The Effectiveness of Tocilizumab in the Treatment of COVID-19 in Adults: A Meta-Analysis of Randomized Controlled Trials.

Background: Since December 2019, COVID-19 has spread to the world which leads to a global health threat. We aimed to investigate the effectiveness of tocilizumab on COVID-19 patients. Methods: We systematically searched PubMed, EMBASE, the Cochrane Central Register of Controlled Trials (CENTRAL) and WHO international Clinical Trials Registry Platform (ICTRP) from their inception to March 10, 2021 for randomized controlled trials (RCTs) on tocilizumab supplementation in adults with COVID-19 disease. The primary outcomes were mortality at 28-30 day and 60-day, incidence of mechanical ventilation (MV), composite outcome of death or MV, time to hospital discharge, and intensive care unit (ICU) admissions. A random-effects meta-analysis model was used to pool studies. Results: Eleven studies with a total of 6,579 patients were included in our meta-analysis, of which 3,406 and 3,173 were respectively assigned to the tocilizumab and control groups. Tocilizumab could signicantly reduce 28-30 day mortality (RR = 0.89, 95% CI 0.80-0.99, P = 0.04), incidence of MV (RR= 0.79, 95% CI 0.71-0.89, P = 0.0001), composition outcome of MV or death (RR = 0.81, 95% CI 0.72-0.90, P = 0.0002), time to hospital discharge (HR = 1.30, 95% CI 1.16-1.45, P (cid:0) 0.00001 ), ICU admissions (RR = 0.64, 95% CI 0.47-0.88, P = 0.006), serious infection (RR = 0.61, 95% CI 0.40-0.94, P = 0.02) and events of serious adverse advents (RR = 0.64, 95% CI 0.47-0.86, P = 0.004). There was no signicant difference between tocilizumab and control groups in 60-day mortality and adverse events (AEs). Conclusions: Tocilizumab could reduce the short-term mortality, incidence of MV, composite outcome of death or MV, ICU admissions, serious infection and events of serious adverse advents, and shorten the time to hospital discharge in hospitalized patients with COVID-19. The optimal effective dose needs to be conrmed by further studies. x-ray tomography; (2) tocilizumab intravenously (IV), with dosages ranging from 400 to 800 mg; (3) comparison: standard care; (4) outcomes: the primary outcomes were mortality at 28–30 day and 60-day, incidence of mechanical ventilation (MV), composite outcome of death or MV, intensive care unit (ICU) admissions, and time to hospital discharge. The secondary outcomes were time to oxygen supply independency, non-serious adverse events, serious adverse events, serious infection, events of serious adverse advents; (5) study design: RCTs. The to Two of


Introduction
In December 2019, there had been more and more con rmed cases of novel coronavirus pneumonia in Wuhan, China, which then quickly spread to the world leading to a global health threat [1]. The World Health Organization (WHO) o cially named this pneumonia coronavirus disease 2019 (COVID-19) on February 11, 2020. [2] COVID-19 can be mild or progressive to dyspnea and/or hypoxemia, and severe cases often progress to respiratory failure, acute respiratory distress syndrome (ARDS) and septic shock, which can further lead to multiple organ dysfunction syndrome (MODS) or death [3,4]. Although most COVID-19 patients are self-limited, it still causes serious loss of life worldwide [3]. As of April 26, 2021, more than 14.6 million people have been infected and more than 3 million people have died around the world [5]. All parts of the world are striving to nd effective treatments to control the ongoing COVID-19 pandemic [6]. monoclonal antibody against human interleukin 6 (IL-6) receptor, which has been con rmed that it could reduce the biomarkers of COVID-19 infection and increase the level of lymphocyte count [10].
There are several meta-analyses of observational studies which have showed that tocilizumab could reduce the mortality of COVID-19 [11][12][13][14][15]. Considering the low levels of evidence in observational studies may confound the ndings, the bene ts of tocilizumab on mortality of COVID-19 must be cautiously interpreted. Several newly published randomized controlled trials (RCTs) [6, 16-25] and meta-analyses [26][27][28] of RCTs have investigated the effects of tocilizumab as adjunctive therapy in COVID-19 patients, but reported inconsistent results. Moreover, due to daily update of studies regarding tocilizumab anti-COVID-19, it is mandatory to conduct an updated study on this eld. Hence, we conducted an updated meta-analysis to synthesize the evidence of well-conducted RCTs to evaluate the effects of tocilizumab in COIVD-19 treatment.

Literature search
We systematically searched PubMed, EMBASE, the Cochrane Central Register of Controlled Trials (CENTRAL) and WHO international Clinical Trials Registry Platform (ICTRP) from their inception to March 10, 2021 for RCTs, by using a combination of Medical Subject Headings (MeSH) or Emtree and related key words in all elds. The keywords used were "tocilizumab" or "atlizumab" or "Actemra" or "Roactemra" or "lusinex" or "anti-interleukin 6 antibody", and "COVID-19" or "coronavirus 2019" or "2019-nCoV Infection" or "SARS CoV 2 Infection" or "2019 Novel Coronavirus Disease". We also scanned the reference lists from relevant studies and key review articles to locate relevant studies.

Inclusion Criteria
Studies meeting the following criteria were included: (1) participants: patients aged ≥ 18 years with con rmed SARS-coV-2 infection by a positive polymerase-chain -reaction test for SARS-CoV-2 in any body uid and/or bilateral chest in ltrates on chest x-ray or computed tomography; (2) intervention: tocilizumab administered intravenously (IV), with dosages ranging from 400 to 800 mg; (3) comparison: standard care; (4) outcomes: the primary outcomes were mortality at 28-30 day and 60-day, incidence of mechanical ventilation (MV), composite outcome of death or MV, intensive care unit (ICU) admissions, and time to hospital discharge. The secondary outcomes were time to oxygen supply independency, nonserious adverse events, serious adverse events, serious infection, events of serious adverse advents; (5) study design: RCTs. The language was restricted to English. Two of the authors (JZ and CC) independently evaluated the eligibility of all studies obtained from the databases according to the above selection criteria. Discrepancies regarding study inclusion between reviewers were resolved through discussion.

Data Extraction And Risk Of Bias Assessment
Two of the authors (JZ and CC) independently extracted data. The following data were extracted from the studies: study name (name of the rst author with publication year), country and design, participants (sample size, sex and age), intervention arms and controls (intervention drug, dose, and duration of follow-up) and outcomes (primary and secondary outcomes). The Cochrane Collaboration's tool for assessing risk of bias was used to appraise the quality of each RCT, which includes the following criteria: adequacy of sequence generation, allocation concealment, blinding of participants and personnel, blinding of outcome assessors, incomplete outcome data, selective reporting and other biases [29]. JZ and CC reviewed all the included studies and rated them "low risk", "unclear risk" or "high risk" based on the Cochrane risk-of -bias tool.

Statistical analysis
To evaluate the effect of tocilizumab on COVID-19, we calculated relative risks (RRs) with 95% con dence intervals (CIs) for dichotomous outcomes. As for continuous outcomes, mean differences or standard mean differences between the tocilizumab and placebo groups were used for meta-analysis. Time-toevent outcomes were analyzed by using hazard ratios (HRs). Heterogeneity in results across studies was examined by using Cochran's Q and I 2 statistics [30]. The null hypothesis that the studies are homogeneous was rejected if the P value for heterogeneity was < 0.10 or I 2 was > 50%. Studies with an I 2 statistic of > 50% were considered to have signi cant heterogeneity. A random-effects model was used to pool the study estimates for each outcome.
A sensitivity analysis was conducted to assess the in uence of individual studies on the pooled result when P was < 0.10 or I 2 was > 50%, by excluding each study one by one and recalculating the combined results on the remaining studies [30]. All analyses of data were performed with Review Manager 5.4 (Cochrane Informatics and Knowledge Management Department), available from http://tech. cochrane.org/. Fig 1 shows a ow diagram of the study selection process. A total of 1,074 records were initially identi ed from the database search. Of these, 382 records were excluded for duplicates, and 653 records were excluded after screening the titles and abstracts. After full-text screening, a total of 11 studies [6, [16][17][18][19][20][21][22][23][24][25] were included in the meta-analysis.

Characteristics of included studies
The characteristics of studies included in our meta-analysis were summarized in Table 1 Overall, a total of 6,579 patients were enrolled in our meta-analysis, 4,906 of them were male (74.6%), and the average age ranged from 54 to 75 years old. A total of 3,406 were administrated with tocilizumab in addition to standard care or placebo, 14 of which were administrated with tocilizumab and favipiravir, and 3,173 were administrated with standard care or placebo, 7 of which were administrated with favipiravir. Except two [21,22] RCTs used only a single dose of tocilizumab, other nine [6, 16-20, [23][24][25] RCTs allowed additional dose if needed. The tocilizumab doses vary from 400 mg to 800 mg and were all administrated intravenously infusion for more than one hour. The maximum dose was 480 mg/d in one study [24], The pooled analysis showed that there was a signi cant difference between tocilizumab and control groups (RR = 0.81, 95% CI 0.72-0.90, P = 0.0002) (supplemental Fig 5).  6).

Secondary outcomes Time to oxygen supply independency
Our meta-analysis including three RCTs [17,21,22] with 502 cases showed that there was no signi cant difference in time to oxygen supply independency between tocilizumab and control groups (HR = 1.21, 95% CI 0.94-1.57, P = 0.14) (supplemental Fig 8).

Discussion
Our meta-analysis investigated the effect of adjunctive tocilizumab on COVID-19 patients in hospital and found that tocilizumab supplementation could reduce 28-30 days mortality, the incidence of mechanical ventilation, composite outcome of death or mechanical ventilation, ICU admissions, serious infection and events of SAE, and shorten the time to discharge. There was no evidence that tocilizumab could increase the adverse advents and reduce 60-day mortality and time to oxygen supply independency.
The results of our meta-analysis are not completely consistent with recently published meta-analyses [26,28,31,32], which showed that tocilizumab had no effect on 28-30 days mortality in COVID-19 patients.
There are several strengths in our meta-analysis. Firstly, with the updating of the literature, our metaanalysis was able to include the most recently published RCTs. Secondly, given the clinical heterogeneity across included studies, we used the random-effects model to pool the results, which is generally a plausible match to the underlying population effect distribution [33].
All published meta-analyses have different degrees of bene t from tocilizumab. Tleyjeh et al [32] showed that tocilizumab could reduce the risk of MV and the composition outcome of MV or death. Lin et al [26] found that COVID-19 patients receiving tocilizumab had a lower rate of MV, ICU admission, composite outcome of MV or death compared with control group. Sophie et al [28] showed evidence of a bene cial effect of tocilizumab compared with control on MV. Chia et al [31] found that COVID-19 patients with use of tocilizumab could bene t in the composite endpoint of MV and/or death. Moreover, Ghosn et al [27] including 8 RCTs had the same result that tocilizumab could reduce all-cause mortality at 28-day in hospitalized COVID-19 patients. Rezaei et al [34] including forty-ve studies with 13,189 patients showed that tocilizumab can reduce mortality rates in severe to critical COVID-19 patients. Researches [35,36] have shown that interleukin-6 is an important cytokine associated with mortality and severity of COVID-19. One genomic analysis [37] showed that genetic variants in interleukin-6 in ammatory pathway are associated with life-threatening in COVID-19. All of the studies support the therapeutic strategy of inhibiting interleukin-6 in severe COVID-19 patients. Tocilizumab is an anti-IL-6 receptor-a monoclonal antibody, which has been identi ed to speci cally bind soluble and membranal IL-6R and inhibit signal transduction [6]. Combined with our meta-analysis, we conclude that tocilizumab could reduce the shortterm mortality, the composition outcome of MV or death, risk of MV, ICU admission in moderate to critical COVID-19 patients.
Our study analyzed time to discharge and found that tocilizumab could signi cantly shorten time to hospital discharge. We also analyzed time to oxygen supply independency, and found that there was no signi cant difference between tocilizumab and control group. A retrospective study [38] found that patients had lowered their oxygen intake after using tocilizumab compared with control group in severe COVID-19 patients. Considering the data that could be analyzed was limited, we only included three RCTs [17,21,22] in this meta-analysis. Considering the limited studies and patients, we could not conclude that tocilizumab has no effect on time to oxygen supply independency. There are need more effective and larger RCTs to con rm this issue.
As for safety, all published meta-analyses [26-28, 31,32] got the similar conclusions that tocilizumab was safe and did not increase adverse events and serious adverse events compared with control group in COVID-19 patients which were consistent with our results. We also found that tocilizumab could reduce the serious infection and events of SAEs. Lin et al [26] and Ghosn et al [27] also separately found that tocilizumab could reduce serious infection and SAEs, which were consistent with our results.
Although a major strength of this meta-analysis was that we included the largest number of RCTs in currently, this study also had limitations. First, there are many ongoing RCTs, also indicate that follow-up of ongoing trials is needed and meta-analyses need to be updated when necessary. Second, the dose of tocilizumab varied from 400-800 mg/d in included studies, the optimal effective dose of tocilizumab is still uncertain. Thirdly, given the limited data on oxygen supply independency and 60-day mortality, further studies are warranted.

Conclusions
Tocilizumab could reduce the short-term mortality, the incidence of mechanical ventilation, the composite outcome of death or MV, ICU admissions, serious infection and events of SAE, and shorten the time to discharge, and could not increase the adverse advents of the hospitalized patients with COVID-19. But the optimal effective dose needs to be con rmed by further studies. Availability of data and materials Not applicable.

Competing of interest
The authors declare that they have no competing interests.

Funding
The authors declare that this research did not receive any speci c grant from funding agencies in the public, commercial, or not-for-pro t sectors.

Authors' contributions
Chun Chen and Jing Zhang initiated and coordinated the study. Chun Chen, Jing Zhang and ZeMei Zhou were responsible for the literature research, data extraction, statistical analysis, and Chun Chen wrote the rst draft. Studies reviewed by Jing Zhang. All authors read and approved the nal manuscript.

Figure 1
Study ow diagram. All studies were randomized controlled trials.

Figure 2
Risk of bias summary of the included studies. The forest plot of mortality at 28-30 day and 60 day between the tocilizumab and control groups. The forest plot of incidence of mechanical ventilation between the tocilizumab and control groups.

Supplementary Files
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