American pharmaceutical company Pfizer said it has begun human safety testing of a new pill to treat the coronavirus that could be used at the first sign of illness.

“Tackling the COVID-19 pandemic requires both prevention via vaccine and targeted treatment for those who contract the virus. Given the way that SARS-CoV-2 is mutating and the continued global impact of COVID-19, it appears likely that it will be critical to have access to therapeutic options both now and beyond the pandemic,”said Mikael Dolsten, Pfizer’s Chief Scientific Officer, in a statement.

The oral antiviral clinical candidate “PF-07321332”, a SARS-CoV2-3CL protease inhibitor, has demonstrated potent in vitro anti-viral activity against SARS-CoV-2, as well as activity against other coronaviruses, the company said in statement.

This Phase 1 trial is being conducted in the United States.

The Phase 1 trial is a randomised, double-blind, sponsor-open, placebo-controlled, single and multiple dose-escalation study in healthy adults evaluating the safety, tolerability and pharmacokinetics of PF-07321332.

The initiation of this study is supported by preclinical studies that demonstrated the antiviral activity of this potential first-in-class SARS-CoV-2 therapeutic designed specifically to inhibit replication of the SARS-CoV2 virus.

The structure of PF-07321332, together with the pre-clinical data, will be shared in a COVID-19 session of the Spring American Chemical Society meeting on April 6.

Pfizer, in collaboration with German company BioNTech, was the first pharmaceutical company to receive emergency use authorization from the Food and Drug Administration (FDA) for a COVID-19 vaccine.

Currently, the only FDA-approved antiviral treatment for COVID-19 is Gilead’s Remdesivir.