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The COVID‐19 pandemic caused by new betacoronavirus SARS‐Cov‐2 demands rapid exploration of safe and effective therapeutic options. In this perspective, “drug repurposing” aims to represent a rapid and valuable strategy. In the last decades, the endogenous gasotransmitter hydrogen sulfide (H2S) has emerged as a ubiquitous modulator of several biological functions. Early studies pointed out its importance in the regulation of numerous biological functions and systems. Accordingly, H2S deficiency has been associated with several disorders, and many chemotypes of H2S‐releasing agents have been developed as potential therapeutic tools for diseases related with impaired H2S production/activity. Some of these compounds are in advanced clinical trials. Presently, the pivotal role of H2S in modulating the inflammatory response and proinflammatory cytokine cascade is well recognized, and the usefulness of some H2S‐donors for the treatment of different forms of acute lung inflammation (due to infectious and non‐infectious etiologies) has been reported. More recent evidence is also unravelling several mechanisms of action which may account for antiviral effects of this gasotransmitter. Noteworthy, some preliminary clinical results suggest an inverse relationship between endogenous H2S levels and severity of COVID‐19 disease. Therefore, repurposing of H2S‐releasing drugs may be worthy of investigation as potential therapeutic opportunities for treatment of COVID‐19 disease.

Severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) is a newly identified coronavirus which has spread from China to the rest of the world causing the pandemic coronavirus disease 19 (COVID‐19). It has fatality rate that floats from 5 to 15% and the symptoms are fever, cough, myalgia and/or fatigue up to dyspnea, responsible for hospitalization and in most of the cases of artificial oxygenation. In the attempt to understand how the virus spreads and how to pharmacologically abolish it, it was highlighted that SARS‐CoV‐2 infects human cells by means of angiotensin converting enzyme 2 (ACE2), transmembrane protease serine 2 (TMPRSS2) and SARS‐CoV‐2 main protease (Mpro). Once bound to its receptor ACE2, the other two proteases, in concert with the receptor‐mediated signaling, allow virus replication and spread throughout the body. Our attention has been focused on the role of ACE2 in that its blockade by the virus increases Bradykinin and its metabolites, well known to facilitate inflammation in the lung (responsible for cough and fever), facilitate both the coagulation and complement system, three mechanisms that are typical of angioedema, cardiovascular dysfunction and sepsis, pathologies which symptoms occur in COVID‐19 patients. Thus, we propose to pharmacologically block the kallikrein‐kinin system upstream bradykinin and the ensuing inflammation, coagulation and complement activation by means of lanadelumab, which is a clinically approved drug for hereditary angioedema.

Lopinavir combined with ritonavir were reported to benefit the patients with SARS by reducing the viral loads. However, in the latest clinical trials, no benefit was observed with lopinavir-ritonavir treatment beyond standard care in patients with COVID-19. We comment here that this disappointed result of clinical trial might result from the low volume of the lung distribution of lopinavir. The major reasons were listed below: 1) The binding affinity of ACE2 with SARS-CoV-2 spike protein is ~10- to 20-fold higher than the binding affinity of ACE2 with SARS-CoV spike protein, indicating that SARS-CoV-2 can enter AT2 cells in lung much easier than SARS-CoV. Therefore, the viral loads of SARS-CoV-2 might be much higher than viral loads of SARS-CoV in the lung tissue. 2) The concentration of lopinavir in the lung tissue was 1.18 μg equiv/ml in rats. The low volume of the lung distribution of lopinavir might not be enough to inhibit the coronavirus replication due to the high viral loads in the lung tissue. 3) In contrast, the concentration of chloroquine in the lung tissue was much higher (30.76 ± 0.85 μg equiv/ml) in rats, which might lead to its clinical and virologic benefits in the treatment of COVID-19 patients. Together, we proposed here that anti-SARS-CoV-2 drug repurposing studies should pay more attentions to the lung tissue distribution of antiviral drugs. The efficacy of antiviral drugs might depend on their lung tissue distributions

Severe pneumonia which shares several of the features of acute respiratory distress syndrome (ARDS) is the main cause of morbidity and mortality in Coronavirus disease 19 (Covid‐19) for which as of now there is no effective treatment. ARDS is caused and sustained by an uncontrolled inflammatory activation characterized by a massive release of cytokines (cytokine storm), diffuse lung edema, inflammatory cell infiltraton and disseminated coagulation. Macrophage and T lymphocyte dysfunction plays a central role in this syndrome. In several experimental in vitro and in vivo models, many of these pathophysiological changes are triggered by stimulation of the P2X7 receptor. We hypothesize that this receptor might be an ideal candidate to target in Covid‐19‐associated severe pneumonia.