Drug delivery devices, sealing members for containers housed within such drug delivery devices, and related methods of assembly are disclosed. The drug delivery device may include a housing, a container disposed in the housing and having an interior volume, a drug disposed in the interior volume, and a septum. The container may have an opening formed in an end surface and which communicates with the interior volume. The septum may include a proximal end inserted through the opening into the interior volume of the container. Additionally, the septum may include a distal end having a flange disposed outwardly of the proximal end and contacting the end surface of the container. At least an end portion of the flange may be made of a material that is permeable to a gaseous sterilizing agent.
