One such target is the 3C-like proteinase (3CLpro), a key enzyme involved in viral replication. Inhibition of 3CLpro has shown promise in reducing viral spread and mitigating severe complications associated with COVID-19 (6, 7). Additionally, RNA-dependent RNA polymerase (RdRp), crucial for the viral life cycle, presents another avenue for antiviral drug development (13, 14).
Protease Inhibition Strategies
The absence of a human homolog for 3CLpro makes it an attractive target for antiviral drugs, and its conservation among coronaviruses suggests the potential for broad-spectrum antivirals (10). Notably, Pfizer’s introduction of Nirmatrelvir, in combination with Ritonavir, under the name “Paxlovid” in late 2021 marked a significant milestone (11). Nirmatrelvir, through effective covalent inhibition of 3CLpro, demonstrated an 89% reduction in severe complications in unvaccinated, hospitalized adults with symptomatic COVID-19 infection (12).
RdRp Inhibition Strategies
RNA-dependent RNA polymerase (RdRp) serves as another promising target due to its essential role in the RNA virus life cycle (13, 14). Low-fidelity viral RdRPs, lacking proofreading functions, make nucleoside analogs effective in causing premature termination or lethal mutations in viral RNA (16). These strategies offer potential avenues for long-term antiviral interventions against evolving viral pathogens like SARS-CoV-2 (17).
Combating COVID-19: The Urgent Need for Novel Antivirals
Uzbekistan’s Unique Contribution
In the Republic of Uzbekistan, researchers have explored the effectiveness of Rutan, a compound derived from Rhus coriaria, against various viruses, including influenza, adenoviruses, paramyxoviruses, herpes virus, and cytomegalovirus (19). Rutan’s anti-radical antioxidant activity and stabilizing effect on cardiomyocytes make it a potential candidate for addressing respiratory dysfunction, heart failure, circulatory disorders, and other conditions associated with coronavirus infection.
Rutan’s Antiviral Potential
Clinical trials conducted in 2015 recommended Rutan as an antiviral drug for treating influenza viruses in Uzbekistan (20). Given the importance of repurposing existing antiviral molecules against COVID-19, researchers investigated Rutan’s effectiveness against SARS-CoV-2. Results from in vitro experiments, preclinical studies, and randomized, open-label, controlled clinical trials demonstrated Rutan’s potential as a multi-component antiviral drug for treating coronavirus infections.
Discussion: Unveiling Rutan’s Antiviral Potential Against SARS-CoV-2
Isolation and Antiviral Activity of Rutan: The study initiated with the extraction of polyphenols from dried leaves of tannic sumac Rhus coriaria, resulting in the creation of Rutan. The compound, composed of five main components, exhibited potent antiviral activity against influenza A/California/07/09 (H1N1) strain with an EC50 of 3.2 μM, surpassing the positive control Favipiravir (EC50 of 24 μM). Importantly, Rutan displayed low cytotoxicity, with a concentration range just above 50 μM, yielding a selectivity index (SI) of over 15. Notably, Rutan showcased significant inhibitory activity against SARS-CoV-2 RdRp, outperforming Myricetin by 3.8 times.
RdRp Inhibitory Activity of Rutan: In-depth exploration of Rutan’s mechanism revealed its ability to block the formation of the RdRp-RNA complex, hindering efficient binding of SARS-CoV-2 RdRp to RNA. This process involved two accessory proteins, nsp7 and nsp8, ultimately preventing RNA polymerization. Rutan and its main components demonstrated inhibitory effects on poly-U primer elongation, with synergistic effects observed in the sum of components. Notably, Rutan exhibited promising inhibitory activity against SARS-CoV-2 virus in Vero E6 cells, with an EC50 value of 5.245 μM, showcasing its potential as an effective antiviral drug. A comparative analysis with Remdesivir revealed Rutan’s EC50 to be 2.6 times lower, presenting a compelling case for Rutan’s efficacy.
CLpro Protease Inhibition Activity: Given the pivotal role of 3CLpro in the viral maturation and replication cycle, Rutan’s inhibitory activity against SARS-CoV-2 3CLpro was examined. In laboratory in vitro experiments, Rutan exhibited antiviral activity, inhibiting 3CLpro at a concentration of 0.5 μM by 17.7%, reaching 97.5% at 50 μM. Comparatively, the flavonoid Baicalein and previously reported inhibitors displayed IC50 values of 0.94 μM and 4.5 μM, respectively. Moreover, Rutan’s main components showcased higher inhibition (IC50 values ranging from 1.3–9.9 μM) of the main coronavirus protease compared to established inhibitors like Lopinavir and quercetin.
Clinical Studies in Adults: The comprehensive investigation of Rutan’s efficacy transitioned to clinical studies in adults, adhering to the ethical principles of the Declaration of Helsinki and the regulatory framework of the Republic of Uzbekistan. Randomized, open-label, controlled clinical trials involving 121 adult patients with SARS-CoV-2 were conducted, categorizing them based on disease severity. Rutan tablets (100 mg) were administered twice daily for 10 days to the main groups, while control groups received standard therapy per the National Interim Protocol 7.
Results from the study unveiled Rutan’s notable impact on clinical symptoms, showcasing its effectiveness in reducing weakness, lethargy, headache, dizziness, sore throat, anosmia, ageusia, and myalgia. Importantly, Rutan-treated patients experienced early alleviation of symptoms, with an average discharge occurring on day seven after Rutan initiation. Moreover, Rutan demonstrated significant efficacy in reducing viral load, as reflected by the PCR analysis, with a remarkable 100% negativity rate at discharge compared to the control group. The study underscored Rutan’s potential in curbing the progression of COVID-19, highlighting its safety and absence of severe side effects.
Clinical Studies in Children: In extending the study to children (ages 6–18), Rutan’s efficacy was examined in a randomized, open-label, controlled clinical trial involving 201 PCR-positive children. Rutan tablets (25 mg) were employed in complex therapy for children with mild and moderate COVID-19. The findings demonstrated Rutan’s significant clinical impact, effectively relieving hyperthermia, reducing the severity of cough and shortness of breath, and restoring various clinical symptoms compared to the control group.
Moreover, the study investigated the biochemical indicators of inflammation, namely C-reactive protein (CRP) and D-dimer, revealing a substantial decrease in CRP levels in the Rutan-treated group. Notably, children treated with Rutan exhibited a quicker resolution of symptoms, with the duration of symptoms reduced by 2–3 days in the mild course and 3–4 days in the moderate course. Importantly, Rutan demonstrated efficacy in minimizing the duration of virus shedding, with PCR analysis revealing a significantly lower virus detection rate in the Rutan group compared to the control group.
Furthermore, the study delved into the long-term effects post-COVID, indicating that Rutan-treated children exhibited fewer and less severe post-COVID symptoms compared to the control group. The manifestation of asthenia-vegetative and inflammatory-pain syndromes were notably lower in the Rutan group. Gender-based and age-specific analyses revealed Rutan’s consistent efficacy, suggesting its potential as a foundational treatment for children with mild and moderate COVID-19.
Conclusion and Future Directions: The comprehensive clinical studies presented here highlight Rutan’s effectiveness in treating both adults and children with mild and moderate COVID-19. The absence of severe side effects, the reduction in viral load, and the alleviation of symptoms position Rutan as a promising therapeutic agent. The findings advocate for the inclusion of Rutan in the standard treatment protocols for COVID-19, particularly in the Republic of Uzbekistan.
However, it is essential to acknowledge the need for further research, especially in larger, multi-national/multi-institutional clinical trials to validate Rutan’s efficacy on a broader scale. Investigating the synergistic effects and cellular mechanisms of Rutan fractions is crucial for a more profound understanding of its therapeutic potential. The limitations of the study, such as the medium-sized participant pool and its single-institution nature, emphasize the necessity for expansive, collaborative research efforts to establish Rutan as a globally recognized antiviral treatment for COVID-19.
reference link : https://www.frontiersin.org/articles/10.3389/fmed.2023.1310129/full
