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| - Background: Tocilizumab blocks pro-inflammatory activity of interleukin-6 (IL-6) which might be important in the pathogenesis of interstitial pneumonia. Objective: to evaluate efficacy of tocilizumab in COVID-19 pneumonia patients. Design: multicenter single-arm phase 2 trial, powered to detect 10% absolute lethality rate reduction at 14 and 30-days, with 20% and 35% expected rates. A consecutive prospective validation cohort was also evaluated. Setting: 185 Italian public hospitals, during coronavirus breakout. Patients: 1221 patients hospitalized with pneumonia, from March 19th to 24th, 2020. Intervention: tocilizumab 8 mg/kg, intravenously, one or two administrations with 12 hours interval. Measurements: lethality rates at 14 and 30-days; safety according to CTCAE. Results: 301 and 920 cases were available for intention-to-treat (ITT) analysis in phase 2 and validation cohorts. Due to delayed drug availability, 60% of patients received tocilizumab, and with some delays. In phase 2, 67 patients died; lethality rates were 18.4% (97.5%CI: 13.6-24.0, P=0.52) and 22.4% (97.5%CI: 17.2-28.3, P<0.001) at 14 and 30-days. Lower rates (15.6% and 20.0%) were reported in the modified ITT including only treated patients (mITT). Lethality rates in the validation cohort were smaller than in phase 2, at 14 and 30 days and in ITT and mITT populations. Multivariable logistic regression model suggests tocilizumab be more effective in patients not requiring mechanical respiratory support at baseline. No relevant signal of specific drug toxicity was reported, many severe adverse events being disease-related. Limitations: single-arm design. In addition, delayed availability of the drug induced indication bias and immortal time bias. Conclusion: Tocilizumab reduced lethality rate at 30 but not at 14-days, compared with the expectations, without significant toxicity. Efficacy was more evident among patients not requiring mechanical respiratory support.
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