Roche’s influenza treatment Xofluza – a one-dose pill that can clear flu symptoms within days – may cause a mutation of the virus that leads to drug resistance, researchers reported.

French drugs and healthcare group Sanofi signed a rights deal with Roche for Tamiflu in the United States.

Roche said the Swiss drugmaker’s new one-dose flu medicine Xofluza was comparable to the company’s 20-year-old drug Tamiflu in reducing the duration of symptoms of the viral disease, citing a study of the drug in children aged one to 12 years old.