DSPE-PEG5000-GALA is a PEG compound composed of DSPE and the lung endothelial targeting peptide, GALA. GALA, a 30-amino acid pH-sensitive amphipathic peptide, serves as a lung endothelial targeting ligand. In acidic conditions (pH 5.0), GALA undergoes a structural change from a random coil to an α-helix, leading to endosomal membrane destabilization and fusion. Liposomes modified with GALA are capable of crossing pulmonary endothelial cells via clathrin-dependent endocytosis and transcytosis, and they accumulate specifically in the lungs following intravenous injection. DSPE-PEG5000-GALA is applicable for drug delivery purposes.