COVID-19 Drugs: New European Study Shows That Fenofibrate (Tricor) Exhibits Antiviral Properties Against SARS-CoV-2 Coronavirus
: A new study by researchers from University of Birmingham-UK, Keele University-UK, San Raffaele Scientific Institute-Italy, University of Copenhagen-Denmark and the University of Liverpool-UK demonstrates that the drug called Fenofibrate exhibits antiviral properties against the SARS-CoV- coronavirus and could be repurposed to treat COVID-19.
Fenofibrate, sold under the brand name Tricor among others, is a medication of the fibrate class used to treat abnormal blood lipid levels. Fenofibrate
is used along with a proper diet to help lower "bad" cholesterol and fats (such as LDL, triglycerides) and raise "good" cholesterol (HDL) in the blood. It works by increasing the natural substance (enzyme) that breaks down fats in the blood.
The SARS-CoV-2 pandemic has caused a significant number of fatalities and worldwide disruption. To date more than 1.98 million people have died from the COVID-19 disease globally and more than 92.5 million people have already been infected with the virus. America leads the country with the most infections and deaths so far with more than 385,000 Americans who have died from the disease so far and more than 23 million Americans have already been infected. Infections and deaths in the United Kingdom is fast rising exponentially and hopefully it will soon rise up to the second place behind the United States or at least behind Indian, coming in third.
In order to identify drugs to repurpose to treat SARS-CoV-2 infections, wthe study team established a screen to measure dimerization of ACE2, the primary receptor for the virus. This screen identified fenofibric acid, the active metabolite of fenofibrate. Fenofibric acid also destabilized the receptor binding domain (RBD) of the viral spike protein and inhibited RBD binding to ACE2 in ELISA and whole cell binding assays.
Both fenofibrate and fenofibric acid were tested by two independent laboratories measuring infection of cultured Vero cells using two different SARS-CoV-2 isolates. In both settings at drug concentrations which are clinically achievable, fenofibrate and fenofibric acid reduced viral infection by up to 70%. Together with its extensive history of clinical use and its relatively good safety profile, these studies identify fenofibrate as a potential therapeutic agent requiring urgent clinical evaluation to treat SARS-CoV-2 infection.
The study findings were published on a preprint server and are currently being peer reviewed. https://www.biorxiv.org/content/10.1101/2021.01.10.426114v1
The second wave of the COVID-19pandemic, caused by the SARS-CoV-2 coronavirus has led to renewed efforts to find effective antivirals, both newly developed or repurposed drugs.
This new study reports the efficacy of the cholesterol-reducing drug fenofibrate in reducing infection rates of SARS-CoV-2 in cultured cells.
The SARS-CoV-2 coronavirus must engage host cells via its receptor-binding domain (RBD) on its spike protein, which binds to the angiotensin-converting enzyme 2 (ACE2) receptor on the host cell. Inhibitors of spike-ACE2 binding are therefore likely to reduce the entry of the virus into host cells, th
us reducing disease severity or preventing transmission of the virus altogether.
To date they are no effective drugs to treat COVID-19 despite scams perpetrated by the various American regulatory and healthcare entities like the U.S. FDA or by the U.S. NIH with drugs like hydroxychloroquine, remdesivir, convalescent plasma and various monoclonal therapeutics.
This study employed an assay that evaluates the spike RBD-ACE2 binding to help identify binding inhibitors that act through novel mechanisms, and might therefore escape recognition. ACE2 is a dimer, and multiple RBDs may interact with each ACE2 molecule. It is also a flexible protein, enabling binding between more than one dimeric ACE2 with a single trimeric spike. If ACE2 dimerization is affected, therefore, the avidity of binding to RBD is possibly impaired.
Interestingly with other receptors, dimer formation has been found to increase internalization. This could therefore be a promising target for antiviral drugs. The researchers developed another assay that measures dimerization of ACE2 using the NanoBIT interaction system.
This system contains two components, LgBIT and SmBIT, which are individually inactive but are activated when they combine to form an active luciferase enzyme.
Hence, they can be fused to the ACE2 monomer so that their association in dimer form allows the formation of active luciferase.
The study team then perused through a library of a hundred already approved drugs to identify potential inhibitors of ACE2 dimerization. They found that fenofibric acid, which is the active form of the cholesterol synthesis inhibitor fenofibrate, led to twice as much ACE2 dimer formation, which prevented RBD-ACE2 binding by destabilizing the spike RBD. Both fenofibrate and fenofibric acid reduced the thermal stability of RBD, though fenofibric acid was active at a much lower drug concentration. The fenofibric acid had a modest but significant inhibitory effect on RBD-ACE2 binding, as did fenofibrate.
It was found that the increase in dimerization peaked at about 30 minutes following exposure to fenofibric acid. Fenofibrate failed to show any significant activity in this assay, perhaps because it lacks a free carboxylic acid, unlike fenofibric acid.
The subsequent step was to screen for the effect of the drug on the virus infection itself.
These two drugs were assessed for infection inhibition by SARS-CoV-2 in two different assays and using two different viral isolates. The use of live virus allowed both primary infection and secondary infection by newly released viral particles to be assessed, at 24 and 48 hours, respectively.
For the initial step, the hCOV-19/England/2/2020 virus strain was tested. With fenofibrate, virus infection was reduced by 65% (from 59% of cells to 18% of cells) at 230 μM, relative to the controls.
Importantly cell viability was not reduced. In contrast, other statins like simvastatin and pitavastatin also reduced infection rates but at the cost of cell viability.
Next, the study team tested the effect of fenofibric acid and fenofibrate using live SARS-CoV-2.
The study team found that at 24 hours, fenofibrate reduced infection levels by 60%, and to a smaller extent with fenofibrate, though the reduction observed with fenofibric acid was not significant. The same pattern was seen at 48 hours, which showed sustained suppression of infection by fenofibrate.
Significantly this agrees with earlier studies showing that fenofibrate, as well as fenofibric acid to a smaller extent, are strong contenders as SARS-CoV-2 inhibitors. The pattern of inhibition was sustained at 24 and 48 hours. Thus, fenofibrate can both prevent primary infection and reduce secondary infection rates.
The findings were confirmed by reduced viral N-gene RNA levels with fenofibrate, in a dose-dependent manner. Even though fenofibrate operates on lipid metabolism via the PPARα pathway, this does not appear to account for the antiviral action.
The study findings were also confirmed using a second strain of the virus in a plaque assay. The use of fenofibric acid reduced plaque formation by 76% at a dose of 250μM, with fenofibrate showing a similar but less powerful action.
As plaque assays are the gold standard in determining infectivity for this SARS-CoV-2, these results are significant. In both cases, pretreatment with fenofibrate was just as powerful as co-treatment.
According to the study team it appears that the antiviral effects of fenofibrate and its metabolite are not due to its inhibition of cholesterol synthesis, nor to their direct effect on the viability of the infected cells. The differences in the level of inhibition observed with the different assays may be due to the different strains used or the variation in the methods.
For example, fenofibrate may alter the conformation of ACE2 rather than causing it to dimerize.
Furthermore the ‘open’ and ‘closed’ conformations of ACE2 may affect RBD-ACE2 binding at the level of RBD monomers, or affect the number of spike proteins capable of attaching to each ACE2 dimer. Either way, binding avidity could be affected. Changes in ACE2 conformation could also make it more resistant to proteolysis by the serine protease TMPRSS2.
Should fenofibrate truly exert its antiviral activity via ACE2-mediated effects; this imparts additional advantages over other drugs that inhibit viral proteins, because its activity is less susceptible to viral mutational escape.
Importantly, it reduces the RBD stability and impairs ACE2-RBD binding, both of which reduce the extent of infection in treated cells.
Hence this shows that fenofibrate may act via multiple mechanisms, reducing the chances of viral resistance emerging rapidly.
For example, it increases the levels of the glycosphingolipid sulfatide, which could reduce SARS-CoV-2 infection. It suppresses airway inflammation and hence cytokine release, which is associated with severe COVID-19. It has also been suggested to reduce thrombosis and platelet aggregation, promote clot lysis and thus prevent or modulate hypercoagulability, seen in advanced COVID-19. Its role in inhibiting cholesterol biosynthesis via PPARα has also been suggested to be beneficial in preventing infection, and two trials have been registered to examine this premise.
The research team concluded, “Utilizing two different virus isolates, we demonstrate that fenofibrate, or its active metabolite fenofibric acid, are able to significantly reduce SARS-CoV-2 infection in cell culture models.”
Most importantly the safety of this drug, its convenience of use, and bioavailability at currently recommended doses, along with its cheapness and wide availability as a generic drug, has led to the recommendation that it be used in clinical trials to assess its efficacy in preventing severe or critical COVID-19.
The study team said, “Further detailed studies to clarify the precise mechanism of the anti-viral activity of fenofibrate are warranted, but this should not delay the urgent clinical evaluation of the drug to counter the current crisis.”
Thailand Medical News had also published in July 2020 a study by Israeli researchers linking fenofibrate with decrease mortality and severity in hospitalized COVID-19 patients. https://www.thailandmedical.news/news/covid-19-drugs-israeli-researchers-discover-that-cholesterol-lowering-drug-fenofibrate-tricor-could-downgrade-covid-19-severity
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