The therapeutic potential of small interfering RNA (siRNA) has since long been recognized. However, its clinical translation is limited by various extra-and intracellular drug delivery barriers. The delivery of siRNA is typically facilitated by its encapsulation in lipid-or polymer nanoparticles (nanomedicines, NMs), which is essential to improve in vivo biodistribution and enhance delivery across cellular membranes. Unfortunately, upon endocytosis by target cells, NMs are largely trafficked toward lysosomes for degradation and conventional strategies to stimulate endosomal escape typically fall short, highlighting the need for alternative strategies. Given the inevitable lysosomal accumulation of NM, we propose to exploit lysosomes as intracellular drug depots, using existing cationic amphiphilic drugs (CADs) as adjuvants to trigger lysosomal membrane permeabilization (LMP) and stimulate the release of siRNA in the cytosol. First, the most potent CAD adjuvants to induce LMP and enhance NM-mediated cytosolic siRNA delivery will be identified. Second, we aim to exploit the physicochemical lipid-like properties of CADs to develop CAD-liposomes for in vivo siRNA delivery, in which the CAD is used both as a structural and functional component. Finally, the value of CAD adjuvants for siRNA delivery will be assessed in a mouse model of metastatic breast cancer and refractory asthma, applying systemic and pulmonary administration, respectively.