Fujifilm Holdings Corp. will continue clinical tests of its anti-flu drug Avigan, a candidate treatment for the novel coronavirus, beyond the initially scheduled end in June due to a lack of sufficient data, a company source said Monday.

Fujifilm planned to finish the clinical tests it started in March in Japan by the end of this month but has seen a delay as recent falls in the number of confirmed infections made it difficult to reach the enrollment target of 96 patients, the source said.

Fujifilm said it does not know when the clinical tests of the drug, developed by its unit Fujifilm Toyama Chemical Co. and also known as favipiravir, will finish.

After the government of Prime Minister Shinzo Abe gave up on getting approval for the drug by the end of May, the aim was to complete clinical trials this month.

Drugmakers around the world are scrambling to develop treatments and vaccines for the new coronavirus, which has infected nearly 7 million people globally, while the disease it causes, COVID-19, has killed around 400,000.

Many countries are focusing on drugs like Gilead Sciences Inc's antiviral remdesivir and some are using the anti-malaria drug hydroxychloroquine, touted by U.S. President Donald Trump. Abe's government has championed Japanese candidate Avigan.

Countries that have succeeded in curbing infections have sometimes paradoxically found it difficult to sustain clinical trials because of dwindling sample sizes for patients.