Ulcer drug found to be potent weapon against virus

Jane Cheung

An ulcer drug that is cheaper than the antiviral remdesivir can be used to treat Covid-19, the University of Hong Kong says.

The drug RBC - ranitidine bismuth citrate - has been tested on hamsters and researchers found it can be as effective as the antiviral drug remdesivir, if not more, in suppressing the viral load.

Clinical trials could start in Hong Kong if it sees a fourth wave of infections but details on the dosage and whether it would be used on patients with serious or mild symptoms have yet to be confirmed.

The university expected RBC to cost less than US$750 (HK$5,850) per treatment - a quarter of the US$3,000-per-course of remdesivir - which is being clinically trialed in many countries.

Clinical trials for remdesivir in Hong Kong were completed in May and in July the drug was "limited registered" in the SAR to be used on patients with serious symptoms.

The university's microbiology team led by government adviser for Covid-19 Yuen Kwok-yung and the chemistry team led by chair professor Sun Hongzhe said RBC has been used to treat Helicobacter pylori bacterial infection in the digestive system for decades.

Experts found the bismuth metal-carrying drug can stop the coronavirus's double-stranded DNA from unwinding into single strands, which is a crucial step for virus replication before it infects other cells.

"RBC is the first discovered drug to target the helicase protein on the surface of Covid-19 virus," Sun said.

"We are applying for a patent in the United States on this usage."

In an animal experiment to compare the effectiveness of RBC and remdesivir, the team administered the drugs to three groups of hamsters - four to six in each group - 24 and 48 hours after being infected by Covid-19.

On the fourth day of infection, most of the viruses in their nasal cavities and lungs had been cleared, indicating RBC is highly effective in eliminating the virus.

Researchers also observed the drug helped alleviate inflammatory response triggered by the infection.

RBC is commonly used as an oral drug to treat ulcer on the surface of the digestive tract.

Since the Covid-19 virus causes infections in cells, the team is looking to improve the composition of the drug so it can be intravenously injected like remdesivir.

The university's post-doctoral fellow in chemistry, Wang Runming, said RBC is already widely used for other medical purposes, proving it is safe, and it can complete clinical trials quicker than newly invented drugs.

A clinical assistant professor of microbiology, Jasper Chan Fuk-woo, said RBC can be added to the cocktail therapy against the coronavirus as it works in a different mechanism to other drugs such as interferon and protease inhibitors that have been used to treat Covid-19 patients.

He said RBC has not been reported with adverse effects under doctor's prescription but warned the drug can cause toxicity and disruption of the nervous system upon overdose.

"Therefore, our preliminary idea is to use it on patients for a short period of time," Chan said. "As Covid-19 induces an acute infection in the respiratory tract, it's best to administer the drug in the first few days of infection."

jane.cheung@singtaonewscorp.com