A framework for rational design of therapeutic siRNA conjugates Sponsor

About This Grant

PROJECT SUMMARY ABSTRACT Hundreds of proteins have been implicated in driving diseases, but many remain challenging to inhibit. Small interfering ribonucleic acids (siRNA) offer a versatile solution to silence proteins, even those considered “difficult- to-drug” by other therapeutic modalities. Although siRNA technology has existed for decades, delivery remains the greatest hurdle preventing siRNAs from achieving their widespread clinical potential. Excitingly, conjugating siRNA to cell-targeted delivery vehicles has recently enabled several hepatocyte-targeted siRNA-conjugate therapies to reach the clinic. However, the progress of targeted siRNA therapy in cells outside the liver remains limited. The Momin lab aims to address the barriers to extra-hepatic siRNA-conjugates using antibody-siRNA conjugates (ARC) as a tool. Since siRNAs are too large and charged to diffuse across a cell membrane, their uptake requires receptor- mediated endocytosis. Abundant and rapidly internalized receptors are the key to achieving siRNA uptake. However, current methods cannot quantify the dynamic flux of all receptors without major cell perturbation. To address this methodological gap, we propose (Project 1) to develop a radically new method leveraging our chemistry expertise and recent findings. Our goal is to fuel the discovery of promising new receptors for siRNA conjugates, including ARCs. Upon internalization, siRNAs are trapped in endosomes, with <1% productively escaping by unknown mechanisms. Amplifying endosomal escape without cytotoxicity is a formidable hurdle. Escape efficiency varies with both siRNA design and cell properties, yet a predictive understanding of endosomal escape across the vast feature space of siRNA conjugates and cell types is still missing. This insight has been elusive in part because of challenges in manufacturing variants of siRNA conjugates and measuring endosomal escape. Timely advances have allowed my lab to overcome these hurdles. So now we propose (Project 2A) to create a pharmacokinetic model that predicts endosomal escape of ARCs and (Project 2B) to decipher the cell regulation that governs their silencing. Our goal is to help clarify the still-mysterious mechanisms of endosomal escape and inform future siRNA conjugate design. The Momin lab’s overarching goal is to create a framework to propel forward next-generation siRNA conjugates. The objective of this proposal is to fill key methodological and knowledge gaps by drawing on our expertise in chemistry, ARC engineering, and modeling, and our ongoing collaborations. Given the potential of siRNA therapy, our proposal to make siRNA conjugate design more straightforward will spark their translation across diverse diseases and thus falls squarely within the mission of NIGMS.