Pleuromutilin and its derivatives are antibacterial drugs that inhibit protein synthesis in bacteria by binding to the peptidyl transferase component of the 50S subunit of ribosomes. This class of antibiotics includes the licensed drugs retapamulin (approved for topical use in humans), valnemulin and tiamulin (approved for use in animals) and the investigational drugs azamulin and lefamulin (BC-3781).