The Efficacy of IL-6 Inhibitor Tocilizumab in Reducing Severe COVID-19 Mortality: A Systematic Review

Kaye, A. G.; Siegel, R.

Without proven, targeted therapies against SARS-CoV-2, it is crucial to counter the known pathophysiological causes of severe COVID-19, potentially utilizing existing drugs. Severe COVID-19 is largely the result of a dysregulated immune response characterized by lymphocytopenia, neutrophilia and critical hypercytokinemia, also called a cytokine storm. The IL-6 inhibitor tocilizumab (TCZ) could potentially suppress effects of the pro-inflammatory cytokine which drives the cytokine storm and thereby lower mortality from the disease. This systematic analysis aimed to investigate and synthesize existing evidence for the efficacy of TCZ in reducing COVID-19 mortality. PubMed and SearchWorks searches were performed to locate clinical studies with primary data on TCZ treatment for severe COVID-19. 9 case-control studies comparing mortality between TCZ and standard of care (SOC) were identified for a qualitative synthesis. In all of the studies, the odds ratio of mortality from COVID-19 pointed towards lower fatality with TCZ versus the SOC and a combined random effects odds ratio calculation yielded an odds ratio of 0.482 (p<0.001, 95% CI 0.326-0.713). Additionally, 12 uncontrolled trials were identified for a qualitative analysis producing a raw combined mortality rate of 13.6%. Results from the systematic analysis provide positive evidence for the potential efficacy of TCZ, validating the merit and need for ongoing clinical trials of the drug to treat severe COVID-19.