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Cytokine release syndrome in severe COVID-19: Is tocilizumab effective?



A large amount of data suggest that mild or severe cytokine storms, accompanied by high expression of interleukin-6 (IL-6), occur in patients with severe coronavirus disease and can be an important cause of death. Blocking the signal transduction pathway of IL-6 is expected to become a new method for the treatment of patients with severe COVID-19, with the IL-6 inhibitor, tocilizumab (Actemra), poised to become an effective drug for these patients, according to the authors of a review published online in the International Journal of Antimicrobial Agents.

This scanning electron microscope image shows SARS-CoV-2 (yellow)—also known as 2019-nCoV, the virus that causes COVID-19—isolated from a patient in the U.S., emerging from the surface of cells (blue/pink) cultured in the lab. Courtesy NIAID-RML

The reviewers from China detailed the metabolic pathways and regulation of cytokine release syndrome, especially with respect to what is known about severe COVID-19, and discussed the results of recent trials with tocilizumab, which is currently used for treatment of CRS in a variety of cancers and other metabolic disorders.

Tocilizumab is a recombinant humanized monoclonal antibody against human IL-6 receptor of immunoglobulin IgG1 subtype and has been approved for the treatment of rheumatoid arthritis and systemic juvenile idiopathic arthritis. The antibody specifically binds soluble- and membrane-bound IL-6 receptors (sIL-6R and mIL-6R) and inhibits sIL-6R– and mIL-6R–mediated signal transduction. It has been shown to be effective in the treatment of severe CRS patients. In 2017, the U.S. Food and Drug Administration approved tocilizumab for the treatment of CRS caused by CAR-T (chimeric antigen receptor T-cell immunotherapy) therapy.

A small clinical trial in China examined the effectiveness of tocilizumab in 21 patients who met the criteria for severe or critical COVID-19, including respiratory failure requiring mechanical ventilation, shock, or admission to the ICU with other organ failure. After a few days of tocilizumab treatment, the body temperatures returned to normal (initially, all 21 patients had fevers), and all other symptoms were significantly improved, according to the authors. A total of 75% (15/20) of the patients reduced their oxygen intake, and 1 patient did not need oxygen. CT scanning showed that 90.5% (19/21) of the patients had absorption of pulmonary lesions, and lab tests showed that the proportion of peripheral blood lymphocytes and C-reactive protein in the patients returned to normal.

The main deficiency of the study was that only the level of IL-6 in peripheral blood before treatment with tocilizumab was reported (mean value, 132.38 ± 278.54 pg/mL), but the level of IL-6 following treatment was not given, according to the reviewers. Serum levels of IL-6 in normal patients are undetectable or very low.

Based upon their analysis of COVID-19’s possible mechanism and the small samples of clinical data available, tocilizumab appeared effective, and “we suggest that it should be used in critically ill COVID-19 patients with significantly elevated IL-6,” the authors stated.

“CRS occurs in a large number of patients with severe COVID-19, which is also an important cause of death. IL-6 is the key molecule of CRS, so IL-6R antagonist tocilizumab may be an important drug to save patients’ lives,” the researchers concluded.

This study was supported by China Mega-Project for Infectious Diseases and the China Mega-Project for Innovative Drugs. The authors reported that they had no conflicts.

SOURCE: Zhang C et al. Int J Antimicrobial Agents. 2020. doi. org/10.1016/j.ijantimicag.2020.105954.

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