Fasenra (Benralizumab) for Severe Eosinophilic Asthma
Fasenra is indicated as add-on maintenance therapy for patients aged 6 years and older with severe asthma and an eosinophilic phenotype, administered as 30 mg subcutaneously every 4 weeks for the first 3 doses, then every 8 weeks thereafter. 1
Indications
Fasenra has two FDA-approved indications 1:
- Severe eosinophilic asthma: Add-on maintenance treatment for patients ≥6 years with severe asthma and eosinophilic phenotype
- Eosinophilic granulomatosis with polyangiitis (EGPA): Treatment for adult patients
Key limitation: Fasenra is NOT indicated for acute bronchospasm or status asthmaticus 1
Patient Selection Criteria
The ideal candidate for benralizumab has:
- Blood eosinophils ≥300 cells/μL (though benefit seen down to lower levels) 2, 3
- History of ≥2 exacerbations requiring systemic corticosteroids in the past year 1
- Uncontrolled symptoms despite medium-to-high dose inhaled corticosteroids plus long-acting beta-agonist 2, 3
- Pre-bronchodilator FEV1 <90% predicted 1
According to recent European guidance, consider benralizumab specifically for patients with highly eosinophilic asthma as a preferred option, particularly when comorbid chronic rhinosinusitis with nasal polyps is present 4.
Dosing Regimen
Standard Dosing (≥12 years and pediatric ≥35 kg)
- 30 mg subcutaneously every 4 weeks for 3 doses
- Then 30 mg every 8 weeks 1
Pediatric Dosing (6-11 years)
- Weight <35 kg: 10 mg subcutaneously every 4 weeks for 3 doses, then every 8 weeks
- Weight ≥35 kg: 30 mg subcutaneously every 4 weeks for 3 doses, then every 8 weeks 1
The every-8-week maintenance regimen is optimal based on pharmacokinetic modeling showing the 90% effective concentration (927 ng/mL) is below steady-state levels achieved with this dosing 5. Meta-analysis confirms 30 mg every 8 weeks may be more effective than every 4 weeks for quality of life outcomes 6.
Expected Clinical Outcomes
Exacerbation Reduction
Benralizumab reduces annual asthma exacerbation rates by 74% in patients with blood eosinophils ≥300/μL (rate ratio 0.26,95% CI 0.19-0.36) 2. Across all studies, the pooled incidence rate ratio is 0.53 (95% CI 0.39-0.72) with high certainty of evidence 3. Real-world data shows 92-93% reduction in exacerbation rates by weeks 16-48 7.
Lung Function
- FEV1 improvement of 0.25 L at week 48 in patients with eosinophils ≥300/μL 2
- Pooled mean difference of 0.107 L across studies 8
- Real-world data shows 27.7% increase in FEV1 at 6 months 9
Symptom Control and Quality of Life
- Significant improvement in ACQ scores (mean difference -0.174) 8
- Over 90% of patients show improved quality of life (mini-AQLQ) 9
- 72.7% achieve better asthma control (ACT scores) 9
Oral Corticosteroid Sparing
Benralizumab reduces daily oral corticosteroid requirements with high certainty of evidence 3. Real-world data demonstrates 50% dose reduction with 25-28% of patients requiring >5 mg/day at weeks 16-48 (down from baseline) 7.
Biomarker Response
- Blood eosinophils decrease by 97.5% within weeks, typically to near-zero levels 9, 7
- FeNO decreases by 57% at 6 months 9
- Eosinophil depletion occurs rapidly due to benralizumab's mechanism targeting IL-5 receptor α, causing antibody-dependent cell-mediated cytotoxicity 10
Onset of Action
Rapid FEV1 improvement occurs with estimated half-maximum time of 7.6 days (vs. 18 days for placebo), with greater response in patients with higher baseline eosinophil counts 5. Clinical benefits on exacerbations and symptoms become evident by week 16 and are sustained through week 48 and beyond 7.
Safety Considerations
Common Adverse Events
The safety profile is similar to placebo 10, 3:
- Nasopharyngitis (most common)
- Worsening asthma
- Headache
- Injection site reactions (erythema in ~35% in some trials) 11
Discontinuation rate is remarkably low at 1.3% in real-world settings 7.
Serious Adverse Events
Benralizumab shows no significant increase in drug-related serious adverse events compared to placebo (low to very low certainty of evidence) 3. No anaphylaxis or serious safety signals have emerged in large trials 2, 3.
Special Populations
Pregnancy (Category: No adequate data)
- No evidence of teratogenicity in animal studies at 310 times human exposure 1
- Crosses placenta; eosinophil suppression observed in infant monkeys with gradual recovery by 6 months 1
- Poorly controlled asthma poses greater risk (preeclampsia, prematurity, low birth weight) than theoretical drug risks 1
- Consider continuing if benefits outweigh risks; closely monitor asthma control
Lactation
- Unknown if present in human milk, though IgG antibodies are present in small amounts 1
- Consider maternal need versus potential infant exposure
Pediatric (6-11 years)
- Safety profile similar to adults and adolescents 1
- Weight-based dosing ensures appropriate exposure 1
Geriatric (≥65 years)
- No dose adjustment needed; 13% of trial patients were ≥65 years 1
- No differences in safety or efficacy observed 1
Administration
- Subcutaneous injection in abdomen, thigh, or upper arm 4
- First 1-2 injections in healthcare setting to monitor for reactions 4
- Self-injection possible thereafter with proper training 4
- Prepare medication, clean injection site with alcohol, inject using auto-injector or pre-filled syringe 4
Monitoring
- Baseline: Blood eosinophil count, FEV1, asthma control (ACT/ACQ), exacerbation history
- Week 16: Assess eosinophil depletion (should be near-zero), FEV1 improvement, symptom control
- Week 48 and ongoing: Continue monitoring exacerbation rates, lung function, symptom control, oral corticosteroid dose
Clinical Positioning
According to recent European guidance, benralizumab is the preferred choice for eosinophilic asthma, particularly highly eosinophilic phenotypes 4. It is one of three anti-IL-5 pathway biologics (with mepolizumab and reslizumab) recommended for severe eosinophilic asthma 4.
Benralizumab offers advantages over other anti-IL-5 agents through complete eosinophil depletion via antibody-dependent cell-mediated cytotoxicity and convenient every-8-week dosing after initial loading 10. Real-world comparative studies show equivalent efficacy to mepolizumab across clinical outcomes 12.
For patients with multiple type 2 comorbidities (chronic rhinosinusitis with nasal polyps, atopic dermatitis), dupilumab may be preferred 4. For allergy-driven asthma or females planning pregnancy, omalizumab is first-line 4.
Cost-Effectiveness
The incremental cost-effectiveness ratio per quality-adjusted life year is above willingness-to-pay thresholds for all biologics in severe asthma, though potential savings derive from decreased hospitalizations and emergency visits 3. This economic consideration should not override clinical decision-making when patients meet appropriate criteria.