Evaluation of the toxicological effects of favipiravir (T-705) on liver and kidney in rats: biochemical and histopathological approach

Repositioning Antivirals Against COVID-19: Synthetic Pathways, Mechanisms, and Therapeutic Insights

The pandemic of COVID-19 has ignited a global race to locate effective therapies with drug repositioning emerging as a leading strategy due to its cost-effectiveness and established safety profiles. Remdesivir, Favipiravir, Hydroxychloroquine, and Chloroquine have been the focus of rigorous clinical trials to determine their therapeutic potential against SARS-CoV-2. This article delves into the innovative synthetic strategies behind these drugs, providing a blueprint for researchers navigating the complex landscape of antiviral development. Beyond synthesis, we explore the fascinating mechanisms of action: hydroxychloroquine and chloroquine elevate lysosomal pH to impede autophagy and viral replication; favipiravir, a nucleoside analogue, induces lethal mutagenesis or RNA chain termination and remdesivir disrupts viral RNA synthesis through delayed chain termination. By merging synthetic methodologies with mechanistic insights, this article offers a comprehensive resource aimed at accelerating the development of potent COVID-19 therapies and underscores the crucial part that chemistry in addressing global health emergencies. It also underscores the vital function of chemistry in addressing global health emergencies and highlights how innovative drug design and repurposing can provide rapid responses to emerging infectious diseases. This fusion of chemistry and virology not only advances our understanding of drug action but also paves the way for the discovery of new therapeutic agents crucial in future pandemics.

Experimental evaluation of favipiravir (T-705)-induced liver and kidney toxicity in rats

Favipiravir is an antiviral drug that selectively and potently inhibits RNA-dependent RNA polymerase of various RNA viruses. Its empirical use has increased with the COVID-19 pandemic. This study aimed to investigate the potential toxicological effects of favipiravir administration on healthy rats' liver and kidney tissues. Four groups were established in the survey (n = 10): Control, Low-dose favipiravir (100 mg/kg/d), Medium-dose favipiravir (200 mg/kg/d), and High-dose favipiravir (300 mg/kg/d). On the first day of the study, a loading dose equivalent to twice the maintenance dose was administered. On the eleventh day, liver and kidney tissues were collected for histopathological and immunohistochemical analyses. According to our results, favipiravir caused various histopathological damages in the liver and kidneys and led to alterations in the levels of cytokines associated with inflammation (IL-6, TGF-β, TNF-α, IL-1β, IFN-γ). Co-administration of favipiravir with various protective agents may be needed to mitigate potential damage to the liver and kidneys.

Investigation of metabolite profiles of kidney tissues in rats treated with favipiravir drug: An NMR-based metabolomics study

In response to the urgent need for effective treatments during the rapid spread and high mortality rate of COVID-19, existing drugs were repurposed for potential antiviral effects, including favipiravir, originally designed as an RNA-dependent RNA polymerase inhibitor for influenza. Despite limited antiviral effectiveness against COVID-19, favipiravir has been reported to cause several adverse drug events (ADEs) in the body. Recent studies have shown that favipiravir can damage various tissues in rats. However, a detailed analysis of its effects on the metabolomics profile of tissues using high-resolution spectroscopic technologies has not yet been conducted. In this study, it was aimed to analyze the metabolomic changes in rat kidney tissues induced by favipiravir, using high-resolution nuclear magnetic resonance (NMR) spectroscopy. Sixty male Wistar Albino rats were randomly divided into three groups: control, low-dose favipiravir (200 mg/kg), and high-dose favipiravir (300 mg/kg), with 20 rats per group. Each group received its respective treatment via oral gavage. After the treatment period, kidney tissue samples were collected and subjected to 1H NMR analysis. Bioinformatics analysis of the obtained 1H NMR spectra suggests that favipiravir induces dose-dependent metabolic changes in kidney tissue, with higher doses causing more profound disruptions in several pathways.

Evaluation of the effects of favipiravir (T-705) on the lung tissue of healty rats: An experimental study

Favipiravir, a broad-spectrum RNA-dependent RNA polymerase inhibitor widely used during the COVID-19 pandemic, effectively reduces viral load but has been linked to inflammatory changes in tissues such as the liver and kidneys. High-dose and prolonged use of favipiravir for COVID-19 raises concerns about its potential toxic effects on the lungs, particularly in patients with pre-existing pulmonary conditions. This study investigated favipiravir's effects on lung tissue in healthy rats. Experimental groups included a Control (saline) and three favipiravir doses: Low (200 mg/kg/day loading, 100 mg/kg/day maintenance), Medium (400 mg/kg/day loading, 200 mg/kg/day maintenance), and High (600 mg/kg/day loading, 300 mg/kg/day maintenance), all administered via gavage for 10 days. Histopathological analysis showed normal lung structure in the Control group, while favipiravir-treated groups exhibited Bronchus-Associated Lymphoid Tissue (BALT) enlargement, inflammation, fibrosis, and hemorrhage. Immunohistochemical analysis revealed dose-dependent increases in TNF-α, TGF-β, IL-6, IFN-γ, IL1-β, α-SMA, and collagen-1, especially in the High-dose group (p < 0.05). These findings suggest favipiravir may induce lung inflammation and fibrosis, emphasizing the need for careful evaluation of its safety in clinical settings, particularly for COVID-19 treatment. Future research should investigate the underlying mechanisms of these effects with clinical studies to assess their relevance to humans, high-risk pulmonary patients.

A standardized chamuangone enriched extract from Garcinia cowa Roxb. leaves shows acute and sub-acute safety

ETHNOPHARMACOLOGICAL RELEVANCE

The safety assessment of herbal products is critical for their appropriate pharmacological applications. Garcinia cowa Roxb., commonly known as Cha-muang in Thai, has ethnopharmacological relevance for inflammation, infectious diseases, and diabetes. The leaf extracts of G. cowa have been extensively reported for their anticancer, anti-inflammatory, antimicrobial, and antioxidant effects. Notably, chamuangone is their major active constituent that contributes to various pharmacological properties.

AIM OF THE STUDY

The current study aims to establish a standardized chamuangone enriched extract (CEE) and assess its acute and sub-acute toxicities in animal models.

METHODOLOGY

CEE was established from G. cowa leaves using a microwave-assisted extraction (MAE), followed by fractionation and enrichment through silica gel vacuum and column chromatography. The concentration of chamuangone in the extract was quantified using a validated quantitative high-performance liquid chromatography (HPLC) method. The safety profiles of CEE were thoroughly evaluated in rodents according to the Organization for Economic Cooperation and Development (OECD) 425 and 407 guidelines. The effects on oxidative stress markers such as superoxide dismutase (SOD), reduced glutathione (GSH), catalase (CAT), and malondialdehyde (MDA) levels were also evaluated in various organs.

RESULTS

Based on the quantitative HPLC analysis, the CEE contained 73.0 ± 2.0% w/w of chamuangone. In the acute toxicity study, following up and down procedure the female rats were dosed with CEE at 1750 and 550 mg/kg body weight (b.w.), with CEE 1750 mg/kg b.w. was toxic, causing mortality, while CEE 550 mg/kg b.w. was deemed safe. An LD50 value was calculated according to the standard protocols, resulting in 970 mg/kg b.w. In histopathological examination, 550 mg/kg b.w. of CEE was safe in all the selected organs, while the 1750 mg/kg b.w. CEE treated rats exhibited toxic effects in histological tissues sections in the form of necrosis in the brain, cardiac muscle hypertrophy, liver inflammation, mild untoward effect in the spleen, fibrosis in the lungs, pancreatitis, pyelonephritis, and ovarian cyst. Administration of CEE at doses of 550 mg/kg b.w. (single dose) in the acute and 100 mg/kg b.w. (regularly 28-days) in the sub-acute toxicity studies significantly (p < 0.05) decreased levels of uric acid, triglycerides, and cholesterol. Importantly, the CEE (550 and 100 mg/kg b.w.) also significantly increased the levels of antioxidant enzymes (SOD, GSH, and CAT) and decreased MDA levels. Normal histopathology was observed in the sub-acute toxicity study in all treated groups.

CONCLUSION

This study successfully concludes that CEE at a dose of 100 mg/kg b.w. is safe for therapeutic application or use as a chemopreventive functional food utilizing green extraction methods. However, chronic toxicity studies are further recommended to validate safety concerns over an extended period.

Investigation of oxidative, inflammatory and apoptotic effects of favipiravir use alone and combined with vitamin C on brain tissue of elderly rats

Favipiravir is a nucleoside analogue antiviral drug and inhibits the replication of many RNA viruses, especially influenza viruses. Favipiravir has also been used to treat patients with mild to moderate COVID-19 disease. However, various side effects, including neurological side effects, have been reported related to the use of favipiravir. Therefore, in this study, we aimed to investigate the possible effects of favipiravir alone or in combination with vitamin C on aged rats' brain tissue and the possible mechanisms of these effects. A total of 30 rats used in the study were randomly divided into 5 equal groups and the first group was kept as the control group. High-dose (100 mg/kg) or low-dose (20 mg/kg) favipiravir was administered alone or in combination with vitamin C (150 mg/kg) to other groups. Administration of both high and low doses of favipiravir significantly increased TBARS levels in brain tissue of aged rats. Similarly, both high and low doses of favipiravir led to significant increases in Bcl-2 and caspase-3 relative mRNA expression. However, only low dose favipiravir caused a significant increase in iNOS and IL-1β relative mRNA expression levels. Similar results were also observed in histopathological examinations. However, co-administration of vitamin C with favipiravir attenuated some of the adverse effects of favipiravir. In conclusion, in this study, it was shown that the use of favipiravir caused some adverse effects through oxidative, inflammatory and apoptotic processes in the brain tissue of aged rats, and the potential of vitamin C to alleviate these effects.

Biochemical and histopathological evaluation of systemic and ocular toxicity of favipiravir in rats

Purpose: Favipiravir (FAV) used against COVID-19 is an antiviral drug that causes adverse reactions, such as hyperuricaemia, liver damage, and hematopoetic toxicity. The aim of the study was to investigate the systemic and ocular side-effects of FAV in rats, for the first time.Materials and methods: A total of 18 albino male Wistar rats were used in the study. The rats were divided into 3 groups as the healthy group (HG), the group given 50 mg/kg/day favipiravir (FAV50), and the group given 200 mg/kg/d favipiravir (FAV200). These doses were given to the experimental groups for one week. At the end of the experiment histopathological examinations were performed on the conjunctiva and sclera of the eye. In addition, malondialdehyde (MDA), total glutathione (tGSH), superoxide dismutase (SOD), interleukin-1β (IL-1β), and tumor necrosis factor alpha (TNF-α) levels were measured in blood samples taken from rats. Results: Compared to HG, the MDA (1.37 ± 0.61 vs. 4.82 ± 1.40 µmol/mL), IL-1β (2.52 ± 1.14 vs. 6.67 ± 1.99 pg/mL), and TNF-α levels (3.28 ± 1.42 vs. 8.53 ± 3.06 pg/mL) of the FAV200 group were higher. The levels of tGSH (7.58 ± 1.98 vs. 2.50 ± 0.98 nmol/mL) and SOD (13.63 ± 3.43 vs. 3.81 ± 1.43 U/mL) the FAV200 group were lower than the HG (p < 0.05, for all). The degree of damage to the cornea and sclera of the FAV200 group was quite high according to HG (p < 0.001). Conclusions: FAV can cause damage to rat conjunctiva and sclera by increasing oxidant stress and inflammation at high dose.

Assessment of toxicological effects of favipiravir (T-705) on the lung tissue of rats: An experimental study

This study aimed to present new data on the side effects of favipiravir on healthy lung tissue and the respiratory system. In the study, two different durations (5 and 10 days) were preferred to determine the effect of favipiravir treatment due to clinical improvement rates of approximately 5 and 10 days during the use of favipiravir in COVID-19 patients. In addition, after 10 days of favipiravir treatment, animals were kept for 5 days without any treatment to determine the regeneration of lung tissues. Favipiravir was administered to rats by oral gavage at a daily dose of 200 mg/kg for 5 and 10 days, as in previous studies. At the end of the experiment, the histopathological and biochemical effects of favipiravir in the lung tissue were investigated. The data obtained from the study showed that favipiravir increased oxidative stress parameters, expression of apoptotic markers, and pro-inflammatory markers in lung tissue. Since malondialdehydes is an oxidant parameter, it increased in favipiravir-administered groups; It was determined that the antioxidant parameters glutathione, superoxide dismutase, glutathione peroxidase, and catalase decreased. Other markers used in the analysis are Bcl-2, Bax, NF-κB, interleukin (IL)-6, Muc1, iNOS, P2X7R, IL-6 and caspase-3. The levels of Bax, caspase-3, NF-κB, IL-6, Muc1, and P2X7R were increased in the Fav-treated groups compared with the control. However, the levels of Bcl-2 decreased in the Fav-treated groups. The present study proves that favipiravir, widely used today, causes side effects in lung tissue.

The effect of vitamin C supplementation on favipiravir-induced oxidative stress and proinflammatory damage in livers and kidneys of rats

Background: Favipiravir (FPV), an effective antiviral agent, is a drug used to treat influenza and COVID-19 by inhibiting the RNA-dependent RNA polymerase (RdRp) of RNA viruses. FPV has the potential to increase oxidative stress and organ damage. The purpose of this study was to demonstrate the oxidative stress and inflammation caused by FPV in the liver and kidneys of rats, as well as to investigate the curative effects of vitamin C (VitC).Methods: A total of 40 Sprague-Dawley male rats were randomly and equally divided into the following five groups: 1st; Control, 2nd; FPV = 20 mg/kg, 3rd; FPV = 100 mg/kg, 4th; FPV = 20 mg/kg + VitC (150 mg/kg), and 5th; FPV = 100 mg/kg + VitC (150 mg/kg) groups. Rats were given either FPV (orally) or FPV plus VitC (intramuscular) for 14 days. Rat blood, liver, and kidney samples were collected at 15 days to be analyzed for oxidative and histological changes.Results: FPV administration resulted in an increase in proinflammatory cytokines (TNF-α and IL-6) in the liver and kidney, as well as oxidative and histopathologic damage. FPV increased TBARS levels significantly (p < .05) and decreased GSH and CAT levels in liver and kidney tissues but had no effect on SOD activity. VitC supplementation significantly reduced TNF-a, IL-6, and TBARS levels while increasing GSH and CAT levels (p < .05). Furthermore, VitC significantly attenuated FPV-induced histopathological alterations associated with oxidative stress and inflammation in the liver and kidney tissues (p < .05).Conclusion: FPV caused liver and kidney damage in rats. In contrast, co-administration of FPV with VitC improved FPV-induced oxidative, pro-inflammatory, and histopathological changes.

Tracing down the Updates on Dengue Virus-Molecular Biology, Antivirals, and Vaccine Strategies

BACKGROUND

Nearly half of the world is at risk of developing dengue infection. Dengue virus is the causative agent behind this public healthcare concern. Millions of dengue cases are reported every year, leading to thousands of deaths. The scientific community is working to develop effective therapeutic strategies in the form of vaccines and antiviral drugs against dengue.

METHODS

In this review, a methodological approach has been used to gather data from the past five years to include the latest developments against the dengue virus.

RESULTS

Different therapeutics and antiviral targets against the dengue virus are at different stages of development, but none have been approved by the FDA. Moreover, various vaccination strategies have also been discussed, including attenuated virus vaccines, recombinant subunit vaccines, viral vector vaccines, DNA vaccines, nanotechnology, and plant-based vaccines, which are used to develop effective vaccines for the dengue virus. Many dengue vaccines pass the initial phases of evaluation, but only two vaccines have been approved for public use. DENGVAXIA is the only FDA-approved vaccine against all four stereotypes of the dengue virus, but it is licensed for use only in individuals 6-16 years of age with laboratory-confirmed previous dengue infection and living in endemic countries. Takeda is the second vaccine approved for use in the European Union, the United Kingdom, Brazil, Argentina, Indonesia, and Thailand. It produced sustained antibody responses against all four serotypes of dengue virus, regardless of previous exposure and dosing schedule. Other dengue vaccine candidates at different stages of development are TV-003/005, TDENV PIV, V180, and some DNA vaccines.

CONCLUSION

There is a need to put more effort into developing effective vaccines and therapeutics for dengue, as already approved vaccines and therapeutics have limitations. DENGVAXIA is approved for use in children and teenagers who are 6-16 years of age and have confirmed dengue infection, while Takeda is approved for use in certain countries, and it has withdrawn its application for FDA approval.

The preclinical discovery and development of molnupiravir for the treatment of SARS-CoV-2 (COVID-19)

INTRODUCTION

Molnupiravir (MOV) is a broad-spectrum oral antiviral agent approved for the treatment of COVID-19. The results from in vitro and in vivo studies suggested MOV activity against many RNA viruses such as influenza virus and some alphaviruses agents of epidemic encephalitis. MOV is a prodrug metabolized into the ribonucleoside analog β-D-N⁴-hydroxycytidine. It is incorporated into the viral RNA chain causing mutations impairing coding activity of the virus, thereby inhibiting viral replication.

AREAS COVERED

This review analyzes the in vitro and in vivo studies that have highlighted the efficacy of MOV and the main pre-authorization randomized controlled trials evaluating its safety, tolerability, and pharmacokinetics, as well as its antiviral efficacy against SARS-COV-2 infection.

EXPERT OPINION

MOV is an antiviral agent with an excellent tolerability profile with few drug-drug interactions. Treatment of mild-to-moderate COVID-19 can benefit from MOV administration in the precocious phases of the disease, prior to the trigger of an aberrant immune response responsible for the parenchymal damage to pulmonary and extrapulmonary tissues. However, its suspected mutagenic effect can be a factor limiting its use at least in selected populations and studies on its teratogen effects should be planned before it is authorized for use in the pediatric population or in pregnant women.

Pulmonary Delivery of Favipiravir in Rats Reaches High Local Concentrations without Causing Oxidative Lung Injury or Systemic Side Effects

Favipiravir displays a rapid viral clearance, a high recovery rate and broad therapeutic safety; however, its oral administration was associated with systemic side effects in susceptible patients. Considering that the pulmonary route could provide a high drug concentration, and a safer application with less absorption into systemic circulation, it was aimed to elucidate whether favipiravir delivered via soft-mist inhaler has any deleterious effects on lung, liver and kidney tissues of healthy rats. Wistar albino rats of both sexes (n = 72) were placed in restrainers, and were given either saline or favipiravir (1, 2.5, 5 or 10 mg/kg in 1 mL saline) by inhalation within 2 min for 5 consecutive days. On the 6th day, electrocardiographic recording was obtained, and cardiac blood and lung tissues were collected. Favipiravir did not alter cardiac rhythm, blood cell counts, serum levels of alanine transaminase, aspartate transaminase, blood urea nitrogen, creatinine, urea or uric acid, and did not cause any significant changes in the pulmonary malondialdehyde, myeloperoxidase activity or antioxidant glutathione levels. Our data revealed that pulmonary use of favipiravir via soft-mist inhaler enables a high local concentration compared to plasma without oxidative lung injury or cardiac or hepatorenal dysfunction.