What New Flu Drug Means for Other Treatments, Vaccine

The FDA’s approval of a first influenza drug in more than 20 years is expected to be a boon in treatment of the flu and will likely impact sales of Tamiflu (oseltamivir).

While there are other antivirals on the market, Xofluza (baloxavir marboxil) is novel because it is a single-dose tablet and targets a different enzyme in the replication of the virus than other antivirals, Peter Gilmore, principal at KPMG Strategy, tells Drug Topics.

“This drug targets the process of how the flu virus transcribes its genetic material to replicate itself, while Tamiflu targets an enzyme tied to the release of viral particles from the infected cell,” Gilmore says.

“Xofluza is a first-in-class medicine with a novel mechanism of action that inhibits cap-dependent endonuclease in the polymerase acidic (PA) protein, an enzyme essential for viral replication,” says the drug’s manufacturer, Shionogi & Co., Ltd., in a statement.

Gilmore says that though both Xofluza and Tamiflu must be administered within at least two days of symptom development, Xofluza will benefit from its single-dose tablet formula.

The drug, marketed in partnership with Roche and Genentech, will be available in the United States in the coming weeks, Shionogi says.

According to Gilmore, Roche’s executives expect Xofluza, which will sell for a list price of $150 before any promotions or rebates, to fully replace sales of Tamiflu. This is due in part to Tamiflu’s falling sales because of a generic version that the FDA approved in 2016.

Global sales of Tamiflu were down 33% in 2017 and the drug was not even mentioned in Roche’s 2018 nine-month results in October, according to Gilmore. “The cost advantage of generic Tamiflu may still create a drag on sales for Xofluza due to payer formulary pressures, but it remains to be seen how much of an impact that will be,” he says.

Initial projections forecast Xofluza sales to reach $655 million globally by 2024, John Santilli, president of Market Access Intelligence, tells Drug Topics.

“Xofluza side-effects are also expected to be less than those experienced with Tamiflu,” Santilli adds. Diarrhea and bronchitis are the most common side effects, according to Shionogi.

“The FDA approved Xofluza after Shionogi demonstrated that patients treated with Xofluza had a shorter time to alleviation of symptoms than those who took the placebo,” the agency says.  “With thousands of people getting the flu every year, and many people becoming seriously ill, having safe and effective treatment alternatives is critical,” says FDA Commissioner Scott Gottlieb, MD, in an FDA statement.

However, influenza treatments are not a substitute for yearly flu vaccinations, Gottlieb says.

“Flu season is already well underway, and the CDC recommends getting vaccinated by the end of October, as the seasonal flu vaccine is one of the most effective and safest ways to protect yourself, your family, and your community from the flu and serious flu-related complications. Yearly vaccination is the primary means of preventing and controlling flu outbreaks.”

“Flu vaccines are typically less expensive than influenza drugs, so prevention can be less costly; however, flu shots are not fool-proof. The vaccine formulations each season are educated guesses about the prevalence of certain strains of flu,” Gilmore says.

According to Gilmore, last year’s flu season was more deadly than usual with 80,000 fatalities.

“It is always helpful to have additional treatment options that can shorten the severity and duration of flu symptoms,” Gilmore says.