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Published on: April 16, 2019
Guanabenz (Wytensin™) selectively enhances uptake and efficacy of hydrophobically modified siRNAs
Maire F Osborn1, Julia F Alterman1, Mehran Nikan1
1RNA Therapeutics Institute, Department of Molecular Medicine, University of Massachusetts Medical School, Worcester, MA 01605, USA.
Abstract:
One of the major obstacles to the pharmaceutical success of oligonucleotide therapeutics (ONTs) is efficient delivery from the point of injection to the intracellular setting where functional gene silencing occurs. In particular, a significant fraction of internalized ONTs are nonproductively sequestered in endo-lysosomal compartments. Here, we describe a two-step, robust assay for high-throughput de novo detection of small bioactive molecules that enhance cellular uptake, endosomal escape, and efficacy of ONTs. Using this assay, we screened the LOPAC (Sigma-Aldrich) Library of Pharmacologically Active Compounds and discovered that Guanabenz acetate (Wytensin™), an FDA-approved drug formerly used as an antihypertensive agent, is capable of markedly increasing the cellular internalization and target mRNA silencing of hydrophobically modified siRNAs (hsiRNAs), yielding a ∼100-fold decrease in hsiRNA IC50 (from 132 nM to 2.4 nM). This is one of the first descriptions of a high-throughput small-molecule screen to identify novel chemistries that specifically enhance siRNA intracellular efficacy, and can be applied toward expansion of the chemical diversity of ONTs.
Insights
Researchers developed a new assay to find drugs that improve oligonucleotide therapeutic delivery. They discovered Guanabenz acetate enhances siRNA cellular uptake and gene silencing, significantly boosting therapeutic efficacy.
Area of Science:
- Oligonucleotide Therapeutics
- Drug Discovery and Development
- Molecular Biology
Background:
- Efficient delivery of oligonucleotide therapeutics (ONTs) to the intracellular environment is a major challenge for their pharmaceutical success.
- Internalized ONTs are often trapped in endo-lysosomal compartments, preventing functional gene silencing.
- There is a need for novel chemical entities to enhance the intracellular delivery and efficacy of ONTs.
Purpose of the Study:
- To develop a robust, high-throughput assay for identifying small molecules that enhance the cellular delivery and efficacy of ONTs.
- To screen a library of pharmacologically active compounds to discover novel enhancers of oligonucleotide therapeutic activity.
- To identify specific compounds that improve both cellular uptake and endosomal escape of ONTs.
Main Methods:
- A two-step, high-throughput assay was designed for the de novo detection of small bioactive molecules.
- The assay measures enhancement of cellular uptake, endosomal escape, and efficacy of oligonucleotide therapeutics.
- The LOPAC (Library of Pharmacologically Active Compounds) was screened using the developed assay.
Main Results:
- Guanabenz acetate (Wytensin™), an FDA-approved antihypertensive drug, was identified as a potent enhancer of oligonucleotide therapeutic activity.
- Guanabenz acetate significantly increased cellular internalization and target mRNA silencing of hydrophobically modified siRNAs (hsiRNAs).
- A ~100-fold decrease in hsiRNA IC50 was observed in the presence of Guanabenz acetate (from 132 nM to 2.4 nM).
Conclusions:
- This study presents one of the first high-throughput small-molecule screens for identifying novel chemistries that enhance siRNA intracellular efficacy.
- Guanabenz acetate demonstrates significant potential for improving the therapeutic performance of oligonucleotide-based gene silencing agents.
- The developed assay and identified compound can contribute to expanding the chemical diversity and therapeutic applications of oligonucleotide therapeutics.
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