Developing Autophagy-Targeting Chimeras and Optimizing Cell Penetration of Large-Molecule Therapeutics

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The Kritzer lab focuses on inhibiting protein-protein interactions involved in autophagy. Autophagy is a protein degradation pathway that is active in all human cells, and inhibiting autophagy shows promise as a therapy for late-stage cancers especially in combination with DNA-damaging chemotherapies. Autophagy research and drug development currently rely on compounds that inhibit autophagy indirectly. Better, more specific inhibitors of autophagy would be broadly adopted. A large amount of genetics and cell biology work supports that inhibiting the LC3/GABARAP family of proteins can block autophagy selectively. In one series of projects, we will develop novel stapled peptide and small molecule inhibitors of LC3/GABARAP and evaluate them in models of late-stage cancers and other diseases. Because of our expertise in compounds that bind LC3/GABARAP proteins, we also propose to evaluate related compounds as autophagy-targeting chimeras (AUTACs). These compounds could be used to selectively degrade any proteins in the cell, similar to proteolysis-targeting chimeras (PROTACs) but potentially more versatile and easier to develop. Based on strong preliminary data that validate the AUTAC concept, we will develop novel AUTACs and demonstrate their ability to degrade endogenous proteins, unlocking a broad new area for drug development in targeted protein degradation. Over the course of developing stapled peptides as autophagy modulators, the Kritzer lab encountered a common problem in the field: how to measure the amount that actually reaches the cytosol. In an independent series of projects, the Kritzer lab has developed novel assays that quantitate the cytosolic penetration of large-molecule therapeutics. In this proposal, we describe new opportunities to address challenging problems in drug development for large-molecule therapeutics. We describe new methods to measure penetration to different cellular compartments in any cell type, including primary cells. We also describe a molecular evolution approach to develop a new “turn-on” assay that measures the real-time kinetics of cytosolic penetration. We describe pooled CRISPR screens to reveal the cellular components that mediate endosomal escape. Finally, we describe a novel screening platform that will allow us to screen thousands to millions of molecules at a time for those that are most cell-penetrant; the new screen will be incorporated into a design-test-learn cycle to produce data-driven design algorithms for cytosol-penetrant molecules. All together, these data will represent a huge leap in our understanding of structure-penetration relationships for several classes of large-molecule therapeutics.