(Corrects to show reduces duration of symptoms to about 2.2 days (not begins to improve symptoms after about 2.2 days), paragraph 10)
ZURICH, July 17 (Reuters) - Swiss drugmaker Roche's hopes of regaining ground in the influenza market have been boosted after a late-stage study showed its investigational drug baloxavir marboxil reduced symptoms in people at high risk of complications.
Analysts, however, said there was only a marginal benefit while there were cheaper generic copies of Roche's older Tamiflu medicine.
In severe flu outbreaks, millions of people can get sick, resulting in hospitalisations and hundreds of thousands of deaths, in particular among older people or those with compromised immune or respiratory systems.
Roche's Capstone-2 trial focused on adults aged 65 or older, or those who have conditions such as asthma, chronic lung disease, diabetes, or heart disease.
It evaluated a single dose of the new medicine compared with a placebo, as well as Tamiflu which requires a twice-daily, five-day regimen.
Baloxavir marboxil is approved in Japan but not yet in the United States, although regulators have accelerated their review and could make a decision by Dec. 24.
Roche has partnered with Japan's Shionogi & Co., Ltd. to develop the drug, with an eye to augmenting patent-expired Tamiflu with a more-convenient alternative. In 2017, Tamiflu sales tumbled 33 percent to 535 million Swiss francs ($536.99 million), as cheaper generics muscled in on the market.
“Baloxavir marboxil is the first antiviral to show a clinically meaningful benefit in people who are most susceptible to complications from the flu," said Sandra Horning, Roche's chief medical officer, adding the company would now go to health regulators with the results.
Roche did not give specifics for the Capstone-2 study results.
In a previous trial for acute, uncomplicated influenza in people aged 12 and older, called Capstone-1, the medicine was shown to reduce the duration of flu symptoms to about 2.2 days, around a day earlier than in patients who received a placebo.
That study also showed a reduction in the period in which a person is infectious, compared with both a placebo and Tamiflu.
Some analysts say the limited improvement over Tamiflu would be unlikely to cause a sea change in flu treatment.
"We see the bulk of the flu market further dominated by Tamiflu generics," analysts at Baader Helvea said on Tuesday, adding that the new medicine would likely gain sales at the expense of current Tamiflu revenue. ($1 = 0.9963 Swiss francs) (Reporting by John Miller; Editing by Stephen Coates and Kirsten Donovan)