Oligomer-lipid 7C1 is an ionizable lipid produced through the reaction of low-molecular-weight polyamines with lipids. It effectively binds siRNA to form nanoparticles. In non-human primates, Oligomer-lipid 7C1 induces RNA interference in endothelial cells of multiple organs. Additionally, it delivers siRNA to endothelial cells, promoting improved endothelial function in models of murine vascular permeability, emphysema, primary tumor growth, and metastasis.