SAN FRANCISCO — With progress toward a universal flu vaccine on the march, the global fight against influenza is building momentum. But as epidemics still lead to millions of severe cases of the infection each year, hospitalization and death are still stark realities for many patients. Now Roche Group and its partner, Shionogi & Co. Ltd., could soon add a new weapon to America's annual battle with the illness: a single-dose, oral treatment called baloxavir marboxil. Data the company is presenting at IDWeek on Saturday suggest the new medicine – up for priority review at the FDA with a Dec. 24 PDUFA date – could potentially offer significant benefits to both people at high risk for flu complications and those infected with type B strains, a subgroup where some antivirals have shown only limited efficacy or inconclusive data.

Baloxavir, a cap-dependent endonuclease protein inhibitor, is already marketed by Shionogi in Japan as Xofluza. But if successful at the FDA, the filing would open the door for Roche's Genentech Inc. unit to market it at home where the company views it as "an attractive asset with the potential to replace Tamiflu," said Genentech's executive vice president of global development and chief medical officer, Sandra Horning, during a recent company meeting.

With the Capstone-1 study having already set the foundation for a potential approval for treatment of acute, uncomplicated influenza in people 12 years and older, the partners are now focused on broadening evidence for baloxavir's application in wider populations. That's where Genentech's IDWeek news comes in. With the presentation of data from Capstone-2, the drug's backers showed that, in a less healthy group, baloxavir reduced the time to improvement of influenza symptoms by 29.1 hours vs. placebo (median time of 73.2 hours vs. 102.3 hours; p<0.0001).

The trial enrolled people at high risk of serious complications from the flu, a group that includes adults 65 years of age or older and those who have conditions such as asthma, chronic lung disease, morbid obesity or heart disease. In the subpopulation of trial participants with influenza type B, the study also showed baloxavir was more effective than Tamiflu in reducing the time to improvement of symptoms, cutting the time to improvement by a median 27 hours (median time of 74.6 hours vs. 101.6 hours; p<0.05).

Mark Eisner, Genentech's vice president of product development immunology, infectious disease and ophthalmology, told BioWorld that "it's very exciting that we're seeing strong results in terms of improvement of influenza symptoms in this high-risk population, because there's no drug currently approved that has this population in the label as an efficacious one."

The 65-and-older group is especially important because, according to the CDC, between about 70 percent and 85 percent of seasonal flu-related deaths and between 54 percent and 70 percent of seasonal flu-related hospitalizations occur in that group.

Established flu vaccines can prevent 70 percent to 90 percent of flu-specific illnesses. Despite that, the ongoing need for additional flu treatments was made especially clear last flu season, when, according to early estimates by the CDC, more than 900,000 people were hospitalized and more than 80,000 people died from flu. But there are also other reasons that patients, Roche and its customers might welcome baloxavir. First, a single-dose therapy would likely prove attractive to people taking Tamiflu for its recommended flu treatment course, twice daily, for five days. Second, though Tamiflu resistance is a relatively small problem in the U.S., it isn't unknown. "That said, when you talk to public health experts at CDC or BARDA, they are very concerned with the potential for any single agent, like neuraminidase inhibitors," Eisner said.

Baloxavir is also active against an emerging and particularly virulent form of bird flu, H7N9, which has been a big worry for public health officials. While it appears to only be transmitted between birds and people, not person to person yet, Eisner said that "if it was able to mutate and adapt itself to spread person to person, baloxavir could be a very important treatment for that."

In addition to working with Shionogi to advance the drug globally outside Japan and Taiwan, Genentech is also working with the Biomedical Advanced Research and Development Authority (BARDA), which is providing funding to support the development of the drug for severely ill hospitalized people with flu, with the potential for funding of other studies.