Drug and pharmaceutical giant Johnson & Johnson has agreed to pay $1.75 billion in cash to acquire Alios BioPharma, a private biotechnology company developing a medicine to combat a serious childhood respiratory infection for which there is no current treatment, the companies announced Tuesday.

South San Francisco-based Alios currently is in Phase II of development of an oral antiviral medication called AL-8176 for RSV, or respiratory syncytial virus, a disease that generally afflicts infants and children under the age of 5. The company also is developing a portfolio of potential treatments for other viral respiratory infections, including influenza, rhinovirus and coronavirus, according to Alios.