SiRNAs with Neutral Phosphate Triester Hydrocarbon Tails Exhibit Carrier-Free Gene-Silencing Activity

Abstract

Short interfering RNAs (siRNAs) show promise as gene-silencing therapeutics, but their cellular uptake remains a challenge. We have recently shown the synthesis of siRNAs bearing a single neutral phenylethyl phosphotriester linkage within the sense strand. Here, we report the synthesis of siRNAs bearing three different hydrophobic phosphate triester linkages at key positions within the sense strand and assess their gene silencing in the absence of a transfection carrier. The best siRNAs bearing hydrophobic phosphate triester tails were not aromatic and exhibited effective gene silencing (IC50 ≈ 56–141 nM), whereas the aromatic derivative with three hydrophobic tails did not exhibit carrier-free gene silencing.

Synthesis of Dinucleotide Non‐Symmetrical Triester Phosphate Phosphoramidites and Their Incorporation Within Oligonucleotides

“…The synthesis of the four dinucleotide triester phosphate alcohols were adopted from previously published articles from our laboratories (Hammill et al., 2022; Tsubaki et al., 2019; Tsubaki et al., 2020). In general, these reactions proceed well and are high‐yielding in nature.…”

Advancing New Chemical Modalities into Clinical Studies

“…Similar to ASOs, standard chemical alterations include replacing the 2′-hydroxy in the ribose sugar (Figure ). Additional medicinal chemistry modifications are an active area of research . Since the siRNAs only need to be delivered outside the nucleus, in contrast to ASOs, other delivery approaches have been investigated, like lipid nanoparticles and GalNAc conjugates.…”

“…Additional medicinal chemistry modifications are an active area of research. 35 Since the siRNAs only need to be delivered outside the nucleus, in contrast to ASOs, other delivery approaches have been investigated, like lipid nanoparticles and GalNAc conjugates. We refer the readers to recent literature for further insights on those approaches.…”

Replacement of the phosphodiester backbone between canonical nucleosides with a dirhenium carbonyl “click” linker—a new class of luminescent organometallic dinucleoside phosphate mimics

“…[1][2][3] Furthermore, the discovery of novel chemically modified nucleosides and nucleotides has been beneficial for the development of RNA/DNA-targeting technologies such as antisense and short interfering RNA as well as the increasingly popular CRISPR-Cas9 gene editing technique. [4][5][6][7][8] Structural alterations of canonical nucleic acid components pertains to the modification of the nucleobase, the (deoxy)ribose and the phosphodiester backbone. 1,2,[9][10][11] In the case of the phosphodiester backbone, three general classes of modifications can be distinguished.…”