Tocilizumab treatment leads to early resolution of myeloid dysfunction and lymphopenia in patients hospitalized with COVID-19

Tocilizumab, an anti-interleukin-6 receptor inhibitor, is recommended in global treatment guidelines for patients hospitalized with severe COVID-19. Using proteomic and transcriptomic analysis, we characterized the immune profile and identified cellular and molecular pathways directly modified by tocilizumab in peripheral blood samples collected from patients enrolled in the COVACTA study, a phase 3, randomized, double-blind, placebo-controlled trial, to assess the efficacy and safety of tocilizumab in hospitalized patients with severe COVID-19 pneumonia. We identified factors predicting disease severity and clinical outcomes, including markers of inflammation, lymphopenia, myeloid dysfunction, and organ injury. Proteomic analysis confirmed a pharmacodynamic effect for tocilizumab. Transcriptomic analysis revealed that tocilizumab treatment leads to faster resolution of lymphopenia and myeloid dysfunction associated with severe COVID-19, thus defining an anti-inflammatory mechanism of action for the beneficial effects of tocilizumab in patients hospitalized with COVID-19. One sentence summary Interleukin-6 receptor blockade with tocilizumab accelerated resolution of myeloid dysfunction and lymphopenia in patients hospitalized with COVID-19