Roche’s expected Tamiflu replacement has already shown solid efficacy in otherwise healthy people. Now, a phase 3 study also showed that this new flu drug worked in people at high risk for serious flu complications, padding the drug’s case of helping Roche reclaim ground lost to Tamiflu generics.
Baloxavir marboxil, marketed in Japan as Xofluza, bested placebo in time to improvement of influenza symptoms in the phase 3 study, meeting its primary endpoint. It also demonstrated superior efficacy compared to Tamiflu in some secondary endpoints, including time to stop virus release and reducing viral levels in the body.
“Baloxavir marboxil is the first antiviral to show a clinically meaningful benefit in people who are most susceptible to complications from the flu, including older people and those living with certain medical conditions,” said Sandra Horning, M.D., Genentech’s chief medical officer and head of global product development, in a statement.
The CAPSTONE-2 study enrolled over 2,000 participants defined by the CDC as at high risk of flu complications that can lead to hospitalization or even death. They include people 65 years or older and those who suffer from diseases like asthma, diabetes and heart disease.
However, in that Tuesday release, Genentech didn’t specify whether Xofluza was better than Tamiflu at quickly relieving flu symptoms or at reducing the rate of flu complications in those vulnerable patients. In its previous phase 3 trial in flu patients who were otherwise healthy, Xofluza didn’t significantly reduce the duration of symptoms compared to Tamiflu. Xofluza does have a dosing advantage, having achieved those benefits with a single dose, compared to Tamiflu's twice-daily, five-day regimen.
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The FDA is accelerating review on the drug’s use in uncomplicated influenza based on the CAPSTONE-1 study, with a decision set for Dec. 24. If approved, it will be the first flu drug with a novel mechanism of action in nearly 20 years. Horning said the company will submit the new phase 3 results to drug regulators to discuss next steps.
Genentech obtained commercial rights to Xofluza through a 2016 licensing deal with its developer Shionogi, which holds rights to the drug in Japan and Taiwan, as well as certain co-promotion rights in the U.S.
On Roche’s first-quarter earnings call, pharmaceuticals division chief Dan O’Day said Xofluza “has the potential to become a full replacement for Tamiflu.” Roche needs the Tamiflu follow-on to fill the sales gap widened by Tamiflu generics. In 2017, the first full year Tamiflu suffered copycat erosion, Tamiflu sales plummeted 33% to CHF 535 million ($537 million). The past severe flu season likely expanded the entire patient base and helped Tamiflu achieve a 11% year-over-year increase in first-quarter sales.
Editor's Note: The story has been updated to show that Xofluza comes in one dose, not one pill, as the dosage is based on body weight.