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

TOKYO - A Japanese medical university said Friday a clinical study of the antiviral drug Avigan has failed to demonstrate a clear efficacy in treating coronavirus patients at an early stage of the disease.

Fujita Health University said that the difference seen between the patients who took the drug immediately and those who took it later was not statistically relevant in assessing the effectiveness of the drug, developed by a subsidiary of Fujifilm Holdings Corp.

"There has been a tendency to bring down fever or eradicate the virus" in those administered with the drug, Yohei Doi, a professor at the university who led the study, said during an online press conference.

But he also said the enrollment of 89 patients in the study was too small to yield a statistically meaningful difference.

Avigan, also known as favipiravir, has been seen as a possible treatment for COVID-19, the respiratory disease caused by the novel coronavirus.

Fujifilm Toyama Chemical Co., the developer of the drug, is separately conducting its own clinical tests of Avigan, with results yet to be released.

Prime Minister Shinzo Abe had expressed hope to see the homegrown drug approved by the end of May but gave up the target after the university's interim report, released in mid-May, did not indicate clear efficacy in treating the disease.

In Tokyo, Chief Cabinet Secretary Yoshihide Suga said at a press conference, "There's no change in our policy to approve the drug if its efficacy (against the coronavirus) and its safety are confirmed."

In the study at the university, 89 infected patients with mild or no symptoms at 47 facilities across Japan took part.

Excluding one patient who decided to pull out in the middle of the study, 88 were divided into two groups -- one given Avigan from the first day of the study and another starting to take the drug from the sixth day.

The two groups were compared for the percentage of those who saw the coronavirus disappear from their bodies as well as for the period of time it took for their fevers to alleviate.

Of those who had Avigan administered from the first day, 66.7 percent saw the virus disappear by the morning of the sixth day, while 56.1 percent of those with delayed doses showed similar signs of recovery by the same morning.

It took an average 2.1 days and 3.2 days for the first and second groups to have their fevers lower, respectively, the university said.

As Avigan can inhibit the replication of the virus in cells, experts say it may bring about improvements in patients but it cannot be administered to expectant mothers or women who are likely to become pregnant as it may cause birth defects.