An assembly for a drug delivery device (1) is described which comprises a cartridge (4) containing a plurality of doses of a drug and a piston rod (9) adapted and arranged to expel drug from the cartridge (4) during a dose delivery operation of the assembly, the piston rod (9) comprising a thread (9a). The assembly further comprises a nut member (13), wherein the nut member (13) is adapted and arranged to be rotated with respect to the piston rod (9) about a rotational axis (7) during a dose setting operation of the assembly, the nut member (13) thereby being axially displaced along the piston rod (9) from a start position towards an end position with respect to the piston rod (9) due to mechanical cooperation of the nut member (13) with the thread (9a). The assembly further comprises a last dose stop mechanism adapted and arranged to prevent a user from setting a dose of the drug which exceeds a remaining amount of drug in the cartridge (4), the last dose stop mechanism comprising at least one first interaction member (16) and at least one second interaction member (17) provided by the piston rod (9) and at least one first stop member (18) and at least one second stop member (19) provided by the nut member (13), wherein the interaction members (16, 17) and the stop members (18, 19) are configured to mechanically cooperate with one another when the nut member (13) is in the end position with respect to the piston rod (9) such that further relative movement of the nut member (13) and the piston rod (9) for setting a dose of the drug is prevented. Furthermore, a drug delivery device (1) is described.La présente invention concerne un ensemble pour dispositif dadministration de médicament (1 ), lensemble comprenant une cartouche (4) contenant une pluralité de doses dun médicament et une tige de piston (9) conçu et agencé pour expulser un médicament de la cartouche (4) lors dune opération de distribution de dose de lensemble, la tige de piston (9) comprenant un filetage
