Abstract: Described are implantable devices having expandable reservoirs for the sustained release of therapeutic agents. The device is configured to be at least partially implanted in an eye and includes a retention structure and a penetrable element coupled to and extending within at least a portion of the retention structure. A porous drug release mechanism is positioned in fluid communication with an outlet of the device; and a reservoir having a volume configured to contain one or more therapeutic agents is in fluid communication with the outlet through the porous drug release mechanism. The device is at least partially inserted along an axis of insertion. The reservoir enlarges from an insertion configuration having a first three-dimensional shape to an expanded configuration having a second three-dimensional shape, the second three-dimensional shape being eccentrically positioned relative to the axis of insertion.