Photo/Illutration The National Center for Global Health and Medicine in Tokyo (Asahi Shimbun file photo)

A team of researchers has discovered two chemical compounds that can block the novel coronavirus from replicating--potentially a major milestone in the development of new drugs to fight the virus.

Results from a test tube experiment show that the chemical compounds identified have little toxicity and are more effective when combined with an existing remedy, according to the team led by scientists from the National Center for Global Health and Medicine.

“While we have no remedies yet that can fundamentally help patients recover, we have found prospective candidate substances,” said Hiroaki Mitsuya, who spearheaded the research.

The team focused on a chemical compound that can inhibit the activity of protease, enzymes that break up proteins. It was effective when used against another kind of coronavirus: the one responsible for SARS.

The researchers created about 400 kinds of chemical compounds artificially that work similarly. The scientists injected them into cells infected with the new coronavirus--the one that causes COVID-19--and studied how they affected the virus’ proliferation.

The team found two chemical compounds had blocked the virus from multiplying effectively, called “GRL-1720” and “GRL-2420 (5h).”

GRL-2420 (5h) was able to almost completely block the virus from replicating when used alongside remdesivir, a drug used as a treatment for COVID-19. 

Mitsuya said they are seeking to develop new drugs and continue with their research through animal testing.

The research paper was published in the British scientific journal Nature Communications on Jan. 28, at the following website: (