A cartridge assembly (300) for a drug delivery device (1) is provided, 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, a fixing member (322),wherein the fixing member comprises a fixing surface (323), in particular a radially oriented surface, which is arranged to abut a cartridge surface (313) of the cartridge, in particular a radially oriented surface, 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 member comprises a securing surface (324) which is arranged to abut a holder surface (325) of the cartridge holder to prevent removal of the cartridge from the cartridge holder such that the cartridge is permanently secured in the cartridge holder, and wherein the holder surface is a distal surface of the cartridge holder. Further, a drug delivery device and a method for assembling the cartridge assembly are provided.
