The Japanese government is already planning to approve the antiviral drug Avigan as a COVID-19 treatment in November even before its developer has filed for regulatory review, government sources said Saturday.

Under that plan, the review of the influenza drug Avigan as a new coronavirus treatment will be completed in an unprecedentedly short screening period of three weeks once Fujifilm Toyama Chemical Co. submits a new drug application, expected in mid-October, the sources said, raising concerns about whether its safety and efficacy will be thoroughly scrutinized.

Supplied photo shows tablets of the anti-influenza drug Avigan. (Photo courtesy of Fujifilm)(Kyodo)

Despite some concerns about the drug's side effects such as birth defects, the Japanese government has been eager to get the health ministry to approve it as a coronavirus treatment and offer it to other countries.

Former Prime Minister Shinzo Abe came under fire in May for hyping up Avigan for treating COVID-19, saying then the drug's approval was expected within that month.

According to the sources, the government had already mapped out the drug's approval process by the time Fujifilm Toyama Chemical, a subsidiary of Fujifilm Holdings Corp., disclosed data from clinical studies on Sept. 23.

Three weeks would be an unusually short period for a review of a new drug even if it receives a fast-track designation which is meant to speed up approval of orphan drugs and treatments for serious conditions. A new drug review typically takes about a year.

There have also been concerns about whether the developer can collect enough clinical data to confirm Avigan's safety and benefit, given the limited number of patients available in its domestic clinical trial.

According to data on 156 patients without severe conditions released by Fujifilm Toyama Chemical in late September, those administered Avigan showed improvement in their conditions after 11.9 days, shorter than the 14.7 days for those in a placebo group.

On Saturday, nearly 600 new coronavirus cases were reported in Japan, bringing the cumulative total to over 86,000. The death toll has topped 1,600.