FormalPara Key Summary Points

Why carry out this study?

As the pandemic progresses, the pathophysiology of COVID-19 is becoming more apparent, and the potential for tocilizumab is increasing.

However, the clinical efficacy and safety of tocilizumab in the treatment of COVID-19 patients remain unclear.

What was learned from the study?

The study was conducted, including 95 patients treated with tocilizumab plus standard treatment and matched controls with 95 patients treated with standard treatment therapy by propensity score from February to April 2020. We searched some databases using the search terms for studies published from January 1, 2020, to June 1, 2021.

Our case-control study found a lower mortality rate in the tocilizumab treatment group than in the standard treatment group (9.47% versus 16.84%, P = 0.134), but the results were not statistically significant.

We selected 49 studies (including 6568 cases and 11,660 controls) that met the inclusion criteria in the meta-analysis. In the overall analysis, we performed a meta-analysis that showed significantly decreased mortality after patients received tocilizumab (OR 0.81, 95% CI 0.69–0.95, P = 0.008). We also revealed significant associations within some subgroups. The sequential trial analysis showed a true-positive result.

No significant associations were observed between tocilizumab and elevated secondary infection risk, discharge, adverse events, and mechanical ventilation in the overall analysis.

Our data suggests that clinicians should pay attention to tocilizumab therapy as an effective and safe treatment for COVID-19 patients.

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Introduction

Coronavirus disease 2019 (COVID-19) may be associated with a dysregulated immune response and hyperinflammation, which can lead to or exacerbate acute respiratory distress syndrome (ARDS) and multiple organ failure [1,2,3]. As the pandemic progressed, there was an unfounded enthusiasm surrounding the use of tocilizumab. However, the clinical efficacy and safety of tocilizumab treatment of COVID-19 patients have been controversial.

Epidemiologic studies and earlier recent retrospective studies have demonstrated that patients infected with SARS-CoV-2 exhibited high plasma levels of circulating interleukin 6 (IL-6), IL-1Ra, IL-1β, IL-10, IL-17, IL-18, interferon γ (IFN-γ), tumor necrosis factor α (TNF-α), C-reactive protein (CRP), granulocyte colony-stimulating factor (G-CSF), and macrophage colony-stimulating factor (M-CSF), suggesting a rapid activation of the innate immune response [4,5,6,7,8,9,10,11]. Several studies have shown that plasma IL-6 levels are elevated in COVID-19 patients in the intensive care unit (ICU), and they appear to be positively correlated with mortality [12,13,14,15,16,17]. In an observational study, tocilizumab, an anti-IL-6 receptor monoclonal antibody, has been approved for the treatment of various inflammatory diseases and appeared to improve outcomes in COVID-19 patients in several countries [2]. Some recent studies have suggested that tocilizumab may be intensively related to a lower risk of intubation or death in severe and critically ill patients with COVID-19 pneumonia. Since the clinical severity of COVID-19 patients appears to be associated with a cytokines storm and an overproduction of soluble inflammatory mediators, tocilizumab is currently under investigation. Still, the results were inconsistent [18,19,20,21,22,23,24,25].

Amid the shortage of robust evidence regarding the use of tocilizumab in COVID-19 patients, we aimed to evaluate the efficacy and safety of tocilizumab treatment for COVID-19 patients in a case-control study and meta-analysis, which will help inform clinical management of COVID-19 patients.

Methods

Patients

The retrospective case-control study was performed between February to April 2020 and was conducted in Wuhan, China. All participants were admitted to the Huoshenshan Hospital and were confirmed COVID-19 cases according to quantitative real-time polymerase chain reaction (qRT-PCR). We received approval from the ethics committee of Huoshenshan Hospital and conducted the study following the tenets of the Declaration of Helsinki and its amendments.

All participants voluntarily provided written informed consent for sample collection and their subsequent analysis. Intravenous tocilizumab was administered at a dose of 8 mg/kg body weight (up to 800 mg), up to twice, 12 h apart. Matched control patients were retrospectively identified within the electronic information database of Huoshenshan Hospital. The primary endpoint was 60 days’ mortality, improvement, and discharge, and critical secondary endpoints were hospital stay, secondary infection, and mechanical ventilation. All participants received standard treatment, including hydroxychloroquine and antiviral therapy, including lopinavir/ritonavir, antimicrobial agents, and corticosteroids.

Study Selection

We searched PubMed, Web of Science, and MedRxiv using the search terms severe acute respiratory syndrome coronavirus 2, COVID-19, SARS-CoV-2, 2019-nCoV interleukin-6 inhibitors, tocilizumab, and coronavirus for studies published from January 1, 2020, to June 1, 2021 (Fig. 1).

Fig. 1
figure 1

Flow diagram of the study selection process

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Data Extraction and Verification

The inclusion criteria of the meta-analysis were: (1) research focus on tocilizumab and COVID-19; (2) studies on humans; (3) the number of cases and controls; (4) papers with full text available. The exclusion criteria of the meta-analysis were: (1) review, (2) case report; (3) animal study; (4) incomplete data and unclear outcome effects; (5) repeat of the report.

Specific information about the included studies is listed in Table 3, including (1) the author’s last name and country, (2) publication and online time, (3) 3thnicity or race, (4) severity of disease, (5) dose of tocilizumab, (6) study design, (7) journal, (8) case size, (9) number of cases and controls, (10) number of discharges in cases and controls, (11) number of deaths in cases and controls, (12) number of secondary infections in cases and controls, and (13) number of mechanical ventilations in cases and controls. First, three authors (Weijun Jiang, Weiwei Li, and Ying Han) independently screened the studies that met inclusion and exclusion criteria and extracted all data. If two or three of the three agreed, the study was included in the meta-analysis. Next, each of the three authors pulled the data, while the other two cross-checked the data. Disagreements were resolved through review and discussion.

Statistical Analysis

Categorical variables were summarized as counts and percentages (%). For the continuous measurement, we used the Kolmogorov-Smirnov test to evaluate the distribution type. We also used mean ± standard deviation (SD) to express the customarily distributed data and otherwise used median and interquartile ranges (IQR) to describe the continuous variables. Continuous variables of different groups of data were compared using independent sample double-tailed t-test and Mann-Whitney test. Chi-square and Fisher’s exact test was used to compare the frequencies of categorical variables. We used a 1:1 propensity score matching (PSM) analysis to reach patients who underwent tocilizumab with those who did not. We used SPSS (v.20.0; SPSS Inc., Chicago, IL, USA) to perform statistical analysis.

We used the DerSimonian and Laird method data in the random-effects model and used the Mantel-Haenszel method in the fixed-effects model. Z-test was used to determine the pooled odds ratio (OR) statistical significance, with P values < 0.05 being considered statistically significant. When the P value for heterogeneity was ≤ 0.10 or I2 ≥ 50%, there was heterogeneity between comparative studies. Conversely, if I2 < 50% and the P value for heterogeneity was > 0.10, this indicated that there was no heterogeneity between comparative studies. We used funnel plots and Egger’s linear regression test to evaluate publication bias. We used STATA version 11.0 (Stata Corp., College Station, TX, USA) to carry statistical analyses. Similarly, we used novel statistical analysis software, known as trial sequence analysis (TSA), to examine the reliability and conclusiveness of the existing evidence.

Results

Basic Characteristics and Demographics

We analyzed a total of 190 participants who were determined to have COVID-19 in the clinical study. Ninety-five patients received standard treatment alone, and 95 received treatment with tocilizumab in addition to standard treatment. Of all patients, 63 (66.32%) cases and 56 (58.95%) controls had coexisting conditions, including hypertension, hyperlipidemia, hyperuricemia, diabetes, chronic cardiac disease, cancer, etc.

Interestingly, we found that both hospital stay and secondary infection risk in the case group were significantly higher than in the control group (P < 0.001). However, the rate of mortality in the tocilizumab treatment group was lower than that in the standard treatment group, but no statistically significant difference was found. We also found that the mortality rate in tocilizumab treatment groups was significantly lower than in the standard treatment group in the stratified ICU analysis (OR 0.52, 95% CI 0.44–0.61, P = 0.048 and OR 0.31, 95% CI 0.10–0.99, P = 0.044). In the subgroup without secondary infection, the tocilizumab treatment group's mortality rate was significantly lower than that in the standard treatment group (OR 0.35, 95% CI 0.12–1.00, P = 0.040).

However, no significant differences in age, disease severity, rate of cure, and basic disease between the tocilizumab group and standard treatment group were found. Our results showed that tocilizumab treatment did not significantly reduce the rate of COVID-19 mortality and the increased secondary infection risk. Clinicians are advised to use this therapy with caution. The clinical characteristics and demographic data of all participants are shown in Tables 1 and 2.

Table 1 Clinical characteristics of all COVID-19 patients
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Table 2 Outcome of tocilizumab treatment COVID-19 patients in stratified analysis
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Study Selection and Characteristics

The combination of search terms produced all the related articles. A preliminary review of titles and abstracts found 157 articles that required a full manuscript review. According to the inclusion criteria, we selected 49 papers with potential relevance through literature retrieval and screening (Fig. 1). In our meta-analysis, a total of 49 studies, including 6568 cases and 11,660 controls, met the inclusion criteria. Table 3 summarizes the characteristics of the selected studies.

Table 3 Characteristics of all studies describing tocilizumab treatment COVID-19 patients in the meta-analysis
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Mortality

In the overall analysis, we performed a meta-analysis of 49 studies (6568 tolcizumab plus standard treatment COVID-19 patients and 11,660 standard treatment COVID-19 patients) that reported that significantly decreased mortality after patients received tocilizumab (OR 0.81, 95% CI 0.69–0.95, P = 0.008). We also revealed significant associations within the mix of race subgroup (OR 0.86, 95% CI 0.79–0.94, P = 0.001), Caucasian subgroup (OR 0.64, 95% CI 0.45–0.89, P = 0.008), severe subgroup (OR 0.65, 95% CI 0.52–0.82, P = 0.001), critical subgroup (OR 0.77, 95% CI 0.66–0.89, P < 0.001), dose of 800 mg subgroup (OR 0.81, 95% CI 0.70–0.94, P = 0.006), no specific dose subgroup (OR 0.74, 95% CI 0.62–0.89, P = 0.001), case-control study subgroup (OR 0.72, 95% CI 0.56–0.91, P = 0.006), journal of published subgroup (OR 0.78, 95% CI 0.64–0.94, P = 0.011), and case size of < 100 subgroup (OR 0.77, 95% CI 0.61–0.98, P = 0.030), but not the remaining subgroups. In addition, there was an edge effect in dose of the ≤ 400 mg subgroup (OR 0.66, 95% CI 0.42–1.03, P = 0.067) and the multicenter case-control subgroup (OR 0.69, 95% CI 0.45–1.05, P = 0.081). For mortality, the number of patients did not reach the optimal information size. However, the blue cumulative Z curve crossed both the traditional boundary and the TSA boundary showing that no more tests are needed to reach a positive conclusion in advance. Specific data are summarized in Figs. 2, 3 and Table 4.

Fig. 2
figure 2

Forest plot of mortality and tocilizumab treatment COVID-19 patients

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Fig. 3
figure 3

Trial sequential analysis of mortality and tocilizumab treatment COVID-19 patients

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Table 4 The mortality and risk of infection of tocilizumab treatment COVID-19 patients
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Secondary Infection Risk

No significant associations were observed between tocilizumab and an elevated secondary infection risk in the overall analysis. However, we found significantly increased secondary infection risk after COVID-19 patients received tocilizumab in the dose of 400–800 mg subgroup (OR 1.43, 95% CI 1.06–1.92, P = 0.018), dose of ≤ 400 mg subgroup (OR 1.92, 95% CI 1.40–2.63, P < 0.001), retrospective observational study subgroup (OR 2.00, 95% CI 1.15–3.47, P = 0.013), and case-control study subgroup (OR 1.98, 95% CI 1.14–3.45, P = 0.016). In addition, there was an edge effect in the RCT subgroup (OR 0.79, 95% CI 0.61–1.03, P = 0.079). Figure 4 and Table 4 summarize the data associated with tocilizumab and secondary infection risk.

Fig. 4
figure 4

Forest plot of safety of tocilizumab treatment COVID-19 patients. a Forest plot of tocilizumab and secondary infection risk in COVID-19 patients. b Forest plot of tocilizumab and discharge in COVID-19 patients. c Forest plot of tocilizumab and adverse events in COVID-19 patients. d Forest plot of tocilizumab and mechanical ventilation in COVID-19 patients

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Discharge

We also failed to find significantly increased discharge after COVID-19 patients received tocilizumab in the overall analysis (OR 1.13, 95% CI 0.98–1.32, P = 0.100). We revealed significantly increased discharge in tocilizumab treatment COVID-19 patients in the cohort study subgroup (OR 1.32, 95% CI 1.06–1.65, P = 0.014). We revealed significantly decreased discharge in tocilizumab treatment COVID-19 patients in the dose of 400–800 mg subgroup (OR 0.88, 95% CI 0.80–0.98, P = 0.018). However, we also found an edge effect in Caucasian subgroup analysis (OR 1.24, 95% CI 1.00–1.55, P = 0.051), the no specific dose subgroup (OR 1.82, 95% CI 0.95–3.47, P = 0.069), case-control study subgroup (OR 1.37, 95% CI 1.00–1.89, P = 0.051), journal of unpublished subgroup (OR 0.91, 95% CI 0.0.82–1.00, P = 0.055), journal of published subgroup (OR 1.18, 95% CI 0.99–1.41, P = 0.060), and case size of < 100 subgroup (OR 1.19, 95% CI 0.99–1.44, P = 0.060). Specific data are summarized in Fig. 4 and Table 5.

Table 5 The rate of discharge, adverse events and mechanical ventilation of tocilizumab treatment COVID-19 patients
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Adverse Events and Mechanical Ventilation

No significant association was found between tocilizumab and adverse events and mechanical ventilation in COVID-19 patients in the overall analysis. We found significantly increased adverse events risk in tocilizumab treatment COVID-19 patients in the RCT subgroup (OR 1.32, 95% CI 1.00–1.74, P = 0.049). Subgroup analyses were performed to clarify the effects of potential ethnicity, disease severity, drug dose, study type, and case size and whether the article is officially published. There was no significant association between tocilizumab treatment and estimated risk of adverse events and mechanical ventilation, as shown in Fig. 4 and Table 5.

Publication Bias and Sensitivity Analysis

We performed Egger's test and Begg's funnel plot to assess the publication bias of the meta-analysis. We also conducted sensitivity analysis by omitting one study at a time when calculating summary results. Although the size of the sample of cases in all included studies varied, corresponding pooled ORs and 95%CIs did not qualitatively change with or without studies on small pieces.

Discussion

The World Health Organization (WHO) announced COVID-19 may progress to a pandemic associated with substantial morbidity and mortality and is a public health emergency of globalized concern as of 1 February 2020 [1, 3, 12]. At the time of this writing, over 174 million laboratory-diagnosed COVID-19 patients had been reported spanning 212 countries and regions and contributing to > 3,730,000 death.

SARS-CoV-2 brings about a broad spectrum of clinical manifestations, ranging from asymptomatic or paucisymptomatic forms (with malaise, myalgia, dry cough, and fever) to full-blown viral pneumonia ARDS, multiorgan failure, and death [2, 25]. The serum cytokine profiles of some moderate to severe COVID-19 patients overlap with secondary hemophagocytic lymphocytosis (sHLH) and macrophage activation syndrome (MAS). Viruses are known as solid triggers of MAS/sHLH, and serum ferritin levels are associated with mortality in MAS and COVID-19 patients. Endogenous IL-1 is a proinflammatory cytokine that induces the production of IL-6 by macrophages and monocytes and is elevated in MAS, COVID-19 disease, and other diseases, such as severe chimerical antigen receptor T-cell (CAR-T)-mediated cytokine release syndrome (CRS) [2, 26,27,28].

IL-6 inhibitors or their receptor inhibitors have been successfully treated with other cytokine storm syndromes or CRS secondary to CAR T-cell therapies. We already have several drug options available, including IL-6 inhibitors (siltuximab, sirukumab, clazakizumab) and IL-6 receptor inhibitors (tocilizumab, sarilumab). It is noteworthy that tocilizumab has been officially included in the National Health Commission of the People's Republic of China COVID-19 Guidelines for diagnosis and treatment program (7th edition) since March 2020: "Tocilizumab can be used in COVID-19 patients with extensive ground-glass lesions opacity in bilateral lungs or critically ill COVID-19 patients, who have elevated laboratory detected serum IL-6 levels" [2]. The Infectious Diseases Society of America (IDSA) has also recently published guidelines and suggested that tocilizumab should only be used in clinical trials of hospitalized COVID-19 patients because of the lack of reliable clinical treatment data [2].

The Infectious Diseases Society of America (IDSA) has also recently published guidelines and suggested that tocilizumab should only be used in clinical trials of hospitalized COVID-19 patients because of the lack of reliable clinical treatment data [1, 11, 12]. However, several retrospective observational studies have found that, in addition to standard treatment, tocilizumab is a safe and promising treatment to prevent disease progression in hospitalized COVID-19 patients with moderate and hyper-inflammation [13,14,15,16, 28,29,30]. Our case-control study also found a lower mortality rate in the tocilizumab treatment group than in the standard treatment group (9.47% versus 16.84%), but the results were not statistically significant. However, we found that tocilizumab significantly decreased mortality and increased discharge in COVID-19 patients but no increased secondary infection risk, adverse event, and mechanical ventilation in a meta-analysis of 49 studies (6568 cases and 11,660 controls). We additionally found similar results in several subgroups. Therefore, our data suggest that clinicians should pay attention to tocilizumab therapy as an effective and safe treatment for COVID-19 patients.

Some limitations of the study need to be noted. First, in the absence of clinical test data of every patient, it is not clear which patients with high clinical indicators will benefit most when treated with tocilizumab. Second, subgroup analyses involved relatively small groups, which may not provide sufficient statistical power to explore accurate correlations. Third, every doctor has a different treatment for clinical diagnostics, which would allow for adjustment by other factors. Finally, the inclusion of zero-event trials can sometimes reduce effect size estimates and narrow confidence intervals.

Conclusion

To our knowledge, it is the systematic review and meta-analysis to investigate the efficacy and safety of tocilizumab treatment in COVID-19 patients in the the biggest sample size. Tocilizumab significantly decreased mortality in COVID-19 patients but no increased discharge, secondary infection risk, adverse event, and mechanical ventilation in a meta-analysis. Our data suggest that clinicians should pay attention to tocilizumab therapy as an effective and safe treatment for COVID-19 patients.