• Joseph Meletiadis, Sotirios Tsiodras, and Panagiotis Tsirigotis.
• Clinical Microbiology Laboratory, Attikon University Hospital, Medical School, National and Kapodistrian University of Athens, Athens, Greece. jmeletiadis@med.uoa.gr.
• Infect Dis Ther. 2020 Dec 1; 9 (4): 707-713.

AbstractThe severe respiratory insufficiency observed during COVID-19 infection may not be directly related to a cytopathogenic effect induced by the virus itself, but to an exaggerated and inappropriate immune response. In an effort to reduce the severity of organ dysfunction, including respiratory insufficiency, monoclonal antibodies (Mabs) that block the interleukin-6 receptor, such as tocilizumab, sarilumab, and siltuximab, are under investigation for the treatment of COVID-19. However, blocking of just one of the many cytokines involved in the inflammatory reaction may not slow down the magnitude of the process. Since timing is important, the immune deficiency induced by IL6 blockade at the late immunodeficiency phase of sepsis that follows the initial inflammatory response may be detrimental. Finally, monitoring the degree and duration of IL6 blockade may be challenging because of the long half-life of Mabs (2-3 weeks). Pro- and anti-inflammatory cytokines act through a common JAK-STAT signaling pathway, which can be inhibited by JAK-STAT inhibitors. Ruxolitinib, a tyrosine kinase inhibitor selective for JAK1, 2, blocks many pro- and anti-inflammatory cytokines including IL6. Ruxolitinib has favorable pharmacodynamics and an acceptable safety profile. The short half-life (4-6 h) of the drug offers the opportunity for ideal monitoring of the degree and duration of cytokine blocking, simply by the adjusting dose and duration of therapy. From a theoretical point of view, the balanced control of cytokine blockade throughout the course of the septic process should be the cornerstone of modern management. According to this hypothesis, maximization of blocking should be attempted at the phase of hyper-inflammation for preventing severe organ damage, while pro-inflammatory blockade should be minimized at the late phase of immunoparalysis for prevention of secondary infections. Based on the above considerations, we consider that the efficacy and safety of this drug deserves testing in the context of a controlled randomized trial.

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