question: BACKGROUND: Cytokine release syndrome is a serious complication of the new coronavirus infection (COVID-19). The aim of the study was to assess effectiveness and safety of the IL-17 antagonist nekatimab for its treatment. METHODS: The retrospective study included COVID-19 patients with C-reactive protein levels >60 mg/L. Patients received either netakimab (group NET), IL-6 antagonist tocilizumab (group TOC) or no anti-cytokine treatment (group CON). RESULTS: Forty-four patients were enrolled in the NET group, 27 patients in the TOC group, and 47 patients in the CON group. Mortality was lower in the NET group than in TOC and CON groups (2.3% vs. 14.8% and 31.9%; p = 0.018 and p < 0.001). NET group patients required intensive care unit admission (6.8% vs. 25.9% and 46.3%; p = 0.025 and p < 0.001) and mechanical ventilation (4.6% vs. 22.2% and 31.9%; p = 0.022 and p = 0.002) less frequently than patients of the TOC and CON groups. After 7–10 days of anti-cytokine drug administration, a reduction in lung lesion volume (p = 0.016) and an increase in the proportion of patients who did not need oxygen support (p = 0.005) or stayed in prone position (p = 0.044) was observed in the NET group only group; C-reactive protein levels were the same in the TOC and NET groups (p = 0.136) and lower in the CON group (p < 0.001 and p = 0.005). IL-6 levels decreased in the NET group (p = 0.005) and did not change in the TOC group (p = 0.953). There was no difference in the incidence of side effects between groups. CONCLUSION: The IL-17 antagonist netakimab is effective and safe in the treatment of cytokine release syndrome in COVID-19. ELECTRONIC SUPPLEMENTARY MATERIAL: Supplementary material is available in the online version of this article at 10.1684/ecn.2021.0463.