To fully realize the therapeutic potential of proteins, exogenous proteins need to access intracellular targets. Since the vast majority of proteins cannot spontaneously cross cell membranes, a range of delivery platforms have been developed. These delivery platforms have not been efficiently implemented due to cytotoxicity, lack of generality, low potency, or poor in vivo activity. The Liu team has discovered Aurein 1.2, a peptide that substantially increases cytosolic protein delivery by enhancement of endosomal escape and have demonstrated its activity in vivo. This platform can be used to deliver functional therapeutics proteins.