Researchers have said that an HIV (human immunodeficiency virus) drug could stop many coronavirus diseases, including the SARS-CoV-2 variants when given to infected cells at the right concentration.

The researchers have previously shown that a booster drug called -- "cobicistat", which is normally used to reinforce the effect of anti-HIV drugs, could have antiviral properties against a SARS-CoV-2 variant circulating in Europe in early 2020.

In the study, published in the journal Antiviral Research, the researchers investigated whether the anti-SARS-CoV-2 properties of cobicistat were maintained against the key variants of concern (VOCs) of SARS-CoV-2 and other coronaviruses, including Middle East respiratory syndrome coronavirus (MERS-CoV).

With a death rate of over 30 per cent, MERS-CoV circulates throughout the Middle East, Africa, and South Asia without a vaccine or specific treatment.

The researchers also compared cobicistat's effects to those of ritonavir, a structurally similar molecule that is also one of the components of Paxlovid, the current gold standard for antiviral treatment of SARS-CoV-2.

Using automated image analysis for screening and parallel comparison of the anti-coronavirus effects of cobicistat and ritonavir, the researchers discovered that cobicistat and ritonavir both act against all eight VOCs of SARS-CoV-2 tested as well as other human coronaviruses, including MERS-CoV.

"Our study shows that the CYP3A inhibitors ritonavir and, to a higher extent, cobicistat can be repurposed as broadly effective anti-coronavirus agents at concentrations potentially achievable in vivo by adjusting currently approved dosing regimens," the researchers said.

The findings suggested that cobicistat is more effective than ritonavir. Both drugs demonstrated anti-coronavirus activity in vitro at well-tolerated doses that were higher than those currently used for anti-HIV drug booster activity and in Paxlovid.

Cobicistat and ritonavir both inhibited coronavirus replication when used at these higher doses, both alone and in combination with other drugs.