Gaithersburg-based MedImmune says it has received fast-track designation from the Food and Drug Administration for its MEDI8897, a drug being developed to prevent respiratory infections in infants and young children caused by respiratory syncytial virus. “We are working with a sense of urgency to develop a next-generation RSV [treatment] that we believe has the potential to benefit hundreds of thousands more infants, both in the U.S. and around the world,” said Steve Projan, senior vice president of research and development and infectious diseases and vaccines at MedImmune. “If successful, the fast-track designation will enable us to more quickly deliver a preventative solution.”