JNJ-8003 is a potent and orally active non-nucleoside RSV polymerase inhibitor with an IC50 of 0.29 nM. JNJ-8003 targets the L protein polymerase complex of RSV (IC50 = 0.67 nM), and blocks the transcription and replication of the viral genome by inhibiting the activity of RNA-dependent RNA polymerase (RdRp) . JNJ-8003 displays subnanomolar activity in vitro as well as prominent efficacy in mice and a neonatal lamb models. JNJ-8003 can be used for the study of respiratory syncytial virus (RSV) [1][2].