Drug filled delivery assembly

A drug delivery assembly, comprising:

• a housing,
• a piston axially displaceable in the housing from an initial position,
• a variable volume reservoir formed by the housing and the piston and in an initial state containing a fluid drug,
• an exterior fluid inlet arranged in or configured to be arranged in fluid communication with the reservoir,
• a fluid outlet arranged in or configured to be arranged in fluid communication with the reservoir,
• biasing means configured for moving the piston forwards, and
• releasable retaining means configured for retaining the biasing means in an energized state,
• wherein the piston comprises a fluid conduit in flow communication with the exterior fluid inlet, the piston being moveable from the initial position in which there is no fluid communication between the fluid conduit and the fluid outlet and to a connected position in which a direct fluid communication is provided between the fluid outlet and the fluid conduit and thereby between the exterior fluid inlet and the fluid outlet,
• whereby the biasing means in the energized state is allowed to move the piston forwards to expel fluid drug from the reservoir when the retaining means is released.