Fujifilm Holdings Corp. said Thursday it expects to complete clinical tests in Japan of the antiviral drug Avigan, a potential candidate treatment for COVID-19, in September, after a delay caused by difficulty in securing enough patient data.

The last patient will participate in the clinical study on Sunday and all necessary data will have been collected a month later, Fujifilm director Junji Okada said.

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

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Fujifilm began clinical tests in March to see if Avigan is effective in treating patients with COVID-19, a respiratory disease caused by the novel coronavirus, with an eye to completing them by June. But the number of confirmed coronavirus cases in Japan was on a downtrend, making it difficult to meet the enrollment target of 96.

In recent weeks, Japan has seen infections resurging in various parts of the nation as economic and social activities resume.

"Although we've taken more time than planned, we will complete clinical tests as soon as possible and seek approval," President and Chief Operating Officer Kenji Sukeno said during an online press briefing on the firm's earnings.

Prime Minister Shinzo Abe had expressed hope to have the drug approved in May but a Japanese university's interim report, released in mid-May, did not indicate clear efficacy of Avigan in treating COVID-19. The drug, also known as favipiravir, was developed by Fujifilm Toyama Chemical Co., a subsidiary of Fujifilm Holdings.

Elsewhere, a Philippine health official recently said a clinical trial in the country will start soon.