The US Food and Drug Administration (FDA) has approved a new drug produced by Genentech to treat acute uncomplicated influenza (flu) in patients 12 years of age and older who have been symptomatic for no more than 48 hours.

Xofluza (baloxavir marboxil), reportedly the first new antiviral flu treatment to be introduced in nearly 20 years, was discovered by Japanese drugmaker Shionogi and is being developed together by Genentech and its parent company Roche, along with Shionogi.

Under the terms of the agreement, the Swiss-based Roche group holds worldwide rights to the substance except in Japan and Taiwan, where Shionogi retains exclusive rights.

Genentech said it expects the single-dose treatment to be rolled out in the US over the coming weeks at a price of $150 or less, depending on insurance coverage.

The drug’s safety and efficacy were demonstrated in two randomized, controlled clinical trials of 1,832 patients each, in which participants were assigned to receive either Xofluza, a placebo, or another antiviral flu treatment within 48 hours of experiencing flu symptoms.

In both trials, patients treated with Xofluza had a shorter time to alleviation of symptoms compared with patients who took the placebo, Genentech said. The most common adverse reactions noted in patients taking Xofluza were said to include diarrhea and bronchitis.

 “With thousands of people getting the flu every year, and many people becoming seriously ill, having safe and effective treatment alternatives is critical. This novel drug provides an important, additional treatment option,” said FDA Commissioner Scott Gottlieb.

“When treatment is started within 48 hours of becoming sick with flu symptoms, antiviral drugs can lessen symptoms and shorten the time patients feel sick,” said Debra Birnkrant, director of the Division of Antiviral Products in the FDA’s Center for Drug Evaluation and Research.

“Having more treatment options that work in different ways to attack the virus is important because flu viruses can become resistant to antiviral drugs,” she said.