The ability to deliver small protein scaffolds intracellularly could enable the targeting and inhibition of many therapeutic targets that are not currently amenable to inhibition with small-molecule drugs. Here, we report the engineering of small protein scaffolds with anionic polypeptides (ApPs) to promote electrostatic interactions with positively charged nonviral lipid-based delivery systems. Proteins fused with ApPs are either complexed with off-the-shelf cationic lipids or encapsulated within ionizable lipid nanoparticles for highly efficient cytosolic delivery (up to 90%). The delivery of protein inhibitors is used to inhibit two common proto-oncogenes, Ras and Myc, in two cancer cell lines. This report demonstrates the feasibility of combining minimally engineered small protein scaffolds with tractable nanocarriers to inhibit intracellular proteins that are generally considered "undruggable" with current small molecule drugs and biologics.
Keywords: Myc; Ras; intracellular delivery; lipid nanoparticles; protein delivery; undruggable proteome.