Twelve species of pyridobenzazoles and pyrimidobenzimidazole were examined as inhibitors of the replication of respiratory syncytial virus (RSV) in HeLa cells. From the pyridobenzazoles studied, 2-benzamido-4-cyano-1-oxo-1H,5H-pyrido[1,2-alpha]benzimidazol emerged as a potent inhibitor of the RSV. B …