The novel coronavirus SARS-CoV-2 has become a global health concern. The morbidity and mortality of the potentially lethal infection caused by this virus arise from the initial viral infection and the subsequent host inflammatory response. The latter may lead to excessive release of pro-inflammatory cytokines, IL-6 and IL-8, as well as TNF-α ultimately culminating in hypercytokinemia (“cytokine storm”). To address this immuno-inflammatory pathogenesis, multiple clinical trials have been proposed to evaluate anti-inflammatory biologic therapies targeting specific cytokines. However, despite the obvious clinical utility of such biologics, their specific applicability to COVID-19 has multiple drawbacks, including they target only one of the multiple cytokines involved in COVID-19’s immunopathy. Therefore, we set out to identify a small molecule with broad-spectrum anti-inflammatory mechanism of action targeting multiple cytokines of innate immunity. In this study, a library of small molecules endogenous to the human body was assembled, subjected to in silico molecular docking simulations and a focused in vitro screen to identify anti-pro-inflammatory activity via interleukin inhibition. This has enabled us to identify the loop diuretic furosemide as a candidate molecule. To pre-clinically evaluate furosemide as a putative COVID-19 therapeutic, we studied its anti-inflammatory activity on RAW264.7, THP-1 and SIM-A9 cell lines stimulated by lipopolysaccharide (LPS). Upon treatment with furosemide, LPS-induced production of pro-inflammatory cytokines was reduced, indicating that furosemide suppresses the M1 polarization, including IL-6 and TNF-α release. In addition, we found that furosemide promotes the production of anti-inflammatory cytokine products (IL-1RA, arginase), indicating M2 polarization. Accordingly, we conclude that furosemide is a reasonably potent inhibitor of IL-6 and TNF-α that is also safe, inexpensive and well-studied. Our pre-clinical data suggest that it may be a candidate for repurposing as an inhaled therapy against COVID-19.

The potentially lethal infection caused by the novel Severe Acute Respiratory Disease Coronavirus-2 (SARS-CoV-2) has evolved into a global crisis. Following the initial viral infection is the host inflammatory response that frequently results in excessive secretion of inflammatory cytokines (e.g. , IL-6 and TNFα), developing into a self-targeting, toxic “cytokine storm” causing critical pulmonary tissue damage. The need for a therapeutic that is available immediately is growing daily but the de novo development of a vaccine may take years. Therefore, repurposing of approved drugs offers a promising approach to address this urgent need. Inhaled furosemide, a small molecule capable of inhibiting IL-6 and TNFα, may be an agent capable of treating the Coronavirus Disease 2019 cytokine storm in both resource-rich and developing countries. Furosemide is a “repurpose-able” small molecule therapeutics, that is safe, easily synthesized, handled, and stored, and is available in reasonable quantities worldwide.

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The potentially lethal COVID-19 infection caused by the novel Severe Acute Respiratory Disease Coronavirus-2 (SARS-CoV-2) has evolved into a global crisis. There are two major processes that lead to the morbidity and mortality of this disease: initially the viral infection, followed by a host inflammatory response that frequently results in excessive secretion of inflammatory cytokines (e.g. IL-6, IL-8, IL-10, TNFα), developing into a self-targeting toxic "cytokine storm" in which the lungs fill with inflammatory secretions causing critical pulmonary tissue damage. Even though the search for a vaccine and anti-viral agents has already been initiated, the de novo development of a safe, COVID-19 specific solution may take years; regrettably, the need for a therapeutic that is available immediately is growing daily. Therefore, repurposing an already approved drug offers a promising approach to address this urgent need. A truly effective therapeutic, however, should be available not only for the single individual in a developed country, but also for the many people in developing countries. As presented in this review, inhaled furosemide, a small molecule capable of inhibiting IL-6, IL-8 and TNFα within the lung, may be an agent capable of treating the COVID-19 cytokine storm in both resource-rich and developing countries. Furosemide is a "repurpose-able" small molecule therapeutic, that is safe, easily synthesized, handled and stored, and is available in reasonable quantities worldwide.