Ivermectin, antiviral properties and COVID-19: a possible new mechanism of action

Emanuele Rizzo  Naunyn-Schmiedeberg’s Archives of Pharmacology volume 393, pages1153–1156(2020) https://link.springer.com/article/10.1007/s00210-020-01902-5

However, ivermectin could prove to be a powerful antiviral, therefore also useful for a possible treatment of the new coronavirus associated syndrome, even from a new perspective. This could happen assuming its role as an ionophore agent, only hinted in the recent past but never fully described (Juarez et al. 2018). Ionophores are molecules that typically have a hydrophilic pocket which constitutes a specific binding site for one or more ions (usually cations), while its external surface is hydrophobic, allowing the complex thus formed to cross the cell membranes, affecting the hydro-electrolyte balance (Freedman 2012). These chemical species have historically been used to study the mitochondrial respiratory chain and ATP synthesis in eukaryotes (in this case also known as decoupling agents, such as 2, 4-dinitrophenol), and their antibiotic activity has long been appreciated (Bakker 1979). It is also hypothesized their role as antiviral drugs (Krenn et al. 2009; Sandler et al. 2020) and anticancer chemotherapeutic agents (Kaushik et al. 2018). Thinking of the structure of two of the most important ionophores, monensin A and valinomycin, respectively a polyether and a depsipeptide antibiotic, it is clear that they internally present many oxygen atoms (with related free electron doublets), indispensable for binding cations and transporting them through phospholipidic bilayers.

At a first glance, the two structures that make up the ivermectin formula do not have these chemical properties, nor those mentioned above, essential for a compound to be defined as ionophore. However, it can be hypothesized that two ivermectin molecules, reacting with each other in a “head-tail” mode, can create a complex suitable to be considered such (Fig. 2). This interaction could occur spontaneously or be mediated by the binding of the same molecules to some plasma transport proteins, in particular albumin (Klotz et al. 1990), which would have the role of positioning them in the correct way to obtain the proposed configuration.

Fig. 2
Possible interaction mechanism between two ivermectin molecules

As it can be seen, in this way, an internal cavity is formed: the oxygen atoms (indicated in red), now present in greater number, work as Lewis bases and could therefore coordinate a series of cations (Lewis acids). On the other hand, the –OH groups are highlighted in blue and they could have a decisive role in the stabilization of the new structure, with the establishment of chemical bonds between these functional groups: one or more –O– bridges (however, it is difficult the formation of ether bonds, since acid catalysis at high temperature is not possible under normal conditions, both in vitro and in vivo) or more probably hydrogen bonds could be formed, even among more molecular complexes of this type. However, the formation of other weak and strong interactions of various kinds cannot be excluded. Otherwise, specific cations could bind the two molecules in the proposed way, creating themselves the final structure and stabilizing it: there are examples already known in literature (Abbott et al. 1979). The external part of the complex, then, would already have in itself all the hydrophobic characteristics necessary to carry ions through the viral membrane. As a consequence, it would be determined an ionic imbalance between the external and internal environment, with the recall of water and consequent osmotic lysis. This would allow to neutralize the virus at an early stage of the infection, before; therefore, it can adhere to the host cells and enter it to exploit their biochemical machinery for the production of other viral particles. However, this hypothesis would concern only viruses without a proteic capsid, a structure that shows a certain resistance to osmotic pressure, even if to a lesser extent than a bacterial, fungal, or plant cell wall (Cordova et al. 2003). The new coronavirus is one of these, presenting only a phospholipid envelope in defense of the genetic material, where its few proteins are inserted and which it acquires in the act of exiting the infected cells (Sigrist et al. 2020). This unconventional electrolyte uptake mode could also affect the potential of the viral membrane, threatening its integrity and functionality. The same goes for the viral proteins present here. Furthermore, the concentration variation of some cations, thus determined, could inhibit some key enzymes in the viral replication, such as RNA-dependent RNA polymerases (RdRp) (te Velthuis et al. 2010), already used as pharmacological targets.

Another indication in favor of a possible ionophore role for ivermectin comes from the analysis of molecular similarity that can be carried out through the Drugbank database (www.drugbank.ca). By setting a minimum similarity threshold for ivermectin equal to 0.7, about 14 results are obtained. Among the various selected molecules, the majority of which have antiparasitic and antibiotic activity (already not only on the market but also in the study and experimentation phase), a compound that has high structural similarity is nystatin (score of 0.72), an antimycotic drug with an ionophoric activity at the plasma membrane level, where it forms channels (Yamasaki et al. 2011; Stillwell 2016; Rang 2015).

Immediately afterwards, with a slightly lower similarity, it can be find amphotericin B and natamycin, all pharmacological molecules of assured ionophoric activity (score of 0.71 and 0.706, respectively) (Stillwell 2016; Rang 2015; Ramos 1989; Ikehara et al. 1986).

In conclusion, pending computational simulations and chemical-physical laboratory analysis, this hypothesis could be applied to other known pharmacological molecules, in order to identify compounds with probable ionophore nature to be used in research and clinical practice.


A Combination of Ivermectin and Doxycycline Possibly Blocks the Viral Entry and Modulate the Innate Immune Response in COVID-19 Patients.

Dharmendra Kumar Maurya. Radiation Biology & Health Sciences Division, Bhabha Atomic Research Centre, Mumbai 400 085, India. https://chemrxiv.org/articles/preprint/A_Combination_of_Ivermectin_and_Doxycycline_Possibly_Blocks_the_Viral_Entry_and_Modulate_the_Innate_Immune_Response_in_COVID-19_Patients/12630539

Abstract
The current outbreak of the corona virus disease 2019 (COVID-19), has affected almost entire world and become pandemic now. Currently, there is neither any FDA approved drugs nor any vaccines available to control it. Very recently in Bangladesh, a group of doctors reported astounding success in treating patients suffering from COVID-19 with two commonly used drugs, Ivermectin and Doxycycline. In the current study we have explored the possible mechanism by which these drugs might have worked for the positive response in the COVID-19 patients. To explore the mechanism we have used molecular docking and molecular dynamics simulation approach. Effectiveness of Ivermectin and doxycycline were evaluated against Main Protease (Mpro), Spike (S) protein, Nucleocapsid (N), RNA-dependent RNA polymerase (RdRp, NSP12), ADP Ribose Phosphatase (NSP3), Endoribonuclease (NSP15) and methyltransferase (NSP10-NSP16 complex) of SARS-CoV-2 as well as human angiotensin converting enzyme 2 (ACE2) receptor. Our study shows that both Ivermectin and doxycycline
have significantly bind with SARS-CoV-2 proteins but Ivermectin was better binding than doxycycline. Ivermectin showed a perfect binding site to the Spike-RBD and ACE2 interacting region indicating that it might be interfering in the interaction of spike with ACE2 and preventing the viral entry in to the host cells. Ivermectin also exhibited significant binding affinity with different SARS-CoV-2 structural and non-structural proteins (NSPs) which have diverse functions in virus life cycle. Significant binding of Ivermectin with RdRp indicate its role in the inhibition of the viral replication and ultimately impeding the multiplication of the virus. Ivermectin also possess significant binding affinity with NSP3, NSP10, NSP15 and NSP16 which helps virus in escaping from host immune system. Molecular dynamics simulation study shows that binding of the Ivermectin with Mpro, Spike, NSP3, NSP16 and ACE2 was quiet stable. Thus, our docking and simulation studies reveal that combination of Ivermectin and doxycycline might be executing the effect by inhibition of viral entry and enhance viral load clearance by targeting various viral functional proteins.


Ivermectin: a systematic review from antiviral effects to COVID-19 complementary regimen. Fatemeh Heidary & Reza Gharebaghi
The Journal of Antibiotics (2020) Review Article Published: 12 June 2020 https://www.nature.com/articles/s41429-020-0336-z


The broad spectrum antiviral ivermectin targets the host nuclear transport importin α/β1 heterodimer, Antiviral Research, Volume 177, 2020, http://www.sciencedirect.com/science/article/pii/S0166354219307211


Ivermectin Inhibits Bovine Herpesvirus 1 DNA Polymerase Nuclear Import and Interferes With Viral Replication. Raza, S.; Shahin, F.; Zhai, W.; Li, H.; Alvisi, G.; Yang, K.; Chen, X.; Chen, Y.; Chen, J.; Hu, C.; Chen, H.; Guo, A. Microorganisms 2020, 8, 409. https://www.mdpi.com/2076-2607/8/3/409


Potential use of hydroxychloroquine, ivermectin and azithromycin drugs in fighting COVID-19: trends, scope and relevance. R. Choudhary, A.K. Sharma, New Microbes and New Infections, Volume 35, 2020,
http://www.sciencedirect.com/science/article/pii/S2052297520300366 


Hydroxychloroquine and ivermectin: A synergistic combination for COVID-19 chemoprophylaxis and treatment?, Angela Patrì, Gabriella Fabbrocini, Journal of the American Academy of Dermatology, 2020, http://www.sciencedirect.com/science/article/pii/S0190962220305570


Ivermectin and COVID-19: a report in Antiviral Research, widespread interest, an FDA warning, two letters to the editor and the authors’ responses, Mike Bray, Craig Rayner, François Noël, David Jans, Kylie Wagstaff, Antiviral Research, 2020, http://www.sciencedirect.com/science/article/pii/S0166354220302199

“Ivermectin’s key direct target in mammalian cells is a not a viral component, but a host protein important in intracellular transport (Yang et al., 2020); the fact that it is a host-directed agent (HDA) is almost certainly the basis of its broad-spectrum activity against a number of different RNA viruses in vitro (Tay et al., 2013; Yang et al., 2020). The way a HDA can reduce viral load is by inhibiting a key cellular process that the virus hijacks to enhance infection by suppressing the host antiviral response. Reducing viral load by even a modest amount by using a HDA at low dose early in infection can be the key to enabling the body’s immune system to begin to mount the full antiviral response before the infection takes control.”


The FDA-approved drug ivermectin inhibits the replication of SARS-CoV-2 in vitro, Leon Caly, Julian D. Druce, Mike G. Catton, David A. Jans, Kylie M. Wagstaff, Antiviral Research, Volume 178, 2020, http://www.sciencedirect.com/science/article/pii/S0166354220302011

Fig. 1. Ivermectin is a potent inhibitor of the SARS-CoV-2 clinical isolate Australia/VIC01/2020. Vero/hSLAM cells were in infected with SARS-CoV-2 clinical isolate Australia/VIC01/2020 (MOI = 0.1) for 2 h prior to addition of vehicle (DMSO) or Ivermectin at the indicated concentrations. Samples were taken at 0–3 days post infection for quantitation of viral load using real-time PCR of cell associated virus (A) or supernatant (B). IC50 values were determined in subsequent experiments at 48 h post infection using the indicated concentrations of Ivermectin (treated at 2 h post infection as per A/B). Triplicate real-time PCR analysis was performed on cell associated virus (C/E) or supernatant (D/F) using probes against either the SARS-CoV-2 E (C/D) or RdRp (E/F) genes. Results represent mean ± SD (n = 3). 3 parameter dose response curves were fitted using GraphPad prism to determine IC50 values (indicated). G. Schematic of ivermectin’s proposed antiviral action on coronavirus. IMPα/β1 binds to the coronavirus cargo protein in the cytoplasm (top) and translocates it through the nuclear pore complex (NPC) into the nucleus where the complex falls apart and the viral cargo can reduce the host cell’s antiviral response, leading to enhanced infection. Ivermectin binds to and destabilises the Impα/β1 heterodimer thereby preventing Impα/β1 from binding to the viral protein (bottom) and preventing it from entering the nucleus. This likely results in reduced inhibition of the antiviral responses, leading to a normal, more efficient antiviral response.


Ivermectin is a specific inhibitor of importin α/β-mediated nuclear import able to inhibit replication of HIV-1 and dengue virus. Kylie M. WAGSTAFF, Haran SIVAKUMARAN, Steven M. HEATON, David HARRICH and David A. JANS. Biochem. J. (2012) 443, 851–856. doi:10.1042/BJ20120150



PAK1-blockers: Potential Therapeutics against COVID-19, Hiroshi Maruta, Hong He, Medicine in Drug Discovery, Volume 6, 2020, http://www.sciencedirect.com/science/article/pii/S2590098620300269



Ivermectin: enigmatic multifaceted ‘wonder’ drug continues to surprise and exceed expectations. Crump, A. J Antibiot 70, 495–505 (2017). https://doi.org/10.1038/ja.2017.11

Antiviral: “Ivermectin has also been demonstrated to be a potent broad-spectrum specific inhibitor of importin α/β-mediated nuclear transport and demonstrates antiviral activity against several RNA viruses by blocking the nuclear trafficking of viral proteins. It has been shown to have potent antiviral action against HIV-1 and dengue viruses, both of which are dependent on the importin protein superfamily for several key cellular processes. Ivermectin may be of import in disrupting HIV-1 integrase in HIV-1 as well as NS-5 (non-structural protein 5) polymerase in dengue viruses”


Ivermectin, ‘Wonder drug’ from Japan: the human use perspective

Proc Jpn Acad Ser B Phys Biol Sci. 2011 Feb 10; 87(2): 13–28. doi: 10.2183/pjab.87.13

Abstract

Discovered in the late-1970s, the pioneering drug ivermectin, a dihydro derivative of avermectin—originating solely from a single microorganism isolated at the Kitasato Intitute, Tokyo, Japan from Japanese soil—has had an immeasurably beneficial impact in improving the lives and welfare of billions of people throughout the world. Originally introduced as a veterinary drug, it kills a wide range of internal and external parasites in commercial livestock and companion animals. It was quickly discovered to be ideal in combating two of the world’s most devastating and disfiguring diseases which have plagued the world’s poor throughout the tropics for centuries. It is now being used free-of-charge as the sole tool in campaigns to eliminate both diseases globally. It has also been used to successfully overcome several other human diseases and new uses for it are continually being found. This paper looks in depth at the events surrounding ivermectin’s passage from being a huge success in Animal Health into its widespread use in humans, a development which has led many to describe it as a “wonder” drug.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3043740


Ivermectin on Wikipedia https://en.wikipedia.org/wiki/Ivermectin