Rohto Pharmaceutical Co. said Tuesday it will begin a clinical trial in August using stem cells for a potential treatment for patients severely ill with COVID-19.

The Osaka-based drugmaker said it will be the first time in Japan that domestic stem cells have been used for such a clinical test.

To confirm the effectiveness and safety of this therapeutic approach, it will administer mesenchymal stem cells derived from adipose tissue from a donor to patients with severe cases of COVID-19, the respiratory disease caused by the novel coronavirus.

The trial is expected to run through December but if everything goes well it could end sooner, Rohto said, adding it will apply for the launch of the test to the health ministry in late June.

Under the plan, six COVID-19 patients who need to be on mechanical ventilators will receive an intravenous injection of the cells once a week for a total of four times. It is hoped that the injections will restore their lung tissues.

"It has been reported abroad that lives were saved (by the administration of stem cells)," Yoshiki Sawa, a professor at Osaka University's Graduate School of Medicine, who is cooperating in the trial, told a news conference. "We can assume it would be effective against pneumonia."

Mesenchymal stem cells have already been used in clinical studies for liver cirrhosis and heart failure, and they have also been applied on a trial basis overseas.