A drug delivery device comprising or adapted to receive a drug-filled cartridge, comprising: - a housing , - a piston rod adapted to engage and axially displace a piston in a loaded cartridge in a distal direction to thereby expel a dose of drug from the cartridge, - a transmission member defining an axis, - a drive spring coupled to the transmission member, - a drive member in engagement with the piston rod and adapted to be rotated by the transmission member to thereby move the piston rod distally during expelling, - dose setting means allowing a user to simultaneously set a dose amount to be expelled and strain the drive spring correspondingly by rotation of the transmission member, the dose setting means comprising a dose setting member which during dose setting is rotationally coupled to the transmission member and adapted to rotate in a first direction to set a dose, - a releasable ratchet mechanism allowing the dose setting member to be rotated in the first direction to a set rotational position, - a releasable clutch mechanism adapted to rotationally lock the drive member relative to the housing during dose setting, - release means actuatable between a dose setting mode and an expelling mode, characterized in that the clutch mechanism comprises: - a relative to the housing axially non-moveable clutch member , and - a relative to the housing rotationally non-moveable locking member , wherein during dose setting and dose expelling the clutch member is rotationally locked to the drive member , wherein the transmission member is actuatable between a dose setting state in which it is allowed to rotate relative to the clutch member , and an expelling state in which it is rotationally coupled to the clutch member, wherein the locking member is actuatable between a dose setting state in which it is in rotationally locked engagement with the clutch member , and an expelling state in which it is rotationally decoupled from the clutch member, wherein, when the release means is actuated from the dose setting mode to the expelling mode: - the transmission member is actuated from its dose setting state to its expelling state, - the locking member is actuated from its dose setting state to its expelling state, and - the ratchet mechanism is released, whereby the strained drive spring is allowed to rotate the transmission member and the drive member and thereby move the piston rod distally. - a housing , - a piston rod adapted to engage and axially displace a piston in a loaded cartridge in a distal direction to thereby expel a dose of drug from the cartridge, - a transmission member defining an axis, - a drive spring coupled to the transmission member, - a drive member in engagement with the piston rod and adapted to be rotated by the transmission member to thereby move the piston rod distally during expelling, - dose setting means allowing a user to simultaneously set a dose amount to be expelled and strain the drive spring correspondingly by rotation of the transmission member, the dose setting means comprising a dose setting member which during dose setting is rotationally coupled to the transmission member and adapted to rotate in a first direction to set a dose, - a releasable ratchet mechanism allowing the dose setting member to be rotated in the first direction to a set rotational position, - a releasable clutch mechanism adapted to rotationally lock the drive member relative to the housing during dose setting, - release means actuatable between a dose setting mode and an expelling mode, characterized in that - a relative to the housing axially non-moveable clutch member , and - a relative to the housing rotationally non-moveable locking member , - the transmission member is actuated from its dose setting state to its expelling state, - the locking member is actuated from its dose setting state to its expelling state, and - the ratchet mechanism is released, <EOS>