Discovery of Chalcone-Based Hybrid Structures as High Affinity and Site-Specific Inhibitors against SARS-CoV-2: A Comprehensive Structural Analysis Based on Various Host-Based and Viral Targets.

Previous studies indicated that natural-based chalcones have significant inhibitory effects on the coronavirus enzymes 3CLpro and PLpro as well as modulation of some host-based antiviral targets (HBATs). In this study, a comprehensive computational and structural study was performed to investigate the affinity of our compound library consisting of 757 chalcone-based structures (CHA-1 to CHA-757) for inhibiting the 3CLpro and PLpro enzymes and against twelve selected host-based targets. Our results indicated that CHA-12 (VUF 4819) is the most potent and multi-target inhibitor in our chemical library over all viral and host-based targets. Correspondingly, CHA-384 and its congeners containing ureide moieties were found to be potent and selective 3CLpro inhibitors, and benzotriazole moiety in CHA-37 was found to be a main fragment for inhibiting the 3CLpro and PLpro. Surprisingly, our results indicate that the ureide and sulfonamide moieties are integral fragments for the optimum 3CLpro inhibition while occupying the S1 and S3 subsites, which is fully consistent with recent reports on the site-specific 3CLpro inhibitors. Finding the multi-target inhibitor CHA-12, previously reported as an LTD4 antagonist for the treatment of inflammatory pulmonary diseases, prompted us to suggest it as a concomitant agent for relieving respiratory symptoms and suppressing COVID-19 infection.

Dual action anti-inflammatory/antiviral isoquinoline alkaloids as potent naturally occurring anti-SARS-CoV-2 agents: A combined pharmacological and medicinal chemistry perspective.

In the search for compounds that inhibit the SARS-CoV-2 after the onset of the COVID-19 pandemic, isoquinoline-containing alkaloids have been identified as compounds with high potential to fight the disease. In addition to having strong antiviral activities, most of these alkaloids have significant anti-inflammatory effects which are often manifested through the inhibition of a promising host-based anti-COVID-19 target, the p38 MAPK signaling pathway. In the present review, our pharmacological and medicinal chemistry evaluation resulted in highlighting the potential of anti-SARS-CoV-2 isoquinoline-based alkaloids for the treatment of COVID-19 patients. Considering critical parameters of the antiviral and anti-inflammatory activities, mechanism of action, as well as toxicity/safety profile, we introduce the alkaloids emetine, cephaeline, and papaverine as high-potential therapeutic agents for use in the treatment of COVID-19. Although preclinical studies confirm that some isoquinoline-based alkaloids reviewed in this study have a high potential to inhibit the SARS-CoV-2, their entry into drug regimens of COVID-19 patients requires further clinical trial studies and toxicity evaluation.

Application of emetine in SARS-CoV-2 treatment: regulation of p38 MAPK signaling pathway for preventing emetine-induced cardiac complications.

Emetine is one of the most highly potent anti-SARS-CoV-2 agents ever identified. In addition to having strong anti-SARS-CoV-2 activities, emetine has other valuable therapeutic effects such as strong anti-inflammatory and anti-arterial pulmonary hypertension (APH) properties, which are suitable for the treatment of COVID-19. Its proper concomitant therapeutic effect has led researchers to test this compound in clinical trials to combat COVID-19. However, due to the risks of cardiac complications, very low doses of emetine have been used in different studies, which may not have significant therapeutic effects. The p38 MAPK signaling pathway is strongly highlighted as an important operator in cardiac cellular damages such as disruption of cardiac fibroblast function and myopathy/cardiomyopathy. Inhibition of this pathway by appropriate inhibitors has also been considered by scientists as a promising strategy for the treatment of fatal host-related hyper-inflammatory immune responses following SARS-CoV-2 infection. Although remarkable stimulatory effects of emetine on activation of the p38 MAPK pathway have been reported in recent studies and strong evidence suggests that this pathway plays an effective role in the emetine's toxicities, it has not been discussed yet that emetine induced cellular cardiac complications may be due to the activation of this critical pathway. Considering these points could lead to the finding of strategies for applying the valuable potential of emetine in the treatment of COVID-19 at low risks.

Papaverine, a promising therapeutic agent for the treatment of COVID-19 patients with underlying cardiovascular diseases (CVDs).

The causative agent of coronavirus disease-2019 (COVID-19), severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), enters the host cells via an angiotensin-converting enzyme 2 (ACE2)-mediated endocytosis-dependent manner. Because ACE2 is highly expressed in the heart, SARS-CoV-2 can severely infect heart tissue and arteries, causing acute and chronic damage to the cardiovascular system. Therefore, special attention should be paid to finding appropriate agents to protect this vital system during COVID-19 treatment. Papaverine is a unique vasodilator alkaloid that is clinically used in the treatment of vasospasm. Interestingly, this compound has potent and direct effects on a wide range of viruses, and could also prevent viral exploitation mechanisms of the host cell facilities by inhibiting some cellular signaling pathways such as p38 MAPK. This pathway was recently introduced as a promising target for the treatment of COVID-19. Papaverine also has anti-inflammatory effects which is useful in combating the hyper-inflammatory phase of the COVID-19. Unlike some medications that have severe dosage-restrictions in the treatment of COVID-19 due to cardiac side effects, papaverine is recommended for use in many heart disorders. The ability of papaverine to treat COVID-19 has become more promising when the results of some extensive screenings showed the strong ability of this compound to inhibit the cytopathic effects of SARS-CoV-2 with EC50 of 1.1 µM. Having several therapeutic effects along with desired safety profile raises this hypothesis that papaverine could be a promising compound for the suppression of SARS-CoV-2 and prevention of ischemia/vasoconstriction-related complications in COVID-19 disease, especially in patients with underlying cardiovascular diseases (CVDs).

A Recent Update on the Clinical Trials and Effectiveness of Drugs Used in COVID-19, MERS and SARS Coronaviruses

Background: Coronaviruses including COVID-19, MERS and SARS have affected millions of people around the world since their emergence. Still, there is not a certain drug treatment strategy for coronaviruses. Objective: This review aims at a compilation of a comprehensive study on literature reporting the treatment strategies and regimens used for COVID-19, MERS and SARS with an emphasis on the clinical trials and experimentations. Results: According to the literature, the most effective drugs reported so far for treatment strategies include: lopinavir/ritonavir, favipiravir, ribavirin, oseltamivir, remdesivir, hydroxychloroquine, herbal extracts, monoclonal antibodies and anticytokine agents. Some combinations of drugs have been very effective to reduce the death rate, hospitalization stay and to prevent the progress of the disease to the later critical and severe stages. Conclusions: However, a combination of drugs and regimens have been useful and saved millions of patient’s lives but the clinical data reviewed in this essay indicate that the current drugs do not make an impervious barrier against coronavirus infections and cannot protect or treat patients completely. Therefore, there is a much demand for the discovery and introduction of new antiviral drugs.

Therapeutic potential of chelerythrine as a multi-purpose adjuvant for the treatment of COVID-19.

Multifunctional nature of phytochemicals and their chemical diversity has attracted attention to develop leads originated from nature to fight COVID-19. Pharmacological activities of chelerythrine and its congeners have been studied and reported in the literature. This compound simultaneously has two key therapeutic effects for the treatment of COVID-19, antiviral and anti-inflammatory activities. Chelerythrine can prevent hyper-inflammatory immune response through regulating critical signaling pathways involved in SARS-CoV-2 infection, such as alteration in Nrf2, NF-κB, and p38 MAPK activities. In addition, chelerythrine has a strong protein kinase C-α/-ß inhibitory activity suitable for cerebral vasospasm prevention and eryptosis reduction, as well as beneficial effects in suppressing pulmonary inflammation and fibrosis. In terms of antiviral activity, chelerythrine can fight with SARS-CoV-2 through various mechanisms, such as direct-acting mechanism, viral RNA-intercalation, and regulation of host-based antiviral targets. Although chelerythrine is toxic in vitro, the in vivo toxicity is significantly reduced due to its structural conversion to alkanolamine. Its multifunctional action makes chelerythrine a prominent compound for the treatment of COVID-19. Considering precautions related to the toxicity at higher doses, it is expected that this compound is useful in combination with proper antivirals to reduce the severity of COVID-19 symptoms.