Cassella AG, formerly Leopold Cassella & Co. and Cassella Farbwerke Mainkur AG, commonly known as Cassella, was a German chemical and pharmaceutical company with headquarters in Frankfurt am Main. Founded in 1798 in the Frankfurt Jewish Alley by Leopold Cassella, Cassella operated as an independent company until 1995 and was one of many predecessor companies of today's Sanofi. Its history is closely tied to its former owners, the prominent Jewish German Gans family.