A clinical trial for the flu drug Avigan yielded inconclusive results as a treatment for COVID-19, Japanese researchers said on Friday.

Although patients given the Fujifilm Holdings Corp. product early in the trial showed more improvement than those who got delayed doses, the results did not reach statistical significance, Fujita Health University researcher Yohei Doi said.

The results, announced at a news conference Friday, followed the completion of a clinical trial conducted between March and May on 89 patients across Japan.

Prime Minister Shinzo Abe had said he hoped the drug would be approved as a COVID-19 treatment in May, but a shortage of patients delayed the progress of clinical trials. It has been approved as a COVID-19 treatment in Russia and India.

Known generically as favipiravir, Avigan was developed by a subsidiary of Fujifilm and approved in Japan as an emergency influenza treatment in 2014.

Interest in the drug soared in March after a Chinese official said it appeared to help patients recover from COVID-19. It is now the subject of at least 25 clinical trials around the world. The government called on Fujifilm to triple national stockpiles of the drug and pledged to give it away to countries asking for it.

Concerns remain about the drug as it has been shown in studies to cause birth defects in animals.