New England Journal of Medicine September 25, 2014

Oral Glucocorticoid-Sparing Effect of Mepolizumab in Eosinophilic Asthma

Elisabeth H. Bel, Sally E. Wenzel, Philip J. Thompson, Charlene M. Prazma, Oliver N. Keene, Steven W. Yancey, Hector G. Ortega, Ian D. Pavord; for the SIRIUS Investigators

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Bottom Line

In patients with severe eosinophilic asthma, mepolizumab significantly reduced the required daily dose of oral glucocorticoids while simultaneously decreasing asthma exacerbations and improving symptom control.

Key Findings

1. The likelihood of achieving a reduction in the oral glucocorticoid-dose stratum was 2.39 times greater in the mepolizumab group than in the placebo group (OR 2.39; 95% CI, 1.25 to 4.56; P=0.008).

2. The median percentage reduction from baseline in the daily glucocorticoid dose was 50% in the mepolizumab group compared with 0% in the placebo group (P=0.007).

3. Despite receiving a reduced oral glucocorticoid dose, mepolizumab-treated patients had a 32% relative reduction in the annualized rate of asthma exacerbations (1.44 vs. 2.12 exacerbations per year; P=0.04).

4. Asthma symptoms significantly improved in the mepolizumab group, with a 0.52-point reduction on the Asthma Control Questionnaire 5 (ACQ-5) compared to placebo (P=0.004).

5. Over half (54%) of the patients receiving mepolizumab achieved at least a 50% reduction in their daily oral glucocorticoid dose, and 14% were able to completely discontinue oral glucocorticoids (compared to 8% in the placebo group).

Study Design

Design

Randomized Controlled Trial

Double-Blind

Sample

135

Patients

Duration

24 wk

Median

Setting

Multinational

Population Patients aged 12 to 74 years with severe eosinophilic asthma requiring daily oral glucocorticoid therapy (5 to 35 mg of prednisone equivalent) for at least 6 months.

Intervention Mepolizumab 100 mg administered subcutaneously every 4 weeks.

Comparator Matched placebo administered subcutaneously every 4 weeks.

Outcome Degree of reduction in the daily oral glucocorticoid dose (assessed in defined strata) during weeks 20 to 24 while maintaining asthma control.

Study Limitations

• The study duration of 24 weeks was relatively short, limiting conclusions about long-term steroid-sparing maintenance and the long-term resolution of corticosteroid-induced adverse effects.

• The small sample size (N=135) limited the statistical power to detect rare adverse events or deeply analyze specific subpopulations.

• The determination of asthma control during the dose-titration phase relied partially on patient-reported symptoms and investigator judgment, introducing potential subjectivity.

Clinical Significance

The SIRIUS trial represented a major paradigm shift in severe asthma management by proving that targeted anti-IL-5 biologic therapy (mepolizumab) safely reduces the reliance on systemic oral corticosteroids. This addresses a critical clinical challenge, as long-term oral corticosteroid use is associated with profound morbidity (e.g., osteoporosis, diabetes, weight gain, immunosuppression), formally establishing biologics as a standard strategy to minimize systemic toxicity in steroid-dependent severe eosinophilic asthma.

Historical Context

Prior to the advent of anti-IL-5 biologics, the only effective option for patients with severe, treatment-refractory asthma was chronic systemic corticosteroid therapy, carrying immense long-term toxicity. Early trials of mepolizumab in unselected asthmatic populations failed to show significant benefit. However, when investigators began targeting specific endotypes—patients with demonstrable eosinophilic airway inflammation—the profound efficacy of IL-5 inhibition became clear. The SIRIUS trial, published concurrently with the MENSA trial in 2014, was the pivotal study that specifically demonstrated mepolizumab's systemic steroid-sparing capability.

Guided Discussion

High-yield insights from every perspective

Med Student

Medical Student

Mepolizumab targets IL-5 in severe eosinophilic asthma. What is the normal physiological role of IL-5 in the immune system, and why does blocking it allow for the reduction of oral glucocorticoids in this specific subset of asthma patients?

Key Response

IL-5 is the primary cytokine responsible for eosinophil differentiation, activation, and survival in Th2-driven inflammation. By specifically targeting this pathway, mepolizumab selectively reduces eosinophilic airway inflammation, a primary driver of exacerbations in this phenotype, thereby removing the need for broad-spectrum immunosuppression with oral glucocorticoids.

Resident

A patient with severe asthma currently dependent on 10 mg of daily prednisone is considering mepolizumab therapy. What specific biomarkers and clinical criteria must be evaluated to determine if this patient is an appropriate candidate for mepolizumab according to the SIRIUS trial inclusion criteria?

Key Response

Candidates need an eosinophilic phenotype, indicated by a peripheral blood eosinophil count of at least 150 cells per microliter at initiation or at least 300 cells per microliter in the past year, alongside a history of OCS dependence or severe exacerbations despite high-dose ICS/LABA therapy.

Fellow

The SIRIUS trial demonstrated a dual benefit of OCS dose reduction and decreased exacerbation rates using mepolizumab, which neutralizes the IL-5 ligand. How might the differing mechanism of benralizumab, which targets the IL-5 receptor alpha, theoretically impact the degree of eosinophil depletion and OCS-sparing efficacy in a patient with highly refractory eosinophilic asthma?

Key Response

Benralizumab induces antibody-dependent cell-mediated cytotoxicity (ADCC) leading to near-complete apoptosis of eosinophils in both blood and tissue, whereas mepolizumab neutralizes circulating IL-5. Understanding this mechanistic difference aids in selecting or switching biologics if a patient fails to achieve complete OCS independence on mepolizumab.

Attending

When aggressively tapering chronic oral glucocorticoids in patients newly started on mepolizumab, what are the primary clinical risks associated with unmasking underlying conditions, and how should we monitor for adrenal insufficiency during the steroid withdrawal phase?

Key Response

Tapering chronic steroids can unmask adrenal insufficiency due to long-standing HPA axis suppression, or reveal other eosinophilic conditions like EGPA or nasal polyposis that were previously suppressed by systemic steroids. Anticipating and actively managing these risks with slow tapers and cortisol testing is crucial for safe OCS weaning.

Scholarly Review

Critical appraisal through the lens of expert reviewers and guideline development

PhD

The primary endpoint of the SIRIUS trial was an ordinal categorical variable representing the percent reduction in glucocorticoid dose. What are the statistical advantages and potential limitations of using a categorized ordinal outcome rather than a continuous variable for absolute dose reduction in this study design?

Key Response

Categorization standardizes the response relative to baseline, accounting for patients starting on vastly different absolute doses. However, collapsing continuous data into categories can reduce statistical power and obscure absolute dose changes that might be clinically meaningful for safety profiling.

Journal Editor

The SIRIUS trial implemented a structured algorithm for glucocorticoid tapering based on clinical stability. How does the choice of a highly protocolized, investigator-driven tapering schedule potentially limit the external validity of the study when translating these OCS-sparing effects to routine clinical practice?

Key Response

In the trial, OCS tapering was aggressive and strictly monitored every 4 weeks. In the real world, clinical inertia, patient fear of exacerbations, and lack of protocolized monitoring often result in significantly less OCS sparing than demonstrated in controlled efficacy trials, representing a threat to external validity.

Guideline Committee

Based on the robust OCS-sparing effects demonstrated in the SIRIUS trial, how should current GINA guidelines formulate recommendations regarding the sequencing of anti-IL-5 therapies versus chronic low-dose OCS in Step 5 management of severe eosinophilic asthma?

Key Response

GINA currently recommends using biologic therapies like mepolizumab in patients with severe Type 2 asthma before resorting to maintenance OCS. The SIRIUS trial provides high-quality evidence that biologics can safely replace the need for systemic steroids while providing superior asthma control, thus relegating maintenance OCS to a last resort to avoid severe metabolic side effects.

Clinical Landscape

Noteworthy Related Trials

2014

MENSA Trial

n = 576 · NEJM

Tested

Mepolizumab 75mg IV or 100mg SC every 4 weeks

Population

Patients with severe eosinophilic asthma and frequent exacerbations

Comparator

Placebo

Endpoint

Rate of asthma exacerbations

Key result: Mepolizumab significantly reduced asthma exacerbations by 47 to 53 percent compared to placebo while improving lung function and asthma control.

2017

ZONDA Trial

n = 220 · NEJM

Tested

Benralizumab 30mg SC every 4 or 8 weeks

Population

Patients with severe oral glucocorticoid-dependent eosinophilic asthma

Comparator

Placebo

Endpoint

Percentage reduction in oral glucocorticoid dose

Key result: Benralizumab allowed for a median 75 percent reduction in oral glucocorticoid dose compared to 25 percent with placebo, while also reducing exacerbations.

2018

VENTURE Trial

n = 210 · NEJM

Tested

Dupilumab 300mg SC every 2 weeks

Population

Patients with severe oral glucocorticoid-dependent asthma

Comparator

Placebo

Endpoint

Percentage reduction in oral glucocorticoid dose

Key result: Dupilumab reduced oral glucocorticoid use by 70 percent compared to 42 percent for placebo, with simultaneous improvements in exacerbation rates and lung function.

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