The White House has picked another drug as a possible coronavirus treatment—and it’s pressuring the FDA to allow use of the yet-unapproved therapy during the pandemic.

The Trump administration is asking its drug regulators to authorize Fujifilm’s flu antiviral Avigan (favipiravir) for emergency use against the novel coronavirus, Politico reported, citing three officials familiar with the discussions and internal documents.

President Donald Trump has previously talked up other drugs as promising against SARS-CoV-2, including a family of anti-malaria meds known as chloroquine, which the FDA just cleared for emergency use without solid clinical evidence of its effect on COVID-19.

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In Avigan’s case, Japanese Prime Minister Shinzo Abe has publicly endorsed the med. His government is proceeding with clinical trials aimed at winning its approval as a coronavirus treatment and will start ramping up production soon, Abe recently said at a press conference, according to Nikkei Asian Review.

Though approved in Japan and elsewhere, the drug isn't cleared for any use in the U.S. The FDA has in the past rejected it on worries about side effects, Politico said.

In China, where Avigan only won its first approval for flu during the early days of the pandemic, an official at the country’s Science and Technology Ministry has labeled it as “clearly effective” in treating COVID-19, adding that the agency has recommended it to health authorities for consideration in its treatment guidelines.

RELATED: Fujifilm ramps up production of flu drug Avigan as possible COVID-19 treatment

The country’s National Medical Products Administration conditionally approved Zhejiang Hisun’s Avigan version, which the company offers under a licensing agreement with Fujifilm, in mid-February.

Although the specific indication is influenza, the move is widely viewed as opening the door to Avigan as a potential coronavirus drug because it came on the heels of news suggesting it worked better than AbbVie’s HIV combo Kaletra in a COVID-19 clinical trial co-run by the National Clinical Research Center for Infectious Diseases.

Are existing clinical data enough in determining the old flu drug’s anti-COVID-19 benefits? Not necessarily.

First, in that Kaletra head-to-head study in Shenzhen touted by China’s Science and Technology Ministry, both drugs were paired with interferon-alpha. Results showed the 35 patients who got Avigan had their virus cleared after a median four days, significantly shorter than the 11 days observed among 45 Kaletra patients. The Avigan arm also saw better changes in chest CT scans. Fourteen days after treatment, the improvement rates were 91.4% versus 62.2% for Avigan and Kaletra, respectively. In addition, fewer adverse reactions were reported for Avigan (11.43%) and Kaletra (55.56%)

However, as Evercore ISI analyst Umer Raffat noted in a March 18 memo to clients, “there is a very important limitation of this trial: it was non-randomized.” Patients enrolled earlier in the trial got Kaletra, while those entered later landed with Avigan, which prompted Raffat to ask, “did more clinical experience by February help?” Moreover, Raffat noted that the study excluded more severe patients with oxygen saturation levels below 93%.

RELATED: Did chloroquine really fail a COVID-19 study—or was the trial design to blame?

Then, a bigger, open-label, randomized study in the city of Wuhan—the epicenter of the outbreak at the time—slightly undermined Avigan’s case. According to results published in the preprint site medRxiv, when nearly 240 patients were all included for analysis, the clinical recovery rates at day 7 were roughly similar between those who got Avigan and those treated with another influenza med, Arbidol. The numbers were 61.21% for Avigan and 51.67% for Arbidol.

As the researchers noted, the difference was more pronounced in moderate COVID-19 patients. In that group, the clinical recovery rate was 55.86% and 71.43% for Aribol and Avigan, respectively. Nevertheless, as CLSA analyst Tony Ren previously argued, it is the severe patients who are really in need of an effective treatment.

Kaletra, Arbidol and chloroquine are all included in Chinese authorities’ COVID-19 treatment guidelines.

RELATED: Roche launches clinical trial of COVID-19 pneumonia hopeful Actemra after backing from China

In contrast to government backing in Japan and China, South Korea recently decided against using Avigan as a coronavirus drug because of a lack of clinical data and potential side effects.

“Avigan has not only not shown efficacy during test studies but also there is not data on clinical trials conducted on patients,” infectious disease expert Oh Myoung-don said, as quoted by Korean news agency Yonhap. “The drug has also shown serious side effects, such as fetal deaths in animal studies.”

Fujifilm, the FDA and HHS have spent several weeks discussing potential clinical trials of Avigan in the U.S., Politico reported, based on internal summary of related deliberations.

Other than that, a Chinese research team is currently testing Avigan in combination with Roche’s arthritis med Actemra. The IL-6 inhibitor was recently added to China’s treatment guidelines to help control potentially life-threatening immune overreaction called cytokines storm in serious COVID-19 patients.