achieved a significant 50 percent reduction in their maintenance oral glucocorticoid dose while simultaneously experiencing fewer exacerbations.

2016

SIROCCO Trial

n = 1,204 · Lancet

Tested

Benralizumab 30mg SC every 4 or 8 weeks

Population

Patients with severe uncontrolled asthma and elevated blood eosinophils

Comparator

Placebo

Endpoint

Annual asthma exacerbation rate

Key result: Benralizumab effectively reduced the annual exacerbation rate and improved lung function in patients with severe uncontrolled eosinophilic asthma.

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