American pharmaceutical company Pfizer has begun clinical trials on a coronavirus oral anti-viral drug, according to reports on Tuesday.

The phase one US trial of the drug, PF-07321332, is a type of medicine called protease inhibitors, which works by inhibiting an enzyme that the virus needs to replicate in human cells.

"Tackling the COVID-19 pandemic requires both prevention via vaccine and targeted treatment for those who contract the virus," Pfizer’s Chief Scientific Officer Mikael Dolsten said in a statement. "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.”

After developing a two-dose vaccine with its German partner, BioNTech, the company is planning to develop mRNA technology on its own to make new vaccines for other viruses.

The mRNA technology allows pharmaceutical companies to consider the method used in other medical areas beyond vaccines, which is potentially in the billions of dollars in investment.

Coronavirus cases in March increased for the first time since January in the US -- the worst-hit country by the pandemic.

While the US has seen more than 543,000 coronavirus-related deaths, the number of cases in about a year has totaled almost 30 million, according to Johns Hopkins University data.

Out of 156 million distributed doses of vaccines in the US, 126 million have been administered as of early Monday, but fewer than 45 million people, or 13.5% of the population, have received two doses, according to the Centers for Disease Control and Prevention./aa