Shionogi’s flu drug wins green light in Japan, but U.S. approval not likely until 2019

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Shionogi's Roche-partnered Xofluza, a one-time, single-dose flu drug, was approved in Japan. (Wikimedia Commons)

As one of the worst flu seasons in years ravages the Northern Hemisphere, a powerful flu drug developed by Shionogi has been approved in Japan under a fast-track process. However, the U.S. may not see it before next winter.

The new drug, called Xofluza (baloxavir marboxil), works by inhibiting cap-dependent endonuclease, which the flu virus relies on to duplicate in the human body.

A phase 3 trial showed that it can effectively kill the flu virus in about 24 hours, while it takes Roche’s popular Tamiflu 72 hours to achieve that. Killing the virus faster means less opportunity for passing it to others, the company told The Wall Street Journal.

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Both Tamiflu and Xofluza require a similar amount of time to completely alleviate symptoms, but what’s more important from a compliance perspective is that Xofluza is a one-time, single-dose regimen. In comparison, patients are recommended to take Tamiflu twice daily for five days.

Roche has seen significant declines in Tamiflu sales in recent years, which probably prompted it to reach its Xofluza licensing deal with Shionogi in 2016. Under that deal, Roche obtained commercialization rights outside of Japan and Taiwan.

Crashed by generics competition in the U.S., worldwide sales of Tamiflu dropped a whopping 33% year-over-year to CHF 535 million ($568 million) in 2017.

Shionogi plans to file for U.S. approval later this year but expects a decision no earlier than 2019, according to the WSJ. The Japanese drugmaker also retains certain co-promotion rights in the U.S. under the licensing agreement.

RELATED: Flu vaccines 36% effective this season, triggering increased interest in cell-based production: CDC interim report

The Japanese approval came as the U.S. is experiencing a serious flu season. By Feb. 17, the virus had led to 97 deaths among children in the U.S., and flu-related hospitalizations also reached a record high, according to the CDC.

Vaccines are recommended as the first line of defense against the flu, but a CDC interim report found that this year’s flu shots are only 36% effective so far, while protection against a malicious H3N2 strain was only 25%.

Given the difficulty around designing the right seasonal flu vaccines to match the circulating strains, many groups are now looking to develop universal flu vaccines that can hold off a variety of flu strains for multiple seasons. But such vaccines are still in early development and could take years to reach the market.

Several other companies are also working on new drugs against influenza A. Johnson & Johnson’s pimodivir significantly decreased viral load over seven days compared to placebo, recent phase 2b results showed.