Intense effort is underway to evaluate potential therapeutic agents for the treatment of COVID-19. In order to respond quickly to the crisis, the repurposing of existing drugs is the primary pharmacological strategy. Despite the urgent clinical need for these therapies, it is imperative to consider potential safety issues. This is important due to the harm-benefit ratios that may be encountered when treating COVID-19, which can depend on the stage of the disease, when therapy is administered and underlying clinical factors in individual patients. Treatments are currently being trialled for a range of scenarios from prophylaxis (where benefit must greatly exceed risk) to severe life-threatening disease (where a degree of potential risk may be tolerated if it is exceeded by the potential benefit). In this perspective, we have reviewed some of the most widely-researched repurposed agents in order to identify potential safety considerations using existing information in the context of COVID-19.
In the search to rapidly identify effective therapies that will mitigate the morbidity and mortality of COVID-19, attention has been directed towards the repurposing of existing drugs. Candidates for repurposing include drugs that target COVID-19 pathobiology, including agents that alter angiotensin signaling. Recent data indicate that key findings in COVID-19 patients include thrombosis and endothelitis Activation of PAR1 (protease activated receptor 1), in particular by the protease thrombin, is a critical element in platelet aggregation and coagulation. PAR1 activation also impacts on the actions of other cell types involved in COVID-19 pathobiology, including endothelial cells, fibroblasts and pulmonary alveolar epithelial cells. Vorapaxar is an approved inhibitor of PAR1, used for treatment of patients with myocardial infarction or peripheral arterial disease. Here, we discuss evidence implying a possible beneficial role for vorapaxar in the treatment of COVID-19 patients and in addition, other as-yet non-approved antagonists of PAR1 and PAR4.
Metabolic pathways have emerged as cornerstones in carcinogenic deregulation providing new therapeutic strategies for cancer management. This is illustrated by the recent discovery of a cholesterol metabolic branch involving the biochemical transformation of 5,6-epoxycholesterol (5,6-ECs). 5,6-ECs have been shown to be differentially metabolized in breast cancers (BC) compared to normal breast tissue. 5,6-ECs are metabolized into the tumour promoter oncosterone in BC, while they are transformed into the tumour suppressor metabolite dendrogenin A (DDA) in normal breast tissue. Blocking oncosterone’s mitogenic and invasive potential will represent new opportunities for BC treatment. The reactivation of DDA biosynthesis, or its use as a drug, represents promising therapeutic approaches such as DDA-deficiency complementation, activation of BC cell re-differentiation and BC chemoprevention. This review presents current knowledge as to the 5,6-EC metabolic pathway in BC focusing on the 5,6-EC metabolic enzymes ChEH and HSD11B2, and on 5,6-EC metabolite targets LXRβ and GR.
Many Western countries have been affected by the outbreak of COVID-19. Italy has been particularly hit at the beginning of the pandemic, immediately after China. In Italy and elsewhere women seem to be less affected then men by severe/fatal COVID-19 infection, regardless of their age. Despite the evidence that women and men are different fort this infection, very few studies consider different therapeutic approaches for the two sexes. Undoubtedly, understanding the mechanisms at the bases of these differences may help to find appropriate and sex specific therapies. Here we consider that other mechanisms but estrogen protection are involved. Several X-linked genes (such as ACE2) and Y-linked genes (SRY, SOX9) may explain sex differences. Cardiovascular comorbidities are among the major enhancers of virus lethality. In addition, the number of sex-independent non-genetic factors that can change susceptibility and mortality is enormous, and many other factors are likely to be considered, including gender and cultural habits in different countries.
COVID-19 pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has overwhelmed Healthcare Systems requiring the rapid development of treatments, at least, to reduce COVID-19 severity. Drug repurposing offers a fast track. Here, we discuss the potential beneficial effects of statins in COVID-19 patients based on evidence that they may target virus receptors, replication, degradation and downstream responses in infected cells, addressing both basic research and epidemiological information. Briefly, statins could act modulating virus entry, acting on the SARS-CoV-2 receptors, ACE2 and CD147, and/or lipid rafts engagement. Statins, by inducing autophagy activation, could regulate virus replication or degradation, exerting protective effects. The well-known anti-inflammatory properties of statins, by blocking several molecular mechanisms, including NF-κB and NLRP3 inflammasome, could limit the “cytokine storm” in severe COVID-19 patients which is linked to fatal outcome. Finally, statin moderation of coagulation response activation may also contribute to improve COVID-19 outcomes.
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) 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 symtoms 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-CoV2 infects human cells by means of angiotensin converting enzyme 2 (ACE2), transmembrane protease serine 2 (TMPRSS2) and 3-chymotrypsin-like protease (3CLpro), also known as 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 kallicrein-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.
Identifying candidate drugs effective in the new coronavirus disease 2019 (Covid-19) is crucial, pending a vaccine against SARS-CoV2. We suggest the hypothesis that Cannabidiol (CBD), a non-psychotropic phytocannabinoid, has the potential to limit the severity and progression of the disease for several reasons: 1) High-CBD Cannabis Sativa extracts are able to downregulate the expression of the two key receptors for SARS-CoV2 in several models of human epithelia 2) CBD exerts a wide range of immunomodulatory and anti-inflammatory effects and it can mitigate the uncontrolled cytokine production featuring Acute Lung Injury 3) Being a PPARΥ agonist, it can display a direct antiviral activity 4) PPARΥ agonists are regulators of fibroblast/myofibroblast activation and can inhibit the development of pulmonary fibrosis, thus ameliorating lung function in recovered patients. We hope our hypothesis, corroborated by several preclinical evidence, will inspire further targeted studies to test CBD as a support drug against the COVID-19 pandemic.
The complement system is an ancient part of innate immunity sensing highly pathogenic coronaviruses by Mannan-binding lectin resulting in lectin pathway-activation and subsequent generation of the anaphylatoxins (AT) C3a and C5a as important effector molecules. Complement deposition in endothelial cells and high blood C5a serum levels have been reported in COVID-19 patients with severe illness, suggesting vigorous complement activation leading to systemic thrombotic microangiopathy (TMA). Strikingly, SARS-CoV-2-infected African Americans suffer from high mortality. Complement regulator gene variants prevalent in African Americans have been associated with a higher risk for severe TMA and multi-organ injury. These findings allow us to apply our knowledge from other complement-mediated diseases to COVID-19 infection to better understand severe disease pathogenesis. Here we will discuss the multiple aspects of complement activation, regulation, crosstalk with other parts of the immune system and the options to target complement in COVID-19 patients to halt disease progression and death.
The coronavirus disease 2019 (COVID-19) pandemic caused by SARS-CoV-2 infections has led to substantial unmet need for treatments, many of which will require testing in appropriate animal models of this disease. Vaccine trials are already underway, but there remains an urgent need to find other therapeutic approaches to either target SARS-CoV-2 or the complications arising from viral infection, particularly the dysregulated immune response and systemic complications which have been associated with progression to severe COVID-19. At the time of writing, in vivo studies of SARS-CoV-2 infection have been described using macaques, cats, ferrets, hamsters, and transgenic mice expressing human angiotensin I converting enzyme 2 (ACE2). These infection models have already been useful for studies of transmission and immunity, but to date only partially model the mechanisms implicated in human severe COVID-19. There is therefore an urgent need for development of animal models for improved evaluation of efficacy of drugs identified as having potential in the treatment of severe COVID-19. These models need to recapitulate key mechanisms of COVID-19 severe acute respiratory distress syndrome and reproduce the immunopathology and systemic sequelae associated with this disease. Here, we review the current models of SARS-CoV-2 infection and COVID-19-related disease mechanisms and suggest ways in which animal models can be adapted to increase their usefulness in research into COVID-19 pathogenesis and for assessing potential treatments.
COVID-19, the disease resulting from infection by a novel coronavirus: SARS-Cov2 that has rapidly spread since November 2019 leading to a global pandemic. SARS-Cov2 has infected over 2.8 million people and caused over 180,000 deaths worldwide. Although most cases are mild, a subset of patients develop a severe and atypical presentation of Acute Respiratory Distress Syndrome (ARDS) that is characterised by a cytokine release storm (CRS). Paradoxically, treatment with anti-inflammatory agents and immune regulators has been associated with worsening of ARDS. We hypothesize that the intrinsic circadian clock of the lung and the immune system may regulate individual components of CRS and thus chronotherapy may be used to effectively manage ARDS in COVID-19 patients.
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 ARDS.
The brain is the most cholesterol rich organ in the body containing about 25% of the body’s free cholesterol. Cholesterol cannot pass the blood brain barrier and be imported or exported directly, instead it is synthesised in situ and metabolised to oxysterols, oxidised forms of cholesterol, which can pass the blood brain barrier. 24S-Hydroxycholesterol is the dominant oxysterol in brain after parturition but during development a myriad of other oxysterols are produced which persist as minor oxysterols after birth. During both development and in later life, oxysterols and other sterols interact with a variety of different receptors, including nuclear receptors e.g. liver X receptors; membrane bound G protein-coupled receptors e.g. smoothened; the endoplasmic reticulum resident proteins e.g. INSIG (insulin induced gene), or the cholesterol sensing protein SCAP (SREBP cleavage activating protein); and the ligand-gated ion channel N-methyl-D-aspartate receptors found in nerve cells. In this review we summaries the different oxysterols (neuro-oxysterol) and sterols (neuro-sterols) found in the central nervous system whose biological activity is transmitted via these different classes of protein receptors.
Nitric oxide (NO) is a unique signaling molecule in the mammalian species. NO is produced by a variety of cell types to elicit distinct physiological actions. In the vascular system, NO is produced by the endothelium, a single layer of cells forming the inner lining of all blood vessels. Endothelium-derived NO has several different functions, one of which is vascular smooth muscle relaxation, resulting in vasodilation and a consequent decrease in blood pressure and increase in local blood flow. In the erectile tissue, NO is released as a neurotransmitter from the nerves innervating the corpus cavernosum during sexual stimulation, and causes profound smooth muscle relaxation and increased blood flow to the erectile tissue. This results in engorgement with blood and consequent penile erection.The uniqueness of NO as a signaling molecule derives, at least in part, by the fact that it is a gaseous molecule in its native state. However, despite being a gas, NO, like oxygen (O2), elicits its pharmacological effects as a solute in aqueous solution. Another unique characteristic of NO is its fleeting action because of its highly unstable chemical nature and reactivity. Unlike many other signaling molecules, NO elicits its wise array of physiological effects by distinct mechanisms. For example, vascular and nonvascular smooth muscle relaxation, and inhibition of platelet function are mediated by intracellular cyclic GMP (cyclic 3’, 5’-guanosine monophosphate). NO elicits many cyclic GMP-independent effects as well. For example, nitric oxide is a reactive free radical that can covalently modify protein function. One good example is protein S-nitrosylation, which can result in both regulatory and aberrant effects. By this and a variety of other mechanisms, NO also reacts with other molecules, such as reactive oxygen species, in invading cells such as bacteria, parasites and viruses to kill them or inhibit their replication or spread.The first pharmacological action of nitric oxide, demonstrated several years before it’s production in mammals was actually discovered, was vascular and nonvascular smooth muscle relaxation. One of many examples of the latter is the smooth muscle enveloping the sinusoidal cavities within the corpus cavernosum. Another important example is the airway smooth muscle in the trachea and bronchioles of the lungs. Indeed, inhalation of NO gas causes bronchodilation and increased delivery of air into the lungs. However, perhaps more significant than the bronchodilator effect of inhaled NO is its vasodilator effect. In fact, advantage was taken of the vasodilator action of NO in the lungs by Warren Zapol, MD, from the Massachusetts General Hospital in Boston, who discovered that inhalation of very small amounts of NO gas by newborn babies with life-threatening, persistent pulmonary hypertension (PPHN) results in a dramatic and permanent reversal of pulmonary vasoconstriction. Inhaled NO (INO) literally turned blue babies into pink babies. Without INO, most babies would have died while others would have required highly invasive procedures (extracorporeal membrane oxygenation; ECMO) to oxygenate their lungs, and may not have survived.Regarding its antiviral action, NO has been shown to increase the survival rate of mammalian cells infected with SARS-CoV (Severe Acute Respiratory Syndrome caused by coronavirus). In an in vitrostudy, NO donors (i.e., S-nitroso-N-acetylpenicillamine) greatly increased the survival rate of SARS-CoV-infected eukaryotic cells, suggesting direct antiviral effects of NO (1). In this study, NO significantly inhibited the replication cycle of SARS CoV in a concentration-dependent manner. NO also inhibited viral protein and RNA synthesis. Furthermore, NO generated by inducible nitric oxide synthase inhibited the SARS CoV replication cycle. The coronavirus responsible for SARS-CoV shares most of the genome of COVID- 19 indicating potential effectiveness of inhaled NO therapy in these patients.In 2004, during the SARS-CoV outbreak in China, the administration of inhaled NO reversed pulmonary hypertension, improved severe hypoxia and shortened the length of ventilatory support as compared to matched control patients with SARS-CoV (2). The mechanism of action was thought to be pulmonary vasodilation and consequent improved oxygenation in the blood of the lungs, thereby killing the virus, which does not do well in a high oxygen environment. In addition, however, I would offer the opinion that the NO also interacts directly with the virus to kill it and/or inhibit its replication, as shown in a prior study (1).Although studies have not yet been reported with COVID-19, NO has been shown to have an antiviral effect on several DNA and RNA virus families (3). The NO-mediated S-nitrosylation of viral molecules might be an intriguing general mechanism for the control of the virus life cycle. In this regard, it is conceivable that NO could nitrosylate cysteine-containing enzymes and proteins, including nucleocapsid proteins and glycoproteins, present in the coronavirus.In view of the knowledge gained by treating SARS-CoV patients with INO, it follows that INO might be effective in patients with the current SARS CoV-2 (COVID-19) infection. Indeed, a clinical trial of inhaled nitric oxide in patients with moderate to severe COVID-19 with pneumonia and under assisted ventilatory support recently received IRB (Institutional Review Board) approval at the Massachusetts General Hospital. Warren Zapol is director of this project. This trial has now been expanded to include at least two additional hospitals in the U.S. In the successful treatment of persistent pulmonary hypertension in newborns, the amount of NO inhaled is generally one ppm (part per million). In the clinical trial using COVID-19 patients, the amount of NO will be approximately 100-fold higher, about 100 ppm. This is a safe dose of INO, which could prove to be effective in killing the virus and allowing recovery of the patient. The effective use of INO would also lessen the need for oxygen, ventilators, and beds in the ICU.One thing I urge everyone to practice during this coronavirus pandemic is to breathe or inhale through your NOSE and exhale through your mouth. Swedish investigators at the Karolinska Institute in Stockholm have shown that the cells and tissues in the nasal sinusoids, but not the mouth, constantly and continuously produce nitric oxide, which is a gas, and can be easily detected in the exhaled breath. The physiological significance of this is that nasally-derived NO, when inhaled through the nose, improves oxygen delivery into the lungs by causing bronchodilation. This physiological action of inhaled NO is well-known by competitive athletes, especially runners. Moreover, when inhaling through the nose, your nasal nitric oxide is inhaled into your lungs where it stands a chance of meeting up with the coronavirus particles and killing them or inhibiting their replication. Inhaling through your mouth will NOT accomplish this. By the same token, exhaling through your nose is highly wasteful in that you would be expelling the NO away from the lungs, where it is needed most.“INHALE THROUGH YOUR NOSE, AND EXHALE THROUGH YOUR MOUTH!”
The complement system is a well-characterised cascade of extracellular serum proteins that is activated by pathogens and unwanted waste material. Products of activated complement signal to host cells via cell-surface receptors, illicting responses such as removal of the stimulus by phagocytosis. The complement system therefore functions as a warning system, resulting in removal of unwanted material. This review describes how extracellular activation of the complement system can also trigger autophagic responses within cells, upregulating protective homeostatic autophagy in response to perceived stress, but also intiating targeted anti-microbial autophagy in order to kill intracellular cyto-invasive pathogens. In particular, we will focus on recent discoveries that complement may also have roles in detection and autophagy-mediated disposal of unwanted materials within the intracellular environment. We therefore summarize the current evidence for complement involvement in autophagy, both by transducing signals across the cell membrane, as well as roles within the cellular environment.
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
Angiotensin converting enzyme-2 (ACE2) is the receptor for the coronavirus SARS-CoV-2, which causes COVID-19. We propose the following hypothesis: Imbalance in the action of ACE1- and ACE2-derived peptides, thereby enhancing Angiotensin-II (ANG II) signaling, a primary driver of COVID-19 pathobiology. ACE1/ACE2 imbalance occurs due to the binding of SARS-CoV-2 to ACE2, reducing ACE2-mediated conversion of ANG II to ANG peptides that counteract pathophysiological effects of ACE1-generated ANGII. This hypothesis suggests several approaches to treat COVID-19 by restoring ACE1/ACE2 balance: 1) ANG II receptor blockers (ARBs); 2) ACE1 inhibitors (ACEIs); 3) Agonists of receptors activated by ACE2-derived peptides [e.g., ANG (1-7), which activates MAS1]; 4) Recombinant human ACE2 or ACE2 peptides as decoys for the virus. Reducing ACE1/ACE2 imbalance is predicted to blunt COVID-19-associated morbidity and mortality, especially in vulnerable patients. Importantly, approved ARBs and ACEIs can be rapidly repurposed to test their efficacy in treating COVID-19.
In this review, we identify opportunities for drug discovery in the treatment of COVID-19 and in so doing, provide a rational roadmap whereby pharmacology and pharmacologists can mitigate against the global pandemic. We assess the scope for targetting key host and viral targets in the mid-term, by first screening these targets against drugs already licensed; an agenda for drug re-purposing, which should allow rapid translation to clinical trials. A simultaneous, multi-pronged approach using conventional drug discovery methodologies aimed at discovering novel chemical and biological means targetting a short-list of host and viral entities should extend the arsenal of anti-SARS-CoV-2 agents. This longer-term strategy would provide a deeper pool of drug choices for future-proofing against acquired drug resistance. Second, there will be further viral threats, which will inevitably evade existing vaccines. This will require a coherent therapeutic strategy which pharmacology and pharmacologists are best placed to provide.
Background and Purpose: Resurgence in the use of chloroquine as a putative treatment for COVID-19 has seen recent cases of fatal toxicity due to unintentional overdoses. Protocols for the management of poisoning recommend diazepam, although there are uncertainties in its pharmacology and efficacy in this context. The aim was to assess the effects of diazepam in experimental models of chloroquine cardiotoxicity. Experimental Approach: In vitro experiments involved cardiac tissues isolated from rats and incubated with chloroquine, alone, or in combination with diazepam. In vivo models of toxicity involved chloroquine administered intravenously to pentobarbitone-anaesthetised rats and rabbits. Randomised, controlled interventional studies in rats assessed diazepam, clonazepam and Ro5-4864 administered: (i) prior, (ii) during, and (iii) after chloroquine; and the effects of diazepam: (iv) at high dose, (v) in urethane-anaesthetised rats, and (vi) co-administered with adrenaline. Key Results: Chloroquine decreased the developed tension of left atria, prolonged the effective refractory period of atria, ventricular tissue and right papillary muscles, and caused dose-dependent impairment of haemodynamic and electrocardiographic parameters. Cardiac arrhythmias indicated impairment of atrioventricular conduction. Studies (i), (ii) and (v) showed no differences between interventions and control. Diazepam increased heart rate in study (iv) and, as with clonazepam, also prolonged the QTc interval in study (iii). Combined administration of diazepam and adrenaline in study (vi) improved cardiac contractility but caused hypokalaemia. Conclusion and Implications: Neither diazepam, nor other ligands for benzodiazepine binding sites, protect against or attenuate chloroquine cardiotoxicity. However, diazepam may augment the effects of positive inotropes in reducing chloroquine cardiotoxicity.