Key Points
Tocilizumab could prolong survival among hospitalized patients with severe COVID-19.
Tocilizumab weakens the inflammatory response while sustaining immune responses.
During the tocilizumab treatment, no severe adverse drug reactions were reported.
Abstract
The coronavirus disease 2019 (COVID-19) has caused a global pandemic, resulting in considerable morbidity and mortality. Tocilizumab, an inhibitor of IL-6, has been widely repurposed as a treatment of severely ill patients without robust evidence supporting its use. In this study, we aimed to systematically describe the effectiveness of treatment and prevention of the cytokine storms in COVID-19 patients with tocilizumab. In this multicentered retrospective and observational cohort study, 65 patients with COVID-19 receiving tocilizumab and 130 not receiving tocilizumab were propensity score matched at a ratio of 2:1 based on age, sex, and comorbidities from January 20, 2020 to March 18, 2020 in Wuhan, China. After adjusting for confounding, the detected risk for in-hospital death was lower in the tocilizumab group versus nontocilizumab group (hazard ratio = 0.47; 95% confidence interval = 0.25–0.90; p = 0.023). Moreover, use of tocilizumab was associated with a lower risk of acute respiratory distress syndrome (odds ratio = 0.23; 95% confidence interval = 0.11–0.45; p < 0.0001). Furthermore, patients had heightened inflammation and more dysregulated immune cells before treatment, which might aggravate disease progression. After tocilizumab administration, abnormally elevated IL-6, C-reactive protein, fibrinogen, and activated partial thromboplastin time decreased. Tocilizumab may be of value in prolonging survival in patients with severe COVID-19, which provided a novel strategy for COVID-19–induced cytokine release syndrome. Our findings could inform bedside decisions until data from randomized, controlled clinical trials become available.
Introduction
Coronavirus disease 2019 (COVID-19) has caused a global pandemic as a clinical syndrome caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (1). By August 18, 2020, the number of deaths had climbed to 767,158 among 21,549,706 confirmed cases in World Health Organization reports (2). According to a report, the mortality for critical cases reached 60.5% (3). The elevated inflammatory cytokines suggest that cytokine release syndrome (CRS) plays a major role in the pathology of COVID-19 (4, 5).
Although the current focus has been on the development of novel therapeutics, including antivirals and vaccines, there is still a long way to go before the vaccine is officially launched on the market. Before that, research is under way to repurpose medications. To dampen excessive serum inflammatory mediators, interest has increased in the use of anti-inflammatory agents. However, corticosteroids have short- and long-term adverse reactions (6), and plasmapheresis or continuous renal replacement therapy either requires specific equipment or lacks documented efficacy (7).
A better understanding of the underlying pathogenesis in CRS facilitates the design of immunotherapies. IL-6 is the key molecule of CRS, so IL-6R antagonist may be of value in improving outcomes (8, 9). Tocilizumab is a recombinant humanized monoclonal anti–IL‐6R Ab (10) that has been used worldwide in various rheumatic diseases and severe CAR T cell–induced CRS (11, 12). Given the pivotal role of IL-6 in COVID-19 and the efficacy of tocilizumab in CRS, tocilizumab was included for the first time in Diagnosis and Treatment Protocol for Novel Coronavirus Pneumonia (seventh edition) sponsored by National Health Commission of the People’s Republic of China. However, because of the small sample sizes of previous studies, there are insufficient data to support the efficacy of the tocilizumab in patients with COVID-19. To further provide a therapeutic strategy for this fatal disease, ultimately curbing the rising fatality rate of COVID-19, this multicenter, retrospective, observational study presents the clinical details of patients receiving tocilizumab from three hospitals in Wuhan, China.
Materials and Methods
Study design and participants
This multicenter, retrospective, cohort study was conducted in three hospitals in Wuhan, China that were designated centers for COVID-19 treatment: Tongji Hospital, Wuhan Pulmonary Hospital, and Renmin Hospital of Wuhan University (the east campus). We used the following inclusion and exclusion criteria to determine the study cohort. The inclusion criteria included all adult patients (aged ≥18 y old, 5235 patients) with COVID-19, who were admitted to the above-mentioned hospitals in Hubei, China from January 20, 2020 to March 18, 2020. Eligibility criteria for tocilizumab administration were as follows: a diagnosis of COVID-19 confirmed upon RT-PCR positivity for SARS-CoV-2; patients with extensive lung lesions; severe cases who also show an increased level of IL-6 in laboratory testing. Exclusion criteria were as follows: incomplete medical records (e.g., transfer to any other hospital), evidence of concomitant bacterial infection, and pregnancy.
After quality control in clinical data, 65 patients using tocilizumab (B2084B21; Roche Pharma) were ultimately enrolled, and a total of 130 patients not taking tocilizumab were statistically matched by propensity score matching (13) at a ratio of 2:1, based on age, sex, and comorbidities. The comorbidities, including hypertension, diabetes, tumor, coronary heart disease, chronic obstructive pulmonary disease, cerebral infarction, liver cirrhosis, hepatitis, and tuberculosis, were used as matching factors in this study. These comorbidities have been reported to be risk factors for severity or death of COVID-19 (14, 15). The date of final follow-up was April 14, 2020.
For diagnosis, patients were assessed for eligibility on the basis of a positive RT-PCR assay (Shanghai Zhijian Biotechnology or Sansure Biotech) for SARS-CoV-2 in a respiratory tract sample tested by the local Center for Disease Control or by a designated diagnostic laboratory.
This study was approved by the Ethics Committee of Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology (TJ-C20200108) and granted a waiver of informed consent from study participants.
Data collection
Epidemiological, clinical, radiological, laboratory, clinical treatments, and clinical outcomes data of all patients with laboratory-confirmed SARS-CoV-2 were obtained with data collection forms from electronic medical records of Tongji Hospital, Wuhan Pulmonary Hospital, and Renmin Hospital of Wuhan University (the east campus). The admission and in-hospital data of these patients were collected, reviewed, and verified by a trained team of physicians to guarantee the accuracy of the data extraction procedures. Any missing or uncertain records were collected and clarified through communication with involved health care providers and their families. The detailed and standardized information of demographic data, comorbidities, initial symptoms and vital signs were recorded or diagnosed at hospital admission. The chest computed tomography (CT) was recorded at hospital admission and after treatment. The complications, treatments, clinical outcomes, and hospital length of stay were monitored until April 14, 2020, the final data of follow-up. Laboratory examinations, including blood routine, immune cells subsets, inflammatory or infection-related cytokines and biomarkers, and cardiac/renal/liver/coagulation function tests, were detected on the last diagnosed date from laboratory information system.
Outcomes
The primary end point was in-hospital death. The main secondary outcomes were total days in the intensive care unit (ICU), the time from admission to discharge, and complications during hospitalization. Acute respiratory distress syndrome (ARDS) was defined according to the Berlin definition (16). Disseminated intravascular coagulation (DIC) was diagnosed by increased levels of platelets, clotting factors, and other blood components (17). Acute renal injury was identified according to the Kidney Disease: Improving Global Outcomes clinical practice guidelines (18). Acute liver damage was diagnosed by progressively elevated levels of alanine transaminase (ALT), aspartate aminotransferase (AST), or bilirubin. If the serum levels of cardiac biomarker high-sensitivity cardiac troponin I (hs-cTnI) were above the 99th percentile upper reference limit or new abnormalities were shown in electrocardiography and echocardiography, the acute cardiac injury was defined (19).
Safety outcomes included adverse events that occurred during treatment. Adverse events were classified according to the National Cancer Institute Common Terminology Criteria for Adverse Events, version 4.0.
The onset of COVID-19 was defined as the time point when the symptoms were first noticed. Patients receiving tocilizumab during hospitalization were classified as the tocilizumab group. Patients who did not receive tocilizumab during hospitalization were classified as the nontocilizumab group. The criteria for discharge were an absence of fever for at least 3 d, substantial improvement in respiratory symptoms, and both lungs from chest CT and two throat-swab samples negative for SARS-CoV-2 RNA obtained at least 24 h apart (14). In this study, there were no cases lost to follow-up attributed to standardized government management and close tracking for the COVID-19 pandemic. The illness severity of COVID-19 was defined according to the criteria defined by the Diagnosis and Treatment Protocol for Novel Coronavirus Pneumonia (sixth interim edition) sponsored by National Health Commission of the People’s Republic of China.
Statistical analysis
Continuous variables were presented as median and interquartile range (IQR) or mean and SD. Categorical variables were expressed as a number (percentage). Differences between the tocilizumab group and the nontocilizumab group were compared. For continuous variables, a Student t test was used for normal distributed data and a Mann–Whitney U nonparametric test was used for nonnormal distributed continuous data. The Pearson χ2 test, Pearson χ2 test with Yates continuity correction, or Fisher exact test were applied for categorical variables. Time to events (discharge or death) were defined as the time from hospital admission to events. A Cox proportional hazards model was fitted for time to death, controlling for treatment group and potential confounders, including age, gender, and comorbidities. Univariable and multivariable logistic regression models were employed to estimate odds ratios (ORs) and 95% confidence intervals (CIs), adjusting for age, sex, and comorbidities. A two-sided p < 0.05 was considered statistically significant. All statistical analyses were performed using R (3.6.0) or SPSS Statistics (22.0).
Results
This study cohort included 195 COVID-19 patients who were admitted to Tongji Hospital, Wuhan Pulmonary Hospital, and Renmin Hospital of Wuhan University (the east campus) during January 20, 2020 through March 18, 2020. Among these patients with COVID-19, 65 were classified as the tocilizumab group (71.0 y old [IQR 63.0–75.0]; 73.85% men), and 130 patients were classified as the nontocilizumab group (67.5 y old [IQR 61.0–75.0]; 63.08% men) according to the medication used during the hospitalization.
The characteristics of the tocilizumab group versus the nontocilizumab group on admission were provided in Supplemental Table I and Table I. In terms of age, gender, comorbidities, symptoms, and demographic characteristics (CT) of these patients, no significant differences were observed between these two groups. Compared with the nontocilizumab group, the tocilizumab group had higher level of D-dimer and urea. In the tocilizumab group, tocilizumab (B2084B21; Roche Pharma) was initiated at a median of 15 d (IQR 4.0–21.5) following admission. Tocilizumab was administered at a dose of 4–8 mg/kg body weight, and the recommended dose was 400 mg through an i.v. drip up to a maximum of 800 mg. Dilution was to 100 ml with 0.9% normal saline, and the infusion time was more than 1 h. In case of fever within 12 h, an additional dose was given, and the cumulative dose could not be given more than two times. A third infusion, 24 h apart from the second, was optional, based on clinical response. Additional information about dosing and administration appears in Supplemental Table II. In terms of other in-hospital treatment, there were no significant differences in both groups, suggesting that the different clinical outcomes were mainly triggered by the tocilizumab treatment (Supplemental Table III).
Primary outcomes
During a follow-up duration, 56 died out of the 195 patients (28.72%) with COVID-19. The risk of in-hospital proportion of death was lower in tocilizumab group versus nontocilizumab group (21.54% [14/65] versus 32.31% [42/130]; p = 0.12) (Table II). In the Cox proportional hazard model, after adjusting for age, gender, and comorbidities, use of tocilizumab was associated with lower in-hospital proportion of death (hazard ratio [HR] = 0.47; 95% CI = 0.25–0.90; p = 0.023) (Fig. 1). In our study, the adjusted HR for an association of known variables for in-hospital proportion of death due to COVID-19 were 1.82 (95% CI = 1.01–3.27; p = 0.047) for hypertension and 3.25 (95% CI = 1.27–8.30; p = 0.014) for tuberculosis.
Survival of COVID-19 patients during hospitalization. Kaplan–Meier curves for cumulative p value of COVID-19 mortality during follow up duration in tocilizumab or non-tocilizumab cohort among 195 patients within Cox proportional hazards model.
Secondary outcomes
Total days in the ICU in the tocilizumab group are shorter than those in the nontocilizumab group (10.00 versus 12.00 d; p = 0.27), and the duration from admission to hospital discharge was significantly longer (40.00 versus 26.50 d; p = 0.001) (Table II).
SARS-CoV-2 infection can arouse both pulmonary and multisystem inflammation, leading to critical complications. In this study, we observed that the incidence of ARDS (36.92 versus 70.77%; p < 0.0001) was lower in the tocilizumab group than in the nontocilizumab group (Table II). In the multivariable logistic regression models, use of tocilizumab was associated with lower risk of ARDS (OR = 0.23; 95% CI = 0.11–0.45; p < 0.0001) (Table III). These data suggest that IL-6 may be a potential actionable target cytokine to treat COVID-19–related ARDS and that tocilizumab is effective in reducing the incidence of ARDS.
Laboratory test results
Considering that CRS refers to an uncontrolled and overwhelming release of proinflammatory mediators by an overly activated immune system, we analyzed the difference between the tocilizumab group and the nontocilizumab group based on the levels of inflammatory cytokines and immune cells subsets after treatment (Table II). Analysis revealed that the infection-related biomarkers, including IL-10 (5.00 versus 7.35 pg/ml; p = 0.013) and C-reactive protein (CRP; 1.52 versus 22.55 mg/l; p < 0.0001) were remarkably decreased in the tocilizumab group compared with the nontocilizumab group (Table II). Consistent with recently published studies, results revealed that CRS-related cytokines, especially CRP, were rapidly reduced in patients with severe COVID-19 after receiving tocilizumab (20, 21). In contrast, the count of CD3+ T cells (608.29 versus 300.00/μl; p = 0.001) was significantly increased in tocilizumab group than that in the nontocilizumab group (Table II). For further analysis of T cell subsets, we found that the count of CD4+ T cells (395.00 versus 305.00/μl; p = 0.064) and CD8+ T cells (256.98 versus 78.00/μl; p = 0.003) was increased as well as the total number of T cells (Table II). These findings indicate that COVID-19 patients using tocilizumab have more improved inflammation and immune cell function recovery than those who did not. The dynamic change of four indices over follow-up are shown in the Fig. 2. After the patient was admitted to the hospital, the level of CRP increased, whereas CD3+ T cell and CD8+ T cell counts declined in both groups as the disease progressed. After tocilizumab treatment, CRP decreased from 60.85 to 1.52 mg/l in tocilizumab group, and the number of immune cells was higher than the baseline, especially in the tocilizumab group. The difference did not reach statistical significance, but it presented a statistical trend, which may be attributed to the limited sample size and short follow-up time. Noticeably, we observed that CRP and T cell numbers appeared as a significant change in tocilizumab group at week 7 compared with the control group. It is warranted to evaluate the effect of tocilizumab in larger scale prospective cohort studies and randomized controlled trials.
Temporal changes in laboratory parameters in COVID-19 patients after admission. The temporal changes of hypersensitive CRP (hs-CRP) (A), CD3+ T cell (B), CD8+ T cell (C), and lymphocyte (D) in tocilizumab group and nontocilizumab group. These parameters were measured at 1, 2, 3, 4, 5, 6, and 7 wk after admission. The green dotted line represents the lower limit of normal, and the red dotted line represents the upper limit of normal. The levels of these parameters at each point were expressed as median and IQR. **p < 0.01, ***p < 0.001 were calculated by Mann–Whitney U test for last examination.
We also evaluated the dynamic changes of organ damage indices at final examination (Table II). Biomarkers of multiple organ dysfunction in the tocilizumab group were within the normal range. After the treatment with tocilizumab, the activated coagulation system by IL-6 returned to normal. Activated partial thromboplastin time (APTT) was shorter than in the nontocilizumab group (36.80 versus 42.30 s; p = 0.006), and the decline of fibrinogen (2.57 versus 4.71 g/l; p < 0.0001) was more pronounced in tocilizumab group (Table II).
Adverse event
The percentages of patients with adverse reactions were similar in the two groups; there were significant differences (Supplemental Table IV). The most common adverse event in the tocilizumab group was increasing liver enzymes (AST, 8/65 [12.31%]; ALT, 9/65 [13.85%]) as previously reported (22).
Discussion
In this multicenter retrospective study involving a modest sample of consecutive patients who had been hospitalized with COVID-19, the risk of in-hospital proportion of death was significantly lower among patients who received tocilizumab than among those who did not. It revealed that tocilizumab could prolong survival among patients with COVID-19, specifically among hospitalized COVID-19 patients. Clinical data showed that tocilizumab treatment weakens the inflammatory response while sustaining immune responses in posttreatment COVID-19 patients, suggesting that tocilizumab could be an efficient therapeutic for the treatment of COVID-19. Although it is plausible that unmeasured confounding factors may have contributed to the observed protective association, these data suggested that in-hospital use of tocilizumab was not associated with increased proportion of death in COVID-19. These findings provide clinical evidence in support of recently published guidance statements by National Health Commission of the People’s Republic of China to continue tocilizumab in patients with severe or critical COVID-19 (14, 23). Given the observational design, whether tocilizumab could reduce overall mortality in patients with COVID-19 needs further validation in geographically diverse, large-scale prospective cohort studies.
CRS was found to be the major cause of morbidity in patients infected with severe SARS-CoV and MERS-CoV (8). Elevated serum concentrations of the IL-6 are hallmarks of severe MERS-CoV infections (24). Elevated serum CRP, a protein whose expression is driven by IL-6, is also a biomarker of severe β-coronavirus infection. Recent studies have also reported that hypercytokinemia is associated with a higher proportion of death in patients with severe COVID-19. IL-6 is an excellent biomarker of severity and a prognostic indicator for most of diseases presenting with a cytokine storm and is expressed longer than TNF-α and IL-1 (25). Although IL-6 is regulated strictly through transcription and posttranscription mechanisms, dysregulated, persistent production of IL-6 plays a pathological role in tissue hypoxia, hypotension, DIC, and multiple organ dysfunction (26–29). Mechanistically, IL-6 is essential for the generation of Th17 cells in the dendritic cell–T cell interaction (30). The excessive IL-6 may explain the overly activated Th17 cells observed in COVID-19 patients (31). A high level of IL-6 is associated with poor outcome in the setting of COVID-19 pneumonia (32). Accumulating evidence evoked the use of tocilizumab in COVID-19 infection. Tocilizumab, an IL-6R monoclonal blocking agent, was approved for the treatment of rheumatoid arthritis in Japan (2008), Europe (2009), and the United States (2010) (4, 33–35). Mechanistically, tocilizumab can bind both soluble and membrane-bound IL-6R to inhibit IL-6–mediated cis- and trans-signaling (10). A new study found that the inhibition of IL-6 signaling by tocilizumab treatment decreased PAI-1 production and improved the vascular endothelial functions in patients with severe COVID-19. IL-6 trans-signaling forms a positive feedback loop and plays pivotal roles in endothelial cell injury and coagulopathy, thereby mediating systemic inflammation and deteriorating systemic circulation (36). A phase II trial is ongoing in Italy (37), and a phase III trial was approved by the Food and Drug Administration (38) to assess the effect of tocilizumab for severe COVID-19 pneumonia. More than 1 million patients worldwide have been treated with tocilizumab, and clinical trials have proved that tocilizumab is safe for both pediatric and adult patients (22). In the mainly rheumatologic indications, the tolerance of tocilizumab is generally good, the main adverse events are a transient decrease in leukocytes, an increase in liver enzymes, and a slight increase of bacterial infection (22).
In COVID-19 patients with elevated inflammatory cytokines, postmortem pathology has revealed tissue necrosis and interstitial macrophage and monocyte infiltrations in the lung, heart, and gastrointestinal mucosa (22). Moreover, severe lymphopenia with hyperactivated proinflammatory T cells and decreased regulatory T cells are commonly seen in critically ill patients, suggesting dysregulated immune responses. In our study, 65 patients had a history of routine treatment for ∼15 days before tocilizumab treatment. A lower percentage of lymphocytes was found in patients, and it returned to normal when tocilizumab was given. At the same time, patients deteriorated with increased inflammatory response (inflammatory cytokines were elevated [e.g., IL-6, CRP]) and decreased immune function (immune cells decreased [e.g., CD4+ T cell, CD8+ T cell]) before tocilizumab. After the treatment, in addition to partially rescuing the immune dysregulation, the inflammatory response was weakened to some degrees in the patients. During the treatment, no severe adverse drug reactions were reported. Clinical symptoms of all patients improved with good prognosis after the treatment. Overall, these findings suggested that tocilizumab group seemed to have an improved survival outcome that might be explained by the blocking of IL-6–associated dysregulated immune responses and inflammatory storm response.
Our study has several limitations. First, this retrospective study population is derived from three hospitals in Hubei Province, but the effects of tocilizumab may vary among people of different races or geographic locations, which seems reasonable. Second, the potential mechanisms of dysregulated inflammatory cytokines and immune responses were not fully explored and need to be further investigated. Third, the sample size of the study was modest and included 65 patients who received tocilizumab. Currently, the sample size enrolled in case-control study was the largest. Because unmeasured biases are particular problems inherent in retrospective studies, we adjusted for likely confounders, including age, sex, and comorbidities in our analysis. Despite this extensive adjustment, it is still possible that some amount of unmeasured confounding remains. Therefore, large-scale prospective cohort studies and randomized controlled trials are needed to better understand the efficacy of tocilizumab in COVID-19. Recently a randomized, double-blind, placebo-controlled trial indicated that tocilizumab had no significant effect on the risk of intubation or death (39). However, this study states that because of the width of the CIs for efficacy comparisons, it cannot exclude the possibility that tocilizumab is associated with either some benefit or harm in some patients. Reported but still unpublished results of a small number of other randomized trials show that time to hospital discharge was shorter in patients treated with Actemra/RoActemra (tocilizumab) than in those treated with placebo (40). At the same time, our results suggest that tocilizumab has a week effect on survival among patients with COVID-19, specifically hospitalized COVID-19 patients. It is worth noting the limitations of our research; larger scale prospective cohort studies and extended follow-up time are warranted.
In summary, tocilizumab effectively improves clinical symptoms and represses the deterioration of patients with severe COVID-19. In our study, inpatient treatment with tocilizumab was associated with a lower risk of in-hospital proportion of death compared with tocilizumab nonusers. Although study interpretation needs to consider the potential for residual confounders, it is unlikely that inpatient tocilizumab would be associated with an increased risk of mortality. Noticeably, these results are consistent with those reported by other investigators (Refs. 41 and 42, N. Wadud, N. Ahmed, M. Mannu Shergil, M. Khan, M.G. Krishna, A. Gilani, S. El Zarif, J. Galaydick, K. Linga, S. Koor, et al., manuscript posted on medRxiv, DOI: 10.1101/2020.05.13.20100081; and C.A. Rimland, C.E. Morgan, G.J. Bell, M.K. Kim, T. Hedrick, A. Marx, B. Bramson, H. Swygard, S. Napravnik, J.L. Schmitz, et al., manuscript posted on medRxiv, DOI: 10.1101/2020.05.13.20100404), suggesting that these findings can be extrapolated to other populations or countries. Therefore, tocilizumab appears to be an effective treatment in patients with severe COVID-19, which provides a new therapeutic strategy for this fatal infectious disease.
Disclosures
The authors have no financial conflicts of interest.
Acknowledgments
We acknowledge all patients and families involved in the study and all health care workers who are fighting the campaign against COVID-19.
Footnotes
This work was supported by the SARS-CoV-2 Pneumonia Emergency Technology Public Relations Project of Tongji Medical College, Huazhong University of Science and Technology (Grant 2020kfyXGYJ043) and the National Key Research and Development Plan for the Emergency Management of Novel Coronavirus Pneumonia, China (Grant 2020YFC0845100).
The online version of this article contains supplemental material.
Abbreviations used in this article:
- ALT
- alanine transaminase
- APTT
- activated partial thromboplastin time
- ARDS
- acute respiratory distress syndrome
- AST
- aspartate aminotransferase
- CI
- confidence interval
- COVID-19
- coronavirus disease 2019
- CRP
- C-reactive protein
- CRS
- cytokine release syndrome
- CT
- computed tomography
- DIC
- disseminated intravascular coagulation
- HR
- hazard ratio
- hs-cTnI
- high-sensitivity cardiac troponin I
- ICU
- intensive care unit
- IQR
- interquartile range
- OR
- odds ratio
- SARS-CoV-2
- severe acute respiratory syndrome coronavirus 2.
- Received August 26, 2020.
- Accepted November 20, 2020.
- Copyright © 2021 by The American Association of Immunologists, Inc.
This article is distributed under The American Association of Immunologists, Inc., Reuse Terms and Conditions for Author Choice articles.
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