A cartridge assembly (300) for a drug delivery device is proposed, comprising a cartridge (301) containing a drug (307), the cartridge comprising a dispensing end (306), a cartridge holder (302), the cartridge holder defining an interior cartridge holding section (303), where the cartridge is arranged within the cartridge holding section, and a fixing feature (322), wherein the fixing feature comprises a fixing surface (324), in particular a radially oriented surface, which is arranged to abut a cartridge surface (313) of the cartridge, in particular a radially oriented surface, to prevent removal of the cartridge from the cartridge holder such that the cartridge is permanently secured in the cartridge holder, wherein the cartridge surface is a proximal surface which faces away from the dispensing end of the cartridge, wherein the cartridge surface is arranged between the dispensing end of the cartridge and the end opposite of the dispensing end, and wherein the fixing feature is integrated into the cartridge holder.
