A drug delivery device for separating and delivering a number of pre-settable doses of a liquid drug formulation out of an undivided reservoir, the drug delivery device comprising: a housing, a movable member, which is arranged to be rotatable in two opposite rotational directions with respect to the housing, i.e. in an incrementing direction and a decrementing direction, the movable member being operatively coupled to an energy storage member and biased to rotate into the decrementing direction by energy stored or storable in the energy storage member, wherein rotation of the movable member in the incrementing direction increases the energy stored in the energy storage member, a locking system, the locking system comprising a locking feature (62, 46, 160, 161), a block feature (42, 65, 66, 677), and a release member (70, 80), wherein the locking feature is arranged to cooperate with the block feature to form a releasable locking interface, the releasable locking interface being configured such that, when the releasable locking interface is established, rotational movement of the movable member relative to the housing is blocked in the decrementing direction and wherein, when the releasable locking interface is released, the movable member is rotatable in the decrementing direction, wherein the release member is rotatable relative to the housing and/or the locking feature between a first angular position and a second angular position, wherein, in the first angular position, the releasable locking interface is established, and, in the second angular position, the releasable locking interface is released at least temporarily where the drug delivery device is configured such that the rotation of the release member from the first angular position to the second angular position causes the release of the releasable locking interface, and wherein the drug delivery device is switchable between two different axial configurations, a decrementing configuration and a driving configuration, wherein, in the decrementing configuration, the releasable locking interface is established, and, in the driving configuration, the releasable locking interface is released, and wherein, for switching between the driving configuration and the decrementing configuration, the locking feature (62, 46, 160, 161) and the block feature (42, 65, 66, 677) are axially displaceable relative to one another. a housing, a movable member, which is arranged to be rotatable in two opposite rotational directions with respect to the housing, i.e. in an incrementing direction and a decrementing direction, the movable member being operatively coupled to an energy storage member and biased to rotate into the decrementing direction by energy stored or storable in the energy storage member, wherein rotation of the movable member in the incrementing direction increases the energy stored in the energy storage member, a locking system, the locking system comprising a locking feature (62, 46, 160, 161), a block feature (42, 65, 66, 677), and a release member (70, 80), wherein the locking feature is arranged to cooperate with the block feature to form a releasable locking interface, the releasable locking interface being configured such that, when the releasable locking interface is established, rotational movement of the movable member relative to the housing is blocked in the decrementing direction and wherein, when the releasable locking interface is released, the movable member is rotatable in the decrementing direction, wherein the release member is rotatable relative to the housing and/or the locking feature between a first angular position and a second angular position, wherein, in the first angular position, the releasable locking interface is established, and, in the second angular position, the releasable locking interface is released at least temporarily where the drug delivery device is configured such that the rotation of the release member from the first angular position to the second angular position causes the release of the releasable locking interface, and wherein the drug delivery device is switchable between two different axial configurations, a decrementing configuration and a driving configuration, wherein, in the decrementing configuration, the releasable locking interface is established, and, in the driving configuration, the releasable locking interface is released, and wherein, for switching between the driving configuration and the decrementing configuration, the locking feature (62, 46, 160, 161) and the block feature (42, 65, 66, 677) are axially displaceable relative to one another.