An auto-injector comprising (a) a cassette unit (1; 101; 201; 301; 501; 601) comprising a cassette unit housing (20; 120; 220; 320; 520; 620) defining a cassette unit housing cavity, said cassette unit housing cavity arranged for receipt of a syringe (10; 110; 210; 310; 510) comprising: a barrel (12; 112; 212; 312; 512) for containing a volume of a liquid drug formulation; a hollow needle (14: 114; 214; 314; 514; 614) at a front end of said barrel, said hollow needle defining a needle tip (15; 115; 215; 315; 515; 615) for dispensing of said liquid drug formulation; and a plunger (18; 118; 218; 318) that is axially movable within the barrel; and (b) a drive unit (70; 170) comprising: a drive unit housing defining a docking cavity and a needle delivery aperture, wherein said docking cavity is arranged for docking receipt of the cassette unit at a docking position, whereupon said cassette unit and / or a syringe is movable from a rest position, in which the needle tip of the syringe is within the drive unit housing to a use position, in which the needle tip protrudes from said needle delivery aperture; and a drive arrangement, said drive arrangement comprising one or more electrically powered sources of axial drive; a first drive transfer element (82b; 179) for transferring said axial drive to the cassette unit and /or to the syringe for advancing the syringe to said use position; and a second drive transfer element (83c; 187) for subsequently transferring the axial drive to a plunger of the syringe for moving the plunger into the barrel of the syringe to eject at least part of said volume of liquid drug formulation, wherein said drive unit is arranged for initial receipt of the cassette unit at an intermediate pre-docking position and for subsequent transport of the cassette unit to the docking position. (a) a cassette unit (1; 101; 201; 301; 501; 601) comprising a cassette unit housing (20; 120; 220; 320; 520; 620) defining a cassette unit housing cavity, said cassette unit housing cavity arranged for receipt of a syringe (10; 110; 210; 310; 510) comprising: a barrel (12; 112; 212; 312; 512) for containing a volume of a liquid drug formulation; a hollow needle (14: 114; 214; 314; 514; 614) at a front end of said barrel, said hollow needle defining a needle tip (15; 115; 215; 315; 515; 615) for dispensing of said liquid drug formulation; and a plunger (18; 118; 218; 318) that is axially movable within the barrel; and a barrel (12; 112; 212; 312; 512) for containing a volume of a liquid drug formulation; a hollow needle (14: 114; 214; 314; 514; 614) at a front end of said barrel, said hollow needle defining a needle tip (15; 115; 215; 315; 515; 615) for dispensing of said liquid drug formulation; and a plunger (18; 118; 218; 318) that is axially movable within the barrel; and (b) a drive unit (70; 170) comprising: a drive unit housing defining a docking cavity and a needle delivery aperture, wherein said docking cavity is arranged for docking receipt of the cassette unit at a docking position, whereupon said cassette unit and / or a syringe is movable from a rest position, in which the needle tip of the syringe is within the drive unit housing to a use position, in which the needle tip protrudes from said needle delivery aperture; and a drive arrangement, said drive arrangement comprising one or more electrically powered sources of axial drive; a first drive transfer element (82b; 179) for transferring said axial drive to the cassette unit and /or to the syringe for advancing the syringe to said use position; and a second drive transfer element (83c; 187) for subsequently transferring the axial drive to a plunger of the syringe for moving the plunger into the barrel of the syringe to eject at least part of said volume of liquid drug formulation, a drive unit housing defining a docking cavity and a needle delivery aperture, wherein said docking cavity is arranged for docking receipt of the cassette unit at a docking position, whereupon said cassette unit and / or a syringe is movable from a rest position, in which the needle tip of the syringe is within the drive unit housing to a use position, in which the needle tip protrudes from said needle delivery aperture; and a drive arrangement, said drive arrangement comprising one or more electrically powered sources of axial drive; a first drive transfer element (82b; 179) for transferring said axial drive to the cassette unit and /or to the syringe for advancing the syringe to said use position; and a second drive transfer element (83c; 187) for subsequently transferring the axial drive to a plunger of the syringe for moving the plunger into the barrel of the syringe to eject at least part of said volume of liquid drug formulation, one or more electrically powered sources of axial drive; a first drive transfer element (82b; 179) for transferring said axial drive to the cassette unit and /or to the syringe for advancing the syringe to said use position; and a second drive transfer element (83c; 187) for subsequently transferring the axial drive to a plunger of the syringe for moving the plunger into the barrel of the syringe to eject at least part of said volume of liquid drug formulation,