The invention provides a drug delivery device adapted to receive a cartridge, the cartridge being adapted to receive a needle assembly. The drug delivery device comprises a front-loaded cartridge holder adapted to receive and hold a cartridge in a mounted state and being actuatable between an open loading state and a closed operational state. The drug delivery device is further provided with blocking means configured to prevent the cartridge holder from being actuated between the closed and the open state when a cartridge with a mounted needle assembly is held in a mounted position.
