The continued spread of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) results in many new infections, which often manifests as coronavirus disease 2019 (COVID-19). The economic devastation and over 3.8 million deaths have lent urgency to the task of countering this pandemic.
A new study, released as a preprint on bioRxiv* server, shows that a combination of the biological interferon-α and the small molecule nafamostat are effective against SARS-CoV-2 infection in vitro, as well as in vivo.
In the absence of any effective and safe antiviral drugs, useful by themselves to inhibit the virus, attention has turned to the potential utility of combinations of drugs. Synergism is a potential advantage of such combinations since it can allow lower drug dosages and fewer side effects. Moreover, it could provide broader coverage of emerging variants of concern (VOCs) of the virus that resist neutralization by existing therapeutic monoclonal or natural antibodies.
Several earlier studies by the same team of researchers have shown that pairing remdesivir with camostat and IFN-α inhibited SARS-CoV-2 infection in human lung organoids, the latter being effective in hamsters as well.
Synergistic effects in cells and in animal models
Nafamostat is a camostat analog, the latter being a drug originally approved as a short-acting anticoagulant and also used to treat pancreatitis. It is now being repurposed for the treatment of COVID-19 and is undergoing clinical trials for this use, as are IFN-α and its pegylated forms.
The combination of pegylated IFN-α (Pegasys) and nafamostat was found to prevent the death of SARS-CoV-2-infected cells, though Pegasys) was less efficient at inhibiting SARS-CoV-2 replication compared to the non-pegylated form. Conversely, nafamostat has higher efficacy than camostat.
The combination showed strong synergy, showing that the concentration of each component could be reduced while maintaining high efficacy against the virus.
In a hamster model, pre-treatment with these two drugs protected the animals against infection when exposed to the virus intranasally. Compared to controls that received only one drug, which received neither the drugs nor the virus, the combination inhibited the replication of the virus more efficiently.
The synergistic nature of the combination in vivo was also shown with this experiment.
How do the drugs act?
The activity of IFN-α is to upregulate a number of genes, including endothelial plasminogen activator inhibitor (SERPINE1), which is known to inhibit transmembrane protease serine 2 (TMPRSS2) as well. This enzyme is key to activating the viral spike protein in order to mediate virus-host cell fusion and viral entry into the cell.
Nafamostat also inhibits this enzyme. The additive action of both molecules on the same host factor may account for the synergistic efficiency of this combination.
When compared with a regimen containing a SERPINE1 inhibitor as well as the above two drugs, the reduction in viral RNA synthesis mirrors that induced by nafamostat alone. This indicates that SERPINE1 is required for IFN-α to exert its antiviral activity. It also underlines the beneficial effect of using multiple TMPRSS2 inhibitors to prevent or suppress the virus.
Other beneficial effects of the combination
Moreover, while nafamostat is a coagulation inhibitor, suppressing the overactive coagulation functions seen with severe COVID-19, SERPINE1 is known to induce a higher risk of thrombosis. The combination could thus cancel out this known adverse effect of SERPINE1 induction by IFN-α.
The combination of these drugs can also reduce the odds of other adverse effects. It may also be possible to use different routes of administration and thus improve the convenience of use.
What are the implications?
This drug cocktail may also be useful against other TMPRSS2-dependent viruses, including other coronaviruses and influenza viruses. Further studies should focus on identifying other synergistic combinations of antiviral drugs, and thus help to protect against this and other emerging viruses.
The response time to newer viral diseases could thus be shortened significantly, with effective drugs becoming available to cover for the period required to develop vaccines and thus save many lives.
Thus, our study may provide a proactive solution for the ongoing pandemic and potential future coronavirus outbreaks, which is still urgently required in many parts of the world,” write the researchers.
bioRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.