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Breakthrough in siRNA Therapy Reduces Off-Target Effects

Small interfering RNA (siRNA) therapies represent a promising avenue for treating genetic disorders by silencing specific genes. Despite their potential, these therapies face a challenge: the tendency of siRNAs to inadvertently affect non-target genes, which can lead to unwanted side effects.

Researchers at Nagoya University in Japan have introduced a significant advancement in this field by employing formamide to chemically modify siRNA, thereby minimizing these off-target interactions. Their findings, which have been documented in Nucleic Acids Research, could improve the safety profile of these genetic therapies.

siRNAs are short, double-stranded RNA molecules that target messenger RNA (mRNA) to inhibit the production of disease-causing proteins. By disrupting the expression of harmful genes, siRNAs offer a therapeutic route for various genetic conditions. However, the occurrence of off-target effects, when siRNAs interact with unintended mRNA strands, often hampers their therapeutic efficacy. Such interactions can disrupt cellular functions and affect the immune system.

One critical factor contributing to off-target effects is a seven-nucleotide sequence known as the seed region in the siRNA guide strand, which is essential for recognizing the intended target. Unwanted pairings with complementary sequences in non-target mRNAs can lead to these unintended interactions.

Professor Hiroshi Abe, leading the research, noted, “The off-target effect likely occurs when non-target mRNAs exist that form base pairs with the seed region of siRNA,” reinforcing the idea that modifying this specific area could help mitigate such risks. By altering the base pairing ability of this seed region through chemical modifications, the team aimed to create a stable binding only when the siRNA fully interacts with the intended mRNA.

Through the introduction of formamide into the modification process, the research team successfully disrupted the hydrogen bonds crucial for mRNA stability. This chemical alteration destabilizes the mRNA double helix and makes it less likely for the siRNA seed region to bind to non-targeted mRNA strands.

“This modification achieved suppression of off-target effects with higher efficiency than existing chemical modifications,” commented Abe. The researchers found that making this adjustment at a single point within the siRNA sequence allows for greater flexibility in the design of therapeutic siRNA constructs.

The expectation is that these chemically modified siRNAs could be utilized as therapeutic agents with reduced side effects. According to Kohei Nomura, one of the researchers, the implications of this work are vast, potentially benefiting treatments for conditions like hereditary transthyretin amyloidosis, acute hepatic porphyria, primary hyperoxaluria type 1, primary hypercholesterolemia, and mixed dyslipidemia.

More information: Kohei Nomura et al, Synthesis of 2′-formamidonucleoside phosphoramidites for suppressing the seed-based off-target effects of siRNAs, Nucleic Acids Research (2024). DOI: 10.1093/nar/gkae741

This research signifies an important step forward for siRNA therapies, indicating that with careful chemical engineering, it may be possible to enhance the precision of genetic therapeutics while minimizing undesirable side effects.

Source
phys.org