The disclosure features novel lipids and compositions involving the same. Nanoparticle compositions include a novel lipid as well as additional lipids such as phospholipids, structural lipids, and PEG lipids. Nanoparticle compositions further including therapeutic and/or prophylactics such as RNA are useful in the delivery of therapeutic and/or prophylactics to mammalian cells or organs to, for example, regulate polypeptide, protein, or gene expression.本發明提供新穎脂質及涉及該等新穎脂質之組合物。奈米粒子組合物包括新穎脂質以及其他脂質，諸如磷脂、結構脂質及PEG脂質。進一步包括諸如RNA之治療劑及/或預防劑的奈米粒子組合物適合用於將治療劑及/或預防劑遞送至哺乳動物細胞或器官，以例如調控多肽、蛋白質或基因表現。
