(194w) Antibody Dual-Conjugate Delivery for Endosomal Escape of siRNA

Efficient delivery of targeted, systemic, siRNA-based therapeutics continues to be dominated by nanoparticle carriers, and continues to be limited to liver cell targets. Protein-based bioconjugate carriers have the potential to circumvent accumulation in the liver through the use of scFv or full-length antibodies for a plethora of receptor and cell type targets. Many of these conjugates though, still suffer from low potency, presumably due to a lack of endosomal escape.

Commonly used antibody-siRNA conjugates, and many nanoparticle systems, utilize highly cationic peptides polymers both for non-covalent complexation with siRNA as well as endosomal disruption. However, cationic carriers can lead to toxic side effects, dissociation in serum, and rapid systemic clearance. Neutral endosome-disrupting agents can alleviate these effects, but cannot complex with RNA. Therefore, they must be covalently incorporated into the delivery system without inhibiting binding and internalization.

We propose here a co-delivery strategy utilizing two antibodies, covalently linked to either an siRNA or endosomal escape agent, to work together to facilitate efficient knockdown of a target gene. We have built a system using antibodies targeting either recycling or lysosomal targeting pathways, and a model endosomal escape agent, Listeriolysin O (LLO), connected via a reversibly attenuating linker for endosomal disruption with reduced outer membrane toxicity. We anticipate that the “plug-and-play” nature of this method will allow for better understanding of the key variables, such as endocytic pathway, endosomal escape agent, and linker chemistry, in building an efficient siRNA delivery vehicle.