The invention is directed to a dose setting mechanism for a drug delivery device (1) comprising a primary drug delivery assembly (3) and a secondary drug delivery assembly (4), wherein the dose setting mechanism comprises a primary dose dial component (21) for setting a dose in the primary drug delivery assembly (3) and a secondary dose dial component (29) for setting a dose in the secondary drug delivery assembly (4), wherein the primary dose dial component (21) and the secondary dose dial component (29) are configured to rotate during dose setting. For effective combined therapy treatment, a gear mechanism (7) is configured such that in a first phase of the dose setting, rotation of the primary dose dial component (21) is transferred to the secondary dose dial component (29) and such that in a second phase of the dose setting, the secondary dose dial component (29) is decoupled from the primary dose dial component (21) such that rotation of the primary dose dial component (21) is prevented from being transferred to the secondary dose dial component (29). The invention is also directed to a respective drug delivery device.Linvention se rapporte à un mécanisme de sélection de dose pour dispositif dadministration de médicament (1) comprenant un ensemble principal dadministration de médicament (3) et un ensemble secondaire dadministration de médicament (4), le mécanisme de sélection de dose comprenant un composant de sélection de dose principal (21) permettant de sélectionner une dose au niveau de lensemble principal dadministration de médicament (3) et un composant de sélection de dose secondaire permettant de sélectionner une dose (29) au niveau de lensemble secondaire dadministration de médicament (4), le composant de sélection de dose principal (21) et le composant de sélection de dose secondaire (29) étant conçus pour tourner pendant la sélection de la dose. En vue dun traitement efficace par thérapie combinée, un mécanisme dengrenage (7) est conçu de telle sorte
