Gamithromycin is a semi-synthetic macrocyclic lactone belonging to the azalide class derived from erthyromycin, typified by azithromycin. The synthesis of gamithromycin involves a ring expansion using a Beckmann rearrangement to produce the 15-membered dibasic macrolide. Gamithromycin provides a broader spectrum of action, higher acid stability and improved bioavailability compared to older analogues of the erythromycin class and has been exclusively developed for animal health applications.