Docosanoic acid conjugation to siRNA enables functional and safe delivery to skeletal and cardiac muscles

Annabelle Biscans,Jillian Caiazzi,Nicholas Mchugh,Vignesh Hariharan,Manish Muhuri,Anastasia Khvorova

doi:10.1016/j.ymthe.2020.12.023

Annabelle Biscans, Jillian Caiazzi + Show 4 more

Open Access

https://doi.org/10.1016/j.ymthe.2020.12.023

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Abstract

Oligonucleotide therapeutics hold promise for the treatment of muscle- and heart-related diseases. However, oligonucleotide delivery across the continuous endothelium of muscle tissue is challenging. Here, we demonstrate that docosanoic acid (DCA) conjugation of small interfering RNAs (siRNAs) enables efficient (~5% of injected dose), sustainable (>1 month), and non-toxic (no cytokine induction at 100 mg/kg) gene silencing in both skeletal and cardiac muscles after systemic injection. When designed to target myostatin (muscle growth regulation gene), siRNAs induced ~55% silencing in various muscle tissues and 80% silencing in heart, translating into a ~50% increase in muscle volume within 1 week. Our study identifies compounds for RNAi-based modulation of gene expression in skeletal and cardiac muscles, paving the way for both functional genomics studies and therapeutic gene modulation in muscle and heart.

Highlights

Each lipid conjugate was attached to the 30 end of the small interfering RNAs (siRNAs) sense strand, which tolerates a range of covalent modifications .7,39,40 siRNAs were fully chemically modified for maximal stability and minimal innate immune activation.[11,12,13,14,17,18,19,43]
The majority of injected siRNAs accumulate in liver and kidneys, a small fraction of compounds was retained in muscle tissues (Figure S1D)
Our previous reports demonstrate that conjugate chemical structure, which defines serum protein binding and clearance kinetics,[33,34,37,41,44,45,46] drives tissue distribution, and that docosanoic acid (DCA) conjugation may be optimal for siRNA delivery to muscle

Summary

Introduction

Oligonucleotide therapeutics holds promise for the treatment of muscle-related diseases.[26,27] When injected locally, oligonucleotides can achieve significant target gene reduction in a small portion of muscle tissue,[28,29,30] but its limited distribution minimizes potential therapeutic use. Systemic delivery of oligonucleotides to extrahepatic tissues, like muscles, remains a challenge

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