Recent trials have assessed the efficacy and safety of novel monoclonal antibodies such as reslizumab and benralizumab. However, the overall efficacy and safety anti—interleukin (IL) 5 treatment in asthma have not been thoroughly assessed.
Randomized controlled trials (RCTs) of anti-IL-5 treatment on patients with asthma published up to October 2016 in PubMed, Embase, and Cochrane Central Register of Controlled Trials (CENTRAL) that reported pulmonary function, quality of life scores, asthmatic exacerbation rate, blood and sputum eosinophil counts, short-acting β-agonist (SABA) rescue use, and adverse events were included. The pooled mean difference, and relative risks (RR), and 95% confidence intervals (CIs) were calculated using random-effects models.
Twenty studies involving 7100 patients were identified. Pooled analysis revealed significant improvements in FEV1 (first second forced expiratory volume) (MD = 0.09, 95% CI: 0.06–0.12, I2 = 10%), FEV1% (MD = 3.75, 95% CI: 1.66–5.83, I2 = 19%), Asthma Quality of Life Questionnaire (AQLQ) score (MD = 0.22, 95% CI: 0.15–0.30, I2 = 0%), decreased blood, sputum eosinophils and asthmatic exacerbation (RR = 0.66, 95% CI: 0.59–0.73, I2 = 51%); peak expiratory flow (PEF) (MD = 5.45, 95% CI: -2.83–13.72, I2 = 0%), histamine PC20 (MD = -0.62, 95% CI: -1.92–0.68, I2 = 0%) or SABA rescue use (MD = -0.11, 95% CI: -0.3–0.07, I2 = 30%) were unaffected; adverse events were not increased (RR = 0.93, 95% CI: 0.89–0.98, I2 = 46%). No publication bias was observed (Egger's P = 0.78).
Anti-interleukin 5 monoclonal therapies for asthma could be safe for slightly improving FEV1 (or FEV1% of predicted value), quality of life, and reducing exacerbations risk and blood and sputum eosinophils, but have no significant effect on PEF, histamine PC20, and SABA rescue use. Further trials required to establish to clarify the optimal antibody for different patients.
Citation: Wang F-P, Liu T, Lan Z, Li S-Y, Mao H (2016) Efficacy and Safety of Anti-Interleukin-5 Therapy in Patients with Asthma: A Systematic Review and Meta-Analysis. PLoS ONE 11(11): e0166833. https://doi.org/10.1371/journal.pone.0166833
Editor: Stelios Loukides, National and Kapodistrian University of Athens, GREECE
Received: September 5, 2016; Accepted: November 5, 2016; Published: November 22, 2016
Copyright: © 2016 Wang et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: All relevant data are within the paper and its Supporting Information.
Funding: The authors received no specific funding for this work.
Competing interests: The authors have declared that no competing interests exist.
Asthma is a common chronic inflammatory disease that affects more than 300 million people worldwide, and imposes a high disease burden and economic impact globally [1–3]. Despite taking high-dosage inhaled corticosteroids according to the Global Initiative for Asthma (GINA) guidelines, at least 40% of patients continue to suffer from inadequately controlled symptoms, either because they are truly resistant or because they do not take them [4, 5]. Patients who remain uncontrolled can use other drugs such as leukotriene-receptor antagonists, slow-release theophylline, and long-acting anticholinergics . Since the anti-immunoglobulin (Ig)E humanized monoclonal antibody omalizumab became the first biological treatment approved for treating allergic asthma, many small molecules and monoclonal antibodies targeting biomolecular specificities have been investigated for treating symptomatic asthma . Eosinophilic inflammatory infiltration is a central event in asthma pathogenesis. IL-5 is the chief cytokine responsible for eosinophil production, survival, maturation and recruitment and activation at allergic inflammation sites . Preclinical studies have demonstrated a key role for IL-5 in murine models of allergen-induced airway eosinophilia and hyperresponsiveness . Given the relationship of IL-5 to eosinophilia and asthma severity, human(ized) monoclonal antibodies targeting IL-5 have shown great promise in severe refractory asthma with persistent eosinophilia [10, 11]. The anti-IL-5 agents benralizumab, reslizumab, and mepolizumab have been investigated for treating asthma [12, 13]. However, their effects on lung function (especially FEV1) have been less consistent. Here, we conducted a meta-analysis of randomized, controlled trials (RCTs) to assess whether anti-IL-5 monoclonal antibodies therapy is safe and effective in patients (more than 12 years) with asthma.
Literature searches and study selection
PubMed, Embase, and the Cochrane Central Register of Controlled Trials (CENTRAL) were searched for articles published from 1946 to October 2016, using the search terms: ‘‘anti–interleukin-5” or ‘‘mepolizumab” or “benralizumab” or “reslizumab” or “monoclonal antibody” or “anti-IL-5”, combined with ‘‘asthma”. Language restrictions were not applied. Reviews and the reference lists of relevant articles were also screened for additional articles of interest. Two independent authors (FPW and TL) screened all references according to the selection criteria. To ensure a complete review of the available studies, the abstracts of relevant scientific meetings were also examined, but trials published solely in abstract form were excluded. Any disagreements were resolved by consensus with a third author when necessary. The details of the search strategy are displayed in S1 Table.
Inclusion and exclusion criteria
Eligible clinical trials were defined as: (1) adults/adolescents (≥12 years) with diagnosis of asthma; (2) investigations of patients who received anti-interleukin-5 monoclonal antibody therapy at any dose, placebo-controlled or standard therapy; (3) randomized (parallel group) placebo-controlled trials, and (4) RCTs reporting the following outcomes: blood and sputum eosinophil count, asthma exacerbation, lung function, asthma control and quality of life scores, rescue use of SABA and adverse events. We excluded non-randomized, observational, cohort, case-control and non-blinded clinical trials. FPW and TL independently screened all references according to the selection criteria. Differences in opinion about inclusion were resolved by mutual agreement and arbitration of a third author (HM).
Data extraction and quality assessment
FPW and TL independently extracted related data in blinded fashion from eligible studies based on the predefined criteria, which included the characteristics of the trials, interventions, and outcomes. The predefined primary outcomes were lung function [first second forced expiratory volume (FEV1), FEV1% of predicted value, peak expiratory flow (PEF), histamine PC20], the Asthma Quality of Life Questionnaire (AQLQ) scores, and asthma exacerbation. Asthma exacerbation was defined as a worsening of asthma requiring increased corticosteroids or albuterol dose to control symptoms and/or the need for asthma-related emergency treatment/hospitalization. Secondary outcomes were adverse events and efficacy outcomes [blood eosinophil count, sputum eosinophils (%), short-acting β-agonist (SABA) rescue use]. The risk of bias was assessed using Cochrane-recommended tools, which included: (1) adequate sequence generation; (2) allocation concealment; (3) blinding; (4) incomplete outcome data addressed; (5) free of selective reporting; and (6) free of other bias .
All analyses were performed with Review Manager (Version 5.3, The Cochrane Collaboration) and Stata (Version 12.0, Stata Corporation, USA), P <0.05 was considered statistically significant. If a study presented more than two interventions, we combined two or three intervention groups into a single intervention group in accordance with the Cochrane handbook.9 Random-effects model was applied in all data analyses regardless of statistical heterogeneity. Risk ratio (RR) and 95% CIs were used to analyze dichotomous data, and mean difference and 95% CI were used for continuous data. Heterogeneity assumptions were assessed using the I2 statistic (I2>50% indicates significant heterogeneity), and tested with the χ2 statistic (P<0.05). However, the number of studies affects both the power of the heterogeneity test and the heterogeneity measures I2, but not . In order to the increase the power of detecting heterogeneity, the 95% CI of I2 and were calculated [15–17]. If substantial heterogeneity was identified, subgroup and sensitivity analyses were performed. Moreover, we separately performed subanalyses in different drugs for each outcome. Publication bias was determined using the Begg’s funnel plot and assessed by Egger’s test if the number of the studies was larger than ten.
We identified 3047 manuscripts: 2019 from PubMed, 893 from Embase, 135 from CENTRAL. Based on title/abstract and full-text screening, 20 RCTs were included in the meta-analysis. Fig 1 summarized the study selection process [18–37].
Tables 1–3 lists the RCT characteristics, and Table 4 describes the baseline characteristics of the patients enrolled. Sample sizes ranged from 19 to 1306 subjects. Nine, five, and six trials used mepolizumab [18–26], reslizumab [27–31], and benralizumab [32–37], respectively. Treatment duration ranged from 1 day to 56 weeks and follow-up ranged from 12 to 56 weeks. Seven studies administered drugs used subcutaneous injection [25, 26, 32, 33, 35–37], while the remaining studies used intravenous infusion [18–24, 27–31, 34]. Nine studies involved patients with severe/refractory asthma [22–28, 36, 37]; four studies included patients with mild, mild to moderate, or moderate asthma [18–21]; the remaining studies did not specify asthma severity [29–35]. Corren et al.  and Castro et al.  studied patients with non-eosinophilic asthma.
FEV1. Fourteen studies assessed FEV1 responsiveness to anti-interleukin 5 treatment [19,21–24,26,28–31,33,34,36,37]. Six studies reported significant improvements in FEV1 between mepolizumab, reslizumab, and benralizumab treatments and placebo, while the remaining studies reported no effect on FEV1. Fig 2 showed that reslizumab was more effective than other two anti-interleukin 5 monoclonal antibodies in improving FEV1 (MD = 0.12, 95% CI: 0.04–0.19, P = 0.002), and the pooled data analysis revealed a slight improvement (MD = 0.09, 95% CI: 0.06–0.12, P<0.001). There was minimal heterogeneity (I2 = 10%, P = 0.34, 95% CI -53% to 47%, ).
FEV1% of predicted value.
Seven trials using three different anti-interleukin 5 antibodies reported FEV1% of predicted value [23,25–28,34,35]. Overall, anti-interleukin 5 treatment was associated with modestly improved in FEV1% of predicted value compared to placebo (MD = 3.75, 95% CI 1.66–5.83, P = 0.0004) (Fig 3), and heterogeneity was not statistically significant (I2 = 19%, P = 0.29, 95% CI 0% to 62%, ). When looking at subgroups, there were no differences by benralizumab (MD = -0.88, 95% CI -6.88–5.13, P = 0.78).
Peak expiratory flow (PEF) and Provocative concentration of histamine (histamine PC20).
Four trials depicted PEF change after anti-interleukin 5 treatment [19,21,34,35], and only three about mepolizumab studies reported the results in histamine PC20 [18,19,22]. Results from the pooled data illustrated that anti-interleukin 5 could not significantly improve PEF (MD = 5.45, 95% CI: -2.83–13.72, P = 0.2) (Fig 4) or PC20 (MD = -0.62, 95% CI: -1.92–0.68, P = 0.35) (Fig 5). Studies were highly homogeneous (I2 = 0%, P = 0.73, 95% CI 0% to 84%, ; I2 = 0%, P = 0.73, 95% CI 0% to 89%, ). Our confidence in these results is low due to the wide CI.
Asthma Quality of Life Questionnaire (AQLQ) score.
Eight trials of three different anti-interleukin 5 antibodies reported AQLQ scores [22,24,29,31,33,34,36,37]. Pooled analysis showed that anti-interleukin 5 treatment was associated with significantly improved AQLQ score (MD = 0.22, 95% CI 0.15–0.30, P<0.001), with no significant heterogeneity (I2 = 0%, P = 0.94, 95% CI 0% to 29%, ) (Fig 6). Among subgroups, AQLQ scores improved only in the trials involving reslizumab and benralizumab treatment trials (MD = 0.27, 95% CI 0.13–0.42, P = 0.0002; MD = 0.21, 95% CI 0.11–0.31, P<0.001), but not mepolizumab (P = 0.08).
Thirteen studies (6,072 participants) reported on asthma exacerbations [21–29,33,34,36,37]. Table 1 summarizes their definitions for asthma exacerbation. Although these definitions varied, all 13 studies defined exacerbation based on increased corticosteroids or albuterol dose to control symptoms and/or the need for asthma-related emergency treatment/hospitalization. Fig 7 showed that anti-interleukin 5 monoclonal therapies were associated with a significant reduction in asthmatic exacerbation compared with placebo (RR = 0.66, 95% CI, 0.59–0.73, P<0.001), but the reporting was significantly heterogeneous (I2 = 51%, P<0.001, 95% CI 12% to 73%, ).
Blood and sputum eosinophils.
18 trials included blood eosinophil analysis and six trials compared sputum eosinophil levels between anti-interleukin 5 treatment and placebo [18,22–24,28,32]. As the data were reported inconsistently (data were shown as median [range], mean [SD] or geometric mean [log10 SE]), we did not obtain a synthesized analysis of the outcomes. However, from all the results reported, a similar outcome was identified that anti-interleukin 5 significantly decreased blood and sputum eosinophils compared with placebo (S2 Table).
SABA rescue use.
Four trials evaluated the effect of anti-interleukin 5 antibodies on SABA use (Fig 8) [21,29–31]. Analyses of these studies showed a non-significant decrease in the anti–interleukin 5 group compared with the placebo group (MD = -0.11, 95% CI -0.3–0.07, P = 0.22), with low heterogeneity (I2 = 11%, P = 0.34, 95% CI 0% to 54%, ) among the studies.
13 studies reported adverse events, and anti-interleukin 5 therapy was well tolerated [23–26,28–33,35–37]. The pooled RR was 0.93 (95% CI: 0.89–0.98), which showed the lower adverse events incidence were slightly in the anti-interleukin 5 group (P = 0.002), with modest heterogeneity (I2 = 46%, P = 0.02, 95% CI 2.3% to 71%, ) (Fig 9). However, sensitivity analysis that excluded two studies which included patients with non-eosinophilic asthma revealed no heterogeneity (I2 = 0%, P = 0.75, 95% CI 0% to 48%, ) [30,33]. Therefore, the heterogeneity can be explained by the varied participant types. In subgroup analysis, however, only treatment with reslizumab was associated with a trend of lower adverse events incidence (RR = 0.88, 95% CI: 0.81–0.96, P = 0.003), while no significant differences were found in both mepolizumab (RR = 0.95, 95% CI: 0.89–1.01, P = 0.12) and benralizumab treatment groups (RR = 0.98, 95% CI: 0.92–1.04 P = 0.44).
Risk of bias
Fig 10 summarizes the methodological domain assessments for each included study. Most trials had low risk of bias across the six domains. The allocation sequence was adequately generated and concealed in fourteen trials, [22–29,32–37]. The randomization techniques included computer generated randomization codes and minimization. The remaining trials did not report the method used, and we were unable to obtain this information. All but one study was described as double-blinded . Almost all RCTs reported complete outcome data, only one trial reported on attrition insufficiently .
Subgroup analyses and sensitivity analysis
To clarify the heterogeneity or identify the optimal patients for this treatment, subgroup analyses were carried out for asthma exacerbations and FEV1 (Table 5). The studies were stratified according to effects model, asthma severity, asthma types, sample size, drug administration dosage, follow-up duration and published year. Subgroup analyses showed the efficacy of anti-interleukin 5 on asthma exacerbations were only influenced by asthma severity. Most subgroups showed significantly reduced exacerbations risk. Single dose anti-interleukin 5 in two studies showed no significant differences in exacerbation rates. However, the subgroup results should be interpreted with caution because of the limited sample size and potential bias inherent to subgroup analysis. The meta-analysis findings remained stable with multicenter trials. In addition, excluding the results of any single study did not alter the overall findings. Furthermore, based on the subgroups analysis, we could know that anti-interleukin 5 can significantly improve the FEV1 of severe asthma (MD = 0.11, P<0.001) and eosinophilic asthma (MD = 0.11, P = 0.001). This further confirmed that the severe eosinophilic asthma patients are the optimal patients for anti-interleukin 5 treatment.
Publication bias was assessed using Begg’s funnel plot and Egger’s test. Begg’s funnel plot of the 14 studies evaluated the effect of anti-interleukin 5 on FEV1 and the Egger’s test suggested no publication bias (P = 0.78, Fig 11). And also no publication bias was detected by Egger’s test for other outcomes analysis (all P>0.05). However, we could not fully exclude publication bias in four outcomes (FEV1%, PEF, histamine PC20, SABA rescue use); we could not evaluate the potential risk of publication bias, since these tests have very low power in meta-analysis.
We identified 20 RCTs investigating the effect of anti-interleukin 5 monoclonal antibodies in patients with asthma. The results suggest that anti-interleukin 5 therapy was well tolerated and could significantly improve AQLQ score, FEV1, FEV1% of predicted value, and decrease asthmatic exacerbation, blood and sputum eosinophil levels, but yielded no effects in PEF, PC20, SABA rescue use. Additionally, reslizumab seems to be safer and more effective than the other two drugs based on all outcomes. However, since varied baseline of patients among studies, it is not possible to draw a firm conclusion. Different from previous systematic reviews that only included studies of on mepolizumab [38, 39], we included trials about mepolizumab and other two anti-interleukin-5 antibodies-reslizumab and benralizumab. Additionally, the results should be interpreted with caution due to with the relatively small sample sizes and small number of included trials. Therefore, our results may be more believable. In contrast to previous systematic reviews, we found that anti-interleukin-5 treatment slightly increased FEV1 and FEV1% of predicted value. But the clinical relevance of this finding to patients may not be clinically important because of the modest improvement. Only three or four studies reported detailed data, therefore we could not draw exact conclusions for these two parameters due to the insufficient data. Previous two systematic reviews failed to show a significant effect in FEV1, likely due to small number of trials analyzed [38, 39]. Liu et al  converted and pooled continuous variable data such as blood and sputum eosinophils. To reduce the possible bias resulting from data conversion, we only obtained qualitative descriptions with estimations of the two outcomes. Besides, when studies with multiple intervention groups, Liu et al  only selected one pair of interventions and exclude the others which are not generally recommended by Cochrane handbook. Our meta-analysis found that there was a significant improvement in AQLQ score, which is consistent with previous two meta-analyses. However, as the mean change in AQLQ score is less than the clinical minimally important difference of 0.5 units, the clinical relevance of this finding may not be clinically important to patients . Asthma exacerbations are associated with substantial morbidity and mortality . Decreasing the asthma exacerbations rate is a key goal in asthma management. Our meta-analysis showed a significant reduction in exacerbation rates. The clinical relevance of this finding to patients may be clinically important. The inconsistency of the results between asthma exacerbations and rescue use of SABA might due to the next two reasons: 1) the slight improvement in lung functions; 2) most exacerbations in trials were predominantly those that would generally be judged severe on the basis of a need for systemic corticosteroid or requiring admission or visit to emergency. This systematic review also has limitations. First, we aimed to identify the overall effect of anti-interleukin-5 therapy on asthma, the asthma severity and baseline asthma therapy varied among studies (Table 2), so the population examined in this review was too heterogeneous to draw any conclusions about the general asthma population. Further research is needed to clarify which subgroups of patients with asthma can benefit from this treatment. Second, in accordance with the Cochrane handbook, we combined two or three intervention groups into a single intervention group regardless of different intervention dosage and administration routine. This made identifying the optimal dose and regimen for treating asthma difficult. Thirdly, although these studies shared many common issues, there were also substantial subgroup and study heterogeneities. Moreover, there also was significant heterogeneity among studies evaluating asthma exacerbation and adverse events; although we used a random-effects model to account for this, the correction is only partial. As for PEF, histamine PC20 and SABA rescue use, given the small number of studies being meta-analysed, it is difficult to detect heterogeneity and accurately estimate it . Lastly, Ortega et al  re-examined baseline blood eosinophil counts from previous two studies [24,26] on mepolizumab, they found that the use of the baseline at a threshold of at least 150 cells/μL can be a reliable and simple biomarker for patient selection associated with positive clinical responses to mepolizumab treatment. However, due to the lack of individual patient data among all studies, we failed to further analysis the relationship between blood eosinophil counts≥150 cells/μL at baseline and outcomes of mepolizumab, reslizumab and benralizumab treatment.
Our study indicates that anti-interleukin-5 therapy is safe and may reduce asthma exacerbation risk, slightly improve FEV1, FEV1%, and quality of life; and decrease blood and sputum eosinophil levels, although PEF, PC20 were not improved or SABA rescue use reduced. Anti-interleukin-5 therapy may therefore be beneficial as adjunct asthma therapy, particularly in severe and eosinophilic asthma. Further trials are necessary to determine the most effective asthma treatment drug and studies need to be performed that distinguish which patients will respond to particular antibodies, both within and between classes (i.e., who will respond to mepolizumab vs. benralizumab or? reslizumab vs. benralizumab?).
S2 Table. Secondary efficacy outcomes of included RCTs.
S3 Table. The data of all outcomes in all RCTs.
- Conceptualization: HM.
- Data curation: FPW TL.
- Formal analysis: FPW TL ZL SYL.
- Investigation: FPW TL.
- Methodology: HM.
- Project administration: HM.
- Resources: HM.
- Software: FPW TL.
- Supervision: HM.
- Validation: FPW TL.
- Visualization: FPW TL.
- Writing – original draft: FPW TL.
- Writing – review & editing: HM ZL SYL.
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